Into the rabbit hole...36 Watt EL34 Superlite TMB

[JMPGuitars]

Did you go with the 36 watt GDS transformer set on these amps or another make?

Yes, along with a GDS JTM chassis that I retrofitted for this build.

Cheers!

Post some photos, that sounds cool.

[ViperDoc]

I'm sure that's an awesome chassis. I modded a Valvestorm 18-watt chassis for my Superlite build and it was a killer deal.

https://valvestorm.com/Products/MetroAmp

[Billy_Goat]

Your voltages look great! I'm looking forward to hearing a sample of your amp.

Post some photos of your FX loop from a couple different angles so we can see what's going on. The solution could be as simple as chopsticking the leads to avoid the oscillation.

Thanks,
Josh

FX circuit issue resolved!!!

After careful reanalysis and studying of the schematic, it became clear that I had miss wired the jacks. D’oh!

After a quick re-wire and testing, all is well. Yay!!! Effects are clean and as clear as a bell.

I do have an unrelated question about the schematic vs the build doc... The schematic shows the pilot light being fed power from the 6.3v heater secondaries, where the build doc shows the pilot lamp being fed using the 5v secondary. I’m guessing either way works without any issues, but curious if this just an over sight between the two documents or just an inconsequential second path option? I ended up wiring my pilot using the 5v secondary in hopes of extending the life of the pilot lamp with a little less voltage.

As for the chassis, I retro fitted an already in hand combo cabinet and speaker setup that is loaded with a Reeves Vintage Purple 12”speaker. This is supposedly a close recreation of early 1970’s era Fane speakers. This speaker sounds very nice. Very punchy and ballsy with a nice bottom end thump. I alternatively tried a Scumback 65W M75-PVC that also sounded ok, but was a bit more ‘fizzy’ and not quite as punchy. The Scumback sounds amazing in my 18W build, though. Curious to know what speakers other folks with 36W builds are choosing?

As for sound clips, not sure how to make that happen atm as my shelter-in-place COVID home is many miles away from my recording and other studio gear and not easily accessible for now. Not sure that a recording using a phone would be the best means of showing off the build.

Anyway... pictures will follow as it’s now a bit too dark here now to take good photos.

Cheers!

[JMPGuitars]

Well done!

The pilot thing was basically laziness. It doesn't really matter where you connect it between the two choices, but the unused rectifier heater tap is kinda better since it's not doing anything else.

My favorite speaker right now is the WGS BlackHawk (50W). Sounds great on 18W and 36W builds.

Thanks,
Josh

[ViperDoc]

If you feel the urge, the Fane A60/F70 combo is absolute dynamite when broken in with the Superlite TMB. OMG.

[JMPGuitars]

If you feel the urge, the Fane A60/F70 combo is absolute dynamite when broken in with the Superlite TMB. OMG.

Post a demo. I wanna hear them!

[Billy_Goat]

Picture of the internal wiring...

[Billy_Goat]

Control panel... a retro fit into an already in hand cabinet...

[JMPGuitars]

Very nice! Overall it looks like some really nice, clean work. I can't wait to hear it.

[ViperDoc]

Picture of the internal wiring...

WHITE LOOP JACKS. (searching the internet...)

[TriodeLuvr]

Picture of the internal wiring...

WHITE LOOP JACKS. (searching the internet...)

That's a really clean build! I think AES has the white Cliff jacks.

Jack

[Billy_Goat]

Picture of the internal wiring...

WHITE LOOP JACKS. (searching the internet...)

1/4" Jack - Cliff, White, Solder Lug
https://www.amplifiedparts.com/products ... solder-lug

[JMPGuitars]

CLIFF also makes different color nuts for those jacks. I know newark.com can get them, I assume some other suppliers as well.

[ViperDoc]

Thanks for the link. I wonder if they make a white vintage version with the metal ferrule, but with a white bezel. I prefer those jacks to the plastic nuts. I seem to strip those too easily.

EDIT: Well what do you know?

https://www.newark.com/cliff-electronic ... Connectors

[Billy_Goat]

After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?

[JMPGuitars]

After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?

