ESP P3A component recommendations - diyAudio
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Old 30th April 2013, 01:23 AM   #1
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Default ESP P3A component recommendations

Hello everyone...

I'm interested in building a P3A to power a pair of Whatmough floorstanding loudspeakers in my lounge room.

I've built a few amplifiers kits, most recently the 41hz AMP6 which is powering my computer speakers. This is the first time I've had to source my own components. Note: I'll be ordering Rod's PCB.

After doing some reading here there seems to be a whole range of different suggestions for output transistors and passive components.

I'd really appreciate a "Bill of materials" consisting of good quality but not exotic components that will result in a great sounding amp. I'd prefer to buy everything from a single source such as Digikey or RS electronics since shipping to Australia is very expensive.
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Old 30th April 2013, 03:40 AM   #2
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Hi
When you buy Rod's PCB, you receive the circuit diagram and BOM etc. support documents with it. That's his product and details are discussed on his ESP forum.

There are many P3A cloning attempt threads here and people select what they think are good or better parts for the duty as it is an old, inexpensive, well known and understood design, as Rod indicates in his description. His current BOM is copyright, like the schematic and any site information. Posting that here is in violation.

However, plenty of people will make guesses and suggestions for you assuming the circuit diagram currently shown is actually the same as the one the current PCB is intended for! Read the notes re: the illustrative schematics shown on the site. What you see in the product descriptions may not be quite what you get. Many would just look at the pics and buy what they identify from catalogs or on-line. With a little practice, most guys here can identify common parts in seconds.
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Old 30th April 2013, 04:26 AM   #3
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Instead of going in the vague territory, why not build a time tested and survived Leach low TIM amp. It gives very good mids and highs and if set for higher Iq of 150mA, will be good at bass also. Documentation and pcb files are available on the net.

Gajanan Phadte
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Old 30th April 2013, 04:34 AM   #4
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Hello Ian, thanks for your reply. I recently stayed in Coffs on the way back to Brisbane during a drive down to the Hunter Valley. Lovely place.

I purchased Rod's P68 subwoofer amp board several years ago (never completed) and gained access to his secure website at the time. The construction notes for all his projects are listed there, and I've taken the liberty of looking up the P3A BOM, which details the component values, but not brand recommendations (e.g. I've seen references to Vishay resistors).
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Old 30th April 2013, 05:03 AM   #5
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Vague territory?
Elliott Sound Products - The Audio Pages (Main Index)
Check the many threads here too. The design has had massive numbers of builders for many years, worldwide.
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Old 30th April 2013, 06:54 AM   #6
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It may sound like terse general advice but resistor brands are unimportant. Types such as metal film, metal oxide, wire wound, low inductance wire wound are. The same with capacitors. Just don't buy from suspect sources where substandard product or alleged unobtanium is offered at very cheap prices. You could purchase any type on sale at Mouser, Digi-key, E14, RS etc. and you will get good quality that meets specification.

Often capacitor types don't overlap with many different suppliers so quoting WIMA polypropylene is nothing other than to say it's MKP etc and box format. Panasonic make similar product but in powdercoated form like Sprague "orange drops".

The difficulty with capacitor types is size difference. You must check at least hole spacing against lead spacing for Radial types and this dictates choice. Near ideal caps like polypropylene film, are about 10 times the size of mylar metallised film caps which in turn, are more than 10 times the size of electrolytic caps, so interchanging types is seldom an option.
Can I suggest the following inexpensive cap types to begin with:
MKT: any, but use highest voltage option that will fit, MKP: use WIMA.
Electrolytics: Panasonic FC or FM in small sizes, THSA or similar for main power rail reserves. Frequency compensation caps can be NPO ceramic, Mica, Polypropylene film, or Polystyrene film according to availability, budget etc.
You can be sure others reading this won't find their favourite types here and will post them too.

Real improvements in sound quality by component choice are best targeted at certain areas of the amplifier rather than a shotgun approach. Follow Sakis's P3a comparison threads for some hints after you have built it in standard form. He does get it to "sing". Few that I know, even chock full of very expensive parts actually do, IMHO. The testimony to that is that their amplifiers languish in the cupboard - not in daily use.

Without proper comparison though, you'll only be guessing and hoping too.
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Last edited by Ian Finch; 30th April 2013 at 06:56 AM.
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Old 30th April 2013, 11:08 PM   #7
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Good advice - ta. One last question: do you have any specific recommendations on the type and/or brand of transformer to use? I'm putting together a shopping list at Mouser and was thinking a 25-0-25V toroidal would be well suited?
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Old 1st May 2013, 04:20 AM   #8
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Quote:
Originally Posted by Ian Finch View Post
Vague territory?
Elliott Sound Products - The Audio Pages (Main Index)
Check the many threads here too. The design has had massive numbers of builders for many years, worldwide.
...but you will be surprized to know that the oldy is shown to be a winner when SIMed, by one diyer here.

Gajanan Phadte
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Old 1st May 2013, 05:26 AM   #9
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Quote:
Originally Posted by gmphadte View Post
...but you will be surprized to know that the oldy is shown to be a winner when SIMed, by one diyer here......
I know the designs quite well and have seen and heard several but not built them myself. Yes, I agree that these are very good amplifiers but I would not suggest starting there.

They are a little too big, complex and expensive for newbs, In my view. If we consider larger, more ambitious designs like this we might also consider the forum "Honey badger" design by Ostripper. That is also a good design that performs and sounds very well and has the inexpensive support of the forum management for PCBs and documentation also covering protection boards, power supply etc.

As a step up from CMoy-like toys and minimalist class A designs, I think a simple 60W class AB design is appropriate. The problem is the choices and compromises designers and builders often make within that type description. Some of the worst audio I've ever heard came from this type of DIY design area too. A properly built P3A is in another world, though. It can deliver sublime audio for very little money and its high popularity is a fair testament to it. Just yesterday, I counted 4 P3 threads on this forum's first page.
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Old 1st May 2013, 05:42 AM   #10
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Originally Posted by Ranchu32 View Post
Good advice - ta. One last question: do you have any specific recommendations on the type and/or brand of transformer to use? I'm putting together a shopping list at Mouser and was thinking a 25-0-25V toroidal would be well suited?
The type and voltage is fine for 50-60W 8R and more into 4R. A 160-250VA size should be ok, depending on the speaker load. We don't know your Whatmough model so may be able to check if you post it.

Using FEDEX (compulsory with Mouser, Digi-key) for a heavy item like the transformer, from the US, may be more expensive than you anticipate. You can also buy these at Altronics outlets here and possibly keep freight down to $40 for the balance of items.
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Last edited by Ian Finch; 1st May 2013 at 06:09 AM.
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