211 PP - Beastzilla

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jack
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#1 211 PP - Beastzilla

Post by jack »

Not sure why I'm doing this.... however....

I have 2 x 211 PP output transformers designed by Andy Grove and built by Morite, screened to chassis - 15K primary, 6R secondary... Whilst these may be a bargain, the total cost of a decent build will be large and I don't want to make too many mistakes along the way...

Sowter charge £500 EACH for similar OPTs alone... :shock:

I am currently acquiring hardware - the tubes, hopefully, will be with me in a few weeks and I've ordered the Jumbo UXs as well.

Whatever happens, I'll build one channel first...

Starting point is Max's thread - he has the other pair of these beasts and I've mailed him for some info.

This will be a slow-burner - realistically, I don't expect anything working before Christmas as I have 10s of other projects on the go as well...

I'm completely open to suggestions..
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Neal
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#2

Post by Neal »

Andy Grove sent me a driver cct when Max and I where thinking of building the 211 PP, Max may still may have it but I'll have a look to see if I can locate it...it was just an idea of his suggested as a starting point so no actual component values but may give you some ideas Nick...
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#3

Post by jack »

Max's thread is at http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=1461

A few years ago now.

Much to learn, there is.
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Neal
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#4

Post by Neal »

AG idea for the driver stage:

Image

Phase splitter needed ahead of this or go balanced...
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#5

Post by jack »

That's pretty much what Max was doing:

Image

Another approach: http://www.labjc.com/?p=21
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Paul Barker
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#6

Post by Paul Barker »

nickds1 wrote: Another approach: http://www.labjc.com/?p=21
The CCS loaded Pentode is different.

As long as that is linear and all the necessary voltage gain is there, which it has to be, the rest of the amp is nice: White cathode follower driver.

all the three designs are balanced all the way.

Not the only method.

Some people like to go single ended some or most of the way. Sukuma and Stephie to name but two.
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#7

Post by Mike H »

nickds1 wrote:That's pretty much what Max was doing:
Yes scrap C1 in the preceding schematic. (IMHO.)
 
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#8

Post by pre65 »

Right, what I was going to ask was

a) are you going for monoblocks, or one amp and one PSU ?

I would think everything in one case would be too heavy.

b) What HT are you aiming for, and have you a mains transformer in mind ?
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#9

Post by IslandPink »

If you only want A1 then there's E55L pentode as driver ... I know James D likes this option :D
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#10

Post by jack »

2 x mono-blocks + 2 x PSUs.

Mono-blocks & PSUs to be mirror images.

Weight is a consideration - I got the 4 Jumbo sockets today - lovely, but they alone weigh 1.5kg, The OPTs are 6kg each. Each block is likely to weigh 15kg or so, so a single amp would be nuts.

I will use a sub-chassis + a top plate, probably profile-cut from stainless steel with a matt finish - I am a big fan of simple, clean lines. Thinking either dark wood plinth (cherry?) - or beech - can't decide - lots of time to think about such trivia :)

No mains transformer in mind - HT anywhere from 900V up at the moment...

I bought a couple of 100THs yesterday as well. NOS. Just for fun,
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Neal
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#11

Post by Neal »

Mike H wrote:
nickds1 wrote:That's pretty much what Max was doing:
Yes scrap C1 in the preceding schematic. (IMHO.)
Heretic! :D
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#12

Post by pre65 »

I like the AnTek range of toroidal transformers.

http://www.antekinc.com/transformers/

I don't know what rectifiers you hope to use, but a hybrid bridge with two 6Ds22 damper diodes has a lot to recommend, and the AnTeks I use have the required 6.3v windings.

360-0-360 gives me 950v HT in cap input mode.

http://www.antekinc.com/as-4t360-400va- ... ansformer/

They do higher voltage ones as well. :)
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#13

Post by Mike H »

Neal wrote:
Mike H wrote:
nickds1 wrote:That's pretty much what Max was doing:
Yes scrap C1 in the preceding schematic. (IMHO.)
Heretic! :D
Image
 
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#14

Post by slowmotion »

I will be following this thread with great interest.

I would keep C1, by the way.

:)
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Mike H
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#15

Post by Mike H »

Without it you get cathode coupling between the two triodes, thus helping to cancel any level imbalance between the two inputs. Nit picking I know but, why not, if it's available (?)

EDIT: even better cathode coupling with a CCS instead of a resistor. :D
 
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