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Old 17th April 2012, 06:44 AM   #1
kof is offline kof  Thailand
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Default High bright 12AX7 solid state drive

High bright 12AX7 solid state drive From THAILAND

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Old 18th April 2012, 01:36 AM   #2
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Since this circuit does not use Mu to any advantage:
I'd think a triode with higher Gm, like 6DJ8 or 6922
would give a superior result...

Whats with Baxandall pairs at Q6 and Q7? Baxandall
pairs in VAS stage will invite local parasitic oscillations...
You are relying on compensations C7 and C8 to low
pass filter these local oscillations after the fact???

Q14 and Q20 need resistance from base to base.
Minority carriers can't bleed off through diodes
D6 D7, so those transistor shutoffs will be ugly
and slow...

470 seems a bit much for an emitter resistor.
What load is this driving?

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Old 19th April 2012, 08:09 AM   #3
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I am fascinated by tube/transistor hybrids and this one looks good at first glance, but some question came up.

The device info for D6,D7, Q14 and Q15 is not readable.

With the +115V power rails, this amp is capable of putting out about 800W into 8 ohm. Those output devices will not live long. You will need to add a whole lot more of them in parallel.

Another thing: why is there a 1 Henry choke on the output?

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Old 19th April 2012, 09:40 AM   #4
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( yes sir ) , , that's why , , must consult , and correct , with ? ,

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Old 19th April 2012, 11:13 AM   #5
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Quote:
Originally Posted by ingenieus View Post
With the +115V power rails, this amp is capable of putting out about 800W into 8 ohm. Those output devices will not live long. You will need to add a whole lot more of them in parallel.

Another thing: why is there a 1 Henry choke on the output?
I don't see any output devices; this looks like a driver stage only. I'm assuming the output stage (or just output transistors in this case) would be off board, and perhaps running from lower voltage rails.

I'm hoping he mean't 1uH.
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Old 19th April 2012, 12:33 PM   #6
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output stage

2SC5200 - 2SA1943

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Old 19th April 2012, 01:09 PM   #7
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Nowhere near enough devices shown there for +/-115V rails. Eight or more pairs of MJ21193/94 would be needed for that.
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Old 19th April 2012, 02:23 PM   #8
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I built a power amp similar to this with a 6922 at the input and much lower supply voltages. Circuitry was different.
I had to turn on the tube heater first and then switch on the low voltage supplies after some time. I did think of introducing a relay in between to avoid this but then time delayed power switch on seemed better . Will have to find the board to see what I did eventually. Can't recall what the sound was like. Maybe I should try turning it on again.
It's been a long time !
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Old 19th April 2012, 02:47 PM   #9
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At these voltages, your looking at ATLEAST 15-20 pairs of output transistors.

I believe PA amps running these kinda voltages have up to 50-100 pairs of output transistors, depending on make and model.
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Old 19th April 2012, 04:43 PM   #10
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thank every an advice
the royal utensils is like [ model ] at I [ hair ] has tested to upward that get test at DC 90+/- 1200va that output 4 a pair and get test already but still stick a problem at must have the circuit delays clear dot is tube

and now -ing wait for at the some part will in order to , do ,
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