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Author Topic: Passive Tone Circuit  (Read 25275 times)

phatt

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Passive Tone Circuit
« on: May 24, 2009, 10:18:18 AM »
My effort at tone controls.
Ok "Zappacat and sergscar" have asked for this one so here it is;
The "Tonemender circuit" has been mentioned more than once on these pages and although it works it could be quite easily improved. No disrespect to ROG but I get the impression not much effort goes into "Refining" there ideas. Nearly all these old styled passive tone circuits are quite prone to picking up noise but if you know your way around it they can be greatly improved. At the very least this will give DIYer's some other options to choose from that
I think most will find superior.

HiWatt tone does not get much mention (probably because it looks a little tricky) even though it was the best of all the famous tone stacks. In fairness it's no better than the classic Fender in regard to the Amount of bass and treble but the midrange cut leaves fender types for dead.
I doubt many will read all this but I have built a lot of these old circuits both Valve and SState so I'm fairly confident in stating how well they actually DO or Do Not perform.
If you are just hell bent on replicating a specific tone circuit then It should become obvious that you can use most of the old tone stacks in place of mine if you so wish.
For those that wish to replicate the EXact HiWatt circuit be aware that the bass pot was a *TRUE LOG* 500k unit and you may have trouble sourcing those nowadays.  What is often sold today has a psudo log curve and will be very disappointing in use.

I've tweaked the components for what I think is the best mid freq Q point and max cut, it's around 400hZ.
Play around with the values if you so wish but what you gain at some place you may loose out elsewhere. Like all the other tree type tone circuits the controls are very much interactive. There is No Gain/Boost with passive tone stacks so the game plan is all about making the biggest difference between frequencies. A deep notch cut is what you want as shallow scoops tend to sound unconvincing or bland.
Side note;
My Alesis Micro EQ cannot deliver the 30/35Db difference at 400hZ when compared to the passive HiWatt even though the Alesis is an Active parametric device,,, and yes I A/B tested this many times.

This schematic is version 2, which is better than the original circuit that I've already posted on this board. I've built 8 of these units for mostly working musicians and over time it became apparent that the noise/hiss
was an issue with some Hi gain Amps. This is all good because it forces me to work harder and find better ways to implement the circuit.
Very low noise opamps might help in extreme situations, I've used both TL072 and LM883 and you can hardly pick the difference by ear.

Be aware that altering or deleting R5(10k) will just increase the noise in quite a dramatic fashion but not the gain.
I discovered from some in-depth reading that this is how to do it and keeps the noise down. The 10k/10k voltage divider network (R5 and R6) seems to deliver the best results. Some here may have even better ideas so feel free to comment.
Also make VR4 100k lin or log if you need more power to drive your amp but don't go mad here as the noise will climb fast. The intention here was to just use this to balance the bypassed sound level and is not intended as a high gain section,, there are plenty of those around so use them for gain.

A good understanding of wiring up high impedance circuits helps as well. For those that may not fully understand,, Everything above R1 R2 R3 R4 in the tone stack is going to be prone to picking up unwanted crap,,
so just use metal film R's for the whole circuit and be done with it.

What! No active input? :duh
One of the not so obvious subtleties of famous valve driven tone stages was the simple fact that the output of the tone stage had a natural roll off in the high freq response.
With an active opamp buffer stage front-end this may not happen so by using the tone passively you are likely getting closer to the original Valve Tone effect. The passive tone stack input imp is plenty high enough for the magnetic PU's used in electric guitars.
Feel free to use a buffer in front but don't expect it to be vastly
improved.
When players first hear this box there is often a comment about the presence/brightness,, so again attaining more hi freq will likely render it more SState sounding which is the very thing your probably trying to avoid. so your call.
And for those that think it can't work passively you need to go way way back as this was how it was done in some early equipment.

How to use;
The treble dominates the tone in old standard fenders and I wanted to avoid that as much as I could. So if you want the treble to sparkle with this one,, just turn down the mid as it is now the dominant control.
I've deliberately tilted the output slightly to the treble freq but without loosing to much bass.
If you want more bass make R1 smaller, try 56k. Lower values will likely upset the mid cut ability.
Now I've bored you long enough so here's The schematic and some pictures that might give you some ideas of how to build it. I use the old printer selector boxes, you can pick them up for next to nothing as they are of no use anymore.
I do this cause someone may as well benifit from all my frustrations of trying to get a decent sound.
After 20 plus years of fiddlin with circuits,,, on rare occasions you have a win and I think this is one time I did pull something off that actually worked.
Have fun with it, Phil.

