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Old 15th February 2011, 07:57 AM   #1
vivanco is offline vivanco  Italy
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Default questions preamplifier aleph P1.7

hello, I'm making the preamp in question because I want to match it to the final stereo ready (aleph mini version of 10W single end);
looking at the circuit, I noticed the presence of a trimmer 2K, so I ask what is its setting (I guess this is for the bias current for proper operation of the differential);
two more questions:
Which property should have the electrical power transformer (the secondary output and power?)
what value of potentiometer 4 sections I use to create the volume control and where to enter (entry or output?)
thank you very much for your important help.
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Old 15th February 2011, 09:36 AM   #2
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Quote:
Originally Posted by vivanco View Post
hello, I'm making the preamp in question because I want to match it to the final stereo ready (aleph mini version of 10W single end);
looking at the circuit, I noticed the presence of a trimmer 2K, so I ask what is its setting (I guess this is for the bias current for proper operation of the differential);
two more questions:
Which property should have the electrical power transformer (the secondary output and power?)
what value of potentiometer 4 sections I use to create the volume control and where to enter (entry or output?)
thank you very much for your important help.
hello.
for the transformer. you can use a 2x30V 160VA with secondarys conected in series. the 2k pot, isn't that the secondary volum pots?
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Old 15th February 2011, 10:35 AM   #3
vivanco is offline vivanco  Italy
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Quote:
Originally Posted by AudioSan View Post
hello.
for the transformer. you can use a 2x30V 160VA with secondarys conected in series. the 2k pot, isn't that the secondary volum pots?

160VA

Are you sure of this information?
surfing the net, I found the site KK-PCB, where I saw the power supply for aleph P1.7;
60Volt 50VA transformer is indicated for both channel,,,this indication is correct?

trimmer 2K is on the branch connecting the differential, I need to know how to make its regulation, that is, which parameter should I refer?
if I understand it, reading the manual of the great Nelson Pass, the volume control must be placed on the input of the preamplifier, using a binary system to relay, I wonder if you can use a simple potentiometer four sections, and if so what value?

thanks
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Old 15th February 2011, 12:13 PM   #4
vivanco is offline vivanco  Italy
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someone to give me a hand please do
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Old 15th February 2011, 02:24 PM   #5
SRMcGee is offline SRMcGee  United States
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Vivanco:

I used an 80 VA toroid with 60 VAC secondaries on my Aleph P 1.7. Fifty VA is purportedly the norm, though I've heard that 30 VA is more than adequate.

The attenuator should have very low impedance -- 1k or 2k works well -- and should precede the preamp.

Regards,
Scott
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Old 15th February 2011, 02:47 PM   #6
vivanco is offline vivanco  Italy
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Quote:
Originally Posted by SRMcGee View Post
Vivanco:

I used an 80 VA toroid with 60 VAC secondaries on my Aleph P 1.7. Fifty VA is purportedly the norm, though I've heard that 30 VA is more than adequate.

The attenuator should have very low impedance -- 1k or 2k works well -- and should precede the preamp.

Regards,
Scott

Then I can use a transformer with a secondary 60V 50VA x,,,
I have an ALPS potentiometer 10K x 4 sections, I can use it by inserting it between the input and the preamp and the same fine-tune the gain using the trimmers from 2K that I have already put on board the pcb's?
thanks so much for your interest

Gianni
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Old 15th February 2011, 03:53 PM   #7
SRMcGee is offline SRMcGee  United States
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Gianni:

You can, but if you search you'll find posts that indicate that 10k impedance is on the high side for this preamp. From personal experience, I can tell you that 2k sounds terrific.

Regards,
Scott
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Old 15th February 2011, 05:18 PM   #8
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This thread is a bit confusing. The attenuator of the original Aleph P1.7 is on the output of the preamp, and is 1Kohms.

If you are going to attenuate the input you can use anything you wish, but 10K would be a very good choice.

Your trimmer sets the gain of the differential, the lower the setting, the more gain. I believe I read that around 200ohms is what most people like the best.

50VA is plenty.

Best, Bill

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Last edited by Bill Fuss; 15th February 2011 at 05:24 PM.
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Old 15th February 2011, 08:40 PM   #9
generg is offline generg  Germany
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I can only confirm the things Bill writes.......
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Old 16th February 2011, 12:50 PM   #10
vivanco is offline vivanco  Italy
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one thousand ggrazie Bill and thanks to you all, now I understand the situation, if you want I'll keep you informed of the progress,,, hello, I go to work :-)

gianni
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