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Old 23rd June 2014, 09:02 AM   #3991
AndrewT is offline AndrewT  Scotland
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Silly PCB layout exacerbated by big LOOP AREAS at the IN/OUTs

Compare to the original DCB1 IN/OUTs
except that PCB had a grounding error at the relays. I don't have a later PCB to confirm if the "mod" has been applied to the newer PCBs.
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Last edited by AndrewT; 23rd June 2014 at 09:05 AM.
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Old 13th July 2014, 01:09 PM   #3992
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Hi guys,

very interesting Buffer Pre amp to it's simplicity built. Does it work as common pre amp? Or only increase gain?

Does it suit to Gain clone?'

Tq!
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Old 13th July 2014, 01:35 PM   #3993
6L6 is online now 6L6  United States
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No gain, it's a buffer. It allows the attenuator to work in an ideal environment.

Yes, it suits gainclone very well.
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Old 14th July 2014, 02:39 AM   #3994
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Sound very promising.
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Old 21st July 2014, 09:42 AM   #3995
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Hello to everyone.

I was wondering, if there will be improvement in sound quality by attaching B1 to a F5, if I was directly driving F5 fron DEQX DSP xover. No potentiometer in path, volume control digitally in DSP. I have 3 way active system, DEQX as active xover with some DSP correction, then 3 x F5 amplifiers. Please advise, I luck a little of withdness in sondstage.
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Old 21st July 2014, 11:16 AM   #3996
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I'd look at the digital resolution, noise floor and output impedance of your DEQX. The usual arguments regarding analog vs digital volume control will apply.

If the output impedance is low enough to drive the F5 nicely, you can adjust volume within the range you need without eating up the digital resolution of the audio to a noticeable degree, and the noise floor of the DEQX output is low enough that it isn't audible from your listening position, then it's unlikely that the B1 will improve the quality of your playback (unless the B1 distortion spectrum sounds good to your ears).

If on the other hand the DEQX doesn't pass all of these criteria, adding the B1 may well improve your system.
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Old 21st July 2014, 04:32 PM   #3997
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I guess DEQX output impedance is 75 ohm, resolution is 24 bit, and no audiable noise
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Old 3rd September 2014, 06:06 PM   #3998
Hammett is offline Hammett  United States
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Default Did something dumb

For reasons that are not clear right now, when I built my B1 this summer I committed a double error, intending to shift r102/104/202/204 to 330 ohm resistors, but I mistakenly bought 330k ohm.

I then compounded the mistake by putting them in r101/103/201/203 instead of the 1M resistors that should have been there.

The unit sounds mighty good to be honest, but I am wondering if I screwed up so badly that I need to rip them out and replace them with the proper values.

Any thoughts (besides that I should read a schematic more carefully)?
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Old 3rd September 2014, 06:44 PM   #3999
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by jaskierster View Post
I guess DEQX output impedance is 75 ohm, resolution is 24 bit, and no audiable noise
I would guess it's more like 100ohm to 110ohm connection.
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Old 3rd September 2014, 07:00 PM   #4000
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Hammett View Post
For reasons that are not clear right now, when I built my B1 this summer I committed a double error, intending to shift r102/104/202/204 to 330 ohm resistors, but I mistakenly bought 330k ohm.

I then compounded the mistake by putting them in r101/103/201/203 instead of the 1M resistors that should have been there.

The unit sounds mighty good to be honest, but I am wondering if I screwed up so badly that I need to rip them out and replace them with the proper values.

Any thoughts (besides that I should read a schematic more carefully)?
Changing R101/201 from 1M0 to 330k changes the DC input impedance of in2 to 330k. Not much effect. You can leave this with the 330k. It may reduce very slightly the noise when you remove in2 interconnect.
Changing r103/203 from 1M0 to 330k changes the AC input impedance to 330k. Not much effect. You can leave this with 330k

The combined effect is that the input impedance becomes 165k from the 500k that it would otherwise have been.
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