PICS: "Optimos" 140W Monoblock Amps! - diyAudio
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Old 10th November 2002, 03:26 PM   #1
Rarkov is offline Rarkov  England
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Default PICS: "Optimos" 140W Monoblock Amps!

Finally Pics of my so called "Optimos" amps. Almost finished.
Still to do is the aluminium cover, Blue LED potential divider circuit and an aluminium plate between the PSU and the amp...

Hope you like them - they sound great!

P.S. Sorry about the long wait! I wanted to keep the image quality.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

If you can't see those pics use link: http://www.diyaudio.com/forums/showt...2074#post92074

Thanks,

Gaz
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Old 10th November 2002, 03:59 PM   #2
BrianGT is offline BrianGT  United States
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Looks great! Nice clean, compact chassis design. What are you planning on putting on the top and sides?

How big are the pcbs?

Great job!

--
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Old 10th November 2002, 05:05 PM   #3
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Wow, nice!

It looks like you rolled your own boards?

Did you add any features (output protection, etc) to your boards or are they stock?

Where did you get the heat sinks?
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Old 10th November 2002, 06:11 PM   #4
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Looks nice.

Have you figured out if is the OptiMOS you've built? We've had
some discussion about this previously, and I got the impression
you weren't sure about this then. The OptiMOS is one of the
designs I am considering, so it interesting to hear opinions about
it.

Do you really need those large heatsinks? Judging from the
photos it should be the standard 120W version, so I guess
you could manage with quite smaller ones. Not that it hurts
with overkill on the heatsinks, of course. I also see that you
have quite long leads to the output transistors. I would have
preferred a different board layout to avoid that, but if the amps
work well it probably doesn't matter in practice.

Edit: Just saw that it says 140W in the title. I suppose you
just increased the supply voltages a little bit and kept the
number of output devices (if it is the OptiMOS, that is)?
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Old 10th November 2002, 08:35 PM   #5
Rarkov is offline Rarkov  England
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Hi,
I had just written a reply when my PC crashed so here goes again!

BrianGT:
I am using Aluminium Sheeting to cover the Top, back and front with a 3mm blue LED. The PCBs are 125x175mm, but the actual circuit on the board is slightly smaller... more like 90x170mm.

jgwinner:
The boards are by my own fair hands! They are by a system called Press 'n' Peel which I highly recommend avoiding!!! Much better to get a UV light and photo-sensetive PCB. The heatsinks were £10 each from Jakeh on this forum. He is very approachable an are stunning quality! There are no extras on the circuit.

Christer:
I do not believe it to be the OptiMOS circuit. The schematic is slightly different, but the OptiMOS is certainly the closest version to the one I built. It says in the book that it is rated at 140W into 8Ohms and 200W into 4 Ohms when the Power supply is at +- 55V. Since my power supply is at +- 63.1V it will be slightly more. The book says 200W into 8Ohms at +- 68V, so you can do the maths!

The sound is fantastic, but until I build a preamp, I cannot test it with anything but a very dodgy CD player! As I said above, the heatsinks were cheap and allowed me to fit everything in. I'm really happy with the way it's all worked out!

Thanks for the comments, and keep them coming! If you want pics of anything in particular, just ask!

Thanks again,
Gaz
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Old 10th November 2002, 09:52 PM   #6
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Quote:
Originally posted by Rarkov
I do not believe it to be the OptiMOS circuit. The schematic is slightly different, but the OptiMOS is certainly the closest version to the one I built. It says in the book that it is rated at 140W into 8Ohms and 200W into 4 Ohms when the Power supply is at +- 55V. Since my power supply is at +- 63.1V it will be slightly more. The book says 200W into 8Ohms at +- 68V, so you can do the maths!
OK, then I see the reason for the big heatsinks.

Any chance you could post the schematic? It would be interesting
to compare it to the OptiMOS and the designs in Sloanes
power amp book.
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Old 11th November 2002, 07:32 AM   #7
Rarkov is offline Rarkov  England
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Hiya,

Just very quickly, here is the:

OptiMOS Design PDF

And here is my amp's schematic:

EDIT: schematic removed by moderator. This schematic came out of a book and is therefore protected by copyright. Reproduction of said image requires the express permission of Randy Slone.

Hope that helps...
Gaz
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Old 11th November 2002, 07:58 AM   #8
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Press n peel

I have used it a few times and it works fairly well but...
It can be a bit tricky. It does not work well at all for large masking areas and wise traces, I always have to fill those in using nail polish. All the problems I ever had with it were in the peel part. If you are peeling and a trace dosen't stick, stop peeling and iron some more. Never peel it all the way off unless you are happy with the result. Getting it to work right can be difficult but is not impossible. The instuctions are not kidding about a band of copper around the project edge, this holds it down so you can be sure that you get all the traces down.

If I am not using chips and the circuit is small (like power supplies) I usually make a few drawings, then sit down with the board and use an engraving bit to seperate the traces. Not the sexiest but much faster than drawing it up and etching it.

Also congrats on the amp! Looks great
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Old 11th November 2002, 08:10 AM   #9
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Thanks Rarkov,

I would definitely say it is the OptiMOS. As far as I can see it
is exactly the same topology with just a few component values
differing slightly. I suppose the version on the web page is
newer and Sloane has done some tweaking on the exact values
of some resistors.

As I said, I might choose to build the OptiMOS myself, so its
good to hear your positive report on how it sounds. (On the
other hand, considering the weather right now I should perhaps
go for a huge class-A amp instead ).
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Old 11th November 2002, 11:09 AM   #10
Rarkov is offline Rarkov  England
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Hi,
Sorry...That's my fault...Didn't mean to step on anyone's toes!

Therefore, to see the image, you must buy The Audiophile Source Book (Which I highly recommend [grovel grovel!]). You can gt it from Amazon - and is quite cheap. Loads of interesting circuits - not just amps. but protection, preamps, crossovers, equalisers, balanced-unbal convertors etc etc.

Please forgive me!

Gaz
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