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Author Topic: Just built a Tone Bender Mk.I . Need advice.  (Read 8202 times)

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #15 on: January 10, 2016, 07:01:29 AM »
Thank you for your replies Phil and Juan. I have it working much better now. It turns out I had accidentally placed the electrolytic cap backwards in the circuit and that was driving me crazy. I didn't notice until I had swapped every resistor (except the 2k2). It's now getting close to that Yardbirds sound, but it could do with some higher gain transistors.  I want it to be more buzzy sounding. I'm. Pretty sure that Mr.Page used a professional Mk. II bender. I'm also working on one of those and it's giving me more problems than this Mk.I, if you can believe that. As usual, the amp I'm using is my early 70s Kasino. Thanks to Juan's suggestions,  among others, It's still working. These tone benders are certainly teaching me a lot about germanium fuzz. Thanks again.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #16 on: January 10, 2016, 07:05:36 AM »
Oh, and I was blaming those poor AC128s for the muddy sound. After fixing the cap problem, it's now very bright sounding.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

phatt

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #17 on: January 10, 2016, 07:39:01 AM »
Cool :tu:
Regards  posting pictures I have been using this;
http://postimage.org/

Specifically aimed at forums,, Heck if I can work it out it must be close to dumb proof  :lmao:
had no major issues so far. :tu:
Phil.

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #18 on: January 10, 2016, 07:04:56 PM »
Thanks. I'll give that a try. Don't know if it'll work with my phone. I took a look and it seems a but confusing to me.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #19 on: January 10, 2016, 08:50:21 PM »
I can't figure that pos image thing out. It says something about copying the text. I guess I'll just stick to what little bit I can actually do on here. Thanks anyway.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

J M Fahey

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #20 on: January 11, 2016, 12:33:22 AM »
Just thinking aloud: can't you leave the phone aside for a while and grab/beg/rent/steal  ;) a PC/notebook/netbook/tablet for a few minutes?

Phones are cool and available anywhere but sometimes not enough for some tasks.

And not sure how well you can see schematics on the tiny screens anyway.

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #21 on: January 11, 2016, 05:41:56 AM »
I can see schematics just fine on it. I just can't get it to post an image. In answer to your question,  no. No one near me has a computer that I know of and I don't know many of the people who live near me. Thephone may not be the best thing to use, but it's all I have. I believe I got a batch of very leaky AC128 transistors because I just built a Maestro FZ-1 circuit and it works. Not as buzzy as I'd hoped, but these have pretty low gain. Does this mean they're too leaky for my Tone Benders?
« Last Edit: January 11, 2016, 05:44:48 AM by LJN »
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

J M Fahey

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #22 on: January 11, 2016, 07:56:57 AM »
Only testing will do.

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #23 on: January 11, 2016, 09:41:10 AM »
Very true, Juan. I need to get a good transistor tester. All I have is a cheap multi meter and it seems to combine gain and leakage, showing a very high hfe on the display.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

J M Fahey

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #24 on: January 11, 2016, 06:34:25 PM »
Well, go the Argentine Way [tm]  and kludge one ;)

Whenever I have to test or measure something I just build the very basic textbook example , so just a plain multimeter is enough.

In this case, you need a 9V battery (or equivalent supply) , a multimeter, some kind of socket (a protoboard will do) or 3 crocodile clips, and a couple pots: 500k Log might be useful or , say, 500k and 100k linear.

1)  you connect emitter to ground, base to ground, and collector to -9V through the multimeter, suggest the 20mA scale.

Whatever you measure is leak current .
You might make a second reading by grounding base through , say, a 10k resistor to simulate the presence of a biasing network OR plain test with the values suggested in the schematic .
This will give you near actual circuit conditions.

Say you get 0.1 mA leak current. Write it down, somehow label all transistors because there will be quite a spread.

As an experiment, you might touch one case with your finger and watch leak rise with temperature ... or not.

2) now connect the pot in series, set to max value, from base to -9V .

Set it to whatever's necessary to get 1mA+leak current on the meter , in the example 1.1 mA (so you know that 1 mA is due to base biasing and not leak).
Measure pot resistance, calculate base current, divide 1mA by that and you have real Hfe, without leak contribution, how's that?  8)

Yes, it takes a little longer than reading a dedicated LCD screen ...... wait!!!! ..... WHAT LCD screen  :lmao:

The dedicated meter (PEAK?) does the same, just an embedded processor and software does the Math for you.

EDIT: FWIW I'm testing a typical "Twin Reverb speaker" , in this case a Rola pulled from a Silverface '78 one, comparing it to my own version of a classic Jensen C12N .