It sounds like you have an oscillation problem. You can try chopsticking the wires to get rid of the effect, or use shielded wire and see if that helps. Post some photos of the FX loop and surrounding area.

Thanks,
Josh

[Billy_Goat]

After a fair bit of playing and fussing with effects in the FX loop, it appears that the FX loop on my build is exhibiting a bit of comb filtering and / or phasing shifting that is manifesting as a slight unpleasant ‘hollow’ sound overall compared to when I play without using the FX loop. Not sure how to further confirm this and / or how I would go about trying to rectify if in fact more than just my impression? Any thoughts?

It sounds like you have an oscillation problem. You can try chop-sticking the wires to get rid of the effect, or use shielded wire and see if that helps. Post some photos of the FX loop and surrounding area.

Thanks,
Josh

Hey Josh,

Please see attached photo. If not clear, I'll shoot another.

Not much to chopstick that I can see here based on my build. The two connections to the terminal are shielded and these two shielded connections are not more than an inch or two in length. The rest are soldered as tightly as possible to a 4 lug terminal. The terminal is lifted up from the chassis to the approximate level of the jack terminals with a 1" standoff.

I haven't had a chance to do so yet and also not sure if this would be a proper test setup, but I'm thinking that I feed a white noise signal into the amp input and connect ch. 1 of my oscilloscope to that input signal so I can monitor the input signal. Then connect a guitar cable between the two FX jacks and connect ch. 2 of my oscilloscope to the output to see if I can see any comb or phasing issues between the two traces on the oscilloscope. If ok here, then add some pedals into the FX loop to see if there's something going on there. Basically, I'm looking for a way to confirm empirically that what I'm hearing is actually happening. Would there be a better means of confirming something like this?

As mentioned previously, outside of this FX issue, the amp sounds big, strong and amazing. It is overall quiet - no background ground noise, buzzing or other operational artifacts.

Cheers,
Greg

[TriodeLuvr]

Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?

[JMPGuitars]

Your tag board appears to me that it is essentially allowing your loop circuit to run parallel to long plate wires running next to it.

Take a look how I implement the FX loop: viewtopic.php?p=247480#p247480

I keep all parts (except the 68K which I place directly on the circuit board) running in simple lines, which helps avoid issues like parallel plate wires that you currently have. It may not be the source of the problem, but from the photo, it appears to be the most likely cause.

Changing to the method I use will eliminate that issue and help you see if it's the cause. I don't use any extra wires, the leads from the components are all I you really need. I leave just enough slack to chopstick if needed.

Thanks,
Josh

[Billy_Goat]

Is it wired like this? What's to keep the loop return signal from mixing (potentially out of phase) with the dry signal from the 68K resistor?

Hi TriodeLuvr,

Yes, 68K resistor was in place as required. Thanks!

Your tag board appears to me that it is essentially allowing your loop circuit to run parallel to long plate wires running next to it.

Take a look how I implement the FX loop: viewtopic.php?p=247480#p247480

I keep all parts (except the 68K which I place directly on the circuit board) running in simple lines, which helps avoid issues like parallel plate wires that you currently have. It may not be the source of the problem, but from the photo, it appears to be the most likely cause.

Changing to the method I use will eliminate that issue and help you see if it's the cause. I don't use any extra wires, the leads from the components are all I you really need. I leave just enough slack to chopstick if needed.

Thanks,
Josh

Hey Josh,

Ok, I rebuilt my FX connections.

With all due respect, I'm not a fan of wiring components without providing solid mechanical attachment for the same which your photo appears to indicate, so I built a little turret board where the two caps connect directly to the jacks and the two 'in series' resistors from the caps are attached to turrets. Then shielded wire from there to the main turret board and the last 68K resistor placed on the main turret board. I also added some foil shielding underneath the FX turret board and grounded that. The new turret is also now 1.5 inches above the plate wires lying on the chassis. All components and wiring is now more or less 90 degrees away from the plate wiring lying against the chassis. Nothing parallel.

It seems better upon first check, but admittedly I only had a few mins to play and analyze. So, the jury is still out atm.

If it's determine that this rebuild is still not working properly, I'll reluctantly try wiring as your photos suggests.

Cheers