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Gieseler Audio

Power supply upgrade for Gross, Fein & Klein III DAC’s.

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Hi everyone - well I have just made a very interesting discovery regarding the power source for the Gross, Fein & Klein III DAC’s.

Purerly on a whim & at the suggestion from some knowledgeable people I decided to run a Gross DAC from my new M18 Kraftwerk 12v 4A PSU.

What! - as you all know I’ve been telling everyone for years all my DAC’s run on AC not DC so why would I be trying this.

Up untill recently all my DAC’s needed + & - internal voltages & the only way to do this is run them from a AC supply.

With the Gross & the new transformer output design it eliminated the need for negative supplies except for one small negative bias supply for the muting transistors.

Then about ten months ago I changed the muting system to a new photo MOSFET relay setup. NOW all of a sudden the Gross only had positive internal supplies

so the feasibility of runing from a external DC PSU was entirely possible.

But why would I try this? I go to a lot of effort with the internal PSU’s so I’m confident they are very good & I had already tried a much larger external transformer wth no sound change.

As I said before it was purely on a whim & was not expecting any sound quality change

OMG - I was totally gobsmacked at the sound improvement - I thought this can’t be right so I did the comparison another half a dozen times - same result!

Then I tried it the next day & then a few days later - the result was very conclusive that the big external DC PSU was significantly improving the sound.

OK time to see if any one else agrees so I asked a experienced Gross owner & a Fein owner to do the same comparison - conclusion - both agreed on the sound improvement.

Now 12v is not the ideal external dc voltage due to the voltage drop from the DAC’s internal bridge recifiers but it is safe & works very well. My next step is to modify the 12v 4A unit

for 14v output which will be the optimised voltage for all the DAC’s internal PSU to work correctly. While I’m at it I thought I would also try replacing the single main filter cap with 

a bank of 18 Silmic II caps which should improve things even more. However the Silmic caps are about $5 a pop so that option will bump up the price quite a bit.

OK so at this stage I will doing a 14v version of the 12v 4A M18 Kraftwerk PSU especially to just suit the Gross, Fein & Klein III - cost $375 - the same as the current model.

Plus a new pure Silmic II version at $500. I will order the boards tomorrow so about two weeks away.

Guys I’m so confident about this upgrade that all units sold will automatically come with a return for refund in seven days option if not completely satisfied.

IMPORTANT! Please no one try runing their Gross DAC’s on a DC supply untill checking with me first that their unit is compatible. Approximately the first fourteen Gross DAC’s

are unsuitable due the negative internal muting bias supply. It is possible for me to upgrade those units to the new photo mosfet relays so then they would suit the new DC PSU.

I will work out a costing on that soon.

Exciting times!

 

 

 

Edited by Gieseler Audio

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I’ll take one for my Gross, all silmac II version please. My serial No 22. 

 

How are are you going with Femto upgrade? I’d be keen to do that. 

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Hi naggots,

thanks for the vote of confidence -  I will be staggered if you aren’t impressed.

OK  I will check out your serial number model etc at work tomorrow & let you know.

RE Amanero femto upgrade 

 Unfortunately I’ve run into a few snags with that.

 However with the new power supply upgrade I don’t think you would bother wanting to do anything else as it really does sound that good 

Edited by Gieseler Audio

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This is great news Clay. Great to see you are experimenting in this way and continually improving your products. Will PM you re requirements for my unit.

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Hi Clay,

 

very interesting!

Will the 9VAC input of all new DACs now replaced by a 14VDC input?

Thanks

 

Matt

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Hi Matt,

 

no - it does bump the price up so all models will stay the same but the new PSU upgrade will be a permanent option.

A bit like the way Naim does it.

When time permits I will probably do a Uber version of the Gross & Fine that run directly from the big 12v AC 6A transformer.

Edited by Gieseler Audio

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Great news for all the current and new owners. Well done for the Australian Hifi scene. I hope some serious overseas exposure is seen soon. 

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Clay,

how is the procedere then?

When ordering a DAC we can choose either AC or DC input ?

Or have alls DACs both AC and DC inputs?

Thanks

 

Matt

 

 

Edited by matth

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All new Gross, Fien & Klein III's will run on AC or DC 

AC 9v  DC 12v - 15v

Std 5.5m 2.1mm power jack input.

The only exceptions are the special active versions of the Gross & Fein DAC. 

Edited by Gieseler Audio

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For any Gross owners wanting to do a quick check to see if it will suit a DC PSU.

Remove the lid & see if there is a blue power transformer on the board.

If so it is Unsuitable.

However I will be offering a modification service on the early versions to make them suitable for DC operation by changing them over to the photo MOSFET relay system.

A bit of time involved as the pcb has to be fully removed - negative bias parts removed or disabled, transformer disconnected & photo MOSFET retro fitted. I would think $200 would cover it & that would include return freight.

986841742_earlyGrossDAC.JPG.ea1cf22c28bdb8c9d4ebbbefaf06a71f.JPG

 

 

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