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Old 9th September 2003, 01:32 PM   #11
just another
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Thanks jcx.

Most of what you said is beyond my comprehension level, but I'll take your word on it

The amp definitely has some problems in the preamp design (It's actually an integrated amp, I only showed the power amp), so It doesn't surprise me that there may be other problems.

I guess what I really need to do is get off my behind and make my new speakers (which I'm sure are a weaker link at the moment than the amp), then do some A B comparisons with a known good amp, so I can see whether I can hear the difference, and then decide what to do with it.

Regards,

Tony.
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Old 9th September 2003, 08:03 PM   #12
DrG is offline DrG  South Africa
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This post is not necessarily a suggestion for you, Wintermute but more of a question for jcx, aksa and the other very knowledgable SS engineers here.

The 12k/15nF combo in the 2nd LTP doesn't appeal to me. What do you think about replacing it with another BF469, base connected to ground?

Other mods I might try: (1) increase tail current or tail resistors slightly in 1st LTP, in order to increase Iq in 2nd LTP, (2) increase the 100nF shunt cap across the bias pot (substantially).

I'm keen to hear the forum opinions on these proposals.

Besides these "ideas", I would personally replace all caps: larger psu caps with poly by-passes, much larger NFB cap (NP type); replace CCS with resistor. Most of these suggestions have already been made...
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Old 10th September 2003, 03:52 AM   #13
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Quote:
Originally posted by DrG
replace CCS with resistor.
This one may not be such a good idea (I'm only going on what the original amp designer said here not on my own wisdom )

According to the writeup about the design, that came with the kit, the ccs is there to substantially improve the PSRR of the amp, so getting rid of it might improve sonics at the expense of hum????

I've bought a soundcard preamp (which I haven't built yet) and downloaded some CRO software, I'd like to do some measurments around the place (once I work out how ) and do some comparisons before and after changing caps etc as suggested.

Regards,

Tony.
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