TDA1541A I/V conversion

Finally got my CD Pro2m transport working with my TDA1541A double crown homebrew DAC. This currently has passive I/V followed by Thorstens ECC88 valve output stage.

The CD player sounds great, however, I always want more!! I have heard people say that there are better ways of carrying out I/V conversion than the simple resistor arrangement and am currently contemplating the use of Peda Rogic's design uaing a 2SK170 and AD844, possibly still followed by a valve stage. There are also a few designs using discrete transistors such as IRF610's floating around.

Does anyone have any experience of different designs?

Cheers,
Ian

Ive got something you might be interested in trying. PM me

Hi
Have sent PM

Cheers
Ian

[leo:)]

I've tried a few I/V stages with this dac, Pedja's AD844 common base is one of my current favourites, I'm going to try out the Pass D1 next

I have a Pass D1 and psu, constructed 1 month ago Ive nothing to do with it as Ive gone in another direction. Thats the info I had for Ian!

I was thinking of trying Pedja's design but taking the output after the first opamp (pin5) and feed that into a triode output stage.

The other alternative is the D1 design. The problem being that the PSU's are quite different and I don't want to build both. Secondly the Pedja design uses 78 series regulators which I believe are not so good. I suppose I could use LM317 and LM337 regs, though I had also considered super-regs (expensive).

The CDplayer as it stands uses a CDpro2m with separate powersupplies for the display/controller and for the 5v and 9v supply. The DAC is homebuilt around TDA1541A double crown with super regs for the +5V, -5V and -15V. I/V conversion is passive and feeds Thorstens ECC88 triode output stage.

All the transformers, rectifiers and smoothing caps are in a seperate box (like Naim).

I am pretty pleased with the player so far, but would like to take it as far as I can.

Cheers,

Ian

[leo:)]

Hi Ian,

Well I'd try Pedja's AD844 as standard first, just use 78 regs etc to start with, it gives you an idea of the sound and if you think it has potential then you can upgrade the regulation etc later.
Even the 78 series regs sound ok seeing as though all the supplys are separate.
I also tried passive I/V with Thorstens ECC88 output stage, its a nice sounding circuit, quite a bit different to the AD844 common base.
You can try what you like as a buffer on the AD844's output, valves should be interesting

Hi Leo,

Good point about building the basic version of Pedja's I/V circuit, I guess it gives me the possibility of solidstate output or valve. When you built your version of the circuit did you change the regulation?

With regard to Thorstens valve output stage there are 2 versions hat I am aware of, the first being an SRPP circuit on his Thunderstone Audio website. The second I found on diyaudio.com and this uses anode chokes. I built the SRPP version, which one did you try?

Cheers,

Ian

[leo:)]

Hi Ian,

Yes, I did try better regulation, mainly ALW super regs with a VBE replacing the pre reg, results was very good, I've had to go back to normal regulation until I can find a better case.
The TDA1541 dac has been put on the back burner for a while until I've finished faffing about with a PCM1794 dac I recently built

The valve output stage I tried was also SRPP with Bugle boy valves.
I tried Lesha's 6C45PI circuit too, both are decent with the 6C45PI sounding more forward and brighter.
The usual problem for me was suitable cases, both circuits was hard wired onto a wooden board for testing.
Theres so many things you can try on the TDA1541 its never ending

Cheers,
Leo

Hi Leo

I have also used VBE's upstream of the ALW super regs, the circuits being based around IRF610 and IRF9610 depending on whether the regs were positive or negative. I left the pretracking reg on the ALW board.

I had also wondered about using Lesha's 6C45 design, however, I find the DAC with thorsten SRPP quite bright enough and so will leave alone.

Do you think the output of the AD844 (pin 5) could be fed straight into Thorstens SRPP design, or are there better circuits I should consider?

One of the main delays I find with all my projects (in particular the CD player) has been making the cases. I have just taken delivery of another pile aluminium sheet and channel from which i need to build the CD player PSU. If I get a chance I will take some photos and post them, see what people think.

Cheers,

Ian