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Old 8th September 2012, 03:20 AM   #11
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Anyone see anything wrong with this layout?

Click the image to open in full size.

Thanks!

Blair
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Old 9th September 2012, 03:31 AM   #12
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Quote:
Anyone see anything wrong with this layout?
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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Last edited by speakerfritz; 9th September 2012 at 03:34 AM.
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Old 9th September 2012, 03:36 AM   #13
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Which ones?

The PT is at 90 degrees horizontal out of the chokes and the outputs are at 90 degrees out from the PT.

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Blair
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Old 9th September 2012, 04:14 AM   #14
roline is offline roline  United States
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It will be quiet as a church mouse with the iron rotated..
I have scrunched them together on a couple builds.
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SO many tubes, SO little time!!!
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Old 9th September 2012, 04:18 AM   #15
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Which ones need rotating? I started cutting today.

Here is an alternate view:

Click the image to open in full size.

Blair
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Old 9th September 2012, 06:04 AM   #16
dgta is offline dgta  United States
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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.
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Old 9th September 2012, 01:58 PM   #17
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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:

Click the image to open in full size.

Blair

Last edited by deicide67; 9th September 2012 at 02:26 PM.
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Old 9th September 2012, 04:05 PM   #18
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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
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Old 15th September 2012, 03:28 PM   #19
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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
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Old 17th September 2012, 03:22 AM   #20
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Quote:
Originally Posted by deicide67 View Post
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
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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