Schematic: Audio Innovations, The first audio amplifier

maartentje · 20th February 2008, 07:54 PM

Hai there,

Is there anybody with a schematic of the Audio innovations - The first audio amplifier? Or service manual?

*12watts pure class A PP
*Nfb
*2A3 tubes

Maarten

Psychobiker · 20th February 2008, 09:33 PM

AFAIK there can't be Class A p-p

gingertube · 20th February 2008, 11:07 PM

Psychobiker,
There certainly can be full Class A Push Pull.

It simply means that neither tube ever runs into cutoff. As soon as one tube cuts off then thats Class AB.

When one tube cuts off then the effective load seen by the other tube changes from Raa/2 to Raa/4 and it is handling this transistion from class A into Class B that is the one of the major "bug-bears" of Class AB design. Ultralinear Outputs seem to handle this transistion a little better than pentode mode.

There are actually a lot of pure Class A Push Pull Amps out there, particularly with Triode Output.

Then there are also quite a few that claim to be pure Class A but aren't.
In the Guitar Amp world the classic example is the VOX AC30 which was claimed to be full Class A but is'nt.

One of the measures of a good Class AB Amp is actually how much Class A power it can deliver before the transistion into Class B occurs - generally the more the better. This will depend upon the idle current in the output tubes. With higher idle current you can swinf more signal current before a tube runs into cut off, that is more Class A power.

Take that to its obvious conclusion and you see that pure Class A push pull should be much better than Class AB.

Cheers,
Ian

Maarten,

I don't know if this is the amp you were looking for. Its a parallel 2A3 Push Pull Class A

http://diyparadiso.com/mod-ppp2a31.htm

Psychobiker · 21st February 2008, 08:32 AM

Thanks for that

maartentje · 23rd February 2008, 12:01 AM

Hi there,

thanks for response. But thats not the orginal schematic. The orginal audio innovation use only two 2a3's per channel.

Somebody else maybe with schematic?

Best regards
Maarten

maartentje · 16th April 2008, 10:25 AM

Nobody?

ErikdeBest · 17th April 2008, 10:57 AM

I am curious as how the amplifier extracts 12W from two 2A3 valves...

Erik

Geek · 17th April 2008, 11:06 AM

Hi Erik,

Quote:

Originally posted by ErikdeBest
I am curious as how the amplifier extracts 12W from two 2A3 valves...

Erik

Easy

http://www.straubamps.com/tt.html

Quote:

"....allows us to drive them at full Class A Push/Pull power levels...."

Cheers!

ben goh · 17th April 2008, 11:19 AM

Hi

Try this

http://www.drtube.com/audioamp.htm

revintage · 17th April 2008, 11:36 AM

It is possible to squeeze out 12W in class-AB. But not in Class-A if you want to stay below Pamax.

To call the Straub 12W class-A is as wrong as to call the famous Vox AC-30 30W class-A.

But I must say the Straub concept looks nice!

20th February 2008, 07:54 PM	#1
maartentje diyAudio Member Join Date: Jun 2002 Location: USA, FL	Schematic: Audio Innovations, The first audio amplifier Hai there, Is there anybody with a schematic of the Audio innovations - The first audio amplifier? Or service manual? 12watts pure class A PP Nfb *2A3 tubes Maarten

17th April 2008, 10:57 AM	#7
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	I am curious as how the amplifier extracts 12W from two 2A3 valves... Erik __________________ my surname is indeed 'de Best': neither misspelling nor snobbism! Ask SY!

17th April 2008, 11:36 AM	#10
revintage diyAudio Member Join Date: May 2007 Location: Eskilstuna, Sweden	It is possible to squeeze out 12W in class-AB. But not in Class-A if you want to stay below Pamax. To call the Straub 12W class-A is as wrong as to call the famous Vox AC-30 30W class-A. But I must say the Straub concept looks nice! __________________ Brgds Lars

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20th February 2008, 09:33 PM	#2
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Montréal QC	AFAIK there can't be Class A p-p

20th February 2008, 11:07 PM	#3
gingertube diyAudio Member Join Date: Oct 2004	Psychobiker, There certainly can be full Class A Push Pull. It simply means that neither tube ever runs into cutoff. As soon as one tube cuts off then thats Class AB. When one tube cuts off then the effective load seen by the other tube changes from Raa/2 to Raa/4 and it is handling this transistion from class A into Class B that is the one of the major "bug-bears" of Class AB design. Ultralinear Outputs seem to handle this transistion a little better than pentode mode. There are actually a lot of pure Class A Push Pull Amps out there, particularly with Triode Output. Then there are also quite a few that claim to be pure Class A but aren't. In the Guitar Amp world the classic example is the VOX AC30 which was claimed to be full Class A but is'nt. One of the measures of a good Class AB Amp is actually how much Class A power it can deliver before the transistion into Class B occurs - generally the more the better. This will depend upon the idle current in the output tubes. With higher idle current you can swinf more signal current before a tube runs into cut off, that is more Class A power. Take that to its obvious conclusion and you see that pure Class A push pull should be much better than Class AB. Cheers, Ian Maarten, I don't know if this is the amp you were looking for. Its a parallel 2A3 Push Pull Class A http://diyparadiso.com/mod-ppp2a31.htm

21st February 2008, 08:32 AM	#4
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Montréal QC	Thanks for that

23rd February 2008, 12:01 AM	#5
maartentje diyAudio Member Join Date: Jun 2002 Location: USA, FL	Hi there, thanks for response. But thats not the orginal schematic. The orginal audio innovation use only two 2a3's per channel. Somebody else maybe with schematic? Best regards Maarten

16th April 2008, 10:25 AM	#6
maartentje diyAudio Member Join Date: Jun 2002 Location: USA, FL	Nobody?

17th April 2008, 11:19 AM	#9
ben goh diyAudio Member Join Date: Jun 2001 Location: nil	Hi Try this http://www.drtube.com/audioamp.htm

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