Reverse engineering Beano bost

[Banjan73]

Hi.
I just got finished drawing my beano boost copy (reversed engineered).
Can anyone confirm that I am into something here?

[antonis]

R3 / RV1 lug3 junction should go to GND..
R2 may be deleted.. (i'm not sure about its role as it's drawn..)

[Banjan73]

Ah!
Nice spotted. I had to ohm the thing to verify, but you are correct. Both R2 and R3 goes to ground via one leg of the potmeter (soldered to chassis of the potmeter).

[Banjan73]

So, more like this then?

[Banjan73]

Can`t say I understand R2 here either, but it looks like that in the pedal...

[duck_arse]

if C1 is the output cap, it might need a pulldown resistor - R2, fer inst.

[Banjan73]

Aha!
Yes C1 is output cap.
Ok. Thanks for input. Anyone knows if a AC128 tranny is an ok replacement for the CV7003? Much easier and cheaper (i think) to get that one here in Norway.

[antonis]

IMHO, 10nF cap shouldn't need pull-down resistor, especially in case of 3PDT switch wired with OUT grounded when by-pass, but let it be there..

[Wavelength]

All,

I have the mini with power supply jack. The input caps are 6800pF, 6800pF and 0.015uF. 9V into diode->circuit.

CV5713 which I guess is a OC71 type Mullard.

I make my treble booster with OC140/950 germanium NPN from Mullard hfe ~100.

The Beno input impedance is 15.3K, the NPN are a little higher so I may rebias mine as it is at 22.6K.

I did an interesting study on Treble Boosters it's further down the list. Pickup type will change the -3dB point pretty much. I am going to work on this a bit more but have to ship some amps today and tomorrow.

The 0.01uF output should require a pull down or else it will pop with some other pedals when engaged.

Thanks,
Gordon

[Banjan73]

All,

I have the mini with power supply jack. The input caps are 6800pF, 6800pF and 0.015uF. 9V into diode->circuit.

CV5713 which I guess is a OC71 type Mullard.

I make my treble booster with OC140/950 germanium NPN from Mullard hfe ~100.

The Beno input impedance is 15.3K, the NPN are a little higher so I may rebias mine as it is at 22.6K.

I did an interesting study on Treble Boosters it's further down the list. Pickup type will change the -3dB point pretty much. I am going to work on this a bit more but have to ship some amps today and tomorrow.

The 0.01uF output should require a pull down or else it will pop with some other pedals when engaged.

Thanks,
Gordon

Thanks for info, Gordon. Yes, I have seen that tread. Gonna read my way through it now.
As by now, i have the following PNP`s at hand:
2SB459
AC126
AC132
2SB113
2SA354

So, I am wondering which of these is the best to replace that CV7003 / OC44?

Any thoughts?

[Wavelength]

Banjam,

I have a bunch of the Toshiba's and have done a few TB with those. Toshiba makes some really nice transistors in their day. Some of their JFETS are the best ever made.

But I think one deal with any transistor change is this input impedance and the effect it has on the guitar pickups (and cable I guess). I am behind in everything right now but I hope to pack up these two amps and kick them out today so I can get back to this thought.

I think the big question here is... was the OC44 really the best option or is that what they had sitting around? If you look at the Electrosmash page they basically go through the math with a OC44 hfe = 100 and so forth. They get a 12K input Z. The Beano boost is like 15.3K and mine is 22.6K. Now does that input Z have and effect on the sound or just change the roll off point?

I am going to change my bias point today which will lower the input Z. Right now sonically the thing sounds way to thin indicating to me the roll off point needs to move down. Have both dogs at the office today and Barley will howl like crazy if I go down this rabbit hole so maybe this afternoon I can revist this before UPS shows up.

Thanks,
Gordon

[Banjan73]

Think you have some good points there, Gordon.
God knows if they chose the OC44 for sound or just for convenience. When thinking about it, I think they as you say, just chose some more or less "random" transistors. This was not the boutique era, so I give my wote to that conclusion.
I just had a glance at the electrosmash Rangemaster circuit, and its very similar to the beano boost. One big difference is the input impedance, though. The beano boost has that 1M input resistor to ground. So, when you mention 12-20k of input impedance, its not relevant for the beano boost.
I have more or less decided to use the AC126 or AC132 trannys in my build. Just waiting for some components from China...

