Is it possible to make a hiss-free Rangemaster style treble booster?

[nickfox]

The title pretty much says it all. My favorite pedal is the treble booster. I've built a rangemaster clone and bought a good quality rangemaster clone. They both have about the same level of hiss and they both were using nos mullard oc44s.

I'm just trying to figure out if it's possible to build something similar that I can use for recording and is quiet.

Please let me know your thoughts and direct me to resources that can teach me how to build really quiet pedals.

thanks
n

[idy]

The Rangemaster's hiss comes from its germanium transistor, they leak. Even with no signal on the base they act as if a small random signal was there. So, you can: test ge transistors for low leakage, buy modern russian germanium with low leakage, or try the various ways that a none ge circuit can mimic the properties of the Rangemaster. Any booster with a too-small input cap and too-low input impedence could be close enough.

[nickfox]

The Rangemaster's hiss comes from its germanium transistor, they leak. Even with no signal on the base they act as if a small random signal was there. So, you can: test ge transistors for low leakage, buy modern russian germanium with low leakage, or try the various ways that a none ge circuit can mimic the properties of the Rangemaster. Any booster with a too-small input cap and too-low input impedence could be close enough.

thanks. Can you please give me a link to a russian germanium on ebay that you would use.

n

[Electric Warrior]

OC44s usually leak very little. I've tried leakier types in this circuit and they weren't any hissier..

[thetragichero]

is the hiss at a frequency that's useful for guitar or could you tack on a low pass filter at the end?

[nickfox]

is the hiss at a frequency that's useful for guitar or could you tack on a low pass filter at the end?

I'm not really sure what the frequency is. I'm really hesitant to add something to the circuit to make up for the circuit's shortcomings.

I've been looking at some GE transistors on small bear. There is one there that might be a good candidate. The P416B.

It says it has practically no leakage. Does this equate to no (or less) hiss?

http://smallbear-electronics.mybigcommerce.com/germanium-transistor-russian-p416b/

n

[willienillie]

I used a 2SB175 in mine, fairly low leakage.  It probably has some hiss but not enough for me to notice.  Battery only like all of my positive-ground builds.  I used metal film resistors which must help some too.

[idy]

The small bear russians are as good a bet as any. Is the experiment worth the $3+shipping... well you'll have one (or 3) good ge trannies.

Mine I got years ago by the box... all the russians seem to come in many varieties, suffixes for gain... until you need 50 I would buy a few from small bear. Not sure if the russian ones come from actual bears or not...

[PRR]

> could you tack on a low pass filter at the end?

He wants "treble boost". A treble cut on the end probably spoils the effect?

There is hiss EVERYWHERE. The universe seems random down to its least pieces. Then you apply "boost", hiss comes up. Then you apply "treble boost", you get more hiss and where the ear hears it best. It's gonna hiss!

Hiss everywhere but old Ge parts hiss more than natural law predicts. This is only loosely related to leakage. The real leakers probably hiss bad too. The low-leak parts *may* hiss less. At the limit a Ge transistor will leak more than an Si transistor but the hiss may be comparable. However this varied ALL over the place as the technology improved and as factories had good/bad days. (And because in the heyday re-sorters would go through barrels of B-grade parts cherry-picking ones which were useful for something.)

Your primary defense against hiss is to keep your signal level high. Hot pickup turned full-up. If you also want treble boost, first look at your cable. 30 feet of cable off the guitar will suck the high-highs right out. To then try to boost them back is pissing against the wind.

[thetragichero]

so if the hiss were above say 5khz, which is about the limit of most drivers intended for use in guitar amps, a lpf centered around there could have little to no effect on toanz
i think he mentioned for recording purposes... if you've got guitar recorded on your daw with unacceptable levels of hiss determining if it's constrained to a frequency band that s useless for guitar needs or if it's wideband is relatively trivial... my ancient version of pro tools came with a 7 band eq that includes hpf and lpf options
i'm not suggested that this is a silver bullet but on the spectrum of things to try this has got too be the quickest/easiest one to rule out

[MaxPower]

Runoffgroove have a project which is supposed to sound like a rangemaster without the hiss. I breadboarded it and it didn't have any hiss. Don't know if it sounds the same as a rangemaster though.

Edit: D'oh! Maybe it's an AMZ project, not ROG?

[PRR]

> if the hiss were above say 5khz

Then very little >5kHz hiss would come out the speaker. (If you bypass the speaker, you do want a top-cut for this and other reasons.)

> for recording purposes... ... pro tools came with a 7 band eq....

I don't know ProTools. But there are two tools you should look for.

