tube output for Playstation 1

[pebmrb]

I am hoping to get some recommendations on a tube output stage for my Sony Playstation 1 that will get the output up to the level of a normal CD player.I am currently using a tube stage presented by Thorsten Loesch in the document titled:Thermionic valve analog stages for digital audio.I am extremely pleased with the sound I am getting from this and hesitate to change it,but I simply need the output up to a higher level to drive my 2 watt SET EL84 amp.I initially used his circuit without the low pass filter in an effort to get maximum output,but have recently added the filter and got a marked improvement in sound quality,but at the expense of a bit more output.I would like to retain the filter,but get the gain up a bit.Any suggestions?Modify this circuit?Suggest another?Add another gain stage?The chassis is completely DIY,so I have flexibility to do whatever I want .Enclosed is the circuit I am using(using half the balanced lo pass filter).I did post this in the Playstation forum but didn't get quite the response I hoped.
Thanks
Paul

[chanmix51]

Hello Pebmrb,

Here is an output stage we have designed primarily for the TDA1543 DAC. It has a very low input impedance (around 0.1Ω) over all the audio bandwidth and outputs 2vp. I use it connected directly to my EL84 pp amplifier.

Here are 2 versions of this stage the hybrid and full tube one :


Enjoy.
greg

[rsdio]

Originally Posted by chanmix51

Here is an output stage we have designed primarily for the TDA1543 DAC. It has a very low input impedance (around 0.1Ω) over all the audio bandwidth and outputs 2vp. I use it connected directly to my EL84 pp amplifier.

The PS1 should have voltage output, so I don't see how an I/V converter would be a good choice (unless there is a current-output DAC in the PS1 and the OP wants to cut traces on the PS1 PCB). Am I missing something?

[pebmrb]

Thanks for the circuits Greg.Very nice.Yes the PS1 DAC is an AKM4309 I believe,
which is voltage output.
For a quick test,I put in a lens cleaning CD that has a continuous test tone.My PS1 tube stage put out about 100mv RMS vs. 300mv from my stock NAD.I assume I would need a gain of about 3 then to get it to a comparable output.?I prefer to direct couple to the DAC which has DC offset about 2.5v.Also would prefer to avoid feedback if possible.
Thanks for the help.
Paul

[rsdio]

Originally Posted by pebmrb

My PS1 tube stage put out about 100mv RMS vs. 300mv from my stock NAD.I assume I would need a gain of about 3 then to get it to a comparable output.?

Yep, gain would need to be 9.5 dB (or about 10 dB).

I prefer to direct couple to the DAC which has DC offset about 2.5v.Also would prefer to avoid feedback if possible.

Feedback turns a nonlinear device into a nearly linear system. Unless you like distortion, you'll want reasonable feedback. The thing to avoid is designing for an open loop gain of only 10 dB when you want 10 dB of closed loop gain. Instead, you should use a gain device with well over 10 dB of open loop gain, then use the feedback to tame this into a very linear 9.5 dB with minimal distortion and flat frequency response.

[pebmrb]

rsdio
Thanks for the reply.
I love distortion........in my guitar amp.But certainly not in my CD player!Anyway,I guess I was just repeating something I read somewhere about the evils of feedback,but that's a bit off topic.I seen some circuits on the Lampizator site that might work.Anyone have experience with those?

[rsdio]

Originally Posted by pebmrb

rsdio
Thanks for the reply.
I love distortion........in my guitar amp.But certainly not in my CD player!Anyway,I guess I was just repeating something I read somewhere about the evils of feedback,but that's a bit off topic.

I'm glad you took my comment well. I certainly did not intend to start an off-topic discussion about feedback. However, I will try to briefly summarize. An amplifier without feedback is like driving with your eyes closed. As someone else said, every area of engineering utilized feedback without questioning its merits and necessity - only in audio is there this ill-informed idea that all feedback is bad. But, if you read Bob Cordell's amplifier book, or many of the other comments on diyAudio, you'll find that feedback can be used to cover a bad amplifier design, but it's really the bad design at fault, not the feedback. Also, some mistaken papers with bad math have been published in years past, but somehow the anti-feedback sentiment stuck around.

I did drop a good clue: The gain section inside the feedback should have a lot more gain than you want for the overall system, and then it should work well. There are also concerns about frequency response and phase shift, but they're rather difficult to summarize in a few sentences.

I'd recommend seeking out a tube preamp circuit somewhere. You don't need a full power amplifier, and you don't need an I/V converter, so a preamp is probably the most appropriate circuit for you.

P.S. You should attach photos once you've finally got this thing built! I have old PS1 and PS2 consoles that I boxed up when I got my PS3, but it might be fun to break them out.

I seen some circuits on the Lampizator site that might work.Anyone have experience with those?

Can you post links to those circuits? The Lampizator site is not organized very well, or at least I couldn't find anything obvious right away. But, if the circuit you found is designed to take voltage in and deliver voltage out, with moderate gain in a preamp setup, then I think you might be on the right track.

[pebmrb]

These two Lampizator circuits are pretty basic and appear like they may work well,although one of them may have too much gain as is.

http://lampizator.eu/UPGRADE/new%20AF%206H6P.mdi
And
http://lampizator.eu/UPGRADE/6H6P_SRPP.MDI

My CD player has been done for a few months now.It has the 6DJ8 cathode follower output stage shown above,but recently I have decided to change or modify the output stage to get the output up to the norm.But I want to make sure the increased gain isn't at the expense of sound quality.This thing sounds great as is.
Enclosed is a pic of my CD player.There is a PS1 model SCPH1001 in there.
Thanks
Paul