Last Breadboard of 2022: The Timbre Man

[Chuck D. Bones]

You have the pots wired correctly.
I have an updated design that moves the VOLUME pot between U1.1 and the TREBLE pot. This has two advantages:
1. It improves the headroom. At high DRIVE and MID settings, U1.2 could saturate. With the VOLUME control ahead of U1.2, we can back off on the VOLUME as req'd to avoid saturation.
2. It reduces the output impedance.

Note the various component value changes.

 

[Fingolfen]

Thanks! I'll adjust...

Glad I checked before I started trying to lay this thing out...

 

[Chuck D. Bones]

Keep the traces going to U1-6 (on my schematic) very short.

 

[Fingolfen]

Updated... now to get the beast laid out... keeping those Op Amp traces short is going to be the challenge...

 

[Fingolfen]

I need to stare at it a little more and decide whether or not I'm happy with it... but it's getting there...



Edit: Now revised with top and bottom ground planes - and some traces fixed up a bit...

 

[Fingolfen]

So... got my first prototype together today...

Wow... I really like it!!!

Compared to my Tone Geek TSV808 - I really like the 3-way tone control, that gives you a lot of ability to shape the tone.

The background noise with my very hot Seymour Duncan single coils is less on this design as compared to the TSV808, but the volume headroom is also less.

The distortion / dirt comes on pretty much the same way as the asymmetric clipping modes on the Tone Geek TSV

Definitely a lot of shared DNA, but it's also it's own thing...

Full build report coming as soon as I can get some enclosures ordered...

THANK YOU Chuck for sharing this one!

 

[HamishR]

I wonder if changing D5 to a 1N4148 might slightly increase the headroom?

I do like the midrange pot but my version doesn't have it and to be honest I don't really miss it. It's easily my favourite pedal for my Gretsches.

 

[Chuck D. Bones]

I wonder if changing D5 to a 1N4148 might slightly increase the headroom?

Depends on what you mean by "headroom." What I mean is how high can you set DRIVE and how hard can you drive this pedal with hot pickups or a booster without saturating the 2nd stage.

I do like the midrange pot but my version doesn't have it and to be honest I don't really miss it.

I found that the midrange suffered too much when TREBLE was turned down low. Where do you usually set TREBLE?

Another thought is that by making R5 larger (I used 1K on mine), you are de-emphasing the bass which by contrast, can emphasize the mids.

In any case, it's essentially a Timmy with the tone-shaping retuned a bit. And we all know how good a Timmy can sound.

 

[HamishR]

Well that makes sense. I normally run Treble at around noon or slightly higher. I tried the 1K at R5 but just liked the sound better with it at 4K7. I guess it was the emphasis on the mids which I liked.

It's weird - once I find the spot where I like the mids I rarely change it, regardless of which guitar I'm using. But I'm always tweaking bass and treble for different guitars. I hadn't thought of that before. I usually find I need a bass control but a mids control is unnecessary if the circuit is tuned right.

I have been wondering about making an overdrive with a switchable midrange boost, kinda like a treble boost. But then I figured I don't really need it because I can just use a treble booster. I guess what I'd really like is a Red Rooster which is quieter, had adjustable dirt levels so it could go from clean to slightly dirty and a slightly more extreme 800-1000Hz peakiness. Something to get those She Said She Said tones. I have got pretty close with my Red Rooster/Java Boost circuit with higher hfe silicon transistors. Still quite noisy though.

But this is going off topic - sorry!

 

[Chuck D. Bones]

Well maybe we start a new thread! I was wondering if the FET-Ge Boost could be retuned to be more of a treble booster.

 

[MattG]

I was doing a bit of comparison between the Timbre Man and Tommy III schematics.

One thing I noticed: like so many pedals, both the Timbre Man and Timmy use a voltage divider to create a VREF that is half of input voltage (actually, the Timmy/Tommy's VREF isn't exactly half, due to using different value resistors for the divider, 10k and 8k2).

How this VREF is utilized is a little different between the two pedals though: if I'm using the right terminology, the Timmy uses VREF as a "ground" of sorts, keeping the signal centered at 0v. Whereas the Timbre Man essentially centers the signal at VREF, and uses the real 0v reference for ground. (Apologies if I'm butchering the terminology!)

