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Buffalo II & transformers

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Terry - I just have to say, on a personal level I greatly respect your work and experience. Your reputation precedes you. Don't take my comments as critical of you in any way. I hardly have room to say anything there. I respect you immensely. This is just part of the learning process for me. I pride myself in trying to remain objective while maintaining a clear sense of individuality. :D I hope that does not come off as rude.
 
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I agree the phases need to be summed. My personal opinion is the very best place to sum these signals (at least for hi-fi) is at the loudspeaker. My ideal is to keep things fully symmetrical until that point. This of course does not hold true where cases where fidelity is not the first concern (in many cases raw power and reliability are for more important).

Yes agreed. I prefer fully balanced -> spkrs where possible.

Unfortunately not many (other) hi fi systems are balanced hence the DAC
phase sum requirement.

Terry - I just have to say, on a personal level
snipped
:D I hope that does not come off as rude.

WRT rude, not at all.

Thanks for the comments they are probably a bit OTT. I'm no design genius,
I'm just 'in the trenches' like everyone else here trying to learn what I can
and share where appropriate.

cheers

T
 
I was just making the point that this is in every respect an active output stage. Just with a transformer in front of it. :)

Clear Russ ,but as there is always an active stage after..
put in the active in the dac we can use as preamp out ?

balanced not so usefull for tubehead....

PS
looking at commercial stuff there is a lot of new CD/pre, Dac/pre,pre/dac , like Audiolab,Onkyo and so on
 
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The topic is "Buffalo II and transformers." I am sure that initially this was about using transformers in voltage mode? But I think it still fits topic wise.

But if we are exploring all various possibilities is using the Sabre DAC (and that means the topic has influences even beyond Buffalo DAC), then why not explore how txs allows for low Z I/V, which as far as I can tell will invariably means voltage gain afterward (and as has been pointed out, even achieving 2V RMS target will need gain after that).

So I vote for a liberal exchange of views. :)

One thing for sure, the Sabre DAC is more permeable to many possibilities than any other DAC.

Cheers, Joe R.
 
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Joe,

I was not saying that the ZF trafo discussion was off topic. It certainly is. In fact at the moment if I were going to play with a trafo that would most likely be the kind of solution I would choose. :cool:

I was saying to remember that this is a TPA thread and discussion will be limited to TPA gear (not Oppo etc). Those things can be discussed elsewhere.

I have a pretty high tolerance for topic tangents, I only expect people to remember that this is our vendor area,. I have seen people try to promote some other product or agenda (I am not saying you were) and I won't have any of that here.

So while I welcome the liberal exchange of ideas, kindly limit the scope to how they directly pertain to TPA gear please.

Cheers!
Russ
 
Is it a problem to lower the resistance of transformer windings? (in a passive way)
What input impedance i/v stage (opamp or discrete) can have?

What problem? There is only a problem if you don't like the result. :)

All I was saying is that for me I prefer the lowest Z ouput stage I can practically manage. This is based on my years listening to the thing.
 
Clear Russ ,but as there is always an active stage after..
put in the active in the dac we can use as preamp out ?

balanced not so usefull for tubehead....

PS
looking at commercial stuff there is a lot of new CD/pre, Dac/pre,pre/dac , like Audiolab,Onkyo and so on

Basically because it has volume control Buffalo 3 is a DAC/Preamp right out of the gate. Add a Legato or IVY-III and you get some voltage gain and lower output impedance and BAL/SE conversion. You could also use a transformer output directly where you would use one of those two. With or without gain.

The truth is that for standard stereo speaker hi-fi use the only active stage you really *need* after the DAC is a power amplifier. :)

In my case I prefer to use an active I/V output stage before the power amplifier.

It all comes down to what makes you happy.

