Custom Preamp Project

[glasman]

Here are few pictures of a custom preamp I constructed for a customer. It is based around #102 and turned out pretty nice.

A lot of stuff in a small (8" deep) package. Dual trannies for power VCC (series configuration). with US and europeon voltage capability.

[glasman]

I had a small hum that I had corrected by isolating the input jack and grounding it to the preamp star point.

[dcribbs1412]

Cool Gary
gotta say the scope shots are cool, before and after shots of the hum on the scope are impressive
Makes me want to get one but priced out of league.

D

[glasman]

Cool Gary
gotta say the scope shots are cool, before and after shots of the hum on the scope are impressive
Makes me want to get one but priced out of league.

D

Probably even worse, those are on a stand alone spectrum analyzer, kinda pricey, but well worth the cost.

There are cheap, PC based ones that will do the same work at a fraction of the cost of an Agilent, HP or Ono Sokki like I use.

Gary

[martin manning]

Looks very nice! I'm guessing you have a low-Z CF-driven output and a high-Z plate-fed output?

[glasman]

Looks very nice! I'm guessing you have a low-Z CF-driven output and a high-Z plate-fed output?

You are correct, simple is good lol. Anyway, I just used a set of Zingaro boards and cut the Mainboard to eliminate the loop recovery, reverb and power amp section.

I will cut the reamining board again, to extricate the the reverb section for another project I have. Doing the Two Rock thing lol.

Gary

[glasman]

Jeez, how bad of me to forget the top down shot, I am sure that a few builders would love to replicate it lol.

[glasman]

To clarify for Martin, it is close to the standard CF section, I just rebias that section to get more headroom. The standard values suck and it will clip in a heartbeat.

[glasman]

Front panel closeup.

I generated these panel in house on my new to me epilog Helix laser.

[glasman]

This piece was commisioned by Rick Derringer of all people.

[Duble]

This is similar to what I did, but i mounted the boards Dumbleator style.

Preamps can be tough with noise!I had to mess around with the grounding for quite a while. Shopping for a PCB house now for mine. I also did a passive and buffered output, with a full loop. Mine looks much more crude Yours looks really great Gary!

I used a full wave bridge as I'm not a fan of voltage doubler's. Had Heyboer make me a PT with a 260v secondary in an R2C frame.

[glasman]

This is similar to what I did, but i mounted the boards Dumbleator style.

Preamps can be tough with noise!I had to mess around with the grounding for quite a while. Shopping for a PCB house now for mine. I also did a passive and buffered output, with a full loop. Mine looks much more crude Yours looks really great Gary!

I used a full wave bridge as I'm not a fan of voltage doubler's. Had Heyboer make me a PT with a 260v secondary in an R2C frame.

Not too different, my transformer are both 260V with an additional 14 volt secondary. I series both secondary's, the 520V is running to a full wave rectifier, the 28volts is running to a bridge and develops the 12Vdc for the filaments and 15V for the relays. The filtering on the power supply board is a bit over the top lol.

[lovetone]

Front panel closeup.

I generated these panel in house on my new to me epilog Helix laser.

Looks great what material did you use for the face plate?

[DenDanger]

This piece was commisioned by Rick Derringer of all people.

Very nice and neat. Classic look. Super job of fitting 8 lbs in 5 lb box.
Rick Derringer is one of my favorite guitarists. (Very underrated)
I don't think I've seen him use rack mount gear.
I'm sure he will enjoy it.

Denny

[martin manning]

To clarify for Martin, it is close to the standard CF section, I just rebias that section to get more headroom. The standard values suck and it will clip in a heartbeat.

Thanks. That means you have an unused triode?

Super low-ripple power supply and DC filaments are to be expected for a piece of gear like this.