GoodSoundClub - Romy the Cat's Audio Site

03-26-2011

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Romy the Cat

Boston, MA
Posts 10,160
Joined on 05-28-2004

Post #:	26
Post ID:	15863
Reply to:	15862

Yes, it is interesting to fantasize

A few days ago a friend of mine and I did spent over an hour to fantasize what might be done if the ULF tube SET is planned. It is not so simple as to drive the tube like 833/GU-48, you will not be able to do with Milq driver. But I also would like do not have 3 stage amplifier. It needs to be a powerful driver tube that itself will be able to work at high voltage. Ideally I would like it to be direct coupled, the same way how my MF amp is made with second PS float the driver tube. For sure it would be a complex amp but I would like to avoid any inner-stage transformers. I have a paranoia that in any devise shall be only ONE transformer in signal pass, do not ask me why but I would like do not search for one million henries line-stage transformer…. So, 500K-600K input impedance, 30dB gain. 150-200W in Class A, single ended, two stages, no SRPP in driver stage, no parallel drivers stage, ultra-low impedance of output stage PS, a lot of headroom for driver and output stage, a very large non-sectioned output transformer. I true like the idea of paralleling of output stages by 6C33C. If you drive it at 55-58W then it has Rp of near 100R. Connect 10 of them and you have 200W with combined Rp ultra low. You can use 1:1 transformer with primary impedance of a few Ohms. You can make very insulting amp this way. In fact I am not sure if it would not be possible to pass right and left channels across the same amp. It thinks it might be possible to sample it high rate and make non-auditable for LF.

Anyhow, I am for sure will not be doing it but indeed it is fun to have some fantasies about it.

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

03-26-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	27
Post ID:	15864
Reply to:	15863

833 DC to 833?

Actually those fantasies may come true one day...I may be wrong, but I think
the tube-speaker interface is more important than sticking to 2 stage topology?
2 stage => high-mu output tube => high Rp, low controll over the array.
But, if you insist, perhaps 833 driving 833, DC coupled may do the trick?
More elegant than 10.000 6C33C Smile

At 2500V/100mA 833 seems to have approx 4k Rp => 130H. Not bad Smile

Worse as a driver with 4k output impedance...The driver choke loaded of course. 200-250H
872A FW and low DCR PS chokes should give a good PS.
Caps are the problem, esp. in EU, but perhaps 100uF/3kV are obtainable?
Doubling it and stacking will not be easy...Would be happy to go along with one supply only,
like in your MF, but decoupling at 5Hz....lots of uF@3kV

BTW, there is the beefed up version of 833 -- 833C with 550W max forced air cooled!

Cheers,
Jarek
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03-30-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	28
Post ID:	15891
Reply to:	15863

Drum'n'bass party amp

I've made an itellectuall excercise and tried to see hoe to fullfil (some of) Romy's
points regarding the bass amp.

1) To get 100+ W from 833, HT between 2.5kV and 3kV will not work.
Spending some time over the curves, 1400V, 0V, 280mA loaded with
6.5k should give 130W with the swing approx. +60V to -60V, grid current 80-100mA.
According to the data the tube can handle this power 390W if force air cooled.
I'm wondering what is the GU-48 secret knowldge. How does people abuse it?
At this pont the Rp is approx. 3.3k, so 100+H should give 5Hz.

2) The driver is the hardest element: gain around 30, support 100mA grid current
and have lowish Rp. At this moment nothing comes to my mind as other 833.

3) I have a problem with DC: I do not know how stable that would be. The designs
I know (Axiom, Romy's MF, etc) have a cathode bias, which gives some self-balancing.
Here we don't want cathode bias. What is the advantage of DC? No cap/IT. But
their most nasty features reside in MF/HF, not in bass. Besides the driver has to be loaded
somehow and loading it with a resistor is a waste of power. Since we don't care about anything
above 200Hz, the difficulty between making an anode choke and an IT is not that big--we couple
only via the core. I'd even experiment with Dave Slagle's idea of canceling some of the DC flux
with the heater current. The resulting intellectual proposal is below:

Cheers,
Jarek
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03-30-2011

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	29
Post ID:	15895
Reply to:	15891

Bread Board

Well, I am looking forward to a movie of those giant caps going off! Shades of van de Graaff! What do you figure the size will be? Hard to tell until you begin working with it what the "mystery" values will be, such as giant-wire capacitance, EMF-expressed-as-noise-and-?, etc. 70H?!?

