Tone bender transistors

[Johnnyorange500]

Hi,

I’ve acquired a couple of germanium transistors one is a cv7003 and a 2G371A would these work together in a tone bender build. I obviously would need one more transistor I was hoping to get another 2G371A but could only get one! Would a 2G302 work together with these?
Cheers

Johnny

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[JamieJ]

It’s all about hFE and leakage with these circuits (and how they are biased) so part number doesn’t really count for much. Depends on what tone bender you are building also.

There’s load of threads here, FSB and diystompboxes so google is your friend. Also a try it on a breadboard before you commit to a PCB.

 

[Johnnyorange500]

It’s all about hFE and leakage with these circuits (and how they are biased) so part number doesn’t really count for much. Depends on what tone bender you are building also.

There’s load of threads here, FSB and diystompboxes so google is your friend. Also a try it on a breadboard before you commit to a PCB.

Hi jamie. I’m looking to build a mk1 tone bender. My cv7003 is around the 112 hFE and the 2G371A is around 60 hFE.. so was just wanting some clarification on the matching of these all together in one build I’m not sure what the 2G302 hFE is so would have to measure these when I buy them and take a risk. Thanks for the suggestions much appreciated.
Cheers

 

[jhaneyzz]

I completely agree with Jamie’s last point, especially with a simple circuit like a tone bender. Breadboard it first and tweak to your heart’s content. And you’ll learn 10X more about how to tweak the build.

You end up not only with a pedal you like, but one that you feel a lot more connected to and familiar with.

 

[andare]

First of all always specify which Tone Bender since there are at least 4 different circuits.

HFE is not enough, you need leakage as well.

For an MKI I shoot for these specs:

Q1 gain 60-80 leakage 100-150uA

Q2 gain >100 no leakage necessary so low is better

Q3 gain >100 leakage around 150

You want -8V on Q3c to have good output, tone and no artifacts.

Don't touch the resistors, the circuit should work with stock values. Forcing voltage with trim pots results in poor tone IME.

You can lower the 2m2 for more output and the 470k for more gain earlier in the Attack knob. I also recommend an audio pot there for a more gradual increase in gain.

These are my findings, it's possible that those numbers won't work for you.
The above doesn't work with the other Tone Benders.

If you want to build germanium fuzzes you need to buy many because most of them won't work, especially in Tone Benders.

 

[mdc]

Tone Bender MKIs can be really fussy - your options are likely going to be to either build the circuit around the transistors you have or to select transistors that work in the circuit. ie, limit variables and go from there. It's a simple enough circuit parts and connections wise to breadboard easily, but it can be extremely difficult to get it sounding "right."

Again, there are LOTS of threads on diystompboxes, freestompboxes, and the DAM forum with gain and leakage suggestions. If you don't have a way to measure gain and leakage of the devices you have on hand, you might want to invest in one of the $30 eBay options and save yourself a lot of headaches.

 

[andare]

Tone Bender MKIs can be really fussy - your options are likely going to be to either build the circuit around the transistors you have or to select transistors that work in the circuit. ie, limit variables and go from there. It's a simple enough circuit parts and connections wise to breadboard easily, but it can be extremely difficult to get it sounding "right."

Again, there are LOTS of threads on diystompboxes, freestompboxes, and the DAM forum with gain and leakage suggestions. If you don't have a way to measure gain and leakage of the devices you have on hand, you might want to invest in one of the $30 eBay options and save yourself a lot of headaches.

Or get a TC1 tester, which is useful for measuring all kinds of components and IMO indispensable for builders.

 

[JamieJ]

What’s the consensus on the TC-1’s ability to assess leakage? I seen people say that you need a DCA75 to do that job reliably.

 

[Johnnyorange500]

Cheers guys. Think it’s going to be a long process of trying to get parts and testing them with a TC1 tester which I do own. And using a breadboard to try and get it right. I’m not going to jump into it..so will take on board all the advice. I do have an idea of leakage too. I Just didn’t mention it on the post. Cheers

Johnny

 

[Mentaltossflycoon]

What’s the consensus on the TC-1’s ability to assess leakage? I seen people say that you need a DCA75 to do that job reliably.

I got a "better than nothing" response to this question a while back. I'm assuming accuracy isn't great.

 

[andare]

What’s the consensus on the TC-1’s ability to assess leakage? I seen people say that you need a DCA75 to do that job reliably.

I only have a TC1 so I can't compare it to a proper tester. It works for my purposes.