Conrad johnson topology - 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 29th July 2003, 01:47 PM   #1
Stefano is offline Stefano  Italy
diyAudio Member
 
Join Date: Jun 2002
Location: Cagliari, Sardinia
Default Conrad johnson topology

Hi to you all, has anyone of you any information on conrad-johnson's art amplifier topology? Is it something like a tube differential amplifier single-stage or so?
__________________
Let's make something special
  Reply With Quote
Old 29th July 2003, 02:29 PM   #2
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Just plain common cathode with resistive load.
  Reply With Quote
Old 29th July 2003, 02:31 PM   #3
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: Conrad johnson topology

Konnichiwa,

Quote:
Originally posted by Stefano
Hi to you all, has anyone of you any information on conrad-johnson's art amplifier topology? Is it something like a tube differential amplifier single-stage or so?
Multiple paralleled 6DJ8/6922 sections (exact number depends upon the type as the ART has been also build in premier guise), cathode bias via 2pcs silicon diodes in series (appx. 1.2V bias), all anodes bussed up and one common Anode load resistor. Nothing differential, all SE.

Sayonara
  Reply With Quote
Old 29th July 2003, 03:01 PM   #4
diyAudio Member
 
Brett's Avatar
 
Join Date: Jan 2002
Default Re: Conrad johnson topology

Quote:
Originally posted by Stefano
Hi to you all, has anyone of you any information on conrad-johnson's art amplifier topology? Is it something like a tube differential amplifier single-stage or so?
Single ended using 5 6922 tubes with all 10 sections in parallel.
It has poly caps in the PS, and a uprocessor controlled shunt input attenuator.
Yawn.
And only $US15k.
  Reply With Quote
Old 29th July 2003, 03:14 PM   #5
diyAudio Retiree
 
Join Date: Oct 2002
Location: Spain or the pueblo of Los Angeles
Default If my guess is correct

I would bet dinner that the power supply is based on BJT emitter followers. I have owned three CJ products, and worked on several others. I have a Premier Four of a friend's that he has been waiting years for me to fix. With some Vishays and RelCap foil and Polystyrene caps it is very nice sounding. The CJ stuff is interesting since it is so diametrically opposed to the Audio Research designs. I forget if it was Mr.C or Mr. J, but I remember one of them describing the AR designs as byzantine*. Having fixed a few AR products and wondering how many of the dozens of parts in a circuit had failed (and it is never just one) I would have to agree. One of Jocko's friends tried to give me an AR amp. Feeling that was a bit too generous I paid $100 bucks, spent a coulple of months getting it to stay fixed and sold it to another guy who popped $500 in cash in my hand one day when I was not even attempting to sell it. I gave no warranty with it. My CJ MV-75 that the purchaser of the AR sold me earlier blew up so many times that I sold the transformers from it and pitched the rest. So ended my ownership of CJ or AR tubed amps. the Counterpoint stuff blew up more than either the CJ or AR stuff so I just fixed it and didn't even think about owning it. Anybody wonder why I went solid state?

*Definition: A term describing any system that has so many labyrinthine internal interconnections that it would be impossible to simplify by separation into loosely coupled or linked components.

Not nostagic for tubes,

Fred
  Reply With Quote
Old 29th July 2003, 04:38 PM   #6
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: If my guess is correct

Konnichiwa,

Quote:
Originally posted by Fred Dieckmann
I would bet dinner that the power supply is based on BJT emitter followers.
Yup. Spot on. Not the worst possible choice either.

Quote:
Originally posted by Fred Dieckmann
So ended my ownership of CJ or AR tubed amps. the Counterpoint stuff blew up more than either the CJ or AR stuff so I just fixed it and didn't even think about owning it. Anybody wonder why I went solid state?

Not nostagic for tubes,
Hmmm. While I very appreciate the legendary unreliability of ARC, CJ and Jadis it would be good to mention for contrast a pair of Quad II I came across a few years back. These had been modified by the BBC with regards to connectros and had done 5 - 6 Years service at the BBC before being replaced with transistor Amp's and sold off, where they reached the gentleman who had them checked out by my through two further owners.

