Rod Elliot P68-2 PSU Recomendations

[BeanAnimal]

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

[MEGA-amp]

http://www.instantboard.com/users/rode/index.php

This may help


jh

[BeanAnimal]

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

[AndrewT]

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.

[BeanAnimal]

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

[Mattyo5]

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

[BeanAnimal]

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

[richie00boy]

I'm surprised you felt you could not get the information required from the ESP forum. I'm sure you would have been answered quickly.

Just use a single transformer. It will be smaller and offer better regulation, assuming the same total VA of course.

[Mattyo5]

Ok, if impedence is going to be low, use a 1kva toroidal with 40-0-40 rails... lower power into 8 ohms, but greater power into lower loads ...and better stability i think. Thats what i'd do anyway. Good luck

-Matthew K. Olson

[BeanAnimal]

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