Tuesday, August 20, 2013

My Handbuilt 6550 / KT88 Dual Rectified Amplifier - Demo both clean and pushed into Sag

For fans of vintage tube goodness here is a demo of my custom built 6550 tube amp.  I've owned this for quite a few years and it was hand-built by any amazing musician tech who sadly was losing his sight and had to get rid of most of his gear.  

The amp uses a rare vintage circuit that is similar to the lat 1950's Tweed Twin with a pair of rectifier tubes.  here is the lineup:

(3) 12AX7 (or any similar 12 volt preamp tube)
(2) 6550 / KT88 tubes (or you can straight swap 6L6GT's or even 6V6's)
(1) 5U4 Rectifier tube
(1) 5Y3 rectifier tube

The amp controls include the following:
- Preamp gain
- Bass and Treble tone controls (on a concentric pot)
- Volume
- Midrange tone control
- Presence control

It also has a traditional "hum" control pot but it never seems to hum much to me so I leave it alone.

There are two 1/4" output jacks -0 one for 8 ohms and one for 16 ohms.

It has a single 1/4 input on the front of the amp and a green indicator light.

The sound can be incredibly clean depending on what preamp tubes especially the one in the first position.  But when you turn up the preamp gain the rectifiers are pushed into amazing sag that can be saturated enough to be similar to a vintage germanium fuzz circuit but mostly just sounds like sweet output tube drive.

Check it out:



  1. I spy some very nice looking Magnatones! That little hand wired amp does sound good though, I bet even better in person

    1. Just one. The one on the bottom is a Magnatone M10A Custom, next to that is an Airline 62-9013A and a Fender '65 DRRI, the top amp on the left is not a Maggie, it is a 1947 Masco MAP-120 (highly underrated tone monster) and to the right (off-screen) is my Electro M8E, which ranks high on my list of best low wattage single ended amps. My Marshall Studio 15 is not in the picture, I keep it in the house. And yes, the amp sounds much better live, it is hard to capture thick output tube distortion without the benefit of a quality mic but I hope you get the general idea. - JC

  2. Umm...I don't see a price or contact info. I am new here so perhaps I am missing something. I assume all the items listed here were for sale. Is this not for sale????


I appreciate your comments but please no commercial links or non guitar related conversations. Thank you. - JC


I am reposting items here that are listed on CRAIGSLIST throughout the USA. I am not selling any of these items and I cannot facilitate the sale of anything here - so please do not comment or post questions like "Is this still available?" or "I am interested in your guitar please call me, etc." You need to contact the seller directly by calling the phone number listed on the post or by going to the CL listing and emailing them. NEW FEATURE: Click on the title of the CL Listing inside my post to LINK thru to the original Post. If the original CL listing is deleted the item most likely is no longer available. Thanks for checking out my blog and GOOD LUCK!

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