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Bruno Putzeys Balanced Preamp - Group Buy Part 2
Bruno Putzeys Balanced Preamp - Group Buy Part 2
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Old 26th February 2016, 05:22 PM   #11
tfboy is offline tfboy  United Kingdom
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I made a few tweaks to initial post with current status. It should make a bit more sense now
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Old 26th February 2016, 09:49 PM   #12
billshurv is offline billshurv  United Kingdom
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Bruno Putzeys Balanced Preamp - Group Buy Part 2
Added. I may regret not buying some extras, but I do have about an 18 month project backlog!
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Old 27th February 2016, 07:31 AM   #13
sq225917 is offline sq225917  United Kingdom
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Send a message via MSN to sq225917 Bruno Putzeys Balanced Preamp - Group Buy Part 2
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Old 27th February 2016, 08:12 AM   #14
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by tfboy View Post
I made a few tweaks to initial post with current status. It should make a bit more sense now
your signature link took me to post21 of the old GB Thread.
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Old 27th February 2016, 09:00 AM   #15
tfboy is offline tfboy  United Kingdom
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Thanks for the heads up, Andrew. Corrected

A few more orders came in.

I've received a few PMs with order requests. Can I please ask people to express their interest by email - it's the easiest way for me to keep track of everything. Thank you
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Old 27th February 2016, 03:46 PM   #16
tfboy is offline tfboy  United Kingdom
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Made a few new tweaks to the original mail to clarify things further

I'm also aiming to wrap this up by Sunday 6th March, so please put your name in if you want to take advantage of the discounted pricing
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Old 27th February 2016, 08:07 PM   #17
badman is offline badman  United States
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Is low gain an option on this?

Thanks!
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Old 28th February 2016, 07:15 AM   #18
AndrewT is offline AndrewT  Scotland
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The input stage is unity gain buffer.
The differential stage uses equal value resistors so it too is unity gain.

All the gain/attenuation is in the third stage.
The maximum gain is set when the vol pot places near zero ohms to the left of the wiper.
This maximum gain can be reduced by preceding the vol pot with a fixed value resistor. I am hoping to modify the PCB and place an 805 in that input trace to achieve this gain limit.
This modification would turn the system into a low gain version.
Alternatively one never turns the vol pot past 50% rotation. But that is not a nice way to have to operate this pre-amp all the time. It squeezes all the control of attenuation into the first 50% of rotation.
The added resistor gives the option of extending the control to the full 100% of rotation and a maximum gain of +0dB.
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Old 29th February 2016, 06:41 AM   #19
tfboy is offline tfboy  United Kingdom
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Regarding the actual circuit design, I've attached the Gerber files Quick Circuits will use.

I've had a look at them and they seem fine to me - some of the silkscreen positioning could be improved perhaps, but the circuit parts are fine.
Attached Files
File Type: zip MicroPreGerbers.zip (53.9 KB, 53 views)
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Old 29th February 2016, 08:28 AM   #20
AndrewT is offline AndrewT  Scotland
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Is it too late to consider a multi-purpose pad arrangement for the four high peak current "melf" resistors?

Pad arrangement to allow 1206, or 0204 melf, or 0207 melf?
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