BENSON: Preamp, Dylan159 Modded

This is a modded Benson Preamp by Dylan159 on Freestompboxes.  Dylan has taken the original and simplified it but has retained the overall character.  Quite a detailed explanation via the link above, including a schematic, LTSPICE model traces, audio and his vero layout.   What a solid effort.

For me, this is useful, as it has a standard pot value for the bass control, rather than a hard to find B2M pot.

BENSON PREAMP - MODDED - VERO LAYOUT

note: pin 1 volume to ground

MARSHALL: Blues Breaker

Nothing to see here - just a Marshall Blues Breaker...   quite the classic today, bit did not do well when it was released.  

MARSHALL BLUES BREAKER - VERO LAYOUT

JOHN HORNBY SKEWES: Hybrid Zonk Machine, 0.15" Vero Layout

This is the original layout for the Hornby Skewes Hybrid Zonk Machine (Silicon / Germanium). 

Unfortunately, the trimmer needed to be a different size for the layout, so I had to make a strange triangular marker.

HORNBY SKEWES HYBRID ZONK MACHINE - 0.15" VERO LAYOUT (ORIGINAL)

Full details available here, which is my point-to-point layout for the Matsumin Valvecaster.  Original values are used below.   

MATSUMIN VALVECASTER - TAG BOARD LAYOUT

YAMAHA: OD-10MII Overdrive

Like Tube Screamer overdrive, but hate the Tube Screamer mid bump and lo-cut?  Then the Yamaha OD-10MII Overdrive might be just the thing for you.  

Schematic at Aion 

YAMAHA OD-10MII OVERDRIVE - VERO LAYOUT

v2 corrected

VIDEO DEMO

DEATH BY AUDIO: Fuzz War V1

The Death by Audio Fuzz War V1 is notoriously hard to build by all accounts, which makes me want to try.  Might breadboard this one first to sort out any bias issues before committing to the board.  

DEATH BY AUDIO FUZZ WAR V1 - VERO LAYOUT

TRANSISTORS: Soviet Transistor Pinouts

 Just a little reference to Soviet-era transistor pinouts.   

SOVIET TRANSISTOR PINOUTS

note:  in addition to potentially different pinouts, some Soviet-era transistors can have the case connected to the base - which is not good if it touches anything else.  The dot on the case usually marks the emitter, not the collector as often found on European transistors 

KORG: MS-20 Filter - Rene Schmitz Version

This is the Rene Schmitz version of the MS-20 Filter, which is used in the later models.  I didn't include the CV control inputs, as I have no plans on using CV.

KORG MS-20 FILTER - VERO LAYOUT

KORG MS-20 FILTER - BUILD REPORT

This is a very particular sound, and while it doesn't have a lot of uses, it does do a screaming filter sound really well, and can go into oscillation.  It would be more useful with the frequency control running off an expression pedal - or in a synthesiser where it belongs...   

I would firmly recommend adding a volume control at the end, as this can really pump out some level, and/or do not place it in front of anything that is going to die if you feed it high input signal. 

Adding a single germanium diode to the pair of green LEDs or replacing a LED with germanium made a massive difference - I recommend trying this, as it tamed the beast somewhat.  Could pop it on a switch easily enough.  

I also added a 1uf on the input, as the original doesn't have a coupling cap, and I increased the output cap from 470n to 1uf, just because that's what I had on the input.  I have large 1uf caps on the layout, but I decided to use multi-layer ceramics to keep the size down.   The layout is quite flat, basically nothing is higher than the ICs.

Voltages are running at around +/- 17v instead of +/- 15v as that's the best I could do with the MAX1044.  I didn't exactly put in a lot of time trying either.

Note:  diodes and a 10k resistor are on the breadboard 

FRANTONE: Lo-Tone Classic Fuzz

I just found an old, nearly finished layout for the Frantone Lo-Tone Classic Fuzz in my files, so I thought now is as good a time as any to finish it.  After the D*A*M Sonic Titan, I thought I would see what else has an LM386, and this popped up.

Kind of unusual with the incredibly low input impedance for a guitar pedal - it’s about 10k.  Fran has designed some pretty exciting stuff, whereas I with approximately zero interesting things...  so I will not be too critical about this.   

FRANTONE LO-TONE CLASSIC FUZZ - VERO LAYOUT

D*A*M: Sonic Titan ST-07

This is as close as I could get to the original layout for the D*A*M Sonic Titan.   It's pretty much a JFET smashing the LM386 with level, but in the nicest possible way.  I've read a 10k level pot can brighten things up a little. Apparently, this was on some of the earlier versions.  

There's also a bit of discussion around how the tone control functions and interacts with the level control, resulting in the third layout below, using the Sonic Samurai mods.  Other issues include DC causing crackle down the line (no cap on the input to the FET) and 386 note decay issues. 

D*A*M SONIC TITAN - VERO LAYOUT

The original used a 2N3819 JFET - I've listed a J201 as it's the same pinout as some other common FETs, and I have a few and like the sound.

Notice any similarities between the layout above and the circuit from the datasheet below? David Main from, or who is D*A*M, mentioned that the Sonic Titan is a couple of circuits jammed together.  One is straight frodatasheet sheet, and the other is a standard JFET boost.

