Tweed Super Build

Cjsinla

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I believe that the board is ready to drop in, that’s when I solder in the choke and the power supply for the bias.

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tokairic

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If I were building this on a blank chassis I would be tempted to move the transformers further apart and orientate them at 90deg to each other to help stop hum and interference from local magnetic fields around the transformers.

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CB91710

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The power and output transformers are on a different plane.
I'm not sure how much impact the choke has on the output transformer (or the PT on the choke).
Like the power input section, this basic design has been in use since the 40s.
 

Cjsinla

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The first Super I built is basically set up with the transformers in the same orientation and it’s pretty quiet.
 

tokairic

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The power and output transformers are on a different plane.
I'm not sure how much impact the choke has on the output transformer (or the PT on the choke).
Like the power input section, this basic design has been in use since the 40s.
It may be fine on this simple amp, but just because it was ok in the 40's doesn't mean it can't be improved on. I built a Fender Princeton clone to the original circuit diagram and it was fine, with negligible noise/hum. However I have also build a Trinity amp with the transformers at opposite ends of the chassis which is absolutely silent.
It may depend on how much you value originality over improvement however small.
 

Cjsinla

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Just have to screw the board down to the chassis and I can start making all the connections. I’m planning to wire the heaters last. We’ll see how that works out. I have to get a couple of sheet metal screws. These kits never supply those.

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Cjsinla

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I just realized that the NFB is done differently on this amp than on the Marshall 2204. The 2204 connects to the 4ohm tap and uses a 100k resistor. The Super connects to the 4ohm tap but uses a 56k resistor. What’s the difference?
 

CB91710

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Lower resistance provides more negative feedback to the grids of the output, reduces the gain (and cleans up) the output section.
Add a 100k pot in series with the resistor and experiment until you get a tone you like, then measure the pot+56k resistor and sub in a resistor of the same value.... Or keep the pot and add a knob to the bottom of the chassis.
 

Cjsinla

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Finally got some time to resume work. Finished making connections to the tube sockets and the board, I’ll wire the heaters and pots next.

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Cjsinla

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Finally got off my butt, did some more work wiring the pots and jacks. Also added tube retainers. Just need to wire the heaters and the output jack and I’m ready for testing.

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Soul Tramp

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Looks great. I know how slow going it can be.

Work on getting the heater wires twisted tighter. Also, keep the leads as short as possible by removing the loops on the yellow wires. The longer the lead the more prone it will be to noise, especially with the terrible old tweed ground schema.
 

CB91710

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Still really jonesing for a build.
Just can't make up my mind between a 5E3, 5F2A (both of which are really too loud, but everyone needs a real Tweed) and a Studio One.
 

Cjsinla

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Finally got off my butt and finished the wiring today. I have to take my time and savor theses projects as my house is filling up with amps.

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I did plug it in to my light bulb limiter to check a few things. The heater wiring appears to be intact. I put in the rectifier tube and checked the B+ voltage, it was about 385 vdc all the way across the board. Tomorrow I’ll do some more tests with the power and pre-amp tubes installed.
 

Cjsinla

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Finally finished the whole thing, Sounds great, much more clean overhead than the Weber kit. This one is stock Mojotone with Weber speakers and a MM OT. I need to do some checking, the slope on the pots is completely different. The Weber kit stays pretty clean up to about 2, the Mojotone kit stays really clean until 7 or 9 with a pretty big jump in volume at about 10. It gets flubby at 12. Don’t worry, I will be shortening the speaker wires.

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ErictheRed

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Looks great, good work! And speaker wire length is no big deal outside of appearances, so no worries if you wait a while to do that.
 

The Ballzz

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@Cjsinla

Fantastic Job! :dude: As far as the speaker wires, I would keep them long enough, and in a neat manner for ease of access to an attenuator. Of course, the attenuators I use are inexpensive and small enough to mount in the cabinet!

HNAD!
Gene
 

Case24

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Great job! Always so satisfying to build your own amp.
 

Cjsinla

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This amp is so quiet that I thought that it was broken when I first turned it on without a cable in the input.
 




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