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Old 15th December 2010, 05:32 PM   #1
M Gregg is offline M Gregg  United Kingdom
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Smile Any thoughts on this circuit?

Just for interest.

I came across this circuit has anyone ever used it?

The reason I ask is I am looking at a possible Miniwatt using inverter and 3 tubes 2x EL34 1x ECC81 just for fun!



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M. Gregg
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Old 15th December 2010, 05:35 PM   #2
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Looks like the most basic tube amp. You find similar circuits/examples in texts and 1950's tube manuals.

paul
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Old 15th December 2010, 06:09 PM   #3
el156 is offline el156  Portugal
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The 470K resistor shoudnt be conected to the other end of the 10K resistor?
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Old 15th December 2010, 06:20 PM   #4
M Gregg is offline M Gregg  United Kingdom
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This is the circuit as shown.

Spec is supposed to be 3.5 W and it was used with Voight speakers.

So 3.5w per channel.

Here is the idea - link

http://www.miniwatt.com.hk/


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M. Gregg
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Old 15th December 2010, 06:33 PM   #5
20to20 is offline 20to20  United States
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Quote:
Originally Posted by M Gregg View Post
This is the circuit as shown.

Spec is supposed to be 3.5 W and it was used with Voight speakers.

So 3.5w per channel.

Here is the idea - link

MiniWatt Tube Amplifier


Regards
M. Gregg
Pretty high distortion rating w/o feedback.
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Old 15th December 2010, 06:47 PM   #6
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I agree that it resembles a lot of simple circuits, but I must be missing something...we've got signal in, ground, but where's the B+ connection?
Something overlooked in the drafting dept?
John
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Old 15th December 2010, 06:51 PM   #7
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by VictoriaGuy View Post
I agree that it resembles a lot of simple circuits, but I must be missing something...we've got signal in, ground, but where's the B+ connection?
Something overlooked in the drafting dept?
John
Sorry,

The B+ is top of the Op Tx (5K) 225V 60mA.

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M. Gregg
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Old 15th December 2010, 07:05 PM   #8
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What's going on? The schematic you posted is of an ECC81 driving a triode strapped EL34. The Miniwatt amp you linked to (as inspiration?) is a 12AX7 driving an EL84, and it's definitely not triode strapped or it wouldn't make 3.5W. What are you trying to achieve?
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Old 15th December 2010, 07:22 PM   #9
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by leadbelly View Post
What's going on? The schematic you posted is of an ECC81 driving a triode strapped EL34. The Miniwatt amp you linked to (as inspiration?) is a 12AX7 driving an EL84, and it's definitely not triode strapped or it wouldn't make 3.5W. What are you trying to achieve?
The idea is to get an "improved" miniwatt. Using triode EL34 to get the same output power.
Or switchable pentode to get more power! If you have any improvements please post!
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Old 15th December 2010, 07:31 PM   #10
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Quote:
Originally Posted by M Gregg View Post
The idea is to get an "improved" miniwatt. Using triode EL34 to get the same output power.
Or switchable pentode to get more power! If you have any improvements please post!
It's hard to talk in generalities since the devil is in the details, but one aspect is that a pentode EL84 is so much easier to drive than a trioded EL34 that you might be very well be taking a step backwards rather than forwards.

There are SO many choices out there. Have a look at the Simple SE for one.
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