Vinyl Savor 6CB5A SE Amps? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 7th October 2015, 03:05 PM   #1
diyAudio Member
 
Join Date: Aug 2008
Default Vinyl Savor 6CB5A SE Amps?

I built this amp over the weekend using mostly Vinyl Savor's schematic. I swapped the rectifiers out for 6C33s and switched the driver to 6CG7s.

I ended up with 420V B+ on the 6CB5A tube plates. Is the additional 20V of any major consequence?

I ended up with 180V on the plates of the 6CG7s and 5V on the cathodes leaving the 1K cathode resistor and 47K plate load resistor.

I'm mostly concerned with whether or not I need to add another stage to drop a few volts to my PS.

Thanks!
Attached Images
File Type: jpg 6CB1.JPG (123.3 KB, 655 views)
File Type: jpg 6CB2.JPG (121.6 KB, 634 views)
File Type: jpg schematic 6CB5A .jpg (112.4 KB, 651 views)
  Reply With Quote
Old 7th October 2015, 03:09 PM   #2
Stixx is offline Stixx  Germany
I am
diyAudio Member
 
Stixx's Avatar
 
Join Date: Sep 2003
Location: Southern Germany
Nice work for a weekend.
__________________
www.original-ton.net
  Reply With Quote
Old 7th October 2015, 04:01 PM   #3
diyAudio Member
 
Join Date: Aug 2008
Thank you! I've been at this a while, so I have a system for building and machining chassis.

I'm only worried about the B+ because these are run in triode and I know they are being pushed a little in this circuit.

Blair
  Reply With Quote
Old 7th October 2015, 04:40 PM   #4
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi!

Nice build!
How much current do you have through the 6CB5A? You get that by checking the voltage on the cathode resistor. As long as plate dissipation does not get too high you should be fine.
Make sure the plate does not show any red spots. If plate dissipation gets too high you get some dull red glow on the plates. In that case dial the voltage back or increase the cathode resistor. In my experience the 6CB5A is quite tough.

The input sensitivity will be lower with the 6CG7. If your preamp provides enough voltage to drive it to full power it should be fine. I selected the 6N7 to get a decent input sensitivity.

For the 6CG7 I would use a different plate resistor, something like 27k. Did you wire both halves in parallel?

Thomas
__________________
http://vinylsavor.blogspot.com/

Last edited by Vinylsavor; 7th October 2015 at 04:45 PM.
  Reply With Quote
Old 7th October 2015, 04:52 PM   #5
diyAudio Member
 
Join Date: Aug 2008
Hi Thomas!

Thanks for the note about the build! I have 420VDC on the plates, and ~73V on the cathodes. The plates have no glow after two hours of playing.

It definitely needs a little more push to get it up to volume, and I may end up swapping out the driver tube to something with a little more gain. Maybe a 12AT7 unless someone has another 9 pin suggestion that would be better.

If I swap out the plate resistor to 22K, does it need to be 10W like the 47K? That's the biggest driver tube plate load resistor I have ever seen. I usually use 1-2W. I only used 1/2 the 6CG7.

Thanks!

Last edited by deicide67; 7th October 2015 at 05:08 PM.
  Reply With Quote
Old 7th October 2015, 05:14 PM   #6
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi!

You should be fine then!

A 5W resistor would do as well. I like to derate resistors significantly

I wouldn't use the 12AT7. It is quite non-linear and that won't work well in such a NFB design.

With the 6N7 about 2V RMS is needed at the input to drive the amp to full power, With the 6CG7 you will need more than 3V.

Thomas
__________________
http://vinylsavor.blogspot.com/
  Reply With Quote
Old 7th October 2015, 05:26 PM   #7
diyAudio Member
 
Join Date: Aug 2008
Great! Thank you, Thomas!
  Reply With Quote
Old 7th October 2015, 05:42 PM   #8
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi!

I would recommend to change the plate resistor if you keep using the 6CG7. You wrote that you currently have 5V on it's cathode. Since you need 3V RMS, which is almost 5V peak, you have no headroom. As such the driver probably dominates the sound of the amp. It is good to have 6dB headroom. So I would reduce the plate resistor and maybe parallel the 6CG7 halves. Then play a bit with the cathode resistor.

Thomas
__________________
http://vinylsavor.blogspot.com/
  Reply With Quote
Old 7th October 2015, 05:52 PM   #9
diyAudio Member
 
Join Date: Aug 2008
Hi Thomas,

I already ordered some 5W 27K resistors. You think I will be OK with the 6CG7 if I parallel, swap the plate resistors and maybe drive them a bit harder?

Thanks!
  Reply With Quote
Old 7th October 2015, 05:58 PM   #10
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
If the low gain is ok in your system, yes you can make it work.
Try to get an op point with about 10V on the cathode. That gives 6dB headroom.
Then let your ears judge. If you like the sound, you are ok ;-)

Thomas
__________________
http://vinylsavor.blogspot.com/
  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
Vinyl Savor's Octal 6GL7 preamp? deicide67 Tubes / Valves 16 28th January 2016 04:07 AM
SE 6CB5A amp with 6N7 driver Vinylsavor Tubes / Valves 75 17th March 2014 08:30 PM
Many different Vinyl Disc/LP Clamper-Vinyl Record Stabilizer/Clamper for Sound Impr. tiefbassuebertr Analogue Source 3 7th November 2013 08:18 AM
TV7 tester problem with 6CB5A tube NewMountain Tubes / Valves 0 6th July 2013 05:53 AM
cheap SE amps siu sin man tho Tubes / Valves 14 13th May 2003 09:49 AM


New To Site? Need Help?

All times are GMT. The time now is 05:06 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2