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  »  New  6C33C myths: audio Moronometr...  Overdrive warning light...  Melquiades Amplifier  Forum     3  38792  06-22-2005
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  »  New  A full-range quality-triode? Does Size mater?..  A full-range quality-triode? Does Size mater?...  Melquiades Amplifier  Forum     0  10917  12-02-2009
03-09-2006 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 1
Post ID: 2182
Reply to: 2182
GM70 vs. 6C33C

I keep receiving emails from visitors asking me about my views regarding the GM70 vs. 6C33C. I am clearly not in a position to provide any EXPERT opinion because of two reasons. First, I never had a properly built GM70 in my disposal. Second, I hate DIY people, along with their BS interests…

From time to time the GM70 idea comes to me but there is always something the turns me off. The most important is power. People who read my site know that I do not believe in SETs but rather in the DSETs. To have 30W-40W is good but what for?

To use high voltage, 150kg pound monster-amp and to use it with a 20dB voltage divider is probably not a good idea. If a person is stupid enough to use low sensitively speakers that would need those 30W-40W then the person is juts stupid and a “better” amp will not help him…. The only thing that left are usually lower sensitivity LF sections of DSET but still… Mass, heat, cost, high plate impedance, huge transformer for LF section and it is only 40W. Not a lot of reimbursement for the efforts.

Sound? I do not know. I heard 4-5 amps around the GM70 and all of them were crap. I do not think that it was problem with GM70 but rather the amps were not serious.  There are some interesting private, “no holds barriers” implementation around GM70 about wish I have heard but I personally did not hear those amplifiers and the most important those installations.

6C33C is cheap, flexible, easy implementable, very good sounding with fix bias and a proper driver, low voltage and low plate impedance. I find the 6C33C is a quite nice nice for ~9W-12W SET.

Is 6C33C better then GM70? I do not know. I defiantly know that to implement the GM70 and 6C33C at the same level of max performance for each tube would requite very different level of affords. Would the result be justifiable? I do not know. I hope to learn about it sometimes.

Still, following my unavoidable rule:

http://www.goodsoundclub.com/TreeItem.aspx?PostID=432

I would like to be able to identify what the 6C33C or the GM70 does wrong before to consider anything else, though I know that I usually do not like sound of the “large” high voltage tubes: they work “somehow OK” only with the initially dead speakers.

I personally do not look at the GM70 direction but would be happy to audition somebody else’s efforts. The only tube that I might be trying in Melquiades would be YO186 for MF DSET but my motivations are very-very low and so far what 6C33C does perfectly satisfys me. If you have any “special” experience with GM70 (not with 211/845) then let me know.

Rgs,
Romy 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
03-14-2006 Post does not mapped to Knowledge Tree
Genn
Moscow
Posts 16
Joined on 06-28-2005

Post #: 2
Post ID: 2195
Reply to: 2182
GM70 and other Soviet valves
About a year ago I've take an interview of V.Lamm, and he mentioned his plans to release  GM70-based amp.  May be it is already on the market. 

Roman, could you descride your own observations regarding the Sound of Soviet tubes.  I have read a lot about the excelent sound of  various western brands.  But there is a thought, that such tubes do hide initial Musical Idea from the listener - they are not transparent in terms of sense.  Could you, please, share your observations on this subject?
03-14-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 3
Post ID: 2196
Reply to: 2195
Soviet tubes suck.

Lamm has been talking about his GM70-based amp for many years, buttering the subscribing to his speeches public. I do not know what the status in there but I would not expect anything relatively interesting. There are many objective reasons why I do not. Lamm latterly switch his products orientation and target market to hi-fi mass-market and currently his company unfortunately does not offer sound that it use to. In addition, some mental and psychological aberrations that Lamm obtained since bought into his industry statues, from my perspective, made him impotent to produces any more or less interesting results.

