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Old 5th December 2012, 01:21 PM   #1361
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Try repeating the test on your preamp, both connected to your amp and alone. How much can you get out of it to driving the amp? Is the output voltage lower with the amp connected?

I'm guessing that although amp gain is correct, your feedback network resistors may be an order of magnitude lower than expected (1K input instead of 10K), presenting a low impedance load that your preamp cannot handle.
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Old 5th December 2012, 01:43 PM   #1362
kroyin is offline kroyin  India
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Preamp is B1 ... tested before ...unity gain .. x in x out..
As per the readings in my previous post my AJ is working as expected ..right? ??
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Old 5th December 2012, 01:55 PM   #1363
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source , preamp , speakers , what's gain of F5 ?
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Old 5th December 2012, 02:16 PM   #1364
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Quote:
Originally Posted by Zen Mod View Post
source , preamp , speakers , what's gain of F5 ?


Question first :-) is 10x voltage gain par for AJ?

Source-linux->wm8741 dac->b1 with 2x50k mono pot (same setup for F5)
Speakers are 90db 2.5 way troels gravesen nomex

AJ (F5 before that) uses the same trafo, same psu & caps.
F5 biased @ 1.3A (single pair) with 20dB gain (200r resistors)
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Old 5th December 2012, 02:17 PM   #1365
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A B1 ought to be able to handle the amp and not load the source significantly. Measure the source's output into your B1. You should be able to find some full scale signals to burn to CD to test with.

You may need a little gain in the system now. One easy way would be to increase the gain of your AJ a bit, but of course that would impact its sound.
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Old 5th December 2012, 02:25 PM   #1366
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And yes, 10x voltage gain is 20 dB, so the amp is working correctly.

Have you tried with the exact same music with the new amp (too bad you can't do a side by side comparison)? Apparent loudness of individual tracks can vary widely. It's a bit surprising to me how soft so many of my older songs sound compared to modern recordings and 30 years of loudness wars. I find myself riding the volume control as I shuffle through my ripped music collection.
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Old 5th December 2012, 02:32 PM   #1367
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Quote:
Originally Posted by BobEllis View Post
And yes, 10x voltage gain is 20 dB, so the amp is working correctly.

Have you tried with the exact same music with the new amp (too bad you can't do a side by side comparison)? Apparent loudness of individual tracks can vary widely. It's a bit surprising to me how soft so many of my older songs sound compared to modern recordings and 30 years of loudness wars. I find myself riding the volume control as I shuffle through my ripped music collection.
Well song was Floyd Us & Them & yup I have heard it on both setup..

If the AJ is setup ok,I can build Jumas preamp (meant for F5)
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Old 5th December 2012, 02:52 PM   #1368
kroyin is offline kroyin  India
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Quote:
Originally Posted by BobEllis View Post
And yes, 10x voltage gain is 20 dB, so the amp is working correctly.

Have you tried with the exact same music with the new amp (too bad you can't do a side by side comparison)? Apparent loudness of individual tracks can vary widely. It's a bit surprising to me how soft so many of my older songs sound compared to modern recordings and 30 years of loudness wars. I find myself riding the volume control as I shuffle through my ripped music collection.
Well song was Floyd Us & Them & yup I have heard it on both setup..

If the AJ is setup ok,I can build Jumas preamp (meant for F5)
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Old 5th December 2012, 04:50 PM   #1369
Zen Mod is offline Zen Mod  Serbia
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well - you made your measurements

it seems everything is OK

Gremlins in action , maybe ?

btw. I'm quite often finding that short circ between two headphones is troublesome for me
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Old 5th December 2012, 05:21 PM   #1370
kroyin is offline kroyin  India
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:-) grounding gone bad ....there's buzz, hell they even came up with a fancy name ..tinnitus
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