SRV tone with pedal

[Cub]

That was incredible! Your tone got a lot closer to _that_ tone than I heard in many TS clone videos. Man, I want to build that box!

While we're on the subject of passive little helpers, what's your opinion on the Defizzerator?
https://paulinthelab.blogspot.com/2017/10/amptweaker-defizzerator-stripboard.html

[John G]

Hi,
Many years ago a dude by the name of Gil Ayan, made a similar box called (I think) SMOOTH AND SLIM.
He also came up with the input bass reduction mod to the Mesa MK I amp..................... Legend.
John

[Intripped]

many thanks phatt, for this great little tip!

[phatt]

That was incredible! Your tone got a lot closer to _that_ tone than I heard in many TS clone videos. Man, I want to build that box!

While we're on the subject of passive little helpers, what's your opinion on the Defizzerator?
https://paulinthelab.blogspot.com/2017/10/amptweaker-defizzerator-stripboard.html

Hello Cub,, Yes I believe that this is how SRV got THAT tone. But of course no one will ever know
but His brother is still around and I'd bet he has the original splitter box and that would
be the most obvious place to impliment (hide) a couple of resistors and a cap.
Meanwhile the whole teck world has modded a thousand amps and still can't quite nail the sound.

I think the fact that it is just so dead simple they all missed it.
Technical minds tend to assume it must be complex but IMExperimentaion it may well have been this simple.

Here is a dwaring of what is in the box on my video.



This drawing only shows 5 position so just add another stage for 6 positions.
I used 5n6 which gives you 5n6 down to 1n8 at pos 5,, (1n4 at pos 6 on my box)

Just plug that into a standard Hi Z input of any of those old Amps that Stevie would have used,,,
and Bob is your auntie's husband.
I doubt it will work well on a lot of modern higain Amps as they are more about preamp gain distortion
but suck it and see.

Other stuff I wanted to mention but just not enough time on the Video;
I think this trick does more than just forming a hipass filter.
All Magnetic PU's are inductive and have a distinct hump when looking into a hiZ input.
Better minds can explain the terms but in general I think the hotter PU's and more wire turns the bigger the hump.
But if you load down that input (in this case lower than 100k) then that hump is gone it's then a flat response.
That hump may well be the brittleness I hear on some of those hotrod amp rigs.
Thanks to that very much missed man (Roly Roper RIP peace mate, I miss you)
He has a page on PU's at AVA where it clearly shows in graphics how the input Z loads down that hump.

Page is here; http://ozvalveamps.org/pickups.htm

about halfway down you find the graphs
It explains bare PU, then Cable capacitance,, then input loading.
It's the input loading that shows that hump I'm talking about.
At 100k input Z the hump is gone,, you are down -3dB and the bandwidth is limited to around 4khZ.
EEK we have lost all that treble.

I say think again;
You have heard the clip I posted,, did it; improve treble? improve note definition?
Improve guitar amp interaction? My ears tell me it improves the treble.

By adding the high pass cap you have Refocused the tone response. The treble is now focused in the area of the freq
that the guitar works best.
20/20 bandwidth for guitar amps is just going to make it so much harder to dial in tones,,too much clutter.

Sometimes better is the enemy of good.
IMH experience, this cap trick forms the core of the tonal signature of that famous Texas tone thang. (and likely used by other famous players in the know)
All the amp mod tricks I've heard do not capture the sound for reasons explained above. I'd agree that some are very close but anything on the market that sounds like SRV will cost you a fortune,,,meanwhile a capacitor costs 10cents.

Re the *Defizzerator* best I can make out is that it's a hi CUT filter, not sure how the pot is connected?
I assume it would cut treble and lower the input Z.
Brand names escape me but some really old guitar circuits actually had switchable series caps,, how well they worked I have no idea?
Phil.

[phatt]

Hi,
Many years ago a dude by the name of Gil Ayan, made a similar box called (I think) SMOOTH AND SLIM.
He also came up with the input bass reduction mod to the Mesa MK I amp..................... Legend.
John

well I just found this page;
https://reverb.com/item/3431481-used-ay ... slim-fx062

Having read the whole page it certainly seems to be very similar to what I've done,, As I mentioned I figured that someone else would have worked this out as it's so simple. If you are interested in this idea it's worth reading the whole of the above link,, click on MORE to get the whole artical.
Phil.

