Super spud-amp? - 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 28th August 2008, 04:37 PM   #1
JoshK is offline JoshK  Canada
diyAudio Member
 
Join Date: May 2004
Location: Toronto, ON
Default Super spud-amp?

I was thinking about Gary Pimm's pentode +CCS driver circuit last night and it occured to me that this could potentially make a super spud, could it not? I think that would be a cool project to learn some things on, specifically how to build the CCS and how to set it all up.

The small Edcors are cheap so the project wouldn't need to be expensive. One could also use the Swenson/Pimm regulator for the B+ and learn how to build that too. Then it would be an uber spud.

If I did my calculations correctly you could use a 2.5K/8 ohm OPT, since the circuit has a Z out of 500, and get 3 1/4 watts rms out. That is 2A3 territory from a spud. Might make for a kick *** compression driver amp for my active speaker project.

What do you guys think? Would it work?
  Reply With Quote
Old 28th August 2008, 04:40 PM   #2
JoshK is offline JoshK  Canada
diyAudio Member
 
Join Date: May 2004
Location: Toronto, ON
Oh forgot to add the link

http://www.pacifier.com/~gpimm/drivers.htm

Specifically the driver circuit on the right of the top schematic (using 6BQ5).

Click the image to open in full size.

I was also thinking that this would mean parafeed is in order.
  Reply With Quote
Old 28th August 2008, 06:12 PM   #3
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
I don't think I understand the circuit. Isn't that a CCS on top of a CCS? Won't they fight?
  Reply With Quote
Old 28th August 2008, 06:19 PM   #4
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Yes, they will fight.

Try this approach:

Click the image to open in full size.

FET for top transistor will give you higher dynamic resistance.
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 28th August 2008, 06:52 PM   #5
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
I'm not seeing it, where is the second CCS? The bottom pentode looks to me a simple R biased gain stage with a resistive plate load to set gain/distortion.
__________________
Ears aren't microphones.
  Reply With Quote
Old 28th August 2008, 07:18 PM   #6
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by rdf
I'm not seeing it, where is the second CCS? The bottom pentode looks to me a simple R biased gain stage with a resistive plate load to set gain/distortion.
The one on the left, the plate load looks like a resistor to me (and I don't understand the CCS there at all -- maybe I'll go read the article).

But, for the one on the right, I thought the point of a pentode in this configuration is that it is more or less a current sink. Looking at pentode curves, as G1 changes with signal, the current draw should change, and it looks like the voltage is incidental, which will be trouble if the CCS won't allow this to happen. Maybe there are imperfections which lead to huge V swings? Anyway, I really don't understand pentodes very well, so I'm trying to ask a dumb question to see if something will click in my head.

Edit: From the article

Quote:
Here are the results of some Pentode driver stage experiments done awhile back. The idea was to see what could be done combining Pentodes and CCS's. Generally, you can't load a Pentode with a CCS as you are effectively trying to series couple 2 CCS's. This issue is resolved by having a plate resistor in circuit so there is a defined resistance that the Pentode and CCS can work into.
I didn't notice that resistor to ground on the right
  Reply With Quote
Old 28th August 2008, 08:04 PM   #7
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
The only reason it stood out are sims I'm currently doing on a DC coupled, plate choke loaded pentode driver config. Stage gain is set by shunting the choke with a series RC sting.

In both circuits my guess is the top CCS provides the bulk of the gain stage static current and allows more leeway in selecting the shunt R & B+. I haven't tried the circuit on the right but the one left never sim'd with acceptable stability. In the sense that both circuits can be seen as a voltage to current gain stage in series with an essentially infinite DC impedance, it has similarities to two series CCSs.

It also looks like in both these circuits the real purpose is making use of the CCS mu function.
__________________
Ears aren't microphones.
  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
Spud anyone? tubelab.com Tubes / Valves 88 12th January 2010 12:22 AM
Which Spud Amp? ambience exists Tubes / Valves 0 23rd July 2008 09:43 PM
Is this a Spud Amp ? mod_sonic Tubes / Valves 7 12th July 2006 11:11 AM


New To Site? Need Help?

All times are GMT. The time now is 07:31 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