55 WPC 1625 Mono Block Amps - diyAudio
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Old 31st January 2013, 10:39 PM   #1
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Default 55 WPC 1625 Mono Block Amps

1625-3.JPG

1625-2.JPG

1625-1.JPG

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 output power is around 55 WPC. I had to special order a pair of power transformers for the voltage taps. There are separate power supplies for the 12SN7 and 1625 tubes.

The soundstage is very wide and deep, and a much more noticeable 3D effect than other amps I have on hand. The theory as to the depth of the soundstage is use of 1 watt PRP resistors vs. watt units. I put in a pair of 12SX7 input tubes in the 12SN7 slots, and 1940's RCA Army Signal Corps output tubes. It also sports NOS ceramic sockets from the late 40's or early 50's, along with NOS chokes from Chicago Transformers from early 50's, mil-spec 10 turn bias pots, 1 watt PRP resistors, about 3 times the required reserve cap storage, Mundorf Silver/Gold coupling caps, Cardas copper binding posts, and Vampire RCA jacks. They are dead quiet, as quiet as 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. The 1625 tube sound a lot like NOS 6L6, but better (IMHO), as one can run the plate at higher voltage, due to the plate cap.

So, I'm pretty happy with them so far. Also, a note of thanks to Miles Prower is in order. Researching the threads uncovered an issue with oscillation that was easily corrected with the plate and grid stoppers. The posts by Miles helped me sort this out quickly.

Last edited by Redwingnine; 31st January 2013 at 10:42 PM.
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Old 31st January 2013, 11:34 PM   #2
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I recently built a SE 1625 Pentode amplifier - also with Edcor iron - they're great tubes!
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Old 31st January 2013, 11:55 PM   #3
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Ssshh! We don't want a run on these tubes

Yes, I agree, the 1625 is a great tube indeed. I went PP to get the extra watts.

Do you have pics of your amp?
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Old 1st February 2013, 01:25 AM   #4
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schematic?
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Old 1st February 2013, 02:19 PM   #5
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Quote:
Originally Posted by Redwingnine View Post
Ssshh! We don't want a run on these tubes

Yes, I agree, the 1625 is a great tube indeed. I went PP to get the extra watts.

Do you have pics of your amp?
Attached Images
File Type: jpg 1625_amplifier_front.JPG (83.8 KB, 238 views)
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Old 1st February 2013, 04:27 PM   #6
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My 1625 SE, PS and output transf. are is black box on the left side.
https://picasaweb.google.com/1095707...83041150319842
https://picasaweb.google.com/1095707...82994959008034
.....very, very deep scene!

Last edited by azazello; 1st February 2013 at 04:32 PM.
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Old 2nd February 2013, 03:03 AM   #7
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Quote:
Originally Posted by aardvarkash10 View Post
schematic?

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
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Old 2nd February 2013, 03:05 AM   #8
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Kstagger, can you post some additional data on your amp?
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