GoodSoundClub - Romy the Cat's Audio Site - Keep the eyes on the ball.

03-23-2011

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IslandPink
Posts 18
Joined on 02-08-2005

Post #:	22
Post ID:	15833
Reply to:	15830

Zero-crossing ?

There's no zero-crossing with A2 .
833 or equivalent are a good choice for this extreme project and bass performance is excellent, I have heard 833 SE briefly and it has great authority.
The driver would best be some sort of small/medium output valve driving 833 via a step-down interstage. Then the gain of the 833 works in your favour . Various people have done this .
The problem remains the huge size and power consumption of the whole amp , and the core size and gapping required to get sufficient inductance down to 5-10Hz ( for ULF ) while also being gapped for eg.300ma to cover 2x 833 . I'm sure Bud would know how to do this as he works in the power transformer game . He can give you the bad news about how big it will be ;o)

MJ

03-23-2011

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Romy the Cat

Boston, MA
Posts 10,155
Joined on 05-28-2004

Post #:	23
Post ID:	15834
Reply to:	15833

The grand scale of the concept.

What you guys are missing is a grand scale of the concept. You are talking about voltages, implementation, electric chairs and the rest of irrelevant crap but I am talking about the pure inspiration from the concept. No one runs to solder anything. If they do then I do not mind somebody got blown away by a 5kV capacitor – I hope it will be a republican. The point is not about a factual amplifier but the concept of getting bass that was not heard before.

I am sure not a lot of you hear sound of more or less proper playback with “interestingly” reproduced upper or midbass. I would not even mention the lower bass. However if we mention it then I would like to point out that we do not have any tool to amplifier bass except PP SS amps that are not truly able to do bass properly due to crossover and thermodynamic distortions. I am not talking about the fact that we have no speakers or very few speakers that are able to go for proper bass.

If some of you still feel that you know something about bass then let me ask you: how many of you even heard a playback with “interestingly” reproduced region of 10-20Hz by whatever acoustic system it was and driven by a single ended, class A1 amplification free from SS thermodynamic distortions? I do not think I will hear a lot of rise head and you will not see my hand raised as well. But I would like to hear it.

The concept is that I would l would like to hear let say DC-coupled Milq with 8 parallel 6C33C driving 1.5:1 out transformer gaped 2.5A with core able to get 2Hz of first clip at 160W. I just would like to hear what it is, even that that I intellectually understand that sub 20Hz is very problematically distorted on the recordings. Still, I would like to hear it as I would like to get a reference of what is possible by mean of audio. Sure I do not build anything like this but I would like to say, and no one else does to the best of my knowledge but I would like to declare that I have interest in it. In one way or other I would be pushing the concept, not implementation but the concept. Some of my observations in the neighboring fields suggest that there is a lot of to fish in the ULF world if to use it creatively. Who knows, perhaps another day someone would be inspired with the idea, knock in my door and will drag into my room a refrigeration-size amplifier with a pair of fire extinguisher built-in on the chassis… If do not dream about it then no one will knock at your door….

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

03-24-2011

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

Post #:	24
Post ID:	15835
Reply to:	15833

Zero inspiration bias

Some people bias 833 at 0V. Some in A1 but to get teh stated power
it must go into A2. Do you or anyone have
normal plate curves for 833 instead of that multiamp
idiocy usually published? Say up to 200mA. Same for 304tl.
Outpur tranny--this is the function of 833's big
internal resistance. So I'd still lean towards e.g. 304tl.
More current efficient, the parellel structure some purist bark at
should not matter at bass, if it matters at all in any sense.
I think OT is an easy things here. Just the iunsulation.
Any good kV winder can do it, once you calculate the tranny.

Inspiration--there must be a balance between inspiration
and technicalities. One without the other is useless.
I'm much better in vocabulasing technicalities
unfortunately...The Voice Of God would be my inspiration!
I don't need more words.

Cheers,
Jarek
STACORE

03-26-2011

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

Post #:	25
Post ID:	15862
Reply to:	15835

Drum'n'bass party

This thread has triggered some old stupid sentiments. Feel free to remove this post
if irrelevant. I've been thinking how to rationalize my old design in the present context
and make it less idiotic.

First, know the enemy. I don't know the enemy. I assume the bass arrays are very low impedance, 0.5R and require
good controll (damping factor). This should narrow down the tube. Perhaps I'm wrong, but
833/GU-48 does not too look good on paper with their high Rp to achieve good damping,
so I'd stick with 304tl. Apart from Rp at 1.5k level it has one more interesting
degree of freedome to play with: 304th variant with highre Rp if needed.
Biased at 2500V/-250V/120mA and loaded with 7k or so, 304tl should give around
100W, perhaps 120W with a reasonable (?) damping factor, if I'm not mistaken.
The good point is that 304tl must operate at or close to max, otherwoise the tube life is reduced.
5Hz would require 50H primary ind. Doable at 150mA with AMCC800A cores,
1mm gapped, I think 70H too.
To drive I'd go for something non DHT not to complicate:
6E5P DC to, say, EL34 triode connected@400V/60mA and then 1.5:1 stepdown.
Stepdown with 80-100H@60mA primary should be doable too. This should drive 304tl into mild A2 if needed.
PS: I went for the bridge due to the trafo constraints (I had too small lamination), but now I'd do
3kV-0-3kV trafo then 872A FW. For the input and the driver: stacked Romy style supply with mega uF etc.
The most complication is fixed bias...as I see it, due o the DC, each stage would require it's own bias
supply...pain in the ass
THis is something I'd try at this moment, but again--I don't know the enemy, so I'm blind.

Cheers,
Jarek
STACORE

03-26-2011

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Romy the Cat

Boston, MA
Posts 10,155
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
STACORE

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
STACORE

03-30-2011

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Romy the Cat

Boston, MA
Posts 10,155
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
STACORE

03-31-2011

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Romy the Cat

Boston, MA
Posts 10,155
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
STACORE

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 10,155
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 2,656
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

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