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02-13-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 161
Post ID: 9737
Reply to: 9736
That all is incorrect in a way….
fiogf49gjkf0d

KM,

Very good points. There is one more moment that I would like to pay attention. The new prediction tubes are more powerful then vintage tubes. They all claim 1 extra watt because “better materials were used”. So, I wonder, if it would be possible that in some cases Adrian’s old tube run out of power as Adrian did mention bass deficiency. Also, the new tubes might have less grid current and as soon the 2A3 runs out of negative grid voltage and grid current begin to rise then the old tube might need more powerful driver.

So, without a demeaning the results of Adrian’s finding I would propose that his observations are good as they are but if we would demand a definitive comparing then more methodologically kosher environment  shell be used. I would say that to be on a save site it need to be sure that both old and new tubes are used in the equal way. I think two measurements are necessary. First one, is to show how a given tube battles A2 class or how linear it is with positive voltage on grid. Let agree the for 3W tube it matters. Second, I would like to make sure that each tube individually set it the right operation point. I would like to drive a full power over the tube and to see that currant and voltage would clip at the same time. Ok, now it the interesting moment – what to do it they are not the same. To change operation point? To change loading? All of it affects Sound it and the question would be: what is the sound of tube vs. what the sound of the given operation?

I have to note that the Adrian’s comment about the saturation of colors most likely are the not the properties of operation but the properties of the tubes themselves. We do not know for how long but it is what it is. Still my general views on audio suggest me that comparing of tube is necessary to do only in context of the whole framework and in context of the specific intentions of reproduction. Let say for instance that Adrian has a park of all drivers out there and he reports that Silvania 2A3 with one specific driver sounds identically to the Emission Labs with another driver under identical clipping and A2 conditions. I think it would be a useful and indicative illustration. Unfortunately not one does it, .... and frankly speaking…. no one need it… the live is too short to waste it to those things…

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-13-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 162
Post ID: 9739
Reply to: 9736
NOS vs new 2A3 tubes
fiogf49gjkf0d
First of all, this not an attack on NOS tubes and it is all meant to be just sort of fun and educational. I happened to have all these 2A3 tubes side by side for comparison, so why not? I also have done the same thing with other tube types like 6SN7 but since nobody on this website uses 6SN7 in a circuit, I do not think it will be interesting to post it.
 floobydust wrote:
I can't fully respond to this as I don't have the new tube brands you have. I posted earlier regarding my personal findings with the EML 45 solid-plate versus NOS however. As a result I found the (known good) NOS 45 to provide a more neutral and accurate sound.
Anyway, no response necessary. I am just doing this for fun. Keep in mind also that the NOS Sylvania tubes are very good and to my ears better than many of the new manufactured tubes from Russia, China, etc.

 floobydust wrote:
I also have to question if many of the new manufactured tubes with old tube types even qualify as being a "true replacement." Not to mean it's not a good tube, but to point out that is not a true version of the original.

Well, yes, does it really matter, so long as it achieves the goal in the circuit if it is a "true 2A3." I don't see it as a Formula 1 race. However, I get the point, which goes along with my feeling that the Kron tubes and the two mesh plate tubes are sort of revolutionary with distinctly different sound, not characteristic of the limitations of the standard 2A3 tubes. An example: the side mirror was created in racing when a rear view mirror view was obscured by the engine/frame. The car was disqualified that year anyway, but side mirrors are now standard. We should not reject or exclude improvements to design.

 floobydust wrote:
Some of your comments do cause me to wonder about some things... mainly the conditions of your tests. It's unclear (at least to me) what amplifier you are using as a test subject and what are the specifics regarding it.

It is the Moondog 2A3 circuit, basically which can be seen at http://home.earthlink.net/~ivol/audio/moondog.htm.

 floobydust wrote:
Perhaps the NOS 2A3 was no longer running in an optimal setup. In my humble view, if you don't verify proper operation of each set of tubes, then the overall test is somewhat suspect.
Sure, but on the other hand I would say it is a fair test in that all tubes were run under identical conditions.

 floobydust wrote:
Based on my experience with the EML 45, I would not be inclined to purchase a pair of their 2A3 tubes... but the Kron tube seems intriguing and I may look into their 2A3.
The mesh plate tubes are quite different; do not discount them.