Sucker ought to get waaay down there, however...

Best regards,
Paul S

03-30-2011

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Romy the Cat

Boston, MA
Posts 10,160
Joined on 05-28-2004

Post #:	30
Post ID:	15896
Reply to:	15891

Anybody is willing to build something like this?

N-set,

actually, as you drew it, it became not too complex amp. What I would like to find is some kind tube like 833 only twin triode. Then it would be possible to have one chassis with a single drive and two output power stages. With 100W on filament in one tube I think you understand where I am coming from…. For sue I would go with SS rectification and LC filtration. Where to get caps on this voltage is another question. Thos high voltage paper caps are small values… Dima, BTW had an idea to drive a choke with 600V tube… Anyhow, it is not as complex and I initially thought, for sure I am not considering to built it but if someone would do and agree to bring it to my place then I would assist, at least spiritually…

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

03-31-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	31
Post ID:	15897
Reply to:	15896

Me...

...but it will take me N-years and I'm in EU Smile

I could make some preliminary steps this Easter, talk to my winders about transformers etc.
I'm for sure missing the FW and out put cores (AMCC800A will not support 120H at 300mA, low DCR),
but getting mastodont C-cores in Poe-land is not impossible...for a good price.
The driver: I have no better idea at the moment and worse, I'm not sure if the current idea, Sakuma-style, is any good either.
3.3k is not a little and your 2-stage contrarint gives no chance foe a step-down transformer.
I've been trying to find a Spice model of 833 to play with it a bit. Anyone has it?

SchutzStaffel---one could in principle connect in series 4x 1200V SiC's, I'm wondering
if that would be cleaner, switching 1670V, than MV's, which are a PITA to implement and generate a lot of RF.
They need a CM-chokes at the heaters, ferrite beads at the plates and an electrostatic cage
apart from the all the heating ass-related problems, so SS might be the way.
Caps: in US for sure much easier to get (lasers), but ocassionally in EU also:

http://cgi.ebay.com/9x-HUGE-MONSTER-RFT-OIL-CAPACITORS-50uF-2-3kV-2kV-3kV-/350449979135?pt=LH_DefaultDomain_0&hash=item5198724eff

If one loves electrolits and mega uF, one could stack 550V Nichicons. They seem $$$$ at Mouser Digi-srigi etc, but if you ask
directly in China I've been quoted $160 for 4pcs 10.000/550V NIB! I haven't examined the source though.

What I'd love to know is how people abuse GU-48. There are for sure people who tried moving past the official data.
I'm wondering what problems and what measures to deal with them they have developed. Any such insider info Romy?
How is GU-48 at 400W air cooled?? How is 6.5k load at that point?

Paul, I'm sorry but I have no idea what are you talking about. What giant-wire capacitance? You mean 150u/2kV
It's not impossible. I've seen once 100u/22kV cap on US Ebay. There are plenty of those big caps for lasers.
What 70H do you mean? The input choke at this volatge/current is "only" 10H but has to withstand lots of AC. I have such chokes, they
are of a size of a good 100W output transformer. The second choke is left open, I'd have to play with the values
so that the PS does not oscillate at the sudden current changes. EMF--all magnetics potted and then hidden in the chhassis,
so effectively double-potted, cores rotated to minimize craoss-talk, RF filtering, etc.
The size...well a 1/2 of a small fridge I'd say, close to 1kW dissipation
each monoblock. A serious toy.

Cheers,
Jarek
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03-31-2011

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Romy the Cat

Boston, MA
Posts 10,160
Joined on 05-28-2004

Post #:	32
Post ID:	15898
Reply to:	15897

Keep the eyes on the ball.

N-set, I have seen a guy at DIYAudio who built an amp around GU-48. I sent his meals but he did not replay. I have seen a few (very view) people in Russia spoke about GU-48 and some of them built something. I do not know what result is.

It is very difficult to get from people who build such amps any feeling about sound. To build the thing is a complex possess that require a lot of knowledge and pretty much years of experience. People got so infatuated with overcoming technical difficulties during construction of the amp that they are losing eyes from the ball and the all purpose of the build stop to be on their aim.

