# Timmy chip replacement...



## Nork (Mar 27, 2010)

Hey guys -

I'm in need of some help before I sell my Timmy. I'm looking for a Canadian dealer that will sell me an LM1458 - just one. I tried Abba Electronic in Montreal, but they have a 50$ min on online purchases. I only need one, lol. Is there anywhere I can pick one up that I don't have to wait for it to come over from China? Haven't had any luck at The Source here in Ottawa. Anyone in Ottawa know of anywhere to pick on up?

Also - dumb question - what sort of brand do you look for when it comes to this stuff or does it even matter?

Thanks guys!


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## Cups (Jan 5, 2010)

Is this some mod that will help you sell the pedal for more money? If you need it for a fix that's fine but unless you sell the pedal for 20$ more because of the chip don't bother.

Here's a link to a small, dedicated pedal parts store in NY: IC LM1458

0.60$ for the chip. I'm sure it's a good 5$ for shipping.

As for the sound; it's an overdrive pedal. It's not hifi. You may notice a difference in noise but a difference in tone is ..... subjective at best.


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## mhammer (Nov 30, 2007)

You're in Ottawa. I'm in Ottawa. I have a bunch of them. Drop me a note and we'll figure out a way and time to get the part to you.


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## Nork (Mar 27, 2010)

I've seen a more than a few posts on the web about op-amp switches in the Timmy making a difference. Paul himself put the 1458 in his green Timmy for Humbucker to get a different sound. Figured it's a cheap "mod", can't hurt. 

I'm actually hoping to not sell it, but with its current tone, the Voyager beats it currently.


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## sulphur (Jun 2, 2011)

The same chip in the Tim, I'm assuming?

I wouldn't mind trying this out.

Let us know what you think when you make the change.


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## Nork (Mar 27, 2010)

I don't know about the Tim, though I suspect so. I've read lots of chip swapping done over on TGP, even at one point found a whole list of samples from chip swaps guys have done. I was ready to sell the pedal, but after reading that the chip swap can make quite a bit of difference, and hearing some of that difference for myself, I figured it was worth the shot if it means I keep it. 

Here's what Paul said about the swap: http://www.thegearpage.net/board/showthread.php?t=1112313&highlight=surf+green+timmy


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## mhammer (Nov 30, 2007)

sulphur said:


> The same chip in the Tim, I'm assuming?
> 
> I wouldn't mind trying this out.
> 
> Let us know what you think when you make the change.


When Nork comes over, we can pop in a bunch of different chips and see if the 1458 provides an audible improvement. Personally, I'm disinclined to place much creedence in such chip magic, when:
a) the persons reporting have sent their pedal away and gotten it back later (auditory memory not being much bloody use in that circumstance)
b) the context the pedal is used in remains unspecified or is otherwise "special".

That doesn't necessarily mean there is any sort of snake oil sale, scam, or bunk. It may simply be that the alternate part requires very special circumstances to produce audible difference, and those circumstances may eother occur very rarely, or not at all for any given player.

So, the gain/bandwidth limitations of a substitute chip may have an impact on the tone achieved for someone playing a Strat with 1M volume pot through a $100 10ft cable into an amp with such-and-such extended-range speakers and a specially-wound mercury Magnetics output transformer, but mean absolutely bupkes for someone playing an Epiphone Les Paul through a budget 25ft cable into a Marshall MG50.

I'm game to try it out, though. Several years back, I posted a soundfile I had made that demonstrated a bunch of different op-amps in a Distortion+ clone, including a "stacked chip" (as per Dave Barber's suggestions) where the pins of a pair of 5534 chips were soldered together and the composite plugged into the socket. There were audible differences, but part of it was really because the biasing in the Dist+ was set up _specifically_ for the LM741 (i.e., NOT for any of the other chips used), and another part because the 741 clips even without diodes (so the pedal is technically a double clipper). In some respects, the conclusion of the soundfile was akin to "Man, this screwdriver is awful! I couldn't get ANY soup to stay on it."


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## Nork (Mar 27, 2010)

It's a socketed IC, so guys just pop'em in at home usually.


