New Trainwreck Inspired 2 channel amp

[skyboltone]

2 piece, just like a Marshall 18watt, 2 x 12 combo cab is done. Richie came up with the idea to put the Blues Breaker grill cloth on the amp and I thought it just looked too cool with the white cab and black trim. He is doing a 4x6v6 version of the amp. Kind of a Express/Rocket amp with the same front /back panels and cab. Now that I finished the first one I get to build one more.

I've got to build one for the little amp I just debuted in the tech section. It's gotta hang fender style though. I'm thinking the grill cloth will be the tan "Marshall" cane with an oval cutout. The rest black. There just isn't much room between the stuff on top of the chassis and the face.

The other Hall

[bnwitt]

Ok, I'm struggling with this layout because I don't have enough information. I have no clue what capacitance the filter caps are, I'm just guessing on the spacing of things, The power regulator board schematic and layout don't seem to match(the zener bridges legs 1 and 3 in the picture but connects leg 3 and R57 on the B+ side in the schem), I don't have much on the relay board, it's difficult to see all of the wires and connections in the photos i do have......in other words I could use some more hi-rez pictures, some more info etc etc. So, I'm going to have to put this on hold until I get it. Attached is the layout as it is.

there are just so many questions What's the rating on the bridge rectifier for the 5 volt supply, what model are the three relays, what is the value and rating of the filter cap on the 5 volt supply, what model is the zener diode on voltage regulator board, what type of led's are those for the channel indicators, what value is the pica farad cap on the phase inverter board connecting the 100k resistors, what about underboard wires, etc......A BOM would be most helpful.

Also, I am running into things that don't look right, for example, in the attached picture there is a resistor that I expect to be 68k from it's location and the schematic but it appears to be 150K.

I've also attached the beginning of the drawings for the boards.

[UR12]

Ok, I'm struggling with this layout because I don't have enough information. I have no clue what capacitance the filter caps are,

40/20/20/20@500v and 50/50@500v JJ Multicap can

I'm just guessing on the spacing of things,
there are just so many questions What's the rating on the bridge rectifier for the 5 volt supply,

Any 1 amp bridge rectifier will work. I used a 1.5 amp bridge I got at radio shack

what model are the three relays, what is the value and rating of the filter cap on the 5 volt supply,

The relays are Radio shack part #275-240 5 v spdt relays, Cap in the 5v supply is 1000uf @16v.

what model is the zener diode on voltage regulator board,

6v 1w

what type of led's are those for the channel indicators,

Doesn't really matter, Just pick the color and brightness and mounting you want. I used a red led that mounts in a chrome holder. I'll have to see if I can get a part number on the led bezels.

what value is the pica farad cap on the phase inverter board connecting the 100k resistors, what about underboard wires, etc......A BOM would be most helpful.

50pf

Also, I am running into things that don't look right, for example, in the attached picture there is a resistor that I expect to be 68k from it's location and the schematic but it appears to be 150K.

The 68k on the schematic is right. I have been substituting in different parts while tweeking and the pics were taken when I had the 150k in there.

I've also attached the beginning of the drawings for the boards.

Looking good so far.

[bnwitt]

Allright!!! Thanks for the info Dana, and the files you sent. We'll have a complete set of drawings before you know it.

[Zippy]

Allright!!! Thanks for the info Dana, and the files you sent. We'll have a complete set of drawings before you know it.

Where is the happy ending to this saga?

Anyone else develop this implementation?

What of the stability issues of the Liverpool design when in a combo cabinet?

Is anyone (besides me) curious to use this topology with an Express output section (2xEL34)?

[Zippy]

Allright!!! Thanks for the info Dana, and the files you sent. We'll have a complete set of drawings before you know it.

Where is the happy ending to this saga?

Anyone else develop this implementation?

What of the stability issues of the Liverpool design when in a combo cabinet?

Is anyone (besides me) curious to use this topology with an Express output section (2xEL34)?

[Stanz]

I have thought about a Liverpool/Express with two switchable power sections and a fixed/cathode bias switch. Since the preamps are so similar, it seemed like a worthwhile project. But this project seemed interesting also. I had not seen a schematic or layout for the Rocket/Liverpool 2 ch amp. Does anyone have a copy of these?

