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Old 21st April 2005, 06:44 PM   #11
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Thanks Enzo
You're a very helpfull person.
Waiting for your news.
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Old 27th May 2005, 01:46 PM   #12
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noticed the mention of the Mitsubishi M5201. This is like a dual op amp with a switch, a DC control voltage on one of the pins (DIP pin 1) selects the output from one of the inputs, and passes it to the output stage.

NJR makes two compatible parts, the NJM2120 and the NJM2121. Search mouser.com for NJM212* to get price and data sheets.

The NJM2120 has 7MHz GBw, the NJM2121 about 14MHz GBw. both of them seem like decent op amps, input offset ain't the greatest at 2 to 6mV typical. Most of the opamps in the Marshall valvestate are low-bandwidth types like the MC1458,TL071, TL072 etc. so the NJM2120 should be fine.
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Old 29th May 2005, 10:44 AM   #13
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Hi scooperman,
The valvestate is ok right now!I found 5201 directly from Marshall at 3 euros/each.
The pots were a little bit expensieve(8euros/each) but anyway....

But thanks for the info.Maybe NJM2120 and NJM2121 are more easy to find!
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Old 31st May 2005, 01:55 PM   #14
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hi resident,

I was working on a JCM900 combo amp model 4101, the Marshall marketing literature called the JCM900 their "Valve Series". It is early 90s vintage, maybe this was before they started calling them "Valvestate". The preamp circuit board is marked JMP52, it had 4 of these Mitsubishi switching op amps on the board. The previous owner zorched it pretty badly, every op amp and diode on the preamp board were fried, all the way back to the power supply rectifiers. The other parts are common, the Mitsu op amp was the only one hard to find. I bought some of the NJM2120s and also the NJM2121s just in case, after reading the data sheets I decided the 2120s were OK. With all new semiconductors and ICs in the premap, everything is fine now, it sounds as good as new.

Right, sometimes it is easier to just buy parts locally, the price might be higher but shipping costs less. Marshall might be getting selected or premium parts from Mitsubishi but I doubt it, Marshall probably bought the chip for about 0.3 euro in small quantity, maybe about 0.1 euro in large quantity. Mouser is not a big-volume distributor, in 100 piece quantity they get 0.31USD for the NJM2120, 0.24USD for the NJM2121. If Mitsubishi has discontinued the part (I could not find it on their web site) then that would explain the very high price, if you have stock then you can charge anything you want for discontinued parts.
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Old 2nd June 2005, 01:06 AM   #15
Enzo is offline Enzo  United States
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Valvestate has been around quite a while. The Valvestates are basically a solid state amp with a preamp tube stuck in there.

The 4100 series are much more tubish. Tube power amp and several preamp tubes as well as the solid state junk. They are different families of amp.
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Old 2nd June 2005, 07:03 AM   #16
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Yup.Yesterday I saw a JCM900 5881 series.
Different family from valvestate.
Four 5881 and three 12AX7 but with a lot of SS junk.

And one more thing.
Amps are not as good as they were
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Old 4th June 2005, 11:11 PM   #17
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is that true that new marshall valvestes are using only one tube in a cathode follower configuration?
I've heard they do so and I feel that the tube is added mainly to give light and for myth/marketing related issues. Sound is also crapy, harsh, solid-statish...
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Old 5th June 2005, 03:12 PM   #18
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It's one double triode(12AX7) One triode is connected as common cathode and it's direct coupled to the other which is as cathode follower.
Quote:
I feel that the tube is added mainly to give light and for myth/marketing related issues.
ooh come on now.Do you really believe this?
.....just joking.I agree.
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Old 19th March 2007, 01:48 PM   #19
Sztaki is offline Sztaki  Hungary
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Quote:
Originally posted by Enzo
Send me an email with "VS100R Schematic" in the subject line.

My email is tmenzo

then the symbol for "at"

then msn dot com

Those VS series circuits are related but not the same.
Hi Enso!

I also need your help with regard to VS100R Schematic. Is it possible to get the schem on the same way as resident got it?
I have a VS100R to repair it, but without schem it is almost imposibble.

Thank you for your help in advance.

Sztaki
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Old 19th March 2007, 02:33 PM   #20
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Hello Sztaki,
I can send it too. Send me an e-mail if you like to have it.......
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