Dallas Rangemaster: voltage collector

[willienillie]

Well, more or less, yes.  I was talking more about collector voltage.  If your desire is to mimic the sound of an original unit (it may or may not be), then you should take impedances into consideration.  Large changes in resistor values will change impedances (and any HPFs and LPFs) within the circuit, and thus change the sound somewhat, for better or worse.  This is a reason to select a transistor that gets close to the "best sounding" bias point with the original circuit resistor values.  (Caps influence sound too, but not DC bias).  That's where a ballpark "target" collector voltage becomes useful here, in selecting the transistor.  But you should still allow yourself to make smaller adjustments to get the "best" sound from the particular transistor you used.

The original Rangemasters didn't have bias adjustment trimmers.  Even though they had a much larger supply of Ge transistors to select from, I'm sure there was still quite a bit of sonic variation from one unit to the next.  Even at the same ambient temperature and battery voltage.

Another detail to consider in this case, two resistor values were different between the OC44 version and the OC71 version, from online pictures I've eseen.  So there is no "one" Rangemaster sound anyway, maybe more reason to feel free to tweak the values a little to get the best performance for your needs.

[ricci]

Thanks for everything you wrote. In fact, I experimented a bit and even made a Rangemaster NPN with an AC127 but, leaving the same resistors and capacitors as the OC44, as I expected it gives me a different sound from the OC44, shifted a little in the mid frequencies which not much I like it. What can I do to get the same sound as the 1044?

I had done the version with AC127 so I would have had no difficulty in daisy chaining pedalboards since the RM with the OC44 in a daisy chain with a power supply needs -9V but with none of my 3 pieces of MAX1044 I get the reverse and negative voltage, always and only positive and then I ordered some ICL7660SCPAZ

Someone told me that the Max1044 works at maximum with 10V but with me it worked until recently and easily converted the + 9V to -9V. I don't understand why it doesn't work anymore.

[willienillie]

from online pictures I've eseen.

Typo, but maybe "eseen" is appropriate for online pictures?

Thanks for everything you wrote. In fact, I experimented a bit and even made a Rangemaster NPN with an AC127 but, leaving the same resistors and capacitors as the OC44, as I expected it gives me a different sound from the OC44, shifted a little in the mid frequencies which not much I like it. What can I do to get the same sound as the 1044?

I've never had either type to mess around with.  Maybe there is some inherent difference between them such that they can never sound exactly the same.  They would probably be very close if they had similar gain and leakage, and were each biased to their respective sweet spots.

I built mine with a Matsushita 2SB175.  It sounds great, but I have no doubt it sounds at least a little different than the OC44 or OC71 originals.  But I've never played an original either, so I wasn't really chasing a specific sound.  (Don't get me started on Tube Screamers or Fender amp clones, lol)

So for either of your transistors, all I can advise is to tweak that trimmer to the best sound.  I also used a 100K trimmer in place of the 68K resistor, and small bumps make a big difference.

[Steben]

Well, more or less, yes.  I was talking more about collector voltage.  If your desire is to mimic the sound of an original unit (it may or may not be), then you should take impedances into consideration.  Large changes in resistor values will change impedances (and any HPFs and LPFs) within the circuit, and thus change the sound somewhat, for better or worse.  This is a reason to select a transistor that gets close to the "best sounding" bias point with the original circuit resistor values.  (Caps influence sound too, but not DC bias).  That's where a ballpark "target" collector voltage becomes useful here, in selecting the transistor.  But you should still allow yourself to make smaller adjustments to get the "best" sound from the particular transistor you used.

The original Rangemasters didn't have bias adjustment trimmers.  Even though they had a much larger supply of Ge transistors to select from, I'm sure there was still quite a bit of sonic variation from one unit to the next.  Even at the same ambient temperature and battery voltage.

Another detail to consider in this case, two resistor values were different between the OC44 version and the OC71 version, from online pictures I've eseen.  So there is no "one" Rangemaster sound anyway, maybe more reason to feel free to tweak the values a little to get the best performance for your needs.

To be honest thats why today most fuzz faces sound good while Jimi selected fuzz faces that sounded good.

[Electric Warrior]

Another detail to consider in this case, two resistor values were different between the OC44 version and the OC71 version, from online pictures I've eseen.  So there is no "one" Rangemaster sound anyway, maybe more reason to feel free to tweak the values a little to get the best performance for your needs.