* Noise Gate. When the music fades, cut the audio. This is a heavy trade-off between chopping the tails of string decay and reverb, or passing most of the hiss. But it is simple and should be cheap, both to buy/use and in terms of load on the CPU.

* Noise cancellation. You show the tool a piece of "silence", raw hiss. You say "I don't want this sound". Then put it in Process. It nulls the hiss but lets the non-hiss sound go through. There is much to go wrong here. Chopped tails. Warbled fades. Small details, especially un-pitched finger-slips, may get taken out as hiss. And it is heavy on the CPU. But I have pulled-out listenable music from 78s that were more hiss/scratch than music. Apparently this does not come-with PT, you have to get a plug-in. I'm thinking the best plugins won't be free/cheap.

[bluebunny]

Edit: D'oh! Maybe it's an AMZ project, not ROG?

ROG Omega?

[amptramp]

I am not a fan of the way the Rangemaster boosts treble.  The pickup has a large inductance, on the order of 3 to 5 Henries, so if it goes into a low resistance, this kills the high end in an effect known as "tone sucking".  The input impedance of the Rangemaster is set by the parallel resistance of the 68K resistance to the emitter supply, the 470K resistance to the collector supply and the input impedance of the transistor base.  (I call it emitter supply and collector supply since both genders of transistor have been used and this applies to both.)

To counteract this, they use a small 5 nF input capacitor so only the highs get through.  The low input resistance reduces the resistive voltage noise but the low input capacitor keeps the output resistance of the guitar from adding much in the way of parallel resistance so you cannot simply turn the level control on the guitar all the way up so you only get the pickup resistance - the capacitor isolates it.  The original version did not have pulldown resistors on the input or output so there is no way to determine what the worst case would be - the output capacitor may go into a high resistance or a low resistance and the lower the resistance, the more the bass is cut (giving the effect of a treble boost).

To reduce noise, I would go with a Tillman or other quiet full-range amplifier and after boosting the signal and reducing its impedance to a known level that does not vary, then I would do the frequency shaping.

There are other possibilities - there are noise reduction circuits that sense the signal level and reduce high-frequency response when the signal level drops.  Since hiss is most noticeable at low signal levels, it cuts the treble when there is less signal.  This circuitry has been around since 1936 when it was introduced to RCA record players that were part of console radios:



This is a two-tube circuit that was mounted as a separate chassis within the radio (which had separate chassis for the power supply / push-pull 6F6 11 watt output amp section and the radio tuner section) and it operated like this:

The 6AV6 is a voltage amp with a rectifier on the output to give an envelope of the incoming audio level averaged over a short time constant but longer than an audio cycle.  The filter is two identical sections with a lowpass cutoff of 67.8 Hz.  This output goes into a 6BA6 variable-gain reactance tube that multiplies the value of the 27 pF grid to plate capacitance and puts it across the output.  Since everything here is high impedance, the small capacitor with the large and variable gain of the remote-cutoff pentode allows a large variation in high-frequency cutoff.  This does not have the obtrusive sudden cutoff or multiple cutoffs of a noise gate - it reduces the lowpass frequency linearly as the level goes down.  This circuit could be translated into a FET version without too much change and would make a nice upgrade to a noise gate.  An 83 year old circuit definitely has some mojo working for it.

[nickfox]

I just wanted to update you guys and let you know what I've done so far. I ordered a handful of russian transistors from small bear. I got an MP21A, MP42B, P416B (80-120 gain), P416B (70-79) and a sylvania 2N229 (not russian but i just thought an nos sylvania was really cool).

It's my little russian transistor starter pack. I'll soon see how quiet they are compared to my oc44.

n

[tubegeek]

* Noise cancellation. You show the tool a piece of "silence", raw hiss. You say "I don't want this sound". Then put it in Process. It nulls the hiss but lets the non-hiss sound go through. There is much to go wrong here. Chopped tails. Warbled fades. Small details, especially un-pitched finger-slips, may get taken out as hiss. And it is heavy on the CPU. But I have pulled-out listenable music from 78s that were more hiss/scratch than music. Apparently this does not come-with PT, you have to get a plug-in. I'm thinking the best plugins won't be free/cheap.

This effect is available in the stock plugins with Reaper, an excellent inexpensive DAW. Also, never give Avid any money.

[nickfox]

Edit: D'oh! Maybe it's an AMZ project, not ROG?

ROG Omega?

Thanks. I had a look at that omega project. It looks interesting. I'm going to wait for my russian transistors to get here and see how they sound (and hiss). If they hiss to much, I'm going to look at this project.

n

[MaxPower]

Had a look through my notebook and indeed it is the ROG Omega I was thinking about. Never used a rangemaster so I don't know how they compare but the Omega is hiss free.