Nkt275 gain

[Johnnyorange500]

Hi,

I've been thinking about NKT275 and was just interested in people's take on and experience with the best gain results within these transistors. I know people have different ideas on specs, etc.—high and low gain, and of course breadboarding. And people will say to just breadboard them and hear how they sound, but I would like to hear if anyone has had any luck with low HFe with these transistors, and if so, how low?

Cheers

Johnny

 

[Big Monk]

Hi,

I've been thinking about NKT275 and was just interested in people's take on and experience with the best gain results within these transistors. I know people have different ideas on specs, etc.—high and low gain, and of course breadboarding. And people will say to just breadboard them and hear how they sound, but I would like to hear if anyone has had any luck with low HFe with these transistors, and if so, how low?

Cheers

Johnny

Do you already have them?

I would be wary of the stock left of the older stuff and there are a TON of fakes floating out there.

 

[Johnnyorange500]

Yeah,
I've got a couple. I got them from an old 1960 pye popliner radio. But they’re all around the 60/75 hfe depending on the temp of the environment with low leakage.

 

[Big Monk]

Yeah,
I've got a couple. I got them from an old 1960 pye popliner radio. But they’re all around the 60/75 hfe depending on the temp of the environment with low leakage.

In my personal experience, and depending on the circuit you put around it, those hFE could make a great Fuzz Face.

You could go Q1 = 60 and Q2 = 75.

I've made a few Fuzz Faces with 50-60 hFE General Electric 2N169 transistors and they have that characteristic lower gain Germanium Fuzz Face sound without a doubt.

 

[Johnnyorange500]

Great stuff! Thanks for this much-appreciated. Overall, I paid £40 for the two radios, so not too bad I think?! and there defo the real deal without a doubt got smaller legs than I’d like too but hey.

So any tips on making any changes to the resistor or capacitor values to make it work better? Or would the generic base values work?

 

[Big Monk]

So any tips on making any changes to the resistor or capacitor values to make it work better? Or would the generic base values work?

I rarely change the bias resistor for Q1. 33k just always seems to work there.

My general setup is:

For Silicon Transistors - Bias Resistor = 1.2k + 5k Trim
For Germanium Transistors - Bias Resistor = 2.2k + 10k Trim

I tend to vary the feedback resistor between 91k-110k depending on what the voltages are looking like and If I want a small fine tuning of the overall gain structure of the pedal.

 

[SillyOctpuss]

Well the four I've got are a matched pair with both at 58 hfe and sub 0.040 leakage. The other two are on the other end of the scale for Nkt275 86hfe and 88hfe again with pretty low leakage. These readings were taken in my workshop which is pretty cold at the minute.

The gain range for Nkt275 on the data sheets are 30-90 hfe.

So far I love the 58hfe set, they sound really fantastic with my Marshall and strat. I've got a standard 33k resistor to bias q1 and a trim pot for Q2. They bias up just fine.

I got one of mine from a pye popliner too.

What was the nkt278 like from your popliner? Mine had a crazy high hfe and leakage over 0.400.

 

[Johnnyorange500]

Well the four I've got are a matched pair with both at 58 hfe and sub 0.040 leakage. The other two are on the other end of the scale for Nkt275 86hfe and 88hfe again with pretty low leakage. These readings were taken in my workshop which is pretty cold at the minute.

The gain range for Nkt275 on the data sheets are 30-90 hfe.

So far I love the 58hfe set, they sound really fantastic with my Marshall and strat. I've got a standard 33k resistor to bias q1 and a trim pot for Q2. They bias up just fine.

I got one of mine from a pye popliner too.

What was the nkt278 like from your popliner? Mine had a crazy high hfe and leakage over 0.400.

Nice one! EBay?

Yeah, I was worried they were going to be too low gain and someone suggested that they wouldn’t work and are too low gain! but got nothing to lose and if yours sound great there in good stead. So gonna give it a go. Did you use yours in a fuzz face replica or in a more modern concept fuzz? My nkt278 from what I remember were around the 100/150 hfe mark. So yeah a bit odd very high gain

Johnny

 

[SillyOctpuss]

Nice one! EBay?

Yeah, I was worried they were going to be too low gain and someone suggested that they wouldn’t work and are too low gain! but got nothing to lose and if yours sound great there in good stead. So gonna give it a go. Did you use yours in a fuzz face replica or in a more modern concept fuzz? My nkt278 from what I remember were around the 100/150 hfe mark. So yeah a bit odd very high gain

Johnny

I've been using mine in a sunface clone. Your's definitely aren't too low gain, I've been testing a lot of different transistors with various hfe recently and definitely prefer lower values for a fuzz face.

Between the two sets of Nkt I've got I definitely prefer the lower gain set, they clean up really well.

I've also been looking at a lot of the Analogman Nkt sun faces and their gain ranges seem to go from about 40 for q1 up to 90 for Q2 so yours are right in the middle of that.

Are you putting yours in a straight fuzz face?

 

[Johnnyorange500]

I've been using mine in a sunface clone. Your's definitely aren't too low gain, I've been testing a lot of different transistors with various hfe recently and definitely prefer lower values for a fuzz face.

Between the two sets of Nkt I've got I definitely prefer the lower gain set, they clean up really well.

I've also been looking at a lot of the Analogman Nkt sun faces and their gain ranges seem to go from about 40 for q1 up to 90 for Q2 so yours are right in the middle of that.

Are you putting yours in a straight fuzz face?

Man! that’s great to hear. I’m not too sure? Was going to put them in a fuzz face, but might do something a little different. I’ve done 3 fuzz faces so.. might do the same as you and give a go at a sunface clone.