Hi guys,
There have been quite a few threads about people rebuilding these. One of the most mentionable is Bricktop's build on AudioKarma. Very nice job!
Anyway, I got one of these recently and I am about to pursue my iteration of this good fun. I'm adding a separate grid supply, and chokes in the PS, etc.
I'm waiting for my donor amp to arrive, so I figured I would ask if someone has the L X W dimensions of the power and output transformers.
Also, if someone here who may not be browsing the classifieds has an extra MO-200 they may be willing to part with, I may be interested.
Here is what I think my layout could look like if the power and outputs are not too big.
Thanks!
Blair
There have been quite a few threads about people rebuilding these. One of the most mentionable is Bricktop's build on AudioKarma. Very nice job!
Anyway, I got one of these recently and I am about to pursue my iteration of this good fun. I'm adding a separate grid supply, and chokes in the PS, etc.
I'm waiting for my donor amp to arrive, so I figured I would ask if someone has the L X W dimensions of the power and output transformers.
Also, if someone here who may not be browsing the classifieds has an extra MO-200 they may be willing to part with, I may be interested.
Here is what I think my layout could look like if the power and outputs are not too big.
Thanks!
Blair
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The transformers are all about the same size, approx. 4"x4.5" footprint and 3.5" high above the chassis as installed (end cover facing up).
Not clear what you propose to do, are you splitting an MO200 into 2 separate MO100 monoblocks? If so, you need another PT. A stereo pair on a single chassis could use a single common PT.
Not clear what you propose to do, are you splitting an MO200 into 2 separate MO100 monoblocks? If so, you need another PT. A stereo pair on a single chassis could use a single common PT.
I have 2 MO200's waiting for my attention. One of the problems I find with this amp is the massive amount of wieght the chasis has to support. One of my amps is earlier than the other....one amp does not have factory installed chassis reenforcment while the other as factory installed chasis reenforceement. My intention was to add to the existing chasis a rack mount face plate with side panels that would help stiffen the unit up.
I like the Dynaco Mark VI layout. Notice the rack mount faceplate with the reinfoced side panels. I think I am leaning more to making them mono blocks to give me more room to work in. There's a lot of rack mount related faceplates, shelving, and side supports out there so maybe I'll kick start the project once I find the right case.
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yes...big time..transformers and inductors need to be 90 degrees out of phase from each other.......when you stack them like that weird stuff happens. take a look at this amp...notice how closely spaced trannies are 90 degrees out of phase. also...I would mono block this..and use some really decent caps like on the pic I posted.
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The original amp is very crowded. I fail to see the point of building a new amp with the same parts and even more crowded.
Build it on a much larger chassis, or 2 mono chassis, and allow some room for air circulation/cooling. And as said, no 2 adjacent transformers/chokes should have the cores parallel. In the original MO200 the OPTs are parallel, but they carry the same signal (mono) so any cross-coupling is not harmful.
Build it on a much larger chassis, or 2 mono chassis, and allow some room for air circulation/cooling. And as said, no 2 adjacent transformers/chokes should have the cores parallel. In the original MO200 the OPTs are parallel, but they carry the same signal (mono) so any cross-coupling is not harmful.
I see and understand the core orientations. The end goal is to make these mono just like the original. The chokes should not be an issue like they are. I've done that before with little to no consequence.
This chassis is 12X16, so larger is not really in the cards.
In the images posted of amps, granted the outputs are separated by the PT, the cores are parallel also.
Here is an image of an amp I built about 5 years ago that was dead quiet even though the OPTs were parallel and very close:
Blair
This chassis is 12X16, so larger is not really in the cards.
In the images posted of amps, granted the outputs are separated by the PT, the cores are parallel also.
Here is an image of an amp I built about 5 years ago that was dead quiet even though the OPTs were parallel and very close:
Blair
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Looking at the suggestions, minus the OPTs because I do want to eventually wire this mono, the reason for the two 193Q chokes is that I am afraid that one is not sufficient for an 8 pack of EL34s.
I could easily, if I used one, rotate it and free up quite a bit of space. Will the 193Q handle the current for 8 EL34s? It is 10H at 500mA.
Thanks,
Blair
I could easily, if I used one, rotate it and free up quite a bit of space. Will the 193Q handle the current for 8 EL34s? It is 10H at 500mA.
Thanks,
Blair
Nobody? If I understand correctly, the higher the plate voltage you go, the lower the bias point. So, with 650-680V on the plates, I figure it will probably be between 25-35mA per tube.
I do not know how to calculate the max current draw from each tube at full swing. If it is 60-70mA, then a single 500mA choke should work even though it may be pushing saturation at full tilt.
The thing is that I have 4.5K primaries, so I'm trying to decide on a quad of KT88s or and octet of EL34 before I start punching holes. I think both tubes will work just fine into the load, but the choke is the limiting factor. It will easily handle a quad of KT88 or KT120s, but the EL34 seems like it may be pushing it.
Thanks!
Blair
I do not know how to calculate the max current draw from each tube at full swing. If it is 60-70mA, then a single 500mA choke should work even though it may be pushing saturation at full tilt.
The thing is that I have 4.5K primaries, so I'm trying to decide on a quad of KT88s or and octet of EL34 before I start punching holes. I think both tubes will work just fine into the load, but the choke is the limiting factor. It will easily handle a quad of KT88 or KT120s, but the EL34 seems like it may be pushing it.
Thanks!
Blair
Would like to join the discussion but I'm not sure what the question is? I have an MO 200 and thought I would build it into a stereo one day, so your quest is more than academic to me.
If the guestion is about the choke one could look emperically at the Dyna ST 70 with a 225 ma choke feeding two pairs of EL34's plus the driver circuitry (and an preamp, if you choose to use the provided octal plug). In the Dyna application the EL34's are running 50 ma each. At you higher voltage with much lower current a 500 ma choke would not have any difficulty feeding eight EL34's by themselves. (Of course provided that it is a true 500 ma choke that could handle the high voltage.)
The decision between EL34 and KT 88 or 120 is a matter of choice and economics. Some golden ears hear a difference; I have not, yet. An octet of EL 34s will like cost you less than a quad of good KT 88's or KT120's. At the higher primary impedance presented to an octet, power and distortion should be lower.
Sorry if I missed it but you will need a higher power/amplitude driver to drive an octet of EL34's , or quad of KT's, than an octet of original 8047's
My advice, gained from experience, is: "don't think 'ultimate amplifier' now, as it is a journey"? I have built many amplifiers and there is always a new (old discovery) to try out.
Hope this contributes.
Best wishes,
Francois
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