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Old 25th March 2009, 11:44 AM   #91
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Default Re: Re: PC board layout.

Quote:
Originally posted by juma



Here you are, copper side view:

Thank You.

Joe
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Old 4th April 2009, 03:41 PM   #92
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just a thanks to juma-got one of your preamp modules installed in a F5 and playing it right now-sounds great!!!!!!!!!!! thanks-mark and joe
ps- named this one F5HO -- ( High Output )
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Old 7th April 2009, 11:09 AM   #93
juma is offline juma  Serbia
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You are welcome
I'm glad you like it. BTW, which one did you choose?
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Old 7th April 2009, 07:31 PM   #94
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one from post 53
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Old 14th April 2009, 01:57 AM   #95
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juma....what do you measure to adjust the DC offset?
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Old 14th April 2009, 08:14 AM   #96
juma is offline juma  Serbia
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DC offset is unwanted DC voltage on amp's/preamp's output, so you should measure it between output point and ground.
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Old 12th February 2012, 06:53 PM   #97
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How well would an AMB a20 set up for voltage gain work as a pre-amp for the F5?

The α20 Line Stage Amplifier
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Old 12th February 2012, 08:44 PM   #98
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Quote:
Originally Posted by Jack Tupp View Post
How well would an AMB a20 set up for voltage gain work as a pre-amp for the F5?

The α20 Line Stage Amplifier

F5 has a very high Zin (101k) so it doesn't need high current drive i.e. EF (Q5,Q6). Without EF Vbe multiplier(Q7) makes no sense so we will lose it too. What is left is schematic from post #53 of this thread (which has higher Id through JFETs in order to avoid that grainy sound that makes some people to hate JFETs).
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Old 12th February 2012, 09:41 PM   #99
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Quote:
Originally Posted by juma View Post
F5 has a very high Zin (101k) so it doesn't need high current drive i.e. EF (Q5,Q6). Without EF Vbe multiplier(Q7) makes no sense so we will lose it too. What is left is schematic from post #53 of this thread (which has higher Id through JFETs in order to avoid that grainy sound that makes some people to hate JFETs).
"It is configurable at build-time for a voltage gain of 1 to 20 (0dB to 26dB)"

Even if you set it up for voltage gain?
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Old 12th February 2012, 10:06 PM   #100
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Many signal sources have Vout of 2V RMS and many have less. F5 needs about 2.6V RMS at its input for full power output. So you need some gain. How much? It depends on your sources. Maybe you have very efficient speakers and you don't need to drive your F5 to full power - then you'll need no additional gain from preamp. It's all about what you have and what you need...

BTW, the gain is set by ratio of resistor values in the feedback loop (R14/R13 in alpha20 sch.)

Last edited by juma; 12th February 2012 at 10:08 PM.
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