*Edit*  Just a note, Scroll down for the up to date SCHEMATIC. Cheers, Phil.
« Last Edit: January 16, 2010, 07:45:23 AM by phatt »

sergscar

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Re: Passive Tone Circuit
« Reply #1 on: May 25, 2009, 11:02:41 AM »
Hi Phil,
Thanks a lot for your post !
I'll squeeze my brains (with the help of the "Eagle" PCB software...) to create a PCB layout and proceed building the circuit.
I don't know if I can find the "printer selector boxes" here but, if not, I'm pretty sure some alternatives may arise.
Keep you posted abt outcomes !
B'rgrds,
Sergio
Guitars: Hondo II Les Paul '79, Crafter FW-770 EQ (steel) '96, Edwards ESP Strato '02, Acoustic Yacopi (nylon) '09, Fender Strat MIM S/S/H '05
Amps: "Scarface" Ruby, Dean DGX-12, Laney TF-200
USB Interfaces: M-Audio JamLab, M-Audio FastTrack Pro
Mic: HSR 3.2 Multipatern Condenser

phatt

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Re: Passive Tone Circuit
« Reply #2 on: May 27, 2009, 08:57:05 AM »
Hi sergscar,
Here's a pic of how I do it,,, might help?
I use eagle but I do the boards by hand as most of my stuff is simple and for one off's it's not worth all the bother. 
I just use a fine tip oil pen and etch the thing, Eagle just helps to keep all my centre pops exact. I print out a mirror on paper tape it to a blank,, lightly C pop all holes,,,then just join the dots,, etcxh and drill.
Of course you would not do it like this if you went into mass production. :loco

Note: This is the earlier version so it's not exactly the same.

Cheers Phil

sergscar

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Re: Passive Tone Circuit
« Reply #3 on: May 27, 2009, 09:31:08 AM »
Hi Phil,
Big help, of course !
I already had "throwed" all the components inside "Eagle", but some doubts always arise, and the picture clarified most of them.
I've installed Eagle a few days ago, just for doing the "Passive tone circuit" and takes some time to learn the "how to" (in particular, I'm feeling some difficulties for finding the right components in the libraries). Maybe there are easier softwares out there.

Just one more question: COM1, COM2 and COM3 are the Ground connectors for "IN", "LED/-Vcc" and "OUT", respectively ?

Thks again !
« Last Edit: May 27, 2009, 09:57:42 AM by sergscar »
Guitars: Hondo II Les Paul '79, Crafter FW-770 EQ (steel) '96, Edwards ESP Strato '02, Acoustic Yacopi (nylon) '09, Fender Strat MIM S/S/H '05
Amps: "Scarface" Ruby, Dean DGX-12, Laney TF-200
USB Interfaces: M-Audio JamLab, M-Audio FastTrack Pro
Mic: HSR 3.2 Multipatern Condenser

Zappacat

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Re: Passive Tone Circuit
« Reply #4 on: May 27, 2009, 02:41:41 PM »
Hi Phil,
Big help, of course !
I already had "throwed" all the components inside "Eagle", but some doubts always arise, and the picture clarified most of them.
I've installed Eagle a few days ago, just for doing the "Passive tone circuit" and takes some time to learn the "how to" (in particular, I'm feeling some difficulties for finding the right components in the libraries). Maybe there are easier softwares out there.

Just one more question: COM1, COM2 and COM3 are the Ground connectors for "IN", "LED/-Vcc" and "OUT", respectively ?

Thks again !


I've been doing the same thing.  What did you end up using for the variable resistors/POTS in the Eagle component library?  Also, are you sticking to a particular size/brand when it comes to capacitors and resistors?  I wish I knew more about this stuff but I'm taking a stab at it anyway.  Anxious to hear what Phil has to say about the above question of yours.  I found this link http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=110 when learning about Eagle.  It may not apply to this project but it's interesting and informative.  I'm making an LM3886 right now just to get used to the Eagle component.library editor.
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.

sergscar

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Re: Passive Tone Circuit
« Reply #5 on: May 27, 2009, 10:46:30 PM »
Hi Zappacat,
As I told before, i'm also in the 'learning phase', and I'm very impressed, since I discovered that many shcematics you find in the net can be reproduced by this mean.

