Thorsten's Valve Output Stage with TDA1541DAC

[juancho]

Has anyone tried Thorsten's circuit for a valve ouput stage with the TDA1541 dac?

I'm interested how this worked generally and also whether anyone has used the TDA1541 in nos mode with this output stage.
Many thanks
David

 

[paba]

Can you post a circuit,
I've only read text scattered invarious places/forums.
Thanks
paba

 

[juancho]

Hi,
here's the link to the circuit.

http://www.fortunecity.com/rivendel...fda/vasfda.html


David

 

[lpm76]

The link didn't work for me, but this does:

http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html

 

[Andypairo]

I have built it some time ago thinking to use it in my next DAC but so far I haven't assembled the DAC yet.... first I have to complete the MOX x-over... a tube preamp and to properly settle in my new house

Cheers

Andrea - starts thinking that getting married is a real challenge, especially timewise

 

[paba]

That's oldish material I've read T's posts in various places where he updates this circuit.

thanks anyway, maybe he will reply.

 

[Andypairo]

That's oldish material I've read T's posts in various places where he updates this circuit.

thanks anyway, maybe he will reply.

If you can post some links for these updates it could be very useful....

Cheers

Andrea

 

[paba]

That's the problem, it is text spread out in several forums and I don't have that collected. That's why I was asking in the first place, in case it did exist in one place updated.

sorry
paba

 

[ThorstenL]

Konnichiwa,

Okay, quick & painless.

I have published a few circuits.

1) The one from the Valve Article - also linked in post #4 which is actually not a circuit as such but a blueprint meant to be adapted by the individual builder.

2) The one I used in the final accounting with my "Adagio" TDA1541 DAC:

http://www.fortunecity.com/rivendell/xentar/1179/projects/adagio/Adagio.html

3) The one specifically aimed at the TDA1545 (and no other) which has been ripped off all over the net without propper attribution to me (which really pi...es me off) for example here:

http://www.ptsoundlab.com/secnumerique/cd/philips723/etagelampes.htm

(The siteowner also copied several other of my schematics - not even having the decency to re-draw them - again completely without attribution!!!)

The design originated in a "lets hotrod the Philips CD723" Discussion on a German board.

A "non-oversampling" digression was discussed here, this might be a neat upgrade for Yeo's TDA1545 DAC Board....

http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=52708

4) The "latest" TDA1541 Analogue stage as here:

An externally hosted image should be here but it was not working when we last tested it.

There have also been some discussions on circuits for the TDA1543, but they are posted in my Yahoo Group and thus not directly accessible....

I hope this helps.

Sayonara

 

[juancho]

Hiya,
Thanks for the reply. The 'latest' tda 1541 circuit you post below, is that sonically better or similar but with a much lower component count?
Thanks
David

 

[ThorstenL]

Konnichiwa,

Thanks for the reply. The 'latest' tda 1541 circuit you post below, is that sonically better or similar but with a much lower component count?

It is a very different circuit, aimed a sonic purity, with no serious consideration given to load drive ability (eg no long cables please) output levels, low measured distortion and the like.

Sayonara

 

[Andypairo]

What if I can only get a 120 or 200 H choke? Must play with B+?

Cheers

Andrea

 

[Bricolo]

I'm no tube expert at all, but are you really talking about 200 Henries?!!
H, no mH or uH?

 

[ThorstenL]

Konnichwa,

What if I can only get a 120 or 200 H choke? Must play with B+?

Not really. Adjust +B to give around 70V on the ANode, depending on choke DCR. Otherwise more L will be a good choice, IF the HF behaviour of the choke is good (in other words if it is wound as anode loading choke).

Sayonara

 

[ThorstenL]

Konnichiwa,

I'm no tube expert at all, but are you really talking about 200 Henries?!! H, no mH or uH?

Yes, of course. What else? The Anode impedance of an ECC88 is around 3K. With a 200H choke this leads to a -3db point for the analogue stage of around 3.4Hz purely from the LR interaction, of course distortion will go up at higher frequencies from the elleiptical loadline.

Sayonara

 

[Bricolo]

It's just that I didn't know that such high values existed. 200H sounds to me like 200F, IWO: huge!

 

[ThorstenL]

Konnichiwa,

It's just that I didn't know that such high values existed. 200H sounds to me like 200F, IWO: huge!

Tango carries the TC160-15W which is a choke that offers 160H/15mA or 40H/30mA. It is quite small actually. As you can see, with falling current requirements the inductance of the choke for a given core goes up by the square of the current reduction (this is admittedly a little approximate but illustrates the point)....

Sayonara

 

[Andypairo]

I've searched around and the prices I found for this Tango choke is more than 100$/pc... this is a little out of budget for me

Since as alternative is suggested a current source I think I'll go for that

Do you suggest a tube or a solid state CCS?

Cheers

Andrea

 

[ThorstenL]

Konnichiwa,

Since as alternative is suggested a current source I think I'll go for that

Do you suggest a tube or a solid state CCS?

Specifically intended with the +B of 100V is the IXYS HV Chip CCS.

Otherwise design your own as you like, making sure of the 70-75V anode voltage for the ECC88/6DJ8/6922/7308.

Sayonara

 

[Andypairo]

Just a quick one...

Kuei, since a pair of Amplimo showed up in the trading post and I already have some E182CC, how would you rate this stage vs the original Adagio?

Cheers

Andrea