In the end it is the Liverpool that has my interest.

[UR12]

Allright!!! Thanks for the info Dana, and the files you sent. We'll have a complete set of drawings before you know it.

Where is the happy ending to this saga?

Anyone else develop this implementation?

What of the stability issues of the Liverpool design when in a combo cabinet?

Is anyone (besides me) curious to use this topology with an Express output section (2xEL34)?

The last few things I have done with that build was to switch everything over to fixed bias, It has a VVR installed and I wanted to use this build to test the fixed bias VVR2 setup. It worked flawlessly and I must say that I like the Liverpool with fixed bias better than the cathode bias. Just my opinion YMMV.

This was built as a head cab and not a combo. I have built a 15w version of the Liverpool in a 2 x 12 combo and have experienced no ill affects. You just need to choose your tubes carefully to make sure they aren’t microphonic and you shouldn’t have any problems. My brother Richie actually has an Express/Rocket build waiting in the wings. He was going to use 4 6V6s .

Having said all of that I do like this amp. It is very versatile.

I have thought about a Liverpool/Express with two switchable power sections and a fixed/cathode bias switch. Since the preamps are so similar, it seemed like a worthwhile project. But this project seemed interesting also. I had not seen a schematic or layout for the Rocket/Liverpool 2 ch amp. Does anyone have a copy of these?

In the end it is the Liverpool that has my interest.

I can send you a copy of the last schematic I have with the channel switching changes when I get home this evening. The schematic will still reflect the cathode bias instead of fixed bias.

[84k]

what a great idea. Very cool Dana!

[UR12]

Here is the original schematic. I have made a lot of changes since this was drawn. I may get some time to make the changes to the schematic but it won't be any time soon. Here are a few pics of that with the mechanical relays and one like it looks like today with the new mosfet switching and fixed bias.

[Stanz]

Excellent, thanks Dana. The relay switching was the main thing I was after. I am sure that VVR would be put in. I am not a huge fan of LOUD, but am a huge fan of cool tones.

If you could do one favor instead of an updated schematic, a simple list of the design changes you ended up putting in, that would be very helpful. I would probably end up keeping it close to the original design, but simply adding ideas to consider would be helpful.

[Fischerman]

Beautiful work!

[UR12]

Excellent, thanks Dana. The relay switching was the main thing I was after. I am sure that VVR would be put in. I am not a huge fan of LOUD, but am a huge fan of cool tones.

If you could do one favor instead of an updated schematic, a simple list of the design changes you ended up putting in, that would be very helpful. I would probably end up keeping it close to the original design, but simply adding ideas to consider would be helpful.

Really the only design changes were to replace the channel switching with one of the boards Allyn and I came up with for the Comet switching. It just makes for a better interface for the Mosfet switches I used to replace the relays. I also decided to go with a middle of the road tail resistor on the PI instead of switching the PI resistor between two different values. The Liverpool uses a 39k and the Rocket uses a 47k. I went with a 43k. I also changed the bias circuit (See pics of power supply board) over to fixed bias. This was done mainly to test the VVR2 board in a fixed bias amp. I didn't have a amp the had a VVR installed except for this one and I removed the cathode bias board and installed the fixed bias board after changing it over to fixed bias. So basically I used this amp as a test bed for testing my PCBs and didn't really change everything around to " fix problems" with the design. I will say that the mosfet switching is quieter than the relays but that kind of goes without saying.

Here is a pic of the completed amp[img:881:468]http://users.zoominternet.net/~jdhall/a ... 0front.JPG[/img]

[Aurora]

Fixed bias...?
The VVR2 seems to have two channels...is #2 for the bias following the HT? Any more details?

[UR12]

Fixed bias...?
The VVR2 seems to have two channels...is #2 for the bias following the HT? Any more details?

Yes, there are two versions of the VVR2. One for cathode biased amps and one for fixed biased amps. The fixed bias version has additional circuitry to track the bias with the HV so as you reduce the HV you are also reducing the bias in a linear fashion and they both track together.

The same blank PCB can be used for either configuration by populating it with the right parts.