GM70 Monoblocks’

What people are working on at the moment
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Paul Barker
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#46 Re: GM70 Monoblocks’

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The news update is I miscounted Anode chokes. There are 3 per channel. No need to worry, I think I have enough.
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Paul Barker
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#47 Re: GM70 Monoblocks’

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Homemade kathode caps

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"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Paul Barker
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#48 Re: GM70 Monoblocks’

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I found a wooden thing in £ shop yesterday. My caps haven't arrived. But it appears I shall have to put as many as I can fit standing tall on top, because they arent the best thing to put inside as their volume is great and the amp case isn’t spacious, I have anther power choke two filament transformers and 6 anode chokes power resistors and a whole load of point to point wiring to fit beneath.

Valve bases on order, capacitors on order, I think I have enough resistors, the white coffins take up space. The el84 resistors are ok to mount against side thick aluminium side panel. Trying to make the new stainless steel when it arives to not look like a pin cushion. Thinking of Arulditing the ceramic bases up from beneath.

Havent thought yet how to stand capacitors neatly. But just came to me. Araldite.

When I was a young boy my friends Dad an action man in the war, was building a cannoo with araldite. He said “this is a good glue Paul, they build bridges with it.”

When Delta forse failed to rescue US hostages from Iran, the SAS were asked if they were involved. To which the short reply came “if we had been involved it wouldn’t have failed”. Where is this going?

“If araldite was involved building that US bridge, it wouldn’t have failed.”

Anyway,
Plans patience period. Carefully planning avoids piss poor performance.
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Paul Barker
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#49 Re: GM70 Monoblocks’

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My careful planning has got me thinking about valves. We like to see them on top, we are like male peakocks.

Im not saing yay or nay. But when all caps are here, I shall see how the extrenally mounted components goes. Amaybe all the caps fit above, all remaining chokes and transformers fit above. Maybe there is room for valves. But they are the last thing to need it. Theu could live on the mezanine floor a neatly punched and grated hole above each valve. If there is space for said grated hole. There may not be, which wont matter at all. They can all sit upside down in the basement, so as removal of base panel to tube roll. A slow running fan powerd with the filaments wont be heard keeping the EL84’s alive longer. Its an EL84 thaing. They overheat.

I might letracett in Gold on the black blank front. EL84 Thaing.
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Paul Barker
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#50 Re: GM70 Monoblocks’

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Its not going to be easy. The tin caps arent whats going in. The plastic ones are smaller diameter.

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But it may be possible,
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Paul Barker
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#51 Re: GM70 Monoblocks’

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I’ll start new plans to go off board with the power supply. This chassis is too small and the power supply is so important I can’t compromise with it. Actually the rediculous thing is the 630v capable power supply Im using with the EL34 stand alone amplifier would become surplus when the GM70 amp is built. This power supply will fuel anything up to 630v b+.

So now I can focus on the signal section to drive the future GM70 signal section and the GM70 power supply.

This existing power supply stands a loan for everything else. I can only listen to one signal stage at a time.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Paul Barker
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#52 Re: GM70 Monoblocks’

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Right, so as this driver amplifier shall complement the GM70 putput stage I shall tailer a power supply for it, butit it cant fit this chassis without compromise and difficulties.

This is where you end up requiring a lot of floor space. Ive been here often. It would probably fit a likewise dimension chassis as the signal section. So would look neater if that were so.

Perhaps I’ll first check cheap chassis on Ebay.

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Close enough the signal chassis is 360 X 270 area. So they can fit one on top of another.
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Max N
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#53 Re: GM70 Monoblocks’

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If you haven’t ordered that Hammond chassis yet…

How many of the Nightingale chassis do you have?
You could order some blank aluminium plates cut to size to fit those? Plus maybe a few spares?
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rowuk
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#54 Re: GM70 Monoblocks’

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When I see builds like this, it reminds me of the late 1970s and early 1980s with those magnificent huge receivers from Kenwood, Pioneer and Sansui. They were not just big boxes, they were full.
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My opinion is that a "magnificent" build like this should also get a big, statement box so that the components have room to breathe, the coils, chokes and transformers have adequate space to spread their magnetism without interfering with one another. Maybe a tribute to the time when automobiles and hifi did not need to be practical.
Whenever I feel blue, I start breathing again.
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Paul Barker
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#55 Re: GM70 Monoblocks’

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I ordered it already. I have another Nightingale, not used but kept in manshed so would need a brush up with fine wire wool.

But the GM70 output monoblocks will need half width chassis, and probably same dimensions for power section. So I could buy 4 same chassis. The power supplies would have big power transformers and same size chokes and a pair of U19 each and a single 572b each.

I wont get it all on the bus.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Paul Barker
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#56 Re: GM70 Monoblocks’

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So now the Celestion A2 are the resident speakers downstairs. Amplified by Cambridge Audio CXA60.

This monoblock project has reached the next project on the list. I’ll have to voltage ratio check the Tribute SE ratio to see if I can get enough for 4 ohm speakers. Im not home atm, when I am I’ll check. If not suitable I’ll check the Sowter PP OPT’s 8k see if they have a 4 ohm tap.

So the monoblocks may evolve to PP.

Watch this space.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Paul Barker
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#57 Re: GM70 Monoblocks’

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Sadly the Sowters are 8 ohm. I doubt the Tributes will work out either.

So project probably off the radar again.
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Paul Barker
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#58 Re: GM70 Monoblocks’

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OK looking at Stephy’s diode cathode bias 845 amp which I looked at for the EL38 the 845 output valve resulted in substituted the GM70.

The limit of the output stage of my cirquit is 60mA. Hence 15 watts. Better than the 3.6 watts of the EL38. As Ive already found the diodes to use for the EL38 version may aswell use yhat project to volt amp and drive the output valve.

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Nick
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#59 Re: GM70 Monoblocks’

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Other than removing a power supply, what does the diode bias give you that a -ve grid supply wouldn't?
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Paul Barker
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#60 Re: GM70 Monoblocks’

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Looks the same if you dont have a longer view.. when I build the b+ capacitorless. Stephies power supply is capacitorless. Ive built it before, I can build it again. So building signal section with that in mind. I have two transformers just need matched heavy duty chokes. Can build monoblock capacitorless easily. Building two is difficult.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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