# Duocast tone seems off



## Peddler (May 12, 2021)

Hello fellow builders. I just finished the Duocast and it doesn’t seem to sound like what I expected. It is very bright with more treble than my rangemaster. Otherwise, it works like it should.

I used an Ac128 with 80 HFE, and checked the cap values. It all seems correct. Does anyone have any ideas or bias voltages that I can check? I also confirm my resistors with a DMM to be safe when building.

Thanks for your insights!


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## JamieJ (May 12, 2021)

How have you got the low cut knob set? Mine is almost completely off.


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## Peddler (May 12, 2021)

JamieJ said:


> How have you got the low cut knob set? Mine is almost completely off.


I have the low cut off completely, but it is still pretty bright.


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## Cucurbitam0schata (May 12, 2021)

Dumb question, but worth asking - was your IC in when trying out the pedal?


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## Peddler (May 12, 2021)

Cucurbitam0schata said:


> Dumb question, but worth asking - was your IC in when trying out the pedal?


I am still waiting for the IC to arrive, so at this point I have only tried the pedal at 9V. The IC is a charge pump for 24V when the switch is toggled.

I tried the pedal out of the enclosure today and there was no difference. I’ll try to clean it with rubbing alcohol and see if that helps.


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## music6000 (May 12, 2021)

Peddler said:


> I am still waiting for the IC to arrive, so at this point I have only tried the pedal at 9V. The IC is a charge pump for 24V when the switch is toggled.
> 
> I tried the pedal out of the enclosure today and there was no difference. I’ll try to clean it with rubbing alcohol and see if that helps.


I can get Low Cut to where I like it @ 8.00 to 9.00 O'Clock so nearly at minimum.
There is definately room for improvement on this Low Cut Control!
Can you hear the Bass coming in when you you get to thee last 1/4 of a turn CCW.
If not there maybe another issue, If yes you could try upping C5 value to something like 680nf & see if that brings the pot back to within the range you want.


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## Peddler (May 12, 2021)

I scraped between all of the solder points with a knife and splayed down the pcb with electrical parts cleaner.

Does the standard duocast cut a lot of bass in peoples’ experience? Maybe my expectations were off.


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## Peddler (May 12, 2021)

music6000 said:


> I can get Low Cut to where I like it @ 8.00 to 9.00 O'Clock so nearly at minimum.
> There is definately room for improvement on this Low Cut Control!
> Can you hear the Bass coming in when you you get to thee last 1/4 of a turn CCW.
> If not there maybe another issue, If yes you could try upping C5 value to something like 680nf & see if that brings the pot back to within the range you want.


I may try to swap C5. That is a good idea. It looks like C1 could have a similar effect, but my circuit knowledge is n00b.


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## music6000 (May 13, 2021)

Peddler said:


> I may try to swap C5. That is a good idea. It looks like C1 could have a similar effect, but my circuit knowledge is n00b.


I just jumpered a 330nf giving me 660nf at C5 & had to turn the Low Cut knob CW to 11.00 OClock for the same setting I normally use it at 8.00 to 9.00 so it works!
It could be your AC128 is giving you a harsher sound?


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## Peddler (May 13, 2021)

Solved.

The AC128 was bad, resulting an a tone that lacked treble and was low on gain. I learned the hard way that I should socket Ge Transistors. Another AC128 that I had on had fixed it and now the tone is glorious. It is largely transparent with gain increasing the saturation and adding some breakup. I used a 60hfe Transistor, so there is likely fatter and more wild fuzz available with a higher gain one.
Thanks for the troubleshooting help!


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## JamieJ (May 18, 2021)

Peddler said:


> Solved.
> 
> The AC128 was bad, resulting an a tone that lacked treble and was low on gain. I learned the hard way that I should socket Ge Transistors. Another AC128 that I had on had fixed it and now the tone is glorious. It is largely transparent with gain increasing the saturation and adding some breakup. I used a 60hfe Transistor, so there is likely fatter and more wild fuzz available with a higher gain one.
> Thanks for the troubleshooting help!


Glad to hear you sorted it!


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## fig (May 18, 2021)

That's great!



Peddler said:


> I used an Ac128 with 80 HFE





Peddler said:


> The AC128 was bad


Did you use a transistor tester to determine this?


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## Peddler (Jun 6, 2021)

To test hfe I have a small breadboarded circuit according to RG Keen’s fuzz face article that you can find online.

I decided the transistor was bad when a replacement worked.

One very interesting trait of this pedal is that it requires some warm up time. It will also still work and slowly fades out when power removed. I assume this is due to using some higher voltage capacitors based on what I could source. They seem to need a little time to charge up when my One Spot is first plugged in.


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