 Romy the Cat wrote:
So, I wonder, if it would be possible that in some cases Adrian’s old tube run out of power as Adrian did mention bass deficiency. Also, the new tubes might have less grid current and as soon the 2A3 runs out of negative grid voltage and grid current begin to rise then the old tube might need more powerful driver.

So, without a demeaning the results of Adrian’s finding I would propose that his observations are good as they are but if we would demand a definitive comparing then more methodologically kosher environment shell be used. I would say that to be on a save site it need to be sure that both old and new tubes are used in the equal way. I think two measurements are necessary. First one, is to show how a given tube battles A2 class or how linear it is with positive voltage on grid. Let agree the for 3W tube it matters. Second, I would like to make sure that each tube individually set it the right operation point. I would like to drive a full power over the tube and to see that currant and voltage would clip at the same time. Ok, now it the interesting moment – what to do it they are not the same. To change operation point? To change loading? All of it affects Sound it and the question would be: what is the sound of tube vs. what the sound of the given operation?
Again, it is just a my own test in my own circuit with a few listeners. I would say that my impressions of other types of tubes generally coincide with the many stated on various forums, so I do not think my set-up is abnormal in any way; it is a real-life application for 2A3 tubes and I expect any 2A3 I buy to function in it.

I again just mention that the Sylvania 2A3 has a "kind of neutral sound" - not audio neutrality for the Sound as has been discussed here before, but more regular audiophile neutrality, with middle of the road balance and omission of errors. It is not a bad tube, actually a very nice traditional 2A3.

Adrian

02-13-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 163
Post ID: 9741
Reply to: 9739
The identical operation environment?
fiogf49gjkf0d

 drdna wrote:
First of all, this not an attack on NOS tubes …

A very strange introduction. Since when people post at this site feel a need to ask apologies for attack or not attack anything? Also, where this phase “attack” ever came from?  Adrian I can assure you that people who find useful for them to visit this site, not to say post here, have no personal spiritual investment into any agenda. So, would you attack the NOS tubes or not attack them it recognize as nothing else them your assessment of NOS tubes. If people feel that you “attack” the NOS tubes then the people are idiots and who care what they feel. I do not know many idiots in audio who feel that expressing a justified criticism is a personal attack. I have seen intense cases when people go to extremes, whoring own wife and losing all dignity and respect to truthfulness/really just because somebody express a skepticism toward to their sound (like that dirt from the PA’s Mill). I true hope that those attitude are not reveling in this site and there is no need to remind  that your objectives are not “to attack”.

 drdna wrote:
  Again, it is just a my own test in my own circuit with a few listeners. I would say that my impressions of other types of tubes generally coincide with the many stated on various forums, so I do not think my set-up is abnormal in any way; it is a real-life application for 2A3 tubes and I expect any 2A3 I buy to function in it.

Well, it is not a conversation about your set-up “being abnormal in any way” but about evolution methods. It you replace your 6SN7 with other vintage then it would be not a big deal and the result will be demonstrate the difference in the tube. Even if you run twice more current over your driver tube it will not affect sound a lot. The output tube and partially in no feedback amp is a different story. Some NOS and the new tubes are so different then need to be used differently in order to have own best respectful applications. I just say the it is very difficult subject and juts puling the tubes in and out is NOT always send the very different tubes in identical operation environment.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-13-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 164
Post ID: 9742
Reply to: 9741
Preferred 2A3 operating point
fiogf49gjkf0d
 Adrian, Romy, et al,

 Okay, I don't take any of it as an attack... so none of that bothers me.... I'm fine with it... again, it's a view on what you heard based on your test scenario, nothing more and I certainly welcome the review. Now that I understand it... here's some of my (personal) viewpoints on this.

