This is not just another gainclone

[SkinnyBoy]

Okay, I'm making a gainclone... I am still not totally sure what it is... but so what?? I have some LM3886ICs... now to find something to use as heatsinks.... lol... I think I have an old saucepan (pan/pot) somewhere.... hmm.... heatsink/case..

[planet10]

Originally posted by GringoAudio
Also where is the Thorsten circuit available?

Home of Thorsten's circuit



dave

[planet10]

Originally posted by GringoAudio
How does Quality Kit's LM1875-based kit compare to the Thorsten circuit?

If you built it as shipped it probably has too many parts... no doubt the more you can leave out the closer you'd get.

Does anyone have a take on whether you'd need to make any changes to pop in an 1875 into the Thor circuit?

dave

[analog_sa]

I've listened to an inverted gainclone for almost a year and there are some things everyone should know before their expectations get sky high.
The gainclone is as fussy about speakers as my SE valve amp. It plays great with my Lowhters and Tannoy Golds but is totally pathetic with my SF Signum. The SF is not a difficult load, having 1st order crossover and it can be very enjoyable even with a little 10W EL84 pp amp but with the gainclone it's vurtually unlistenable.
And to all who seriously compare gainclone to a good SE valve amp, please guys lets get down to earth.

cheers

peter

[SkinnyBoy]

What about the LM3886 amp IC?? or is that a no-no cos its got a mute circuit?? can I bridge to gainclones??

[planet10]

Peter,

If i get it correctly this is the as-built (i've added the optional 1,5k load resistor in blue)?

dave

[analog_sa]

Although i'm a different Peter, the 1.5k resistor is not doing much connected to ground. It should go -Vcc

[planet10]

Originally posted by analog_sa
Although i'm a different Peter, the 1.5k resistor is not doing much connected to ground. It should go -Vcc

Thanx... i've fixed my ID 10 T error...

dave

[vuki]

Dave: You can switch LM1875 instead of LM3875, but you'll need power xformer with lower sec. voltages (2x18V). Also, I had some difficulties with DC offset (it was 300-400mV) so you'll probably need adj. resistor +cap. at positive input to ground. But it sounds as good as LM3875.

[halojoy]

Originally posted by planet10
Home of Thorsten's circuit

http://home.attbi.com/~greggbaker/invertedLM3875.gif[/IMG]
dave

Thanks for link to the Forum, about thorsten's LM3875

Found this article mentioned in the Forum.

It is about parallelling LM3886, but could probably be valid for other chips.
Four LM3886 gives more than 200 Watt out!

Also Schematic

DC Electronics -App Note - PARALLEL-BRIDGED CONFIGURATION USING LM3886

This is Thorsten's comment on that article:

Hi,

This Parallel/Bridging principle applies to all Power Op-Amp's. In fact, a number of recent Jeff Rowland Amplifiers employ Bridged/Parallel LM3886.... They call "intelligent output transistors".

If I find Tripath Eval Modules too expensive for my Subamp for my new Speaker Project (18" Eminence Kilomax in URP Subwoofer mode, 15" Tannoy Coax, Supertweeter) I'll be using such a system as "fallback".

BTW, the parallel/bridging can be achieved without any further active components than the Amp Chip's themselves....

Ciao T

/halojoy - has not BRIDGED yet -Is not DEAF enough, to need so much power - but the day may come when he is 80 years old