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I just wanted to let everyone know that I am nearly complete with my Lafayette KT-550 rebuild. This amp is just awesome. I will try to get a full review and some comparisons to other amps at sometime once things are settled. I changed out caps, resistors and tubes. Kept the original transformers and chassis (so far).
During this whole process, Don Sachs helped me thru many twists and turns. He essentially taught me many do's and dont's while exploring the KT-550. Don's expertise was invaluable. If you ever want to have a Citation or Lafayette rebuilt by a professional doing master craftsman work, please don't hesitate to contact Don. Much thanks to Don!!
http://www.dsachsconsulting.com/
Follow Ups:
Aw shucks... thanks guys! I just finished a KT550 for a customer and it sounds fantastic. I didn't want to gush about it because that always raises core prices! However, in this case there are so few of them and everyone knows anyway. Jim McShane and I discussed a few improvements and then I did them. I posted a few photos on my site in the gallery page, but I didn't want to post here because that is sort of advertising and I think that is a no no on this forum. However, given that this amp is not for sale, it is being shipped back to its owner after the crazy shipping damage season that is Xmas, I guess it is ok. You can check it out the link at the bottom of this post. There are a few pieces on that page, but the KT550 has three photos and they will scroll by. Here is what Jim and I cooked up.1. We added a separate screen supply since there was room on the bracket.
2. Of course totally beefed up the doublers and filters ala the citation II
3. I put in diodes to split each channel's B+ and screen supply before the filter caps, also added a pair of CL150 on the B+
4. Added cathode and screen resistors.
5. Improved grounding using a nice bus on the PS bracket
6. K40 caps as the main couplers and all those terrible electrolytic signal path caps are Solens now.
7. Good quality resistors everywhere and silver micas for the little feedback capsI had to basically rewire the amp to pull all the old brittle wire. The original design had the output tube cathodes going through the meter switch to a single ground point. The meter was toasted on this one so I just grounded each cathode through its resistor to the ground bus. I then installed small tip jacks on the rear for each output tube so you can bias it without opening it up. Works great. To do AC balance you can just take the reading across each tube pair as well. Works like a charm. Also added the nice big Belden AC cord we make up for the Citation II.
Amp is stunningly good. Not much else I can say. Very much like a Citation II...no surprise, the circuit is very similar and Stu H designed them both. Old boards are a pain, but I found all the bad spots and fixed them. It should run another 40 years now!
Wish Santa would leave me a KT550 core under the tree!
cheers,
Don
Edits: 12/20/13
Love the website..Beautiful.
Some people like second order distortion in their tube amps,some people like honesty in their tube amps. I like honest!
thanks Mikey! I have to post other photos, but I never get around to it. I finally rebuilt the website to look more modern. Always a work in progress! But soldering pays the bills, not fiddling with websites! The KT550 is a great amp. Sort of a 6L6GC version of the Citation II. It was built with crappy parts, but as you well know, if you put good parts and a good power supply in what is a very good circuit.... well the magic appears. I hate old PC boards though... Give me those mil spec turret boards in the citations!
His rebuild of my Sherwood-5000 is nothing short of spectacular. Listening right now to some Bill Charlap. So nice.
Paul
Not only is Don a master craftsman, he is a knowledgeable and exceedingly generous sharing information and suggestions.
There are a number of fine people in this hobby, and Don is definitely one of them. A public thanks for all the help he has given me over the years.
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