Serial Tone Killer

[lhwarp]

Hello All !

Well... I started this project/prototype in december 2015 (design) and I'm trying (and hoping ) to finish it these days, where I have momentarily some time to do it...






Only the biggest is under finishing for the moment :






I still have to debug a (well hidden - probably grounding ) hum issue in the reverb/FXloop... That's why I'm late...

-lhwarp

[Jaguar018]

Look cool to me. These all for you?

[lhwarp]

Look cool to me. These all for you?

Thanks Jaguar018 !

The small one with stripes is for an amateur luthier friend. It's a more classic circuit design, though. I'll start the building soon...




-lhwarp

[Shadoweclipse13]

Lovely amp!! I also love your EHX Holy Grail. Is the effects loop internal?

[lhwarp]

Lovely amp!! I also love your EHX Holy Grail. Is the effects loop internal?

Thanks Shadoweclipse13 !

Yes, the FX loop is internal, set at stompbox level (-10dBm), and is footsichable, as are the EHX reverb, the booster, the clean/OD channels.



-tbln

[somanytoys]

That’s beautiful work, they look great.

They remind me a little of the red/cream version of two blue/cream Vox amps that I have. Those are really pretty.

Nice work on the electronics as well. Brilliant use of a pedal for reverb.

Thanks for sharing those.

[Shadoweclipse13]

Lovely amp!! I also love your EHX Holy Grail. Is the effects loop internal?

Thanks Shadoweclipse13 !

Yes, the FX loop is internal, set at stompbox level (-10dBm), and is footsichable, as are the EHX reverb, the booster, the clean/OD channels.



-tbln

I said that jokingly, but that's actually really cool!

[mbene085]

That's one of the more unique and interesting designs I've ever seen - an internal reverb pedal instead of a tank!

Now I'm imagining an amp with an internal pedalboard - maybe a closed back cab with a portion that flips open - and control of effect 1/2/3 integrated with the channel switch and Reverb on a footswitch. Lets you change things around at will, transport a modest sized pedalboard easily, and control everything with one compact footswitch!

[lhwarp]

Lovely amp!! I also love your EHX Holy Grail. Is the effects loop internal?

Thanks Shadoweclipse13 !

Yes, the FX loop is internal, set at stompbox level (-10dBm), and is footsichable, as are the EHX reverb, the booster, the clean/OD channels.



-tbln

I said that jokingly, but that's actually really cool!

That's one of the more unique and interesting designs I've ever seen - an internal reverb pedal instead of a tank!

Now I'm imagining an amp with an internal pedalboard - maybe a closed back cab with a portion that flips open - and control of effect 1/2/3 integrated with the channel switch and Reverb on a footswitch. Lets you change things around at will, transport a modest sized pedalboard easily, and control everything with one compact footswitch!

That’s beautiful work, they look great.

They remind me a little of the red/cream version of two blue/cream Vox amps that I have. Those are really pretty.

Nice work on the electronics as well. Brilliant use of a pedal for reverb.

Thanks for sharing those.

Thank you Guys !

Well, I'm still fighting the reverb hum... But I'm making good scores in that field ! Patience...

Reverb and connections displacement tests :


First conclusion and attempt : shortening the connections... Great improvement, but not perfect, and I want zero hum !


Wait and See !

[mijmog]

Holy Grail inside the amp, that is crazy - I love it! Genius.

[fuzzjunkie]

Could the pedal case be causing the hum issue?

Acting as an antenna or

In any case I would just use the circuit board and ditch the box and switch, mount a switch and the controls on the panel.

[carron]

If the pedal is causing the hum, you can try to make sure the box is grounded so that it can act as a Faraday Cage and block the source of noise. If the noise is from the transformer hum being picked up by the pedal, same thing. So I would keep the box, with the back lid installed, and check its ground.

Otherwise, disregard this comment.

Amazing build!.

[lhwarp]

Holy Grail inside the amp, that is crazy - I love it! Genius.

Thanks @mijmog !

I did this on several of my DIY amps : no hum issue and grat tone...

Could the pedal case be causing the hum issue?

Acting as an antenna or

In any case I would just use the circuit board and ditch the box and switch, mount a switch and the controls on the panel.

No, @fuzzjunkie, what you suggest makes sense, but you guess that I checked that : the casing is fully grounded and acts as a Faraday cage. But not against magnetic induction...

If the pedal is causing the hum, you can try to make sure the box is grounded so that it can act as a Faraday Cage and block the source of noise. If the noise is from the transformer hum being picked up by the pedal, same thing. So I would keep the box, with the back lid installed, and check its ground.

Otherwise, disregard this comment.

Amazing build!.

Thanks @carron !

Yes, It's what I checked for sure and it's a good Faraday cage.

But this is inefficient against magnetic radiated hum : in no way aluminium blocks magnetic radiations due to the transformer core, like usual non-ferrous metals... Here, my chassis is aluminium and the HGN case is too (or maybe an alu alloy like Zamak).

I would need µmetal, very costy high permeability steel, and painful to worh with.

Soft iron would be a possible (much) downgraded substitution, though, if I completely encase the toroidal transformer, but I'm not sure that it would be rewarding for the related work, complication and drawback...

To corroborate this, I made a transformer displacement test - quite conclusive :



I wonder if, finally, a classic EI transformer wouldn't be better, since its radiation is core-orientated and not omnidirectional like on the toroidal Xfos... I can find an EI power transformer that would allow me an extra feature "HI power - Fixed Bias / LO power - Cathode bias" thanks to its plate voltage coil tap.

But the drawback is an increase of +3kg weight ! I wanted this amp to stay lightweight...

I'm somewhat puzzled...

Wait and See !

-lhwarp

[carron]

Great detective work!

Yes, aluminum is not the best, and mumetal is expensive. Perhaps you can try to cover some of the aluminum enclosures in copper tape to see if that helps. Though two types of metal together are a recipe for corrotion.

In principle a toroidal transformer should minimize the leakage of magnetic flux, so I would have thought it should have minimizde hum relative to a classic transformer design.

It is true that the radiation has a "more" omnidirectional structure than a classic transformer, where it is even more concentrated in one direction. Nevertheless the radiation of a toroidal transformer is not perfectly omnidirectional. It should be larger along the axis perpendicular to the toroid "circle", because the inner side of the coil and farther side are at different distances to the center and the effect does not perfectly cancel out, and the effect sums from every direction along the center symmetry axis. Perhaps there is something just directly below that transformer, along that axis that is acting as an antenna and picking that noise. Have you tried turning the Toroid 90 degrees on its side, to see if anything changes?

Reducing hum is a difficult art for any expert designing circuits, and I am no expert by any stretch of the imagination.

Again, amazing build.

[carron]

Ahh, magnetic fields... I take it back. because of the right hand rule the magnetic field along the center line from coils on opposite sides at the same distances cancel out... so take everything I said in the previous post and make it the opposite. The radiation should be lower along the symmetry axis.

Anyway, turning the toroid 90 degrees and then rotating it could help you diagnose where the hum is being picked up.

Good luck.