DIY Rangemaster

[sekim]

Just a few comments on the Range Master that may be useful to anyone wanting to build one.

I evaluated a number of the Russian "flying saucer" case germanium PNP with hfe from 20 to 95 and the different part numbers with similar hfe all sound the same to my picky ears. They are all very quiet for germanium and there is no audible hiss. The stability of these is good for germanium devices.

I tried a prototype with the negative ground mod and it sounded horrible (probably due to guitar cables with high capacitance). Sounds great with a battery setup as negative supply. Also sounds great with the MAX1044 negative supply chip in high frequency mode, which is what I settled on. Also, don't buy the MAX1044 from Chinese suppliers on EBAY, they're fakes and do not work right. I found out the hard way and then bought from Mouser and all is well now.

Have yet to try Russian npn germaniums, and probably won't since this batch of pnp's sound fantastic. But if you don't already have pnp's you want to use, I would suggest trying the russian npn's based on how good these pnp's are.

As for hfe and bias points, this is really a matter of preference imo. The mid 80's to low 90's hfe range with -7vdc bias is a classic sound with plenty of crunch and plenty of gain. Very responsive to guitar vol and tone settings and very fun to play thru for the guitar hero sound that is on countless records.

But I also discovered when I auditioned my russian germaniums in the prototype circuit (and rebiased them), the 45-60 range is very nice as well, not quite as crunchy, but still plenty of gain. Experienced players who want a bit more articulation will probably love these. Also very responsive to guitar vol and tone controls.

Surprisingly, I really like the 20-ish hfe biased at about -6 to -6.5. Its a different animal, but place a comp after it and its a relatively clean chime that can go to slight crunch with plenty of sustain and still has the germanium mojo. No comp and it's this wonderful trebly spank on rythm. Both are sounds you've heard on a lot of famous records. And as with the hfe 50-60, more experienced players are probably going to really like these as an additional flavor. Also very responsive to guitar vol and tone controls.

Bottom line is any of the hfe ranges can be the foundation of a great sound. As for me, I ended up with a cool, warm and hot version and use them all.

[iainpunk]

hey, welcome to the forum!

really cool writeup, i personally like the same gain range as you, around 30 Hfe is my favourite range, but i use silicon transistors in reverse. gives a bit brighter crunch. another difference; i really like biassing right near 8.5v or so, that it clips nearly instantly.

cheers

[sekim]

Actually, my favorite is one I did with a 2SK170BL jfet. Ultra quiet and very articulate tone. I biased it on a scope similar to how a hfe 65 works at -7v. I imagine any decent jfet would perform similarly as long as you set up the bias resistors to show about 12K to the guitar.

Also worth mentioning how I managed to fry two of my genuine MAX1044. Long story short is that I am using a switching power supply for the 9VDC (sourced from either Digitech or Electro-Harmonix IIRC) and with the RM already plugged in and working, when plugging in another stomp box to the daisy chain power cable, a reverse spike from 9VDC down to close to zero occurs and that causes the MAX1044 to become unstable and fry itself. This is with V+ on the MAX1044 bypassed with both a 3.3uF electrolytic and a .01uF tantalum. So I added a 1500uF 10V to the V+ bypass and now it works fine under that circumstance. It would probably work with about 220uF or maybe even less, but don't want to fry another one just figuring out the min size. No such issue using an older transformer wall wart supply and daisy chain cable...

[mozz]

Thought there was going to be a list of what transistors you used.

[iainpunk]

really cool idea, a Jfet based range master.
i would remove the vcc to base resistor entirely, just have the gate at 0Vdc, and replace the bias pot with a 100k resistor. ill replace the source resistor with a bias pot, to bias it to a good tone, followed by an emitter follower (buffer) and a volume control.

ow, i forgot to say i also like the bias at 2.5v, at the other end near saturation, instead of near cutoff. gives a different kind of sound/vibe tho

cheers

edit:
try a BD139-10 power transistor for a range master, it has a range from 63 to 160, selecting from a batch would be wise

[GibsonGM]

Welcome to the forum, Sekim - nice writeup.  I like to use a RM with my Marshall 18 watt, real 60s mojo, very Pete Townshend.  Good to see some comparisons using trannies of different gains!

