Any thoughts on this circuit?

M Gregg · 05:50 PM

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!

Regards
M. Gregg

phaselag · 15th December 2010, 05:35 PM

Looks like the most basic tube amp. You find similar circuits/examples in texts and 1950's tube manuals.

paul

el156 · 15th December 2010, 06:09 PM

The 470K resistor shoudnt be conected to the other end of the 10K resistor?

M Gregg · 06:32 PM

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/

Regards
M. Gregg

20to20 · 15th December 2010, 06:33 PM

Quote:

Originally Posted by M Gregg

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.

VictoriaGuy · 15th December 2010, 06:47 PM

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

M Gregg · 15th December 2010, 06:51 PM

Quote:

Originally Posted by VictoriaGuy

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.

Regards
M. Gregg

leadbelly · 15th December 2010, 07:05 PM

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?

M Gregg · 07:25 PM

Quote:

Originally Posted by leadbelly

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!

leadbelly · 15th December 2010, 07:31 PM

Quote:

Originally Posted by M Gregg

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.

15th December 2010, 06:20 PM	#4
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	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/ Regards M. Gregg __________________ What is the sound of one hand clapping? Last edited by M Gregg; 15th December 2010 at 06:32 PM.

15th December 2010, 07:05 PM	#8
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	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? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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15th December 2010, 05:35 PM	#2
phaselag diyAudio Member Join Date: Nov 2010 Location: N.E. PA	Looks like the most basic tube amp. You find similar circuits/examples in texts and 1950's tube manuals. paul

15th December 2010, 06:09 PM	#3
el156 diyAudio Member Join Date: Apr 2010 Location: ALBUFEIRA ;PORTUGAL	The 470K resistor shoudnt be conected to the other end of the 10K resistor?

15th December 2010, 06:47 PM	#6
VictoriaGuy diyAudio Member Join Date: Dec 2008 Location: Victoria, BC	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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