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Cheap as Chips OPA1688 Low-THD Muscle Amp
Cheap as Chips OPA1688 Low-THD Muscle Amp
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Old 15th July 2018, 11:03 PM   #21
AKSA is offline AKSA  Australia
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X,

Extraordinary performance! Beautiful layout (congratulations JP!) and absolutely top class commercial work. I hope lots of people looking for a ultra-low THD HPA build this and that the pcb can be available from the DIY shop!

I think we can be very grateful for X and JP for their brilliant, restive work for our benefit. I am very grateful for X because he builds a lot of my prototype circuits at least 20 times quicker than I do it myself...... the ALPHA has been our work together, and the layout was brilliantly done by JP64.

I'm hoping more and more of the ALPHAs are built. This is a superb 20W Class A amplifier based on a combination of the AKSA/Lender preamp and the Aleph J active current source from Nelson Pass. It is a very good amplifier, one of the best - and thanks to X and JP64 who brought it into the world.

Cheers,

Hugh
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Old 16th July 2018, 12:21 AM   #22
xrk971 is offline xrk971  United States
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Cheap as Chips OPA1688 Low-THD Muscle Amp
Thanks for the kind words, Hugh. It’s been a privilege gettibg to build your amp designs! Working with you and JPS64 is a blast and I hope we keep making new cool amps!
Cheers,
X
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Old 16th July 2018, 11:10 AM   #23
suzyj is offline suzyj  Australia
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Looks pretty cool - kinda begging to be bridged though.
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Old 16th July 2018, 02:15 PM   #24
xrk971 is offline xrk971  United States
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Cheap as Chips OPA1688 Low-THD Muscle Amp
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Originally Posted by suzyj View Post
Looks pretty cool - kinda begging to be bridged though.
If I can get 2.5w normally, bridging gets 6.25w?

Thatís a lot of opamps

But tiny WSON8 packages donít take much room itís the ancillary low ESR caps that surrounds them that is the pain.
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Old 16th July 2018, 02:27 PM   #25
Sodacose is offline Sodacose  United States
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This looks like a very cool amp to build up and keep around as a reference (always been curious about the Self amp I mentioned earlier).

Are you planning to make the layout/files available for other DIYers?
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Old 16th July 2018, 02:56 PM   #26
xrk971 is offline xrk971  United States
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Cheap as Chips OPA1688 Low-THD Muscle Amp
If there is enough interest JPS64 and will probably do a group buy, but in general, JP does not release the layout files. This board has small WSON8 SMT parts (with underside thermal pad and no legs) that are not trivial to solder without proper equipment like a hot air gun. I may have to offer a prepopulated SMT board to reduce the level of difficulty on this amp.

Click the image to open in full size.
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Old 16th July 2018, 03:21 PM   #27
Sodacose is offline Sodacose  United States
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Ah ok, just through your Etsy then?

Also, any details on the power supply in the new renders?
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Old 16th July 2018, 04:18 PM   #28
Tazzz is offline Tazzz
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I made a similar amp earlier this year (when I realised the M2Tech dac I bought cheaply on impulse could not drive my headphones)

I used 2xOPA2172 per channel i.e four opamps per channel (however with all contributing output current) I also added some low IDSS 2sk170 for biasing and included regulation (simple Zener followers) +/- 5V

The measurement shows 1Vrms into 50ohm.
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Old 16th July 2018, 06:05 PM   #29
lineup is offline lineup  Sweden
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OPA172, OPA2172 is something new for me.
Thank you!
Can deliver at least 70mA, as I can see it.
An interesting opamp.
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Old 16th July 2018, 07:10 PM   #30
xrk971 is offline xrk971  United States
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Cheap as Chips OPA1688 Low-THD Muscle Amp
Quote:
Originally Posted by Tazzz View Post
I made a similar amp earlier this year (when I realised the M2Tech dac I bought cheaply on impulse could not drive my headphones)

I used 2xOPA2172 per channel i.e four opamps per channel (however with all contributing output current) I also added some low IDSS 2sk170 for biasing and included regulation (simple Zener followers) +/- 5V

The measurement shows 1Vrms into 50ohm.
Nice design! Did you use the 2SK170ís to bias the rails into Class A?
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