You've probably seen one with a black glass OC44 then. These have a 4k7 instead of the 3k9 or 3k7 found most earlier yellow jacket OC44 and the OC71 units. These often (but not always) have a 680k instead of the usual 470k as well.

There is some variation for the input and output caps, too. Some units have a 0.0082µF output cap. 0.004µF input caps were used in the earliest units. Some OC71 units have a 20k or 22k pot.

To be honest thats why today most fuzz faces sound good while Jimi selected fuzz faces that sounded good.

There is a huge range of bias voltages that will sound good in a Fuzz Face. 10% resistor tolerance and 20% pot tolerance can mess with the bias a lot, though. So even if you select transistors that work well, each Fuzz Face may sound a little (or even quite a bit) different. That's not a bad thing. It gives you lots of different sounds to choose from. I'm finding it hard to make bad sounding Fuzz Face..

As germanium units get hot, they tend to get spittier sounding with less sustain and eventually will gate in an unpleasant and unusable way. They were often biased quite hot (by today's standards), so they would suffer from temperature related issues easily..

[ricci]

I decided to insert the RM with OC44 in the pedalboard and I'm waiting to pilot it with an ICL 7660 SCPAZ that should arrive in a few days and in the meantime I was making a consideration.

Since I already have a large spectrum booster in the pedalboard, I thought of making a modification to the RM to make it more versatile, perhaps adding a 100nF capacitor to the input and switching from broad spectrum to original RM, via a 6-way rotary switch with 2 positions .

But as there was little space available, I thought about equipping the RM with a simple switch. I wanted to make sure that when the booster pot is at minimum, the volume is the same as the dry guitar when the booster is off. It can be done ?

[Steben]

As germanium units get hot, they tend to get spittier sounding with less sustain and eventually will gate in an unpleasant and unusable way. They were often biased quite hot (by today's standards), so they would suffer from temperature related issues easily..

Jimi did settle for silicon

[BJF]

Hi There,

The sound you like should be your goal as voltages will differ with transistors used and there is no specific magic with voltages exact numbers more so the workingpoints.
Since the emitter is fully decoupled you gte gain according to gmxRC. You can swap out some noise and make unit to unit more equal by inserting a small resistor between
emitter and decouplig capacitor. There are some funny things happening at the edges of transfer caracteristics and let's say you put in 33R ( Ohms) gain would with an ideal transistor be 10K/33Ω
however this ratio is larger than gmxRC so actual gain will be closer to gmxRC even so a small resistor like that will limit some noise and some distortion and make difference between transistors a little less.
You can take this a step further and set ratio RC/RE equal to hfe;) but even a minimum of resistans will affect distortion and noise
This resistor will also affect hie. In the circuit since emitter is decoupled inputimpedance would be hie// with base bias network. Now hie for a germanium is on the order of a couple of KOhms but differs from transistor to transistor
So corner frequency at input will be less dependent on the bias network than the hie of the transistor used.


DC gain of the circuit is 2,5 times but AC gain is gmxRC because the emitter is decoupled for all audio frequencies.

The circuit has the standard bias setup to allow a number of transistors to clock in fairly equal and in production one would have to look at how to minimize variation between devices so that assembly becomes plug in only.
One can assume quite a bit variation with this circuit because it has its emitter fully decoupled and thus end result will be at heavily dependent of the transistor used.

In most any amplifier the workingpoint is what counts as it will set the overtones produced at overload and you can therefore in the circuit set working point by adjusting the emitter resistor which will be forced to have about 800mV across
it but the resting current produced will affect the workingpoint at Collector or you could adjust say bottom leg of bias network at Base.

For a circuit like this the key to sound lies in where the collector rests not the actual resistor values. You could easily make this circuit with parts you have at hand and then ratios of the components will have bigger impact than their actual value.

