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Old 11th June 2013, 02:50 PM   #21
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Jorge: METAL and I will definitely offer this PCB in a group-buy. METAL is currently re-working the µProcessor's software (firmware)
to include the changes (f.e.: Soft-Power-On interface, HTBypass interface, ...), while I do the layout-changes
and keep the documentation up-to-date.
I suppose to start the group-buy next week, but we have to settle upon what I will offer in this group-buy (PCBs, pre-programmed µProcessor,
for sure, what else?) first.

Wineds: the schematics are posted in the documentation ("Builder's Manual") that I will send to all participants of the group-buy.

The VCPre is communicating its status on a 1x16 chars, HD44780 compatible LCD display. I will use a display with 9mm big letters.

You may use the display, but you need not.
The status of the source selection relays, the HTBypass relay and the Soft-Power-On relay will be reported on LEDs as well.

Find attached 2 pictures.
The left one shows how my front panel will look like, while the right one shows the front panel of a German DIY-friend of mine.
He is using McIntosh-like panel meters that are driven from a small DIY-PCB.

Best regards - Rudi_Ratlos
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File Type: png Image5.PNG (40.1 KB, 511 views)
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Old 11th June 2013, 03:36 PM   #22
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@Voxxonline: I do see no reason, why this is not doable.

The VCpre needs 2 voltages: 5VDC (7805) for the analog and digital world and 6VDC (7806) for the Motor-H-Bridge
to drive the motorized potentiometer.
The power-consumption of the VCPre is: 1-2 source relays (source-input and HTBypass, if HT is selected), 2-3 LEDs
(Active/Sleep-LED, 1-2 source-input relay LEDs), LDR-LED current, LCD display, µProcessor: round about 100mA.

The motorized-potentiometer needs about 100mA if processed.
I am not aware of any hum or "electronic smog" that the VCPre generates, nor do the German DIYers, who have already built the VCPre.

Best regards - Rudi_Ratlos
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Old 11th June 2013, 03:37 PM   #23
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That is the approx price of complete build?
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Old 11th June 2013, 03:46 PM   #24
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And physical size of the boards please
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Old 11th June 2013, 03:53 PM   #25
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Hi Rudi, nice project. I would not use Molex KK for 230 V though. Better use a Phoenix MKDS for that. If you use a FR5 fuse it will fit.

Did you measure the device ? The transformer is pretty close to the audio circuitry. I think your GB will be a successful one as it is a complete versatile device. A buffer would have made it suitable for preamp use with separate power amps.
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Old 11th June 2013, 03:53 PM   #26
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@Voxxonline:

I am currently calculating prices (they depend of course upon the amount of orders), but I can give you the size of the PCBs immediately:

VCPre - PCB: size is 100 x 100mm
SPO - PCB: size is 80 x 70mm
HT - PCB: size is40 x 29mm

Best regards - Rudi_Ratlos

P.S. Jean-Paul: I will look for PHOENIX MKDS in my EAGLE-library.
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Old 11th June 2013, 04:33 PM   #27
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Hi please look for this one: MKDS 1,5/2

http://www.farnell.com/datasheets/100425.pdf
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Old 11th June 2013, 04:39 PM   #28
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Hi Jean Paul!
How do you think this pre would mate with Subbu dac + gb buffer?
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Old 11th June 2013, 04:40 PM   #29
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Jean-Paul: here we are.

Best regards - Rudi_Ratlos
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Old 11th June 2013, 04:43 PM   #30
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That depends on the input impedance of this pre. The Subbu DAC does not like very low impedances. I take the liberty of asking some questions to Rudi:

1. What is the input impedance of the VCPre ?

2. At what load starts it to choke ?

3. Why no buffer at the output ?

Quote:
Originally Posted by Rudi_Ratlos View Post
Jean-Paul: here we are.

Best regards - Rudi_Ratlos
That is better Rudi. Don't you think the SPO tracks run too close to AC pins of the transformer ? Also upper 230 V AC track from the fuse to the primary pin can be adjusted so that it stays further away.

* the whole input section can be moved somewhat closer to the upper side of the PCB. The further away from the transformer the better it is.
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