 The Moondog design goes back a good 10 years now, is a straight-forward design and there's basically nothing wrong with it. If you do some modeling you're running about 15.5 watts of dissipation on the plate and pushing over 4.5 watts output. Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in higher distortion than the text-book operating point, which is B+ of 300 volts and a 750 ohm cathode biasing resistor and the 2.5K load.

 From my findings with the (NOS) 2A3 and higher voltages, going to a higher plate load impedance makes a large difference by lowering distortion. My basic 2A3 SET design uses a 3.5K load with a 866 ohm cathode bias resistor and a 350 volt B+ supply. This was far more optimal and provided much better (clean) low-frequency response and a noted reduction in measured distortion and better wave-form symmetry. I also tested with a 2.5K load and a 1K cathode bias resistor.... so at least with NOS 2A3 tubes, performance suffered.

 I have a "gut feel" that the new manufacture 2A3 versions may perform better than the collection of NOS tubes I used for validating my design (literally over 50 of different brands) at the operating points of the Moondog. Again, a gut feel... nothing more. One last point to consider.... I've not seen any specifications for new tubes which state what the interelectrode capacitance values are. As pretty much all of the new tubes are NOT the same materials and/or internal construction, it's unlikely they are the same in these measurements. This could result in an audible difference based on the driver circuit and available slew rate and current flow. If I were to obtain a pair of KR 2A3 tubes (I'm thinking about them... but they are very pricey!) I would certainly go back and optimize the operating points for them. I had to do this for the EML 45 tube and it paid off in better performance (ad more power).

 Regards, KM




... just because you're paranoid, it doesn't mean they're not after you ...
02-13-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 165
Post ID: 9743
Reply to: 9742
The sound of the 2A3 however?
fiogf49gjkf0d
 floobydust wrote:
Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in higher distortion than the text-book operating point, which is B+ of 300 volts and a 750 ohm cathode biasing resistor and the 2.5K load. From my findings with the (NOS) 2A3 and higher voltages, going to a higher plate load impedance makes a large difference by lowering distortion. My basic 2A3 SET design uses a 3.5K load with a 866 ohm cathode bias resistor and a 350 volt B+ supply. This was far more optimal and provided much better (clean) low-frequency response and a noted reduction in measured distortion and better wave-form symmetry. I also tested with a 2.5K load and a 1K cathode bias resistor.... so at least with NOS 2A3 tubes, performance suffered.
Perfectly reasonable, however I would be very interested to know the way in which the sound changed with the adjustments, beyond oscilloscope measurements with the different ways you tried it. This would be useful information to me.

Also what is interesting is that the general observations I have had are similar to those of others who have used these tubes in different circuits. That is the sonic differences remain consistent. So I wonder how profound would be the sonic impact of the optimization of the circuit you speak of. No doubt a tube must be operated correctly to do its best, but the question to me is how big is the reward and in what respect it affects the sound.

Adrian
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 166
Post ID: 9747
Reply to: 9742
Circuit modification for 2A3 optimization
fiogf49gjkf0d
 floobydust wrote:
If you do some modeling you're running about 15.5 watts of dissipation on the plate and pushing over 4.5 watts output. Running the higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load results in higher distortion than the text-book operating point, which is B+ of 300 volts and a 750 ohm cathode biasing resistor and the 2.5K load. From my findings with the (NOS) 2A3 and higher voltages, going to a higher plate load impedance makes a large difference by lowering distortion. My basic 2A3 SET design uses a 3.5K load with a 866 ohm cathode bias resistor and a 350 volt B+ supply. This was far more optimal and provided much better (clean) low-frequency response and a noted reduction in measured distortion and better wave-form symmetry.
Okay, so do you have some specific suggestions for modification of the exisiting circuit? I am willing to do it and then repeat my comparison tests to see what result the changes will give.

 floobydust wrote:
I have a "gut feel" that the new manufacture 2A3 versions may perform better than the collection of NOS tubes I used for validating my design (literally over 50 of different brands) at the operating points of the Moondog.
I would agree. I usually think the NOS tubes are better also. However, the improved design 2A3 are actaully an improvement to my ears. Too bad about the price.

