New Project: 6U8/6V6 amp

[tunghaichuan***]

I got a start on my newest project: a single ended amp using a 6U8 triode/pentode for the preamp tube and a single ended 6V6 for the output.

Here are some pix.

The amp uses a 6U8 triode/pentode for the preamp. The pentode section is the input tube; the triode drives the 6V6. I have quite a few NOS 6U8 tubes as well as 6GH8 and 6BL8, which have the same pinout but slightly different ratings.

The output is based on the tweed Princeton/Champ. I decided to use JJ 6V6S tubes as I got a batch with the skinny pins. The ceramic tube sockets I got a while back grip the pins very tightly, which is good because the JJ 6V6S tubes are loose in the NOS sockets I have

One interesting thing about this circuit is that it has a built in compression control. More on that later.

I also plan on installing the VVR circuit using this layout. The VVR is a type of power scaling which uses a MosFet to control the anode voltages, and thereby reduce the ouput wattage. I've been wanting to try this for a while because it is supposed to give good OD sounds at whisper-quiet volumes. We'll see. The one bummer about using the VVR is that the MosFet costs about $12US. It really pains me to pay that much for a solid state device.

So far I've generated the schematic and the board layout. Next up is building the board, and then generating a chassis layout.

I've been wanting to do this project because eventually I want to build a push pull version of this amp using the 6U8, a 12AX7 phase inverter and a pair of 6V6 tubes. Maybe even a tube rectifier.

Stay tuned...

tung

[duhvoodooman***]

Cool! Waiting to see (and hear!!) how this one turns out! :

[tunghaichuan***]

Got the circuit board built this morning. As usual, I made a master drilling board so all I have to do is cut the blank to length and put the master on top and trace out the holes. I then drill the board using a layout guide and a fence on my drill press so all the holes line up evenly. Next, installed the eyelets.

Next step is to drill the chassis. Since this is a prototype, I'm not going to spring for face plates. There will only be four knobs on it anyway: compression, volume, tone on the front and a VVR level on the back.

Some pix:

Drilling pattern taped on master and blank board. The bag to the right is full of 1/8" eyelets, approximately 1,000.

Closeup of pattern taped on master board and blank board.

Drilled out blank board, master and extra pattern.

Finished board.

tung

[tunghaichuan***]

Got the chassis done yesterday.

Blank Bud AC-409 chassis It's even RoHS.

Chassis with blank circuit board

Chassis clamped to bench

Control panel holes drilled out

Finished chassis

Front of finished chassis

Board mounted in chassis

Parts mounted on chassis

Board stuffed with parts, not soldered yet

So far this is shaping up nicely. The next step is to solder the flying leads to the board and mount into the chassis. After that, I can begin to wire the circuit.

More later.

tung

[piebaldpython***]

I gotta tell ya Tung, I am totally in awe; : : : ; of what you and DVM do with your skills in making amps, pedals, etc.

OMG, I would be ready for the loony bin for sure.

[duhvoodooman***]

Comin' along nicely there, Tung! :

I gotta tell ya Tung, I am totally in awe; : : : ; of what you and DVM do with your skills in making amps, pedals, etc.

Don't be so impressed, Pie. If Tung and I can handle this stuff, how hard can it be??