One of the early products of my tube amp experiments. Today I really wound not recommend using a pair of
almost new RE134's for such a project. But the amp worked and sounded really fine but was dismanted after one year
of service after one tube broke. One of these is standing on my desk and is waiting for service in an upcoming
This was ( maybe still is ) a EL84 push-pull guitar amp that was made from parts from an old Tesla
tape recorder and from an Telefunken radiogram. Only some resistors and caps were bought.
I used this amp occasionally and carried it through half Germany during a school trip. During this trip
the amp was bounced around all the time and water ran over the chassis when our radiator broke during one night.
Some month later I sold it to someone and tried to send it via German parcel service. When the amp arrived, the chassis
had left its place and literally trashed everything into pieces including the output transformer HV-winding.
I traveled to the amp during one holiday and rebuild it with only the parts that had survived and it worked again.
Two years later I heard from the guy who bought the amp and he stated that he still regulary used this amp
with his band. This is some 8 years ago and I wonder what became out of this amp....
Here you can see a 845 power triode amp I started in 1994. At this time I was still visiting school and was
like most people of that age regulary out of money. So this project developed in very small steps over the years.
The picture shows the amp 2 years ago with a EL32 compatible tube in the driver stage. In the now almost
finished version there is a 6SN7GTB in the driver stage. The amp has 2 ( stereo ) inputs and internally mixes the two
channels. It is designed to be used with a subwoofer to support my 2A3 stereo amp.
This picture shows the internal wiring of the 845 triode amp during development. Some parts have moved since then but the
basic layout is the same.
Note the giant base for the 845...
The power supply for the 845 employs 3 transformers for 4 different voltages and 1 switching power supply. Output is 1000V=( anode HT for the 845 ), 310V=( U+ for the preamp and driver stages ), 145V= ( bias for 845 ), 6V AC ( preamp and driver filament ) and the 10V DC for the direct filament of the 845.
The case of the whole power supply has only venting holes, no external switches or indicator lamps. The supply is activated
by means of a reed-switch and a magnet that can be seen in front of the first transformer.
I recently picked the the finally running amp from the shelf again and gave it a try.
This is a somewhat illfated project as the amp is only mono as I intended to use it on an additional subwoofer, which
did not work out too well because of the low grade of damping triode amps show to external loads.
To use it as a normal amp I would need to build a second one which is currently not in sight.
However, this picture at least shows it working, the glow of the 845 is realy far beyond anything you see
from tubes like an EL34. Amlmost brighter than desired.
As I only can hear it mono I can not say too much about the sound of this amp. At least it is very clean
and the output is bigger that I can test in my flat with speakers. No power tests with dummy load were done,
maybe another time but who cares for figurest anyway if the loudness is sufficient ....
I would not say it sounds spectacular, I like the 2A3 much better.
This is my everyday amp. It's a 2A3 triode with ECC83 tubes in the driver stage. I built this amp almost 12 years ago,
and aside from one cap failure which was very spectacular I never had any serious problems.
The one tube is still
the original and the other was changed some years ago. Although this is against anything those HiFi-nuts believe in, I can
assure you the amp still sounds pretty good. The power supply for this amp is a rewound welding transformer which
( in original configuration ) can deliver 3KVA. I feel this is sufficient for two channels with 3Watt RMS out... ;-)
While taking some pics this little 6V6GT amp came into my mind. While this is not the very first amp I ever built,
it is the first one which included such a usefull feature as a casing, the one or two projects before
were simply thrown together on my workbench.
The amp was intended to be a guitar amp as I was starting to play electric guitar at tat time.
Later I found out that my way of playing is not the way that should be amplified at all ;-)
To be honest, this amp sounds like crap, don't ask me why, but playing guitar on your PC-speakers would
probably sound better. Maybe its the output transformer which originaly came from a radio which is
most probaly not designed for the great overdrive experience... at least not willingly.
The good thing is the integrated tremolo using an ECC85, at least a good use for this otherwise worthless tube.