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Versatile and comfortable passive pre-amp

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Master Rudi , would. It be possible to ask for your help creating remote controlled on off switch using small footprint ? I need it for my amp which would ideally be triggered by same protocol on off as foir vcpre. ? I d use same remote as with pre.
Thx
Ivan
 
Ivan, this would of course be possible.

All you need is a small PIC-processor, an infrared-sensor, a relay and a piece of software.
But I am very busy currently and do not have the time to do it.
Moreover: who will etch the PCB for you?

Best regards - Rudi_Ratlos
 

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VCPre boards for sale

Hi. I have not yet assembled my VCPreamp. But with Rudi announcing the new one with the integrated Calvin buffer, I think I will wait for that one. This was going to replace a similar setup with a dcb1, but Rudi's new one will let me have a new complete preamp without changing my current dcb1 setup. Hope you don't mind me posting the for sale here, but I've seen a few people ask if there were any kits left.
 
Ivan: you are right. Uriah has stopped selling matched quads of LDRs.
But this is no problem. I have built a small test-rig myself (a rotary switch with 10 resistors from 80K to 470Ohm connected to the DUT 🙂) and will offer matched LDRs once I will offer the new, enhanced VCPre-version.
The size of the PCB will be 150 x 80mm.

Best regards - Rudi_Ratlos
 
Will the new VCPre offer to switch digital sources along analog sources?

If not directly, then maybe at least an option for it, like digital pin out from the PIC that could be used to control another board, that would choose the digital source before the DAC?
 
TUO: my passive Pre-Amplifier is able to connect to (to choose between) five - music-sources (by means of the 5 relays on top of the PCB).
I myself will configure my own Pre-AMP to connect to one digital source (Jean-Paul/Subbu's DAC) and 4 analog inputs (CDP, Tuner, ...).

In the meanwhile I have layouted the needed PSU - PCB (Image1).
The requirements are: 8VDC (to provide currents to the MICREL5205 and the motorized potentiometer), +5VDC for the digital part of the Pre-Amplifier and the DAC) and +/-18VDC for the line-buffer.
I am very happy to have found a transformer (even an R-Core!) that will provide the needed secondaries: 2 x 9VAC and 2 x 18VAC.

Find attached (on the second image), how I will implement a very smooth, "ripple-free (?)" 5VDC - voltage / current regulator, using the LM317 as "tracking-pre-regulator".
This one will provide a very stable 5VDC to the DAC and the digital part of the pre-AMP.
I have come across this circuit while reading about the LM317.

In case you do not find a severe error in my design: I will order a couple of prototype PSU-PCBs on the day after tomorrow.

Best regards - Rudi_Ratlos

P.S. The 5VDC - output voltage is determined by 1.25V (adjustment of LM317) plus 2 x LED - voltage - drop (3.84V).
P.P.S.: this is the article that I am referring to: http://www.acoustica.org.uk/t/3pin_reg_notes4.html
 

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Motor not working on volume control

Rudi,
I got around to repairing my issue with volume control not turning. I ordered a set of BC548b and 2N5551. When I removed the BC548b and checked them they checked fine, I was a little concerned it had reversed the pin-out as you had mentioned in the instructions. Oddly when I removed the 2N5551 two of the four of them were reversed. On examination they appeared to be from he same manufacture and were purchased at the same time from the same supplier. Since these did not requiring matching I never tested them before installing, morel is from now on I will test all components before installing and save some time down the road.

Many thanks
Bill
 
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