[Wavelength]

Banjan,

The 1M is a pull down for the input so the pedal doesn't pop when switched on or off. The Electrosmash assumes an OC44 but it's all math and as we know germanium is all over the place.

The Beano Boost I have with the CV5713/OC71 has an input Z of 15.3K. Mine was 22.6K until I went through a boat load of math and cap values and changed the bias point and brought it down to 17.224K. This allowed me to use the 5600pF (Mial) in stock. This also gave me a 1.65KHz -3dB roll off point when using my sound card (DragonFly Black 0.4ohm output Z).

I didn't get to try too many guitars yesterday but both pedals (both Mullard OC variations, mine OC140) very similar on all my T types. I need to try gold foil and P90 later. On humbuckers (Lollar Imperial) there was a slight difference in sound. I am going to run tests with a 10K pot in series later today as we found in my other thread this changes the -3dB point.

The beano has a lot more gain than mine. 0dB reference beano 10 oclock, mine noon.

I am glad I added that shunt low dropout regulator as my noise was easily down a boat load compared to the beano.

I am using an output transformer on mine and the 10K pot on the output.

More on my thread later this morning.

Thanks,
Gordon

[Wavelength]

All,

Ok you can read all about my screw ups in the measurements in my thread up here as well. But in general the Beano has an input impedance of 18.04K and my Nitrous T 17.832K.

I changed my bias resistors to lower my input Z from 470K/68K to 200K/39K which lowered mine from 22.63K to 17.832K. Now granted I am using an OC140 NPN Mullard and since I have a transformer 10K:10K on my collector and 10K pot on the secondary, the OC140 is pulling 0.4ma which is 2x the standard Rangemaster.

But I think all these transistors (germanium) are going to give you different impedance. Maybe OC44 are 12K, the Electrosmash is just calculated so who knows.

My sound as I said in my thread was very similar with all my single coils. But Humbuckers because of the higher driving impedance the Beano sounded better since it's -3dB point (center position) was 785Hz and mine was 1020Hz.

Anyway read on...
Thanks,
Gordon

[Wavelength]

Additional info...

I was looking for some 2N404 for something else and found a bunch of OC44's here look to be Mullard glass units. Really nice tested great low leakage.

I also found a bunch of OC71's. I can say the CV5713 in my Beano is not equivalent to an OC71. I tested like 28 OC71 most had hfe in the 35-45 range. All the OC44's I have tested in the 99-150 range. I would say the CV5713 is more of a OC44 than an OC71. That just from the amount of gain this thing has.

Of course the hfe will have a difference in the input Z which then will have a difference in the the roll off point. So take that all into consideration. hfe/transconductance = input Z, transconductance is a factor of current so everything is going to change that -3dB point with the standard Rangemaster setup.

Thanks,
Gordon

[Banjan73]

So.
Finally I have "finished" this project, that means I will probably tweak the caps in the filter switch after a little more testing.
I was originally going to use an AC126 transistor, but the one I had was a noisy son of a b@#*. So, i just put in an Hitatchi 2SB259 (beta of 180), and that worked perfectly! I have to test the thing a little more, but it is really promising.

[Banjan73]

The original vs the copy:

[Banjan73]

Going to update the schematics tomorrow to correspond with the final thing..

[Rob Strand]

Going to update the schematics tomorrow to correspond with the final thing..

Move  RV1, C1, R2 to the collector of Q1 then wire the grounds of those parts to the ground at C6, R5.

Also, draw R3 downward from C4 with the ground at the bottom.

It doesn't change the schematic but it will make the circuit a hell of a lot easier to read.

[Banjan73]

[/quote]

Move  RV1, C1, R2 to the collector of Q1 then wire the grounds of those parts to the ground at C6, R5.

Also, draw R3 downward from C4 with the ground at the bottom.

It doesn't change the schematic but it will make the circuit a hell of a lot easier to read.

[/quote]

Ok.
I`ll keep that in mind ;-)