I am sure no one that I heard off made bass DSET around GU-48. The guys who use this tube would try to get the most from the efforts and would go wide range. This is understandable. Moreover, the people who need 150+ Watts of wide-ranges amplification would be hardly the people who use high quality acoustic systems. So, what they think about own amp is kind of irrelevant to me.

The whole project like this in a way an applied waste. It will cost a lot or money, it will cost n-years of time and in the end it will answer very little questions. In fact the questions that the amp will answer will be so narrow that only insane man would do for it. Still, I would be the one who would feel that SOMEONE has to do it. Sure it will be not me, thankfully.

N-set, if you are planning to do something like this then you have to have good reasons to do it, not just a fact the you can do it. BTW, there is an alternative about which I have been thinking. There was in 50s a class of magnetic amplifiers, there very stable and very high power.

http://www.goodsoundclub.com/pdf/magnetic%20amplifiers.pdf

They work well only at LF and this is what I would like to be with this DSET…. I just need to find an old man who still remembers them. I think it might be a good candidate to try for ULF.

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

03-31-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	33
Post ID:	15899
Reply to:	15898

Reasons...

...are some bullshittings we attach to our irrational actions a posteriori merely to justify them.
I think you understand it well. I have that idiotic 304tl project, have accumulated lots of hardware, this may be a way
to make something remotely useful out of it.

Asking about GU-48 black art I did not mean the Sound, no! that would be asking for way too much!
Just some basic technicalities like: "at 400W
it will melt the plate no matter what you do" or to the contrary
"it withstands 400W with no problem without cooling" etc etc. Amateur radio people are the right group to ask
I think. The only hints on the sound I've found in the very same DiYAudio thread is that GU-48/metal plate 833 is bass heavier than the
graphite...which if true is not the best news since graphite can withstand more power abuse.

Mag-amps: will look at that.

Cheers,
Jarek
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03-31-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	34
Post ID:	15905
Reply to:	15891

D'n'B v2

Here is another, simplified assault after some rethink and PSUD simulations.
Rectifier: 3x1.2kV SiC per phase should do the job, actually 2 would do, but I'd prefer
to be safe. Bridge I don't want, as there would be 6 not 3 diodes switching
1750V. 1.2kV 10A SiC's. There are 1.7kV SiC's but in raw wafers which I have no
idea how to handle.

The caps: actually why not stacking electrolyts? ESR worsens, so does the impulse
power transfer, but maybe one could still reasonably bypass at 2kV?. Nichicon has introduced
630V elco's, so hopefully 550V ones will be cheaper (or dirt cheap if bought
directly where made--in China). 500uF @ 1.4kV stores as much as 15.000
@ 250V. It also gives a reasonable damping to the LC cell (low DCR LC supplies are
notoriously resonant). The first cap, let it be PiO to save on space a bit.
The resulting ripple @ second cap is around 70mV according to sims and 40mV if the
first cap is 20uF (which I don't have).

Heating is a pain now. Due to the huge currents it should be DC I think, which adds to the
complexity and weight. Ideally it should be a CCS, but let's try to simulate it with chokes.
Don't get fooled by small values.
10mH@10A stores as much energy as 100H @100mA if that matters...

I was looking for another driver. SV572-30 would be an option (one can still get them
for $80...) but it has higher Rp and mu=30 is a bit low. 812 is another one, but cannot withsand
100mA -8-10V biased, IIRC. I'd stay with 833 at the moment although it's 3.5k Rp may kill the idea.
Audiopedophiles would be impressed anyway, let them listen to a 833 RIAA!

I think it would not be much bigger than Wavac SH-833. And there are people
who somehow think they need 3 of them per channel:

http://forum.audiogon.com/cgi-bin/fr.pl?vaslt&1104825435&read&keyw&zzwavac%20audio%20sh-833

let their gods connect them to the hot 833 plates, so perhaps in light of that idiocy the whole
idea of 833 bass is not that irrational as it may seem? The narrow questions are within 10-100Hz,
projecting to ...Hz-...Hz, I agree,
but maybe an unheard trace of the voice of god resides there?

PS Some idea on how to mount the rectifiers: take a hammond die cast alu box, make 2 big holes and put good
multi kV groomets, put the rectifiers+resitors there
and fill everything with silicone. Then close and forget! The box will shield the RF a bit
(one can go delux and wrap the box with Cu foil, which is easy).

