Discussion in 'Marshall Amps' started by NewReligion, May 1, 2012.
Will I like it? Sorry texting from my iphone
You should get it and try it and let us know.
Hey thanks for the input.
I am guessing it is designed after both, the 2100 & 4100 series JCM 900 circuits?
I have one, it has 3 preamp tubes in it, an effects loop, I think it sounds ok, I had it hooked up to the 9005 tube poweramp...until the 9005 tubes went..haven't replaced em yet. I then tried it with a Carvin 100 watt tube power amp...sounded good, but not as good as a head( dsl 100 or jcm 800kk.The footswitch is hard to get also. The switches seem kinda cheap, has a shared eq with the channels. I think I paid $200 for it and $350 for the poweramp. Once ina while I'll play with it...but I prefer a head these day's!
NR try it if it's cheap...don't think you'll like it as much as your 800..you've bonded with that one!
Its the preamp at the top of the rack..below the DR, ps the 9005 is REAL heavy to lift
I've had one of these for awhile, it is an interesting and unique animal. It is mostly an all-tube circuit, but does have a pair of diodes in the crunch channel. Perhaps the most interesting part about it is the tubes are connected in a very unusual way; one half of the 12AX7 is used as a current source for the second half (known as a SRPP circuit). Here's an article on the topology:
The Valve Wizard- SRPP
I have never seen any other Marshall (or any other guitar amp at all) that uses such a circuit. The circuit is widely appreciated amongst the hi-fi crowd though.
So how does it sound? The clean sound is very nice, can get clear and bright. There is a treble control on the clean channel that can be adjusted through the top of the case with a screwdriver (the front panel tone controls are active and post-distortion).
The crunch channel is the most useless tone I have ever heard from a Marshall. It's just bad. Very plain and dead sounding, like a solid state amp. No matter what I did, I couldn't get it to sound useful (although a pair of diode connected MOSFETs helped a little).
The gain channel is interesting; it has two drive controls and can radically reshape the tone of the channel by varying the two settings in relation to each other. The stock circuit is a bit soft sounding, not as hard hitting as most other Marshalls. It is certainly worth a try as you might like it, and it has a much different tone than many Marshalls.
I did modify mine by changing two of the tube stages to a standard configuration (common cathode with cathode follower). This IMHO really improved the tone, and made the distortion channel hit much harder with no softness. It was a good tone, but I don't use it any more and don't miss it. I plan someday to put it back stock and sell it.
One other thing; the 9001 speaker compensated recording out gets the award for the most useless circuit on any Marshall product. Words can't describe how bad and useless it is. So, if you are considering buying a 9001 for this feature, don't. The one in the JMP-1 is far, far better.
Thank you gentlemen. I found your input useful and think I will avoid the 9001. I have owned a JMP-1 in the past and understand that it is based on the 4500/4100 circuit. It sounded "okay" but I did not care for the set digital incriments as I prefer attenuating knobs much more being the tone tweaking freak I am.
Thanks again for the fast responses.
If I recall, not many people or artists even used the preamp. I think Tony Iommi was one of the very few artists who used the preamp, and it was only for his live setup.
Hi I have just got a 9001 pre- amp & it goes to a 9100 head & 2 1922 cabs but to note a thing I noticed & did when the pre amp arrived it had chinese valves in it & I thought man I have got a lemon here!! My old pre-amp & Power has older Mullard & Sylvannia valves that I had collected.
I changed them in the pre-amp & it came to life very nicely. I will note that the crunch needed a little more oompf. This was improved with the use of the eq channel being on. I use a les paul & a strat & I don't play metal so much anymore the band I am in plays good old Aussie Pub rock I get the sound I am after with this setupo If I do play metal I use a wampler Pinnacle that gets me in that zone. Anyway haven't tried the speaker cab emulator yet but the FX loop is a bit finicky but I am only after the drive from it.
After digging around the web yesterday to see if anyone else has done any work on this issue. Apparently the clipping diodes on the input of V2 cause the nastys in the crunch channel. In this forum (Vintage amps bulletin board) it also said that putting a 5751 In V1 & Mullard in V2 & V3 a jj & that combination gave a better result. I have been experimenting with an old Marshall origional issue guvnr pedal & can get a good result also but I do have the gain down. Seems all Marshall things like one another!!!
The solutin for the diode clipping was to take them out. I am consulting a tech today & may elect to put a switch to turn off or on as I say I am happy with the tone I am getting. The only problem is the more I turn it up the better it sounds!! I do think to old mullards are a good investment for any Marshall valve amp. Rock on
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