Walt Jung Class A preamp

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#121
ppl:

start using more linear BJT for the second stage (Q5 and Q6) like 2SC2240/2SA970,ztx453/553, fmmt493/593. Also use japanese BJT in the output stage or mosfet's heavily biased (but the is should some with low gatecharge -> irf610/9610 (1.choice), buz900/buz905 (2.choice)).

For an amp with the walt jung buffer ... http://www.diyaudio.com/forums/showthread.php?threadid=1794&highlight=jfet

It works nice.. but some jfet matching is needed.

Sonny
 
#122
sonnya;

Thanks for your sugestions. I Have the ztx453/553, fmmt493/593 Transistors, Will sub. I don't Like Mosfets but like you sed heavy Bias for them sound better. I will however stick with a BJT output stage. What Japanese BJT Types for Output? For output Currents less than 1 Amp The Motorolla (ON Semiconductor) types I listed looked Good to me with the Exception of Ft?

Thanks;
 
#126
So far the Sound is not bad. Lots of dynamic Punch, However the upper mids and higher are Kind of Dark Sounding In the present form the 2N3904 & 2N3906 are replaced with MPS-8099 & MPS-8599. What do you think of these transistors?
 
#129
The Fets i used were because thay were the only Well matched pair of Comp. Jfets I had at the time. Any Alternate sugestions? Hopefully of US or Euro make as these are a plenty hear.
Thanks. Also check out some of the Devices at this site http://www.linearsystems.com/ I used there Dual comp. BJT's in a DIY Power Amp as Comp. Diff amps and that worked and sound great very well matched and low noise. LS-312 & LS-352. BJT's
 
#130
LK-1 Circuit

Here is a image of the LK-1 circuit I think that the distorsion is rather high 0,1 % thd maybe it would be some adjustment to the circuit but where?🙂
 

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#134
Jfet version of WJ buffer

Any seen the Jfet version of WJ buffer I have searched but I can't find it I'm also interested in to get some info regading the best new ZETEX BJT's are these the very best for audio wich types should I buy, I see that we DIYer's have to stick to current types.🙂
 
#138
Re: LK-1 Circuit

leiade said:
Here is a image of the LK-1 circuit I think that the distorsion is rather high 0,1 % thd maybe it would be some adjustment to the circuit but where?🙂
Click to expand...

leiade,

the Linn LK1 circuit simply has not enough gain. The current from the input stage is mirrored twice, and maybe there is a tenfold current muliplification at the first set of current mirrors (depending on actual resistor values not shown in the circuit schematic), but that is simply not enough.

If you convert it into differential amp -> differential VAS stage -> current mirror, you get early Mark Levinson style from raw topology and much reduced distortions. Mind the phase, when doing the conversion. Check for oscillations, because of more open loop gain.

regards,
Hartmut
 
#139
Why Preamp???

It's easy just make a good little power amplfier say about 8Watt/8 Ohm I can't get into my head why a preamp must to be just a preamp with small signal level just voltage no current it's must be an old basic statement.

If a preamp was designed as a little power amplifier wich very often has very good THD figures and can deliver a whole bunch of voltage and current when needed Ok! if I check an power amplifiers spec's it very often can deliver low distorsion high voltage and high current what more we need.
8 Watt is 8 Volt in 8 Ohm 8 volt maximum is that enough to drive a power amp its maximum???🙂
 
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