Tone Bender MKII mojo

[Electric Warrior]

first off, I hope discussing MKII tweaks is not against this forum's rules. If it is, I'm terribly sorry. please feel free to delete this thread in that case.


I'm planning to build an MKII soon, but I'm not sure about some details.

This is the layout I'm using:

layout.png (36.84 KiB) Viewed 6533 times

It's based on a layout that Chris Brown posted over at diystompboxes.com.
I've already changed the resistor values to OC75-Bender style values (spent hours comparing photos of different MKII variants to double check if they're right).
The capacitor values are rather hard to make out in the pictures I've found. Are the values in the layout in the right ballpark?

I have several Philips OC75 and OC76 transistors as well as some Matsushita 2SB172s. Any recommendations regarding hfe/leakage selection? 70/70/100 seems to be popular and I've got OC75s in that ballpark. Q1 should be medium leakage, while Q2 should be low, right? Any different opinions?

then there's the bias thing... many people recommend to bias Q2 and Q3 like a germanium fuzz face and Q1 as if it was a Rangemaster (collector voltage of Q1 around 7V, Q2 around 0,5V and Q3 around 5V) and I can see why they do it, as the circuits are rather similar. but is that really what I should go for?

could anybody help me with this, please?

[Creepyfingers]

Yo

Your ears are very important when it comes to biasing...

--Brad

[Dragonfly]

Yo

Your ears are the most important thing when it comes to biasing...

--Brad

Fixed.


I would suggest to the OP that he build the circuit on the breadboard, check voltages, make adjustments, etc BEFORE committing it to vero board. The TB MKII is an amazing sounding circuit when built correctly, and a freaking horrible sounding circuit when done wrong. Either you test it on a breadboard and "tweak", or you build a hundred MKII's to discover some of their "secrets".

Best of luck.

[Electric Warrior]

I will use sockets for the transistors and some trim pots to find the resistor values I like. The problem is: I have no clue what a good tone bender is supposed to sound like with my rig.

[Dragonfly]

I will use sockets for the transistors and some trim pots to find the resistor values I like. The problem is: I have no clue what a good tone bender is supposed to sound like with my rig.

Thats where your ears come in.

In the immortal words of Joe Meek ... "if it sounds good, it is good".

[Electric Warrior]

or "all you need is ears" (George Martin)

[Electric Warrior]

updated layout:

mk2layout.png (34.4 KiB) Viewed 6323 times

[Electric Warrior]

parts:

parts.jpg

quick layout test (don't worry about the wrong resistor values) - maybe I should have chosen smaller resistors, it might have fitted a B-sized enclosure... but these 2 watt metal films look so sweet...

layouttest.jpg

[tatter]

If you test all your transistors first on breadboard you won't need the sockets (which spoil the look a bit i think) then you could just solder the transistors directly. Just make sure you solder them quickly or you'll damage the transistors.

If you're using the original layout may as well go the whole way!

[Electric Warrior]

true - but I would have to buy a breadboard and I'm short on money
if it turns out that I'm sure that I really like the transistors I might just solder them to the board..