The Soviet tubes? I do not like them. Most of them snickly vulgar, dirty-colored, have no delicacy and no diminutive discrimination, too brutal, very unreliable, have a huge deviation from specification. Russian tubes Sound is like to massage a human body wearing gloves. Each single time when western equivalents was available the Soviet tubes were in deep lost. Not to mention the practically any Soviet tube, very similar to the majority of of Soviet commercial products, are juts the direct copy-cats of the western model.  I know some people who spread propaganda about the superior Sound of Russian tube but if to look deeply then behind their  views there are or mercantile interest, or plane ignorance or, primitive reference points or juts the typical Russian stupidly-imperial nationalism.

I do not have any observations “ in terms of sense”. I do not think that tubes, any of them have their intrinsic sound. All those tubes wee made “as is” and no one cared how them might sound. The GM70 was made to broadcast the Soviet railways regulation signal and not one ever thought that it might be ever used for any serious sound reproduction. In fact I do not think that anyone even made any tubes consciously and deliberately “for sound”. First of all because no one know or knew how to do it. We juts take the selected by different criteria tubes as they are and try to accommodate them for our purposes.

Why the Soviet tubes sound bad? I do not know and I do not think that they NECESSARY sound bad. They sound bad in comparing to their Western equivalents. However Russians made some their own tubes that were not stolen from West or stolen so poorly that it leaded to the creation of own “off the wall” tubes. Those tubes migh “sound OK” but only God knows how they would sound if West would produce the tubes with the identical characteristics.  It would defiantly would be fun to have for those $7 per tube the  Tungsram, Mazda, Mullard, Raytheon or Sylvania made 6C33C… I am sure if the do them then they would be much more interesting then the Soviet 6C33C

Rgs,
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
03-15-2006 Post does not mapped to Knowledge Tree
Genn
Moscow
Posts 16
Joined on 06-28-2005

Post #: 4
Post ID: 2197
Reply to: 2196
Re: Soviet tubes ...
Roman, thank you for your thoughts. 
However - you decided to use 6E5Pi to drive 6C33C, and the filed of competition in this case might be higher - including those E810F,  E180F, EL84..  or even 12AT7, or even (probably) WE 437.  Some of them would need higher input, but that is not a problem with pream. Were there any sonic reasons to choose 6E5P?  Or it is just a good engineering fit?
03-15-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 5
Post ID: 2198
Reply to: 2197
Re: Soviet bad, bad, bad tubes ...

 Genn wrote:
However - you decided to use 6E5Pi to drive 6C33C, and the filed of competition in this case might be higher - including those E810F,  E180F, EL84..  or even 12AT7, or even (probably) WE 437.  Some of them would need higher input, but that is not a problem with pream. Were there any sonic reasons to choose 6E5P?  Or it is just a good engineering fit?
I dod not. The 6E5Pi is not good tube, too thin. My interest for 6E5P/6P [to drive 6C33C] was not because my recognition of it’s advantages over other drivers (BTW, none of those that you mentioned are not good tubes for my application) but rather because my specific interest to the 6E5P/6P. If any know to me western tubes would do the certain things that 6E5P/6P does then I would be gladly useing the western equivalents.

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
06-05-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 6
Post ID: 2485
Reply to: 2182
The “elephant sound” from 211, 845, GM70...

I always was “concerned” about those large high voltage triodes: 211, 845, GM70….  They kind of different… The 845 always was brutal and not elegant, 210 was elegant but not sophisticated, and the GM70 was sophisticated enough but no one build any serious performing systems with this tube.

Still, all those large over 1000V tubes share the same quality that I head in all of them. Despite of their obvious intrinsic and implementation differences they all share something that I call “elephant sound”.

A couple days ago I heard a 845-based PP, driven by 300B. Even if to forget any randomness of that installation I still had a constant feeling when I was listening that I was geting the “elephant sound” – the sound that develops it’s own pressure without reference to it’s dimensions . To me those amps sound alike an elephant that stays in my leaving room. Suddenly the elephant would like to call me from kitchen and he makes his crazzy scream to attract my attention.  This scream is completely without any proportion to the distance, intentions, result and volume. It is juts a very rough loud and big sound, completely unnecessary in the given context. All 211, 845, GM70 that I heard did it: they created initially large sound and than minimize it's side depends of the input signal. People kind of like it, I do not.

