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Old 11th September 2010, 02:06 PM   #111
chrish is offline chrish  Australia
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I hope that I can include these amps as a "Tubelab" amp. They are a pair of monoblocks using Tubelab's universal driver schematic. Tubelab helped with this design on the 'tubes' forum.

The amp is two DC coupled 6SN7 differential stages with constant current sinks driving a pair of MOSFET source followers driving push pull 6L6s through Tamura 6.6K output transformers. Power supply is 'Maida' style regulator 400 volts. +75 and -105 volt supplies from separate transformers with VR tubes (for fun).

Chassis were picked up in Singapore some time ago. Very thick aluminium top plate used as heat sink for MOSFETs and CCS chips.

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Old 18th September 2010, 04:50 PM   #112
w5jag is offline w5jag  United States
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Those monoblocks look fantastic. What kind of OPT's are you using?

Win W5JAG
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Old 20th September 2010, 12:49 AM   #113
chrish is offline chrish  Australia
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Thanks, they are Tamura F-684, 6.6K 30Watt.
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Old 20th September 2010, 05:52 PM   #114
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Chrish,

One question: are the mosfet of the power drive attached directly on the chassis ? Aren't you afraid to get the B+ on the cabinet ?

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Davide
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Old 21st September 2010, 09:04 AM   #115
chrish is offline chrish  Australia
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The top plate of the chassis is about 5mm thick aluminium so is good for a heatsink. The MOSFETs are insulated with an insulator. There is a regulated power supply with a floating LM317 regulator and MOSFET pass device. Both are attached to the large heatsink at the rear of the chassis with insulators. If B+ touches the chassis it is grounded and should trip the earth leak protection breaker at the fuse box and also the fuse in the IEC connector on the chassis.
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Old 25th December 2010, 06:05 PM   #116
Structo is offline Structo  United States
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Man those are some great looking amps guys!

Can anyone tell me where to find the motor run caps that are high enough voltage to use?
I think the highest rated round one I saw was 370v.

Also, where do you get those nice transformer housings?

I love the exotic wood used on some of those enclosures.

That guy in Lebanon is only about 40 minutes south from me.
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Old 27th December 2010, 12:58 AM   #117
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Quote:
Can anyone tell me where to find the motor run caps that are high enough voltage to use?
I think the highest rated round one I saw was 370v.
370 VAC is fine for a Simple SE. Thats what's in mine.
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Old 27th December 2010, 07:30 PM   #118
Structo is offline Structo  United States
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The secondary voltage is what I am having trouble figuring out for the SSE.

I see an Allied 6K7VG is recommended.
It has 750 VCT.
I get confused on transformer ratings because some companies show what the loaded voltage is while others show unloaded voltages.
So is this Allied PT a 375v PT?

So with a 5AR4 I get (375v * 1.31 = 491) - 17v = 474v on the output of the 5AR4.

Is that correct?

The Allied PT is only 5 amps on the 6.3vac.

I figure if I run EL34's I will need at least a 6 amp heater winding.

The Hammond 274BX has a 6 amp heater winding but it doesn't seem to get very good reviews.

The Edcor XPWR035 PT is (370-0-370) at 200mA center tapped, 6.3V (3.15-0-3.15) at 5A center tapped and 5V at 2A

So it is only 5 amps again on the 6.3 vac.

If I use 6L6GC tubes then 5 amps is enough, but I want to be able to run EL34's as well.

Funny thing is that when I look up the specs for the Allied transformer up pops a Hammond data sheet.
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Old 27th December 2010, 07:32 PM   #119
Structo is offline Structo  United States
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I like the fact that Hammond has started making their PT primary with the choice of 115 or 125vac.

Since the higher wall voltages are common you can use the 125v primary to lower your heater voltages.

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Old 1st January 2011, 01:31 AM   #120
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Hello all and Happy New Year, I'm ringing in the New Year listening to the Beatles my SE. Needless to say, it sounds stupendous! The build was finished late summer but I didn't have a good camera at that time so my entry was delayed. This is my humble contribution to the gallery. The case is recycled from a broken sony DVD changer. The paint is Grey Hammertone spray. Thanks to all of the generous experts on this forum who provide timely support.
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