Romy the Cat wrote:

Still, doing whatever crazy and Macondo-dedicated things I will be doing with one stage I will have my full-range Milq as a tested reference trying to get result no worse then the one that I got from a “default” Melquiades …

It was quite serious, rich and meaningful Sound the Sound the ignited within me lethargy to destroy the Super Milq, pulling form it the MF output transformer for the single-stage Melquiades. The Sound was so balanced and so “compiled” that to take it apart would be an act of real barbarianism. Frankly speaking I was so comfortable and so contented that I was wondering if I even what to go for the single-stage Melq… Sure it might be interesting to try to see what would happen  but it would open a Pandora box for many other prospective “issues”.

It is quote nice as it with no extra efforts invested… I do not know… I will not hurry this case…. If someone make for me the necessary uncompromised MF and HF output transformers then I would make the single-stage Melq. If not then I will keep what I have now and will keep bitching that the world is the place filled with mean and non-cooperative people….

Ah, how wonderful would be if I could write a check to someone and that someone would bring the build amp in my room in a few weeks/month…

Now I re-listen all the things the we try to measure. To surmised everything I have to tell that Dima’s way to looks for optimum operation point of the tube (setting balance for voltage vs. current sufficiency) turned out to be very successful as I did not see absolutely no discrepancies between auditable and measurable. As long the tube has the identical and symmetric current and voltage clipping it does sound the best. I have no idea why audio  people create so much “cult” about finding the best operation points for tubes and why any controversy exist – it look so simple and so unambiguous – for one stage of course.

Anyhow, I was not able to listen the Single-stage 6E5P with horns. The tolerable volume level I got driving Vitavox with 0.6-0.7V… VERY far from any dangers regions. So, I took 16R speaker with 90dB sensitivity and drove it with Single-stage 6E5P. First - the 0 bias on the tube – it was absolutely unusable, sorry ml8…

The best sound I got from this tube with ~ 6.5-6.8W dissipated on plate. More power made the  sound more stiff less power made… less power…Now current vs. voltage (with 16R load) keeping the same power. More voltage and less current made Sound “brown”, more compressed and in a way “inverted”.  More current and less voltage made it sound suffocated. In a way deficiently in voltage or current both produced that over- damping effect at upper bass and lower midrange but that over-damping sounded different for voltage and different for current. It is have to explain in words but it is VERY much the same as over-damping of bass when we adjust VTA of cartridge vs. lighting of bass when we change the tracking mass.

Ironically the best subjective sound I got in the best measurable point. I did a few blind tests  with different tubes when I was trying to set subjectively the best sound adjusting bias without looking at miliampermeter of the plate current. In all cases, finding this operations point and then driving the amp into distortions I has the perfect symmetrical pictures of voltage vs. current. It all was at the same current but at different bias settings (from minis 3.1V to minis 3.8V). So, the “magic” number was 175V and 38mA…

Now is the quandary… Do I have to for the Single-stage Milq pre-select the tubes or I need to put bias adjustment in there? Perhaps only for upperbass channel where I “might” be important. Now is the biggest question: now important all of this? All those experiments took place with amp outputting 3V but during it live the Single-stage Milq will do less then 1V. I do not have a full range 109dB system to assess subjectively how will sound. Listening single channels I can say that the deviation form perfect voltage vs. current setting is WAY less (if any) auditable at 0.7V. So, I need to think how important it might be in the real world.

Jim, returning back to the subject of tube testing….

I do not know if you have seen my most recent obsession; the idea of driving my Macondo with 1.8W of a single 6E5P:

http://www.goodsoundclub.com/LatestPosts.aspx?ThreadID=4241

So, what I learned is that all 6E5P, regardless of vintage and lever of being used up have the same 30 times gain. So, it is a drastic improvement over the very uneven gain of 6C33C. Still, all 6E5P have different ability to produce current – the stupid Russian tubes! So, sine I know the exact operation point for this tube and sine I will have the adjustable base for each channels of the single stage Melquiades then what might OBJECTIVELY indicated to me the life span of the 6E5P? The cathode emission? The transconductance? The use of getter? The darkening of the glass? Where would be an objectively correct point when a tube consider “gone”: 10% less of cathode emission, 30% less of cathode emission, 50% less of cathode emission? Is it wary from tube to tube and some of the sound fine with 50% less of cathode emission and with less bias?

hagtech wrote:

Stepping back a moment, I'm guessing this tube is designed for radar operation.  Maybe in an aircraft.  The spec sheet definately talks only about pulse mode of operation.  Maybe it was a driver for a pulse radar transmitter?  What this means to me is that there are some sacrifices made in the tube.  It has a very limited maximum average power dissipation.  This had to be done in order to keep the structure small enough that it would operate at the desired RF frequencies.  It has very high pulse current capability, so the cathode must have extremely high emission, or plate gets starved and curves fall over.

