Which phase inverter for a deluxe - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

Instruments and Amps Everything that makes music, Especially including instrument amps.

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 6th November 2013, 01:24 AM   #1
diyAudio Member
 
LATUBEGEEK's Avatar
 
Join Date: Mar 2013
Location: Orange County, CA
Default Which phase inverter for a deluxe

I want to build a 5C-E3 Fender Deluxe clone. See they use a Cathodyne, Paraphase or LTP PI. Want it for guitar. Want to be able to bias the P-P tubes separately. Think I can with any of them. Any favorites out there, and why? Thanks!
  Reply With Quote
Old 6th November 2013, 02:15 AM   #2
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
I would use this one:
http://www.webphix.com/schematic%20h..._5e3_schem.pdf

It has a Cathodyne Phase Splitter.

It is auto bias (cathode bias) so there is no bias adjustment. If you want to be able to use unmatched output tubes then:
- Rather than the common 250 Ohm cathode bias resistor on the 6V6es with a 25uF bypass capacitor, separate the cathodes and put a 470 Ohm 5 Watt resistor with a 47uF bypass capacitor on each 6V6.

If you expect to overdrive it I would change the 1500 Ohm grid stop resitors on the 6V6s to 22 KOhms.

My own (home built) guitar amp is like this except I use 6SL7 octal for the phase splitter.

Cheers,
Ian
  Reply With Quote
Old 6th November 2013, 03:20 AM   #3
diyAudio Member
 
LATUBEGEEK's Avatar
 
Join Date: Mar 2013
Location: Orange County, CA
Ian thanks! I was leaning towards the Cathodyne (5E3), but being only my 2nd build (beyond a 5F1) I'm needing to learn lots about PIs and biasing PPs. The non-PI half of the 12AX7 is a gain stage not in other deluxe designs? Does it actually increase overall gain or just compensate for the Cathodyne's lower gain (relative to other PIs)? And thanks, I will separate the common cathode biasing (seen it on early Fender preamp designs, and will utilize it), but then would you adjust the 470 ohm resistors, to dial in the plate dissipation? And are factory bias adjust pots rated at 5W? I know some only "balance" the bias (not really an adjustment), but they seem to be normal (1/4W). Jeff
  Reply With Quote
Old 6th November 2013, 03:41 AM   #4
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
Gain of the Cathodyne is 1 (actually about 0.95) so the Common cathode amplifier (gain stage) preceeding it in the power amp is used to get the sensitivity up such that a signal level of about 1V is enought to drive the power section to full output.

The suggested 470 Ohm cathode bias resistors will bias the 6V6 tubes very conservatively. You could take these down to 390 Ohms if you want to bias hotter or try say 2 off 820 Ohm 2 Watts in parallel (420 Ohms) for something in between. Biasing hotter gives a richer harmonic content but tubes don't last as long. Less than 390 Ohms per tube is a BAD idea.

If you are a real "shreader" then you could think about using a design with a LTP phase splitter. It responds best to metal head style playing, else the Cathodyne is perfectly adequate.

Cheers,
Ian
  Reply With Quote
Old 6th November 2013, 05:04 AM   #5
diyAudio Member
 
LATUBEGEEK's Avatar
 
Join Date: Mar 2013
Location: Orange County, CA
Sounds good! And since I'm wanting to experiment with PIs, I wonder how difficult it would be to have a separate eyelet board for the PI, so I could build one Cathodyne and one LTP, and swap them out to compare. Or.... install them both... and find a 6PDT switch.....
  Reply With Quote
Old 6th November 2013, 08:40 PM   #6
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
I see no reason that you could not do that.

I recall a post on one of the forums regarding a switchable Phase Inverter, hang on while I start a second session and do a search......
Ah! here it is:
Switchable PI, Paraphase,Cathodyne, LTP.

Cheers,
Ian
  Reply With Quote
Old 7th November 2013, 12:23 AM   #7
diyAudio Member
 
Join Date: Apr 2010
Quote:
Originally Posted by gingertube View Post
I see no reason that you could not do that.

I recall a post on one of the forums regarding a switchable Phase Inverter, hang on while I start a second session and do a search......
Ah! here it is:
Switchable PI, Paraphase,Cathodyne, LTP.

Cheers,
Ian
Way too complicated. A four pole switch is plenty. Cathodyne to LTP. Preamp switching changes from a 5E3 to semi 18 Watt config.

Click the image to open in full size.

Mind you it takes some liberties with the standard Fender values. Problem with doing something of this sort is that you have to be careful you do not get ultrasonic oscillations. Layout is important, not really for a beginner. Have schemed up a few other PI switching circuits, will have to try them all some day.
  Reply With Quote
Old 7th November 2013, 03:21 AM   #8
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
Thanks P2 for the update of your switched PI.

@Latubegeek
My early posts show signs of being done late afternoon with the brain in lurking till go home time mode.
When you put separate cathode bias R and C on each tube then you need to double the resistance (develope the same bias voltage from 1/2 the current) and to keep the same frequency response you need to halve the capacitance.
That means you replace a single 250 Ohm resistor with a 25uF bypass cap with a 500 Ohm resitor and a 12.5uF bypass cap on each tube.

470 Ohms and 22uF on each tube will be fine.

Cheers,
Ian
  Reply With Quote
Old 7th November 2013, 11:50 AM   #9
diyAudio Member
 
doozerdave's Avatar
 
Join Date: Feb 2012
Location: Kitchener, Ontario
One more thing about the concertina PI; If you do hope to overdrive the 6V6's you'll need as high a voltage as possible on the PI to ensure it has enough headroom to not overdrive itself if the incoming signal is high. In my PPP 6V6 amp I've got the concertina PI running at the same level as the screens, filtered through a 7H choke (probably doesn't need to be that large, but it's a choke I had handy).

This is a good read.
__________________
-Dave
  Reply With Quote
Old 9th November 2013, 03:32 AM   #10
diyAudio Member
 
LATUBEGEEK's Avatar
 
Join Date: Mar 2013
Location: Orange County, CA
Default STARTED MY HYBRID 5E3 DELUXE!

Thanks Dave! I wanna get started on something, so decided on the 5E3 Cathodyne. I am going to drop the 2nd pair of inputs, use both 1/2s of the preamp 12AX7 on one input (and the cathodyne PI gives me a 3rd stage of gain!), but use a single tone pot (ala AA764) to keep it simple. Attached is the schematic and the eyelet board on my breadboard. So far so good. Now to build the PI eyelet board and put them both together!
Attached Images
File Type: jpg 3-STG GAIN DESIGN.jpg (661.6 KB, 48 views)
File Type: jpg IMAG1412.jpg (788.4 KB, 49 views)
  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
Need help identifying a phase inverter LATUBEGEEK Instruments and Amps 6 27th September 2013 11:59 PM
How to make a phase inverter? Fresh Analog Line Level 1 7th March 2012 07:57 AM
Gain of Phase Inverter hpupo Tubes / Valves 10 28th May 2011 02:21 PM
Phase inverter ThSpeakerDude88 Tubes / Valves 37 29th August 2007 03:15 PM
Modified Fender Deluxe - Constant Current Phase Splitter lcsegeng Tubes / Valves 6 26th February 2007 07:22 PM


New To Site? Need Help?

All times are GMT. The time now is 11:21 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