Fender Super 60 to ODS 124

[335rat]

Hi!

I have a long time project converting a Fender Super 60 to something else. Right now it's like a Rob Robinette's Black Vibe where I used the left over preamp tube to add a cascading Dumble drive stage. All is done on the original pcb and some components are soldered on the potentiometers. It works fine and sounds good but it's a mess when I want to mod something. That's why I'm thinking of converting everything to eyelet board #124 style amp.

What makes me wonder is the Super 60's tube layout, which is like the first picutre below, and that I would like to use the original combo cabinet. This is quite compact and there's no place to move the output transformer close to the power transformer as in the standard Dumble layout.

The easiest way would be to place the main board as in the second picture below. But the problem I see with this is the long wires from the main board to the potentiometers. And also that the heater wires to the preamptubes crosses a lot of signal lines. Or is that not a problem if I make the heater wires standing up from the tubes as I've seen on some builds? On the original pcb every plate load resistor crosses the heaterline so maybe it works?

Another possibility could be to move the preamp tubes to the rear of the chassis as in the forth picture. The problem I see here is that the signal from the output tubes to output transformer comes close to the input tube, and also that the input signal crosses the OT on it's way to the first tube. As I understand it, you should avoid having input signal and output signal close to each other. Or is it not that sensitive

If none of this will work I guess I either have to design a new board with the components in the same place as the original Super 60 pcb? Or I have to give up the plan of using the combo cabinet and just build a new one with place for the original Dumble layout of the transformers?

What do you say? Thank's in advance if anyone has any advice on which way to go or or maybe has a better solution to the problem.

[romberg]

I have a fender super 60 head and have also built an ODS into a smaller non-traditional jtm45 sized chassis. So, I get where you are coming from:

https://ampgarage.com/forum/viewtopic.php?f=4&t=33427

I'm not saying you won't be able to stuff a full ODS circuit into a fender super 60 chassis. But it is gonna be very tight. The biggest hurdle as I see it, will be that the super 60 chassis is not near as tall as a jtm45 chassis. Many dumble style builds place rectifier and FET boards into the sides of the chassis in an effort to find space. Remember that you will need to not only find room for the preamp board. But also the power supply filters, rectifiers, FET board, relay power supply and the relays themselves. Also, you may have to add an additional transformer to use for the relay power supply as the super 60 PT probably does not have a spare low voltage tap to put to that use.

The super 60 transformer set does seem pretty stout and would probably work well for an ODS type build. But if I were you, I might look into getting a more traditional style chassis which would have more room.

If instead, you want a challenge then it would also be cool to try and make it all fit into the super 60 chassis. If you go that route then I'd recommend designing your own eyelet boards. I just don't think you could fit everything any other way. Then draw up everything in a CAD software package ahead of time. I spent more time drawing, measuring and planning where to fit everything than I did building the actual amp. In the end everything did fit. It was fun. But I don't think I'd repeat it

Mike

[Reeltarded]

After having recently been inside a VHT D50 for some hours.. I am not afraid of anything. The power string is all but braided to the heaters and intertwined with the early large signal wires. I unweaved the plates and cathodes. A little different, but not honestky worth the couple hours imagining it and doing it.

The depth is probably your biggest enemy as Mike said.

I build rear input amps so having the stages in front doesn't scare me. The OT vs board might be fine just by centering the board more than your drawing, or moving the OT more centered and toward the rear..

We are afraid of bad stories from all sorts of places and reasons. Maybe fiddle around for an hour with what is in there to make a super high gain set of stages and see what it acts like before worrying more. Try to make it be awful. If it still isn't, maybe take the chance with is as is.

[335rat]

Thanks for your replies and advises!

Yes you might be right that I worry too much about signal line and the heater wire. In the end the layout and placement of everything seems to work in the Super 60 anyway.

First I must say I was a little bit unclear. My amp is more of a D'Lite type amp with no FET board and no jazz/rock switch. The relay is powered from the filament's as described on the Hoffmans site and I think it works so far. I have also incorporated the IC'based effectsloop from the Super60 where I put my reverbpedal. Maybe I put a switch on the loop so I can disconnect it. My intention was to make a better amp out of the parts that's in the Super 60, which I think it is now.

I did start designing my own board but then I thought about it and just did a small board for those components that was mounted on the potentiometers. This board is rather small so I put it in front of the original pcb. Now it's easier to experiment with different values for the tonestack. Maybe I keep it this way or I see if I go on in the future and rebuild the whole amplifier. Then I think as you say the best way is to design my own boards.

Romberg , that was a complex build and I understand if you don't want to do it again.

Here's how the amp looks today:

Super60ODS_20221114_091110.jpg

Super60ODS_20221114_091336.jpg

And just as an example, here is my first attempt to do an eyelet board around the input valves. But I think I should do it in another way today. Not checked yet so I'm not shure if its correct.

