class d amp repair

Seymour Duncan Powerstage 170 Repair

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Seymour Duncan Powerstage 170 repair

This Seymour Duncan Powerstage repair was a pretty simple job and was turned around next day for the customer on my express service. The customer was an American pop punk band, currently touring the UK.

Though he normally used a step down converter. Unfortunately the customer had inadvertently connected his 110V seymour duncan powerstage to UK mains (nominally 230V, really 240V) and it had blown up spectacularly.

The part that was blown up is a hifi poweramp, made by a subsidiary of Bang And Olufsen. They’re used in many amps nowadays, including Gallien Kruger, Acoustic Image, Fender Bassman 500 and Fender Tonemaster.

Icepower module replacement Seymour Duncan Powerstage 170 repair

Ironically, the unit has an internal selection for 110V/230V to allow the unit to be swapped very quickly between UK and US mains. I’m not giving details of what to do online as encouraging people to meddle with mains electricity is beyond the scope of this blog!

The band’s tour manager brought the unit in for repair and I got the new power amp module delivered on next day shipping.

I set the Powerstage back to 110V operation for the customer as had a spare for UK gigs but were touring US again immediately on their return.

If you have a Seymour Duncan Powerstage 170 that you need repairing, please do drop me a message.

Acoustic Image repair – Clarus 1

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Acoustic image repair Class D amp repair

It’s always interesting to get something in that’s a bit different – this was my first Acoustic Image repair. The amp is a Clarus 1, now discontinued. It’s a great bass amp in a very compact and lightweight form, made possible by the use of a Class D power stage.

I’m a big fan of class D amplifiers such as this Acoustic Image – in my ‘other’ job I’ve designed quite a few for a leading audio equipment manufacturer. They’re lightweight, efficient, sound great and they’re quite easy to repair, but they do take some careful designing.
Acoustic Image repair
This particular amp had blown a FET and a gate resistor in the output. The FET turned out to be obsolete upon investigation, so I have to thank Laurence of Acoustic Image UK and Rick Jones, Acoustic Image owner, for helping me to identify their approved alternative part. The choice of Class D FETs has to be carefully made to fit the design otherwise they will not operate reliably. This is demonstrated in the image below. The waveform should have very little ringing, and very little curve on the waveform top.
Acoustic image repair Class D amp repair
I noticed that the reservoir capacitors were bulging slightly – possibly a sign of age or linked to the output failure. I suspected that these caps were the cause of a quiet crackling noise observed when I’d fixed the output so I replaced these with high quality parts. This fixed the crackling noise.

The Nottingham based owner was happy with the repair and kindly left me a review:

If you have an acoustic image repair, please get in touch.