Jim, I think you look at different datasheet. The 6E5P never meant to be used for pulse operation. The Datasheet said that it was designed for broadband amplification of HF.

http://www.goodsoundclub.com/PDF/6E5P.pdf

The 6E5P was use in railway radios transmitters, in portable SW radio stations, in some consumer radios in 60s and reportedly in TV applications. The 6E5P did have a version specialty dedicated for impulse operation. It called 6E5P-E. It has visibly the same constriction but extra short balloon:

http://www.goodsoundclub.com/PDF/6E5P-E.pdf

A few years ago I foolishly bought 100 of them (I think I paid 8c per tube) and they turned out to be VERY different sonically then the 6E5P and I found them unusable (about which I warned in the Melquiades article). BTW, you might see them on the picture:

The number 2 on the left in the first row is the 6E5P-E. The number 4 on the left in the first row is a normal 6E5P.

hagtech wrote:

So I have an idea.  For class A operation, the cathode emission is way too high.  We cannot run at the high peak currents because the plate will melt.  Or at least overheat and cause secondary emission problems, glow, etc.  Therefore, I suggest starving the filament.  Let's think about running this tube with 5V heater.  I'll run some sweeps to see what happens to the curves.  I think adapting the tube from pulse operation to continuous mode is no problem.  The lower emission is still enough for our needs, and it has the side benefit of greatly increasing lifetime.

Well, sine there is not need to fight with impulse mode I do not think it is the problem. However, the idea to starve filaments I very interesting. For LF horns I would need the full 6.wW on plate but for HF horns I need a fraction of watt and I might drop the heater voalsh, prolonging the tube lives. I will also make some Dima’s voltage vs. current tests (BTW, I found it VERY cool approach) with lover heater voltages.

hagtech wrote:

Most importantly, I think we have to keep the plate dissipation way down, like 6W or so.  Cannot let the G2 get too hot.

In my experiment I would say that up to 6.8W it behaved reasonably and more or less proportionally increase power with inverse voltage. I have to note that went I drove my 109dB upper bass horn with minus 10dB digital off my 5V DACK at 13:1 and having 6.6W on 6E5P’s plate then I took a think blanket and patched the mouth of my horns because it sounded louder then civil defense bombing alarm. I presumed that it offset the horns resonant frequency quite aggressively but it was the only way to test it under the live condition. With a “tampon” in the mouth that horn would be too violent to be with it in the same room.

hagtech wrote:

I like the direction you are headed.  This tube will sound better and more natural than the 6C33.  But might lack "authority".

Well with 109dB sensitively there are very many rational to go into the direction I ma going… how it will manifest itself in Sound I have no idea. I personally less care about “lack of authority". It is 109dB and I need just 0.7 V to pump into my speaker to get listening level. I more concern about ability of this single tube (and it is VERY fast tube) to play “slow” and produce the necessary “acoustic like” and “dynamically viscose” harmonic pattern. It did it with two stages but I do not know if it will with single stage. The individual channel looked like sound fine but how it will be in context of the whole installation only God knows…

hagtech wrote:

For a single driver, looks to me like you need an input signal of at least 3Vrms.  A lot of linestages can do that, so a single tube power amp seems both reasonable and interesting.

What actually I discovered the last week makes me VERY enthusiastic. I usually drive my horns with under 1V that… make it possible to drive then with …. preamp. Sure it doe not pump a lot of current but still it is possible sine I need no bass and no electric cones damping. Anyhow, I was experimenting with the single-stage Milq (the full gazed version not the prototype) and ended up trying with my Denon D30 mini-system. As I told before the D30 is amazing crap but still I have a bunch of small monitors that the D30’s 22W amps drives… So, I took the D30 headphone output and drove with it the single-stage Melquiades. To my great surprise the result was nothing short of stunning – I absolutely did not expect it. Sure it was not able to drive it with a lot power – increase of volume sent Sound to ugly clipping but at very low volume the Milq absolutely overridden the D30’s sound making it to sound very large, VERY dynamic (…and it is with the Celestion SL-600!!!!), surprisingly colorful and very inversing…. I was very pleased and puzzled with this effect….

BTW, Jim (and others) I have difficulties to source the necessary transformers for HF channels of single-stage Melquiades. Do you know any sources that sell the amorphous core for transformers in small quantities?

hagtech wrote:

You know, for somebody just taking a snapshot of a bunch of tubes for a forum post - it's really quite good.  Has that Ansel Adam's look.  I'd swear you used film.