The 6C33C does opposite: it crate a small sizes with small signal and then increase the “size of the elephant in the room" along with it's necessity. The 6C33C do not reaches the “size” of the 211, 845, GM7 but when we are talking about the 211, 845, GM70 size do we talk an it’s side or we talk about a pressure as an evidence of the size? What would describes the elephant on a room: it’s smell, it’s size, or…. the pressure with which the elephant’s ass press a listener to a wall?

To me the sound of 211, 845, GM70 in some ways remind me the sound of Martin Logan Statement.



If heard that monster 3 times and if you have experience with “that” sound then you know what I mean. Defiantly the Martin Logan Statement is too horrible to make this association but in any association there is a reason….

Rgs,
Romy 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
06-06-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 7
Post ID: 2488
Reply to: 2485
How the “elephant sound” made “useful”

 Romy the Cat wrote:
I always was “concerned” about those large high voltage triodes: 211, 845, GM70….  They kind of different… The 845 always was brutal and not elegant, 210 was elegant but not sophisticated, and the GM70 was sophisticated enough but no one build any serious performing systems with this tube.

Yesterday someone pointed out for me an interesting part that is begged to be use for some kind of 211, 845, GM70 project. It is a relatively small capacitor of 1000uF and 2000V. If consider that GM70 should be run at 1300V-1400V then this cap is God sent and would make the GM70’s power supply quite simple.

It is not that I am contemplation the GM70 – I relay have no use for such an amplifier - but this event again made me to think about the sound of those high voltage triodes like 211, 845, GM70.

What I feel that those large high voltage tubes trade the brilliance of the details for the size of the presentation. It is not only the “elephant sound” but also the “elephant color”. The elephants are mostly grayish, so the 211, 845, GM70….

Honestly, I do not have my personal experience of teaching the 211, 845, GM70 amps to sound correct. All that I have is an experience of listening of many amplifiers with high voltage triodes. Perhaps they were made improperly, perhaps used wrong drivers, perhaps people did not know how to use those out tubes, or perhaps the OPT were wrong. There are many other reasons why the amps could eat details. I also suspect that to filer out the over thousands volts of GM70 people forced to employ paper and oil capacitors. Paper and oil capacitors dry out sound and eat the sonic nuances very aggressively. They do work in speakers crossovers but they behave very poorly anywhere else. Anyhow, I do not know the real reason I juts know the result.

Now, let look at the installations what I heard the 211, 845, GM70. They all were not the flea power minded installations with “large minded” speakers but they all imploded the flea-capacity acoustic systems. It is well know that I do not have a lot of respect to DIY community and the speakers they produce is even worst then anything else they do.  I have seen people build crazy 1100V amplifiers and run them against the Avantgard Duo, against Verity Parsifal or against the home brewed single driver back-loaded crap. The point is that the people who were impressed with the presentational mannerism of those 845 or GM70 (and partially the 211 that has much less the “elephant effect”) were looking for their amplifiers override the misery of their acoustic systems. The fact that they were loosing the delicacy, details and tonal fragility were completely irrelevant to them because their loudspeaker were not able to handle it to begin with.

Perhaps I am incorrect and there is out there an interestingly performing GM70 amp. There are almost excellent performing 211 amps. So, what is it: voltages? Tube? Implementation? The Moronity of the builder? Go figure…

In the end it is my strong feeling the “size” of playback presentation should be handled ONLY by the effort of acoustic system and it’s relationship with a listening room. The imbed the “largeness” into amplification is wrong…or perhaps less desirable… or perhaps I did not see any good examples how it might be done properly…
 
Rgs,
Romy 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
06-07-2006 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 8
Post ID: 2489
Reply to: 2488
Re: Jumbo Sound
I'm sure there are many bad implementations of the 845 and 211. Almost all of the commercially available ones are pretty mediocre. However I have heard good examples of both so I know it can be done. I've yet to hear an impressive 6C33 amp so it wouldn't be my first tube of choice but I'm sure such an amp can exist. Your Melquaides design may be that amplifier, I don't know.