TITAN VIDEO DEMO

TRANSISTORS: Mullard Data Book 1965 - 66 & 1974 - 75 Excerpts

Transistor datasheets from Mullard for;

Germanium:    OC44, OC45, OC70, OC71, OC72, OC74, OC75, OC78, OC81 and OC81D

Germanium:    AC126, AC127, AC128, AC176, AC187, AC188

Silicon:            BC107, BC108, BC109, BC186, BC187

MULLARD DATA BOOK 1965 - 66

MULLARD DATA BOOK 1974 - 75

COLORSOUND: The Yellow Hybrid OC140 Tone Bender by Jake Rothman, 0.15" Vero Layout

All the details are listed in the previous post - this is a 0.15" version of the yellow Colorsound Hybrid Tone Bender.  

I did the previous layout on standard size vero, and after using 0.15" vero and tag board on a lot of builds recently, it just seems very tiny now, so I did another layout on a larger scale.

YELLOW HYBRID COLORSOUND TONE BENDER - 0.15" VERO LAYOUT

note:  the exact value of the zener diode at the time of posting this unknown

On the bench, waiting for an OC140 to arrive in the mail.  I've built another on regular vero with an AC127 (which sounds great).

Not exactly as per the the layout above, as I moved a couple of things around a little to fit more comfortably.  I'm also going to try a 47n cap in the tone section instead of 33n - 47n is found in earlier versions.

• 0.15" vero
• 1W carbon film resistors
• The orange caps are Philips
• 500pf styroflex caps instead of 470pf ceramics
• OA7 germanium diode
• Standard MKT caps in grey and white
• Q1, AT462 which is similar to a BC107
• Q2, BC109C
• Q3, will be an OC140 - once it arrives in the post
• Added 100ohm resistor to combine with a 220uf for power filtering, and a diode for polarity protection

COLORSOUND: The Yellow Hybrid OC140 Tone Bender by Jake Rothman

Such a lengthy heading...   I've been waiting to find out what was going on with this one, and it has recently been traced on the Pedal PCB forum.  There's also a great back story here, with some info on the Zener diode.

The schematic can also be found via the Pedal PCB link above. 

There are other earlier versions, including a PNP version using an OC75.  The OC75 version is very close to the OC140 version - although there's no diode involved in biasing the collector, just a 4k7 resistor (and obviously some different transistors on Q1 / Q2).  A couple of odd value resistors, like a 10ohm on the emitter of Q2.  I'm pretty sure I'm reading it correctly, but...  

The PCB is a Jumbo Tone Bender board with modified parts/values.   

COLORSOUND HYBRID TONE BENDER (2018 EDITION) - STANDARD VERO LAYOUT

note:  V3 germanium diode polarity reversed, fuzz pot changed to A100k

I'll get around to cleaning up the connections at some point, as they are a bit rough and will also add another diode for polarity protection - this was a quick solder job for testing.

It works....  sounds like a Tone Bender too.  Not a direct replication of the sound of a MKIII / MKIV, but the flavour is there.

  

I had to make a few substitutions as I did not have all the parts as per spec. 

• 5.1V zener diode, instead of the 4.7V (bear in mind the actual value has yet to be confirmed)

• AC127 instead of the OC140 - it's quite leaky, with a gain around 100

• AT426 instead of the BC107

• 100n instead of 10n, just because I wanted to, and it has been seen in earlier versions
  

• B25k pot instead of W20k
  

    

 

TONE POT SWEEP

The PNP version uses tropical fish capacitors, using a 47n cap instead of 33n, resulting in a slightly different sweep, with less of a dip in the mids.

ON THE SCOPE / FFT

Input signal:  440hz sine wave, approx 130mv TRMS

 

 

Q1 Collector  (AT426)

Fuzz set to 100%

C 4.4V

B 0.6V 

E 0.04V

Q2 Collector (BC109C)

Fuzz set to 100%

C 4.35V

B 0.6V 

E 0.04V

 

Q3 Collector (AC127)

Fuzz set to 100%

C 1.7V    (Traced pedal read 2.5V with OC140)

B 0.1V 

E 0.0V

 

Bass

 

 Treble

 Tone 50 / 50 Mix

 

Tone Bender MKIII, Q3 Transistor Comparison (OC71, OC75, OC81)

Now I didn't go as far as measuring and matching gain and leakage (as much as possible), but here's a comparison of a few Q3 transistors for a Tone Bender MKIII - all the same setting, just swapping Q3 on the breadboard.

Why?   I saw someone on Facebook poking fun at an eBay seller in Thailand over what they thought were fake OC71.  I bought some as the seller looked legit to me, as did the transistors -  so I tested them yesterday, and it turns out they are real, so I promptly ordered more.

Lines on a screen don't replace ears, but as you can see, they are quite similar.  There are definite differences in harmonic content, with the 2nd and 4th being the most obvious.  On the scope, the waveforms are very similar, with hard-to-pick differences.

I could talk about the sound, but it's very subjective... 

Unbranded OC71

Valvo OC75

Mullard OC81