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 21st April 2003, 07:20 PM   #1
diyAudio Member
 
Join Date: Apr 2003
Location: Israel
Default Strange phase splitter design !?!?

Hello All,

Just bumped into this ecl82 design and could not figure out the phase splitter design, looks sort of a biased concrtina and the FB does not go to the usual place.

Can anybody explain to me how this design works?

thank you very much.

http://www.fonar.com.pl/a_index.htm

Glass_painter.

PS

Look at this web site, this is a gold mine of info, do not let the fact that it is in Polish stop you, look at the schematics.

Gp
  Reply With Quote
Old 21st April 2003, 07:26 PM   #2
diyAudio Member
 
Join Date: Apr 2003
Location: Israel
Sorry about that, from some reason the first URL directs to the main page and not to the article, lets try again.

http://www.fonar.com.pl/audio/projek.../wzm13/wzm.htm

Thanks.

Glass_painter
  Reply With Quote
Old 21st April 2003, 08:06 PM   #3
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Wow! That is unusual.

It's a concertina sat on top of a common cathode amplifier, so the lower valve thinks its a mu-follower. Very cunning. Distortion will be low due to mu-follower action. Analysing output balance will be much harder. Because the output voltages must be referred to ground, output balance will be a bit problematic, hence the tweak. I would expect it to work well, but (like all series amplifiers) be hungry for HT volts.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 22nd April 2003, 11:33 AM   #4
diyAudio Member
 
Join Date: Feb 2003
Location: Birmingham, UK
It is an interesting circuit - the designer is obviously a fan of cathode followers, as there are two in the pre-amp also - the second one feeding into a 500k volume control, which I would have thought was rather high in value for this circuit

Because of the language the explanation of the amp is not available, but I would be interested to know why an ECC85, a VHF RF/frequency changer tube was chosen for the second pre-amp tube in preference to a designated audio tube, and I cannot see how the first half of the first tube in the pre-amp receives bias, as the cathode is taken straight to chassis and there does not appear to be grid bias.
  Reply With Quote
Old 22nd April 2003, 11:48 AM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
and I cannot see how the first half of the first tube in the pre-amp receives bias, as the cathode is taken straight to chassis and there does not appear to be grid bias.
It should still bias slightly through the 330K gridleak R.
Probably only just enough to take an MM cartridge, a 3M3 R would have been a beter choice.

Just my two cents though.
__________________
Frank
  Reply With Quote
Old 22nd April 2003, 11:49 AM   #6
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
The output cathode follower has a strange bias arrangement too. It's direct coupled from the previous valve (which would bias it) but it also has self-bias from its cathode chain. The two will fight one another. Using the cathode follower to drive the Baxandall tone control makes sense as the first stage will be incapable of driving anything. Perhaps the logic of the design is explained by the fact that it was designed in the "flower power" era?
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 22nd April 2003, 01:19 PM   #7
diyAudio Member
 
Join Date: Feb 2003
Location: Birmingham, UK
....Certainly an unusual circuit. Two cathode followers in the pre-amp which are hardly going to contribute to gain, the Baxandall tone control system which will hold down the gain of that stage, meaning that the first stage of the first tube will be providing the most gain in the pre-amp! And this tube not properly biased!

I agree with Frank that really a minimum of 3.3Meg is needed to provide bias to avoid distortion in the first stage, although I'd prefer higher values, 4.7 - 10meg preferably. Even then, using grid bias has traditionally not been recommended for hifi amps because of its non-linear amplification. When used with amps such as the Mullard 3-3 it was with the proviso of large amounts of NFB to correct the linearity.
  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
Is this a phase splitter? tom-vdl Solid State 9 15th October 2009 08:21 PM
phase splitter with Tr ? sam8888ysl Tubes / Valves 9 22nd October 2008 11:28 AM
Strange splitter in the Audio Research D4 ray_moth Tubes / Valves 4 17th August 2008 03:48 PM


New To Site? Need Help?

All times are GMT. The time now is 05:09 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