Hi all:
It is up and runing, so I thought I would share this project with you all.
It is a single-ended KT88 in Triode mode, with a 6DJ8 SRPP driver stage, James OPTs and a HUGE power supply made from trafo and chokes rescued from some very classy radio equipment.
The whole thing is built on an open-frame chassis made from 1/2-inch (yes, thats 13mm) aluminium plate. All up it weighs about 55lbs.
Construction is very straightforward. However the power supply is a bit wierd. The Trafo outputs 375-0-375. Since I did not have room on the chassis for a rectifier tube, and SS rect. brings the voltage up so high that I would not have been able to use reasonable value caps, (plus, I had 2 chokes) I decided to split the output of the trafo into 2 seperate half-wave supplies.
The result is a seperate supply for each channel, which share a trafo secondary. So an almost doal-mono design
Some more photos:
Just starting construction
Things well along
Nearly done
first power-up = measuring voltages and waiting for smoke
In the room and making tunes - mighty good-sounding, if not overly powerful.
and the schematic
It is up and runing, so I thought I would share this project with you all.
An externally hosted image should be here but it was not working when we last tested it.
It is a single-ended KT88 in Triode mode, with a 6DJ8 SRPP driver stage, James OPTs and a HUGE power supply made from trafo and chokes rescued from some very classy radio equipment.
The whole thing is built on an open-frame chassis made from 1/2-inch (yes, thats 13mm) aluminium plate. All up it weighs about 55lbs.
Construction is very straightforward. However the power supply is a bit wierd. The Trafo outputs 375-0-375. Since I did not have room on the chassis for a rectifier tube, and SS rect. brings the voltage up so high that I would not have been able to use reasonable value caps, (plus, I had 2 chokes) I decided to split the output of the trafo into 2 seperate half-wave supplies.
The result is a seperate supply for each channel, which share a trafo secondary. So an almost doal-mono design
Some more photos:
An externally hosted image should be here but it was not working when we last tested it.
Just starting construction
An externally hosted image should be here but it was not working when we last tested it.
Things well along
An externally hosted image should be here but it was not working when we last tested it.
Nearly done
An externally hosted image should be here but it was not working when we last tested it.
first power-up = measuring voltages and waiting for smoke
An externally hosted image should be here but it was not working when we last tested it.
In the room and making tunes - mighty good-sounding, if not overly powerful.
and the schematic
An externally hosted image should be here but it was not working when we last tested it.
The holes were all drilled. The square holes that mount the trafo and chokes were drilled at the corners, then cut with a jigsaw, then filed smooth. Very time consuming and rather mad, really.
However, the chassis is nothing if not solid
They most certainly are Dave's enABleD FE127s.
BTW: Thanks very much, gmilitano, for the KT-88 SE you published on your site. It is the source for the KT-88 section of this amp.
However, the chassis is nothing if not solid
They most certainly are Dave's enABleD FE127s.
BTW: Thanks very much, gmilitano, for the KT-88 SE you published on your site. It is the source for the KT-88 section of this amp.
JesseG said:BTW: Thanks very much, gmilitano, for the KT-88 SE you published on your site. It is the source for the KT-88 section of this amp.
Actually, that is Mikael Abdellah's Single Ended KT88 Tube Amplifier.
Here is Alex's Single Ended (SE) KT88 Tube Amplifier with a beefed up supply.
Cheers,
Gio
Good eyes
I left off the cathode bypass for two reasons - 1) because I wanted to get a good idea of the effect on the sound with and without a cathode cap. and 2) because the schematic calls for a 220uf cap - I don't have any 220uf of any kind of quality right noiw and the idea of putting a cheap electryolytic in there just makes me cringe.
Right now, the amp sounds fantastic. When I can get some 220uF Black Gates (or similar) the I will try them.
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