B1 with Korg Triode

[Ben Mah]

highendaudio,

Was it squealing with a source connected to the input?

Does it squeal with no source connected to the input?

Does the squeal volume change with volume pot adjustment?

Are all of the voltage measurements specified in the project documents within specifications?

 

[hyendaudio]

Hi Ben Mah
Yes, the noise is present with and without input present. The noise is not affected by volume and the input voltage is at 9.1V across the zenner diode.

Thank you

 

[Ben Mah]

What are the voltages at the other Test Points? T3, T5, T6, T7, T8?

What if you short the inputs?

Does it play music in addition to squealing? Or no music output?

How loud is the squeal?

How did you determine the frequency of the squeal?

Did you try connecting to a different amplifier?

 

[Zen Mod]

squeal in both channels.

try putting 100nF caps ( or so) across electrolytics in PSU

 

[hyendaudio]

Ben Mah - can you share a link to documentation showing test points or other troubleshooting guidelines, please?

The squeal is about 75db. I used a spectrum analyzer to determine the frequency, which is actually right around 5,124khz. I did hear something other than squeal through the preamp, but didn't try to play any program material through it. And yes, it's neither the amplifier nor the interconnects, I've tried swapping those.

Zen Mod - are you suspecting a bad PS electrolytic?

 

[Ben Mah]

Documentation in post #1 of this thread.

As you had originally mentioned and as Zen Mod is suggesting, as both channels are involved, it points to the power supply system. However it doesn't hurt to confirm that the rest of the circuit is indeed working properly.

It may also be a solder issue. Since it was working properly prior to it sitting on the shelf for a few months, it could be a issue with connectors/wiring being stressed by removing and connecting interconnects.

 

[hyendaudio]

I've moved it off the bench for the moment to service a turntable and will circle back to it in a few days.

Thank you both for your suggestions. I'll report back as soon as I have an update.

 

[sparkpark]

I just built my B1 Nutube and from the first time I used it I experienced a squeal. It sounds like ringing, high frequency feedback. Very loud, constant, not dependent on input or volume pot position, music does continue to play. Only starts after about 2-5 minutes of use. All voltages ok. Could it be physical feedback from the tube being microphonic?

Parker

 

[ItsAllInMyHead]

Could it be physical feedback from the tube being microphonic?

From what you describe... almost definitely.

 

[birdbox]

I have a bunch of Zen Mod's Korg B1 Soft Heat Start boards for dirt cheap if anyone is interested in trying them. I ordered 50 qty from JLCPCB just recently. I have not yet built one up and installed into the circuit, but I have 4 qty Korg B1 builds that will likely all get this circuit along with the AmyAlice SMPS filter. I have both the soft heat start and AmyAlice boards posted in the swap meet.

Thank you for your generosity @Zen Mod !

 

[Fabian85]

I hate cable routing. Thats, in my opinion one of the most annoying thing in DIY. Thats why I lay out 2 simple addon boards. The right board carrying the slim version of AmyAlice, filters DC, routes it to front where it can be connected to On / Off switch, then it will be routed back where it can be wired with short wires to B1K Board.

Left Mainboard is simpler. Its just the L-shaped board, all inputs can be accomodated here while on front layer, the signal layers run in parallel to input switch, on back layer, common grounds for left and right channels are routed to the front. I like it clean 🙄

My main idea in designing these two helper boards was to use up the space within the "official DIYAUDIO case" from Modushop and minimize cable salad routed through it.

 

[ItsAllInMyHead]

^ Oooooooooh! Now THAT is a very thoughtful implementation. 😎

 

[Fabian85]

Added some explanation @ItsAllInMyHead ;-)

Sadly I couldnt wait and thats why the right board has some small hickup. The lower of the 3 holes carrying SlimAlice is about 1mm too close, so the spacer is no absolute perfect fit. Kinda annoys me, but I only had gerbers of the DC Filter and had to measure from them in gerber viewer. Maybe I will do a rework, cause I hate this imperfection. (in the end absolutely no one will see it, but i know it 🤣)

 

[Brijac]

I love it! Very well done 🙂

in the end absolutely no one will see it, but i know it 🤣)

I know right 😅 And I always say, "but I personally know how it looks inside" 😁 Weird ocd we have.

 

[Fabian85]

That was the first case iteration since 2018 😂😂😂

Don't ask for the toilet paper rolls. In there were like 15 or 16 for transport purposes. Use what you got! 😎

 

[Zen Mod]

That was the first case iteration since 2018

That's The Spirit!

 

[Fabian85]

Continue building it into the case. As planned, solid core silver cables. AmyAlice (thanks for that @Mark Johnson ) foes a perfect job. Completely got rid of wall wart ringing. Test setup is rock silent. Now waiting for the switches to do the final front panel wiring.



If anyone would like to have the gerbers for the Addon boards I can share them for free ofc.

 

[Skywave-Rider]

Here's ZM's fancy fix for soft heat start up.

Works like a champ. Beautiful design, easy assembly and installation.

I used a plastic stand off to mount above the board. Fits the space above the removed 9V zener.

I've got 3 boards if anyones interested - PM me.

Thanks ZM and all the contributed to this sweet fix.

@carlpsyd Has the mod fixed the left channel filament problem?

 

[carlpsyd]

Yes, believe it has. I've had no problems since adding the soft startup module.

 

[birdbox]

If anyone is interested in giving the "soft heat" a try, I've got some full up kits posted in swap meet. I still haven't modified mine, but plan to give it a go soon and will post my results.