Adrian
02-14-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 167
Post ID: 9748
Reply to: 9747
How to get max power from 2A3
fiogf49gjkf0d
I do not remember details already but Dima and I had the same discussion a few weeks back. After all his research he was very much disagree with textbook use of 2A3. He felt that max power and the most proper operation of this tube will be at 275V on plate and 4.1K load. He had a very elegant theory of “a proper entrance in voltage starvation mode”, might be he will be posting it… He constantly was taking about 4.5W with under 15W on plate. I did not test this mode but what Dima proposed sounded much rational to me then the classic 250V and 2.5K load.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-14-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 168
Post ID: 9749
Reply to: 9748
2A3 voltages, loads and realized output power
fiogf49gjkf0d
 Adrian, Romy, (Dima),

 First, I most certainly agree that the textbook operating point for the 2A3 is not optimal and can be improved on, hence my own design from a few years ago. If you are sticking with a 2.5K load, you will simply not get the most from the 2A3, distortion will be higher and waveform symmetry will suffer. This is validated by hundreds of hours of research/testing which included calculated load lines, software simulations and most importantly, bench time with over 50 different NOS 2A3 tubes using different load impedances, plate voltages and bias currents. Measurements were done using a Fluke digital meter (for DC voltage measurements), Tek 2215A dual-trace scopes, HP 400FL True RMS meters and a 334A Distortion analyzer with a clean sine/square oscillator.

 From all of my research on this tube, I feel quite comfortable stating that 3.5K is the optimum load. Going lower increases distortion and going higher results in a loss of power with no tangible benefit. At 275 volts and a 4.1K load (15-watt Pd) you'll be lucky to get much more than 3-watts. You simply don't have the voltage to swing. I prefer ~290 volts on the plate (plate to cathode measurement). I also run the plate dissipation up a bit higher to 17-watts. Note: I don't see this as any sort of risk provided you have adequate ventilation around the tube. What is critical is NOT to exceed the rated cathode current of 60ma, as this will decrease the usable lifespan of the tube.

 In my existing (implemented) design, I have a 350-volt plate supply, a 3.5K primary OPT, and an 866 ohm cathode bias resistor (bypassed). Pd is 17-watts, cathode bias current is 58ma and it puts out a solid 4.5-watts with good NOS tubes before any clipping occurs, and the clipping is symmetrical. The performance is also very consistent with the majority of the 2A3 tubes I have. There are of course some NOS tubes which are not so good... I even have two with grid leak problems despite using a 249K grid resistor.

 Still, I'd be very interested to hear what Dima finds in his testing.... and of course which tubes he winds up using for his tests.

 Regards, KM



... just because you're paranoid, it doesn't mean they're not after you ...
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 169
Post ID: 9750
Reply to: 9749
Optimal operation of 2A3: an experiment
fiogf49gjkf0d
 floobydust wrote:
[The Moondog amplifier has] a higher B+ voltage (350 volts) with a 1K cathode bias resistor and the 2.5K load.


 Romy the Cat wrote:
...the most proper operation of this tube will be at 275V on plate and 4.1K load.


 floobydust wrote:
3.5K is the optimum load. I prefer ~290 volts on the plate (plate to cathode measurement). I have a 350-volt plate supply, a 3.5K primary OPT, and an 866 ohm cathode bias resistor (bypassed). Pd is 17-watts, cathode bias current is 58ma and it puts out a solid 4.5-watts.


So it would require a new OPT to be made with around 3.5-4K primary impedance. The power the amplifier puts out is already far too much. I always have the volume dial around 1-2, so this will be okay. I don't have such an OPT on hand so I will need to buy one...

Will that be an adequate test or would you suggest changing the values of R9 and R10 also?

