Small Bear Flathat Tonebender Set and Build Observations

[Big Monk]

Long time lurker but first time poster.

Recently got back into building and decided I'd finally put a Tonebender together. I opted for Steve's "Flathat" TB MKII set as the foundation.

I put the circuit on the breadboard over the past few days. I was initially planning on more of a Supa-Fuzz variant but playing through the circuit with my neck humbucker only guitar led me back toward the stock circuit. A few things I've noticed:

1.) I tried a few combos for the input cap including an Easy Face Blend control. I used 10 mf/2.2 mf, 10 mf/4.7 mf and 10 mf/0.01 mf with a 100kB pot. I was careful to hook it up correctly but it did not seem to do much. I also tried 10mf, 4.7mf, and 2.2 mf separately. 10 mf was too woofy in any combination (i.e. in conjunction with other "downstream" mods) and 2.2 mf was too icepicky/bright after playing around I settled on the stock 4.7 mf.

2.) I played around with resistor from base to ground on Q1. I swapped values when I had the other input caps in, such as 10k up through 100k with the 10 mf, etc. but settled on 100k with the switch back to 4.7 mf.

3.) I have a 250k Easy Face style Pre-gain control currently hooked between the coupling cap off of Q1 and Q2 base. I was originally planning on a fixed value in place of the Attack pot and just using the Pre-gain to control fuzz. I hooked up the Pre-gain in the beginning of the circuit as well. I placed an order through Small Bear for a 1kC pot for Attack and I think when I hook it up I'll move the Pre-gain back to the input. I'm hoping these 2 controls together will give me a good way to impact the overall texture of the fuzz tone.

4.) I played around with bypass caps on the Q3 emitter. Obviously I tried 10 mf, 4.7 mf and 2.2 mf. 10 mf is definitely out, and I currently have a 4.7 mf there, but 2.2 uf is still in the rotation.

5.) I used Steve's recommendations for collector resistors and the feedback resistor but may hook up trim pots on Q2 and Q3 to see if I can lock down a bias value that gives me the overall texture I want.

6.) I changed the resistor from output cap to power rail to 1.2k to boost the overall output.

7.) I used some silver mica caps that I had laying around from base to collector on Q2 and Q3. I believe I used 10 pf on Q2 and 220 pf on Q3. For Q3 it was a huge improvement. I really liked the brightness after going back to the stock circuit but the overall tone was a big ragged/jagged/spiky. That cap smoothed it out very nicely and reduced the overall noise in the circuit. I do think I want to experiment with a smaller value to maximize the effect. Also I'd like to try a larger value at Q2.

8.) I played with the stock 0.01 mf output cap and 0.1 mf. Along the same lines as 7.) the 0.1 smoothed thing out pretty nicely with the stock circuit. I may try a few more values lower than 0.1 mf to try and maximize the smoothing effect.

9.j I may try a cap in a parallel with the 1.2k "output" resistor.

Overall I went back to the stock circuit and am just going to try and maximize the overall brightness and smoothness with cap mods and the Pre-gain/Attack pot combo. I also ordered the parts to try and breadboard a silicon version to satisfy my curiosity but overall the "Flathat" germanium Version with minor tweaks is sounding nice.

I guess I don't really have any questions or concerns but I'd be willing to hear what you think!

[tubegeek]

I think that's a pretty informative Post #1 is what I think. Welcome.

[Big Monk]

Well I started the thread thinking I was going to have more questions! I'm an electrical engineer so troubleshooting is something I'm doing on a regular basis so when it came time to post I realize I had all my issues worked out and was just looking to document my thoughts.

[Fancy Lime]

Long time lurker but first time poster.

...

Welcome to the nuthouse!

Andy

[smallbearelec]

I am always a little concerned at first when I see a heading that starts "Small Bear Transistor Set...", because it might be a newbie who writes something like: "I built with the recommended resistor values and it doesn't work/doesn't sound right..." I'm glad to see that this poster did the right thing and put the circuit on breadboard to tweak; always my first suggestion when building any germanium design.

Merry Christmas/Happy Chanukah to all!

SD

[Big Monk]

I am always a little concerned at first when I see a heading that starts "Small Bear Transistor Set...", because it might be a newbie who writes something like: "I built with the recommended resistor values and it doesn't work/doesn't sound right..." I'm glad to see that this poster did the right thing and put the circuit on breadboard to tweak; always my first suggestion when building any germanium design.

Merry Christmas/Happy Chanukah to all!

SD

Well I appreciate the back and forth we had via email Steve. You've been a great supplier.

