Hi all, I have been rocking this darlington rangemaster circuit for at least half a decade now and I am tired of replacing the germanium transistors bi-annually. I installed some 2n3904 in place of the MP44s I usually use and the circuit just sounds extremely "farty" and not in a good way. There is consistent signal but just really distorted in a bad way (like way worse than the difference between Ge and Si would give).
Changes I have made to the attached circuit (and used for years): took RC out for maximum gain, RD is 15K and RE is 3.3k.
Any thought what could have gotten messed up?
Changes I have made to the attached circuit (and used for years): took RC out for maximum gain, RD is 15K and RE is 3.3k.
Any thought what could have gotten messed up?
Two things come to mind:
Wrong biasing: Rb and Rd have to be increased until you have about the old bias currents back. I would try
Rb = 120 kohm
Rd = 33 kohm
Is that measured 7 V for the original situation?
Too high current gain of the transistors, so they work more as quite nonlinear transconductance amplifiers than as reasonably linear current amplifiers.
By the way, I would add a 1N4148 with its cathode connected to the base of the first transistor and its anode to ground to protect the input transistor against emitter-base avalanche breakdown when there is a too large input signal.
Wrong biasing: Rb and Rd have to be increased until you have about the old bias currents back. I would try
Rb = 120 kohm
Rd = 33 kohm
Is that measured 7 V for the original situation?
Too high current gain of the transistors, so they work more as quite nonlinear transconductance amplifiers than as reasonably linear current amplifiers.
By the way, I would add a 1N4148 with its cathode connected to the base of the first transistor and its anode to ground to protect the input transistor against emitter-base avalanche breakdown when there is a too large input signal.
Current and gain are set for very low gain transistors.
So id expect the usual fart sound from these circuits
with replacement silicon.
Far as I remember basically 700 Hz highpass.
and the gain just drove amps into distortion.
Basic tube screamer with tone control
vast improvement.
turn gain almost all the way down.
Or just use the tone control from a screamer
being it is a treble booster with variable control.
So id expect the usual fart sound from these circuits
with replacement silicon.
Far as I remember basically 700 Hz highpass.
and the gain just drove amps into distortion.
Basic tube screamer with tone control
vast improvement.
turn gain almost all the way down.
Or just use the tone control from a screamer
being it is a treble booster with variable control.
Probably ment MPSA44
400 volt general purpose silicon transistor.
Just a basic low noise BC546 is suitable for such low voltage
silicon
Can use NTE103 for germanium
its likely no different than 2N2354
and zillion other general purpose GE
My point?
Range master is hopelessly obsolete BUT it was used by Guitar Gods Clapton, Blackmore, etc.
So you just build the original circuit, with obsolete Germanium transistors and all, and call it a day.
Why "update" it?
What's the point?
If you want treble boost with modern components you just design one.
FWIW my very first Musical Instrument commercial product in 1969 was a Treble Booster straight from the pages of Popular Mechanics.
And it already used an NPN Silicon transistor.
Germaniums were already obsolete (yes, in 1969!), used only in battery powered AM radios. Not readily available in shops any more, I had to buy the Hitachi or Toshiba 6 transistor "radio sets" 2SA49, 2SA52, etc.
Range master is hopelessly obsolete BUT it was used by Guitar Gods Clapton, Blackmore, etc.
So you just build the original circuit, with obsolete Germanium transistors and all, and call it a day.
Why "update" it?
What's the point?
If you want treble boost with modern components you just design one.
FWIW my very first Musical Instrument commercial product in 1969 was a Treble Booster straight from the pages of Popular Mechanics.
And it already used an NPN Silicon transistor.
Germaniums were already obsolete (yes, in 1969!), used only in battery powered AM radios. Not readily available in shops any more, I had to buy the Hitachi or Toshiba 6 transistor "radio sets" 2SA49, 2SA52, etc.
I have a Legendary Tones Time Machine Boost from 2003-2004, it’s one of the first batches before it was sold to Keeley.
https://www.vintageguitar.com/3147/legendary-tones-time-machine-boost
It has a few different circuits in the box.
The vintage mode has a Ge transistors, the other is Silicon JFETs I think.
I really recommend it, you can fine them fairly cheaply now second hand. No one on YouTube has yet done a rediscovery of this pedal and inflated the price
https://www.vintageguitar.com/3147/legendary-tones-time-machine-boost
It has a few different circuits in the box.
The vintage mode has a Ge transistors, the other is Silicon JFETs I think.
I really recommend it, you can fine them fairly cheaply now second hand. No one on YouTube has yet done a rediscovery of this pedal and inflated the price
Yeah - just use original (ish) Ge transistors, call it a day - and add the damn reverse protection diode so you don’t have to keep changing out the transistors anymore.
Your schematic says "Q1 and Q2 should have gains of 20 to 25". A 2n3904 has a gain >100. I would guess the circuit is massively overdriven, and also possibly biased wrong for the 2n3904.
I would ditch the darlington. A single 2n3904 is plenty loud. If you look for schematics based on the Naga Viper, it's a silicon rangemaster type circuit that has things biased right, and includes a few tweaks that help get a good sound from a silicon transistor (which will naturally roll off highs less than germanium, at least to my ears).
I would ditch the darlington. A single 2n3904 is plenty loud. If you look for schematics based on the Naga Viper, it's a silicon rangemaster type circuit that has things biased right, and includes a few tweaks that help get a good sound from a silicon transistor (which will naturally roll off highs less than germanium, at least to my ears).
That.
Original Range master was a single Germanium transistor.
Horribly low input impedance but that's what it was, the real thing.
And it needs that low impedance so very small input capacitor cuts bass and low mids so it works like a "treble boost" Sort of.
"Correcting" that by using a Darlington completely misses the point.
Using Silicon is even worse.
Again: just build the original one, the original way.
THIS is a Rangemaster.
That "thing" above is an abomination.
Original Range master was a single Germanium transistor.
Horribly low input impedance but that's what it was, the real thing.
And it needs that low impedance so very small input capacitor cuts bass and low mids so it works like a "treble boost" Sort of.
"Correcting" that by using a Darlington completely misses the point.
Using Silicon is even worse.
Again: just build the original one, the original way.
THIS is a Rangemaster.
That "thing" above is an abomination.
The Ge transistors I usually use are russian NOS MP44 transistors not MPSA44.
The rangemaster circuit is perfect for my style of playing and the amps I build.
I will continue to use the darlington setup as I don't use this circuit as a treble boost but as a distortion pedal. The massive benefit (besides sounding better than an op amp with diode clipping) is being able to roll the guitar volume down to adjust how much distortion/go clean and have all that headroom to play around. I quite like my abomination thank you very much
Thank you so much for mentioning the protection diode, thats kind of what I was fishing for in my last post about the Ge issue.
I also agree its probably a biasing issue, I am going to spin up a quick test fixture and dial it in. Thank you guys for your suggestions I really appreciate it.
The rangemaster circuit is perfect for my style of playing and the amps I build.
I will continue to use the darlington setup as I don't use this circuit as a treble boost but as a distortion pedal. The massive benefit (besides sounding better than an op amp with diode clipping) is being able to roll the guitar volume down to adjust how much distortion/go clean and have all that headroom to play around. I quite like my abomination thank you very much
Thank you so much for mentioning the protection diode, thats kind of what I was fishing for in my last post about the Ge issue.
I also agree its probably a biasing issue, I am going to spin up a quick test fixture and dial it in. Thank you guys for your suggestions I really appreciate it.