Adrian


02-14-2009 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,570
Joined on 10-12-2006

Post #: 170
Post ID: 9751
Reply to: 9749
Tubes, Whole Circuits, Expectations and Sound
fiogf49gjkf0d
It sounds like a lot of the circling has to do with which 2A3 "sounds better", outright.  In any case, I'm guessing everyone would agree that it is specious to argue about which 2A3 sounds most like some internally-established aesthetic benchmark for 2A3s.  I certainly hope no one cares about that.  The idea is to get the "Best Sound", period; right?

The fact is that "new 2A3s" are often thinly-disguised 300Bs, and they can easily up the ante with respect to power, which often gets short shrift from flea-power afficionados.  Well, if it's power one wants from a 2A3, then why not start out with a clean-sheet design based on one of the new breed of "2A3s"?  

As it happens, I prefer the best part of the "neutral" sound "character" of old, tres-expensive 45s to anything else I've gotten to listen to long enough to establish a sense of its contribution to the sound.  Yet, I have never actually owned a 45.  The reasons for this are purely practical; basically, it lacks the range and power to drive acceptable speakers well enough to play Music to my satisfaction.  The 45 sounds great; but it can't make great Wagner.  And as I progressed with the more-powerful 2A3, I wound up with the same problem, even with A-2 via the very-hearty older Sovteks (which the circuit was built around, BTW).  I can only guess whether others have FR speakers that are somehow efficient enough to overcome the problems I encountered; but I have my suspicions...

With respect to circuit design, one of the most facinating things I have learned about electronics for hi-fi is that any theoretical solution to a given problem requires an all-inclusive, 4-D, total-system perspective; and still one is apt to wind up scratching one's head at results.  From Miller Effect to ESR, on and on, real world circuits are "dynamic" in every sense, and they are in every sense woirthy adversaries, to say the least.  For instance, although I have no idea where the actual power goes, I have begun to see a pattern of diminishing net returns with respect to the smaller SETs, to the point where I wonder if their "potential" can ever be practically realized as Music in Full Glory.

Regarding 2A3 selection, my impression here is that we all +/- understand the in's and out's of operating points; but we all have different systems and it sounds like we also have different expectations at this time.

Lastly, the choice of an output tube for MF-only DSET for a single 109 dB horn-loaded compression driver casts an entirely different light on the subject, I think.  If there is a real possibility, then this might be close to a case where one need only look at the straightest part of the plate curve of a 2A3 (or 45) and build to that, irrespective of "power".  I have had some luck adapting phono stages this way; but so far, no keepers from amongst the small SETs I've played with.

Paul S
02-14-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 171
Post ID: 9752
Reply to: 9750
Gain is not power.
fiogf49gjkf0d
 drdna wrote:
So it would require a new OPT to be made with around 3.5-4K primary impedance. The power the amplifier puts out is already far too much. I always have the volume dial around 1-2, so this will be okay. I don't have such an OPT on hand so I will need to buy one...
Adrian, what you report that your amp “puts out already far too much” is gain not power. You have two driver stages each of them 20 times gain, so you have too much gain, not power. BTW, if I were you I would get rid one stage as it is absolutely not necessary in this design. I do not like high-gain 2A3 –who heed high gain if it is not supported by sufficient power? I did have 2 stages, one stage, one parallel 2A3 and one 6E5P (which is 30 times gain with one stage). I do not like too much gain for given power as it driver the power tube deeper to A2 – way would we want it? BTW, when you go from the “standard” 2.5K load to 4.2K you will lose some gain.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 172
Post ID: 9753
Reply to: 9749
2A3 amplifier modification & Optimization
fiogf49gjkf0d
KM:

It will be a little project to modify the amplifier, but it may be educational. To optimize the Moondog circuit for the NOS 2A3 tubes, so they will give their best, I plan to buy a new OPT with primary impedance around 3.5-4K. Will that be sufficient or would you chnage the values at R9, R10, or what would you do to consider it a optimum test?

