Sola Sound - Tonebender Mark II Professional  [schematic]

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

Re: Sola Sound - Tonebender Mark II Professional

Postby Scruffie » 29 May 2013, 15:14

DrNomis wrote:
Scruffie wrote:The red dot has always been the collector on any germanium i've ever used... that's what it's for as far as I know.

Well the DMM readings are higher because of the leakage aren't they.

AC127s? They're NPN aren't they? Germanium NPN seems to commonly be of worse quality (except for some of the russian stuff and wherever Smallbear Steve is getting his NOS parts) they were probably just hugely leaky and shot.



Yep, that's true, Germanium transistors do generally exhibit alot more leakage (microamps) than Silicon ones do (nanoamps), and yes AC127 transistors are NPNs, they're basically the complements of AC128s which are PNPs, in the early days of transistorised radios an AC127 and an AC128 were used as power output transistors in what's called a complementary Push-Pull configuration, sometimes either two AC128s or AC127s were used together with a small audio output transformer, I used to have a couple of OC140 NPN transistors and they had very low leakage currents, worked great in a Fuzz Face circuit, unfortunately one of the leads broke off one of the OC140s right where it goes into the encapsulation so I couldn't use it anymore, when you buy Germanium transistors on eBay it's a case of pot-luck whether you get good ones or not, and I tend to have a philosophical attitude about that and accept that I'll ocasionally get duds, sometimes you do end up scoring a few gems though.

The reason why Germaniums leak more than Silicons has alot to do with the atomic structure of the Germanium semiconductor material, the electrons in the outermost shell (the Valence Shell) aren't held as tightly in their orbits around the nucleus as they are in the Valence shell of a Silicon atom, therefore they are easily knocked out to the shell by an electric current, sorry about the technical terms there.... :thumbsup

I wonder what criteria Smallbear Steve uses for determining which Ge transistors are good or not?.... :hmmm:

I also wonder what criteria Analog Man use in his selection process too?.... :hmmm:


:lol: I'm well aware of the difference between Silicon & Germanium and the issues of leakage and purchasing them Simon :thumbsup

What I was saying was that over PNP germanium, i've seen a lot more reports of NPN Germanium leaking more or having low hFe, well in the past, it seems people have started digging up decent ones especially from Russia & U.S. factories now-a-days. I recall the AC127 in particular being used because everyone figured 'AC128 for the PNP Fuzz Face, I should use the NPN Counterpart' and then being disappointed with the quantity of bad ones on the market.

I've only ever played with a handful of NPN Germanium though, tend to use PNP with charge pumps as I have (or had until I sold off most of them) a decent quantity of good quality original Mullard transistors in all the favourite 44/71/75 & 81D flavours. Saying that when using 81Ds in my MkII while they sounded nicest in either the 1st or 3rd positions (can't recall which without going and looking) I preferred 81s (not the Driver suffix) in the other positions, even accounting for leakage and gains... but that's a different story altogether.

Ha, I had worse than that, I had a Mullard metal can OC81D actually shatter internally when trying to use it, can't remember how I actually managed to do that but the transistor was a write off... thankfully I think it wasn't a very good one anyway.

Yeah i'm pretty sure Steve mentions he uses the R.G Keen method, it's reliable enough and as I think the Sun Face from AnalogMan has been around I think longer than those Peak meters have been around, i'm guessing much the same, especially as he was once a regular of DIYStompboxes so would undoubtedly have read Geofex.
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Re: Sola Sound - Tonebender Mark II Professional

Postby DrNomis » 29 May 2013, 15:34

Scruffie wrote:
DrNomis wrote:
Scruffie wrote:The red dot has always been the collector on any germanium i've ever used... that's what it's for as far as I know.

Well the DMM readings are higher because of the leakage aren't they.

AC127s? They're NPN aren't they? Germanium NPN seems to commonly be of worse quality (except for some of the russian stuff and wherever Smallbear Steve is getting his NOS parts) they were probably just hugely leaky and shot.



Yep, that's true, Germanium transistors do generally exhibit alot more leakage (microamps) than Silicon ones do (nanoamps), and yes AC127 transistors are NPNs, they're basically the complements of AC128s which are PNPs, in the early days of transistorised radios an AC127 and an AC128 were used as power output transistors in what's called a complementary Push-Pull configuration, sometimes either two AC128s or AC127s were used together with a small audio output transformer, I used to have a couple of OC140 NPN transistors and they had very low leakage currents, worked great in a Fuzz Face circuit, unfortunately one of the leads broke off one of the OC140s right where it goes into the encapsulation so I couldn't use it anymore, when you buy Germanium transistors on eBay it's a case of pot-luck whether you get good ones or not, and I tend to have a philosophical attitude about that and accept that I'll ocasionally get duds, sometimes you do end up scoring a few gems though.

The reason why Germaniums leak more than Silicons has alot to do with the atomic structure of the Germanium semiconductor material, the electrons in the outermost shell (the Valence Shell) aren't held as tightly in their orbits around the nucleus as they are in the Valence shell of a Silicon atom, therefore they are easily knocked out to the shell by an electric current, sorry about the technical terms there.... :thumbsup

I wonder what criteria Smallbear Steve uses for determining which Ge transistors are good or not?.... :hmmm:

I also wonder what criteria Analog Man use in his selection process too?.... :hmmm:


:lol: I'm well aware of the difference between Silicon & Germanium and the issues of leakage and purchasing them Simon :thumbsup

What I was saying was that over PNP germanium, i've seen a lot more reports of NPN Germanium leaking more or having low hFe, well in the past, it seems people have started digging up decent ones especially from Russia & U.S. factories now-a-days. I recall the AC127 in particular being used because everyone figured 'AC128 for the PNP Fuzz Face, I should use the NPN Counterpart' and then being disappointed with the quantity of bad ones on the market.

I've only ever played with a handful of NPN Germanium though, tend to use PNP with charge pumps as I have (or had until I sold off most of them) a decent quantity of good quality original Mullard transistors in all the favourite 44/71/75 & 81D flavours. Saying that when using 81Ds in my MkII while they sounded nicest in either the 1st or 3rd positions (can't recall which without going and looking) I preferred 81s (not the Driver suffix) in the other positions, even accounting for leakage and gains... but that's a different story altogether.

Ha, I had worse than that, I had a Mullard metal can OC81D actually shatter internally when trying to use it, can't remember how I actually managed to do that but the transistor was a write off... thankfully I think it wasn't a very good one anyway.

Yeah i'm pretty sure Steve mentions he uses the R.G Keen method, it's reliable enough and as I think the Sun Face from AnalogMan has been around I think longer than those Peak meters have been around, i'm guessing much the same, especially as he was once a regular of DIYStompboxes so would undoubtedly have read Geofex.



No worries at all Scruffie, amongst my set of AC127 transistors, the majority of them definitely were very low gain, Hfes around 7 to 8 , there was one that had a leakage of about 1.4mA.... :shock: ...., I compared them to some OC44 transistors I had (PNPs) which were more consistant, so I would have to agree with you on that, the PNP Germaniums avalible do seem to be a bit more consistant.... :thumbsup
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Re: Sola Sound - Tonebender Mark II Professional

Postby jrod » 29 May 2013, 16:42

DrNomis wrote:I wonder what criteria Smallbear Steve uses for determining which Ge transistors are good or not?.... :hmmm:


Scroll to the bottom of this article and he explains his method.
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Re: Sola Sound - Tonebender Mark II Professional

Postby jalmonsalmon » 30 May 2013, 01:23

bajaman wrote:Of all the tonebenders, I really do like the MkII version - It nails the Hendrix Voodoo Child sound when you put a well tuned wah pedal in front of it too.
I don't think Hendrix ever used a Fuzz Face - If he did, I don't think he liked it from what I have heard from folks supposedly in the know - forget the other benders - build a MkII - you won't be sorry you did.
bajaman



Hehee... I some of the tonebender type of tones Hendrix got could have been from running 2 fuzz faces together at the same time... If he did in fact use a tone bender... way cool! :hmmm:
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Re: Sola Sound - Tonebender Mark II Professional

Postby phibes » 30 May 2013, 05:35

Those are DSI 81'd's. NPN shouldn't leak any worse than PNP. I've never seen one leaking more, just depends on how cherry pick the batch is that you choose from.

You might be able to pull it off Simon, those gains are low but it's worth a shot. Try subbing the resistor on Q2's collector for a 100K trimmer. Tone Benders aren't meant to sound perfect. You don't need to use the RG Keen method for measuring germs, the peak atlas does just fine. Analogman has super secret special gnomes measure his germs.
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Re: Sola Sound - Tonebender Mark II Professional

Postby DrNomis » 30 May 2013, 09:40

Cheers phibes, I'll try that 100k trimpot suggestion of yours, should make it easy to set the Q3 biasing point, I found that with a transistor with 100Hfe for Q3 I needed a 20k trimpot to get the biasing right, will let you guys know how it goes, might see if I can post a soundclip too..... :thumbsup
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Re: Sola Sound - Tonebender Mark II Professional

Postby bato001 » 30 May 2013, 14:41

DrNomis wrote:Cheers phibes, I'll try that 100k trimpot suggestion of yours, should make it easy to set the Q3 biasing point, I found that with a transistor with 100Hfe for Q3 I needed a 20k trimpot to get the biasing right, will let you guys know how it goes, might see if I can post a soundclip too..... :thumbsup


DrNomis, I use trimpots on Q2 and Q3 (10k if I remember correctly-there are schematics in this thread a few pages back) to tailor the sound even further. I don't see any reason why you cannot get a decent sounding MKII with those HFE's. I never measure leakage, just HFE. I put the lowest HFE trannie in Q1, highest in Q2 and middle in Q3. I found the best sounding Bender came from a HFE of around 70 in Q1, 120+Q2 and 100+ Q3, but that is my personal taste. I have made MKII's with transistors all below 100 HFE and they sounded good.
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Re: Sola Sound - Tonebender Mark II Professional

Postby phibes » 30 May 2013, 15:40

You shouldn't need a trimmer on Q3 if you got one on Q2. The trimmer on Q2 sets the point for Q3 so they interact correctly. I agree on gains though. I rarely use any germs over 80.
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Re: Sola Sound - Tonebender Mark II Professional

Postby bato001 » 30 May 2013, 16:57

phibes wrote:You shouldn't need a trimmer on Q3 if you got one on Q2. The trimmer on Q2 sets the point for Q3 so they interact correctly. I agree on gains though. I rarely use any germs over 80.

I will try eliminating the trim on Q3 on my next build then. Saves me money lol.
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Re: Sola Sound - Tonebender Mark II Professional

Postby DrNomis » 30 May 2013, 17:45

If anything, it's going to be an interesting little excercise, thanks for your inputs phibes and Bato001..... :thumbsup
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Re: Sola Sound - Tonebender Mark II Professional

Postby Fred_Garvin » 18 Jun 2013, 02:49

Here's my version of the Tonebender MK II

I used the biggest goofiest case I could find on Ebay. There's no mojo parts, even the transistors are average pnp germanium.
Transistors used are TUNGSRAM ac128 (66hfe, leak: .160mA) Q1, Russian 1t308B (79hfe , leak: .000mA) Q2, and lastly a NTE158 (120hfe, leak: .230mA) Q3. All measurements done by the Peak atlas DCA55.
No pots on Q2 or Q3, I just used my ears to select the best candidates.

I used the vero board layout found at Guitar Fx Layouts for this build, and it uses the ICL7660S to invert the voltage back to standard negative ground.

Why the big box? It was needed to contain all that tone. Yes, it does sound that huge. Sound clips to follow, soon.
But, it's silver? The Silver Dragon doesn't sound as cool as the Black Dragon, really, now does it?

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Re: Sola Sound - Tonebender Mark II Professional

Postby phibes » 18 Jun 2013, 04:53

Good job! The dragon would make a nice tramp stamp :wink:
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Re: Sola Sound - Tonebender Mark II Professional

Postby drewl » 24 Jun 2013, 15:22

I found some really nice sounding NPN and PNP germaniums in some old equipment from the 60's.
Before that, I ordered a set from Small Bear for a MKII build and they sound really good, lucked out I guess.
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Re: Sola Sound - Tonebender Mark II Professional

Postby andregarcia57 » 24 Jun 2013, 22:25

I bought this kit on ebay

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemVersion&item=321122102165&view=all&tid=1101424003011

according to the seller transisotres have HFE:
Q1 = 78
Q2 = 112
Q3 = 126

I have not changed anything on resistors and did not sound good.

then put trimmer in Q2 and Q3, made ​​some adjustments and improved sound.

Q2 was more resistor with 19k, it remains correct?
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Re: Sola Sound - Tonebender Mark II Professional

Postby phibes » 25 Jun 2013, 05:19

The trimmer on Q2 as at 19K? You shouldn't have to go that low. What's the trimmer on Q3 at? Those gains are high.
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Re: Sola Sound - Tonebender Mark II Professional

Postby jalmonsalmon » 29 Jun 2013, 05:40

I have a tonebender Pro MK II I made and have not really messed with the resistor on Q2 but plan on putting a trimmer on it ASAP...
Using red dot OC84s and as is, the pedal sounds fantastic, I have a 10k pot for the 8.2 resistor and that just does some cool weirdness to the effect so I am really interested in hearing what a trimmer on Q2 does :mrgreen:
This pedal sustains for days (you can go and have a bite and still be hearing that one) 8)
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Re: Sola Sound - Tonebender Mark II Professional

Postby Fred_Garvin » 10 Jul 2013, 23:49

I went back to auditioning my build and found it was nowhere near to the sounds I was hearing from the clips on Youtube.

