Steel String Singer #002 Build - Noise Problem

[Galef]

Hello everyone, this is my first post but I've been reading the forum a lot since i bought the SSS Chassis and PCB's from Erwin.

I completed my SSS Build last year incl. scope PI-Balance etc.
The amp sounds amazing and i really like him but i have one problem, i got some noise/buzzing. The noise goes completely away if i remove the V1 Tube, i already tested different Tubes in V1 but no change. The noise is way quieter than my amplified guitar signal but i think this isn't normal.

The Layout & Schematic are from here/Ryan.

-the noises gets louder with the preamp Volume/Gain pot
-the cable from the middle lug of the volume pot to the bright switch is also very noisy if i only slightly touch it with a chopstick
-Shielded cables goes to V1 / heater wire are far enough away
-ground connections are measured good
-i measured no DC-voltage on the pots
-the bright cap amplifies the noise somewhat if i turn on the bright switch
-I already checked the input jack; put the FET-Board outside and chopsticked everything but the noisefloor stays the same

I have attached pictures from the chassis, from the frequency measurement of the noise with my smartphone and a soundfile of the noise. The noise doesn't sound like 150hz.
The noise was measured and recorded with preamp- and mastervolume at noon.

I don't have the scope at the moment but maybe again next week.

Maybe someone can help me where to look.

Regards and thanks in advance
Christopher

[timrobertson100]

Welcome and congrats with the build.

Hard to tell from the photo - is the chassis painted inside? The early ones were, and you had to scrape the paint for the ground points. I think I read Erwin was changing that on later runs though.

[erwin_ve]

Hi Christopher,

Nice to see a finished build!
On the hum, you really need a scope. We can do some wild guesses:

1. As mentioned by Tim: if you have one of the early chassis: scrape off the groundpoints.
2. From the input jack to the pcb: keep the wire close to the chassis or use a piece of coax.
3.sometimes a input jack has a ground connection to the chassis and a ground connection through the ground wire. A isolation washer for the input jack should prevent 2 ground points for the same input jack.

Erwin

[Galef]

Hello and thanks for your response.

I already scraped all ground points and used lock washer while building the amp. All groundpoints measure great.
The Input jack is isolated and i already test it by having the jack floating freely, but nothing changed.

I have now replaced the input-jack cable with a coax but again nothing changed.

I'll wait until I have my scope back.

Christopher

EDIT: I can filter out all of the noise with the High-Filter, when its fully turned clockwise the amp is quiet. Nothing change with the Low-Filter.

[timrobertson100]

That clockwise thing is familiar... If you see my build thread I had some hiss that was not present when fully clockwise on the high filter.

After playing around on a lot of things mine turned out to be as simple as a cold solder joint on the ground side of the b+ caps. It wouldn't hurt to reflow all your power board solder joints as well.

Edited to add:

If you look at the schematic fully clockwise adds the 0.003 shunt to ground, the only position on that switch that does this. From what you've explained, my first guess is noise on the b+ feeding V1 which passes through to v2a unless in that filter position. If correct the problem lies somewhere on that b+ line (e.g. solder joints or grounding on the power board).

[erwin_ve]

Christopher: I cant see the 1M resistor across the input jack, is it hidden ?

[rccolgan]

I had a noise problem when I first built my SSS 002 but it was related to the heaters on and around v1. I see you did the optimized way for heaters so I don't think that would be the issue however see if moving that yellow wire directly across the gap instead of going to the pin. It may not be anything but you never know... Chopsticking things around will be valuable too.

[Galef]

The 1M resistor is there, it is directly on the input jack. It is also an RN65 so the color is nearly the same as the jack itself, it is behind the blue cable.
The yellow wire doesn't react to chop-sticking, generally i didn't find anything that reacted to my chopstick for now
But i will change that cable like on your pics Ryan, i dont know why i put it directly on the pin.

I now rewired the filter & Eq section to match the pictures from Ryan more. (all filter wires are now bundled)

I also reflowed all ground points on the PCBs.

Again nothing changed.

My artificial heater-CT is near the PT and not at the same spot like on Ryans layout, maybe is this a Problem?

Tomorrow i will reroute the groundwire from the last filter section on the powerpcb and then maybe also the artificial CT.
I also have a spare JJ Cap can, maybe i will swap them out when all of the above doesn't help. (I had bad experiences with a CE-can on a princeton Build, so i used a JJ).

Thanks @all for your help

[rccolgan]

Good stuff! Your build looks great BTW. I went back and checked my photos and I saw that on my first build, I routed that yellow wire exactly as you did. My guess is that you saw one of those pics so no need to be ashamed!

The artificial center tap location should be ok. I'd put that lower on the list of troubleshooting. The grounding could indeed help on your last filter. You must be really close since it's just within the v1 tube network as you found out with your troubleshooting. Maybe remove the FET power and ground after you did your other bits of troubleshooting. Crossing my fingers for you!

This community is really fantastic. I owe so much to them all!

[WhopperPlate]

Hard to tell from the photo but you might want to double check this shielded cable to make sure it’s not accidentally had the insulation melted from too much heat , or if any stray shielding wire hasn’t been neglected . Wouldn’t be the first time a shielded cable was bad on installation .

5AD83AB9-C0A0-4188-A210-B1E519C84286.jpeg

[timrobertson100]

The resistor on the left here next to v1 might also be worth a solder reflow (could be fine underneath of course but no harm)

[Richard1001]

Hello and thanks for your response.

I already scraped all ground points and used lock washer while building the amp. All groundpoints measure great.
The Input jack is isolated and i already test it by having the jack floating freely, but nothing changed.

I have now replaced the input-jack cable with a coax but again nothing changed.

I'll wait until I have my scope back.

Christopher

EDIT: I can filter out all of the noise with the High-Filter, when its fully turned clockwise the amp is quiet. Nothing change with the Low-Filter.

To be sure: all ground points should be all the metal parts connected to the chassis (tube shields, (slide)switches, pots, jacks etc)

[Galef]

I rerouted some grounding wires and reflowed everything around V1 and some other components, i also checked the grounding of all metalparts, indeed there was a problem with the high filter switch. I temporally added caps in parallel on the Cap can.

I disconnected the FET-Board also.

Nothing changed

But i think the noise is now only an hissing (i will "measure" again with my app soon) and now i can hear that my preamp-volume pot is scratchy, even after cleaning.
I measure no DC on it, but maybe the pot is defective or the coupling caps have problems, currently i have no filmcaps that I could install in parallel.

So i ordered some spare parts for the area around V1 and a new pot.

EDIT: the EQ pots have no scratchiness, so the coupling caps should be okay i think when i look at the schematic. Maybe only the volume/gain pot?

Thanks @all
Christopher

[rccolgan]

Can you post a new audio sample sweeping through the filters with no input connected, please? TBH hissing and elimination using the high filters is somewhat normal to a degree (same with the SSS 004 circuit). I run my SSS 002 with the high filter cutting 3-4 less than the max darkness cut. It should be less hissing than a Deluxe Reverb overall Hissing is better than humming and less to focus on. It still could be anything from a noisy cap somewhere to a hissy resistor.

[Galef]

The hum is still there but the noise floor generally lowered around 3db (same settings on the volume pots).
Because of the hissing at around 3000hz the hum is not perceived as such.

I attached the soundfile, high filter first and low filter second.
The FET-Board was still disconnected.

Tomorrow i will check everything again and by the end of the next week i should have my scope back and some spare parts.