Not really it was an old image that I took from the bottom of the Melquiades pages.

cv wrote:

Hi Romy, I dunno if you mean the C-core materials itself or the completed transformers... if the former (perhaps a poor term in this context), then http://www.elnamagnetics.com have what you are looking for. Seach for AMCC - these are the Metglas C-cores you are after...

Well, Bud do not mind to wind HF transformer if e find an interesting raw core… I hardly doubt I will find anywhere a ready to go transformer with my custom DSET HF specifications…

cv wrote:

Also, if you are able to limit the LF before the power stage,

Well this it VERY big subject. As you remember in two stages Milq I was not able to high pass the amps at line level as it created very wrong sound. I have a number of hypnotizes about the resume and the single stage amp would be a good playgroup to try it. I do intend to high pass it if I could. There is a great chance that in the two stages Melquiades the high pass was not possible die to the application in the given topology. I spent a LOT of time to experiment with it.

cv wrote:

I would very strongly suggest trying a custom OPT from Sowter in the UK on a 100% mumetal EI core for the S2.... expensive but something magical about the sound.

Chris, can you point to the specific model of the Sowters OPT?

cv wrote:

If we agree on the spec beforehand, we may even be able to come to an arrangement where I purchase them from you if you don't like them so you're not risking much. Feel free to PM me if you are interested.

jd: I'm celebrating the 1 year anniversary of my order for custom transformers from AE Europe.
It suits me fine that they haven't delivered (because I don't have the $ now), but you may want to be ...less than overly optimistic.

I don't know about the waiting time with Tribute transformers.
Perhaps Dave Slagle (www.intactaudio.com) could do the job?

First of all thanks to all who assist me with this project, including those who did not post here.

Jim, Electraprinted Jack is great guy but he does not believe in exotic cores, very unfortunate because I like to deal with him.

Jessie, you are right I did forget the AE Europe source. It would be interesting what they say. BTW, I would need all secondary sections all go outside with marked polarity….….

op.9, could you in term of subjective impressions and associations describe what your Sowter did with the Sound of you treble horns?

Still, without exclusion of all other opportunities, I would like Bud to bid with his transformer wounded around an amorphous stick or amorphous bagel…

Anyhow, I would like to share some my concerns about the transformers for Vitavox S2 channel. A common thinking about famous transformer would not be really applicable in my case as I did not see anyone judge transformer in context of DSET use. Within a very low power, within very small size and within a very limited frequency range it would not be difficult to make a very good transformer but then the question would be: how to make it to sound in a seatrain way. This is the zone in wish I have absolutely no experience which buttons to push and no knowledge what ingredients to mix. I less case about the transformer for tweeter channels – there is not a lot of sound there but with the midrange with S2 driver the transformer in this project would be a very interesting subject.

Let me I explain my objective for this transformer. In my mind  (the mind of user bit the designer) in this transformer should be 4 entities that should be properly balanced:

1) Harmonics
2) Speed
3) Dynamics
4) Connectivity

HARMONICS is hardly the properties of the transformer itself but rather the plate loading via transformer. So the secondary sections should be stuck out allowing remapping the sections on fly. Still, read about the “speed”.

SPEED should be maximum possible. However it is a different speed then juts unloading the tube, striping the harmonic tails and converting SET into the crappy OTL sound. Usually in “betters” SETs the output stage loaded slightly les and it create the feeling of speed. I do not like it. Along with this “speed acceleration” the sounds slightly flatten the parabola with which the notes roll it their pitches. As the results it create slightly “flat” (musically) sound. The speed that I am taking about should not interfere with harmonic pattern. It should be maximum speed of exchange of information but it should be absolutely indifferent to harmonics. Still, read about the “dynamics”

DYNAMICS should at it max as well but there is more to it. The speed of information exchange should be identical (or different) at different dynamic ranges. I do not know if at minus 60dB the speed of information exchange should be identical to the minus 20dB. It might be that it should have own speed deviation… However, when it sounds I know that it is wrong when it sounds wrong.  Some transformers do change the speed of information exchange at different dynamic ranges but they do it according to wrong algorithms. I do not know what the right algorithms are: I am not in the business of design the things but in the business of bitching about others. Anyhow, for my transformer I would like it to be able to have own dynamic intelligence and know what speed to demonstrate at wish dynamic level, still keeping the dynamic window as wide as possible. Still, read about the “connectively”.

