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Old 23rd January 2002, 11:20 PM   #1
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Default Trimodal Power amp and Precision Pre amp

Has anyone out there got a setup of Self's Precision pre-amp and his Trimodal power amp?

CAn anyone give me:
Opinions?
Performance (Watts into 8 Ohm)?
Ease of fitting it all into various cases?
Power supplies (and/or specs) to use?

I'm thinking of implementing this setup and would like to hear from people who have already done so (or similar).

This is my frst foray into the self-build region of hifi!

Thanks

Pete.
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Old 26th January 2002, 02:15 AM   #2
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I have built a "custom" version of the precision pre-amp '96, using my own PCB's and it is great. Noise is extremely low, as well as distortion using standard (NE5532) op-amps. I highly recommend the design... you can bump up the supply voltage to +- 22 volts to get even more headroom if you like, by simply changing a couple resistors in the power supply -- you better slap some sort of heatsinks on the 5532's however as they will get VERY hot.

Haven't heard or built the tri-modal amp, but from looking at the design and reading Doug's artical is looks very promising. I would also like to know of anyone's experience with this amp!
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Old 26th January 2002, 01:13 PM   #3
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Hi there,

I built the tri-modal amp by D. Self, but I didn't incorperate the Class switching, so it ran in pure class A.

Sound was completely neutral, no warmth, no harshness. For some, this is what they are looking for, others want a bit of warmth. Lots of detail to the point it 'sparkled' (for want of a better term). At higher volumes, it had no hint of compression, or change of character. I can't comment on the exact power, but given Self's infatuation with numbers, and design, I believe it gave out exactly what it was designed to.

I desined the PCB's on paper, and etched them myself. It was a fairly straight forward process, but not advised if you are new to electronics, better to buy the PCB's offered by Self. I didn't have any problems with hum or noise, but apparently it may have a few problems if you don't follow Self's instructions on the input and output filtering.

The usual comments for the power goes, ie get a transformer capable of at least twice the power as is drawn by the amp, and the more capacitance the better, even though Self's analysis says it doesn't make a difference.

It is an amplifier designed to have extremely good numbers, that is THD, noise, efficiency (in both Class A, AB and B). I liked it.

Hope this helps,
Adrian
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Old 28th January 2002, 04:23 PM   #4
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Thanks.

I'll probably be purchasing the PCBs soon.
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Old 1st February 2002, 10:18 AM   #5
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Hi There,

I have built the Precision Preamp and have been using it now for 5 years 6 in september the only thing i have done recently is change the opamps from the standard 5532/34 combo to opa2134, I left the phono section because, The circuit is somewhat "designed around" the 5534.

Changing the main opamps improved the sound somewhat but i am not sure it was worth the extra expense

There are some pics on my site.

I have not had any experience of the trimodal, but i read about the load invariant power amp, in wireless world when it was first published

Dan
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Old 11th February 2002, 05:16 PM   #6
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Thanks for your views!
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Old 11th February 2002, 07:18 PM   #7
Helix is offline Helix  United Kingdom
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hey pete, sorry it's off topic, but i live in tonbridge too!

working at time electronics, part working and part studing at oxford uni
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