Just un-gooped my Tonebone Classic to find diode clipping !

Post by **mxrmxr** » 07 Mar 2009, 20:00

So much for natural tube distortion

No wonder they gooped it

Dirk_Hendrik · Post by **Dirk_Hendrik** » 07 Mar 2009, 20:30

for those who start to scream "Q..", please think again, silkscreens can be wrong on purpose.

mxrmxr has shown me that the schematic I've drawn up of the tonebone classic some 4-5 years ago lacks a few components end therefore contains a flaw. I thank Mxrmxr for clarifying this. Swell job done, admiration for your guts to attack that goop

At the time I've limited myself to measurements for "the stuff under the goop" at that time. Since there's multiple diodes in series expected (waiting for mxrmxr's response) my DMM will not give readings in that case.

As for the full schematic (minus mxrmxr's findings), one may revert to DIYstomps and search for the whole discussion. Bottom line is I had the schem on my page for some 1.5 yrs when someone there started asking questions. The whole "legal" discussion took off and a day later Radial was in my mailbox asking me to take the schem down (and not asking nicely). Today I would not since there was no T-shirt involved. Three years ago I did and since I did so, that will remain so. If you have that schematic, feel free to post it. The clipping circuit is around that 68 k resistor and presumably clips to ground.

Ripdivot · Post by **Ripdivot** » 07 Mar 2009, 21:08

Here it is

Post by **mxrmxr** » 08 Mar 2009, 17:54

Here ya go

lolbou · Post by **lolbou** » 08 Mar 2009, 18:04

I guess you diserve the Degoop Doctor title, mxrmxr...

Can anybody show how are these SMD diodes implemented on the board?? I just can't figure out, even when tracing, I can't find the bridge rectifier...

Post by **mxrmxr** » 08 Mar 2009, 18:15

It is done with 3 of these configured as above.

lolbou · Post by **lolbou** » 08 Mar 2009, 18:21

3?

makes 6 diodes then? two more than for a bridge rectifier...

Or maybe these two are added to get asymmetric clipping in some way? Just guessing here... Thank you anyway!

Post by **mxrmxr** » 08 Mar 2009, 18:26

lolbou wrote:3?

makes 6 diodes then? two more than for a bridge rectifier...

Or maybe these two are added to get asymmetric clipping in some way? Just guessing here... Thank you anyway!

5 of the diodes are used in the above circuit. The remaining 6th diode is not used and is shorted out.

lolbou · Post by **lolbou** » 08 Mar 2009, 18:32

Thanks! It's strange to see such precautions to protect their once called "secret"...

Why didn't they use a SMD bridge rectifier? Did they thought people (or chinese copymakers or Zachary

) would X-ray their pedal and then used transistor looking diodes and wrong silkscreen?

bajaman · Post by **bajaman** » 08 Mar 2009, 19:34

They presumably did it to make people think there were three bipolar transistors or fets being used under the goop.
By the way have you noticed how the tube is configured

- as a paralleled cathode follower - absolutely NO GAIN whatsoever - a con of the highest magnitude - is the tube suppose to warm up the sound???? what bullshit.
I tried one of these overpriced pedals once - it was unremarkable to my ears.

bajaman

ps: thanks for blowing the mystery goop mxrmxr

bajaman

lolbou · Post by **lolbou** » 08 Mar 2009, 19:47

bajaman wrote: By the way have you noticed how the tube is configured - as a paralleled cathode follower - absolutely NO GAIN whatsoever - a con of the highest magnitude - is the tube suppose to warm up the sound???? what bullshit.
I tried one of these overpriced pedals once - it was unremarkable to my ears.

Dear! I didn't notice it... Just a buffer feeding the tone stack?

What's the point of having a doubled cathode follower by the way? Is it really needed to use a buffer to drive an active tone stack?

Ripdivot · Post by **Ripdivot** » 09 Mar 2009, 04:33

I had one of these pedals for a while and it sounded great with my setup. Changing the tube did affect the sound slightly but not drastically. It has a lot of tone shaping and I got a great brown sound out of it as well as a nice light crunchy overdrive. I sold it because I prefer to have pedals I build myself on my board instead.

culturejam · Post by **culturejam** » 09 Mar 2009, 04:51

Damn. That's messed up. But I suppose in the most technical terms, you really do get "tube tone", since the tone is filtered through the tube.

Not very scrupulous, however, in my opinion.

Does this thing sound any good? If so, maybe it would be worth the effort to work up a project for it...sans the superfluous tube, of course.

Pedalpusher · Post by **Pedalpusher** » 09 Mar 2009, 15:57

culturejam wrote:Damn. That's messed up. But I suppose in the most technical terms, you really do get "tube tone", since the tone is filtered through the tube. Not very scrupulous, however, in my opinion.

Does this thing sound any good? If so, maybe it would be worth the effort to work up a project for it...sans the superfluous tube, of course.

They already did. It's called The Bones series. If You run them through a tube amp it's the same thing IMO.

lautmaschine · Post by **lautmaschine** » 09 Mar 2009, 21:18

The tube does warm the pedal... physically that is.

And it offers glowing eye candy.

I seem to recall this revelation being discovered over at the other forum some time ago. Tubes and diodes aside, the tonebone is a needlessly complex and disappointing pedal with little character.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 10 Mar 2009, 09:36

I'e said it once, I'll say it again.

The tube is not for generating distortion. The tube, in this application, works as a filter with a somewhat "tubey" response. I wish that people stopped thinking of filters as a building block that affects frequencies only. A similar thing is done by Fender in their "1 preamp tube" amplifiers like the rocpro and the performers where the two halves of a 12AX7 are used as diodes. (combined with diode clipping).

Essentially these are applications that bypass the BK butler patent.

An then,
Is diodeclippng suddenly not allowed? Tell that to the Mesa fella's when they designed the V-Twin. Or to the Hughes&Kettner guys designing the Tube factor. Please don't be too puritannical. Denis Rozon has made up some nice tonebones and deserves credit for that.

lolbou · Post by **lolbou** » 10 Mar 2009, 10:14

Dirk_Hendrik wrote:The tube is not for generating distortion. The tube, in this application, works as a filter with a somewhat "tubey" response

You mean this cathode follower actually change the response? I though it was a unity gain gevice, with quite low distorsion of the sound... So it's not a driver at all? I don't see the way it changes the response...

Lots of questions indeed, but I'd like to correct my beliefs...

briggs · Post by **briggs** » 10 Mar 2009, 12:09

What a great find. Very well done mxrmxr, it's great to see everyone taking on the goop! An interesting diode config, all though, all I can see is it basically creating symmetrical clipping through 3 diodes to ground on each wave portion.

lolbou · Post by **lolbou** » 10 Mar 2009, 14:17

briggs wrote:all I can see is it basically creating symmetrical clipping through 3 diodes to ground on each wave portion.

I would go for asymmetrical, since 5 of them are linked, the sixth one is not connected...

cbriere · Post by **cbriere** » 10 Mar 2009, 14:29

same diode arrage inside this hi-end preamp...

ooops,,,,

http://www.drtube.com/schematics/marsha ... -61-04.pdf