Super60 to ods AN_1cut.png

[335rat]

After a long time with no progression I've now made a layout for my Fender Super60 amp. It's based on the #124 schematic but with no FET-board and no rock/jazz switch. I also did the layout for tradiotional Fender tone control but with a 100k mid pot so I can get a bit of the PAB sound and try the D-style later.
Because the distance between the preamptubes are fixed by the holes in the chassi maybe it's a littel bit crowded and tight between V1 and V2? But I probably go with the Malory caps I already have and they will fit. On the other hand the layout dont't need the long wires going to and from the tubes as in the more tradiotional layouts, which I hope is a good thing. I will cut out holes in the board for the tubes as I've seen in some builds of the SSS.

The relay will be on a separate small board and is just scetched out here. The power for it I plan to take from the heaterwires as I did in my previous version. The power supply is based on the Super60 and so are the bias and heaterwiring. I also have to adjust the dropping resistors in the powersupply and study a little bit more how the primaryside of the transformer is connected.

I will try to put the OD-trim VR3 on the underside of the chassi or maybe at the back of it so I easily can adjust it if I want to.

Maybe I will move the choke to the underside of the chassi and place the rectifierboards on the side as it use to be in most builds. Or is it better to leave it where it is? I`ll probably do a pcb for the rectifiers

In som places I think it shuold be possible to mount one part of the component directly to the tubesocket, for example the 220k/500pf on V1. But maybe it’s better to not do that if I want to change something later?

I hope I've done every thing rigtht now but everytime I go back and check there's always something to adjust or correct.

Are there anyone who have time to give an option on this? What do you think, is it a good solution and do you maybe see something in the layout that is not so good and should be improved?

Thanks in advance!

[335rat]

So now it’s finally up an running! It started without any problem at first time and sounds wonderful with no hiss or hum so far. I have done some edits to my previous layout and there are still some values to tweek, but right now I just think I play it and learn how it feels. As I wrote in my earlier post, I went with the Malory caps I already had but will see if I change them to orange drops later. The resistors in the signal path are Xicon cf 1w and Beyschlag mf 0,6 w. The NF switch on V1 is not yet connected.

The power transformer gives 463 V at B1+ and I have 197 V at V1 pin 6. What do that higher B1+ voltage to the power stage do to the tone compared to the more comon 440V? Is there any audible difference?

Here’s my layout and some pictures. And thanks to all the members of this forum for all the information you have shared here.

[martin manning]

Looks great! The higher B+ is no problem, but you might want to try increasing the 2k7 first dropping resistor to knock 10-15 volts off of the V1 plates.

[romberg]

Very nicely done! I'll be honest, I did not expect that you would actually do this. How wrong I was .

It is now a real sleeper. I really like amps that veer hard away from a clone look while still using the same circuit. To me the circuit is where all the magic happens anyway.

She looks great. And your boards look so much better than that horrid stock fender one. I invented many new swear words while re-capping my super 60. It is now sitting over there on the shelf looking nervous as my eyes switch between it and they pictures of yours...

Love to hear some sound clips,

Mike

[martin manning]

Another thing you might try is moving the GNFB lead to the 8-ohm tap, or reducing the FB resistor to 3k3 (from 4k7) to adjust the FB for your 50W output.

[ijedouglas]

To me the circuit is where all the magic happens anyway.

Mike, I'd have to disagree with you on this. While the circuit is certainly important, there is so much more that goes into these amps. Component location, chassis material, lead dress to name but a few. HAD was asked in an interview whether he could "Dumble-ize" a Fender and his response was "It's a compromise" and "They're just a little bit too squashed. A distance of half a centimeter makes a big difference in the way something sounds. It's a science involved with what's called circuit constants."

I'm sure you could build a great sounding amp into a Fender chassis but I doubt it would come close to the sound of a Dumble. I'd love to be wrong

[335rat]

Thank you Martin! I will try to lower the V1 plates as you suggest and also change the GNFB to 8 ohms. Will it be the same even if I install a jack for extension speaker?

Thank you Romberg! Yes it took a while to do it, but now it's done As you wrote a year ago it was the planning and adjusting the layout that took most of the time. And because this was my first amp build, I tried to be extra careful. There have also been long periods when I didn't do anyting with it at all.

I think this is probably the closest to a Dumble I ever will be and don't think I ever will get the chance to play a real one. So if this sounds god to me I'm satisfied right now, and now I hopefully can tweak it to my taste.

[martin manning]

...and also change the GNFB to 8 ohms. Will it be the same even if I install a jack for extension speaker?

Yes, it's the voltage from the 8-ohm tap you want, which will match the voltage from the 4-ohm tap on a 100W amp.

[335rat]

Thank you! I have changed that now.