flak monkey

ESP P101 Stereo Power Amp Build

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Super Wammer

A little winter project and I'll add more detail as I get into it...

I'm currently using the power amp stage in my XTZ A100-D3 amp coupled to my SP12/PH12 pre.

I'm waiting for a pair of these boards to arrive: http://sound.whsites.net/projects.htm

And one of these cases to house it in: http://www.ebay.co.uk/itm/271984251495

The components are all due to arrive today from Digikey, and I'll be ordering a 500VA 0-40-0 torroidal transformer from Airlink.

Hopefully everything will arrive before Christmas so I can make a start getting it built up - looking forward to seeing how it works... :)

Anyone else built one of these before?

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I have a few of the boards and a mate of mine is putting 4 of them in with a small x86 PC and a multi-channel USB DAC to make a digital active system.

He's in the middle of buying 1cm squared copper bar for the power supply! :D

Once it's all up and running we're going to have some fun configuring ALSA to do the speaker crossovers and room eq

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Super Wammer

Sounds like a nice set up :)

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Super Wammer

Ok, I have most of the small components here now.

The mosfets should arrive from Profusion tomorrow, I went with matched sets of ECX10N20-S and ECX10P20-S.

The transformer from Airlink will also be arriving tomorrow.

I have no idea when the PCB's and case will arrive... both on a slow boat from the other side of the planet!

IMG_20161215_200348_zpshzhosyky.jpg

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Super Wammer

The case arrived from Hong Kong today - not bad, it was picked up on Christmas Day.... it wasn't cheap, but it's all solid aluminium. I'll mount the amplifier boards vertically, one on each side on the heat sinks.

It's been freezing out in the workshop, so I've been making a mess on the living room carpet drilling the panels and getting a few of the main bits mounted (don't worry I hoovered up when I was finished)... the circuit boards still haven't arrived. Hopefully they will soon!

Kept the front clean and simple, just a single blue LED power light

IMAG2747_zps7tz7qwge.jpg

So far inside is the 500VA torroid, the 35A bridge rectifier and the start of the filter cap bank - there's 2 more to add (6x 10,000UF) and the main ground plate to solder on. The white bit of foam is a placeholder for the soft start circuit board.

IMAG2750_zpsemaroux3.jpg

The back panel, main power inlet and switch in the centre. Speaker binding posts and then the RCA's.

IMAG2751_zpsdfna51dt.jpg

There's a lot to do yet...

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Did you also order the output protection boards too?

Looking good so far :)

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Super Wammer

Yes, I'm planning on fitting speaker protection as well, I'm waiting for all of the boards to arrive....

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Super Wammer

Progress is very slow as I am still waiting for the boards to arrive from Australia. But I got another delivery from Digikey today, which included all of the components for the speaker protection and soft start boards.

So I just spent a little time mounting the output relays and completing a little of the wiring to them. Don't worry, I'll tidy the wiring up when its done... and there's still a lot to hook up. I'm also still missing one pair of main power caps, they'll be added soon....

Output relays are a pair of 30 amp, 24v coil mounted as close to the speaker output as possible - the speaker output is connected to the common terminal on the relay (pin 30).

The relay coils will be connected in series, with a 110ohm resistor to drop the extra voltage from the 56v supply for the amps.

The 5W 3.9ohm resistor and 100v 10uF bi-polar cap across the output terminal is a little protection for the relays if they are ever called into action, a little overkill considering they are only about £4 each, but it might just save them if there is ever a fault. Once I know everything is working as it should I'll apply a little hot melt adhesive to support the resistor and capacitor.

The NC (87a) relay terminals are connected back to the earth terminal (that will prevent any fault DC arcing across the terminals to the speakers), which in turn will be connected to the main star ground and chassis ground for the whole amp, which will be a copper plate bridging the central pins of the power supply capacitors.

IMAG2821_zps51syv5if.jpg

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Super Wammer

It's going very slowly but getting there....

It's mostly just mocked up at the moment, and I'm more or less set on the final internal layout now.

Still an awful lot to do, but it should be done in a couple of weeks :)

IMAG2826_zpsgkkgbq9u.jpg

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Super Wammer

Today I more or less finished off the power supply side of things. Waiting on some mica insulators and fuse clips before I can finally mount the amp boards to the heatsinks. They should be here Monday.

There's still some clipping/tidying to do but in general all of the power supply is done with the exception of the soft start board.

Power to the 500VA torroid will come from via the soft start board. The dual 0-40 secondaries are linked, with the link wired back to the main ground plate giving a 40-0-40 output. That goes to the 35A bridge rectifier.

Output from the rectifier goes to the capacitor bank which is 6x 10,000uF caps. Main ground plane for the whole assembly is the copper plate soldered across the centre pins of the caps, this effectively acts as the star ground point for the whole set up. The loose white/black (9VAC) and brown/red (240VAC) wires will connect to the soft start board when I have it built...

To reduce noise the caps are linked with 0.1 ohm 5w resistors rather than wire links - this does reduce power marginally, but it's not significant enough to worry about. The +/-56VDC outputs to the amps are Blue/Red/Black wires that run around the outside of the case. All of the noisy AC runs in the middle of the case, and as far as possible from the DC supply.

IMAG2834_zpslzhj0fi1.jpg

Here's the boards less the fuse clips...

IMAG2836_zpssizickk9.jpg

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Super Wammer

Well it seems the guys over on DIY audio don't like the idea of using a copper plate for the main 'star ground' point. But I'm going to try it and see what happens. 

I got the idea from the Elliot Sound Products page, so he obviously seems to find it works OK. 

One way to find out!

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Super Wammer

A lot of people saying the same thing in different ways....

Quote

Bad idea. You have lost control of where the currents go. A simple copper wire (or PCB trace) bus is better. One end goes to the secondary CT. The other end goes to the circuitry, and also may have the speaker returns. Along the bus go the PSU capacitor joins.

Edited by flak monkey

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Makes sense. But like you say, only one way to find out if there's an audible difference. 

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Super Wammer

I like a little adventure.... easy enough to change if it doesn't work. :)

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