I find it amusing when people talk about the sound and character of different tubes when most of what they are listening to is the sound of the power supply attached to them. How you can conclude that this tube sounds 'grey' or that tube sounds 'big' is beyond me. Its like trying to describe the sound of a drive unit without reference to what enclosure it is used in.

Keeping power supply considerations constant, I am currently enjoying using the often overlooked small DH triodes like the 26, 12, 10Y and 71 as line stage or input/driver stages (particularly when choke loaded or transformer coupled) These are all preferable to my ears to the more commonly used and 'modern' higher mu tubes.
06-07-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 9
Post ID: 2490
Reply to: 2489
Sound of tubes or the sound of attitudes.

 guy sergeant wrote:
I'm sure there are many bad implementations of the 845 and 211. Almost all of the commercially available ones are pretty mediocre. However I have heard good examples of both so I know it can be done.

Actually I did not talk about the “bad implementations” but rather about a common quality of any implementations. Also, the “Jumbo Soundness” of 845, GM70, and in slightly less degree the 211, was moistly perceived by people as virtue, not as a shortcoming. In fact the people who make those amps bravado with the “largeness” of the sound.  As I said above the “big sound” is a virtue of acoustic system not an amplifier….

 guy sergeant wrote:
I've yet to hear an impressive 6C33 amp so it wouldn't be my first tube of choice but I'm sure such an amp can exist.

Try the old version of Lamm ML2, you might learn a lot from that sound. I did.

 guy sergeant wrote:
I find it amusing when people talk about the sound and character of different tubes when most of what they are listening to is the sound of the power supply attached to them. How you can conclude that this tube sounds 'grey' or that tube sounds 'big' is beyond me. Its like trying to describe the sound of a drive unit without reference to what enclosure it is used in.

Actually when I refer to “gray sound” I did refer to PS, didn’t I? I also was under presumption that when people built their SETs they use the PSs that benefit the given design. Still, I personally did not play with the “large triodes” and whatever I was able to heard form those amps I accept “as is”.

 guy sergeant wrote:
Keeping power supply considerations constant, I am currently enjoying using the often overlooked small DH triodes like the 26, 12, 10Y and 71 as line stage or input/driver stages (particularly when choke loaded or transformer coupled) These are all preferable to my ears to the more commonly used and 'modern' higher mu tubes.

If you prefer the specific tubes in context of the keeping the “power supply considerations constant” then why do you “find it amusing when people talk about the sound and character of different tubes”?  It is not the question that requires an answer but juts a rhetoric point of inconsistently of judgments….

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
06-07-2006 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 10
Post ID: 2491
Reply to: 2490
Re: power supply considerations & scale
I have a preference for making the power supply a certain way and using certain types of components. If I do that and am consistent about it, I can get better results from some of those old tubes than I can from the more recent types.

But hearing one 845 amp in one place with one type of (probably inadequate) power supply, hearing a different one somewhere else and then maybe hearing a 211 or a 300B amp and from those experiences forming opinions about the 'sound' of those tube is flawed. I'm not suggesting that is what you have done but it is what many people seem to do. They form an idea of the sound of the 845 or the 211 or the 300B but there's no consistency in what powers each of those amps.

On the subject of putting 'scale' into your playback I'm not sure I agree that it can only be done by the speakers. I'm probably thinking more in terms of dynamic range but I've heard phono stages and power amplifiers that sound correct in many ways but very small or constrained. The line stage I'm listening to at present sounds 'huge'. Not in terms of the size of instruments or the spatial presentation of anything but in an unlimited, generous, unforced and very natural way that allows the music affect me more deeply. This unburstable characteristic is also audible via some small bookshelf speakers I also have.
06-08-2006 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 11
Post ID: 2496
Reply to: 2182
GM70 advantages? How real is real?

