DIY tube output in DAC - needs advice...

[Andypairo]

Hello,
thank you for your insight.

About my supply problem, is 230-235 V too much for B+ or are these acceptable values? the datasheet of the ECC88 says that the maximum Va for each section is 130V but I'm not sure I'm looking at the right value....

Cheers

Andrea

 

[fdegrove]

Hi,

Can I just replace the tube of above schematic with 6N1P (I have loads of them but nil ECC88 or 6N23P)?

Both types are slightly different_depending on the sources you want to believe_the 6N1P needs higher heater current: 600 to 650 mA iso the 310 to 335 mA required for the 6N23P.

Also the mu of the 6N1P is a little higher at 35 compared to 34 for the 6N23P.

The main difference however is the Ra which is 4K4 as opposed to 11K for 6N23P and 6N1P respectively.
Hence transconductance values are also different for both: 3.2 as opposed to 12.5.

The net result would be a higher Zout for the 6N1P but I don't consider this critical for a DAC output stage.

Cheers,😉

 

[Pedja]

In what application and compared to what other options?

I have compared them to the ICW's, Ampohm and Ansars, with the SCR/Solen types coming out poor seconds compared to these. Between Ansar & ICW the race is less clear cut, it often depends upon the specific position, the Ampohm are solidly encased and are best of all these MKP types I came across.

Tried them like line level coupling and speaker crossover units, and if that matter, never with any significant offset. Compared to the realtivelly widely available stuff of similar price like WIMA, Arcotronics, Siemens, Rifa. And it was just on the pleasant side, though sometimes lacking dynamics of some others.

Pedja

 

[Peter Daniel]

I would advise against Solens, in the past I found them to give sonic problems.

Sayonara

A hard, unpleasant sound. This may be very well a result of the microphonic behaviour of these capacitors, just sweep one with a nice high level sinewave while applying a few volt bias....

Interesting, I found them to be among more pleasant ones.

That is interesting. I tried some oder Solens at one time, and didn't like them at all. Yet a friend of mine whose hering abilities I trust, said that in his speakers he tried many caps, yet the Solens were clearly the best for him. Could it be that the older Solens sound different than new production?

The ones I was listening to were somewhat older and I would never touch them again.

 

[fdegrove]

Hi,

Could it be that the older Solens sound different than new production?

IME, yes they do.
I liked them before they became better known...
A few years later I could hardly believe how they'd changed for the worse.

Nowadays the FC series is O.K. but I find the Audyn range alot cheaper and better sounding for the money.

To me this makes the Solens just O.K. for PS apps where I like to use large values of polyprops unavailable elsewhere and even than I'd rather use the ASC PIO caps for high voltages.

I haven't tried the latest batches but neither am I inclined to either...

Cheers,😉

 

[ThorstenL]

Konnichiwa,

About my supply problem, is 230-235 V too much for B+ or are these acceptable values?

I'd say a little high. Simply bump up the resistor values in the supply circuit until the +B settles at around 160V.

Sayonara

 

[argo]

Hi,

.....The main difference however is the Ra which is 4K4 as opposed to 11K for 6N23P and 6N1P respectively.
Hence transconductance values are also different for both: 3.2 as opposed to 12.5.

The net result would be a higher Zout for the 6N1P but I don't consider this critical for a DAC output stage.

Cheers,😉

Frank,

Thank you for your input
Yeah, I was kind of afraid that Zout would be different.
I once simulated SRPP (still don’t now how to calculate Zout for this, hence I use simulator) with 6N1P followed with Mosfet follower and the high pass -3dB point for the total circuit fell into 10kHz to 15kHz range, depending on the resistor values and B+.🙁
So I was left with impression that 6N1P is not suitable tube for SRPP because it’s highish Ra. Is mu-follower any different regarding that?
How do I calculate Zout of mu-follower?
And, what is an adequate Zout for DAC output stage? I think early highpass rolloff can be made an advantage for Non OS DAC?

Argo

 

[fdegrove]

Hi,

So I was left with impression that 6N1P is not suitable tube for SRPP because it’s highish Ra. Is mu-follower any different regarding that?

There's no problem using a 6N1P as SRPP whatsoever, Zout will still be low enough and bandwidth way beyond 20kHz should be obtainable.

The mu-follower is an optimized SRPP to make the top triode a more ideal current source making it track its amplifiaction factor more closely.
This higher gain may not be what you're looking for here however.

In its standard form it still uses the same twin triodes as the SRPP and while it is better in some aspects it's far from perfect, nothing ever is.

To give you an idea about the formulas to use you can check one of our member's excellent site:


THANKS MAARTEN.

For loads of theory on SRPP and derivatives:

TUBECAD.

Cheers,😉

 

[argo]

Hi,

.....To give you an idea about the formulas to use you can check one of our member's excellent site:


THANKS MAARTEN. .......

Cheers,😉

Thanks a bunch! Truly excellent info! And with spreadsheets .

 

[gregaz]

Transformer source?

Hi,

Can someone recommend a source for a transfomer for the tube amp circuits discussed here?

Thank-you,

Fred

 

[simonov]

Hi all,
can I use tube rectifier instead of solid state? I'v played with PSU designer II. RC, LC, RC filter showed promissing results.

Regards 🙂

 

[dutchaudio]

Again old add but never boring 😀

http://www.diyaudio.com/forums/digital-line-level/79452-building-ultimate-nos-dac-using-tda1541a-364.html#post2525747