Cheers!
Russ
 
Hi Russ

I understand. But may I point out that with using txs with the Oppo, I have advised and indeed sold transformers to Buffalo users in both Asia (mainly Malaysia and Japan) and Europe. So there is sometimes a bit of cross-fertilizing going on. Things done to the Oppo translates directly the Buffalo II, and you may not be aware that I have actually recommended buying your DAC on the basis of the results I've gotten with the Oppo - which is less DIY friendly.

Cheers, Joe R.
 
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Joined 2009
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Hi Russ

I understand. But may I point out that with using txs with the Oppo, I have advised and indeed sold transformers to Buffalo users in both Asia (mainly Malaysia and Japan) and Europe. So there is sometimes a bit of cross-fertilizing going on. Things done to the Oppo translates directly the Buffalo II, and you may not be aware that I have actually recommended buying your DAC on the basis of the results I've gotten with the Oppo - which is less DIY friendly.

Cheers, Joe R.

Actually I did the same: already started with Oppo, and then bought Buffalo. The advantage with Oppo is that one have quite all together in the same box. But is enough difficult to work with that big analogue board, which anyway is very bad designed...
Buffalo will be for me the next step (the better one...)
 
If using a pair of Buffalo2's in dual mono, what should the resistor values be with a tube stage after the transformer?

JD

I still think somebody should try this with a Sabre DAC using Tubes.

IV-Tube.gif


Normally Tubes are only good for voltage DACs, but use a transformer like this and you will have a Tube I/V stage - and it is the Sabre DAC that makes it possible - offset current = 8mA (I wouldn't do this with any other DAC I could think of). It can be pulled all the way to ground on the Primary and the Secondary grounded - and just input to the grid of your favourite Tube - and away you go.

Somebody should try it - requires gain about 50.

Cheers, Joe R.
 
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I'm thinking in terms of using a tube stage with gain after the transformer as in Joes schematic and keeping the the two reisitor low. His schematic shows a pair of 3r to ground on the primary for an output of the transformer to 30mv.
My question is would those resistors be the same value or a different value if using a dual mono rather than the single one in the schematic. (just curious)


Another thought I had was just running the Dal Mono Buff2's into a transformer with it's secondary loaded (2v) then into a 6H30 driver / buffer (with no gain).

JD

I would install a 100K POT and find a sweet spot to your taste.
After you find sweet spot, I would swap to the fixed value.

Loading transformer makes huge difference on its sound. The best is subjective and up to your taste.;)
 
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JD,
I agree with fulken's suggestion but if you don't want to do this, you can use 1.5ohm resistors since you are running dual mono. You should still get 30mV if you're using a 1:1.

No, you will get 15mV RMS. Each phase of ES9018 will produce 1V RMS. Use Ohm's Law calculation:

2*(1.5/195) = 0.015384

I think 1R would be low enough to claim proper current mode, but the subsequent gain would need to be very high and low noise. That's the other consideration if using a tube gain stage, noise. If you want 2V RMS final out, then gain = 200.

Cheers, Joe R.
 
Joe, JD is running dual mono. He has 8 Dacs per channel. Output impedance should be half the 195 you used in your calculation. Cheers DF

OK, gotcha on that one. That will indeed double up.

But something came to mind, that means the 195R gets halved, but also means that a lower Z is required for same 'level' of current mode, as the ratio between that Z and the load Z defines current mode. In theory it should be infinite and that means the ES9018 should only see its own Z and no more. But real world...? I have used 3R (stereo) and 1R5 (8 channel) and it works well - but didn't use tubes and no tx as I had a differential input with a gain of about 70 and very low noise.

But tx is a good idea when you have a single-ended input tube stage. I haven't done it, but a friend/client is soon to try.

Cheers, Joe R.
 
Just wanted to say thank you to everyone in this thread, it's been a great resource to me. :) I'm currently building my Buffalo III and decided to go with Sowter 3603 transformers with the OCC wire option. There will be a build thread for it soon, but this is where I'm at so far:

DSC03934.jpg
 
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