Go Back   Home > Forums > >

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Great American Sound Head Amp
Great American Sound Head Amp
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools
Old 26th November 2020, 05:28 PM   #11
johnfalc is offline johnfalc  United States
diyAudio Member
 
Join Date: Mar 2009
Interesting information, thanks.

I have found a schematic for what is titled on the engineering drawing "PHONO CIRCUIT (THOEBE, THAEDRA)" which, given its 47K ohm loading resistor at the input, is obviously for MM cartridges. This uses dual differential BJTs and is clearly quite different from what is in my Thoebe.

The Thoebe I have here does not have the DD BJT MM photo circuit; rather it has (as you point out) the MC 324D adjustable gain board from a Thaedra II with its 1.2 ohm series R1 and 1K ohm R2 loading resistor - suitable for a MC cartridge (and, of course, it includes RIAA compensation).

So ... it appears that converting a Thoebe between MM and MC is as simple as swapping boards.

Perhaps this is moot for me in that I may not use the Thoebe for vinyl at all, except to test it with an Ortofon MC20. I'm considering it and the associated Grandson likely for use in a guest bedroom or as a shop setup.

A friend gave these (and a pair of AR-2ax speakers) to me. I originally declined the gift as I have too much stuff already but, when he said he'd take it all to landfill I recanted and accepted them. Anyway, it is a fun project and takes little in expense to get it all running as new (I've already replaced the woofer surrounds and will have the tweeters repaired).

Fun for some nostalgic reflection though, since I met Jim B. several times when he was with SAE.
  Reply With Quote
Old 26th November 2020, 06:17 PM   #12
llwhtt is offline llwhtt  United States
diyAudio Member
 
Join Date: Jun 2008
Location: SoCal
You'll have to find a MM board to use in Thoebe if you want to use a MM cartridge. I have several versions of line stages and PS/regulator boards but no spare MM or MC boards. They come up on that auction site every now and then.

I got to meet JB shortly before he passed away, he'd mellowed out quite a bit since you saw him at SAE. I have soooooo many questions for him but it's too late.

Craig
  Reply With Quote
Old 26th November 2020, 08:08 PM   #13
johnfalc is offline johnfalc  United States
diyAudio Member
 
Join Date: Mar 2009
I was lucky, I think, to be so involved in audio during what I consider the best of times, basically from 1969 through 1982 or so. Travels around the country and to the Audio Fairs in Tokyo were among the highlights. I'm fortunate to still be in touch with dozens of folks who also worked for Pacific Stereo and CBS.

Good gear and plentiful material plus relatively unaltered hearing mean I can continue to enjoy the music ... that's what really counts.

Cheers and Happy Thanksgiving, John
  Reply With Quote
Old 29th November 2020, 12:36 AM   #14
johnfalc is offline johnfalc  United States
diyAudio Member
 
Join Date: Mar 2009
Parts came in for the Grandson so that part of the duet is complete. Once all back together (except for the case) I discovered one of the meter level controls was defective. Thankfully I had some good multi-turn 2K pots to use so I installed those and calibrated the meters.

Mouser order for the Thoebe caps is due on Monday.

Grandson measures very well, distortion and noise is mostly at the limits of my HP 339. I look forward to auditioning the two pieces together once I've finished the Thoebe.

Thanks again for your input.
  Reply With Quote
Old 29th November 2020, 01:43 AM   #15
pcb121055 is offline pcb121055  United States
diyAudio Member
 
Join Date: Sep 2008
This is such a treat to see GAS chatter! I loved that stuff. I was a salesman for a GAS dealer in the late seventies and bought a Ampzilla II, a Goliath, and a Sleeping Beauty. Lost the Ampzilla having sent it in to the factory to have a channel repaired and was told they went out of business and couldn't get it back. So sad. Anyway, thanks much for the Goliath info
  Reply to this post

Reply


Great American Sound Head AmpHide this!Advertise here!
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Great American Sound Thaila 2 Setup Procedure gasgeek Analog Line Level 4 12th October 2015 03:36 PM
128w 8ohms X 2 amp, sound nice, great amp space2000 Solid State 58 28th February 2015 07:22 PM
Great American Sound Thalia 1 Service Info gasgeek Analog Line Level 2 19th February 2015 10:30 PM
FS Gainclone Great Chassis, Potted toroidal, great sound PHilgeman Swap Meet 4 2nd May 2006 02:20 PM
MJ head-amp- how does it sound? Simpleton Tubes / Valves 1 8th September 2005 11:18 PM


New To Site? Need Help?

All times are GMT. The time now is 02:55 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki