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Old 2nd January 2018, 03:45 AM   #21
kasanay is offline kasanay  United States
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Quote:
Originally Posted by PRR View Post
But 105mA Peak. The most peak in the smallest bottle of any TV-shop tube.
<snip>
PRR,
Thank you for all the great information.
My comment about the 1030/30 was just a wild-*** guess. I am not yet capable of making accurate calculation on audio amplifiers. I am trying to learn as I go but most times, I must lean on folks like yourself to help me through any issues I come across.
The preferred speakers were wired for 32 ohms. According to the gain charts, 16 ohm and 22 ohm drivers were also acceptable.
I'll post the schematics and charts, shortly (I think you will find them interesting). A review and any comments would be appreciated.
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Old 2nd January 2018, 03:58 AM   #22
kasanay is offline kasanay  United States
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Originally Posted by TonyTecson View Post
Hi Kasanay, do you have any documentations that we can look at? links?
Tony,

Here are the schematics, parts lists and charts.
If you are familiar with the Futterman family of OTL amps, you will see these are very similar to the 12B4 amps he built. I think the biggest difference can be seen in the power supplies (and the number of tubes).

Thanks,
Joe Y
Attached Images
File Type: png B-603 Power Amplifier.png (968.9 KB, 491 views)
File Type: png B-603 Power Supply.png (816.4 KB, 474 views)
File Type: png B-603 Charts 1 thru 3 Page 001.png (549.3 KB, 451 views)
File Type: jpg B-603 Charts 1 thru 3 Page 002.jpg (167.6 KB, 441 views)
File Type: jpg B-603 Charts 1 thru 3 Page 003.jpg (142.9 KB, 425 views)
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Old 2nd January 2018, 04:00 AM   #23
TonyTecson is offline TonyTecson  Philippines
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thanks kasanay, 12b4 i think came after 6S4 i have both tubes in my stash...

i also made an 8 ohm to 32 ohm auto-traffos as per Patrick Turner's recommendations..
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Old 2nd January 2018, 04:04 AM   #24
kasanay is offline kasanay  United States
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Quote:
Originally Posted by kevinkr View Post
Presumably it is based on the Futterman design. I imagine all of those electrolytics now need to be replaced, and there are a lot of them.

It probably sounded pretty good, no one would have gone to this amount of trouble at that time for any other reason.
Kevin,
As I posted in another reply, these are VERY similar to the the Futterman 12B4 amps.
MP was building these at (basically) the same time that Julius was building his.

Thanks,
Joe Y

Quote:
Originally Posted by smoking-amp View Post
Looks like it says:
MP Engineering Co. Fairfield ? Conn. <snip>
Smoking-amp,

There are no fans on the amps.
These were indeed, marketed (to a few very wealthy people). Mirko Paynko designed, built and installed these and many other systems in fine homes and institutions across the country. He was in business from the 30' until some time in the 60s.

Thanks,
Joe Y

Quote:
Originally Posted by smoking-amp View Post
You are right of course, it CAN be done. <snip>
Don't discount this design too quickly. I know a fellow who ran his amps for many years. I don't know how reliable they were, but this fellow has the means to replace them with any system on the market if he wanted.

The photos attached show a similar pair of MP OTLs that were sold on the bay a few years ago. The second shot is of a pair that are owned by Mathew Polk of Polk Audio. He reportedly prefers these over several others at his disposal.

Thanks for your interest,
Joe Y

Anybody interested in learning a little about the guy that designed these amps, check out the story in the Sept 1957 High Fidelity mag. The piece is called: Music For Millionaires. I think it starts on page 55.

Do a search for: "Music for Millionaires Mirko Paneyko"

Thanks,
Joe Y
Attached Images
File Type: jpg 1_5bcc7891534adcd794b48d0c47d0bd1b.jpg (52.1 KB, 303 views)
File Type: jpg 89014.jpg (269.1 KB, 294 views)
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Old 2nd January 2018, 07:09 AM   #25
jazbo8 is offline jazbo8
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Here is the article.
Attached Files
File Type: pdf 1957 - Music for Millionaires (Kuttner).pdf (942.8 KB, 160 views)
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Old 2nd January 2018, 12:34 PM   #26
banat is offline banat  Serbia
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MP OTL amp and J.Futterman amp are topologically very similar, but main difference between two OTL amps is that by MP amp phase inverter cathode resistor (R7=33K) is grounded , where by Futterman amp that cathode resistor is purposely connected to output line of the amp ,
IMHO those vintage MP OTL amps deserve and need very careful check of all active and passive elements,correct OPS biasing ,...
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Old 2nd January 2018, 07:33 PM   #27
smoking-amp is offline smoking-amp  United States
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Quote:
Don't discount this design too quickly.
Sorry if I sounded too harsh. I'm sure the MPs CAN indeed sound excellent, just saying that's not the way I would (these days) design such an amplifier.

Once one resigns themselves to the use of massive N Fdbk, as pretty much all OTLs do in the end, to get lowered output Z, then one no longer needs to fixate on triode outputs. As Futterman realized in his H3 design, a big honkin' pentode is just fine. 6HJ5, then 6LF6, the bigger the better. Actually a Mosfet would work best if it only looked more like a tube.

I would be more oriented toward reliability, ease of servicing, and minimized heat and weight these days. (switching power supplies for sure)

-----------

Quote:
MP OTL amp and J.Futterman amp are topologically very similar, but main difference between two OTL amps is that by MP amp phase inverter cathode resistor (R7=33K) is grounded , where by Futterman amp that cathode resistor is purposely connected to output line of the amp ,
Futterman H1 schematic for comparison:
http://www.audiodesignguide.com/otl/12b4.gif

This difference IS significant. Futterman used an (anti) bootstrap for the bottom output tube's drive ( 6S4 splitter cathode), to effectively "equalize" the grounded cathode mode drives for the outputs. (which requires either attenuation of the bottom grid signal for a totem pole design, or boosting of the top tube grid signal via (positive) bootstrapping.)

While the MP design does not do this. (it has equal splitter outputs) Which overdrives the bottom output tubes in a totem pole configuration. Bruce Rozenblit used the same configuration for his OTL design. That got criticized by John Broskie at TubeCad. It makes for inefficient operation of the output tubes, and higher distortion, 2nd harmonic distortion mainly. A SET like characteristic.

This probably does appeal to some listeners, just like SET designs do. However, the output tubes run hotter since they are fighting each other some. Output Z will not be as low either. My feeling is that the output stage (of an OTL) is not the place to meddle for such effects.

If massive N Fdbk is a religious problem however, then it'll take 600 12B4s for an 8 Ohm OTL with quality triode sound. (Or a triode emulation type design with some big pentode outputs. That's NOT triode strapped output pentodes by the way, Mosfets would work just fine too )

Last edited by smoking-amp; 2nd January 2018 at 08:02 PM.
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Old 2nd January 2018, 09:51 PM   #28
kasanay is offline kasanay  United States
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Quote:
Originally Posted by jazbo8 View Post
Here is the article.
Thank you for posting that for me.
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Old 3rd January 2018, 05:59 AM   #29
PRR is offline PRR  United States
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I would not expect to need women with shopping-carts of tubes for hourly repairs. This is far smaller than EINIAC (20,000 vacuum tubes). I road-tripped tube power amps with more tubes total than this, and didn't carry spares, and no failed gigs. I salvaged a broadcast console with more tubes than this, and I do not recall tube-troubles in commissioning or operation.

This rig has a small advantage in that one or two 12B4s could fail and hardly be missed. (In a console, any tube failure was a dead channel or output; mitigated in that each stage was plug-out and also originally patchable.)

The tube density is frightful, yes. I commend the book Hot Air Rises and Heat Sinks, which discusses why many heat problems confound average persons. In particular, putting hot-spots together may *improve* cooling; or at least not get you in trouble. The convective forces and air-rate increase. His example was a rack of gear. One unit ran warm. Two units ran warmer. 13 units stacked ran *cooler* than 3 on average, with no over-temps.

I do not think "massive" NFB, not like a Williamson or transistor amp. I make it about 20dB in lower audio band and less above ~~1KHz.

Pentode power will need floating G2 supply, a complication the designer may have disliked.

Bootstrapping the driver to "equalize" the drives may be another complication avoided. Work out the gains. The "plate loaded" side has very low gain. The "cathode loaded" side has lower gain, but maybe not enough to hurt, or justify all possible "improvements". I'll accept that the designer spent a lot more time on this than I ever will, and his path was best for him. Apparently this was not a one-off or direct-to-dumpster product.

Bigger tubes mean less tubes but they cost more each. At some point in the designer's thinking, he studies his tube-shop price list. While the customers are rich, their pockets are not bottomless, and you want to give them the "most" for their money while not going broke. The wiring-costs of 30 small sockets vs 8 large sockets do suggest fewer bigger tubes, but you may have low-pay workers or just think socket-wiring is relaxing evening work. Certainly the wiring of 30 sockets looms small compared to the hundreds of hours developing and evaluation, and time spent turning potential customers into actual buyers.

An amazing piece of kit. Thanks for sharing.
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Old 3rd January 2018, 06:23 AM   #30
TonyTecson is offline TonyTecson  Philippines
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PRR, what is your take on the Tim Mellows OTL? anyone?
http://www.mellowacoustics.com/artic..._amplifier.pdf
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