Building a Douglas Self design preamp

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Just to offer if anyone is interested, i have spares available for the Preamplifier 2012. Spares such as resistors, capacitors, relays, i.c.'s, potentiometers etc etc.
Place your request here, prices will be promising

Do you have C12 = 10μF 20% 63V, 6.3mm diam., 2.5mm pitch polarized for the power supply?

Depending on shipping to sweden i would be interested in a pair
 
Note!
C12 is a 10uF 20% 63V, 6.3MM diam., 2.5mm pitch.

In Elektor's BOM list it was listed incorrectly with Farnell code 1236680.
Under this number it is actually a Non-Polarised capacitor 10uF 63V.

On page 26 of Preamplifier 2012 (3) C12 is actually a 10uF 63V, and should not be Non-Polarised.

I have some 10uF 100v. Their size are ok.
 
Last edited:
Couple of thoughts:

On one of the other associated forum threads someone posted the files for the front and back panels. The files are to be used with the software "Front Panel Express". You could print the panels and use as a template.

I made high resolution scans of my boards before stuffing them. You are welcome to these files. I also have the Front Panel Express files. Just send me a PM.
 
Hi muskyhuntr,
That mains input, FN9263-4-06 from DigiKey, has a power On/Off switch.
What switch type is the one you've used on your front panel?

Might you have the part number and type number/names for those DigiKey toggle switches you used?

I looked at that EBay link, but those are ON-OFF-ON types, and the cutting hole for those is 15mm.
Ordering from EBay means most supplies from China (quality?) takes at least a month to arrive.

The Elektor toggle switch type used was http://export.farnell.com/multicomp/1ms1t1b5m1qe/switch-spdt-2-0a-250v/dp/9473378?ost=9473378&scope=partnumberlookahead&exaMfpn=true&searchref=searchlookahead&iscrfnonsku=false&ddkey=http%3Aen-EX%2FElement14_Export%2Fw%2Fsearch
But the cutting hole for these are 6.35mm, not 15mm.

So another E-Bay search gave me: -
5Pcs R13 Black 3Pin ON-ON Round Paddle Maintained Toggle Switch 2Position SPDT | eBay
The cutting hole for these are 15mm.

As i mentioned i have a R.S. Components case | PF-19 Ventilated Rackmount Enclosure with Handles, 2U, 84 HP, 245mm Deep | and i believe you have used the same case.

Ideally i would prefer to use the orginal Farnell toggle switches, but this would need the Front Panel Designer files to be amended (not my cup of tea).

The front panel design in post #6 NE 5532 PreAmplifier from Doug Self, Elektor 2012, is clearly for the 15mm DigiKey toggle switches.

I'm really at a loss what's best to do.
 
Last edited:
The power input connector on my pre-amp has a power switch as well as a line filter. Those are the reasons I choose it. The one I posted is the one I used. I have no idea as to what the power switch on the front panel is. It was a part I had on hand at the time.
r13-402 is the marking on the 3 front panel switches. I had originally bought them from DigiKey, but it seems that they are no longer available there. The part I posted was from EBay thru a quick search. Try this one: SCI R13-402 Round 2Pin ON-OFF SPST 2Position Toggle Switch 3A 250VAC | eBay.
As for the front power switch, any 2 position rotary switch capable of handling a few amps at 250V would work. Just look for one that matches your mounting hole.
Note that the chassis I used was an EBay item also, I don't know if the one you are using is the same as mine.

Jim
 
Can builders of this Preamplifier please advise on the interconnecting cable you've used?
I made up the interconnects as twisted pairs (two way) and similar for the three way and four way leads using Harwin M20-1 series header housings and crimps. Wire size was 22AWG of appropriate colours for role. The end result works great and has no issues with crosstalk or hum.

Farnell p/nos for these are:

865606 M20-1060200 2-way housing
865618 M20-1060300 3-way housing
865920 M20-1060400 4-way housing
1022219 M20-118042 crimp 22AWG to 30AWG

Others used coax in place of twisted pairs and reported these were great too.

The lead between the two input board and source selector front panel board is a 10-way flat ribbon cable.

Geoff
 
I too cannot hear any difference between using coaxial cable and twisted pair for interconnects.
I also use twisted pair internally.
I have tried using small diameter coaxial internally but the extra hassle does not seem to bring any benefit.

But I am a stickler for minimising EMI by implementing adequate RF filtering and using LOW LOOP AREA terminations at the cable ends.

My soom to be delivered RTX measurement system may provide some evidence that coaxial is better than twisted pair. But I will have to wait a while to get comparative results.
 
Last edited:
Thanks Geoff for this information

What Co-Ax did you use?

Could you give me the type of Wire size 22AWG, that you used?
I didn't use coax. All wiring (apart from 10-way flat ribbon between front panel source selector switch and input board relays) was twisted pairs / triples with 22AWG wire.

For the black wire, Farnell o/n, manufacturer/n, etc.:
1764928 6713 BK005 AlphaWire Eco-wire, black
For other colours, Farnell o/n varies but AlphaWire p/n just changes the two letter segment of their p/n. e.g. orange wire is 6713 OR005.

For Power feeds between PSU and each board, I used slightly thicker wire and ran them as three wires tightly twisted together. The wire was cheapish stuff from Maplins that I already had in my parts box.

Geoff
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.