solid state metal preamp - diyAudio
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 31st December 2006, 09:05 PM   #1
diyAudio Member
 
Join Date: Dec 2006
Default solid state metal preamp

im wanting to make (from scratch or a kit im not fussed) a 2-channel preamp to feed into a 100watt torque poweramp to play my guitar through.
i want it preferably to have a clean channel and a dirty channel. the dirty channel should be really metal and crunchy like a high gain marshall on 11 or a dual rec.
also it needs a b,m an t eq on it as the poweramp has just a vol control.
schematics and links would be helpful.

any suggestions?

abe
  Reply With Quote
Old 31st December 2006, 09:51 PM   #2
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
You might have a look at this one, although it's a single channel with volume and master gain controls.

However, if you're wanting the 'Marshall Sound' you really need a fully valved amp - it's as much the output stages overloading as the preamps that gives the sound.
__________________
Nigel Goodwin
  Reply With Quote
Old 31st December 2006, 10:23 PM   #3
teemuk is offline teemuk  Finland
diyAudio Member
 
Join Date: Nov 2004
Location: Suomi, Finland
Plenty of suggestions, almost all guitar preamplifiers I've seen fill those terms, except the "metal and crunchy like a high gain marshall on 11 or a dual rec", which is the most important one.

My opinion: Build a clean preamplifier then make it have a switchable effects loop (i.e. selection between two individual FX loops) and stick with pedals. Most distortion circuits that really are adequate for metal tones are more complex than just fitting a couple of diodes to clip the signal. Take a look at Boss MT-2 for example: http://www.goldhand.com.pl/audio/git...ty/boss_mt.gif
Besides that diode clipping you need a lot of proper filtering post and pre. If you build a simple circuit it will quite likely just sound bad - unless it is designed for a clean tone. And with "clean" I mean a lot of headroom, not something that will annoyingly clip to rails once you pluck the strings harder. Start from having a clean circuit, that is the main sound of your amp no matter how much distortion you decide to add afterwards. Concentrate on tweaking the tone stack circuit: It has the largest effect on amplifier's tone besides the speaker system.

Solid-state guitar preamps are basically easy to design, just few clean opamp stages with moderate or low gain, some high and lowpass filtering to remove unneccessary bass and excessive high end, then insert a suitable fender/marshall/vox/whatever tone stack in between. Add perhaps few extra gain stages or buffer circuits more for FX loop and reverb. If you want more headroom or supposedly rounder clipping characters replace opamp stages with jfets or transistors. They tend to cause more distortion (even when "clean"), although nobody will likely notice a difference. All those building blocks are common knowledge to anyone that possesses even a moderate knowledge of basic electronics. Well, perhaps not the tone stack circuitry - but that is quite common to people dealing with guitar audio. If unsure, just google for "tone stack".

Anyway, any distortion in solid-state designs aimed for guitar amplification should be caused intentionally. Usually this involves enhancing or attenuating certain frequencies and using high/low-pass filtering post/pre the overdriven/clipping part of the circuit. See the "Boss pedal" example. Simple designs will likely sound bad if you aim for metal tones.

More complexity comes from designing a suitable layout, switching arrangements between channels and other circuit parts (especially with solid state switching) etc. To this part most schematics really offer no help, except by giving you ideas, of course.

There are hundreds of guitar preamplifier schematics circling in the internet. I could post you links but it's not worth the trouble since you can find them very easily if you just search. Besides, I don't keep a track of links to schematics - I rather just save all interesting designs on hardrive for further studying. Anyway, building a preamp is just as easy as I described but making the circuit have a tone you like - especially a distortion tone.... well, I believe that no-one can tell you which circuit is good for that. Be prepared to tweak the design you choose.

If you want nice distortion tone, use a pedal or build a circuit that you know has a nice distortion tone - shouldn't be a big problem to implement it to a preamp design and make it switchable, if you know what I mean. In my opinion, having these circuits on a pedal plugged to switchable effects loop (or just between guitar and amp) means more versatility. The one day you get tired to that distortion tone you can easily change it without changing the whole amp, right?

Since you already stated one preference you could start by looking at Marshall's designs: http://www.drtube.com/marshall.htm See section solid state. Also, many of their modern designs (and some of the older ones as well) use solid-state preamps. Be prepared to browse through a lot of schematics. They do look complicated but that's what you get when you need channel switching or even mediocre sounding distortion tone. Still, basically all that those circuits contain are few gain stages with carefully selected low and hipass filters and a tone stack circuit. Runoffgroove site (http://www.runoffgroove.com) also contains some very nice sounding designs - basically intented as external distortion pedals. I recall there was a circuit mimicking Mesa amplifiers there. I see no reason why few mods and some extra circuitry for clean tones and channel switching could not turn any of these designs into a preamplifier you need.

