A bit of a classic - the MK1.5 Tone Bender. Some great phots and background information here on Fuzzboxes.org and some great video demos below - who better than Ant Macari to talk Tone Benders.
Note that some earlier versions carried a 500k volume pot, instead of 100k resulting in more bass - ultimately bringing it closer to a Fuzz Face.
One of the main differences to a Fuzz Face is the use of OC75 transistors. The key to this is that they are very leaky, and will not bias the same way as a regular fuzz face. Do not try and bias it like a fuzz face with 4.5v on the collector of Q2 - it will be around 7 or 8 volts.
SOLA SOUND MK1.5 TONE BENDER - ORIGINAL VERO LAYOUT (0.15" / 3.8MM)
I've built one and biased it to -4.5V like a Fuzz face - guilty! It sounds like a Fuzz Face with more bass due to the 4u7 input cap. I used some cheap transistors in the Fuzz Face gain buckets, can't afford OC75s. Will revisit the circuit soon.
ReplyDeleteI know - OC75 are insanely priced. I bought mine from someone locally for a few dollars each. That supply is no longer available :-(
DeleteYou can still get transistors of a similar gain and leakage for a decent price.
BTW where do you buy 0.15" stripboard?
ReplyDeleteI buy it from RS Components in Australia. They’re also in the UK.
DeleteSearch for vero and look for the one with 3.8mm hole spacing. They only carry one size in stock.
Thank you!
DeleteDAM uses a trick with the OC75 (I think it will help with others leaky transistors) putting a 47k (measured to be near 43k) from B of Q1 to ground to help biasing.
ReplyDeleteThanks for the tip!
DeleteThanks for the tip!
DeleteShort question, I always thought that you could use transistors with low leakage in this circuit, the same with the Vox Tone Bender, right?
ReplyDeleteOh, and something else. Is the cut (7 to the right, 5 down) necessary?
ReplyDeleteIt’s not necessary - I’d actually add another cut on 3,3 to keep the signal from the collector of Q2 away from the input. I sometimes add cuts to shorten the length of vero strips. Less chance of stray capacitance, signal bleeding across strips or picking up noise.
DeleteYes you can use low leakage transistors, but part of what makes it a little bit different to a fuzz face is the leaky transistors.
Right, thanks! And the same for the Vox Tone Bender?
DeleteThe Vox Tone Bender used a pair of low leakage transistors, the first in the 80-100hfe and the second one are lower than usually people think, more in the vein of 30-50hfe, at least the ones carrying SFT transistors. The OC76 can vary a lot more, I have a Mullard in the 36hfe and Valvos in the 150-200hfe. For me the first sound a lot better and a lot more similar to the YouTube vids. The Vox Tone Bender is one of the usually forgotten but a psych machine.
DeleteAwesome advice. Changed the transistors in my Vox TB built accordingly (Q1: 90 very low leakage, Q2: 45-50 very low leakage) and with Q1 0,7 V and Q2 6,4 V it sounds as I hoped it would. Thank you! The only thing I will change in the future is using a reverse log pot for Fuzz instead of a linear.
DeleteThat was me, I forgot to log in.
DeleteI am glad it worked for you too! The C1K pot helps to open a bit more the range on the fuzz pot. It's not perfect but a good improvement.
DeleteLike all vintage pedals, original 1.5s are all over the place in terms of tone (at least according to the videos I've seen) but I think it's supposed to sound brighter than a Fuzz Face despite the larger input cap. I think it has to do with the fact that Q2 is typically biased at around -7V as opposed to -4.5V like a Fuzz Face. This makes sense since it's the same voltage for Q3 in the Tone Bender MKII, which is a 1.5 with a transistor stage in front of it.
ReplyDeleteYes! Back in the day they usually didn't take half the time we take to tune the fuzzes for what we consider "the best tone possible".
DeleteI will recommend in the MK1.5 to add a bias trimmer or potentiometer. If not with leaky transistors during the summer time the voltage can increase until almost 9V. (And this is the reason for the appearance of the MKII, a bunch of dissatisfied costumers claiming that their fuzz had stopped to work under a sunny day in a hot summer)