Doug Self Preamp from Linear Audio #5

I had been told by others that this transformer (or it's pinout equivalent) was easily available in the EU/UK ... No???

If there is enough interest I can easily add the 114/230v jumper mod to the PCB.

I looked at several types but couldn't find one that fitted so bought the recommended one.

If you do the 115/230 mod, I'll buy a couple more pcbs for other projects.

Attached Vigortronix data - mains pins and pin spacing generally all completely different.
 

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So through the BOM i went to TAYDA parts distributor?? Anybody know anything about parts quality fro this place? Would you order things like caps and transistors or maybe just headers and switches. Let me know

Omeg produce a high quality plastic film 4k7 pot but they are all sold.

Our UK supplier is expecting stock mid October. I don't know who the US distributor is but they will be waiting on stock too I expect.

https://cpc.farnell.com/omeg/pc2g16eco4k7a/pot-dual-gang-lin-4k7/dp/RE04429

Its best to buy the other components from Mouser & Digikey using their stock numbers that are on the BOM.
 
Omeg produce a high quality plastic film 4k7 pot but they are all sold.

Our UK supplier is expecting stock mid October. I don't know who the US distributor is but they will be waiting on stock too I expect.

https://cpc.farnell.com/omeg/pc2g16eco4k7a/pot-dual-gang-lin-4k7/dp/RE04429

Its best to buy the other components from Mouser & Digikey using their stock numbers that are on the BOM.

I forgot to add that I used Vishay R55 series very low noise 1% resistors instead of the ones on the BOM (I couldn't find a noise figure for them).

E.g.

RN55D6800FB14 Vishay / Dale | Mouser United Kingdom

The Nichicon UES series caps are important as they are their 'Muse' audio grade non polar electrolytic capacitors so do not substitute.

My build is on hold until the Omeg pots arrive but apart from them and the resistors, I stuck to the part numbers on the BOM.
 
I forgot to add that I used Vishay R55 series very low noise 1% resistors instead of the ones on the BOM (I couldn't find a noise figure for them).

E.g.

RN55D6800FB14 Vishay / Dale | Mouser United Kingdom

The Nichicon UES series caps are important as they are their 'Muse' audio grade non polar electrolytic capacitors so do not substitute.

My build is on hold until the Omeg pots arrive but apart from them and the resistors, I stuck to the part numbers on the BOM.

Aren't RN55 series 1/8W? The BOM suggests 1/4W
 
Hi to all
I am finishing my Pre-amp and wish to make the front panel labels with a laser machine on wood. The panel layouts in the forum cannot be read by the appropriate software. Apparently a PDF file can be used so I wonder if anyone has such a file. It would save a large amount of time and learning if I were able to obtain one.
Cheers
Wayne
 
Hi to all
I am finishing my Pre-amp and wish to make the front panel labels with a laser machine on wood. The panel layouts in the forum cannot be read by the appropriate software. Apparently a PDF file can be used so I wonder if anyone has such a file. It would save a large amount of time and learning if I were able to obtain one.
Cheers
Wayne

Wayne,

No guarantees but ...

I couldn't leave you hanging. Here is a front panel PDF of the FPD file for the v2 layout of the preamplifier. It is intended to be printed landscape mode on 11 x 17 paper. I hope that it works for you. Please let us know if it does.

Dropbox - DSelf_Preamp_v2_FPD.pdf
 
Does a schematic of the I/O board exist somewhere?

Well ...

The answer is "Yes" and "No". The original project IO was 1 x 1 (ie; 1 input and 1 output). There was no switching in of inputs. When builders asked for more inputs I added a simple selector switch that turned on relays as it was rotated.

The details for the original IO PCB is on page #2 of the schematic. The added rotary switch and relays being so trivial, has never been documented.
 
Does the selector switch close the coil circuit on the high side or the low side of the power supply? Not sure if mine is working or not. Will be looking at later tonight. As far as the switch mounting is concerned does it go on the opposite side of the printing on location? if it were the other way around that wouldn't make any difference in operation correct? It having a locator pin and everything.
 
So I'm having issues with the I/O and the selector switch. It doesnt seem to switch through the inputs. There are 5 input relays to switch(XLR input coils are parallel) and the selector switch is 10 positions?? Not sure why. Am I supposed to run 17 volts from the power supply to the terminal block and then jumper. It seems like it is getting power from the main board. I'm not supplying power but I can here relays switch when I connect the IDC's. I'll start there but sure I'll have to supply more details. Anyone have startup issues with the I/O??