Since you use old germanium transistors there are a couple of leakage currents that will influence settings

So the unit is good when it sounds good not necessarily when it meets magic numbers

At your service
BJ
BJF Electronics
Sweden

[antonis]

let's say you put in 33R ( Ohms) gain would with an ideal transistor be 10K/33Ω however this ratio is larger than gmxRC so actual gain will be closer to gmxRC

For a 10k Collector resistor and Vcc/2 bias, Collector quiescent current shoud be 450μΑ so intrinsic Emitter resistor (r_e or 1/g_m) should be  about 56R..
This very resistor is set in series with 33R external resistor (Emitter load) so gain should be calculated as 10k/(33+56)..
Additionally, 10k Collector resistor value is "ideal", in the mean of infinite following effect input impedance..

[ricci]

Can you tell me if i'm wrong? I had thought of adding a resistor on the ground lug of the pot to have minimum volume equal to volume with RM bypassed and avoid it starting from zero. Can it work ?

[Big Monk]

Can you tell me if i'm wrong? I had thought of adding a resistor on the ground lug of the pot to have minimum volume equal to volume with RM bypassed and avoid it starting from zero. Can it work ?

I would just add a level control. My rangemaster has a blend control like the Easy Face and an output control after the boost pot. Covers a lot of sonic territory.

[ricci]

I would just add a level control. My rangemaster has a blend control like the Easy Face and an output control after the boost pot. Covers a lot of sonic territory.

Any wiring to refer to?

[Big Monk]

I would just add a level control. My rangemaster has a blend control like the Easy Face and an output control after the boost pot. Covers a lot of sonic territory.

Any wiring to refer to?

I'm not sure what board or wiring you used for your RM, but you would simply take the output of the circuit to lug 3 of a 100kA pot, send the wiper to the circuit output and ground lug 1.

Viola!

[willienillie]

I had thought of adding a resistor on the ground lug of the pot to have minimum volume equal to volume with RM bypassed and avoid it starting from zero.

It could be done.  The volume pot in a traditional Rangemaster is also the collector resistor.  Adding resistance there would change the bias, but it could be compensated for.

Or you could use a lower-value pot and a fixed resistor in series, to equal 10K total (or close).  A wild guess, because it's an audio taper pot, maybe a 2K pot and an 8.2K resistor.

[ricci]

Used without other stomp boxes everything is ok but because of the power supply I used an ICL7660S CPAZ that I fixed (I tried 10) together with the two 47uF capacitors on a very small pcb but even if I short circuit pins 1 and 8 I feel the famous hiss that decreases or goes to zero if I approach my hand or if I touch some wire or if I change position to the pcb, while if I decrease the gain from maximum to zero, the hiss increases more and more. With all ten ICL7660s the hiss always behaves the same, so I don't think they are fake.

[willienillie]

I'm confused.  I thought you built the "upside down" PNP version with negative ground.  But a few posts up you mentioned using a charge pump with the OC44.

[ricci]

I confirm, i built a PNP negative ground with OC44 but since the final purpose is to insert it in the daisy chain together with other pedal effects, i followed the advice I read here

https://www.electrosmash.com/dallas-rangemaster

where the PNP positive ground is good only with the battery and not with an external DC adapter which causes short circuit if put together with other pedals with negative ground, so i built a PNP Negative Ground but reading the article, it seems that with this version you can hear various noises and to eliminate the latter is recommended the REAL version that uses a MAX1044, which I tried but since I didn't get the -9V, then I used a 7660S which all guarantee that it eliminates the hiss which is there anyway.

[ricci]

A little while ago i tried the RM with negative ground, without other pedals and with my 1-Spot, and in fact i heard a noise that sounded like the ticking described in the article linked above but i had not yet tried to insert it in the daisy chain together with the other stompboxes, so i first checked in daisy chain without charge pump, assuming that i would have suffered the ticking and instead no ticking but i hear ... sssssssssssssssssssss ... typical noise when increasing the treble of an equalizer ....

Can this sssssssssss be reduced ?

[ricci]

Unfortunately, the basic hiss is also present with the AC128, OC84 and BC32, a real disaster. Apparently, it sounds quiet with moderate amp volume, but as soon as I get half a point up it's really a disaster.

[Big Monk]

Unfortunately, the basic hiss is also present with the AC128, OC84 and BC32, a real disaster. Apparently, it sounds quiet with moderate amp volume, but as soon as I get half a point up it's really a disaster.

Have you tried positive ground and a battery?

I know my NPN Rangemaster has no hiss even at top volume. I use a regulated power supply feeding all my pedals.