Adrian
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 173
Post ID: 9754
Reply to: 9751
Specialized DSET approach
fiogf49gjkf0d
 Paul S wrote:
I have begun to see a pattern of diminishing net returns with respect to the smaller SETs, to the point where I wonder if their "potential" can ever be practically realized as Music in Full Glory. Lastly, the choice of an output tube for MF-only DSET for a single 109 dB horn-loaded compression driver casts an entirely different light on the subject.
How about using the 6C33C for the low midrange-woofer, the 2A3 for the upper midrange, and the 45 for the tweeter? I suspect if each circuit can be optimized, that they can do their best within each frequency range.
Adrian
02-14-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 174
Post ID: 9755
Reply to: 9754
6C33/2A3 DSET?
fiogf49gjkf0d
 drdna wrote:
How about using the 6C33C for the low midrange-woofer, the 2A3 for the upper midrange, and the 45 for the tweeter? I suspect if each circuit can be optimized, that they can do their best within each frequency range.
Hm…. I do not think that it makes sense in your particular playback. You use Edgar’s refrigerator subs that use own LF SS amps (that use EQ of I am not mistaken), so you do not use the full advantage of SET LF sound. To construct 6C33C DSET juts for sake of upperbass driver doss not sound reasonable to me. Now, if you intend to drive you subs and upperbass from 6C33 then it is while another story. Then you might have 2-way DSET with let say 500-600Hz break and it might be an interesting solution. The key would be to found out what kind loading the refrigerator subs would demand and if the 6C33 will have enough power to drive the LF. It would be also nice if the upperbass would be OK with the same loading as bass would demand. Then you can go line level-crossover for MF (big advantage) and do not case about the power from your 2A3. Theoretically it possible to make a situation when the 6C33 and 2A3 would be driver from the same PS but it would be too difficult…

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-14-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 175
Post ID: 9756
Reply to: 9752
SET usable power and making the most of it
fiogf49gjkf0d
 Well... tis for all reading/following this thread.

 As Romy pointed out, having high gain is not the same as power. And as Adrian hinted at... the overall system paradigm is important. If you're only barely cracking the volume control on your amplifier or preamplifier then it should be obvious that you have more gain than you need. Personally I don't put volume controls on power amplifiers... I prefer ONE point of control, not multiple... but to each his/her own.

 If you're designing and building your own equipment then managing the system as a whole becomes less of an issue. If you're picking piece parts (either built, kit or implementing somebody else's design) then you need to manage the various gain of each component and determine how to best integrate them into a system. As far as the gain in the amplifier goes, it's a moot point IF you manage the overall system gain properly. I've done two SET designs over the past few years... and they are quite different on gain, yet have very similar specifications. There are both technical and financial reasons for each design but both have been optimized for performance, not gain. Also, both take into account the OPT winding/phase and result in a non-inverting design.

 A brief word on power.... the 45 triode in a proper design will deliver a solid 2- to 2.5-watts and can be flat from 20Hz to 50KHz (or more) depending on the design, components and how it's actually built. A 2A3 triode will deliver up to 4.5 watts in the same application... please note that this is ONLY a 3dB change (double the power). As such, it's not really surprising that you (Adrian) realized little benefit from the 2A3 over the 45... you didn't gain very much (power). Having speakers which have higher sensitivity is a real requirement for using low power amplifiers. And even then, the last 1 to 2 octaves will require some additional help for anything beyond moderate listening levels. There's no free lunch to acheiving SPL levels.... it's a match between the sensitivity of the speakers and the available output power, i.e., no magic involved.

