Blue Voodoo Solid State Rects to Tube Rects? - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 2nd June 2009, 08:47 PM   #1
diyAudio Member
Join Date: Jun 2009
Question Blue Voodoo Solid State Rects to Tube Rects?

I know I'm new here but the basis for the join is I've about racked my brain out on this probably because I'm overlooking something very basic...

Let me start off by saying this isn't my first project with amps but it is my first with tube amps. I own 3 tube amps plus this and want to mod it to see if the overall effect and appearance is worth modding my real amps.

The current amp I'm modding for fun is the Crate Blue Voodoo 120w. It's by no mean a top of the line amp but it's my test mod amp and I'd rather destroy this than my other 3 amps...

BV120_2 BV120_1

You can see the 3 full wave rectifier circuits and maybe I'm a little confused here but would each of those need an individual tube? I was under the impression 1 tube or 2 tubes could drive all 3 circuits... I am looking at installing 5AR4's... Anybody have input?
  Reply With Quote
Old 2nd June 2009, 08:57 PM   #2
diyAudio Member
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
BV120 comes up ok but BV120 1 seems to be a bad file.
  Reply With Quote
Old 2nd June 2009, 10:09 PM   #3
diyAudio Member
Join Date: Jun 2009
That was my bad I'll re-up the files...
  Reply With Quote
Old 2nd June 2009, 10:09 PM   #4
diyAudio Member
Join Date: Jun 2009
Default Re-Upped Files

The new files are listed at this HTML:

Blue Voodoo
  Reply With Quote
Old 2nd June 2009, 10:30 PM   #5
diyAudio Member
Join Date: May 2007
Hi, what sort of change to the sound are you seeking?
Looking at schematic of power supply, I cannot see an easy way of replacing SS bridge with a 5AR4, the HT winding has no centre tap, and there is no 5V heater supply winding.
If slow start is required, may add a TV damper diode such as 6AU4 or 6AX4 in series with HT after first filter capacitor. Another idea might to replace the 1N4007 rectifiers with diodes that have a more benign switching characteristics, there are other on this forum that can suggest something, I have kept to tube rectification in my own designs, so cannot really suggest specific types.
  Reply With Quote
Old 3rd June 2009, 05:36 AM   #6
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
Right. You just say you want to "mod" these, but what are you trying to achieve? By inference you seem to want to make the power suply rectifiers tube based, but you don;t state why. I can see that a tube rectifier in the B+ circuit might add some sag dynamics, but hte rest is a mystery.

Unless you just want the challenge of making just EVERYTHING a tube, I don;t see the purpose. You have three bridge circuits. I don;t know what you mean by one tube could drive all the circuits.

One bridge provides the B+ - the high voltage for the tubes. But as radiotron points out, there is no center tap on the HV winding, and no 5v winding for the rectifier heater, so that makes a tube rectifier a lot harder to use. I suppose you could add a 5v transformer for the heater, and you could replace half the bridge with a tube maybe. But just sticking a tube rectifier in there in place of the diodes will drop your B+ voltage considerably.

Then ther are the other two bridges. Did you sort out what each does? The lower one make DC voltage for the preamp tube heaters. Why on earth would you want to try to run that off a tube rectifier? It's not in the signal path.

The bridge in the center makes +/-9.5VDC for the 5532 effects loop op amp IC, and +/-10VDC for the reverb driver IC as well as the LEDs and the transistor switching circuits. Again, I can;t imagine why you;d want to make the power supply for that tube based. Those op amps are in the signal path, but they are all working class A, there would be no sag dynamics to play with anyway.

Adding all these tubes would certainly add weight and a lot of heat to your amp.

Regardless of what you think of the tone, the amp as it exists now does work, so I don;t think. a soft start is an issue.

SO what are your overall goals in this project? I see plenty of possibilities to modify the signal circuits, massage the tone, tweak the gain structure, ets.
  Reply With Quote
Old 3rd June 2009, 02:27 PM   #7
diyAudio Member
Join Date: Jun 2009
Your both absolutely correct, the point or inspiration is really just for the challenge to see if I could get it done, I'm not looking for an overall tonal change since sag only occurs when the amp is played at a rather loud volume. The whole change would be just to add tubes to make it an "all" tube amp. I'd already thought about the the transformer and you are correct I'd be adding another one to the two transformers already in the unit.
  Reply With Quote
Old 3rd June 2009, 11:28 PM   #8
diyAudio Member
Join Date: Jun 2009
Originally posted by Enzo
SO what are your overall goals in this project? I see plenty of possibilities to modify the signal circuits, massage the tone, tweak the gain structure, ets.
If you have other thoughts aside from toying around with the rectifier I'd be interested in hearing them. After allm, all I do this for is fun and for the learning experience I am not an "audiophile" I just like finding new and better ways to modify some things. I am still searching for the best tone out of each amplifier but I like doing things one step at a time...
  Reply With Quote
Old 4th June 2009, 01:48 AM   #9
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
I don;t have specific ideas for you, that isn;t my thing. I run a pro audio maintenance and repair operation. I am more interested i getting things back to normal.

But all the things people do to amps could be done to yours. Changing tone stack values, changing voicing in the stages. Massaging the NFB, altering the gain structure, trying different tubes. (Get yourself a 5751 and sub it for each 12AX7 one at a time and listen for the differences sometime) And so on.

There are some great resources. Under the software downloads - they are free - at DUncan amps is a tone stack calculator. It allows you to select a number of tone stack circuit types and then vary the component values and see the response curve changes in real time graphically. Very cool. Plenty of other good stuff there.

Check out the tech info section at Aiken's site

kevin O'Connor's site has good stuff too

And while the forum here is generally aimed more at hifi, there are other forums that are focused on guitar amps, you might look around. I like the MEF
  Reply With Quote
Old 4th June 2009, 07:13 AM   #10
diyAudio Member
Join Date: Oct 2004
Location: Adelaide South Oz
Tube rectifiers for Guitar Amps are generally not a good thing.

It depends a bit on what you want to achieve - for example, modern metal tones are produced by overdriving the preamp and running a very clean almost HiFi'ish power amp which needs a clean fast and have a reasonably hard "little sag" power supply. SS is the go for this.

The ONLY sound that "requires" a tube rectifier is that 60's and early 70's Dirty Blues sound which is achieved by a reasonably clean preamp sound and driving the power amp hard so that you get power supply sag on the attack.

This sound can be achieved in various ways. A current limit in the high voltage supply is one way to do it (a MOSFET and 1 transistor circuit). If it is just Power Amp "compression" that you want then you can actually induce the Power Section to do this at a lot lower volume by replacing those 470 Ohm Screen resistors with 2K2 or even higher.

  Reply With Quote


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
Blue Voodoo Tube amp issue sasij Instruments and Amps 1 24th July 2008 11:51 AM
parts from abandoned amp project for sale (caps, rca sockets, bridge rects.) 01001101 Swap Meet 0 18th November 2006 11:25 PM
FS: 6800uF/63V caps, regulators, transistors, Br/Rects len_scanlan Swap Meet 2 18th January 2006 10:12 PM
Best Tube 4 Solid State Jay Tubes / Valves 17 29th March 2003 04:08 PM
solid state or tube? jaybird Solid State 5 1st February 2003 10:17 AM

New To Site? Need Help?

All times are GMT. The time now is 07:16 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2