CONNECTIVITY – this is the key. The connectively is something that differentiate a right transformer from anything else. What is important also that a good transformer should have absolutely maximum connectivity with absolutely maximum speed and dynamics. So, what the connectively is all about? The connectively is the association between the events that being transmitted via a transformer. The individuals sounds, properly harmonically structured at this max speed and with no compression it not enough. In music notes have inferred references to other notes and even if to virtually cut out of music the referred notes (along with their harmonists) then the referencing notes still will imply the removed notes. Bad transformers have no speed and no dynamics but if the bad transformers do have speed and dynamics (with correct harmonics) then they have no connectively between the notes. With bad transformers sound feel like a porcupine’s back with a zillion individuals needles stick out of Sound and each needle do not know about the sharpness of other needles. In a good transformer each needle of event (would it be a note or a pause) are kind of managed by one mind, the same mind that manages the speed and dynamics. Also it is very important that the connectively should not be loosing itself at high and low dynamic levels… In a way a transformer in it’s connectively should be more like Michelangeli play….

Well, I would love to tell you that I know HOW to do it but I do not know. The only one transformer that I have seen that had the absolute maximin of connectively, speed and superbly smart dynamics were the Expressive Technology transformers. Well, it would be very interesting to find the transformer for my S2 channels that would be able to do the same. It looks like that within a limited bandwidth the task should not be  too difficult…

Chris,

I head a lot a lot of good thing about Pieter from Tribute and I would like to recruit him for the s2 transformer. We send last week to him an email and he did not reply. I heard from many other people that it is a very typical for his communication pattern. So, it dificalt if he is not accessable to communicative? I do not know also how Bud’s amorphous transformer would be, I do not think he knows either but he is not only accessable but also abuseable. :-) since I have very limited ides what I need technically it is very important to me that someone could listen all my "verbiage" and in his mind to convert it into the implementable specifications...

Anyhow, I if you feel that it worth try then I do not mind to try the Sowter’s mumetal transformers. I was also thinking about the 200Hz from bottom, 50mA gap. Let presume that I WILL BE ABLE to high-pass it at line level and that the MF stage will NOT handle the full range signal. Then the key would be to have the minimal amount of turns in primary, preserving best coupling with objectives to serve the necessary ratio (since we have no heavy inductance demands). About the ratio. I would like to have 12:1 with half-&-half. It means that all secondary sections should go outside to some kind of mapping board and if I connect half of then in serial and half of them in parallel then I would like to get in this setting 12:1. Fell free to convert what I meant to say into a format that would be more comprehendible for the Sowter guy. Feel free also to suggest what I am thinking wrong.

Allo

Pieter is super-talented and a great guy; if you are a Larry David fan he looks a bit like his Dutch cousin...

The only problem is that he has a long waiting list... I don't think you would get the OPTs any time soon.

If we will try Sowters then I would suggest:

Primary inductance of about 2H, for use above 1kHz.

Turns ratio of 12:1 would give you a 2.4k load with 16 ohm secondary.

With a gap of 50mA, I reckon on the order of 1-2W may be possible at 500Hz - let's see what Brian thinks once spec is complete. Not sure the biggest mumetal core they have will handle much more.

As for secondary configuration, if you don't need the facility to play with taps, you are generally better off without all the connection options as you don't have to re-terminate all the secondary options. (The secondary will always need to be sectioned internally). If you do have taps, it's vital to use the entire secondary or else the tx is suboptimal.
Sowter have a range of options, scroll down at:

http://www.sowter.co.uk/2se.htm

So you pick any option except the "tapped" one! I don't understand why you want to insist on half series/half parallel connections when internally, the secondary is made of more than 4 sections? Just because the "mapping board" has 4 sections coming out of the tx...

Anyway, I will email Brian and see what he reckons.
cv

I would defiantly avoid any taps by any cost, regresses how “advanced” they are implemented. On the page that you referred the first configuration, with secondary sections sticking outside, looks like a reasonable to me.

Yes, the 2.4k to 3.0K load with 16 ohm secondary would be fine but only in the middle of that first configuration. I would like to have at least one, one a half kOhms up and down. As I undusted the re-termination and remapping of secondary does not affect sound in any way.

One of the reasons why I do not know where to lend because I do not know what kind “contrast” Brian’s transformer will give. If case of “contrasty” sound it would be nice to drop I would say 500R and to load the tube slightly harder. It is really does not cost money and do not affect sound. So, why not to have this option…

BTW, Chriss I have two questions,. What will be the range of the prices for this MF transformer and what you thoughts I might do for HF channel transformer (>12K and up). I think we spoke about it in past:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=634#634