Cheers,
Jarek
STACORE

04-01-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	35
Post ID:	15917
Reply to:	15905

No go!

This whole 833 A2 concept, given the constraints,
is a no go. When driven positive, the grid equivalent resistance drops
down to 1/transconductance level. For 833, being a high-gm tube,
this can be as low as 100R. In order not to distort significantly the driver
should have the output impedance in the 10R region, and at the same time
mu of 35 to maintain the 2 stage topology. Clearly this is impossible to fullfill.
Some of Romy's constraints must be relaxed if one wants to keep 833.

1) active: 3 stage with the stepdown IT to 833; 2 first stages can be DC coupled;
6E5P input would pose much more relaxed conditions on the driver EL34, 845, GM70, whatever,
but increased complexity

2) passive version: step-up input transformer ->driver ->stepdown to the output tube.
this would pose harder conditions on the pre as the seen input impedance will drop, but at least at the ULF the
parasitic capacitances, amplified by the step-up, do not matter;
one may actually try to use the input trans as a part of the input filter; getting one milion
henrys should not be very problematic as there would be no DC; big nanocrystaline cores with
mu=80.000 are cheap now; also the choice of the driver is a bit more relaxed now as one can adjust the gains.

3) resign from A2, move to A1 at 2.5 to 3kV @ 10-15k load, probably very linear
but "only" 70-80W + pain in the ass power supply;
eventually parallel 833 to get into the 150W range and resign from heating in your house during the winter.

At the moment 2) seems to me as the most elegant to implement, but I haven't thought it well over...

Cheers,
Jarek
STACORE

04-14-2011

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Romy the Cat

Boston, MA
Posts 10,160
Joined on 05-28-2004

Post #:	36
Post ID:	16045
Reply to:	2136

Talking about Powerful SETs

It was posted by 6Moons and pop up at some other sites:

“April 2011 - Audiopax Maggiore 100 - Eduardo de Lima reports the pending launch of a new series of amplifiers. " The Maggiore 100 makes 100 watts with KT88 and 130 watts with KT120 in single-ended class A1 (all the other SE amplifiers at this power level operate in class A2 over the high power band and I only know 3 of them - the Wavac 833, the Win Analog 833 and the NAT Magma with the Eimac 450 tube). Maggiore production will be done in Switzerland near Zurich. We are finalizing the amplifiers (several prototypes have been playing for a long time) and will premier them at the Munich hifi show. The new amplifier is based on the M88s but takes some of the original ideas to a new level. I believe it is a much more mature product. I had expected it to be better than the 88s but the extent to which it turned out better has surprised me. It was one case where I had to do a little revision on my theories not because it did not work but because it worked too well."

It looks like it will be using 6 x KT120. I am sure that it will not be LF DSET but a full-ranghe SE, still the OPT might be changed ....

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

04-15-2011

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JJ Triode
Posts 99
Joined on 09-12-2007

Post #:	37
Post ID:	16046
Reply to:	16045

Sounds like PSEP (Parallel Single-ended Pentode)

To get 17W per KT88 in SE, I think it must be pentode or ultralinear operation. Triode-connected in A1, I think a KT88 can only make 10-11W max (plated dissipation limit is 44W.) So it probably uses feedback, but that is still not automatically a bad thing. User-adjustable feedback is a lot like user-adjustable plate loading; it affects distortion and damping factor in a similar way, hence your TTH also.

04-15-2011

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	38
Post ID:	16051
Reply to:	16046

Class A1 SE Pentode?

Someone please jog my memory by naming some previous true Class A1 SE pentode amps, since I can't for the life of me recall any. This might actually work pretty well if targeted for LF! Adjustable "feedback" could help tons with Z matching, a very nice tool for dialing in LF. I think most of us take lots of distortion for granted at LF. How cool would it be to be able to choose by ear? If it uses KT88, it should be adaptable for EL34, as well, for more "neutral" sound.

What are drivers, again? 2 or 3 stage? I need to look it up. Anyway, what a cool idea. Sounds like it should have been around already...

