Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki 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

DC coupled single ended cathode follower 6SJ7/6V6 amp project
DC coupled single ended cathode follower 6SJ7/6V6 amp project
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 21st July 2019, 11:41 PM   #41
45 is offline 45  Italy
diyAudio Member
 
45's Avatar
 
Join Date: Dec 2008
Location: UK
Quote:
Originally Posted by Dinolobe View Post
I guess i’ll have to find another ocatal/two valves circuit with 5k OPTs to fill my enclosure, wich has already been drilled. The other version of the circuit, the RC coupled one, was still tempting, but the power figures are so low for such an investment in time. 1250v is just wrong for such a low power output !!

Since my chassis is ready to receive this circuit topology, and because I can’t find a suitable two valve all octal single ended schematic for a 6v6gt, I think that I will assemble the rc coupled version of the bates amplifier. That will satisfy my curiosity and i’ll be able to measure it’s output power in real world.

The other option would be to tame myself and take the time to design something else that would fit the bill. I don’t have a computer that can run the tubecad programs and don’t know how to use LTspice so I would have to do it "by hand", unless you guys know of a circuit that I could use. Thanks to everyone who answered this thread, it’s been really instructive !
You don't necessarily need to find another tube. The easy solution is that you change the output stage from cathode follower to common cathode. It can be done in several ways. The simple one is RC coupling of input stage to the 6V6 and self-bias for the power tube with RC network. Can do triode or pentode with some feedback. If the gain of the input pentode is too much and don't want feedback you can connect it in triode mode as well. Gain will be similar to what you get from 6J5/6SN7 family.
  Reply With Quote
Old 22nd July 2019, 01:04 AM   #42
jhstewart9 is offline jhstewart9  Canada
diyAudio Member
 
jhstewart9's Avatar
 
Join Date: Apr 2013
Location: near Toronto
The attached very early 6V6 data sheet shews triode operating specs. So in the RCA lab under ideal conditions the typical triode connected 6V6 manages one watt powered by a lab supply of 250V on the plate. Multiply that by something like 85% efficiency of a SE OPT, so less than a watt.

It does a little better with a higher voltage supply.

There are several modern power triodes used as vertical amplifiers in TV that will do quite a bit better. But in a CF cct needs a rather large drive.

A cunning devil cct would bootstrap the drive using a PP OPT. But why bother, there are better ways.
Attached Files
File Type: pdf 6V6 Radiotron.PDF (572.0 KB, 31 views)
  Reply With Quote
Old 22nd July 2019, 02:10 AM   #43
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
Quote:
Originally Posted by 45 View Post
The obvious solution to that circuit has already been posted by Tubelab. ....
"class H design with modulated supply rails"
"floating buck converters"

?? This looks like it was designed and assembled by a practicing cell-phone engineer and technician.

It is very not-1949, not very nostalgic (unless you remember burning your first 6336), and not real scrap-box friendly (unless you salvage at Motorola).

It's a great design!! But not what this thread is about.
  Reply With Quote
Old 22nd July 2019, 02:19 AM   #44
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
> very early 6V6 data sheet

Thanks.

We see around 5W in pentode, 1.65W in triode.

_IF_ we could drive a cathode follower HARD, we'd get the same powers at lower THD. (However making a driver deliver >125V peak at <5% THD requires heroic engineering.)
Attached Images
File Type: gif 6V6-pent-tri.gif (19.7 KB, 124 views)
  Reply With Quote
Old 22nd July 2019, 09:28 AM   #45
45 is offline 45  Italy
diyAudio Member
 
45's Avatar
 
Join Date: Dec 2008
Location: UK
Quote:
Originally Posted by PRR View Post
"class H design with modulated supply rails"
"floating buck converters"

?? This looks like it was designed and assembled by a practicing cell-phone engineer and technician.

It is very not-1949, not very nostalgic (unless you remember burning your first 6336), and not real scrap-box friendly (unless you salvage at Motorola).

It's a great design!! But not what this thread is about.
Everyone has his opinion. I don't care about nostalgic stuff. My point is that he has gathered stuff and wants to use it.
  Reply With Quote
Old 22nd July 2019, 10:28 AM   #46
Dinolobe is offline Dinolobe  Canada
diyAudio Member
 
Join Date: Jun 2018
Quote:
Originally Posted by 45 View Post
Everyone has his opinion. I don't care about nostalgic stuff. My point is that he has gathered stuff and wants to use it.
Exactly. It doesnít even have to be this circuit at all !

Quote:
It's a great design!! But not what this thread is about.
If I had those parts laying around, why not. Everyone doesnít have the same background as Tubelab
  Reply With Quote
Old 22nd July 2019, 12:58 PM   #47
Tubelab_com is offline Tubelab_com  United States
diyAudio Member
 
Tubelab_com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
It is very not-1949, not very nostalgic.......It's a great design!! But not what this thread is about.
The class H design line was not posted for the purpose of someone else's duplication. The information about the cathode follower amp it contains, and the "plain jane" stand alone cathode follower amp that was designed for it (also linked) is pertinent to the request for a two octal socket cathode follower design. The input and voltage gain stages are one octal bottle (6EM7) and the output tube could be just about any triode wired octal TV sweep tube. A 6CD6 ot 6DN6 would work.

Quote:
I canít find a suitable two valve all octal single ended schematic for a 6v6gt........I could also order my parts and populate the Tubelab SSE board that I have received two months ago. It may be more logical to put in use the big edcor OPTs
I don't think any of the 6V6 cathode follower circuits found with two octal tubes are going to work well on modern speakers and outperform a conventional design. A design similar to the Fender Champ 5C1 with some added plate to plate feedback should work far better. Convert the 6SJ7 to cathode bias and add a resistor between the two plates for feedback.

