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Old 21st April 2003, 02:32 PM   #21
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Peter Daniel


Making a gainclone to sound special is not that easy.
and what about making one that sounds good?
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Old 21st April 2003, 02:35 PM   #22
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Quote:
Originally posted by Bricolo

and what about making one that sounds good?
This is not that hard if you follow suggestions in the GC thread
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Old 21st April 2003, 02:38 PM   #23
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To Steve Eddy:

Sure, but not with the famous 1.5K resistor to Vsupply! The gainclone chips' temperature and current safety circuits make it unsuited for high bias (say 25 Ohm to -33V supply).

Regards,

Thijs
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Old 21st April 2003, 02:38 PM   #24
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Peter Daniel


This is not that hard if you follow suggestions in the GC thread
FC ps caps, type N input & coupling caps? brand resistors?


I only use cheapo parts (for the momment) in mine

It doesn't sound bad, on my crappy speakers (crappy crappy...)




Peter: when you are about to test an amp's (or anything else) sound, how are you proceeding?
You certainly listen to a perfectly known CD, but what do you pay attention for?
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Old 21st April 2003, 02:38 PM   #25
miguel2 is offline miguel2  Portugal
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I use a 28 VDC supply with 6800uF per rail in the PSU. In the amp I use 1000uF per channel and per rail, bypassed by a 1uF film cap between + and -.

Miguel
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Old 21st April 2003, 03:02 PM   #26
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It shouldn't be that hard to disonnect 6800 caps. I'm curious on your findings, just use 1000u per rail. And if DC allows, don't use coupling cap.

When I listen to the amp, I have a Zen like state of mind, and I try to find what's my reaction to music is. If I enjoy it, then I look further into details, frequency extention, soundstage and try to listen to familar tracks. But the most important factor is that the music must feel real and not boring.
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Old 21st April 2003, 03:28 PM   #27
miguel2 is offline miguel2  Portugal
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Quote:
It shouldn't be that hard to disonnect 6800 caps.
well, it is anothers amp PSU, and I have not access to the bottom of the board without taking the whole thing apart...

But I can use the transformer's leads and a diode bridge to take out the juice. That is easier.

Of course I keep the inputs/outputs of this amp disconnected when I use the gainclone, so the few mA it draws in iddle should not affect the sound.

Miguel
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Old 21st April 2003, 03:28 PM   #28
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Quote:
Originally posted by analog_sa
But at what level? We're talking 20mA or so through the biasing resistor, right?
It depends on the value of the resistor and the rail voltage. You can set the resistor to run as much or as little current as you want provided it's within the SOA of the device.

se
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Old 21st April 2003, 03:42 PM   #29
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Quote:
Originally posted by tschrama
Sure, but not with the famous 1.5K resistor to Vsupply! The gainclone chips' temperature and current safety circuits make it unsuited for high bias (say 25 Ohm to -33V supply).
Well, that 1.5k resistor is only meaningful in the context of small signal opamps.

Not sure exactly what you can ultimately get away with using the LM-3875. I'd have to take a look at the datasheet. Certainly you wouldn't be able to get away with something on the order of 50 watts as you suggest above. But I don't see any reason why you couldn't get away with it down around say 10 watts or so.

se
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Old 21st April 2003, 05:43 PM   #30
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I am more or less gathering that the OPA541 is not good... well, I have two of them lying around, so is it even worth my trouble? Or should I just get an LM3875 and let it be that?

I think I mentioned this before... I am using a Sony CDP-CE375 cd-player RCA outs as my source. I do not know if there is any DC present here. I can check... just run the MM from output ground to output signal with MM on DC, right? What is a safe level?

The amp will be used with speakers I am building (8" Eminence, 1" Selenium tweeter, in 1.1cu.ft. box). I will also be making a sub preout, probably including a preamp there, for a 15" DIY sub I have also. With speakers such as these, which chip would sound best? Overall sens= 97-100dB throughout audio spectrum.

A note on parts, again: The speakers I am using will use Solen crossover caps, the same ones I would have used on the amp input. Iw as planning to bypass the 3.3uF metallized Solen coupling cap with a .22uF polypropylene. would this help anything? Should I source other caps? Is .47uF enough on input, or do I need more?

Also on parts: the Nichicon UPW's are spec'ed basically the same as Panasonic FC. Shouldn't they be an ok subtitute? I cannot order enough from Digi-Key to meet the minimum order, which is why I would like to cut them out. Are 1/2W RN65D Vishay/Dale resistors sufficient?

Thanks
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