Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Marshall JCM900 2500 preamp
Marshall JCM900 2500 preamp
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 26th October 2011, 11:02 PM   #1
hpupo is offline hpupo
diyAudio Member
Join Date: Feb 2011
Default Marshall JCM900 2500 preamp


I am trying to make sense of the preamp for a the marshal JCM900 2500 (http://www.drtube.com/schematics/mar...d0109-iss9.pdf). I have a few questions:

- why the two zeners at the input?
- One leg of c14 is connected to gnd and the other to the top of the input connector through something called "link". Is this link a contact? If not, what is c14 actually doing?
- VR1 is connected to the Cathode of V1b through c15 and to the grid of V1b. What exactly is it doing to the tube? Also, D1 is part of the same circuit. That is operating as a limiter correct?
- Can someone explain to me what kind of feedback C16 creates?
- I read on a bunch of places that Vr2 "bypasses" the rectifier BR1. I am assuming that basically, on its lowest setting it attenuates the signal enough so that the bridge will not clamp it. Is that assumption correct?
- lastly, and i am ashamed to ask this, but what does c6 does to the circuit on V2a?

Thanks all
  Reply With Quote


Marshall JCM900 2500 preampHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Marshall JCM900 2500 preamp hpupo Instruments and Amps 9 6th December 2014 09:12 PM
Marshall AVT 50 preamp gain/distortion increase Voland Instruments and Amps 3 27th November 2010 01:05 PM
Parasound 2500 AV Controller preamp doerfast Swap Meet 0 23rd March 2009 05:48 AM
Output tubes on a Marshall JCM900 Netlist Instruments and Amps 0 11th September 2006 02:55 PM

New To Site? Need Help?

All times are GMT. The time now is 09:43 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio