Paraphase Splitter - why is it unpopular? - 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 7th March 2006, 10:15 PM   #1
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
Default Paraphase Splitter - why is it unpopular?

The reason I'm interested to learn more about the (floating) paraphase is that it seems to be a handy and simple way of obtaining good gain, balance and voltage swing.

The LTP splitter, which I use at present and which also gives good gain and voltage swing, is a less simple solution because it needs a CCS in the tail (with attendant negative supply) to achieve good balance.

The paraphase splitter appears to be a thing of the past and I'm wondering why?
  Reply With Quote
Old 8th March 2006, 05:12 AM   #2
diyAudio Member
 
Tubes4e4's Avatar
 
Join Date: Jul 2005
Location: Leverkusen
Default Re: Paraphase Splitter - why is it unpopular?

Quote:
Originally posted by ray_moth
The paraphase splitter appears to be a thing of the past and I'm wondering why?
Comparing to concertina and LTP, the main advantage of the paraphase is that it obviously gives the most voltage gain of that trio.

The drawback is, that it obviously has the highest distortion of that trio. F.e, the concertina is low distortion by design (100% local FB), and in an LTP, much distortion cancels out due to its PP nature.

The paraphase being just two consecutive grounded cathode stages, distortion, especially uneven harmonics, sums up.

Due to the consecutive stages and the coupling caps involved, the phase behaviour is worse than concertina or LTP, too, and obviously it cannot be the same for both "paths" after the splitter. This might add to stability problems with gNFB, which are hard to tame since the phase errors are not symmetrical after the splitter.

Summing up, I guess paraphase was popular mostly because of its high gain and because it doesn´t need additional -ve voltage (or CCS) or elevated heaters, and so on, to get reasonable performance.

Tom
__________________
If in doubt, just measure.
  Reply With Quote
Old 8th March 2006, 10:38 AM   #3
lndm is offline lndm  Australia
diyAudio Member
 
Join Date: Mar 2006
Location: nsw
Yes. The paraphase phase splitter does seem easy (and inexpensive) to implement, but the thought of the upper and lower resultant portions of my waves going through different amounts of circuitry doesnt sit well.

The frequency extremes may also exhibit differing levels of phase shift.
  Reply With Quote
Old 9th March 2006, 02:24 AM   #4
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
Thanks for your replies, which make sense.
  Reply With Quote
Old 9th March 2006, 12:51 PM   #5
diyAudio Member
 
Join Date: Sep 2003
Location: iowa
Default Works for me

I've used it and it seems to work fine for me. Here is a quote from Joseph Diamond, a development engineer for UTC from days goneby, re the circuit as used in his amplifier design,

"The phase inverter used is of the paraphase or anode follower type, and is difficult to surpass. For high frequency applications this circuit has given excellent balance to 1 megacycle."

This refering to a 6SL7 used as input volt amp and paraphase splitter. I will note that my design was a two stage with no feedback and Diamonds was a three stage with local feedback between the power and driver stages but no feedback to the splitter/input.

Easy enough to try, then you can form your own opinion.

Michael
  Reply With Quote
Old 9th March 2006, 03:43 PM   #6
diyAudio Member
 
Tubes4e4's Avatar
 
Join Date: Jul 2005
Location: Leverkusen
Default Re: Works for me

Hi Michael,

Quote:
Easy enough to try, then you can form your own opinion.
.

I did

But leaving generalisations aside, I agree. There is no "best splitter" topology anyway, as usual, it just depends on the goals being set to chose the topology that meets the requirements best.

Tom
__________________
If in doubt, just measure.
  Reply With Quote
Old 9th March 2006, 07:59 PM   #7
diyAudio Member
 
Dave Cigna's Avatar
 
Join Date: Oct 2003
Location: Finger Lakes, NY
Quote:
... the thought of the upper and lower resultant portions of my waves going through different amounts of circuitry doesnt sit well.
I've heard this argument before, but it seems to me that a LTP does the same thing when only one grid is driven. The 'undriven' side is running as a grounded grid (which is not the same mode of operation as the driven side) and gets its signal only after it passes through the driven side.

I admit that the LTP looks a whole lot more elegant and somehow more balanced than the paraphase on paper. It almost certainly produces more symmetric outputs if a CCS is used as a tail. If that's what you're going for then the LTP is the obvious choice.

Incidentally, I have tried the paraphase and found it sounded surprisingly good despite its apparent warts.

-- Dave
  Reply With Quote
Old 9th March 2006, 08:44 PM   #8
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Quote:
Originally posted by Dave Cigna


Incidentally, I have tried the paraphase and found it sounded surprisingly good despite its apparent warts.

-- Dave

I agree. The bonus is a 3 stage amp. Most of the para designs worked with an ECC83 which I basically loathe. Short of a complete bench redesign, has anyone tried it with a better tube ?

The 7199 is a good runner for cathodyne but I find pentodes fussy to setup between makes and despite lower gain behave better strapped as triodes.
  Reply With Quote
Old 9th March 2006, 09:35 PM   #9
lndm is offline lndm  Australia
diyAudio Member
 
Join Date: Mar 2006
Location: nsw
Quote:
Originally posted by Dave Cigna

I've heard this argument before, but it seems to me that a LTP does the same thing when only one grid is driven.
-- Dave
Yes, it _seems_ that way. The other triode is driven by its cathode, which is using the same resistor as the first triode. They are intimately connected. I feel this intimate connection is the phenomena that makes local feedback a different proposition to global.

I have used the Williamson phase splitter before. This is a standard split load phase splitter followed by a pair of otherwise independent voltage amps that share a tad of cathode feedback. Elegant, fairly simple in design, even if it takes a couple of extra triodes, and it drives well.
  Reply With Quote
Old 10th March 2006, 12:50 AM   #10
diyAudio Member
 
Join Date: Sep 2003
Location: iowa
Default oops

OK guys, I have to fess up. I was wrong on both points. First, Mr. Diamond did take overall feedback to the cathode of the first section of the 6SL7. Second, my build is actually a sort of funky hybrid. It uses a 6N7, a twin triode with the cathode common to both sections, and the cathode resistor is only partially bypassed. So I guess you could say it is a short tailed paraphase inverter. Try it you'll like it.

Michael
  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
Unpopular music Prune Music 28 1st June 2008 06:31 AM
Trouble with a paraphase PI Turbo7MN Tubes / Valves 17 26th May 2007 02:07 AM
Help on Magnavox Paraphase (Gabevee?) pengboon Tubes / Valves 7 26th June 2006 04:02 AM
So why are sealed boxes so unpopular? David Gatti Multi-Way 33 6th May 2005 07:55 PM


New To Site? Need Help?

All times are GMT. The time now is 04:58 AM.


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