 If you plan on using 2- to 5-watt SET amplifiers, you need to mate them with speakers of adequate sensitivity AND which will mate well with a low powered SET, of which most (if not all) have no negative feedback and have low damping factor. This places a much greater demand on the type of speaker that will perform well with the amplifier. Personally, I find the sonic neutrality and open soundstage of a properly designed SET to be the dominant factor that makes me want to use one. The (technical) reasons are beyond the scope of this post however. The down side is two-fold: 1- The electrical and mechanical parameters of the speaker (impedance curve, self damping, moving mass, etc.) can wreak havoc with any SET design. 2- Low frequency performance will be limited regardless... as you walk down the scale of organ pipes you simply need more power and larger drivers to deliver those low pedal notes. Getting the last couple of octaves will require additional support and you're not going to manage it with low powered SETs.

 As for modifying your Moondog amplifiers, I would recommend against it. While you can effectively reduce the overall distortion and gain a bit of additional power, it's not worth gutting the amplifier and start swapping out expensive parts. If you're not happy with the amount of power now, NO change will fix it as you simply can't gain enough power to deliver Wagner.... also what speakers are you driving with the MDs? You would likely be better off with a different (SET) amplifier which has enough power to meet your needs.

 Regards, KM



... just because you're paranoid, it doesn't mean they're not after you ...
02-14-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 176
Post ID: 9757
Reply to: 9753
The 2A3 loading
fiogf49gjkf0d
 drdna wrote:
It will be a little project to modify the amplifier, but it may be educational. To optimize the Moondog circuit for the NOS 2A3 tubes, so they will give their best, I plan to buy a new OPT with primary impedance around 3.5-4K.
Sure you might do it but if you are comparable with your transformer then it might be no need to order another OPT with higher primary. If you have multiple taps on secondary, which is most likely you have on a commercial amp then you can drive your 16R driver from 4R or 8R taps – you will have the same effect of unloading the 2A3’s plate. You might also to use some secondaryies sections (if you have access to them) as primaries…

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 177
Post ID: 9760
Reply to: 9755
DSET solution for EdgarHorn?
fiogf49gjkf0d
 Romy the Cat wrote:
You use Edgar’s refrigerator subs that use own LF SS amps (that use EQ of I am not mistaken), so you do not use the full advantage of SET LF sound.
You are correct, though I believe the subwoofer covers only below 40 hz.

 Romy the Cat wrote:
To construct 6C33C DSET juts for sake of upperbass driver doss not sound reasonable to me.
This is coming from the same person who has built a 6-channel DSET?

Anyway, it was more a thought about optimizing the operation of each of these tubes and matching them to the drivers they would work.

Adrian
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 178
Post ID: 9761
Reply to: 9756
Optimizing the 2A3
fiogf49gjkf0d
 floobydust wrote:
As Romy pointed out, having high gain is not the same as power. If you're only barely cracking the volume control on your amplifier or preamplifier then it should be obvious that you have more gain than you need. If you're picking piece parts (either built, kit or implementing somebody else's design) then you need to manage the various gain of each component and determine how to best integrate them into a system. As far as the gain in the amplifier goes, it's a moot point IF you manage the overall system gain properly. I've done two SET designs over the past few years... and they are quite different on gain, yet have very similar specifications. There are both technical and financial reasons for each design but both have been optimized for performance, not gain. A brief word on power.... the 45 triode in a proper design will deliver a solid 2- to 2.5-watts and can be flat from 20Hz to 50KHz (or more) depending on the design, components and how it's actually built. A 2A3 triode will deliver up to 4.5 watts in the same application... please note that this is ONLY a 3dB change (double the power). As such, it's not really surprising that you (Adrian) realized little benefit from the 2A3 over the 45... you didn't gain very much (power). Having speakers which have higher sensitivity is a real requirement for using low power amplifiers. And even then, the last 1 to 2 octaves will require some additional help for anything beyond moderate listening levels. If you plan on using 2- to 5-watt SET amplifiers, you need to mate them with speakers of adequate sensitivity AND which will mate well with a low powered SET, of which most (if not all) have no negative feedback and have low damping factor. As for modifying your Moondog amplifiers, I would recommend against it. While you can effectively reduce the overall distortion and gain a bit of additional power, it's not worth gutting the amplifier and start swapping out expensive parts. If you're not happy with the amount of power now. You would likely be better off with a different (SET) amplifier which has enough power to meet your needs.

