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Old 25th October 2011, 02:59 PM   #331
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Thanks Botte.
I'm just going to have to do this by ear. I can't see myself getting a frequency analyser (then again I wasn't going to build my own amps a few years back). I've set P3 on both boards mid-way and I'll just see what happens.
Chris
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Old 25th October 2011, 03:12 PM   #332
Botte is offline Botte  United States
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Quote:
Originally Posted by Backbones View Post
Thanks Botte.
I'm just going to have to do this by ear. I can't see myself getting a frequency analyser (then again I wasn't going to build my own amps a few years back). I've set P3 on both boards mid-way and I'll just see what happens.
Chris
Here’s the thing, you can use just about any old computer with a sound card for this. You just need to be careful about not overloading the input of the sound card. You can just put a couple of diodes across the input or build a pad. Look at this link for more info. Once you have this tool you will wonder how you got by without it.
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Old 25th October 2011, 04:59 PM   #333
generg is offline generg  Germany
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And if you are too lazy to build it yourself.......like me
Look for this

"VIRTINS Sound Card Oscilloscope Probe Kits- the world's first"*********************************

Virtins Technology: Turn a PC into Virtual Instrument - Products

scroll down the page...


By the way ....... Good old Aleph P looks very well concerning distortion......

K2 in my build is a bit lower than k3 and both values are very low..... At medium volume

And also an easy build....

Also no feedback, even SUSY on board .......
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Old 25th October 2011, 10:58 PM   #334
rsdio is offline rsdio  United States
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Originally Posted by Botte View Post
Here’s the thing, you can use just about any old computer with a sound card for this. You just need to be careful about not overloading the input of the sound card. You can just put a couple of diodes across the input or build a pad.
The diodes are a great idea in terms of protecting the sound card input (provided that they're wired correctly), but if they actually conduct then they will create distortion that you might falsely attribute to your amplifier under test. It seems to me that a passive pad would be a superior choice since it shouldn't introduce significant distortion. Then again, an insufficient pad wouldn't protect your sound card, so perhaps both are needed. I guess it depends upon your exact situation and the amount of gain in your amplifier.

The link you provided seems to have good suggestions.
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Old 29th October 2011, 03:21 PM   #335
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Can someone confirm that 'D' on the BA-3 board goes to 'D' on the bias board.
Also, can I set the 1V across R10 and R11 with just the power supply connected.
Chris
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Old 29th October 2011, 04:01 PM   #336
generg is offline generg  Germany
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Yes
D to D ....

You set the 1V power supply connected..... Correct!
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Old 29th October 2011, 04:12 PM   #337
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Yes
D to D ....

You set the 1V power supply connected..... Correct!
Thanks generg,
No sounds yet. Connected the mosfets round the wrong way because I was in a hurry. Now I'm going nowhere waiting for replacements.
Chris

Last edited by Backbones; 29th October 2011 at 04:14 PM.
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Old 29th October 2011, 08:37 PM   #338
generg is offline generg  Germany
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Oh what a pity.......,

I also stopp sometimes my work too late and I produce faults....mostly with the second channel, less concentrated, already a bit eager to have a result, euphorized from the working first channel .....

But I learn ... Do you have to wait a long time for your replacements?
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Old 29th October 2011, 11:21 PM   #339
JimM is offline JimM  United States
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Can anyone give me a idea on how the fairchild FQP3N30 and FQP3P20 sound vs. the Toshiba parts (2SK2013 and 2SJ313). The Toshiba parts seem to be in short supply.
Thanks
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Old 30th October 2011, 12:05 AM   #340
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I have some for $5/pair plus shipping.
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