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## sulphur (Jun 2, 2011)

I see what you're saying Mark, but as Nork stated, it's a simple as pulling one out and slapping in the other.
Who sends their pedal away to have that performed on them?

There is some slight bit of harshness, especially when stacked I found with the Tim.
I've read elsewhere, that guys did this mod and it smoothed it out somewhat.
Snakeoil maybe, but if someone is willing to try it, with a couple different sets of ears,
not just the guy doing the mod, we might get some useable results.


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## sulphur (Jun 2, 2011)

I've wanted to try this on my Rockett Flex Drive too.

The op-amp is directly mounted under the tone pot.
So wouldn't that make a difference to the tone if replaced?

Of course, I'm in the same boat, nowhere local to pick any of these up,
and I'm not about to buy in bulk.


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## Jeff B. (Feb 20, 2010)

sulphur said:


> I've wanted to try this on my Rockett Flex Drive too.
> 
> The op-amp is directly mounted under the tone pot.
> So wouldn't that make a difference to the tone if replaced?
> ...


 The position of the IC and the Tone control would be unrelated as the circuit board traces could lead anywhere and connect to anything. Back tracing the circuit or having the schematic would let you know for certain what it interacts with. I have all kinds of LM1458 IC's, I use them in Pistol Slapper's. When I was doing side by side comparisons in that circuit last year I found the TL082 to be very close in sound to the LM1458.

EDIT: It's the MC1458's I have and use. Mark's post jogged my memory, I had thrown them in the LM1458 drawer and didn't change the label.


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## mhammer (Nov 30, 2007)

So we did the experiment, maintaining the same settings, or as close as we could , using a variety of chips, my Turser Tele with the handwound pickups and my faithful tweed Princeton.

We auditioned:
OP275
LM833
CA3240
JRC4558D
HA17458
TL272
MC1458

We never got around to LF442, TL082, TL072, LF353, NE5532. Rereading the thread now, I should have pulled out the TL082 earlier.

The OP275 sounded more hi-fi-ish.
The LM833 sounded kind of ugly.
The TL272 distorted harder.
The JRC4558D didn't sound that much different than the 4559.
The CA3240 didn't sound that bad if your goal was a more nasal or throaty sounding overdrive (worth trying out).
The HA17458 (supposedly a Harris version of 1458, but different internally) sounded a bit better than 4559, but didn't win us over.
The Motorola MC1458 was the hands down winner. Took some of the nasty top off.

Personally, I would have also increased the feedback capacitor in the clipping stage beyond the stock 100pf to roll off even more of the nasty top end, but it wasn't my unit to dicker with, so we just changed chips and left it at that.

I hadn't expected to hear that much difference, but it was there. In one sense, not that surprising, since the Timmy uses diodes in the feedback loop like the Tube Screamer, and folks have proposed that the reason for the JRC4558D being preferred for the TS9/808 is its interaction with those clipping diodes. And we did hear the 4558 producing more of an overdrive sound, compared to some of the others. What I imagine the clincher was, though, was the limited bandwidth of the 1458. This was particularly the case since the Timmy doesn't do that much treble trimming. At min gain and full treble the Timmy imposes only a very shallow rolloff starting around 10.6khz. Turn the gain up full tilt, and you have a rolloff around 1.5khz, which is helpful when used in conjunction with the treble control. But at, say, 1/3 gain, there is very little treble trimming available on-board. You end up having to tame the sizzle from the guitar and amp. We also found it became more acceptable with a warmer speaker when we switched over to one.

Still, I think the Timmy stands to be improved by having more bandwidth limiting available in the clipping stage itself, rather than afterwards. But that's me. I also wish it was possible to A/B these thngs more easily. Having a pair of Timmys with different chips and blind A/B testing would have been much better.

All in all, a successful experiment.


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## Nork (Mar 27, 2010)

Fantastic experiment. Tks for a) having me over b) letting me play that Princeton and c) teaching me a bunch. And, of course for the LM1458. Sorry for being a wimp with the circuitry dinking.


