Who best to build a power supply for this preamp?

bigbajo60 · Post by **bigbajo60** » Sun Oct 08, 2006 10:48 pm

I'd like to pick the collective brains of the tube tech forum regulars.

I came across a little gem of a Groove Tubes preamp (MP-1) for just $25. In researching it, I read that in it's day, it was considered a most excellent bass pre/DI. It utilizes one 12AX7 and one 12AT7 tube. I got it for just $25, because it came without it's power supply, which originally connected to the pre via a mini 9-pin D-connector. I can email a few pics to any interested parties for analysis' sake. Or maybe one of you can resize the pics for me to post in the thread... anyway;

I've got three questions for you.

1st - How difficult it would be to build a proper power supply for it?

2nd - Technological advances being what they've been since this unit was built, can a more modern (read: smaller; toroidal) power supply be internally installed?

3rd - Who best to perform this work?

Thanx for the neural activity!

doctorwho · Post by **doctorwho** » Mon Oct 09, 2006 12:15 pm

I'd start by e-mailing Groove Tubes' tech support (e-mail address is at the bottom of the page here: http://www.groovetubes.com/) and ask (1) whether a replacement power supply is available, and (2) whether a schematic of the power supply is available. With a schematic, anyone with reasonable electronics knowledge and skill can construct one.

bigbajo60 · Post by **bigbajo60** » Mon Oct 09, 2006 12:33 pm

Yeah, I did that a little more than a month ago... and I was initially impressed by a follow-up phone call someone from GT placed to me the next Monday after my Friday email.

The young man on the phone was very nice, and stated that I had a very nice older piece of GT kit on my hands that could easily be gotten up and running. The guy then said that he'd check their shop area for possible compatible power supplies, but he didn't think he'd run across anything. Finally, he said that he'd be emailing me a copy of the schematic as soon as he could find it in the GT archives, but that I should also keep an eye out for these power supplies on eBay... usually in a set with one of their early tube mics.

As I said... that was about a month ago, and two follow-up emails have gone unresponded to. I will continue to exercise patience, though... especially since that's just about the only exercise I get.

doctorwho · Post by **doctorwho** » Mon Oct 09, 2006 1:26 pm

If the reply was from a personal e-mail address at the company, I'd once again e-mail the original address (the general tech support mailbox) - if the person left the company, went on sick leave, etc., your messages might be "falling on deaf ears".

Archived material is often not easy to find - a former colleague inquired about a manual for an old pump. The U.S. rep had to request info from the European parent, and it took them about two weeks to find the original manual in their archives. In another case, a different colleague inquired about a manual for a Hitachi spectrofluorometer. When he was told that it would cost $195 for a copy, he balked; a few months later, the manual was no longer available.

rick32559 · Post by **rick32559** » Mon Oct 09, 2006 3:27 pm

There are some excellent websites available for this. www.ampage.com had plenty of links and try 18watt.com this should get you started in the right direction.

rick32559 · Post by **rick32559** » Mon Oct 09, 2006 3:45 pm

Sorry its ampage.org

doctorwho · Post by **doctorwho** » Mon Oct 09, 2006 8:46 pm

I did a generic Yahoo search but did not find any concrete leads to that specific schematic.

bigbajo60 · Post by **bigbajo60** » Mon Oct 09, 2006 9:51 pm

I've refreshed my request for the schematic at the Groove Tubes Service site, so lemme start holding my breath...

...*GASP*!!!

...on second thought, I'll just cross my fingers.

jnbass · Post by **jnbass** » Mon Oct 09, 2006 10:59 pm

Hows about Aspen Pittman's book(s)?

Got both of 'em-will check it out

jnbass · Post by **jnbass** » Mon Oct 09, 2006 11:23 pm

no deal-only the Studio 220 schematic

bigbajo60 · Post by **bigbajo60** » Tue Oct 10, 2006 5:20 am

Thanx to everyone who's jumped on board this thread.

Involvement and participation... that's why I love this place!

Anyways (and I know I shouldn't, but)... assuming that I get my hands on that schematic, is there a particular person or shop that any of you have dealt with that you'd trust with the job of building the power supply for this pre?

Perhaps one of you, even?

ken_j · Post by **ken_j** » Tue Oct 10, 2006 7:06 am

Try here; http://www.schematicheaven.com/

bigbajo60 · Post by **bigbajo60** » Mon Oct 16, 2006 12:53 am

Ok... an update about the schematic;

I GOT IT!

My sincere thanx to Sam at GT for his diligence and professional attitude!

Now to show the schematic to an engineer friend of mine to see if he'd like to take the project on. As a Plan B though, any suggestions as to who else might be able to build the PS for me?