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DC coupled single ended cathode follower 6SJ7/6V6 amp project
DC coupled single ended cathode follower 6SJ7/6V6 amp project
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Old 18th July 2019, 11:57 AM   #21
Dinolobe is offline Dinolobe  Canada
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Maybe I could also ask you guys what it would take to make the output stage work as itís intended. I am ready to give up the dc coupling since it seems to be the most limiting factor. Iíll re read the articles about the cathode follower output stage on tubecad since it is the most reliable and extensive information source about it.

By the way, the tektronix power transformer I intend to use has many different HV secondaries, so that could be useful to make the driver stage swing higher than the output stage. All this discussion has been really informative for me since iím tackling something that is a lot deeper into tube circuit than what iíve done before. I thank you all guys !!

Quote:
Originally Posted by DF96 View Post
You could make a simple SE. It won't be hi-fi, but it could make pleasant noises.
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 that are waiting in their boxes
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Old 18th July 2019, 01:58 PM   #22
Sodacose is offline Sodacose  United States
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Quote:
Originally Posted by Dinolobe View Post
Maybe I could also ask you guys what it would take to make the output stage work as itís intended. I am ready to give up the dc coupling since it seems to be the most limiting factor.
You're on the right track of investigation with forgoing the DC coupling.

Also read here:

Cathode Follower | Tubelab

Because you've already got the octal sockets, two stages of 6SN7 (maybe choke loaded) could also be a solution to get the voltage swing you're looking for.
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Old 18th July 2019, 04:26 PM   #23
Dinolobe is offline Dinolobe  Canada
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I have quite a nice stash of tubes and sockets so iím not limited to the octal ones. The reason why I got into tube amps is that someone gave me all his material for building guitar amps, so I started out with a lot of parts. It kinda helped !!

Tubelab_com : your cathode follower amp is very interesting ! If you have any new informations, I would be more than happy to learn more about it !
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Old 18th July 2019, 08:34 PM   #24
pcan is offline pcan  Italy
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DC coupled single ended cathode follower 6SJ7/6V6 amp project
The Raymond H. Bates circuit was published at page 62 of Radio News, 1949, issue 11. The same year, mr. Bates published the non-direct coupled version of this amplifier on the june issue of Audio Engineering, page 30. This was presented as "low power cathode coupled amplifier". The more professionally-oriented magazine distanced itself from the autor by presentig it as novelity in the "reader's contribution" section. The author also toned down the claims, and dropped the absurd 4.5W power specification.
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Old 18th July 2019, 10:06 PM   #25
Bas Horneman is offline Bas Horneman  Netherlands
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Not sure how many watts this delivers. But it sounds sweet on my efficient speakers.
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File Type: jpg 6v6.jpg (111.6 KB, 173 views)
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Last edited by Bas Horneman; 18th July 2019 at 10:09 PM.
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Old 18th July 2019, 10:47 PM   #26
leadbelly is online now leadbelly  Canada
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I don't know why you are obsessed with building something unusual. What's wrong with a 6SJ7 driving a 6V6 RC coupled? If you buy into this 0 feedback, triodes-only nonsense, then just strap them as triodes.
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Old 19th July 2019, 12:00 AM   #27
kodabmx is offline kodabmx  Canada
Spreading triode love.
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DC coupled single ended cathode follower 6SJ7/6V6 amp project
Triodes are more linear. It's not nonsense, just an observation. I use gNFB on my triode amps, too. Open loop is a pain in the butt to get flat IMHO. I'd triode-strap the 6SJ7, and use a triode strapped 6DQ6 or something, but that's just me, right? Also I only build PP amps... YMMV
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Old 19th July 2019, 12:28 AM   #28
6A3sUMMER is offline 6A3sUMMER  United States
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Bas Horneman,

I like the simple circuit, including the UL.I am starting to use UL in some SE and some PP amps now (I never thought I would like that but I do). What is the function of the 2 diodes and 2 electrolytics in the primary circuit?
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Old 19th July 2019, 12:58 AM   #29
Tubelab_com is offline Tubelab_com  United States
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Quote:
What's wrong with a 6SJ7 driving a 6V6 RC coupled?
That's where I started in the early 60's at around age 10. This was before computers and the only place to find schematics was a magazine article, a book from the library, or by ripping something apart and tracing it's circuit, something I did a lot. The 6SN7 driving a 6V6, powered by a 5Y3 schematic was obtained by carefully tracing the circuit of a friends old Fender Champ. That design worked for guitar and my record player. A ham radio guy taught me how to convert grid leak bias into cathode bias and it got better. When I couldn't find 6V6's in the trash, I used a 6BQ6.

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Tubelab_com : your cathode follower amp is very interesting ! If you have any new informations
I did all the cathode follower stuff 12 years ago mostly for one purpose. Microchip had sponsored a design contest in Circuit Cellar magazine featuring their then new dsPIC chips. They wanted some unique designs featuring their new chips, so I set out to build a rather unique vacuum tube HiFi amp with some efficiency and power output improvements afforded by modulating the power supply voltage under DSP control. Low power output....low B+ supply voltage.....big transient coming, crank up the supply voltage just for that instant, then turn it back down. This is somewhat similar to a class H solid state amp.

I had just finished up a two year research project in my day job designing such a system for cellular towers and phones, so I just re-applied it to a tube amp. Changing the supply voltage on a conventional audio amp while it's playing music will cause all sorts of audible artifacts or worse, so I first needed to create an amp where the power supply knob could be turned without any change in the sound, provided it furnished enough voltage to avoid clipping. The best way to do this is a cathode follower due to its extremely high power supply rejection ratio (PSRR).

The amplifier that I designed for this project could be used without the DSP controller, but you certainly could not run it on 450 volts and get 20 watts out of it for long. The design could be adapted for several different tube complements, but the 6336 and 6LW6 tubes performed the best of any tubes I tested. I am enclosing the entire magazine article from the October 2009 issue of Circuit Cellar magazine. It did win a prize in that contest which resulted in me writing this article for the magazine. That provided me with a good chunk of cash, and got me a phone call from Hartley Peavey asking if the technology could be adapted for guitar amp use.....I had to tell him that it would work, but just didn't sound good when cranked to 11....

I built a few cathode follower amps during this design project. The first was a breadboard that worked quite well. It's schematic can be found in post #22 of this thread, pictures of the PC board version in post #55, schematic (without the bias pots) in post #62:

20W cathode follower amplifier
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File Type: pdf 2910014_Anderson.pdf (289.1 KB, 46 views)
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Old 19th July 2019, 02:25 AM   #30
Dinolobe is offline Dinolobe  Canada
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Quote:
Originally Posted by leadbelly View Post
What's wrong with a 6SJ7 driving a 6V6 RC coupled
Absolutely nothing. But itís fun to go where youíve never been.

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Originally Posted by Tubelab_com View Post
That's where I started in the early 60's at around age 10. <snip:
Cool story ! Thanks ! Iíve started to read the thread.

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Originally Posted by pcan View Post
The same year, mr. Bates published the non-direct coupled version of this amplifier on the june issue of Audio Engineering, page 30.
Do you have access to the orher pages of the article ?
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