You can search the components within the libraries by clicking the "add" button in the left tools' panel, since this will show you search box (down-left).

I quote, here below, the ones I used:

POT: TRIM_US-CIP20C-6MM .
Resistors: R-US_0204/2V (you can change the 2V for something higher...)
Capacitors: CPOL-US085CS-1AR should be ok... (those have polarity)
IC: TL072D (you will have to add it in 2 parts in the schematic, since the pins are splitted in 2)
Power supply: +18V
Jacks: DCJ0202
Led: LED
Diode: 1N4004 (you can change the value...)
Capacitors (wout polarity): CYYC7B5

I guess that's it...
Maybe the components I used are not the right ones, but I guess they accomplish with my needs of designing the board.

Concerning the "tutorial", I do suggest you to download this file:
ftp://ftp.cadsoft.de/eagle/userfiles/doc/veic_pcb_layout_tutorial_010709.doc

In my opinion, this is the best tutorial you will find outthere.

Hope the above of help
regards,
Sergio

Guitars: Hondo II Les Paul '79, Crafter FW-770 EQ (steel) '96, Edwards ESP Strato '02, Acoustic Yacopi (nylon) '09, Fender Strat MIM S/S/H '05
Amps: "Scarface" Ruby, Dean DGX-12, Laney TF-200
USB Interfaces: M-Audio JamLab, M-Audio FastTrack Pro
Mic: HSR 3.2 Multipatern Condenser

Zappacat

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Re: Passive Tone Circuit
« Reply #6 on: May 27, 2009, 11:56:17 PM »
I'm missing the power input stage, the input and output jacks and I need to change the symbols for some of the polarized capacitors.  I'm not sure where the ground symbols are in Eagle.  Also, are there input/output jacks in Eagle?  What heading are they under?  Where are the batteries?

I guess I screwed up on the TL072D.  I found something with similar name(TL072P) and appearance and just dragged it onto the circuit.  Please tell me what other errors you see.

Thanks!

Here's what I've got done in Eagle so far:
***Linked content removed due to malware***
« Last Edit: May 31, 2016, 09:06:09 PM by joecool85 »
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.

iTzALLgoOD

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Re: Passive Tone Circuit
« Reply #7 on: May 28, 2009, 09:33:18 AM »
Have you downloaded the GM libraries for Eagle?  It is set-up almost perfect for most of the stuff we do here. I'll see if I can find a link.

here ya go.  Click on the link and follow the destructions.

http://gaussmarkov.net/wordpress/tools/software/eagle-cad/
« Last Edit: May 28, 2009, 09:35:46 AM by iTzALLgoOD »

phatt

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Re: Passive Tone Circuit
« Reply #8 on: May 28, 2009, 10:33:59 AM »
First my sincere apoligies as I fluffed the schmo,, opps.
No pain as it works both ways which is why I probably gooffed it up cause I've built it both ways and my ears can't tell the diff.  A sim reveals very little difference also.
Just the same I should have been more careful. :trouble  (the bats for me.)

Obviously a little trouble with Eagle.
So here goes;
1/
Pots are *piher PC16S* these are very close to the 16mm pot I use.
2/
  Com1,2,3 are just *wire pads* renamed you just have to give them different names.
3/
  If you want to change a component just click the little *spanner* and select *package*
this brings up the part list again.
4/
  I struggeld with opamp packages so I just used the *dil* and select dil8 for my needs it's fine as you know the pinouts.
Zappacat note that VR2 and VR3 have the wiper not connected, you need to fix that.

As I don't mount the sockets on the board there is no need for them which is probably good cause I've never found a part that comes close to standard 6.5 either.

I have found those onboard mounted sockets can be a pain and are often the thing that breaks down first.
so standard chassis mount and hand wire up for me.


