Some other Source Follower Configurations

[jameshillj]

Hi Patrick,
The "standard" buffer with the k170/j74 (as per the Fig 16B in the "New Frontiers" article) is working well and sounds like "nuthin' at all" (!) - excellent!
The amp changes it's sound quite a bit with extra output series resistance - about 60R for the AKG k701s - bit unexpected.

Is there anything to be gained by fitting IRF610s instead of the IRFP240s? Curious.

Had a better look at the O'Toole regs as per the D1 O/P stage - simpler than initially appearances - could it be be stretched to 400mA and to also feed the buffer?

 

[EUVL]

I don't understand what you are up to.

Why would you try to drive a 60-ohm load with 2SK170/2SJ74 ?
They might just be OK for 2k load.

To drive an AKG701, you need to use the circuit that Steen built -- the DAO follower with LU1014s with Taylor current source.

http://www.diyaudio.com/forums/showthread.php?postid=1592820#post1592820

If in doubts, talk to Steen for details of his implementation.

http://www.diyaudio.com/forums/showthread.php?postid=1603771#post1603771


Patrick

 

[jameshillj]

Sorry Patrick,
I meant that I used the little jfets for the lightspeed buffer and it didn't add any extra colour to the sound.

Modded the original p-p DOA unit to your Taylor version and it is working okay, and simply tried an extra o/p resistor to hear what, if anything, happened with the701s.

The Lightspeed + buffer has a rather different sound to the P/L X2.5 preamp, as you can imagine.

the 610s? have matched sets on sinks from previous h.amp.

the O'Toole supply? improvement to the present R-C-R-C + Cmultiplier?

 

[EUVL]

An additional 60R in series with the AKG701 will of course change the sound (more emphasis on treble) because the impedance of the AKG701 is not constant. Pls google Stereophile AKG 701. They have a full measurement.

Patrick

 

[h_a]

Is there anything to be gained by fitting IRF610s instead of the IRFP240s?

No. They're just used as cascodes, so have little impact on sound overall and 2nd the 240 has a much larger package - you saw that, right? and is therefore easier to cool than the smallish 610.

Matching fets in cascodes is not necessary.

If you want something fancy at this position, you can use Toshiba-Fets or Hitachi-laterals. Or bipolars. But remember to use a large package (not TO-220).

Have fun, Hannes

 

[jackinnj]

If you want something fancy at this position, you can use Toshiba-Fets or Hitachi-laterals. Or bipolars. But remember to use a large package (not TO-220).

The Hitachi's (Renesas) are TO-3P.

 

[steenoe]

the O'Toole supply? improvement to the present R-C-R-C + Cmultiplier?

Hi James.
You can probably make that work, but I am not sure at all, that it is worth the trouble.
The DAO runs absolutely without noise from a simple supply, and I beleive that is the fastest and most responsive psu. If the DAO did need a cleaned up/regulated supply then it would be great to use a shunt regulator like the Toolereg. Nothing wrong to try it out, though.

 

[jameshillj]

Tks Steenoe - will try it, as going to follow up your 'O'Toole -> D1' - interesting.

 

[wrenchone]

Another Source follower type - I'm currently using this in my test preamp ( just back from Burning Amp) as a unity gain line amp. A discrete Darlington with some nice modern bipolars would probably do better than than integrated one I used, though the GE D40K/D41KDarlington series was pretty fast in its day. I have a partially stuffed board in the basement (waiting for some more attention) to see if that is true. The TO-202 packaged Darlington with its long tab made it possible to run it without using a heat sink. The MPF960 uses a TO-92L package, so it is possible to run it with a good deal of bias current without a sink as well.

 

[Luke]

I would be quite keen to make the DAO with Taylor mod, where can you get the parts for this amp? I Can I use a j74 instead of J103 or is it too much voltage?
Does anyone sell loveltech fets and the constant current diodes?

 

[EUVL]

> I would be quite keen to make the DAO with Taylor mod, where can you get the parts for this amp? I Can I use a j74 instead of J103 or is it too much voltage?

No you cannot, because you need a P-JFET with a low transconductance. If you talk to Steen nicely, maybe he can help with 2SJ103s.

> Does anyone sell loveltech fets and the constant current diodes?

http://www.diyaudio.com/forums/showthread.php?s=&postid=1646552#post1646552

Just in time. Lucky you.

Failing that :
http://www.audioprojekte.de/html/semiconductors.html

Get them while you can. They are amazing devices, if you use them right.


Patrick

 

[Luke]

Hi Patrick,

thanks for the link, I missed that one. I also found this:

http://www.diyaudio.com/forums/showthread.php?threadid=123037

Ordered a couple of those too.


Thanks for sharing it with us.

 

[EUVL]

This guy claims to have 12000 pieces and are offering US$2.75 for matched :

http://www.diyaudio.com/forums/showthread.php?postid=1646970#post1646970

12,000 will last the DIY needs for decades. There is no more reason not to build the DAO TCS, or even the DAO TCS-X.




Patrick

 

[jameshillj]

Patrick,
He hasn't actually got any of the 12,000 yet and he's been "Doing the Deal" for quite a while now and you know the saying about things "inthe mail"! - sorry Dave.

Seriously, I wouldn't imagine they're quality control rejects or production-end discards - a quick random test will tell all.

Good price for matched - tolerance is ..?

 

[steenoe]

>

No you cannot, because you need a P-JFET with a low transconductance. If you talk to Steen nicely, maybe he can help with 2SJ103s.


Patrick

Luke;
No problemo at all But a little warning is appropriate! I ordered 30 pcs at first and barely managed to get 2 matched pairs. I was probably just unlucky, 'cause usually the Toshiba's just keep rolling up matching devices. Matching/measuring my stock of 389/109's spawned several quads within 1% Man, did they match!
Well, I can get a few hundred of those 2SJ103's, in case you want some. Just shoot me a mail.

 

[Luke]

This guy claims to have 12000 pieces and are offering US$2.75 for matched :

Heavy user

Well, I can get a few hundred of those 2SJ103's, in case you want some. Just shoot me a mail.

another heavy user

Thanks for the kind offer Steen, Ill mail you.

 

[twitchie]

Is there any other alternative to the J511? I've read some other threads saying that you can use another 25V jfet with gate and source tied together with a resistor in front of it, but I have no idea what jfet and resistor value to use

Would anyone please be able to help with a modified version without the J511?

 

[h_a]

what jfet and resistor value to use

Yes that depends on the IDSS of the jfet; alternatively you can use a pot or more failsafe, a pot with a resistor in series.

Have fun, Hannes

 

[dviswa]

Steenoe,

YGPM.

Dinesh

 

[fff0]

Someone asked about modifications to the DAO follower as built by Steen.

This is the version with the Taylor Current Source.
The 2SJ103 should have about 8mA Idss.

Depending on JFET Vgs variations, the resistor values might need adjusting. I should start with a 1k trimpot for R1 to set DC offset to zero first.

Hope you'll build this. Total dissipation about 15W.


Patrick

Hi hi

Can anybody let me know if:
1) Is this the last alteration of this circuit?
2) A headamp? If so, around 1w output?