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## mhammer (Nov 30, 2007)

Nothing to apologize for. If you knew for a fact that you were NEVER going to sell the Timmy, or that you could easily reverse any changes made should it come time to place it in someone else's hands, that would be one thing. Being reticent about what you don't know how to undo is a perfectly normal response.

Great finish on that pedal BTW. The equal of older ZVex pedals. The functioning of the bass and treble pots is a little counter-intuitive, but easy to get used to, I suppose. Very well made, though. 

And yeah, a bunch of fun trying out those chips. Kinda made me wish I had a portable digital recorder so that each chip change could be directly compared, and available for others to compare as well.


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## Nork (Mar 27, 2010)

Yea. I'll have a look around and see if can't find that sound byte of someone who did just that.


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## greco (Jul 15, 2007)

Sounds like you guys had a great time !

Post #12 is fascinating.

Cheers

Dave


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## Rugburn (Jan 14, 2009)

greco said:


> Sounds like you guys had a great time !
> 
> Post #12 is *fascinating.
> 
> ...


It was *fascinating!!

*[video=youtube;cFods1KSWsQ]http://www.youtube.com/watch?v=cFods1KSWsQ[/video]


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## mhammer (Nov 30, 2007)

greco said:


> Sounds like you guys had a great time !
> 
> Post #12 is fascinating.


Thanks, and yes we did.

I think I accurately conveyed what we thought we heard. I will still emphasize that:
a) we tried to make sure the amp, guitar, and pedal settings remained constant when comparing, but I still had to flip the pedal over to change chips, and we still had to turn the amp down between chip-changes because of the annoying hum produced by the fluorescent lights in the garage; maybe we kept things constant...and maybe we didn't;
b) my guitar and amp is not your guitar and amp, or your picking style;
c) we didn't realize until we were a few chips into it, that Nick/Nork had the guitar's tone control rolled back (the guitar has a bidirectional tone control with no rolloff in the middle, and two different rolloffs going outwards in each direction from there - I was busy trying to quickly change chips while he played, and he mistakenly thought he had it at full treble).

So, there are a number of possible reasons why what seemed to sound better to us did so. I am interested to hear Nick's impression of how it sounds with his guitar through his rig. Hopefully my garage setup did not deceive either of us.


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## Nork (Mar 27, 2010)

So I finally took the Timmy for a run. G&amp;L ASAT Tribute through a Vox AC15C1 (no bright cap mod yet). 

The LM1458 makes quite difference - took it apart and switched chips and it's very different from the 4559. Smoother, less harsh and brittle in the higher register, and the breakup is more organic (??). Less fizz, little more growl. 

The Timmy is billed as a "your amp just more" pedal and it lives up to its name. The Vox's chime and sparkle are still there, but the pedal no longer thins it right out. 

Tks so much, Mark!


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## mhammer (Nov 30, 2007)

Thanks for the feedback.

We too often extrapolate unreasonably from the audiophile realm to the music realm (specifically guitar) or vice versa. There are things that matter a whole lot in the one context, that either don't matter in the other, or else matter in a completely different way. People learn something about capacitors or wire in high end stereo amps and assume that the qualities found desirable there apply to pedals or guitars, and that is not always the case.

In this instance, the 1458 (and its an MC in your pedal not an LM, Motorola versus National Semiconductor) would be considered a poor choice for op-amp in something designed for reproduction of wide bandwidth sound. Lousy slew rate, lousy gain-bandwidth product. If I saw one in a stereo amp, I'd be trying to replace it with something "better" within the hour. But in this instance, the chip's* inability *to deliver wide bandwidth at high gain is specifically what improves the sound in the Timmy. The same chip used elsewhere might not deliver ANY improvement whatsoever. For instance, one would not replace the TL072 dual op-amps in a digital delay pedal with MC1458 to "make the sound warmer", since such pedals would be using the chip at unity gain, or close to it, where the chip would have the same bandwidth as a wide range of other choices, but worse noise specs.

Same thing for the Proco Rat. The LM308 used in it is also a poorer choice of chip than the many others available, but its poorer performance is critical to the classic sound of the Rat, which pushes it beyond its capabilities.


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