[Freo-1]

These are 1625 mono block amps that were just finished by my good friend.  They sound excellent, and will sound much better as they break in.
The soundstage is both wide and deep, and much a more noticeable 3D effect than other amps I have on hand.  I put in a pair of 12SX7 input tubes, and 1940's RCA Army Signal Corps output tubes.  It sports NOS ceramic sockets from the 40's or early 50's.  It also has NOS chokes from Chicago Transformers from early 50's. It also has mil-spec 10 turn bias pots, 1 watt PRP resistors, about 3 times reserve cap storage,  Mundorf Silver/Gold coupling caps, Cardas copper binding posts, and Vampire RCA jacks.  They are dead quiet, as quiet or quieter than most solid state amps.

If one is going to use tubes, an amp like this makes a lot of sense.   The output tubes are cheap and plentiful, long lasting, and MUCH better made than any current production tubes.  The 1625 is a 12V 807 tube.  My buddy says the war was won with these tubes.  They sound a lot like NOS 6L6, but better (IMHO), as you can run the plate a higher voltage due to the plate cap. 
So, I'm pretty happy with them so far.
 

[Ericus Rex]

Very nice!  Were these built off an existing schematic or did your friend design them as well?  MORE INFO NEEDED!!!!

[underdawg]

very nice build

[Freo-1]

Very nice!  Were these built off an existing schematic or did your friend design them as well?  MORE INFO NEEDED!!!!

 
Thanks.  My buddy did a great job building this.  I bought the transformers and coupling caps.  I had to order the power transformer as a custom unit, with four taps for the various power requirements.  He had the rest of the parts on hand.  I am amazed how quiet it is. 
 As far as the schematic goes, the exact circuit values are proprietary, so regretfully, cannot share them.  My buddy got the schematic from a well know industry participant many of you know or are familiar with.  He provides them to my buddy as a personal favor.  Look for the Radiotronics No. 124 on the web, which is a 45 watt push/pull design.  It is similar to this:
 http://www.joeltunnah.com/A515.pdf
 
 Added grid and anode stoppers to ensure no oscillation will occur.  There is some excellent information at the DIY website on this. 
 

[FullRangeMan]

A beautiful amp, congratularions.
The 807/1625 is a nice Pentode for audio, alog with the 813.

[Freo-1]

Thanks!  I am very happy with the sound and build quality.   
 
This amp proved to me the pentode sound can indeed be very musical.   

[Freo-1]

I've been using the mono blocks with this tube preamp:
 
http://www.audiocircle.com/index.php?topic=110027.msg1134725#msg1134725
 
The combination sounds outstanding.  The amps are strating to break in, and smooting out quite nicely.  It takes some time for the Mundorf caps to break in.  Tubes have a certain natural presentaion in the midrange that solid state just can't quite seem to achieve (although the best solid state gets pretty close). 
 
If one wishes to use tubes long term, either need a fair amout of disposable cash, or, go the DIY route.

[Bill O'Connell]

Very Nice!

 Try to find some Tung-sol 12SN7 black-glass round plates. The 12SX7 tubes are warmer/thicker but not as extended as the TS.
Also, be careful with those top-caps,lethal voltages

 The Mundorf Silver/Golds are great caps.


 

[Ericus Rex]

Same buddy made both?  He should go into business!

[Freo-1]

Yep, same guy.  He does outstanding work.
 
I'll scout around for the TS 12SN7's.  The 12SX7's in there are Canadian GE MIL-SPEC units.  They look exactly like the old Sylvania 12SN7's from the early 50's, with the flashing on the bottom.  They sound pretty good.
The top plate cap wire is safe, as long as the amp is off when you go to change the tube!