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Old 16th October 2006, 11:15 AM   #21
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We would be paralleling two of our TPM-OPA549 (or TPM-LM3886)modules, each containing its own feedback loop and optional servo. It would really be a bridged/paralleled circuit.

So, each channel, if paralleled, would consist of a TXD module (symmetric driver), with the + output driving two paralleled TPM-OPA549 modules, and the - output driving two paralleled TPM-OPA549 modules, for a total of 4 chips per channel.

The kit will consist of just two per channel, but you can add as many in parallel as you like, and they will be available seperately. In fact, each TPM module could be used as a simple SE amp channel by itself.
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Old 16th October 2006, 11:58 AM   #22
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Default Re: TXS parallel

Quote:
Originally posted by psroczka
Russ,
You told about paralleling OPA 549, did you mean method from TI Application Note or paralleling two moduls for example TXS ?
Yes the datasheet gives a simple way to parallel the OPA549.

There are two ways to do it with the TPM-OPA549 PCB. You can do it by paralleling two identical circuits using an output resistor on each.

Or, you can set one module up for unity gain and take the output of the actual "Master" module as the input for the follower still using the output resistor.

The second approach is a bit simpler to wire, but the two circuits will not be as well matched, and it may not sound as good as using two identical circuits.
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Old 16th October 2006, 12:16 PM   #23
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Quote:
Originally posted by tschrama
How did you manage to make those beautiful 3D images?

Quote:
Originally posted by Greg Erskine
Looks like Eagle and Eagle 3D to me.

Greg is correct.

Very handy for visualizing PCBs.
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Old 16th October 2006, 01:03 PM   #24
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I might need to buy a couple of these. I always rated the OPA 549 as the better chip, and I have loads in my bits box. It'll have to work hard to beat the Symasym though!
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Old 11th December 2006, 10:08 PM   #25
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Default TXO-2 version done working :)

OK here is a simple 2 TPM-LM3886 X amp. Not merely bridged.

Here are some pictures which may help visualize what is possible, next I will add four more TPM-Lm3886 modules in parallel with the existing ones, this will easily give me around 250W of power into 4ohms.

Cheers!
Russ

Front...
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File Type: jpg test1.jpg (98.9 KB, 3011 views)
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Old 11th December 2006, 10:09 PM   #26
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Guts....
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File Type: jpg txo 009.jpg (90.2 KB, 1895 views)
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Old 11th December 2006, 10:10 PM   #27
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Close up of one channel. Both channels have independent transformers and power supplies.
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File Type: jpg txo 008.jpg (94.5 KB, 1958 views)
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Old 11th December 2006, 10:15 PM   #28
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There is still a lot of case wiring cleanup to do, but I am very pleased with the result so far. < 10mv offset.

Each TPM module has a DC nulling servo to keep the idle current under control and generally keep the amp happy. These can easily be omitted all together or replaced with a feedback cap (place on PCB for this) which will make the amp unity gain at DC. For me the servo is staying.

It sounds as good as anything I have heard with a national chip in it.

Cheers!
Russ
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Old 12th December 2006, 03:16 AM   #29
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Default Awesome!

Looking good. I hope to build one of these once boards are available. How much do you estimate this will output into 6 - 8 ohms with +/- 30 volt rails?
I have gathered most parts, picked up a pair of 400 va +/- 20 volt trannies. Not waiting on boards, still cleaning up a couple other items. This is something I hope to build sometime early next year. Is that close to your plan commercial release?
Wish I had left the family at Opry Mills one night and tried to swing by and listen last month.. Did not happen, problem with getting them out of the car in the 20 degree weather.

George
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Old 12th December 2006, 03:28 AM   #30
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Hi George,

Thanks.

No problem. Family comes first. The invite is always open for you.

I will be making a PCB order here very soon (before the holidays). Brian already has a good jump on the parts.

I hate talking about how my own amplifiers sound, but I can't really find any faults in this one. It is quiet when it should be, and loud when you want it to be.

As for output power you could expect something like (of the cuff) 80W into 8ohms from those rails. I am using 600VA 20V secondaries get roughly 34V rails (perfect for when I go parallel). But I will be putting in some 500VA 25V secondaries here soon (better for the 8ohm loads).

Cheers!
Russ
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