You have a task of figuring out what a certain circuit part does to the sound. Otherwise you are just blindly building a design - and possibly you end up dissapointed afterwards. This is why I implicated that if you already prefer a certain tone, use a pedal or use the amp or whatever that has the tone or copy the circuit in it. Then, schematic is just a half way there... you have to design a layout etc.
  Reply With Quote
Old 31st December 2006, 11:10 PM   #4
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
Default here's a tube fuzz circuit

this ought to give you a tube fuzz sound. it simulates a tube amp in output clipping. remove one of the transistors and it simulates tube input stage clipping.
Attached Images
File Type: jpg softclip3.jpg (19.9 KB, 1264 views)
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 1st January 2007, 02:24 PM   #5
diyAudio Member
 
Join Date: Dec 2006
i see.
i have found a jcm800 'emulator'. it uses jfets and mimics the whole amp not just the preamp so apparently it sounds rather nice. i was thinking of sticking with that as a clean(ish) preamp stage and using my boss me50 for the effects, which i was originally trying to avoid.
the thing that puzzles me about the jcm emulator is that it doesn't appear to have any clipping stages so the 'drive' must be purley overdriving the jfets. i've never heard overdriven jfets personally and i was wondering if it would sap the tone.
also, i found a 12ax7 fender emulator buffer thing also using a j201. would it be worth sticking this infront of the preamp for a bit more warmth - im a metalhead but i still like tone.
  Reply With Quote
Old 1st January 2007, 05:25 PM   #6
teemuk is offline teemuk  Finland
diyAudio Member
 
Join Date: Nov 2004
Location: Suomi, Finland
Clipping characters of both FETs, BJTs and vacuum circuits depend on the gain of the actual device, the gain setting of the circuit, DC bias point of the circuit, amount of negative feedback applied and, last but not least, on low and hi-pass filtering of the stage (post and pre). The tone of a certain device is always as much a result of the surrounding circuitry. Without seeing (and usually hearing as well) the actual design it's always difficult to comment anything about its tone, which is also a highly subjective matter:

I can tell you that I think the clipping characters of a common source JFET gain stage are not that superior over clipping characters of a transistor (or even an opamp) and some one else can tell you that they are. To my ears both clip suddenly and harshly - in circuits designed for clean tones. Then again, another common source JFET gain stage (or a common emitter BJT stage), designed to be overdriven, can sound good while clipping but to my ears it does not sound very good if I need a clean tone.

Don't believe all the hype about clipping characters of certain devices. There is some truth in it but in the end it all comes down to all variables I listed and to how they interact with each other. If you like the tone of a certain circuit then build it. It's that simple.
  Reply With Quote
Old 1st January 2007, 05:44 PM   #7
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
Default clipping jfets

actually i have a circuit that uses a jfet to duplicate an overdriven 12ax7 triode. the output waveform and harmonic content are just about identical.
Attached Images
File Type: jpg fetclip.jpg (19.8 KB, 1207 views)
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 2nd January 2007, 01:45 AM   #8
diyAudio Member
 
Join Date: Dec 2006
well ive got a lot of time on my hands so i might as well build the jcm preamp and fiddle with it a bit. i might havea crack at that tube clipping circuit from uncle jed. if none of it works ill bite the bullet and buy myself an amp.

tell me what you think of this schematic though.
Attached Images
File Type: png 4 - jcm 800 emu.png (6.8 KB, 1232 views)
  Reply With Quote
Old 2nd January 2007, 08:23 AM   #9
teemuk is offline teemuk  Finland
diyAudio Member
 
Join Date: Nov 2004
Location: Suomi, Finland
That is almost like the version of "Thunderchief" effect from runoffgroove.com that had a tonestack (http://www.runoffgroove.com/tc-tone.png). There are couple of differences - like an extra gainstage - but at least the mysterious "Electric" should have given credit to the original designers of this circuit. The low-pass filter is missing as well - that will make a difference to the tone.

There were some problems with the original design so Runoffgroove has released another updated version called "Thor", that is quite different from the original (http://www.runoffgroove.com/thor.html). The linked page discusses some issues related to the original design. You'd better read the FAQ (from the same site) as well since there is a question related to biasing problem of the old design - the circuit you linked has the same problem. There is also a mp3 sound link to the basic "Thunderchief" design that you might want to check out. I'd imagine the inclusion of another gain stage and tone controls will shape the sound quite drastically though, not to mention the exclusion of the lowpass filter.

This design has shown up earlier here at DiyAudio when someone asked how to convert it to higher (and dual) supply voltage. It was mentioned that the supply rejection of this kind of circuit is very poor and I completely agree with that. Unless you decide to run that thing from a battery or from a very stable regulated supply you need to add some filtering between stages to lower supply ripple and to prevent possible "motorboating".
  Reply With Quote
Old 2nd January 2007, 02:42 PM   #10
diyAudio Member
 
Join Date: Dec 2006
yeah i was checking out runoffgroove earlier and i was mightily impressed with all the stompox amp emulators.
but now im stuck:
if the jcm 800 is as difficult as you say, i could just make a different preamp - the uno sounds great and is a clone of a boogie so it must be good.
the thunderchief sounds nice and crunchy also but apparently putting a tonme stack in it complicates it and they go wrong. the thor sounds ok but maybe a bit too limited.
i could even use something like the marshall eighteen watt emu so i can just use a clean sound on it and pump my pedal into it.
but the toss up i think is still between the jcm 800 (and if it doesnt work, accept it) and the mesa boogie mk1.
i guess the mk1 will have more chunk.
what do you think?
  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
Diy Solid State Preamp Pocoyo Solid State 21 17th July 2007 03:53 AM
Michele's New Ideas - Solid State Preamp m_buzzi Solid State 6 30th May 2007 02:29 PM
Tube preamp vs. solid state bushroot Tubes / Valves 16 31st October 2006 07:16 AM
hifi solid-state PREAMP ... Ahmad_tbp Solid State 34 20th June 2005 10:10 PM
Solid state preamp gchrist Solid State 4 7th April 2004 10:19 AM


New To Site? Need Help?

All times are GMT. The time now is 01:45 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