My biggest thing at this point is tweaking the vintage correct stock circuit to suit my style. I like the brightness and cut but I'm just looking for very nuanced tweaks to take the jaggedness/raspiness off the top. Especially since I play a neck humbucker only.

I think between the base-collector mica caps on Q2 and Q3, a 0.1 output cap, and maybe playing with the Q3 emitter bypass cap I'll have it ready for boxing up soon. Also I think the combination of 1kC Attack pot and Pre-gain pot will help to dial in the texture of the fuzz.

I've got some other builds in the works so you can expect more business coming your way.

[Big Monk]

I am always a little concerned at first when I see a heading that starts "Small Bear Transistor Set...", because it might be a newbie who writes something like: "I built with the recommended resistor values and it doesn't work/doesn't sound right..." I'm glad to see that this poster did the right thing and put the circuit on breadboard to tweak; always my first suggestion when building any germanium design.

Merry Christmas/Happy Chanukah to all!

SD

Speaking of Small Bear and Breadboards, I was able to get my thrifty/DIY idea board together today.

Definitely not as elegant as your assembled version Steve, but useful nonetheless!

[Big Monk]

So after my latest Small Bear order, I ended up with the RDV Si Bender MKII with the option of using the "hotter" (relative to the other Flathats) Flathat Q3. Everything just sounded "tighter" in this version and I can still dial in some warmth when needed.

I've got some pictures I'll post up tomorrow. I'm very proud of the wiring.

I do have a question about the attack pot: I used a reverse log 1k in conjunction with an Easy Face pre-gain at 250k. I could have sworn I was getting much better control over the Fuzz on the breadboard than with it all boxed up. Frankly, I now can't remember and I was admittedly testing at low volume so the nuance could be lost. Also, I'm now thinking that due to the noise levels on the breadboard, I may have been perceiving tonal changes from noise/hiss changes.

Any thoughts?

In my research it seems the Q1 base resistor value can effect the sweep on the attack pot?

[Big Monk]

Pictures as promised:









I'm satisfied with the overall circuit but I'd like to investigate a better, more usable range on the Attack pot. The reverse log pot alone didn't give me what I wanted. I'm going to investigate the base to ground resistor on Q1. I currently have a 100k in there.

[Big Monk]

I know from the other forums I participate in (homebrewing forums in particular) that no responses does not necessarily mean people arent tuning in so I have a quick update:

1.) I was having issues with the Attack pot which seem very common. I was aware that the Attack range was nothing mind blowing but also expected something more akin to a "texture" control which I was not getting. The 1kC pot did not seem to do anything for me. In the end I swapped out the 100k to ground on the Q1 based for a full size 100kB pot. I mounted that on the inside of the enclosure with a dab of hot glue so I can adjust and find the fixed value I want in tandem with the bias changes I need. I had read that lowering this resistor could give me a more usable range on the Attack pot. The lowest value I could use while still getting signal through the Q1 stage was ~27k. The Attack pot functioned as a "texture" control at that point as expected but bias was thrown off a little.

2.) I am in the process of laying out a new PCB with some tweaks and improvements on the GGG board. More akin to the Aion board but with a few tweaks I want. I don't like only adjusting bias with a Q3 trimpot so in the same style as the 100k Q1 base resistor, I attached a full size pot inside the case. I am going to tweak all three pots tonight by ear to dial it in and then replace the 2 full size pots and Q3 trim pot with fixed resistors.

3.) I am leaning toward the Q3 Flathat Ge that came with my Small Bear set over the 2N5088 in the Q3 slot. With the revised circuit, the Flathat performs better and has less high end fizz. In my revised PCB layout, I plan on having slots for Base to Collector mica caps like in the Aion board. I technically could have installed one on the GGG board but space was tight and it would have had to go underneath and I believe the cap would have interfered with the PCB standoffs.

[mth5044]

I got to ask... guitar with neck only pickup???

[Big Monk]

I got to ask... guitar with neck only pickup???

I play mostly with the neck pickup anyway. My bridge pickup quit a while back and I was never very fond of it. I'm looking for a suitable replacement. Bridge humbuckers are always pretty wimpy IME on a trem equipped guitar. I use all 5 springs and modified the bridge with 4 screws in addition to the 2 point studs.

For the time being I really like this guitar (an older Squier Standard Strat) and I am auditioning bridge pickup replacements. I'm historically a Les Paul guy but can't seem to bond with anything in my price range. The Squier has a good snappy attack because of the longer scale and plays pretty well. I just recently got back into playing and I scored it cheap used at GC.