[mac]

really cool idea, a Jfet based range master.

https://www.diystompboxes.com/smfforum/index.php?topic=112798

mac

[sekim]

Thought there was going to be a list of what transistors you used.

Here you go in no particular order:

MP13B
MP16(backwards R, whatever that is in english)
MP42B
MP25
MP25B

Of the ones I received, there was a fairly wide range of hfe for any given prt number, though the MP25 were all lower hfe than the MP25B which is what the datasheets indicate.

[sekim]

Here's what I implemented for my JFET RangeMaster:





As you can see, slightly higher resistance seen by the guitar, with cap value adjusted accordingly. The input Z is what I settled on after prototyping to determine the amount of HF rolloff I wanted since unlike a germanium, the vol knob setting on the guitar does not affect the HF rolloff with a JFET RangeMaster. Also, the 1M pulldown on the input side is missing from the Spice sim.... Also, the 200K is a trim pot to adjust bias.

[sekim]

Welcome to the forum, Sekim - nice writeup.  I like to use a RM with my Marshall 18 watt, real 60s mojo, very Pete Townshend.  Good to see some comparisons using trannies of different gains!

One of my gigging amps is a 1990's DSL20 that I did a few mods to to make it more to my liking. Subbed in a 1uF cathode bypass for the clean input stage (I think it had a 22uF stock) and lowered the gain on the drive channel way back and reduced the HF rolloff on that channel. And did an English made V30 in it. Great little amp now. I also had a smashing success doing similar things to a Laney VC30. Seems like the tube amps from that period were all designed with stupid high gain on the drive channels and super bassy sound on the clean channels. I guess that is what sold on the floors of Guitar Centers, lol. But both cr@ppy tones easy enough to correct and you end up with a great amp for not much $$$. My "sonic control" for reference was prime electrical condition 1966 Fender Deluxe (non reverb) which really served its purpose well as a sonic reality check when modding the other amps. They both came out so well, I ended up selling the Deluxe for $1800 when I had a total of $140 invested in it...

[mac]

As you can see, slightly higher resistance seen by the guitar, with cap value adjusted accordingly. The input Z is what I settled on after prototyping to determine the amount of HF rolloff I wanted since unlike a germanium, the vol knob setting on the guitar does not affect the HF rolloff with a JFET RangeMaster. Also, the 1M pulldown on the input side is missing from the Spice sim.... Also, the 200K is a trim pot to adjust bias.

Remember to add a "Guitar Mic Model" in your simulations.
After the Voltage Source add an inductor with typical guitar mic inductance and resistance, say 3H and 5K, the tone control, the volume pot, and the cable capacitance of about 220-330pf.
Without all this you won't get the peaky response of a RM.

mac

[sekim]

As you can see, slightly higher resistance seen by the guitar, with cap value adjusted accordingly. The input Z is what I settled on after prototyping to determine the amount of HF rolloff I wanted since unlike a germanium, the vol knob setting on the guitar does not affect the HF rolloff with a JFET RangeMaster. Also, the 1M pulldown on the input side is missing from the Spice sim.... Also, the 200K is a trim pot to adjust bias.

Remember to add a "Guitar Mic Model" in your simulations.
After the Voltage Source add an inductor with typical guitar mic inductance and resistance, say 3H and 5K, the tone control, the volume pot, and the cable capacitance of about 220-330pf.
Without all this you won't get the peaky response of a RM.

mac

I only wanted to model cutoff and approximate bias behavior in isolation and for comparison purposes since I had no need for a prediction of what the guitar/RM as a system would sound like.