bargain preamp (marshall 9001)

[gwEm]

check out this guy from 1989. it was somewhat of an ebay bargain, and i can hardly believe it was so cheap.

it has three channels:

R1 - 98% clean
R2 - typical marshall crunch
L1 - diode pedal boosted lead (something like a tubescreamer or SD-1)

and you can also select in an FX loop and/or 5 band EQ.

the default valves were some sort of no-names and they weren't that great, so i put in 3 JJs i had spare. channel R1 uses V1, R2 uses V2, L1 uses V2 and V3. the JJs added lacking note definition to the R1 and R2 channels. quality of the components is pretty decent - mostly TL072 opamps, which I like. there are some less good opamps in there, though they don't seem to be on the main signal path. good capacitors were used too, but i haven't checked if there are any electrolytics are on the signal path.

the clean channel is really nice, if you dig in you can get it to break up a little. the crunch channel is also really nice, though it doesn't clean up when rolling down the guitar volume in quite the satisfying way my jmp50 does. it does clean up, but then the volume is rather low. power tube compression may help here. the lead channel isn't quite to my taste, you can't really use it for riffs or chords as the note definition isn't what it could be. it is good for shred and single note leads though as it is rather smooth sounding.

the eq is decent enough. when you activate it, the overall volume drops which is dissapointing. it has 5 bands, which you'd think would give you alot of flexibility - an it does - but those 5 bands are interactive in the same way a traditional marshall eq is - which removes some of the benefits. i've been using it as a sort of mid boost.

so far i just played it through the input of my lead12 combo - not the best probably. but having said that it does sound good. it has a cabinent simulator which i'll try later into a desk or my multitrack.

i'm very tempted to get a cheapy SS power amp to use with it, though i know valve would be better. this preamp is nice sounding, and you can't argue with the price, but the main reason i got it was an experiment due to the low price. more later on the cabinent simulator.

[sgmypod]

ahh remember these

[gwEm]

was looking at the schematic just now. its slightly confusing, but it seems like the lead channel *isn't* diode boosted. it has two drive controls - similar to a jcm900 slx. i'll play with it more later. perhaps a high quality valve in V2 might help too.


edit: ah there is diode clipping on the valve board itself. the schematics seem a bit different to what i found by removing valves though, in terms of which ecc83 is used on which channel

[HTH AMPS]

I've recently got one of those preamps too (£65), mine had three Mullard ECC83s in too  :D

The EQ section on mine RAISES the volume when it's engaged.  I suppose it might lower the volume if you're scooping the mids.

I put a poweramp-input on one of my amps and it sounds great.

[FELINEGUITARS]

I used to have one at one time - didn't quite do it for me though.

[gwEm]

I've recently got one of those preamps too (£65), mine had three Mullard ECC83s in too  :D

The EQ section on mine RAISES the volume when it's engaged.  I suppose it might lower the volume if you're scooping the mids.

I put a poweramp-input on one of my amps and it sounds great.

you got yourself even more of a bargain than me :)

i set the mids flat when i engage them - lowers the volume on mine definately, maybe a different revision of the circuit?

i'm going to try removing the clipping diodes and see if it improves the tone more to my liking. still not 100% convinced by the lead channel.

[gwEm]

it has a cabinent simulator which i'll try later into a desk or my multitrack.

cabinet simulator was pretty cr@p. though tweaking the EQ can make it more tolerable

[gwEm]

i'm going to try removing the clipping diodes and see if it improves the tone more to my liking. still not 100% convinced by the lead channel.

i removed the d1/d2 clipping diodes before work. it was a good mod. the lead channel is much improved - its pure valve fury now. the quality of r2 is also improved, but this channel misses a bit of saturation now as a result of removing the diodes.

going to investigate increasing the input opamp gain for r2, to get some drive back. may also replace ic1 with a burr brown

[HTH AMPS]

your lead channels settings aren't a million miles away from mine - try it with gain1 at 1 o'clock and gain2 between 1 o'clock and 3 o'clock.  

I find that the hi-mids are where the typical Marshall voicing is found, I crank that fairly high.

btw, what amp are you using this into?

(edit): I like the 'voice' control on this preamp - if you look at the schematic, it's a TMB tonestack with the bass and mids fixed on full with only the treble working, I quite like it.

[gwEm]

your lead channels settings aren't a million miles away from mine - try it with gain1 at 1 o'clock and gain2 between 1 o'clock and 3 o'clock.  

I find that the hi-mids are where the typical Marshall voicing is found, I crank that fairly high.

btw, what amp are you using this into?

i'm still using into the input of a solid state combo :/ i need to get some sort of power amp (if i decide to keep it).

i'll try your setting later! so far i homed in on gain1@3o'clock and gain2@12o'clock. gain2 seems to make things a bit thicker/darker/muddier depending on how high i set it.

the R2 and Lead voicing controls are really useful i'm finding.

[HTH AMPS]

I think your problem is that you're using it into the front end of another amp - you've got your signal going through another full preamp with all the (re)voicing that goes with it.  Does the amp have an effects loop? - just plug the 9001 into the effects return.   

NOTE: depending on the location (circuit-wise) of the master volume on your SS combo, you may be running the output stage flat out, so set the volumes on the preamp low at first.  I remember an old Peavey combo of mine ran the output flat out if you ran a preamp into the effects return - the whole house got a very loud shock when I plugged that baby in, ha ha.

[gwEm]

I think your problem is that you're using it into the front end of another amp - you've got your signal going through another full preamp with all the (re)voicing that goes with it.  Does the amp have an effects loop? - just plug the 9001 into the effects return.   

NOTE: depending on the location (circuit-wise) of the master volume on your SS combo, you may be running the output stage flat out, so set the volumes on the preamp low at first.  I remember an old Peavey combo of mine ran the output flat out if you ran a preamp into the effects return - the whole house got a very loud shock when I plugged that baby in, ha ha.

i'd love to do this. though my 2204 doesn't have an fx loop, and nor does the combo :/

does it have to be a specifically guitar voiced power amp? or can i just use a studio/PA amp into my cab?

[HTH AMPS]

I think a studio/monitor poweramp wouldn't sound great for guitar - it'll be voiced to be flat from 20Hz - 20KHz (at least).  Either look for a cheap guitar poweramp (HH would be awesome, that's what EVH used but they're not really thought of as a great 'brand').

Personally, I'd put a poweramp-input in your 2204 - just break the connection before the master volume and inject the signal from the 9001 there.  Use a switching jack so that the signal is complete as before when there is no jack inserted, and when the jack is inserted, the connection from the tonestack is broken.  It works a treat, did this myself with a similar amp. 

[sgmypod]

Powerblock they work well

[gwEm]

Personally, I'd put a poweramp-input in your 2204 - just break the connection before the master volume and inject the signal from the 9001 there.  Use a switching jack so that the signal is complete as before when there is no jack inserted, and when the jack is inserted, the connection from the tonestack is broken.  It works a treat, did this myself with a similar amp. 

i've been tempted many times. the thing is, i use both speaker outputs and can't really sacrifice that hole in the case. not keen on drilling another one due to resale value.

thanks for the tips on h&h and that crate.

(i also wonder about modding a valve junior or my combo for an effects loop. it should be quite easy to add to either in the same way)