Paul Cochrane - Timmy  [traced]

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Re: Paul Cochrane - Timmy

Postby LooseCannon » 03 Aug 2014, 07:57

Could anyone please explain why the Drive pot is wired liked that with R3 going to the second terminal of the pot?

What effect would this give versus how it's wired on a TS9?

Thanks
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Re: Paul Cochrane - Timmy

Postby Nocentelli » 03 Aug 2014, 10:19

I think it makes little difference: The 3k3 (51k in TS) sets the minimum gain level: In the TS, this is in series with the zero ohms of pot resistance at minimum. In the timmy, the 3k3 is in parallel with 1M when the pot is at minimum, so is just a hair under 3k3. The timmy arrangement might have a tiny impact on the taper of the pot as the gain is increased since there's some parallel resistance going on, but I can't imagine it's significant.
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Re: Paul Cochrane - Timmy

Postby LooseCannon » 03 Aug 2014, 13:27

Thanks.

I built the Timmy with this layout, and although it seems to work properly i've compared it to the schematic and the Drive pot wiring doesn't look right. R3 should be connected to the -IN of the opamp, not to the output.

Would this change the drive pot operation?

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Re: Paul Cochrane - Timmy

Postby Nocentelli » 03 Aug 2014, 15:00

It will work just the same: the pot + 3k3 resistor act together as a single variable resistor, either way around is electrically identical.
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Re: Paul Cochrane - Timmy

Postby LooseCannon » 03 Aug 2014, 15:41

Thanks again.

Is it normal for the bass pot to decrease the gain as the bass is cut? Does it change the resistance of R4?

Also regarding R4 (the "maximum gain" resistor) what's the difference between using a lower value for the resistor and using a higher value gain pot?
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Re: Paul Cochrane - Timmy

Postby paulc » 06 Aug 2014, 01:42

LooseCannon wrote:Could anyone please explain why the Drive pot is wired liked that with R3 going to the second terminal of the pot?

What effect would this give versus how it's wired on a TS9?

Thanks


That was done just to make it easier to wire when I made them on generic perf board. No effect on taper or gain range.

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Re: Paul Cochrane - Timmy

Postby paulc » 06 Aug 2014, 01:59

LooseCannon wrote:Thanks again.

Is it normal for the bass pot to decrease the gain as the bass is cut? Does it change the resistance of R4?

Also regarding R4 (the "maximum gain" resistor) what's the difference between using a lower value for the resistor and using a higher value gain pot?


Yes - the bass control is part of the gain circuit. It increases the value of R4, but only in regards to the 1uf cap. R4 stays the same in regards to the 39nf. That's what makes it a shelf EQ instead of a 1st order.

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Re: Paul Cochrane - Timmy

Postby LooseCannon » 06 Aug 2014, 18:01

Thanks for the info Paul :)

After a lot of experimenting with the TS basic circuit i'm starting to to think that the tone control is what makes it midrangy and a bit muddy, I guess the rat style tone control is what makes the timmy more transparent.

(Although I know you started it off as a booster and not as a TS clone)
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Re: Paul Cochrane - Timmy

Postby mmolteratx » 06 Aug 2014, 18:31

LooseCannon wrote:Thanks for the info Paul :)

After a lot of experimenting with the TS basic circuit i'm starting to to think that the tone control is what makes it midrangy and a bit muddy, I guess the rat style tone control is what makes the timmy more transparent.

(Although I know you started it off as a booster and not as a TS clone)


The TS is middy because it cuts all of the bass pre clipping and all of the highs post clipping. That first stage only amplifies things above ~720Hz fully, with everything below decreasing in magnitude as frequency decreases. It also lops off high end, of which the exact cut off frequency varies depending on the drive control setting. You're looking at ~72kHz with the drive at minimum, and ~6kHz with the drive at max. Then after that stage, another filter cuts off high end starting around ~720Hz. Then the tone control boosts or cuts frequencies above ~3.2kHz.

The Timmy is transparent because the tone controls go pretty much completely flat in the guitar's range.
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Re: Paul Cochrane - Timmy

Postby LooseCannon » 06 Aug 2014, 19:03

mmolteratx wrote:It also lops off high end, of which the exact cut off frequency varies depending on the drive control setting. You're looking at ~72kHz with the drive at minimum, and ~6kHz with the drive at max. Then after that stage, another filter cuts off high end starting around ~720Hz.


At what stage does that happen? Are you talking about the 1k resistor and the .22 cap at the output of the first opamp?
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Re: Paul Cochrane - Timmy

Postby mmolteratx » 06 Aug 2014, 20:32

LooseCannon wrote:
mmolteratx wrote:It also lops off high end, of which the exact cut off frequency varies depending on the drive control setting. You're looking at ~72kHz with the drive at minimum, and ~6kHz with the drive at max. Then after that stage, another filter cuts off high end starting around ~720Hz.


At what stage does that happen? Are you talking about the 1k resistor and the .22 cap at the output of the first opamp?


The 1k/.22u is the last low pass filter I was talking about.
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Re: Paul Cochrane - Timmy

Postby LooseCannon » 06 Aug 2014, 21:10

So what cuts off the high end before that?
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Re: Paul Cochrane - Timmy

Postby mmolteratx » 06 Aug 2014, 23:37

LooseCannon wrote:So what cuts off the high end before that?


The 47p cap across the drive control/clippers.
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Re: Paul Cochrane - Timmy

Postby Nacho5 » 03 Nov 2014, 20:53

rocklander wrote:still unverified.. but here's an update.

layout1.10-rocklander2013(c).jpg


pcb1.10-rocklander2013.jpg



Thanks for PCB, what size is the pcb to etching?
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Re: Paul Cochrane - Timmy

Postby rocklander » 03 Nov 2014, 22:05

Nacho5 wrote:
rocklander wrote:still unverified.. but here's an update.

layout1.10-rocklander2013(c).jpg


pcb1.10-rocklander2013.jpg



Thanks for PCB, what size is the pcb to etching?

no worries.. it's the size where you print it out and the opamp fits.. no idea sorry as I've never made it.
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Re: Paul Cochrane - Timmy

Postby jimwoud » 10 Aug 2016, 12:00

Hi All!

I want to make a Timmy Clone, but want to be able to cut more bass and have more treble available.

What do you recommend to change?

Thank you,

Jim
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Re: Paul Cochrane - Timmy

Postby swt » 11 Mar 2017, 20:37

hi. can you tell me the tonal differences between 4558, 4559 and 4560?. thanks a lot
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Re: Paul Cochrane - Timmy

Postby mlp-mx6 » 12 Mar 2017, 02:17

swt wrote:hi. can you tell me the tonal differences between 4558, 4559 and 4560?. thanks a lot

Undetectable, if they exist at all.
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Re: Paul Cochrane - Timmy

Postby mictester » 12 Mar 2017, 04:30

swt wrote:hi. can you tell me the tonal differences between 4558, 4559 and 4560?. thanks a lot


Nothing at all, except the newer devices will hiss slightly less.
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Re: Paul Cochrane - Timmy

Postby swt » 13 Mar 2017, 14:56

ok thanks a lot. i read somewhere that the 4559 is darker and distorts more and just wanna check if this is true.
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