I could tell upon opening the Amp's up that I had been the first person to open them up since the original BBC tech who had fitted the different connectors. The Valves also appeared original. The Amp's still played fine and obviously survived many years gracefully. Sure - most carbon composite resistors had drifted and the 'lytic cap's where near "shot though", but all in all fine Amp's.

After replacing many resistors and all 'lytic cap's plus a new set of Valves they have been playing since with no hitch whatsoever.

That is the difference between a design that operates all parts conservatively (all below 50% rated dissipation and good voltage headroom for cap's) and uses high quality (and relaible Valves) compared to designs that try milking every watt possible from inferior quality Valves and underrated parts.

Don't blame the fact that ARC, CJ and co used Valves, blame imprudent (at best - at worst highly incompetent) design for the lack of reliability. As a rule, competently designed valve gear is AT least as reliable as competently designed transistor gear, however it generally glows longer and sounds better... ;-)

Sayonara
  Reply With Quote
Old 29th July 2003, 04:43 PM   #7
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Don't blame you a bit, Fred. The only tube stuff I'll use is diy. Commercial tube power amps nearly always suffer from one or more of the following:

Poor thermal management (heat flow)
Running output tubes too close to the edge
Overly high value grid resistors
Caps that tend toward leakage at high temperatures
Unsatisfactory grounding and power distribution
Unsatisfactory protection of solid state devices
Non-bulletproof regulators
Unreliable tube sources
Poorly controlled startup and shutdown

You could probably tack a few more items onto this list.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 29th July 2003, 05:27 PM   #8
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Default Ad nausium...

Component penny-pinching
Insulation creepage distance "blindness"
Chaffing of wiring
Component and wiring anchorage deficiencies long-term
Susceptibility to mains-born interference of one or both kinds

Other than that, they're fine

But when well built, the small signal valves should last as long as most people would keep a SS amp. The output valves need replacement more often though.
  Reply With Quote
Old 29th July 2003, 05:46 PM   #9
diyAudio Retiree
 
Join Date: Oct 2002
Location: Spain or the pueblo of Los Angeles
Default Ditto to the tenth power

Quote:
Originally posted by SY
Don't blame you a bit, Fred. The only tube stuff I'll use is diy. Commercial tube power amps nearly always suffer from one or more of the following:

Poor thermal management (heat flow)
Running output tubes too close to the edge
Overly high value grid resistors
Caps that tend toward leakage at high temperatures
Unsatisfactory grounding and power distribution
Unsatisfactory protection of solid state devices
Non-bulletproof regulators
Unreliable tube sources
Poorly controlled startup and shutdown

You could probably tack a few more items onto this list.

We have never been in greater agreement on anything. It is also possible to design unreliable solid state circuits as well I just don't seem to have to fix even a small fraction as many. I have cranked down bias levels in an effort to extend tube life with little improvement in tube life. I don't want to pays for new specialty tubes that are degrading at about the running time that the solid state stuff is breaking in. Yes, they can sound wonderful and it is very recently that solid state is closing the gap, but do you really want deal with idiosyncrasies of a racing car every time you want to go a couple of blocks to the store?
  Reply With Quote
Old 29th July 2003, 05:55 PM   #10
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
The race car analogy is one I use all the time with friends who are considering tubes. "Be prepared to smell hot soldering irons and keep a spare amp handy."
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  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
Conrad Johnson Premier 10 Freddie Tubes / Valves 2 19th March 2013 08:45 AM
Conrad Johnson PV-7 noise Kid Charles Tubes / Valves 19 12th April 2008 11:42 PM
Conrad Johnson Sonographe SA-250 crossroads Swap Meet 1 3rd February 2008 07:40 AM
Conrad-Johnson PV6 Preamp paulcurrie Tubes / Valves 3 17th April 2004 07:11 PM
conrad johnson help efoda Tubes / Valves 3 24th January 2002 03:23 AM


New To Site? Need Help?

All times are GMT. The time now is 01:38 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