The SSE works fine with 6V6's if you jumper across the 10K resistors in series with the CCS chips, and use a power transformer that makes about 275-0-275 volts. It however will only make about 2 watts in triode mode, and pure pentode using ANY tube will need feedback to sound good on most speakers.

If you already have the big Edcor OPT's (CXSE) it would be wise to use them with something that can take advantage of their size. I used the small XSE OPT's in my 6V6 based SSE with a cheap Allied 6K56VG power transformer. This combination makes a nice sounding 2 watt amp.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 22nd July 2019, 01:42 PM   #48
Dinolobe is offline Dinolobe  Canada
diyAudio Member
 
Join Date: Jun 2018
Quote:
Originally Posted by Tubelab_com View Post
The class H design line was not posted for the purpose of someone else's duplication. The information about the cathode follower amp it contains, and the "plain jane" stand alone cathode follower amp that was designed for it (also linked) is pertinent to the request for a two octal socket cathode follower design. The input and voltage gain stages are one octal bottle (6EM7) and the output tube could be just about any triode wired octal TV sweep tube. A 6CD6 ot 6DN6 would work.



I don't think any of the 6V6 cathode follower circuits found with two octal tubes are going to work well on modern speakers and outperform a conventional design. A design similar to the Fender Champ 5C1 with some added plate to plate feedback should work far better. Convert the 6SJ7 to cathode bias and add a resistor between the two plates for feedback.

The SSE works fine with 6V6's if you jumper across the 10K resistors in series with the CCS chips, and use a power transformer that makes about 275-0-275 volts. It however will only make about 2 watts in triode mode, and pure pentode using ANY tube will need feedback to sound good on most speakers.

If you already have the big Edcor OPT's (CXSE) it would be wise to use them with something that can take advantage of their size. I used the small XSE OPT's in my 6V6 based SSE with a cheap Allied 6K56VG power transformer. This combination makes a nice sounding 2 watt amp.
I intended to use the edcor cxse OPTs with my SSE board and 6550s. This threadís purpose was only to find a simple/fun way to use some parts I have laying around, and maybe experiment with something different and learn along the way.

I have a Tek PT with 3 150V secondaries, 2 smallish SE 5k:8 OPTs (antique supply P-T31) and a reasonable stash of tubes. (Pretty much all common noval preamp tubes in different flavors and a few different sets of power tubes like el84, el34, 6v6, 6550...) from what I remember of your cathode follower design, wouldnít I need OPTs with a 600 ohm primary ? I would gladly try your design if itís possible to make it work with the transformers I already have, but if not, I would prefer to use a circuit that better fits those parts. Even if itís a very interesting circuit ! I donít mind buying some tubes I donít already have though.

I havenít thought of the fender circuit. It could be an interesting project too ! Iíve read that you test your amps by playing guitar through them. Could it be possible to build the amp in order to serve both purposes ? Is it just a matter of input/output connectors or there is something else that needs to be done ?

Edit : volume pot of the 5c1 is between the two stages. My guess is that the instrument needs a fixed input impedance, but I may be wrong. Could I use a switch or relay to bypass it, and put rca input connectors in parallel with the 1/4" jack, bypassing the 75k resistor in the input at the same time ?
Attached Images
File Type: png C9AB4EC4-782B-49ED-B5B5-F6647120ADF2.png (119.1 KB, 100 views)

Last edited by Dinolobe; 22nd July 2019 at 02:01 PM.
  Reply With Quote
Old 23rd July 2019, 01:30 AM   #49
rongon is offline rongon  United States
diyAudio Member
 
rongon's Avatar
 
Join Date: Jul 2009
Location: Across the river from Rip's big old tree...
DC coupled single ended cathode follower 6SJ7/6V6 amp project
Stirring up the waters here, but this might be a good type of design to shoot for in a 2 pentode SE amp.

Audio Asylum Thread Printer

Click the image to open in full size.

That uses EF184 and EL84, but maybe could be reconfigured for 6SJ7 and 6V6GT.
--
  Reply With Quote
Old 23rd July 2019, 02:54 AM   #50
leadbelly is offline leadbelly  Canada
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
I wouldn't recommend building the Champ circuit as is. Grid leak bias is probably a bad idea in a hifi chain, your CDP output could probably exceed the input headroom and be clipped. The coupling caps are also on the small size as low bass is being intentionally filtered. Also, building it as drawn would result in enough hum to drive me crazy, as a little hum is no big deal in a guitar amp.
__________________
Wise men speak because they have something to say; Fools because they have to say something. Plato

Last edited by leadbelly; 23rd July 2019 at 02:56 AM.
  Reply With Quote

Reply


DC coupled single ended cathode follower 6SJ7/6V6 amp projectHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Transformer coupled cathode follower power? Sodacose Tubes / Valves 28 29th December 2016 04:55 PM
DC Coupled Cathode Follower Questions steeledriver Instruments and Amps 22 1st April 2016 03:57 PM
A case of direct coupled cathode follower Mosquito Tubes / Valves 62 9th June 2014 02:06 PM
DC coupled cathode follower driving me nuts funk1980 Tubes / Valves 12 9th November 2011 05:48 PM
A Direct-Coupled Amplifier with Cathode Follower 6V6 livingdeliberately Tubes / Valves 6 31st March 2011 06:41 PM


New To Site? Need Help?

All times are GMT. The time now is 06:36 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki