Sola Sound - Tone Bender Mark I (1965)  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...

Re: Sola Sound - Tone Bender Mark I (1965)

Postby DrNomis » 05 May 2014, 22:33

LucifersTrip wrote:
DrNomis wrote:Q3, C=6.77V


should be ~ 8V



So apart from that voltage, everything else is okay?....... :hmmm:


I was reading somewhere that, for a Zonk Machine, the collector voltage for Q3 should be about 7V, seeing that the Zonk Machine circuit is very similar to the Mk I circuit, I was aiming for the same, or similar voltages, my guitars are at the music department at uni so I'm going to see if I can bring my strat home and try out the breadboarded circuit and see how it sounds, might even do a soundclip, thanks for the tip Lucifers Trip..... :thumbsup
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby jalmonsalmon » 06 May 2014, 00:21

I have tried making a mk1 on a breadboard, have not measured voltages or anything but so far I am getting a bad screaching mess with this circuit.
What schematic should I be using and or does anyone actually have a layout handy for a breadboard?

thanks
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby DrNomis » 06 May 2014, 00:47

jalmonsalmon wrote:I have tried making a mk1 on a breadboard, have not measured voltages or anything but so far I am getting a bad screaching mess with this circuit.
What schematic should I be using and or does anyone actually have a layout handy for a breadboard?

thanks



I think sinner posted the most accurate schematics in this thread a few pages back, start at the first page and read through all the posts in this thread since there's lots of info in them.... :thumbsup


I've noticed that the Tonebender Mk I schematic lacks one component which is commonly added to modern stompbox circuits running on a 9V battery, and that's a supply bypass capacitor, I've added a 100uF/25V supply bypass cap to my build in the hope that it'll prevent screeching and oscillation, you can try adding one to your build too, any value from say 47uF to 100uF should work fine as long as you make sure you get the cap oriented correctly..... :thumbsup
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby LucifersTrip » 06 May 2014, 12:50

DrNomis wrote:
LucifersTrip wrote:
DrNomis wrote:Q3, C=6.77V


should be ~ 8V

So apart from that voltage, everything else is okay?....... :hmmm:


Q1 has a bit different voltages from what you have, also...here's some that EW posted:

http://tinyurl.com/m2aoq95
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 06 May 2014, 19:20

:popcorn:

Watching this to see how you guys do. I may even experiment with some more transistors to see what I can get..
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby jalmonsalmon » 06 May 2014, 23:46

I got a set from small bear a few weeks back that were not working...
I measured them according to http://www.geofex.com/Article_Folders/ffselect.htm and here is what I get

2N281 Q1 63 hFE , .078 Lk
AC128 Q2 168 hFE, .776 LK
AC128 Q3 101 hFE, .235 Lk

I think I have several AC125s that are leaking in the 200's and other assorted transistors such as a OC73 that tests out to 170hFE LK 271 because that one AC128 small bear gave me is really leakey.
No time to mess with this circuit because I have a butt load of transistors I am testing and that takes forever haaha... oh temp in this room is about 76ºF - 78º F so testing transistors is always fun to do in here
I will read this thread a few more times and try out all the suggestions here to get this Mk1 working, I even breadboarded a zonk machine layout as well and it is a screeching mess too.

CHEERS!
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby DrNomis » 08 May 2014, 07:27

If any of you are having trouble with your builds making high-frequency screeching sounds while playing, here's something you can try, on the input of the circuit where the 10nF cap is put a 1M resistor in parallel with a small value cap(say anything from about 470pF to 10nF)from where the input socket connects to the 10nF input cap(after the footswitch) to circuit ground, have a look at the Tonebender Mk II circuit to see where to place the cap and resistor, I was tinkering with my build trying to stop it from screeching when I had an idea, I tried putting a cap from the input to circuit ground and found that it fixed the screeching, you may need to experiment with different cap values........ :thumbsup
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For this message the author DrNomis has received thanks:
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby G.G. » 08 May 2014, 20:48

Hi Folks,
I've built up 2 MKI's from the two-trimmer layout over at Guitar FX layouts. I biased them by ear so I don't have voltages but they both sound good to me and have a decent amount of range on the Attack. Both of my builds, however, sound like they don't quite have as much overall volume available when compared with other pedals (TS clone, for example). Is that a characteristic of this circuit or possibly something out of adjustment on my builds? The pedals both get above unity but just don't seem as loud as other dirt pedals I have. Here are a few clips of one of the builds:

https://www.youtube.com/watch?v=IDc9wR6fSi8

https://www.youtube.com/watch?v=LRocGzeUwfg

https://www.youtube.com/watch?v=VbTSKhOZRrk
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 08 May 2014, 22:15

Hey G.G.. it sounds like a decent build. Looks like you were using those Russian 'ufo' style transistors like I did? Do you not have a MM to provide voltage readings? Do you have Hfe and leakage readings also? It would be handy for anybody else that's starting this build.

In the end, I removed the trim pots on mine, replaced with stock resistors and plugged in transistors until it sounded good. I found this to work better than using the trim pots. Mine sounds similar to yours, but a tad less gated.

The low volume is a characteristic of this pedal, it has many quirks. You can counter this by decreasing the value of the final resistor in the circuit though. Experiment with some different values.

Dan
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby G.G. » 08 May 2014, 22:49

Thanks Dan! I do have a DMM but I just had a couple sets of transistors from Small Bear, rather than several to choose from. The build in the video is their "generic" set but I also did a build using their OC75 set. I didn't have both together to compare but they seemed to sound very similar. They low volume doesn't bother me personally, but a friend asked me to build one for him and since I had no experience with the MKI I thought maybe I made a mistake that was causing the low volume. I might mess around with lowering the resistor value and see how it goes. Thanks again!

sickman82 wrote:Hey G.G.. it sounds like a decent build. Looks like you were using those Russian 'ufo' style transistors like I did? Do you not have a MM to provide voltage readings? Do you have Hfe and leakage readings also? It would be handy for anybody else that's starting this build.

In the end, I removed the trim pots on mine, replaced with stock resistors and plugged in transistors until it sounded good. I found this to work better than using the trim pots. Mine sounds similar to yours, but a tad less gated.

The low volume is a characteristic of this pedal, it has many quirks. You can counter this by decreasing the value of the final resistor in the circuit though. Experiment with some different values.

Dan
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby Electric Warrior » 09 May 2014, 13:37

Did you build the one that has a 47k in parallel with the volume pot? The one without it should be loud as f**k.
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 09 May 2014, 14:06

My layout matches the D*A*M Gary Hurst schematic, as does G.G's. There is a 47k to ground after the 2m2. I reduced the 2M2 to 1M, which gave me plenty of volume.

Never seen a schematic without the 47k to be honest.
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby Electric Warrior » 09 May 2014, 14:58

Check out page four of this very thread. The schematic labled "Sola Sound" doesn't have it. I believe they just dropped that resistor at one point.
The unit that Dave traced for this schematic is missing the resistor between the Attac pot's middle log and ground as well - but that one wasn't dropped from what I've gathered so far. I believe it was an optional part.

Also note that Dave changed the resistor on Q2's base to 470k because it biased up better for him. The Sola Sound branded unit he traced had a 180k there. No big deal, though, as it's within the range of values used in vintage units. They tweaked this one a lot. I've seen units with two resistors in parallel there or with a cut out resistor that was replaced with a different value.
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 09 May 2014, 16:15

Interesting, it's been a while since I looked at those schematics. It seems that it's the 56k that was dropped and the 47k moved. I had noticed that 470k change, I had that in there for a while, but changed to 180k and for me it seemed to work better.

I also noticed a few pages back that Dave had a 3n or 4n cap to ground on the input too.. low pass filter? I don't quite get it.. too big a cap to be a noise filter surely?

I swear this pedal could take over your life if you allow it.
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby DrNomis » 09 May 2014, 18:06

sickman82 wrote:Interesting, it's been a while since I looked at those schematics. It seems that it's the 56k that was dropped and the 47k moved. I had noticed that 470k change, I had that in there for a while, but changed to 180k and for me it seemed to work better.

I also noticed a few pages back that Dave had a 3n or 4n cap to ground on the input too.. low pass filter? I don't quite get it.. too big a cap to be a noise filter surely?

I swear this pedal could take over your life if you allow it.




He probably put that 3 or 4nF cap there to tame high-frequency screeching..... :hmmm:
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 09 May 2014, 18:44

I've only just realised the glaringly obvious differences in those schematics. Oh damn it.. now I'm gonna have to build the 'Sola Sounds' version too.. :slap:
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby sickman82 » 09 May 2014, 22:04

DrNomis wrote:He probably put that 3 or 4nF cap there to tame high-frequency screeching..... :hmmm:


You're right.

I messed around with that tonight, it does indeed tame screeching. Anybody with screeching issues, try a cap from 3-10n on the input to ground.. just make sure you put it on the board as opposed to the switch, or it will have an effect on your bypassed signal too.
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby jalmonsalmon » 09 May 2014, 23:08

sickman82 wrote:
DrNomis wrote:He probably put that 3 or 4nF cap there to tame high-frequency screeching..... :hmmm:


You're right.

I messed around with that tonight, it does indeed tame screeching. Anybody with screeching issues, try a cap from 3-10n on the input to ground.. just make sure you put it on the board as opposed to the switch, or it will have an effect on your bypassed signal too.


Thats me... call me mr Screech!

I will try out a cap on the input to ground and see how that works!

Thanks
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby jalmonsalmon » 26 May 2014, 19:07

I think I have this one working now... To the Breadboard I added a 4.7n cap going from input to ground and the screech is gone.
Must sound good because I spent over an hour wailing on this thing, amazed at the sounds I was getting... I just used random transistors and it works great but I will tweak it later with other transistors and report back :applause:
Thanks for all the help and this is an awesome thread!
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Re: Sola Sound - Tone Bender Mark I (1965)

Postby jalmonsalmon » 26 May 2014, 22:59

DrNomis wrote:
sickman82 wrote:Interesting, it's been a while since I looked at those schematics. It seems that it's the 56k that was dropped and the 47k moved. I had noticed that 470k change, I had that in there for a while, but changed to 180k and for me it seemed to work better.

I also noticed a few pages back that Dave had a 3n or 4n cap to ground on the input too.. low pass filter? I don't quite get it.. too big a cap to be a noise filter surely?

I swear this pedal could take over your life if you allow it.




He probably put that 3 or 4nF cap there to tame high-frequency screeching..... :hmmm:



Question about that cap to ground on the input... how is it that it kills the screeching?
I feel kind of dumb here LOL
Would think I could just use the stock schematic without that issue, or maybe I just have crap transisters LOL
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