Among other parameters, it's very important for me to measure the magnetic energy in the voice coil gap, and to check whether my physical measurements precision (no Jensen/Rola blueprints available anywhere) , magnetic steel choice , magnet quality and magnetizer power are all as nbeeded or better.

So I'd need to fire up my Magnetometer .... problem is I have none at home, the only one I know and have access to is in a suburb at the other end of the city (think driving from San Diego to Malibu) plus lately I'm not on speaking terms with my ex business partner so ..... I had to kludge one  :duh

As simple as can be, it's not calibrated in Maxwells because the reference magnet is in the hands of my ex partner  :grr  but I can make very accurate *relative/comparison*  measurements which at the moment is all I need.

I calibrated it so the Twin speaker shows 1.000V on the Multimeter display, I woud have been happy with any measurement (on mine)  above 0.950 V (meaning 95% of the power of an American made Fender speaker), was happily surprised when mine showed 1.150V meaning 15% higher flux so expected 33% higher efficiency, all else being equal of course (efficiency is proportional to the square of magnetic strength) .

So in a nutshell homemade simple instrumentation can be very useful, specially when circumsatances don't justify getting one for a single or very limited use.

Oh, what is the magnetometer schematic?
Just a single Op Amp, an integrating capacitor (100uF) , a couple resistors, and since it drifts (the 100uF is ... ugh ... an electrolytic),  plus the Op Amp even if being a TL072 does have some drift/offset , I had to add a 100k nulling pot and a 1M resistor.

Total cost less than $5  .
« Last Edit: January 11, 2016, 06:58:39 PM by J M Fahey »

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #25 on: January 11, 2016, 07:35:00 PM »
Wow, Man! Interesting stuff! I actually have a schematic for a simple hfe and leakage test circuit in one of my notebooks. Never really thought I'd actually need it, as I couldn't locate any germanium transistors at the time. Glad to hear your speaker's working. I have an old C12N in my cabinet. Those are really good speakers. I believe it dates to 1961. I really appreciate your suggestions on the leakage test, but I'm terrible with math. I guess I could use a calculator,  though. I've noticed that all of my fuzz circuits tend to sound smoother through my Kasino amp. I've tried a few of them through other amps and they sounded completely different. Maybe this just isn't a fuzz-friendly amplifier? In any case, it seems if I record any of my fuzzes on tape, the result is a slightly more raspy sound, even with that particular amplifier. I'm using a 2x12 cab with the aforementioned Jensen speaker, which is paired with a Rola- Celestion G12-30. The microphone is kept near the Rola speaker because it's in the top of the cab. Thanks again, Juan.
« Last Edit: January 11, 2016, 07:36:59 PM by LJN »
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #26 on: January 11, 2016, 08:31:57 PM »
I tried this one with my little Tele-Star amp and there wasn't much difference. With that amp, there's a slight squealing noise in the decay. I did notice that it had a little more sustain than it had when plugged into my kasino amp, though.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #27 on: January 22, 2016, 12:08:28 AM »
I built the R.G Greene transistor test circuit and after testing several of my transistors,  I have found what I believe is the best possible combination from my current inventory. For Q1,  I have hfe 64 with about 153 uA leakage, Q2 the 78 with about 220 uA leakage. I didn't bother to check Q3, but it's labeled as hfe 59 and leakage at 0.08 mA. I imagine it would read differently on my home made tester, but I think I'll just leave it alone. The effect is now more aggressive sounding and has decent sustain. It doesn't seem to be too noisy. Turning down the guitar volume makes it gate, but also adds more treble. It's surprisingly articulate, but still could probably benefit from some higher gain transistors just to get a bit more of that "buzz" out. I'm getting pretty close now, anyway. It'll suffice until I can get a good matched set of transistors for it.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #28 on: February 03, 2016, 04:58:24 PM »
I finally boxed this circuit up in a vintage style enclosure that I built last night. Putting it in a case actually seems to have solved some of the problems it was having. For some reason, it sounds a bit brighter than before and I can now turn the attack control to full, but only with the bridge pickup. Using the neck pickup with the Tone on zero and the attack on full produces a weird chirping sound as the notes decay. I'm still planning to order a matched set of transistors for it. I think there's still room for improvement here.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

LJN

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Re: Just built a Tone Bender Mk.I . Need advice.
« Reply #29 on: February 03, 2016, 05:11:38 PM »
I forgot to mention that I completely rebuilt the circuit and it's now I red point to point just like the original. Also, the guitar I'm using is a Epiphone Les Paul standard with hamburgers. I think the Berridge pickup is around 8k and the neck pickup is around 7.5k. I thought this may have some relevance.
If it sounds good, USE IT!

 Epiphone Les Paul, Kasino U100- P, Sears 125-XL

 

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