I have to tell you something: I do not believe to audio people. Whatever they say has some freakish twist of desire to present the sings in a certain way instead of witnessing and experiencing the thighs as they are. This is one of the reasons why I generally despise the DIY community: they are incredibly boring in their everlasting hobbysm.

I also hardly believe myself is I have no reasons to know the things defiantly. Above I make a bunch of the observation about the 845, 211, GM70 but I never had any of them in my listening room. Since I have seen very few people who preach the playback system and sound reproduction from the positions that I consider “serious” then what evidence I have that those somebody else’s 845, 211, GM70 amps meant to be “serious”? Yes, it is very much correct that my comments above about the powerful triode were based on bad examples or heard in context of bad installations. So they should be understood appropriately. 

It is very difficult to talk about the soldering people about sound. For instance today I read a witnessing of Nicholas Chua about his observations regarding his GM70 amplifiers:

http://diyparadise.com/nikcgm70.html

I like what he did  more or less and what he wrote. In the end he mentioned a little about his perception of the GM70 sound. That part I got different:

  Nicholas Chua wrote:
The Sonics of the amp I would not lie to you, it is great with lots of potential. Feels like a very powerfully 300B and 2A3 amp. It has the nice midrange of the 300B but with the balance tonal of the 2A3. Bass control is excellent here and the amount of bass that can be pump out is insane for a SE amp;

What? What I experienced the properly implemented DSETs do deliver insane bass, not juts insane but absolutely unreachable by any other topology. Yes 300B never has bass but it also never has anything else beside 3-4 octaves on the middle. So did Nicholas discover a good bass with GM70 or he discovered a better bass then 300B?

  Nicholas Chua wrote:
there is more high frequency extension with this amp then my 300b amp.

Good grief! A telephone has more HF then 300B!!!

  Nicholas Chua wrote:
What I like in particular is that at low volume and high volume the sonic character is the same.

Actually it is very interesting quality. But the very next question I would ask what kind loudspeakers Nicholas uses. Usually the sonic character falling apart at high volume because the 300B and 2A3 die driving sub 100dB sensitively. 35W of the GM70 would defiantly help. The 350W of the SS A/B PP would help also… :-)

  Nicholas Chua wrote:
This trait shows the control and power sufficiency of the amp to control the speaker when both posh listening and the wild rocking head banging volume levels is played. The amp plays both rock and other music well. Ziggy Stardust by David Bowie plays now with me rocking in the middle.

No comments…

  Nicholas Chua wrote:
Because of good bass control, double bass plays with great authority. The expansion of the double bass is now very apparent like the how it should sound when you stand/sit 2meters away. Normally in most amps, the double bass is the often miss played instrument where the sound is muffled, not there at all, worst the box is heard but not the string being plucked.

I was under impression that with 140R on plate of 6C33 is possible to get much more interesting bass. Taking about the DSET…. The single channel of Melq will have 15000uF in B+. I wonder how mach space this capacitance would take if it were for 1500V and how many extra turns the amp would have in the output transformer in case the GM70.

  Nicholas Chua wrote:
New World Symphony Largo LP Brass sections did not lack the speed and timbre associated with SE amps but it is noted that it is still slower than it should be. Because of the non-feedback the speed is not compromise where feedback tends to muddle with the speed as some of the signal is feedback to input thus slowing the sound. But with all SE amps there is more swing in orchestra pieces.

Honestly I did not understand it.

  Nicholas Chua wrote:
Separation of the instruments seems to be good too and there clear audible distinct between instruments being played not just a sound wall.

Is it after the 300B? I think the same effect would be if Nicholas would drive his speakers from 8-track car radio – it is the 300B is meant for…

Anyhow, I certainly did not mean to mock the Nicholas’s view but I juts do not see so fat the credible views of the GM70 builders. If someone feel that they have something to say regarding the SOUND of the GM70 vs. 6C33C then feel free to do so.

