erlendg

Got an 9001 preamp, no footswitch.
Anyone knof in Any of the inproduction switches will work?

Please help........

MKB

I have a 9001 also, and am afraid none of the current footswitches I've seen will work due to the sort-of unusual connector (a latching 6 pin DIN). However, it's not very hard to build one; the schematic is available on the internet (it's on the 9001 schematic page with the power supply, in the upper left hand corner), it's just a SPDT latching footswitch and an LED with current limiting per function. I built one for mine and it works great. It would also be possible to modify an existing footswitch if it has the proper switches and cable. Here's the part number for the latching DIN connector that works with the 9001:

Amphenol T3424 501, Mouser p/n 523-T3424-501

http://www.mouser.com/Search/Refine....user_Wildcards

erlendg

Thanx mike.

Got the schem, gott the tools, got most of the parts. Only missing the plug.

tazzboy

I've always wonder what this preamp sounds like?

__________________
tazzboy

MKB

Hard to describe in words. They definately have their own sound.

Clean channel (R1): Very clean tones, and can get very bright. The clean tones are excellent, and it works well with pedals.

Crunch channel (R2): Almost useless. This mode sounds like a bad distortion pedal, especially in the bass. I have tried quite a bit to tweak this channel with no success. There's just not a good tone there.

Lead channel: This one sounds, well, Marshally. The channel has two gain knobs, one is voiced trebley and the other is more mids and bass, you can mix the two for different sounds. You can get some very good sounds out of this channel. It has more of a modern JCM900 sound to me, not so vintage sounding.

The preamp has an interesting circuit layout, mostly op amps, with three 12AX7 tubes running off high voltage. All of the channels have at least one tube amplification stage. The tube arrangement is unusual for Marshall, they use a topology called a mu-follower (where a tube stage replaces the plate resistor) for some reason. This makes the distortion tones sound slightly softer than you might expect. But overall the lead channel sounds much like a Marshall in tone. FWIW, the preamp uses diodes in all distortion modes. The effects loop and five band EQ work very well, and are footswitchable.

I made some modifications to mine, basically changing the distortion diodes to mosfets, and changing the mu-follower arrangement of the tubes to the standard cathode follower (like most other Marshalls). This actually helped the tone quite a bit, especially in the lead channel. This modification gives it almost too much solid bass in the low end, and not muddy bass either. Overall I really like it, but it is seeing a lot of closet time since I got my Vintage Modern...

tazzboy

What kind of Power amp were you using?

__________________
tazzboy

MKB

Mostly an ADA Microtube 200 with either a Marshall slant cab with greenbacks, or a 1X12 Thiele cab with an EVM12L. I also used it straight into a H+K Redbox with good results.

BTW, I forgot to mention that the cab emulation in the 9001 is HORRIBLE. Totally useless. The Redbox was WAY better.

tazzboy

Ok. I have seen these go for a less on Ebay. less then the JMP-1 of course I don't know how they (9004 vs JMP-1) would compare against each other.

__________________
tazzboy

AmpHead

This system is great...many different sounds possible. I have several of them. Very underrated because of the switch in popular gear back in the day.

I have a extra 9001 Pre Amp for Sale. 225.00 Obo. Email me. I also have a extra 8080 power amp I'd sell for 200.00 Obo . This Combo sounds quite good.

Cheers

bridge33

Hello.
I have Marshall 9001 pre and sound on lead channel is't good for me.
To much bassy and muddy, palm muting sound is terribly.
Can you write how changing mu-follower to cathode follower and install mosfets? Scheme etc.
It's very importantd to me.
Please help me.
Best regards.

Generaly adressed to MKB :-)

MKB

Hi bridge33, I'll post the mods as soon as I can dig out the notes and get them written up. It might be a week or so though, gotta go out of town for work.

bridge33

OK, thanks MKB.
I will waiting impatience.
http://www.marshallforum.com/images/smilies/wave.gif

rockrelic

Hi Gang,
I a n00b in these parts and am very interested in a 9001 or 9004 tube preamp to compliment my 100w Valvestate.

Is it worth the purchase to enhance the sound?

When I was younger, I had a straight Marshall 100w head with no master volume. I had a Tom Scholz "Power Soak" and would crank her up and lower the volume on the Soaker.

But now my kid is 14 and uses my Valvestate and it sounds shallow. The tube warmth that I remember is gone. The kid is a great guitarist and I want him to have the vintage sound but not by having to go out and get a vintage head.

(He's also using an MG412 cab, which is not as good as the old cabs....by a long shot.)