So, I went back to the beginning of this post and read through it, and I found that Q3 wasn't properly biased. I decided to take the advice of an earlier post and installed a biasing pot for Q3. I biased it according to the following link.

http://stompboxes.co.uk/forum/viewtopic ... e&start=10

Dialing in -4.5v is totally wrong, I measured my collector voltage at Q3 and it came in at -5.04v, and it sounded squishy, farty and compressed. After I installed a 10k pot, I dialed it in by ear and it no longer sounds the same, but, aggressive, more bottom end, richer. I uninstalled the pot to measure it, and it measured at 1.088k. Wow, the measured voltage installed on the collector of Q3 was 8.77v. Now I was in the ballpark. I decided to install a 2k pot permanently instead, I didn't want all that play in the bias knob, I didn't care for that farty squishy sound. It now has the qualities of the tonebender sound that I was chasing after.

I posted a sound clip for sonic approval (enjoy my mediocre playing skills, put earmuffs on your cat or dog.) .

The clip was recorded with a Classic Series '72 Telecaster Custom, into the pedal, into a THD tube amp, plus a touch of reverb.

http://users.eastlink.ca/~aszwec/pics/huh.mp3 (19M)

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Re: Sola Sound - Tonebender Mark II Professional

Postby DrNomis » 27 Jul 2013, 07:58

Fred_Garvin wrote:I went back to auditioning my build and found it was nowhere near to the sounds I was hearing from the clips on Youtube.

So, I went back to the beginning of this post and read through it, and I found that Q3 wasn't properly biased. I decided to take the advice of an earlier post and installed a biasing pot for Q3. I biased it according to the following link.

http://stompboxes.co.uk/forum/viewtopic ... e&start=10

Dialing in -4.5v is totally wrong, I measured my collector voltage at Q3 and it came in at -5.04v, and it sounded squishy, farty and compressed. After I installed a 10k pot, I dialed it in by ear and it no longer sounds the same, but, aggressive, more bottom end, richer. I uninstalled the pot to measure it, and it measured at 1.088k. Wow, the measured voltage installed on the collector of Q3 was 8.77v. Now I was in the ballpark. I decided to install a 2k pot permanently instead, I didn't want all that play in the bias knob, I didn't care for that farty squishy sound. It now has the qualities of the tonebender sound that I was chasing after.

I posted a sound clip for sonic approval (enjoy my mediocre playing skills, put earmuffs on your cat or dog.) .

The clip was recorded with a Classic Series '72 Telecaster Custom, into the pedal, into a THD tube amp, plus a touch of reverb.

http://users.eastlink.ca/~aszwec/pics/huh.mp3 (19M)

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[ Image ]




Looks cool and sounds cool..... :thumbsup
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Re: Sola Sound - Tonebender Mark II Professional

Postby Fred_Garvin » 27 Jul 2013, 18:45

Thanks DrNomis! I appreciate the feedback. It's nice to hear it.

Another thing I think would change the biasing of Q3 is the leakage of Q2, the use of a russian transistor with no leakage has changed the resistance substancially on the collector of Q3. The resistance went down to bias properly. I bet if I changed Q2 with a leaky AC128, the resistance on the collector of Q3 would have to go in the opposite direction, up. Anyway, leakage and hfe have a great deal of impact on how the circuit functions and sounds.

Just my two cents.
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Re: Sola Sound - Tonebender Mark II Professional

Postby phibes » 27 Jul 2013, 21:18

Fred_Garvin wrote:I went back to auditioning my build and found it was nowhere near to the sounds I was hearing from the clips on Youtube.

So, I went back to the beginning of this post and read through it, and I found that Q3 wasn't properly biased. I decided to take the advice of an earlier post and installed a biasing pot for Q3. I biased it according to the following link.

http://stompboxes.co.uk/forum/viewtopic ... e&start=10

Dialing in -4.5v is totally wrong, I measured my collector voltage at Q3 and it came in at -5.04v, and it sounded squishy, farty and compressed. After I installed a 10k pot, I dialed it in by ear and it no longer sounds the same, but, aggressive, more bottom end, richer. I uninstalled the pot to measure it, and it measured at 1.088k. Wow, the measured voltage installed on the collector of Q3 was 8.77v. Now I was in the ballpark. I decided to install a 2k pot permanently instead, I didn't want all that play in the bias knob, I didn't care for that farty squishy sound. It now has the qualities of the tonebender sound that I was chasing after.

I posted a sound clip for sonic approval (enjoy my mediocre playing skills, put earmuffs on your cat or dog.) .

The clip was recorded with a Classic Series '72 Telecaster Custom, into the pedal, into a THD tube amp, plus a touch of reverb.

http://users.eastlink.ca/~aszwec/pics/huh.mp3 (19M)

[ Image ]

[ Image ]


Did you put the bias pot on Q2 or Q3? Those old DAM MKII's, like the one in that thread used the bias pot on Q2. Q3 will bias itself along with Q2.
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