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CJ MV75 "update circuit drawing"

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CJ MV75 "update circuit drawing"

Postby leakstereo20 » Mon Oct 15, 2012 2:48 pm

Hi,
Anyone who know whether the shown CJ MV75 drawing is correct ? Please find the "new" updated drawing at :

https://picasaweb.google.com/vbkolsen/C ... 8957941074 NEW link

The Conrad Johnson equipment/amplifiers of any kind is very difficult to find in Europe. The possibility to build a clone seems to be one way to learn more about these great amplifiers. Any help with the CJ MV75 circuit would be highly appreciated.

Best regards
Kim Hansen

Google+ changed all my links. This is a new link for the CJ MV75 drawing!
Last edited by leakstereo20 on Sun Dec 30, 2012 7:44 am, edited 1 time in total.
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Re: CJ MV75 "update circuit drawing"

Postby admin » Mon Oct 15, 2012 3:14 pm

You may want to check out the Conrad Johnson Manual and schematics thread. There are schematics for the MV75 in there. Hope that helps.

So you plan on building one of these all by yourself? That's pretty cool, you will have to let us know how it goes! :)
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Re: CJ MV75 "update circuit drawing"

Postby leakstereo20 » Tue Oct 16, 2012 2:35 pm

admin wrote:You may want to check out the Conrad Johnson Manual and schematics thread. There are schematics for the MV75 in there. Hope that helps.

So you plan on building one of these all by yourself? That's pretty cool, you will have to let us know how it goes! :)


Hello,
Thanks for the link to CJ schematics. My intension with the "update" drawing of CJMV75 was to get the best start with the MV75 Clone and some support to other CJ owners.
Most of all old schematic papers are either bad scanned or poor copy quality.

20 years ago I tried to make the CJ MV75 amplifier, and with more experience today I think my chances with the MV75 has improved.

Some valvesamplifier circuits for free at my amateur site: http://www.tubeamp.hobbysider.dk

rgds.
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Re: CJ MV75 "update circuit drawing"

Postby admin » Wed Oct 24, 2012 9:36 am

leakstereo20 wrote:
admin wrote:You may want to check out the Conrad Johnson Manual and schematics thread. There are schematics for the MV75 in there. Hope that helps.

So you plan on building one of these all by yourself? That's pretty cool, you will have to let us know how it goes! :)


Hello,
Thanks for the link to CJ schematics. My intension with the "update" drawing of CJMV75 was to get the best start with the MV75 Clone and some support to other CJ owners.
Most of all old schematic papers are either bad scanned or poor copy quality.

20 years ago I tried to make the CJ MV75 amplifier, and with more experience today I think my chances with the MV75 has improved.

Some valvesamplifier circuits for free at my amateur site: http://www.tubeamp.hobbysider.dk

rgds.


I went and checked out the website you suggested. There are some very fine examples of some great tube amps. I think those projects are a little beyond my expertise, but nonetheless I can definitely see the motivation to build some of the units. It would be great to go through and fabricate the entire unit from start to finish.

Let us know how you make out with CJ MV75. I think that if I ever did build an amp, it would be something based on the CJ line as I have such a high regard for their sound.
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Re: CJ MV75 "update circuit drawing"

Postby leakstereo20 » Thu Oct 25, 2012 1:19 pm

admin wrote:
I went and checked out the website you suggested. There are some very fine examples of some great tube amps. I think those projects are a little beyond my expertise, but nonetheless I can definitely see the motivation to build some of the units. It would be great to go through and fabricate the entire unit from start to finish.

Let us know how you make out with CJ MV75. I think that if I ever did build an amp, it would be something based on the CJ line as I have such a high regard for their sound.


I don't think that the showed valveamplifiers at Tubeamp are beyond your expertise. 20 years ago I started with the basic well known CJ MV75 design, and with a voltage/ampere meter I managed to get 40Watt sinus and a frequence range from 10Hz to 56kHz out of a pair of EL34 with 450Vdc on the outputtransformer center. I had never tried to build a valveamp before this.