I think you may have misunderstood my post. I am not looking for more power or gain at all.

Really the idea of modifying the circuit came about as a thought to try and get the most out of the Sylvania tube and see if I am missing something in my assessment.

There is absolutely no need for more gain or power, as far as I know. The speakers are the EdgarHorn Titan horn loudspeakers, which I think have about 107 db sensitivity. As I said I keep the preamplifier on around 1-2 and it is passive! It would be very easy to sacrifice gain for an improvement in the sound quality, which is after all, as Paul said, the goal of it all.

My goal in audio is to achieve a connection to the Sound, or the living presence of the musicians and composers, the insight into the piece/performance that makes you reflect and ponder, the emotional connection that makes you want to listen, that makes you connect in such a way that you feel you are hearing the real live breathing musicians, not only that they are in the room but beyond that to the soul of the music of what they thought and felt, etc.

So it is a bit idiosyncratic for me, as minimizing distortion and getting a good frequency response are good, but not really my goal. An example: both the Sylvania and the Sophia mesh plate tubes have some limitation in the very low end and do not do the high frequencies exactly correctly; both also have tiny but noticeable amounts of distortion. However, I really love the Sophia tube quite a bit. It has a wonderfully rich, open, concupiscent midrange that I found especially involving on many classical pieces like Bruch's Scottish Fantasy. By comparison, the Sylvania has a midrange presentation that is audiophile neutral. It has an additional level of tangibility and dynamic ease that I have not found with the NOS tubes.

So my thought was: maybe I am missing out. Maybe I should try to optimize my circuit.

Anyway, I would love to hear about your sonic impressions also of the 2A3 tubes, as you have extensive experience with over 50 types. That is a treasure trove of information, and I would love to learn about your impressions.

Adrian
02-14-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,049
Joined on 05-28-2004

Post #: 179
Post ID: 9762
Reply to: 9760
How much to DSET a DSET
fiogf49gjkf0d
 drdna wrote:
You are correct, though I believe the subwoofer covers only below 40 hz.
So???
 drdna wrote:
This is coming from the same person who has built a 6-channel DSET? Anyway, it was more a thought about optimizing the operation of each of these tubes and matching them to the drivers they would work.
And because I have built a 6-channel DSET and have experience of its proper application I do feel comfortable to talk about optimization of DSET ideas from a perspective of cost-benefits analyses. If you would like to build a dedicated DSET with 6C33C juts to drive one upperbass channel then feel free to do so. I do not see you framed a need for it but it is my way to look at the things. When you were talking about “optimizing the operation of each of these tubes and matching them to the drivers” did you mean to have one powerful driver and drive with it both 2A3 and 6C33C with DSET transformers? We use to play with this idea…


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-14-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 180
Post ID: 9763
Reply to: 9762
DSET for Titan
fiogf49gjkf0d
 Romy the Cat wrote:
 drdna wrote:
You are correct, though I believe the subwoofer covers only below 35 hz.
So???
So, my thought was that below 35 hz, there are many ways of thinking about amplification. Some might say SS amplification is helpful due to power demands of horn loaded 18" woofers. To use 6C33 might be a trade off but I do not know if overall it would be a benefit. From your experience, what is your thinking?

It is a good idea to use the 6C33 for the woofer and subwoofer, but I worry that it would compromise the LF sound due to the demands of the subwoofer.
 Romy the Cat wrote:
Did you mean to have one powerful driver and drive with it both 2A3 and 6C33C with DSET transformers? We use to play with this idea…
That is an interesting idea, but I have no idea how such a circuit topology would sound.

I can best frame the limitations of the Titans matched to the rest of the system as some lack of dynamic stability and issues with the HF and midrange not being exactly correct.

I think it will be instructive to play with the Power conditioner and the DEQ. Unfortunately work is too busy right now for me to invest a lot of time in the project, which I would feel that it would require to do properly.

Adrian


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