The "Muscovite" 6S3P Tube Phonostage - Page 6 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 23rd July 2012, 05:35 AM   #51
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Default Final PSU

The power transformers arrived on Thursday night and Saturday afternoon I started to punch the chassis and mount all of the parts - I managed a little wiring before knocking off to go out to dinner. Today after I got back from ice skating I started wiring in earnest, and was able to complete and debug the power supply over the course of about 8 hrs today/tonight.

The 6BD5GT that I choose to use instead of 6V6/6L6 is a little more fussy than I am used to, and my initial reward for all of this work was relaxation oscillations and some VHF garbage. This was resolved in a few hours along with a bad buzz originating in the reference for the right channel supply. (Don't reference filaments directly to a zener used as a reference - apparently this can result in sufficient leakage current to make the reference noisy)

The design has been running for about 1 hour without problems so I would not consider this fully vetted. Build at own risk and expect some issues to be resolved if you follow this route.

Note that I built two supplies, one for each channel sharing a common raw, but rather well filtered supply. The output voltage is approximately 302V, and output noise and ripple is approximately 700uVrms - the pre-amp is now extremely quiet.

Performance overall seems slightly improved if anything, as I mentioned it is quieter overall, and the tonal balance seems if anything even more neutral than before.

The filament supply is not yet documented, but is conventional LT1084 implementation. (It is fully floating.)

EDIT: Power supply misbehavior root cause was pinned down tonight, I also determined that the filament supply is OK, and spent several frustrating hours before I discovered one of the two 6BD5GT pass tubes was gassy. (This caused popping and all sorts of other bad behavior and was visible on the raw plate supply. The strange violet glow at the base of the tube was the clue as was the occasional muted pop when the B+ came up. Replacing it solved all odd behavior.. I did change R6 to 4.7K which further quieted the screen supply, and is recommended for this reason. Schematic updated 7.25.12
EDIT2: Changed R6 to 6.8K and updated schematic to reflect. Shifted operating points of error amplifiers and dropped screen voltage slightly. 7.29.12 (see revised regulator design later in thread for current implementation 5.12.13)
Attached Images
File Type: jpg DSCN0096_R.jpg (206.9 KB, 411 views)
File Type: png 6BD5GT_PSU.png (72.3 KB, 329 views)
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 23rd July 2012, 11:22 PM   #52
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Here is a picture of the inside of the power supply chassis just before I drilled the holes and mounted the bottom cover plate.

Note that the much simpler (single) supply detailed in an earlier post is a perfectly acceptable alternative to this design as would be one similar to this using the 6V6 instead of the oddball 6BD5 (different pin out)

I will post any further changes I make to the PSU as I "fine tune" the design.
Attached Images
File Type: jpg DSCN0098_cr.jpg (209.8 KB, 393 views)
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 24th July 2012, 03:46 AM   #53
Carlp is offline Carlp  United States
diyAudio Member
 
Join Date: May 2006
Location: A New England
Nice to hear about your progress, Kevin. And thanks for the chance to listen to the Muscovite. I have to say the Muscovite is a beautiful sounding phono pre (even without the new PS), very accurate sounding (i.e. neutral) and simply doesn't get in the way. Which is saying a lot based on the quality and accuracy of the rest of your system! That's not to say it isn't involving, though. It is! Very resolving but no fatigue for me. It's hard to describe as I haven't heard a phono pre like it before, but I like it!

So my question was going to be, if I have 6V6 tubes lying around (I do) is there anything to recommend AGAINST using them - I know you mention some improvements using the 6BD5, but if my system isn't as resolving as yours, will those improvements be likely to be noticeable? Tough question I know. But since I have the 6V6s, I'm likely to use them. Anyway it sounds like you've answered that, so maybe no followup is needed. And from what you've written, the 6V6 shouldn't give me the stability trouble you've had with the 6BD5?

Finally, I'm interested in your filament supply should you choose to post it.

Cheers!
  Reply With Quote
Old 24th July 2012, 04:27 AM   #54
Carlp is offline Carlp  United States
diyAudio Member
 
Join Date: May 2006
Location: A New England
Too late to edit my last post, but re: the filament supply, I know you've posted one, including the BOM, but it seems like it has changed some and I haven't tried to follow closely enough to make adjustments to the schematic and BOM.
  Reply With Quote
Old 24th July 2012, 04:55 AM   #55
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Hi Carl,
Regarding the filament supply I recommend the design I originally posted - the only change I made of consequence was to use a 22000uF cap instead of the 10000uF and I do not believe this actually significantly improved the performance of the supply.

With regard to using the 6V6 I think this is an excellent choice and in fact was what I was using in the PSU that powered it when you were here. I think all of the benefits of the current design will be realized with the 6V6 in place of the 6BD5, and to be honest I need to spend a little more time with this tube to really trust it. The way I would put it is I purchased 5 NOS 6BD5GT and the matched pair I bought had one defective tube, so the failure rate out of the box is high IMLE.. We'll see how the rest turn out.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 24th July 2012, 11:45 PM   #56
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Spending some serious listening time tonight, I'm relatively satisfied with the performance at this point, will probably tweak the power supply a bit further once the dust has settled. (We're talking weeks) It's stable and the pre-amp is now vanishingly quiet and sounds good - so the supply has accomplished the design goals.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 25th July 2012, 01:33 AM   #57
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Some minor changes to the power supply since the last photograph. Removed and moved a pair of Clarity SA 4.7uF caps to the phono stages, replaced the 0.1uF feedback caps with Clarity SA and beefed up the grounding to the references and feedback reference points..

No problems so far, one minor thump due to a nearby lightening strike.. (Yeah I just generally ignore the weather outside, figure worst case I'll need some new power transformers.. ) Most of the analog gear runs on balanced power from a 600Va medical grade isolation transformer. The GM70 power amps don't like my 1kVa medical isolation transformer very much so they run direct.
Attached Images
File Type: jpg W_ClarityCapFB.jpg (220.6 KB, 346 views)
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 25th July 2012, 05:40 AM   #58
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
It's pretty late, I guess after nearly six hours of continuous operation I'm out of the woods.

The improvements with the stereo power supply are more significant than I expected. There is certainly more depth, and additional detail - neither were lacking before, and the sound is not the least bit analytical.

I'm rediscovering some familiar recordings, somehow this pre-amp allows me to see a bit further into recordings than any of my previous efforts.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 25th July 2012, 02:35 PM   #59
Carlp is offline Carlp  United States
diyAudio Member
 
Join Date: May 2006
Location: A New England
Quote:
Originally Posted by kevinkr View Post
somehow this pre-amp allows me to see a bit further into recordings than any of my previous efforts.
And THAT is what I look for in all my equipment...that is, without it getting too dry or analytical. It's a fine line and I don't quite understand what qualities in the gear allow such clarity without the downsides, but maybe your goal of accuracy is the answer?

I hope I'll have another chance to listen. But off to the wilds of Canada for a while now.
  Reply With Quote
Old 25th July 2012, 05:05 PM   #60
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Carl, have fun in Canada! Probably will do something between now and the audio fest this fall.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  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
Phonostage with tube moving coil legarem Tubes / Valves 4 13th October 2011 04:42 PM
freaky new phonostage Vinylsavor Tubes / Valves 35 30th November 2010 07:30 AM
Russian 6S3P=WE417? huskydawg9 Tubelab 8 24th March 2010 01:32 PM
rjm 2 tube phonostage hacknet Analogue Source 6 10th April 2006 05:27 AM
Pearl phonostage Mark777 Pass Labs 0 6th July 2003 11:18 AM


New To Site? Need Help?

All times are GMT. The time now is 07:44 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