I was just wondering: what are the right technical terms for each approach; and, are there pros/cons to either approach, considerations for using one approach or the other?

 

[Chuck D. Bones]

Referring the schematic in post #47, above...
Vref is a "virtual ground" because from an AC point of view, Vref and GND are (more or less) the same because Vref is bypassed to ground by a large capacitor (C102). R3 must connect to Vref because we need 4.5VDC to bias the opamps into the center of their operating range. R11 can either connect to Vref, or we can add a series capacitor and return it to GND. C3 and the BASS pot can connect to Vref or GND, it makes no difference as long as C102 is large enough to absorb the AC currents that flow from C3 and the BASS pot. Personally, I do not like connecting C3 and the BASS pot to Vref because nothing good comes from injecting disturbances into Vref. I don't know why some pedal builders do this.*

We can skew Vref above or below 1/2 Vcc by making R101 & R102 different. Most opamp outputs do not saturate symmetrically. In many cases the output can swing closer to GND than it can to Vcc. If we're trying to squeeze out the last few hundred mV of headroom, then setting Vref to slightly less than 1/2 Vcc will help. Whether it's necessary is open to debate.

* I don't know why some pedal builders do a lotta the stuff they do. They'd be hard-pressed to explain it themselves.

 

[MattG]

If the opamp were powered with a bipolar supply, would that remove the need for VREF?

We can skew Vref above or below 1/2 Vcc by making R101 & R102 different. Most opamp outputs do not saturate symmetrically. In many cases the output can swing closer to GND than it can to Vcc. If we're trying to squeeze out the last few hundred mV of headroom, then setting Vref to slightly less than 1/2 Vcc will help. Whether it's necessary is open to debate.

I didn't save the link, but I recently read a post on another forum from PaulC saying that's exactly why he made the VREF voltage divider resistors different, to squeeze out a bit more headroom.

A separate question: would your Timbre Man circuit (referencing schematic in post #41 above) accommodate grafting in the gain toggle that the Tommy III/Timmy v3 has? (And which I'm guessing is used as the basis for the "boost" in the Tim v3.)

 

[Chuck D. Bones]

A separate question: would your Timbre Man circuit (referencing schematic in post #41 above) accommodate grafting in the gain toggle that the Tommy III/Timmy v3 has? (And which I'm guessing is used as the basis for the "boost" in the Tim v3.)

It would work. I take it you're aware that the GAIN toggle affects the response of the BASS control.

OK, so there's one reason to return C9 (Tommy III) to Vref instead of GND. It prevents the toggle switch from popping because the DC voltage on both sides of C9 is equal. Or C9 could be grounded and an anti-pop resistor installed across SW2.2. I don't suppose Mr. Cochrane explained why he connects C3, C4 & C9 to Vref, did he?

 

[MattG]

It would work. I take it you're aware that the GAIN toggle affects the response of the BASS control.

Yup. I want to breadboard this. Not only to play with a boost/gain toggle, but to see if I can steer the overall circuit a bit towards the voice of the Tellurian, which is clearly a tweaked Timmy. (And I still want to breadboard your Yankee ScrewDriver Deluxe Turbo. So many projects, so little time!)

I don't suppose Mr. Cochrane explained why he connects C3, C4 & C9 to Vref, did he?

I don't think so (dang I wish I'd save the link). I don't even remember what I was searching for, I just happened to stumble on PaulC's comment, found it interesting, so it stuck.

Anyway - is it possible to eliminate VREF entirely if using a bipolar supply for the opamp (e.g. +9v/-9v)?

 

[Chuck D. Bones]

Anyway - is it possible to eliminate VREF entirely if using a bipolar supply for the opamp (e.g. +9v/-9v)?

Yes. See the Frost Drive schematic for an example. There's no free lunch: we have to deal with the switching noise from the charge pump.

 

[cooder]

Finally got mine boxed up, this is still after the earlier schematic with volume pot at the end.
Sounds great though, dig it.

 

[cooder]

Gut shot. Chuck's relay switching works a treat.

 

[Chuck D. Bones]

YOWZA!

Looks great!

 

[szukalski]

+1 on that! Looks awesome, and with a great relay IO board!