6550 triode strapped amplifier (~25wpc)

[deicide67]

Hello,

I have a triode strapped 6550 amplifier for sale.

This amplifier has a full choke input triode strapped 6550 amplifier using all old stock organ transformers. It uses a 980 volt center tapped organ tranny directly into a 4H choke with 940uf of capacitance for a modest B+ of 375v. The output transformers are old Baldwin trannys (From the 45) 3800ohm primary with an 8 and 16 ohm secondary(I used the 16 ohm tap for NFB and did not wast the time to tap another hole in the chassis since most modern speakers do not present a 16 ohm load). The power transformer and choke are from a Hammond organ. I'm not sure the model number, but it is BIG! After two hours of play time, I can easily put the back of my hand on the bell housing without even flinching. Plate voltage should not exceed 400v on the 6550 in triode according to the datasheets thus the 375v B+. I used a similar circuit to the ST-70 DIYTUBE circuit modding certain values to use the 6CG7 instead of the 12AU7 for the phase inverter stage as it is mine and many others that the 6CG7 is a much better phase inverter. I used a bus grounding system combination into a star ground at the chassis near the first filter cap. Biased at 50mA this amp is also dead quiet. It has a 3/8" piece of purple heart for the front cover, and I left the sides of the 2RU chassis uncovered for ventallation. It has a full bottom plate and feet and sits a nice 1/2" from the table and the entire chassis is less than 2" tall.

A nice feature of this amplifier is that it has individual bias for each power tube. This way, if you have a mismatched old stock quad or piece a quad together, you should be able to bias them accordingly to get them to dissipate evenly though there are limitations such as old tubes close to the inevitable death.

I am leaving this hobby for a while and plan to sell most of my extra gear and downsize to a smaller system. This amplifier will include a power cord, a pair of NOS 6CG7s, a new Sovtek 12AX7 WXT, and a random quad of 6550s that do not match form what is left of my stash one, as you can see form the pictures is a Sovtek and the others are Tung Sols rebranded for MESA guitar applications. I have sold most of my tubes like I said in exiting the hobby for a while.

Please feel free to ask me any questions about this amplifier. I did build it and it is a solid performer and sounds great. It is all point to point using good quality components. I am posting it here because the Baldwin ouput transformers are suppose to work very well with Klipsch speakers. I have no reference since the only Klipsch I have access to are newer bookshelf speakers and I'm sure they pale in comparison to the old monsters Klipsch is known for.

Asking: $700 obo for this amplifier shipped.

Here are a few pictures of the amplifier:

http://img.villagephotos.com/p/2009-...Picture025.jpg

http://img.villagephotos.com/p/2009-...Picture026.jpg

http://img.villagephotos.com/p/2009-...Picture027.jpg

http://img.villagephotos.com/p/2009-...Picture028.jpg

http://img.villagephotos.com/p/2009-...Picture029.jpg

http://img.villagephotos.com/p/2009-...Picture030.jpg

** Please note that the splotchy looking areas in the pictures do nto exist. It is the camera. Also, you can see that each one of the old stock trannys has a small dent in the bells. On the output trannys, these are on the back and will not be seen, but the power tranny is visible from the top. It does not affect performance at all, and I hardly notice it.

I also have a 12AU7 line stage similar to the Decware ZSLA-1. This is a unity gain preamp/attenuator with a 24 position stepped attenuator. It sounds wonderful with this amplifier, and the combination is dead quiet on my current 90db speakers. I have to have my ears inside the drivers to hear any hum or hiss!

It features:

A single high quality Solen cap in the signal path. All Teflon jacketed silver plated mil-spec wire in the audio path. Regulated 6.3v DC filaments, and a very high capacitance PS filter. The power transformer (NOS Stancor) is much larger than needed and can be left on continuously if you prefer. (I always turned it off as there is no need to burn juice when I'm at work) a 1/8" solid aluminum top plate, solid Cherry front and back panels with curly maple side panels. I will include a NOS Amperex 12AU7 made by Mullard with this line stage as well as a power cord.

This Preamp runs a moddest B+ and should offer very extended life on your precious driver tubes. I would not know. I have never burned one out

Asking: $300obo

Here are a few pictures. If you are interested, I can take a few more since these turned out a little fuzzy. Also, if you want to see the figuring on the sides. My apologies.

http://img.villagephotos.com/p/2009-...Picture006.jpg

http://img.villagephotos.com/p/2009-...Picture003.jpg

Thank you for looking and as I said earlier, please feel free to ask any questions.

Blair

[deicide67]

Bump~

Addressing the PMs

*The section about Klipsch speakers is because I posted this ad on the Klipsch Forum first and just copied and pasted the whole ad. The amp uses the Baldwin 45 OPTs that many Klipsch fans supposidly like. I have had several PMs regarding this.

*The amp is about two weeks old, but played daily. I have used it on my 89db two ways and my 90db big three ways and this combo drives both very well.

*In my ad, I said I would include an old non-matching quad of 6550s. Well, as I said, it was an old quad from god only knows how old and very shortly after I posted this ad during operation, one 6550 failed to hold bias any longer. I managed to find a new quad of Sovtek 6L6GCs or WXEs in the closet, and they biased perfectly and have been holding bias being played daily since. There is really not much to go wrong with a bias supply since it is typically drawing minimal current. That being said, I'll include the new quad of 6l6WXEs and take $75 off the amplifier price to compensate for the old 6550s I was going to include.

****That is $625 shipped for this amplifier with 6L6WXEs.

***I'm pretty firm on the line stage, but several have inquired in PMs about both units as a package.


****If you purchase both units, I'll accept $800 for both shipped. That is $200 short of my original offer.

I need these out of my living room before my wife sells me instead of the gear!

Thank you!

Blair