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/showt...20#post1592820

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

http://www.diyaudio.com/forums/showt...71#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]

Originally posted by h_a

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]

Originally posted by jameshillj


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?