Rgs,
Romy 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
04-26-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010

Post #: 12
Post ID: 18094
Reply to: 2496
GM70SE VS 6C33CSE
fiogf49gjkf0d
I just finished the GM70SE amplifier. It is built on the same size chassis as the 6C33C (with few extra holes) but 1/2 in higher to accommodate quite a few extra parts.
The GM70SE is built with quite interesting feature similar to 6C33CSE :
- Double Tube rectifier & voltage regulator: A first of its kind, it has 1100V regulator for the GM70 and 550V regulator for the input and driver stage. The 6C33C has the same regulator but at much lower voltage.
- No coupling cap in the signal chain, 3 stages design with interstage for driver. 6C33CSE has 2 stages with interstage transformer.- Oil & film cap used for B+ (no electrolytic)
- At 35W it has almost twice the output of 6C33CSE, it should since the GM70 tube is run at max Pd of 120W.
I would not comment on the sound right now, since I will have to play with at least 3-4 driver tubes to find the best match for the GM70, and that might take many moons.



IMG_8034a.JPG
04-26-2012 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,535
Joined on 05-28-2004

Post #: 13
Post ID: 18096
Reply to: 18094
The GM70 SET
fiogf49gjkf0d
Well, as I understand there is no truly GM70 vs. 6C33C context yet (sound in the respectfully equitable load) from you and it will be very interesting to hear from you when you feel that you are ready to say something. As I understand they are the same topology amps only with different PS to care the output tube’s plate voltages. Do you feel that both GM70 and 6C33C amps have the same quality output transformers respective to own pate impedance? In my estimation if everything is made properly then the cost of GM70 OPT shall be as high as the cost of the whole 6C33C amplifier….

About the driver – you know my agenda: I would like you to try my 6E5P driver in the configuration I use for Milq. If you even go there than let me know. Sine you have 3 stage design then you might try what Russians frequently use to drive GM70: 6N6P or 6H30. Bothe tubes are very good sounding current driver’s ether as gain stage or as cathode followers.

I also not a huge fan of oil & film cap used for B+ instead of electrolytic. For my low voltage designs (sub 450V) I experimented a lot with oil and film and oil with paper caps and I never find them to sound satisfactory. They sound to me “too defused” and make lower octave too “mushy” if I might say so and I always prefer sound of good electrolytic. I do not like even film-only caps for PS. I know many people would disagree however. For sure in your case dealing with 1100V in plate it is hard to find electrolytic but if I were you then I would go over the considerable expense and went for electrolytic.

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
04-28-2012 Post does not mapped to Knowledge Tree
KOTriode
Posts 40
Joined on 07-20-2010

Post #: 14
Post ID: 18105
Reply to: 18096
Give the GM70 the best shot.
fiogf49gjkf0d
It is impossible to make two amp with the same quality with such big difference in output tubes , the transformer design are vastly different, a 10Kohm transformer would never have a good bandwidth as a 600ohm transformer. I just have to experiment quite a few thing to make the best possible result for the GM70and compare the two amplifier. But I do have what I think the best output transformer for the GM70 to squeeze out its maximum sonic capabilities to give the 6C33C a best shot.
Regarding caps, I think I know why you found the lower octave mushy, the problem is that it might not have adequate capacitance. My rule of thumb regarding capacitance is 500uF per 100ma of current, with 6C33C you will need close to 1000uF to get tight bass, and it is impossible to get quantity of oil&film cap in one chassis. This why I chose to use the voltage regulator, the amount of capacitance needed reduced to less than 100uF which is more reasonable to realize with oil and film. It is much easier and cheaper to use electrolytic at high voltage( you just series a number of them and get the voltage you want), but I prefer what the oil &film does sonically and chose the difficult path for the power supply.
After playing through this GM70 amp, I will experiment the 6E5P which I just bought 20 of these for the 6C33C, the Melquiades circuit is in the work for a pr of 6C33C amplifier, there are so many things to try and it will take time....
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  »  New  6C33C myths: audio Moronometr...  Overdrive warning light...  Melquiades Amplifier  Forum     3  38792  06-22-2005
  »  New  The loudspeakers for a powerful SET..  Mission Accomplished?...  Audio Discussions  Forum     48  283929  04-11-2008
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