ST70 mods - THE REFERENCE

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poseidonsvoice

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ST70 mods - THE REFERENCE
« on: 30 Aug 2009, 12:47 pm »
There is really no better than K&K Audio in my opinion. I've heard a great majority of them from Van Alstine to Welborne, and this fella takes the cake.

My reference for a 12 watt standard EL34/KT88 differential amplifier. The output stage uses current sources as well and is very much akin to ideas presented by Allen Wright in his DPA 300B differential designs, just different tubes.

Here is a nice review. I'm a proud owner myself.

In the spirit of DIY!

Anand.

JoshK

Re: ST70 mods - THE REFERENCE
« Reply #1 on: 30 Aug 2009, 05:30 pm »
The output stage uses a CCS in the tail?  I didn't know it was a fully differential amp.  Very cool.

I need to get back to work on my Karna.  Its actually not going to be the Karna exactly as I am using K&K's version of the first two stages.  Essentially, instead of two interstages the first one is configured as a differential plate choke instead of an interstage.

The power supplies are ready to be wired up, but I haven't started on the main blocks.


poseidonsvoice

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Re: ST70 mods - THE REFERENCE
« Reply #2 on: 30 Aug 2009, 08:24 pm »
Quote
The output stage uses a CCS in the tail?  I didn't know it was a fully differential amp.  Very cool.

Yes. And a few other tidbits make this a serious contender. Its close to his fully decked out differential 300B amp he has except the driver and output stage are capacitor coupled instead of transformer coupled (hard to do that and make it retrofit a stock ST70 chassis).

More info here.

Keep us updated on the Karna exploration...

Anand.


mgalusha

Re: ST70 mods - THE REFERENCE
« Reply #3 on: 30 Aug 2009, 08:46 pm »
I suspect that would sound very good indeed. I have been running my Mc 275 with that same transformer performing the phase splitting duties and it's a very different animal that running it single ended.  :thumb: I really like what current sources do for the linearity of tubes, so I'm sure the combination is sweet.