So...is it a good idea to use a Marshall Preamp to reproduce the sound I remember so fondly?

bridge33

Hello rockrelic,
Marshall MGP 9004 is not tube preamp!
MGP 9001 it's tube pre with 3x12ax7 on board.
Produce great clean and crunch but lead channel on more gain is so-so.
Stay good to solos. Lead produce marshall in tone sound, like MKB say.
Clean and crunch is really good.

Angus80

Hi guys,
i bought a 9001(for 190 €) almost 2 weeks ago...i had only 2 studio session with my band to try it...well, it sounds GREAT!
I'm using it with a Marshall 8004 power amp and 2x1922 with a custom Jackson...
i would like to build a footswitch by myself like you MKB...
I found the schematic in the net...i'll try to made it!

Thanks, bye.

p.s. MKB did you take some picture of your work?

bridge33

Do you have a bit of time to presente your modifications, MKB?

MKB

Hi guys, just got back from being out of town. I'll try to get the schematic scanned this week and post it here. Sorry for the delay...

Robert Correll

I just bought a 9001. I haven't received it yet, but am looking forward to testing it out and recording with it.

I don't have a rack power amp (yet?), so I will be taking the line out through one or another speaker cab sim (possibly - can't decide yet and looking into building my own - I have a mono Palmer PDA-03 but a PGA-05 is about a grand) and into my mixer. I may route it through my Fender Blues Junior. Would be mono. Lots of options for tone.

I am also interested in the schematic - looking to build my own footswitch.

Thanks. Nice meeting everyone.

__________________
www.robertcorrell.com

bridge33

hmmm... footswitch, you say.
Here you go Robert:
http://www.drtube.com/schematics/marshall/9001-2.gif


PS.
Robert Kubica is the best F1 driver in this season :-) !!!

Robert Correll

Thanks for the footswitch schem, bridge33.

I have a small clip posted on my Web site (see link in sig). Very short piece I worked up to try out the three channels of the 9001. Very promising for me. An older sound that has a classic feel. I haven't had the 9001 very long but I think it's going to work out well. Very happy I got it. I had been working with a Fender Blues Junior. Nothing wrong with that amp, but this is more of the tone I have been looking for.

Playing the 9001 alone is pure fun, but when I was working to fit the three sounds together (the challenge of song writing as opposed to noodling around) I had to fiddle with things. Mainly taking extra stuff out of the path. For crunch, I set my drive and voice only. Sounded better in the mix with no EQ on the box at all. Surprised me, as the path was Guitar->Tone Press compressor->9001 with no EQ or effects->Yamaha MG12/4 mixer->M-Audio Delta 66->Pro Tools M-Powered. Running a cab emulator in software with some mixing magic. I think that's a testament to the good tone inherent in the 9001.

I should say tube 1 was a good one when I got it but I replaced and upgraded tubes 2 and 3 last night.

Robert Correll

__________________
www.robertcorrell.com

tazzboy

That's not bad I was just wondering if you clips with like Clean, crunch, lead channels by themselves. Cause I wanted to hear what they sound like.

__________________
tazzboy

Robert Correll

As it turns out, part of that recording (clean) is ok, but I re-recorded the other two tracks (crunch and lean) for this version and didn't realize something was going goofy in the 9001 until a few days later. My first shot at this (unposted) sounds a lot better.

I was practicing/playing afterwards and just wasn't happy with it. I couldn't get the same range of tone and was becoming really annoyed. Felt like maybe it wasn't as good as I thought.

At the same time, I noticed I wasn't getting the same gain out of it. Then I started cranking the drives and levels in the lead channel and realized something was really wrong - no gain. I remember when I first plugged the 9001 in I had to turn everything down because it had a lot of muscle.

Then I remembered that when I was replacing the tubes I saw what looked like some light discoloration on the circuit board. I opened it back up and took a closer look this time and saw that there was burning under a few resistors, a capacitor, and the bridge rectifier (BR2) that goes to the valve heaters.

I worked to get the board out of the case so I could see underneath, and it was really obvious the rectifier had gone kaput. The two resistors on top looked sort of fried, but checked out ok on a multimeter. I ended up replacing the resistors and capacitor just to be safe and have the bridge rectifier on order.

It's a 200V 6amp BR62, and I read somewhere else that upgrading to a 10amp rectifier helps. Problem with that is, space. I will try, but the 10amp version is a .770 inches while the 6amp fits nicely where it should - .620 inches.

When I get that installed and everything back together in I should be back in business.

Robert

__________________
www.robertcorrell.com