Printer2:
Thats an interresting project!
Can you tell more about the DC booster? Is that an DC-DC converter? Doesn`t those make a lot of noise for audio?
Do you have the full schematics?
Booster is the 45-390V one sold everywhere. I found it to be quiet, I use a 10k and 500 pF cap on the input rather than a 33k. One nice thing is no hum whatsoever. Just a Champ type circuit with 100k/1.5k resistors on each triode and 10uF bypass on them. 470R on the output tube with 22uF. Power supply has a 1k for the screen supply and 10k to the triodes, 10uF caps. Nothing unusual. The only different thing is the tone stack. I doubt I would do the switchable responses for it and just stick to the BF response. It works better for the small cabinet.
The HV module does not like putting out a lot of watts when fed by 12V, it will do 15W with 12V. Above that and the rectifier diode gets hot and blows. This is with free air, in a chassis with the tubes heating it up you would have to derate it. I did use a Russian 6N3C on my breadboard and it managed 300V@55mA but eventually it blew the diode. With a a 6V6 in, 350V, 40mA -16V, 14W out of the module I ran it all night. With a fan on it I had it put out 30W
I soldered some foil to the rectifier and 20W out of it. I did paint it black though.
When the diode heats up the turn off time gets longer and more power is dissipated across the diode blowing it. Managed with a 6V6 in SE, 360V 55 mA. Going up to 16V feeding it gave 390V, 104 mA, 41W although I can not remember what heat sink I had on the Mosfet. Rather than the foil I used copper pennies on the diode.
I do have an over sized heat sink on the mosfet in the amp but it barely gets warm. It was already mounted on the module and I left it there. It is a pain changing the heat sink as you have to unsolder a cap on the board in order to use a screwdriver on the heat sink screw. I will be using the module in a P-P amp but using a 19V laptop supply instead, which should solve the heating problem. I used a 12V6 for the output tube ($8 for NOS!) but on 19V I will be using a step down converter. I tested three normally available and two of them have their switching frequency
Starting with the bottom one in the picture. Should be ok charging batteries as long as you do not want current limiting. 250 mV ripple at 12.6V (all measured at 12.6V) and a speedy 16.7 kHz. But it does have mounting holes. The three trimmer one in the middle runs at 72 kHz. Wonder if my high voltage module running at close to the same frequency will cause any problems? Another concern is its 0.5V ripple. One ray of sunshine, as you reduce the voltage out the ripple reduces somewhat the same amount. These ones use a LM2596 which are knockoffs that should be avoided. The top one fairs a little better. It has 180 mV ripple, best so far. Now the biggie, running at 200 kHz, it uses a XL4015 and the chip may actually match the datasheet specs, the LM2596's do not and are to be avoided.
That is about as far as I got with these modules. Originally I wanted to figure out an inexpensive way for a person to make their first 5F1 without an expensive power transformer and a 12V6. Shame about the heating problem at 12V. A 6K6 as the output tube would be a nifty project and should work with the HV module without any modifications. Would be 4W as compared to 6W output with a 6V6.
A little involved post, tried condensing what I found developing this project. Will be adding a Digilog reverb to it yet.
Topic: Champ-ish "pocket"-amp (Read 3008 times)