Is there a no/gain preamplifier schematic using high-distortion EC90? - 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 9th May 2004, 03:38 PM   #1
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
Question Is there a no/gain preamplifier schematic using high-distortion EC90?

Driving the EC90 (same as half a 12AU7) where it can add colouration to material which benefit with plenty of distortion..Rock circa 1970's\vinyl.

But I need a schematic that will provide all the EC90 can give me in terms of gain for microphone sources and little-to no-gain for line level sources while maintaining that tube distortion quality.

Using my rather extensive supply of Mullard EC90 tubes.

So I can sample it with an ADC.

From my search it's as if no-gain tube preamps are hard to find?!
  Reply With Quote
Old 9th May 2004, 05:56 PM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
For the "unity" gain block, a cathode follower with only a bias resistor will be non-linear.

CCS loading a common cathode wired 6C4/EC90 will allow you extract the "full" mu of the tube in a very linear fashion.

If you use a linear gain block with "mikes" only and feed both amplified "mikes" and line level stuff through the non-linear CF, you will achieve your purpose. A CCS loaded CF to drive the load would finish things off nicely. Use the level control as the linear CF's grid resistor.
__________________
Eli D.
  Reply With Quote
Old 9th May 2004, 06:02 PM   #3
rif is offline rif  United States
diyAudio Member
 
rif's Avatar
 
Join Date: Jan 2003
Location: Southern NJ
What an interesting question! I don't know of any, and am no expert anyway, but looking into guitar effex pedal circuits may help. IIRC, that's what the early ones did -- intentionally clip, noon-linearly amplify, etc. Probably a lot of sites out there with details.

BTW -- is the pin/scoket type the same as 12au7? Just curious.
  Reply With Quote
Old 9th May 2004, 09:32 PM   #4
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
BTW -- is the pin/scoket type the same as 12au7? Just curious.
6C4/EC90 uses a seven pin socket, ECC82 a nine pin (noval).

DUNCAN AMPS DATASHEETS.

Cheers,
__________________
Frank
  Reply With Quote
Old 9th May 2004, 11:25 PM   #5
rif is offline rif  United States
diyAudio Member
 
rif's Avatar
 
Join Date: Jan 2003
Location: Southern NJ
WOW!!!!!!!

I never really checked out that site before. It's inredible! I'd say that just for the tdsl online!
  Reply With Quote
Old 10th May 2004, 05:24 AM   #6
diyAudio Member
 
Join Date: Jan 2004
Location: nowhere
Quote:
For the "unity" gain block, a cathode follower with only a bias resistor will be non-linear. CCS loading a common cathode wired 6C4/EC90 will allow you extract the "full" mu of the tube in a very linear fashion. If you use a linear gain block with "mikes" only and feed both amplified "mikes" and line level stuff through the non-linear CF, you will achieve your purpose. A CCS loaded CF to drive the load would finish things off nicely. Use the level control as the linear CF's grid resistor.
Yo frank you catch the number of that bus!? nay, train!

Yeah it went in one ear and out the other...

CCS loading = active loads instead of resistance.
CCS

Common cathode

Quote:
If you use a linear gain block with "mikes" only and feed both amplified "mikes" and line level stuff through the non-linear CF, you will achieve your purpose.
So "CF" or cathode follower is another way of saying you have the plate of one 'preamp' tube in my case an ec90 going into the cathode of a second more linear preamplifier tube which is then loaded by an active load on it's plate to drive whatever on the end essentially giving a finished signal?
  Reply With Quote
Old 10th May 2004, 06:13 AM   #7
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
For the linear "mike" gain block, a mu stage with either a MOSFET or a 6AU6 "upstairs" will get the job done. Cap. couple the mu stage to the distortion generating block.

The distortion generating block is a simple cathode follower with only a bias resistor under the cathode. A 470 KOhm grid leak resistor is fine here. Cap. couple the distortion generator to the O/P buffer.

The O/P buffer is a cathode follower with an active load "downstairs". Again, either a 6AU6 or a MOSFET will do nicely. If you can source 500 KOhm volume controls, use them as the grid leak resistors for the buffer triodes. You could use stacks of 3X red LEDs to bias the buffer grids 6 V. below the cathodes' potential.

The unit consists of 3 stages: a linear "mike" only preamp, a near unity gain distortion generator, and a linear O/P buffer. There are 3X 6C4s plus 2 other active devices per channel.

BTW, if the distortion generator is a bit much, placing a smallish load resistor under the bias resistor will reduce the distortion level.
__________________
Eli D.
  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
Marshall AVT 50 preamp gain/distortion increase Voland Tubes / Valves 3 27th November 2010 01:05 PM
How to reduce gain of this Tube Preamplifier ? ANALOG GUY Tubes / Valves 5 22nd September 2006 03:37 AM
Have to calculate gain for typical small JFET preamplifier supernet Solid State 4 11th August 2006 11:22 PM
op-amp theory: relation between gain and distortion? Dominique Solid State 12 4th April 2006 12:03 AM
high gain 2nd order high pass active filter topology sreten Solid State 21 23rd March 2006 01:26 AM


New To Site? Need Help?

All times are GMT. The time now is 05:31 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