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 9th September 2012, 12:56 AM   #1
diyAudio Member
 
Join Date: May 2010
Location: Hawkes Bay
Default Grounded grid stage in guitar amp

I'm trying to figure out the effect of the grounded grid (effects return) stage in the soldano super lead 60 schematic I found at EL34world.com.

Also, the following triode is a puzzle. It has a 100k resistor on both anode & cathode with grid connected to previous grounded grid anode at B+.

What happens in these 2 triodes as they overload?

JimG
  Reply With Quote
Old 9th September 2012, 01:03 AM   #2
diyAudio Member
 
Join Date: May 2010
Location: Hawkes Bay
Here is a pdf of the schematic. V3 a&b have me intrigued.
JimG
Attached Files
File Type: pdf soldano_super_lead _60.pdf (173.6 KB, 55 views)
  Reply With Quote
Old 9th September 2012, 02:47 AM   #3
jjman is offline jjman  United States
diyAudio Member
 
Join Date: Jan 2009
That can't be correct I believe. It would put dc on the effect return from the cathode side of R18. I suspect a schematic switcharoo. Not an official one right?
  Reply With Quote
Old 9th September 2012, 03:50 AM   #4
benb is offline benb  United States
diyAudio Member
 
Join Date: Apr 2010
I agree about the DC, and more, I guarantee that schematic is wrong. Even if the return were meant to be a "cathode input" the plate goes directly to B+ and so there's no signal going to the grid ofV3b.

Now I see the disclaimer about accuracy in the lower left corner.

If there's a forum at that site, ask there. Someone may have a corrected version of the schematic.
  Reply With Quote
Old 9th September 2012, 01:43 PM   #5
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Either a deliberate spoiler, or very clumsy reverse engineering. V3a grid and cathode have been swapped, and R21 should be in V3a anode not V3b anode.
  Reply With Quote
Old 9th September 2012, 05:46 PM   #6
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
Quote:
very clumsy reverse engineering.
I have never seen a Soldano schematic with their name on it. I suspect that all the Soldano schematics on the net are reverse engineering derived. That one has the previously mentioned obvious mistakes. I have another (different) Soldano schematic on my hard drive somewhere that has a few questionable "features".
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 10th September 2012, 08:19 AM   #7
diyAudio Member
 
Join Date: May 2010
Location: Hawkes Bay
So soldano doesn't have a magic grounded grid stage. Can a gg be overdriven? What would that look like? Wouldn't have grid current limiting.
Ever been used in a guitar amp?
  Reply With Quote
Old 10th September 2012, 09:19 AM   #8
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
Quote:
Originally Posted by djgibson51 View Post
So soldano doesn't have a magic grounded grid stage.
No, it's just drawn wrong - VERY wrong

Quote:

Can a gg be overdriven? What would that look like? Wouldn't have grid current limiting.
Ever been used in a guitar amp?
I wouldn't have thought so - I can't see any need (or advantage) in ever doing so?. Grounded grid gives you a low input impedance and a high output impedance, neither of which are of any value in a guitar amp.

You could certainly overload gg just as with any configuration, I don't know as it would make any difference or not?.
__________________
Nigel Goodwin
  Reply With Quote
Old 10th September 2012, 11:13 AM   #9
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by djgibson51
So soldano doesn't have a magic grounded grid stage. Can a gg be overdriven? What would that look like? Wouldn't have grid current limiting.
Ever been used in a guitar amp?
I have never seen a magic grounded grid stage. Ordinary grounded grid stages are often used in valve-based UHF receivers such as 1960s TV sets.
Yes, a gg stage can be overdriven. I presume it would cause signal clipping.
My guess is that gg has never been used in a guitar amp, except possibly by accident - someone blindly copying a bad case of reverse engineering?
  Reply With Quote
Old 10th September 2012, 08:18 PM   #10
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Look at the parts. Someone confused the two triodes. R21 and R19 belong to the left triode, plate and cathode. R18 and return signal go to the grid, not cathode. SO the right triode plate goes to B+. And step back and you have a VERY conventional gain stage with 1 meg grid return, a 1k cathode and 100k plate load. Plate direct coupled to VERY conventional cathode follower driving the tone stack.

What is drawn there is totally a fiction, born of error on the drawer.
  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
Grounded Grid TRANSCENDENT line stage widi Tubes / Valves 12 12th September 2012 07:41 PM
Grounded Grid pre amp-- help please andrewe1 Tubes / Valves 10 17th April 2004 02:37 PM


New To Site? Need Help?

All times are GMT. The time now is 02:20 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