Allen Model 75 KT88/6550 mono amplifiers. Restored. - diyAudio
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Old 25th July 2011, 09:29 AM   #1
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Join Date: Jul 2007
Location: Maplewood MN
Default Allen Model 75 KT88/6550 mono amplifiers. Restored.

Allen Model 75 KT88 tube mono amplifiers.


My Allens have been recapped with Solen and remaining electrolytics have been replaced. Any out of spec resistors have been addressed also. Additions consisted of off/on switching, power-on indicator lamps and heavy duty power cords and level attenuators.

Massive wide band (audio) Acrosound and Saratoga output, power and chokes. Point to point wired, Allen amplifiers were over designed for decades of constant use powering large church organ systems. There are a handful of organ amplifier manufactures out there that made amps that perform well for audio applications after mods and output transformer changes, but most take a back seat to the Allens IMO.

Each amplifier weighs 50-60 LBS each . Shipping containers and materials are going to add to that so figure 65 lbs shipped x 2.

The work was done here in town by a local retired Navy electronics tech. He is very knowledgeable, thorough and did a wonderful job. I provided him with pages of internet notes on the slight circuit mods needed that make the 75's into great audio amplifiers. The stock 75's without them are nice but possess too much gain (from what I understand) with out them. That was addressed and the results are very, very nice. My needs have changed and I move into further into high efficiency speaker designs and although they are great to own, I no longer require high power tube amplifiers like the 75ís.

I keep vacillating back and forth as to whether I really want to sell these. Itís tough to let them go but I just donít use them enough to justify keeping them.

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Tube compliment/amplifier:
2- Penta Labs KT88
2- 6SN7GTB
1- EF86
1- 12AY7

I have the schematic for these that notes the circuit mods and biasing info.

$ 1550.00 obo plus shipping. PayPal will add 3% to the total if you want to go that route. Iíd also accept Postal money order or personal check if I know you.

Thanks,
RC
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Old 25th August 2011, 11:18 AM   #2
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Join Date: Jul 2007
Location: Maplewood MN
*** Bump ***

Price reduced to $1400 plus shipping


I have received some nice trade offers and some of which have been quite tempting. Be that as it may, I really need to just sell these outright.

The only thing that I would somewhat entertain right now would be a tube amplifier or preamp (passive or tube) that would offset the price by $400 -$500 at most. A nicely done Bottlehead preamplifier or similar DIY would be nice.


Thanks, RC
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Old 28th August 2011, 01:46 AM   #3
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Join Date: May 2009
Do you have the notes available?
The silver output is the acro?
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Old 30th August 2011, 12:03 PM   #4
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Join Date: Jul 2007
Location: Maplewood MN
Quote:
Originally Posted by deepgroove View Post
Do you have the notes available?
The silver output is the acro?

Hi, deepgrove. Sorry about the delay in responding to your question. I just now noticed it.

All I have is a schematic that notes the changes that were made. I had a two page that noted circuit mods in greater detail along with a ziplock containing all the parts that were replaced. I kept the bag of replaced parts for quite some time but finally tossed it. The notes for the amp circuit mods that were made is around here somewhere but I have been unable to locate them. I remember filing them away in a safe location so they would not be lost or thrown out inadvertently. I think I was too crafty for my own good because I can't find them for the life of me.

Yes, the amp on the right is all Acrosound.

RC
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