Dallas Rangemaster: voltage collector

[Big Monk]

I have adjusted the bias with a trimmer and i would like to know if there could be problems of instability leaving the trimmer without putting the fixed resistance?

I have another question...anyone know about AC142K pnp transistor? I have read that they are very quiet, can anyone confirm this?

Have you entertained a transistor from Small Bear Electronics? Steve has RM specific transistors which bias to spec and are quiet.

[ricci]

I bought them on eBay but since the OC44 broke, I wanted to try again with the PNP AC142K.
For the moment, the RM I made is a PNP with AC127.

[percyhornickel]

Hi, I build a RMwith AC127 too, sounds great. I put a B100k pot instead 68K so I can bias 7 volts or some othes config. I put a switch por input cap too 5n/10n/15n. I really like the RM in a dirty channel, it gets a really "colored" bright sound.

[percyhornickel]

I have build a RM with AC127. A b100k pot instead 68k and input cap selector 5n/10n/15n. Sounds great in dirty channels or tube/Dirty amps.

[ricci]

I would like to ask you if the rustle is loud but I realized that if I look for the original RM I have to keep the rustle too, just listen to some isolated tracks of songs from the 70s. I also realized that the rustle is annoying to the listener only if you are not playing otherwise it is as if it were not there because what matters is the signal to noise ratio. Of course, if I manage to reduce it, it's always better.

[percyhornickel]

I don´t know if you are talking about the "hiss" noise. The hiss noise y almost a charateristic of the RM. Even, when I just building I was concern about so I dadecated plaety of time read a lot about it and see some videos then I saved a list which the hiss noise is so noted. If this is the case I let you here some videos where you can hear just the rm is turned on:

https://www.youtube.com/watch?v=gEdekaZC40E
https://www.youtube.com/watch?v=p5PbyqIdjGw
https://www.youtube.com/watch?v=sNYyjWSsm2k
https://www.youtube.com/watch?v=9G-e5_ALWyI
https://www.youtube.com/watch?v=InxLJ9vYFXc
https://www.youtube.com/watch?v=9mv71HCvuE0
https://www.youtube.com/watch?v=z7cG5uzftj4

For my build I design a small pcb that includes the three inpput caps, I don´t like long component´s legs from one side to another of the circuit, this way induces to add weird noises even the hiss increases. The mine has a normal hiss level, it´s there but not too loud and is almost pleaseful to hear.

[percyhornickel]

Some pics of my build:

[ricci]

Thanks for sharing !

At 1:27 of this video
https://www.youtube.com/watch?v=9G-e5_ALWyI

the noise is really impressive

but it can also be perceived here in an isolated track by Brian May

https://www.youtube.com/watch?v=8XuhJ7qDV9E
at 1:13

[percyhornickel]

There is too too too much hiss in the first video, something must be wrong with the circuit. I don´t know, maybe the very transistor..     

The second one is how it supposed to sound (mine does it very likely), even the hiss is amplified because is using a kind of delay too, you can note it in almost the whole guitar sections.

You have to be aware this hiss sound gets louder if you put a high gain pedal in front, don´t do it...   ...just use your RM with a dirty channel or a tube amp, the sounds is beautiful.

[ricci]

There is too too too much hiss in the first video, something must be wrong with the circuit. I don´t know, maybe the very transistor..     

Will surely be the transistor, unlikely to make a mistake in such a simple circuit

You have to be aware this hiss sound gets louder if you put a high gain pedal in front, don´t do it...   ...

Of course, but the hiss also increases with the RM gain although the pedal is already effective with the gain potentiometer not at 100%

[antonis]

https://www.diystompboxes.com/smfforum/index.php?topic=100982.0

P.S.
A 47-100 pF Miller cap (between Collector & Base) never harmed any CE amp.. 

[ricci]

In my NPN I noticed that by replacing the AC127 with a BC237C and adjusting the bias to around 8V the hiss disappears and the sound becomes quite mellow when the guitar volume is turned down. Basically I have more nuances of sound and almost zero hiss. So I'd like to know what can happen if I don't respect the 7V bias.

[iainpunk]

that tranny is silicon
of course it has less noise.

i had my BD139 range master biased at 8.4V since it sounded the best there, it gave me a punk-rock sound when used in a clean amp and a really tight hard hitting grind when used into a dirty amp, but i biased it really close to gating, just at the brink. so its no problem to bias it anywhere else, just use your ears to where it sounds best!

cheers, Iain

[ricci]

P.S.
A 47-100 pF Miller cap (between Collector & Base) never harmed any CE amp.. 

I did some random tests and, I don't know why but it works better with a 33nF between emitter and collector. However, there is a ticking like an oscillation that decreases as the collector voltage increases until it reaches 9V. What can this ticking depend on? I also feel it when I take off the transistor, albeit to a very small extent so it shouldn't depend on the transistor, right?

Edit:

I add that if I completely turn down the volume of the guitar, the ticking shamefully predominates 


Edit 2:

Maybe I solved the ticking problem because I also have Arduino in the pedalboard which I was temporarily not powered and when I supplied the 5V to Arduino the ticking disappeared. I hope it never comes back.

[ricci]

that tranny is silicon
of course it has less noise.

i had my BD139 range master biased at 8.4V since it sounded the best there, it gave me a punk-rock sound when used in a clean amp and a really tight hard hitting grind when used into a dirty amp, but i biased it really close to gating, just at the brink. so its no problem to bias it anywhere else, just use your ears to where it sounds best!

cheers, Iain

Ok but I wanted to understand if the transistor could be damaged or other damage to other things.

[duck_arse]

I did some random tests and, I don't know why but it works better with a 33nF between emitter and collector.

ricci - did you really use 33nF? and really between emitter and collector? this is not the usual method, and may well be the cause of your [new] tick problems.

[iainpunk]

that tranny is silicon
of course it has less noise.

i had my BD139 range master biased at 8.4V since it sounded the best there, it gave me a punk-rock sound when used in a clean amp and a really tight hard hitting grind when used into a dirty amp, but i biased it really close to gating, just at the brink. so its no problem to bias it anywhere else, just use your ears to where it sounds best!

cheers, Iain

Ok but I wanted to understand if the transistor could be damaged or other damage to other things.

well, most transistors don't mind whatever you do with them when you work with less than 12V. but biasing the transistor nearer to 9V means that you have less current through the transistor, biasing it further away you will have more current.
but with such large resistors, the current won't ever damage the transistor!

cheers, Iain

[ricci]

ricci - did you really use 33nF? and really between emitter and collector? this is not the usual method, and may well be the cause of your [new] tick problems.

With the 33nF cap between E and C I reduce both the frying noise that is in the background and the tick but the latter I solved it as I wrote before.

[ricci]

well, most transistors don't mind whatever you do with them when you work with less than 12V. but biasing the transistor nearer to 9V means that you have less current through the transistor, biasing it further away you will have more current.
but with such large resistors, the current won't ever damage the transistor!

ok, so I'm fine

[antonis]

With the 33nF cap between E and C I reduce the frying noise that is in the background

Strange way for inreasing Power Supply Rejection Rate ..