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Author Topic: Thunderfunk with Dead Power Amp Board  (Read 331 times)

pizzafrenchfry

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Thunderfunk with Dead Power Amp Board
« on: May 03, 2021, 05:27:54 PM »
Hello all,

First post on this forum. I have a decent background in Tube amp repair, but am just really digging into transistors.

I have a Thunderfunk bass amp where the power amp board has failed and immolated itself beyond repair. The amp is fairly obscure and no replacement boards, service documentation, or schematics are available.

The power supply and preamp and working, so I'm thinking this may be a good candidate to receive a 'drop in' Class D power amp board.

The amp was originally 550W into 4Ohms, so I've been looking at  the ICE 500ASP which has similar specs.

The supply in the amp is +/-94VDC and +/-24VDC, for the ICE module I need 42-85VDC  (nominal 75v) and +/-12VDC.

For the +/-12VDC line I was thinking of using a DC/DC converter into some LM7812/7912 regulators.

What would be a good way to drop 15-20V or so or so on the B+?

Anything else I should consider that I may have missed?

https://www.parts-express.com/pedocs/manuals/326-100--icepower-500a-class-d-amp-module-1x500w-data-sheet.pdf
« Last Edit: May 03, 2021, 05:36:48 PM by pizzafrenchfry »

Loudthud

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Re: Thunderfunk with Dead Power Amp Board
« Reply #1 on: May 03, 2021, 06:25:06 PM »
Like most of these modules, the output is balanced. That means you can't ground one side, and you shouldn't use phone type plugs because there will be dangerous Voltages on the metal shells.

There is no good way to drop Voltages to what you need. You can burn several hundred watts via analog means, or build a switching regulator :(

pizzafrenchfry

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Re: Thunderfunk with Dead Power Amp Board
« Reply #2 on: May 03, 2021, 07:29:04 PM »
Like most of these modules, the output is balanced. That means you can't ground one side, and you shouldn't use phone type plugs because there will be dangerous Voltages on the metal shells.

There is no good way to drop Voltages to what you need. You can burn several hundred watts via analog means, or build a switching regulator :(

Good point, that would be a big drawback. I've heard these ICE units are used in several commercial bass amps. I wonder how it's implemented.

I was considering using something like the MOSFET voltage reducer attached. There is a large heatsink in the chassis already and a fan. Would require a large power mosfet in the several hundred+ watt range, but I believe this would work.

joecool85

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Re: Thunderfunk with Dead Power Amp Board
« Reply #3 on: May 04, 2021, 11:50:47 AM »
Like most of these modules, the output is balanced. That means you can't ground one side, and you shouldn't use phone type plugs because there will be dangerous Voltages on the metal shells.

There is no good way to drop Voltages to what you need. You can burn several hundred watts via analog means, or build a switching regulator :(

Good points, and all the more reason to not use 1/4" jacks for speaker connections.  Time to use Speakon connectors.  It's been 25+ years, time for the industry to transition!

Regarding the voltages, you could use a DC/DC converter, but honestly I would just build out a new PSU for the power amp.  Leave the existing for the preamp if you'd like though.

**edit**
I just looked at the datasheet you shared.  The +/-12v is for input voltage, IE signal.  Your preamp will provide that without issue I would guess.  You do need about 75v DC for the PSU though.  Looking at Parts Express, it seems that the board you linked is for use only to add on to another "ICE" board.  They recommend using this one with it's built in PSU for $312 USD: https://www.parts-express.com/ICEpower-500ASP-Class-D-Audio-Amplifier-with-Power-Supply-Module-1-x-500W-326-204
« Last Edit: May 04, 2021, 11:59:00 AM by joecool85 »
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