Best regards
Kim
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Re: CJ MV75 "update circuit drawing"

Postby admin » Fri Oct 26, 2012 10:12 am

leakstereo20 wrote:
admin wrote:
I went and checked out the website you suggested. There are some very fine examples of some great tube amps. I think those projects are a little beyond my expertise, but nonetheless I can definitely see the motivation to build some of the units. It would be great to go through and fabricate the entire unit from start to finish.

Let us know how you make out with CJ MV75. I think that if I ever did build an amp, it would be something based on the CJ line as I have such a high regard for their sound.


I don't think that the showed valveamplifiers at Tubeamp are beyond your expertise. 20 years ago I started with the basic well known CJ MV75 design, and with a voltage/ampere meter I managed to get 40Watt sinus and a frequence range from 10Hz to 56kHz out of a pair of EL34 with 450Vdc on the outputtransformer center. I had never tried to build a valveamp before this.

Best regards
Kim


Do you have a rough idea of how much all the parts cost? It's hard to justify building a new amp when I have the CJ Evolution 2000, this would be more of a "fun project" than anything else.
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Re: CJ MV75 "update circuit drawing"

Postby leakstereo20 » Fri Oct 26, 2012 3:01 pm

admin wrote:

Do you have a rough idea of how much all the parts cost? It's hard to justify building a new amp when I have the CJ Evolution 2000, this would be more of a "fun project" than anything else.


An estimated price would be:
http://store.triodestore.com/mq782.html 107,95$ for a powertransformer
http://store.triodestore.com/a4dyoutr43oh.html 134,95 x 2 for outputtransformers
Both very excellent transformers for the CJ MV75 circuit...I know Hammond has some fine transformers as well.
In Europe I would say (might be slighly less expensive in US) 160$ for hardwiring material as PCB with silverpins, resistors, capacitors a.m.
As valves/tubes are concerned you might choose Sovtek to start with.
Buy a aluminum plate 30 cm x 30 cm place it in a woodframe for less than 50$...take your time and drill the holes.
The main idea with DIY is, (as I see it), that you can buy the stuff when you can affort to spend the money , and get a well sounding amplifier for low cost :P
Secondly ..when your amp plays "star sprangled banner" with Jimi for the first time, you will be proud in more than one way :P
If you start then choose the well known Conrad Johnson MV75 circuit.. it will work...not my update drawing, I have checked the circuit on a test board and there are some circuit mistakes. I shall come back with some changes.
best regards
Kim
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Re: CJ MV75 "update circuit drawing"

Postby leakstereo20 » Sat Oct 27, 2012 4:17 pm

leakstereo20 wrote:
If you start then choose the well known Conrad Johnson MV75 circuit.. it will work...not my update drawing, I have checked the circuit on a test board and there are some circuit mistakes. I shall come back with some changes.
best regards
Kim


There are one wrong connection between R23 and R24 on the first " new drawing" of MV75. If the wire from 6CG7 pin2 is connected to the midpoint of R23 and R24 the phasesplitter will not work. the wire from 6CG7 shall be connected to the 1M , R28. The other end of R28 goes to 6CG7 pin7 and also the 0,47uF from pin 7 to ground. see new MV75 drawing:

NEW link for the update drawing of Conrad Johnson MV75 amplifier plus the KJH MV45 modification: https://picasaweb.google.com/vbkolsen/C ... fiedToMV40
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Re: CJ MV75 "update circuit drawing"

Postby tvr2500m » Wed Mar 12, 2014 8:33 pm

I bought an MV-75 as a kid. It was my first "real" piece of audio gear, and C-J was a new, fledgling company. An upstart. And doing TUBES! I remember the MV-75 was all the rage. I still have that amplifier, though I had it updated to an A-1 by the factory, then took a little further by it's original co-designer and C-J technical director, Bill Thalmann, who is now at his own shop, Music Technology in Virginia. My PV-12A is there right for him to repair.

I'm selling my MV-75. It's in almost new condition. If there's anything I can do to help document this amp for you, let me know. I do have some schematics and parts lists, but they're the ones that've been circulating around forever.
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