Again sorry for stuffup, I guess my only excuse is it a hobby and I'm not making money from it. thanks Phil.  Here is a couple of shoots of my file.
« Last Edit: May 28, 2009, 11:05:39 AM by phatt »

phatt

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Re: Passive Tone Circuit
« Reply #9 on: May 28, 2009, 10:46:28 AM »
Have you downloaded the GM libraries for Eagle?  It is set-up almost perfect for most of the stuff we do here. I'll see if I can find a link.

here ya go.  Click on the link and follow the destructions.

http://gaussmarkov.net/wordpress/tools/software/eagle-cad/

Thanks I'll look into that myself but not until these chaps have sorted their issues.
I hate updating programs in the middle of using them as something always goes fut and you end up in a nightmare not being able to find /access a file.
Cheers Phil.
« Last Edit: May 28, 2009, 11:06:28 AM by phatt »

Zappacat

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Re: Passive Tone Circuit
« Reply #10 on: May 28, 2009, 06:13:22 PM »
Now, I've made it to this point.  Please critique this Eagle schematic.  I know I've got some things to clear up.  Specifically the implementation of :

IC: TL072D, capacitor polarity, battery source?

I can't find an exact match for 1N4001 or TL072 in the Eagle libraries that I have.  Any suggestions?

Any feedback greatly appreciated.

***Linked content removed due to malware***
« Last Edit: May 31, 2016, 09:07:16 PM by joecool85 »
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.

sergscar

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Re: Passive Tone Circuit
« Reply #11 on: May 28, 2009, 08:56:59 PM »
Hi, by the time being, detected some items to adjust:
- Polarity of TL072 is inverted, therefore, you'll have to change the connections accgly
- Polarity of Battery, Led and 1N4001 are inverted

Also, pls note Phil marked some changes on C3 position (check his previous post), and yours is still unchanged

I will try to follow his new schema, and post the result later

Poor Phil, he will have to be patient with both of us...  0:)
Guitars: Hondo II Les Paul '79, Crafter FW-770 EQ (steel) '96, Edwards ESP Strato '02, Acoustic Yacopi (nylon) '09, Fender Strat MIM S/S/H '05
Amps: "Scarface" Ruby, Dean DGX-12, Laney TF-200
USB Interfaces: M-Audio JamLab, M-Audio FastTrack Pro
Mic: HSR 3.2 Multipatern Condenser

phatt

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Re: Passive Tone Circuit
« Reply #12 on: May 31, 2009, 11:46:27 AM »
I thought you chaps where going to breadboard it all first?
But hey if you want to just dive in I'll help as best I can,
Phil.

phatt

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Re: Passive Tone Circuit
« Reply #13 on: June 08, 2009, 10:12:16 AM »
Just adding Something to help you understand why this works so well.
Here is a snapshot of shootout between the *Tonemender and the PhAbbTone*.

Tonemender is average, at around 13dB cut in the mid.

The PhAbbTone big mid notch is clearly evident and my 30dB cut claim is really quite conservitive.
That deep mid notch does amazing things when used in front of even the most basic tube screamer OD pedal.

BTW all those frequency altering switches and add-ons only really shift the mid point up or down a bit and in reality are not much use (IMO)
I have built The famous Dumble tone stack and it's another one that shifts the mid around but nowhere near as powerfull as the HiWatt setup.
Cheers, Phil.

Zappacat

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Re: Passive Tone Circuit
« Reply #14 on: June 09, 2009, 01:10:06 AM »
Just adding Something to help you understand why this works so well.
Here is a snapshot of shootout between the *Tonemender and the PhAbbTone*.

Tonemender is average, at around 13dB cut in the mid.

The PhAbbTone big mid notch is clearly evident and my 30dB cut claim is really quite conservitive.
That deep mid notch does amazing things when used in front of even the most basic tube screamer OD pedal.

BTW all those frequency altering switches and add-ons only really shift the mid point up or down a bit and in reality are not much use (IMO)
I have built The famous Dumble tone stack and it's another one that shifts the mid around but nowhere near as powerfull as the HiWatt setup.
Cheers, Phil.
How did you plot that graphic out like that?  Is it some form of oscilloscope?  Do you hook up your guitar -> tonestack -> input on your scope or computer and strum the guitar?  You have me perplexed!
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.