Blackvibe 6L6 Strange behavior on tone pots
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Blackvibe 6L6 Strange behavior on tone pots
Hi guys
I build a 6L6 blackvibe no trem, no verb.
For safety reasons I gave it to a tube tech, he says everything is fine.
What i really wonder is how the tone pots react, in my understanding weirdly.
On any blackpanel amp if you turn all the tone pots to 0, there will be no sound at all.
This seems, even if rob robinettes says 100% vibroverb, very different on the blackvibe. All Tone pots have a minimal scope/range of action.
When i turn bass from 0 to 10 this would equal like 3-4 on my super, or princeton. Same for treble, the middle would equal 3-5 on a super or Princeton. So the scope is very limited. It is so limitied, that i still think there might be a mistake in my soldering, even tough my amp tech, which is a real tube electronics pro , says ist ok.
Any suggestions or tips would be much appreciated!!
Thx reto
I build a 6L6 blackvibe no trem, no verb.
For safety reasons I gave it to a tube tech, he says everything is fine.
What i really wonder is how the tone pots react, in my understanding weirdly.
On any blackpanel amp if you turn all the tone pots to 0, there will be no sound at all.
This seems, even if rob robinettes says 100% vibroverb, very different on the blackvibe. All Tone pots have a minimal scope/range of action.
When i turn bass from 0 to 10 this would equal like 3-4 on my super, or princeton. Same for treble, the middle would equal 3-5 on a super or Princeton. So the scope is very limited. It is so limitied, that i still think there might be a mistake in my soldering, even tough my amp tech, which is a real tube electronics pro , says ist ok.
Any suggestions or tips would be much appreciated!!
Thx reto
- martin manning
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Re: Blackvibe 6L6 Strange behavior on tone pots
The 6k8 tail resistor on the mid pot is what keeps the tone controls from killing the sound altogether. If you want to go back to the AAB763 functionality, delete that resistor and consider replacing the 100k mid/raw pot with a 10k audio.
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Re: Blackvibe 6L6 Strange behavior on tone pots
Thx so much ! Will the scope then also be as on a ab763?
Thx!
Thx!
- martin manning
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Re: Blackvibe 6L6 Strange behavior on tone pots
Possibly. Unless you have the 100k mid pot turned way down, to zero, you have lifted the tone stack to a significant degree. Do the treble and bass controls seem more normal when the mid pot is at zero?
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Re: Blackvibe 6L6 Strange behavior on tone pots
Hmm i did not try that. I will go to the 10k a pot on the middle and kill the 6.8k resistor. Instead of the resitor i go to ground with the lug directly right?
Thx martin!
Thx martin!
- martin manning
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Re: Blackvibe 6L6 Strange behavior on tone pots
Correct. Try it with the mid pot at zero, which would be 6k8 resistance to ground, like a 10kA mid pot set at ~3:00.
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Re: Blackvibe 6L6 Strange behavior on tone pots
Will do so in abfew days and keep this treath updated.
Thx !!
Thx !!
Re: Blackvibe 6L6 Strange behavior on tone pots
Fender knobs for these amps are 1-10, no 0 available, CCW = 1, CW = 10.retodellatorre wrote: ↑Sun Mar 31, 2024 6:20 pm ... On any blackpanel amp if you turn all the tone pots to 0 ...
With a regular 1-10 knob and 10k log pot, I recall a fairly high setting is required, maybe around '8', to achieve 6k8 resistance.martin manning wrote: ↑Sun Mar 31, 2024 8:39 pm ... 6k8 resistance to ground, like a 10kA mid pot set at ~3:00.
Maybe you mean 3 o'clock, where noon is 50% mechanical rotation?
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- martin manning
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Re: Blackvibe 6L6 Strange behavior on tone pots
Exactly. Using Alpha 15% log taper, 270 deg rotation, I make it 02:52:48 on the clock, or 8.38 on a Fender-type 1-10 knob to get 6k8 of 10k.
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Re: Blackvibe 6L6 Strange behavior on tone pots
Ok - I changed the tone pot to a AK10 removed the 6.8k resistor. Now it sounds like my blackpanels, in my sense muuuuch better control in bass treble and middle. It still sounds a little icepicky and „new“ but i guess it will break in a little too.
Thx for your help!
Reto
Thx for your help!
Reto
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Re: Blackvibe 6L6 Strange behavior on tone pots
What is the bright cap value? 250p? Try 100p. Break-in isn't probably going to retire ice picky.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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Re: Blackvibe 6L6 Strange behavior on tone pots
Honestly … i did not install the bright switch, since i never used it on my super reverb - that said, the cap is used if the switch would be off (not bright) and be bypassed if on (bright) right? If so i made a thinking mistake and left the cap also off
So i have to solder in the cap anyways even if i dont use the switch right?
Thx so much for your help!!
So i have to solder in the cap anyways even if i dont use the switch right?
Thx so much for your help!!
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Re: Blackvibe 6L6 Strange behavior on tone pots
Bright cap makes brighter.
Turn mid control up slightly, and turn treble down the same amount.
If you do add the bright cap it peaks ^ the treble so you turn treble control down. The natural curve might work better.. or might not. You should test.
Turn mid control up slightly, and turn treble down the same amount.
If you do add the bright cap it peaks ^ the treble so you turn treble control down. The natural curve might work better.. or might not. You should test.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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Re: Blackvibe 6L6 Strange behavior on tone pots
Oh dang sorry… and thanks!
So since i dont have the switch and the cap, another Method that rob robinettes has on his page is placing a cap over the 820 ohm nfb resistor to reduce icepick.
Have you guys done that before?
Thx!
So since i dont have the switch and the cap, another Method that rob robinettes has on his page is placing a cap over the 820 ohm nfb resistor to reduce icepick.
Have you guys done that before?
Thx!
- martin manning
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Re: Blackvibe 6L6 Strange behavior on tone pots
A cap across the FB resistor will introduce a phase shift, and might even cause oscillation, but you can give it a try. If that doesn't work, there are several other ways to reduce treble content, including placing a cap across a plate load, from plate to cathode, or across phase inverter anodes.