Help on Magnavox Paraphase (Gabevee?) - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 Search this Thread
Old 4th March 2006, 09:38 AM   #1
diyAudio Member
 
Join Date: Dec 2005
Location: Singapore
Default Help on Magnavox Paraphase (Gabevee?)

Hi!

I am trying to build Gabevee's Maggie from http://members.tripod.com/~gabevee/maggie.html In fact, I had got the 6EU7 from him 2 weeks ago. But now I cannot seem to be able to contact him by e-mail, is it changed? Anyone has any idea?

Anyway, I have finished building the amp. However, I have a problem, there is a loud feedback sound in the speakers. Loud High frequency in one side, and a not so loud lower frequency in the other. This is gone if I disconnect the feedback loop. Does anyone know what's wrong? Without the feedback, the sound sounds funny, the bass is weak too.

I followed his schemetics exactly except for one of the coupling caps which is 0.047 instead of 0.04. Of course our irons are probably different.

Also my B+ is very high at 420V, so I used a 1K 50W (that's what I have at the moment) to drop the B+ to about 280V. I'll probably have to get a variable resistor or a lower valued one to get his specified 335V.

Appreciate any help from anyone with experience with this schematic or anyone at all.
  Reply With Quote
Old 4th March 2006, 03:18 PM   #2
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
hi,

I was fortunate enough to repair one of these paraphase amps before. are you sure that there is a 390 ohm resistor connected to ground and to the 4.7K cathode resistor of the input tube?

you can also try reversing the connections of your opt tranny to the plate of the 6bq5 tubes.

hope this helps.

JojoD
  Reply With Quote
Old 5th March 2006, 08:48 AM   #3
diyAudio Member
 
Join Date: Dec 2005
Location: Singapore
JojoD thanks!

That's exactly it!! I switched the OPT connections and everything is OK! Now music is playing...
  Reply With Quote
Old 5th March 2006, 01:52 PM   #4
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
hi,

you could play around with the cathode resistor to vary the 6bq5's plate current, at least you only have one resistor to play around with.

enjoy!
  Reply With Quote
Old 5th March 2006, 03:06 PM   #5
diyAudio Member
 
Join Date: Dec 2005
Location: Singapore
Well yeah I may... What's the effect of lowering/raising the resistor value?
  Reply With Quote
Old 6th March 2006, 04:49 AM   #6
diyAudio Moderator
 
JojoD818's Avatar
 
Join Date: Mar 2003
Location: searching...
increasing the value decreases the plate current and vice versa. I think the author tried a value around 100-150 ohms.



cheers
  Reply With Quote
Old 26th June 2006, 04:50 AM   #7
amp_guy is offline amp_guy  United States
diyAudio Member
 
Join Date: Oct 2004
Location: utah
Default maggie copy

hi pengboon iam glad toy are enjoying your new paraphase
amp. I have an original maggie amp which continues to amaze
everone that hears it . BTY Ihave a schematic that I reverse engineered from it if anyone wants Ican post it . (circuitmaker 2000 pro format or jpg)
Iam considering builing another in a nicer package using iron from edcor.
Happy listening
  Reply With Quote
Old 26th June 2006, 05:02 AM   #8
diyAudio Member
 
Join Date: Dec 2005
Location: Singapore
Sure, let's take a look at it! How different is it from Sam's photofact?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Trouble with a paraphase PI Turbo7MN Tubes / Valves 17 26th May 2007 03:07 AM
Gabevee's SS tube-like preamp needtubes Solid State 24 27th April 2006 10:13 AM
Paraphase Splitter - why is it unpopular? ray_moth Tubes / Valves 9 10th March 2006 01:50 AM
Gabevee's Maggie (MAG1515) percy Tubes / Valves 2 15th September 2004 12:43 AM


New To Site? Need Help?

All times are GMT. The time now is 01:46 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2