Best regards,
Paul S

04-15-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	40
Post ID:	16053
Reply to:	16045

Paralleling 6421215685 tubes

....may work here as small dis-sincronizations in pumping the current should not matter at ULF.
But how much God would be in 121478521785 parallel KT2318 tubes?
1/121478521785?
One, max two big tubes is still more appealing to me, don't ask me why.
I'm trying to push the 833A idea until some logical "on paper" design--I have an A2 spice model
finally (Stephie you are the girl!Thank you!) and lifting both Romy's 2-stage and one transformer
constraints will try to come up with some idea. I take Paul's word for EL34 neutrality.

Cheers,
Jarek
STACORE

04-16-2011

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	42
Post ID:	16056
Reply to:	16055

11V Direct Heater

N-Set, this tube does look interesting, in that it mostly fits your stated theoretical desiderata, save the true triode part. It will also be interesting to see how you swing the drive voltage in only one stage, and how you will from there arrange an acceptable output impedance.

Like I keep saying, I have no idea how to tame self-effects with all the giant parts and high voltages/EMF in the same box. The scatter from an amp like this would light a grounded flourescent bulb at 30 paces, and the rails would support the MTA.

As you might have guessed already, I've been seriously zapped before, so this certainly enters into my thinking on this subject. This said, and more to the point here, I have no experience that suggests to me at this point that this approach would in the end bear better sonic fruit than a more conventional design.

AC heater, anyone?

Best regards,
Paul S

04-16-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	43
Post ID:	16057
Reply to:	16056

Can it be it?

Paul, I know NOTHING about pentodes. I looked at the curves:
at 1500V/300mA/-85V loaded with 3.2k will give a whooping 190W
with +/-85Vmax swing, staying in A1. At 2.4k this drops to 155W.
G2 @500V, eating 50mA of current(!)
But the linearity...???? The knee seems soft but the data are very sparse.

I'm wondering if 6E5P, choke loaded, DC coupled can drive it?
The is theoretically no grid current and the capacitances at LF do not matter
(anyway it's a HF tube)?
Then it would be a straight, DC coupled 2 stage
amp, as Romy wanted. The supply will be a but complicated: stacked 200V and 1500V
Seems people are trying it (although with a limited power in this case):

http://www.diyaudio.com/forums/tubes-valves/183163-gu-81m-tube-amp-schematics-3.html

I'm trying to see if this little monster has any following in audio...

I think I have a DC supply to power the heaters, they seem similar to 304TL.

Cheers,
Jarek
STACORE

04-16-2011

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haralanov

Bulgaria
Posts 130
Joined on 05-20-2008

Post #:	44
Post ID:	16058
Reply to:	16057

GU81M

N-set, a friend of mine built an amp with this monstrous USSR tube. It has 3 stages and the GU81M is driven by 6C33C.

ampa na ra4ev.jpg

Within context of driving mid or high sensitivity bass drivers, this is all you need. In comparison, his previous SET with 6C33C sounds like a toy. There is only one tube that can beat GU81M in terms of dynamics and effortlessness in the bass octaves and it is GM100.

"If you can't explain it simply, you don't understand it well enough." -A.E.

04-16-2011

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Romy the Cat

Boston, MA
Posts 10,160
Joined on 05-28-2004

Post #:	47
Post ID:	16062
Reply to:	16058

GU/GM vs. 6C33C

haralanov wrote:
N-set, a friend of mine built an amp with this monstrous USSR tube. It has 3 stages and the GU81M is driven by 6C33C. Within context of driving mid or high sensitivity bass drivers, this is all you need. In comparison, his previous SET with 6C33C sounds like a toy. There is only one tube that can beat GU81M in terms of dynamics and effortlessness in the bass octaves and it is GM100.

In comparison to GU/GM tubes, SETs with 6C33C sounds like a toy? Haralanov, I would challenge this observation. I would challenge it not becomes I am familiar with GU/GM to well and not because I am 6C33C user as suffer from “insulted ownership”. I would challenge this observation because there is nothing in larger tubes that would be superior to 6C33C in terms of “dynamics and effortlessness”.

What I would like to offer to your friend or to you is to expend on your findings. I do not refuse what you guys say but I challenge. I did see a few times what people report that bigger tubes have “more dynamics and effortlessness” but it really it is all about the fact that more powerful tubes sit deeper in A1 class or that power powers tube has better drivers that drive them. I do not believe that GU/GM tube is more dynamic then 6C33C if both tubes are driven respectfully identical and drive the appropriate for own power sensitivity. In fact, I think that in respectful to own power operation 6C33C will be MORE dynamic then GU/GM (lower plate R, less wire in OPT...).

Sure, we are not sitting in the same room and exchange opinion about the same Sound and it is very difficult to find any common denominators… Still I feel that what your friend reports might be incorrect.

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

04-16-2011

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	48
Post ID:	16064
Reply to:	16057

Bee's Knees

N-set, I give lip service and a sort of generic consideration to plate curves, but in the end I am not wholly secure in my understanding of this information as it relates to sound with a given tube in a given circuit. My usual basic tactic is to ask rather less of the tube than it might give, in terms of plate dissipation, keeping one eye on the curves. But I agree, I can't say that these curves look like something you'd generally choose for an output tube for an audio band amp.

But you've waited this long already; so I suppose that you are not going to spring into action as a result of some internet chatter on an "underground" DIY site. As we frequently observe around here, plenty gets done as DIY just to do it. OTOH, to survive building an amp like this should bring bragging rights, in itself!

Best regards,
Paul S

04-17-2011

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N-set
Gdansk, Poland
Posts 617
Joined on 01-07-2006

Post #:	49
Post ID:	16066
Reply to:	16064

GU81 considerations

Paul, don't get me wrong--normally I'm not choosing a tube by the power, but this situation is somehow special.
There are very few tubes which have the right electrical parameters (gm, mu, power, etc) to start with. In the
small tubes word one can glaze hours on the curves, trace them himself and then choose to whatever
factors. Here we have what we have. Few +/- aplicable tubes and the curves traced for class B-C opertion.
It's all a gamble. BTW, I've located a Dutch guy at DIYAudio who has been building around GU81M, and monsters like GU5b.

GU81M curves do not look that disastrous: observe that the knee (esp. 0V) seems softer.
I'm wondering how to drive it in A1. Will it need power?
I'd like a very linear triode with mu=30-33 at least and ideally 20W plate diss. SV572-30? 812A? 2x6E5P??
I'm wondering why Romy in his wishlist prohibited paralled
drivers but would happily accept paralled output tubes???

Below is something which may be breadboardable with a single 6E5P
(provided my power tranny can stand the current and I teleport 3000km).
I have no idea how to power the screen properly (500V wrt the cathode, 50mA!).
A separate supply with VR string to give 500V? Now is the RC circuit (no idea how to get C from the data).

With the 833 A2 idea I'm a bit stuck: i've spiced 6E5P -> EL34 (triode) -> 10:1 -> 833 and
EL34 will not give enough swing (the main limiting factor is 425V screen max, plate can stand 800V)

Cheers,
Jarek
STACORE

04-17-2011

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Paul S
San Diego, California, USA
Posts 2,658
Joined on 10-12-2006

Post #:	50
Post ID:	16074
Reply to:	16066

Triode 3-Stage

N-set, starting from reasonable input, the 6E5P can swing some serious voltage, and Romy also sings its praises in terms of sound. Maybe sim that, running it in its safe zone to a 6C33C. From there, you have all the power you'd want to drive -- whatever. Basically, I'm supposing that linear operation, in practice, is likely to work out better than a pushed 2-stage, given the working constraints of SET power in the first place...

I have no personal experience with the 6E5P, and so I don't know how well it holds its values over time; but I can say that the 6C33C will pass on what is fed to it, as long as you can keep it tuned; basically, "fixed bias" needs to be monitored and adjustable.

How does the Dutch guy consider/deal with self/parasitic noise? Maybe figure on all-shielded hook-up wire bled via a dedicated ground... Also, I recently saw (then promptly forgot about...) a "new" composite shielding material that "offers the best of steel, aluminum and Mu metal", yet it can be bent, etc., even grounded.

Did you find those caps yet?

Please correct me if I'm wrong, but it appears to me that you are in love with "transformers". Maybe parallel tubes are a way to boost power and drop output impedance at the same time, versus bigger tranny, with its own ramifications, etc. No Free Lunch...

Best regards,
Paul S

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»	New	More power from Melquiades? More powerful tube?..	A new Icon Audio's MB81 Mono Blocks...	Melquiades Amplifier Forum	19	249792	09-01-2007
»	New	NAT Audio Magna -160 Watts of Single-Ended Class A..	The KR Audio ways....	Audio Discussions Forum	5	73177	11-12-2007
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