Rod Elliot P68-2 PSU Recomendations

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I will be building Rods Beefed up P68 with either his recomended supply or one similar to carlosFMs supply with split rectifiers and snubbers. -or- a design as recomended by somebody here. This is for a Linkwitz Tranformed set of Adire Shivas (later to be tumults) that will comprise the LFE of my HT. The beefed up 500w design could end up with yet 1 more set of output pairs to beef it up even more.

I gather that for +/-70 rails I will need a 50-0-50 toroidal transformer. Parts Express has an 800VA 50V AVEL LINDBERG, will this be suitable for both rails and offer enough power?

-Or- should I use (1) 25-0-25 (wired for 50V output) per rail/rectifier?

Secondly price is a concern, and this is a sub amp... For PSU filtering would the Panasonic AA (comoputer grade) be worth the extra money as opposed to the the lower grade TS-Series? IS there a better choice in this price range?

Please also recomend a brand/source (USA) for the bypass caps and resistors for the PSU.

Kind Regards,
Bill
 
Thanks... but not much help there.

I imagine my questions are pretty applicable to any amp and power supply.... The knowledge base here is much greater and why I asked in this forum. I did also search these forums and have read hundreds if not thousands of posts. I am more confused now than when I started. I am simply looking for definitive answers to these few questions.


Bill
 
Hi,
your 800va is 1.6 times your output power. This is right in the middle of recommended.
Will you ever ask your amp to drive a lower impedance?
If so then the transformer could be rated to 1.5 times the max output into lo Z.
I suggest a separate bridge rectifier for each rail, with adequate smoothing and good quality bypass caps.
regards Andrew T.
 
Assumung a monoblock...

Is the prefered method to use a single transformer with dual secondaries, 1 wired to each bridge? Or is it better to use a seperate transformer for each bridge? If both are acceptable what are the pros and cons (other than the obvious, SPACE and COST)

I will be ordering the transformers this week and need to make a choice.

A single 1kVA 50-0-50
-or-
(2) 800 VA 25-0-25 with secondaries wired for 50 Volts


Bill
 
Ok, if you use 2 800va's...do you have a circuit that can handle that? I had 2 1000va toroids on a 15A circuit and snapped breakers :) anyway, just kinda fyi. I'd stick with 1 800va from avel (or a 1kva...either would be ok). Would probably work fine unless you are running into lower impedences ...or...run slightly lower voltage ie 45-0-45 toroidal ...lower power into 8 ohms, but higher current capability :) later

-Matthew K. Olson
 
The HT will have a dedicated 120V 20 amp breaker just for the audio portion of the setup. A second breaker will power the projector and other devices. Inrush current limiters will be used and the only other amp will be a 6 channel gainclone.

The impedence is likely to be very low, as the SHIVAS voice coils will be paralleled. I am still not clear if using a transformer for each rail is recomended or is not as good as a split secondary.

Bill
 
I could have (and will) pose some questions on the ESP forum, but feel that there is a much greater resource of knowledge and good advice here. I wil also have questions for Rod, but don't want to waste his goodwill on beginer PSU questions. This whole project is a learning experience for me. I am new to amplifiers and audio signal manipulation. I come from a 1s and 0s background and feel more at home with ATMEL AVRs.

So I gather the problem with using 2 transformers can cause slightly different voltages between the bridges/rails? Does this appear as distortion on the outputs?

Bill
 
Using two supposedly identical transformers will yield no worse rail mismatch then a single unit. Note that rail mismatch is not the same as regulation.

The issue is simply that a single unit of the same total VA as two smaller transformers will have better regulation and ability to absorb noise/transients. It will also be significantly cheaper and take up less space.
 
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