[lcv]

Hi Phatt
Great concept!
One question: in your hipass implementation, why is it necessary to halve the output voltage after the series cap?
Thanks
Lcv

[Cub]

Thanks again, Phil! for your detailed explanation, that'll be a fun little build to do.
A very interesting read on pickups as well. I have to sit and read it more thoroughly soon.

The Defizzerator goes in the effectsloop of modern tube amps to suck up some of the fizz, it sounds very promising in clips.

[phatt]

Hi Phatt
Great concept!
One question: in your hipass implementation, why is it necessary to halve the output voltage after the series cap?
Thanks
Lcv

If you series connect a 1n5 cap directly into the Hi Z input of most guitar amps you would be hard pressed to notice any difference
Because at hi Z which is most guit Amps (the typical 33k/1meg divider) the cap would have to be at least x10 lower in value to get the same roll off curve.
So 1n5 would then need to be ~ 150pF which would *kinda* work. EXCEPT!!!! you will still have that Resonant peak from the PU I mentioned which would make the treble much harder to control.

This is all to do with RC maths and Z (impedance) which is just the effective resistance of an AC circuit.

A couple of links that may help;
https://www.electronics-tutorials.ws/fi ... ter_3.html

http://www.johnhearfield.com/RC/RC1.htm
(scroll down to *Impedance* if you don't want to read it all)

http://www.learnabout-electronics.org/O ... /osc31.php

The classic tone stack circuits are HiZ and they can be converted to low Z by *decreasing* all the resistance values
x 10 and *Increasing* all the cap values x10. Of course there is always a trade off and low Z tone circuits don't interact quite the same way as the old Hi Z circuits which is why hi Z tone stacks are still around.
All about Z and RC networks.

Whatever you build tiss wise to breadboard a test circuit first because no matter how good the demo on the Utube sounds it may sound like crap through your rig.

HTH, Phil.

[phatt]

Thanks again, Phil! for your detailed explanation, that'll be a fun little build to do.
A very interesting read on pickups as well. I have to sit and read it more thoroughly soon.

The Defizzerator goes in the effectsloop of modern tube amps to suck up some of the fizz, it sounds very promising in clips.

Ah huh,, Thanks, makes sense now. that would help reduce the brittle hi freq crud.
My stock answer to young folks who struggle to get all the classic Tones/Dist/Odrive effects.
TOO MUCH BANDWIDTH!!!! just destroys a good tone.
(I think) early Mesa mk1 Had 220k on V1 as do some Carvin rigs and likely others in the know.. It helps to keep that reso peak under control at hi volume levels.
Just hanging 1 meg resistors off every input is asking for problems especially with all the hi gain PU's that are now standard even on budget guitars.
Those Texas special pu's that get raved about are just horrible things, way too humpy.
If all you do is play at bedroom level then it's likely is not much of a problem but once you get up on stage and start cranking big volumes with lotsa dist all you archive is annoying the punters with extreme hi freq crud
Phil.

[lcv]

If you series connect a 1n5 cap directly into the Hi Z input of most guitar amps you would be hard pressed to notice any difference

Sorry , my question was not clear.
(I prepared a picture but apparently I can't paste them to posts....)

When asking "why is it necessary to halve the output voltage after the series cap?" I was referring to the voltage divider made by the two 68K .
The signal just after the cap is essentially (assuming the HiZ input load negligible ) the same signal you get from the divider (as per your original schematic) but without attenuation.
So my question about the necessity to attenuate it.
Maybe you wanted to emulate the "low input" kind of attenuation?
Thanks for the interesting links!
Lcv

[phatt]

If you series connect a 1n5 cap directly into the Hi Z input of most guitar amps you would be hard pressed to notice any difference

Sorry , my question was not clear.
(I prepared a picture but apparently I can't paste them to posts....)

When asking "why is it necessary to halve the output voltage after the series cap?" I was referring to the voltage divider made by the two 68K .
The signal just after the cap is essentially (assuming the HiZ input load negligible ) the same signal you get from the divider (as per your original schematic) but without attenuation.
So my question about the necessity to attenuate it.
Maybe you wanted to emulate the "low input" kind of attenuation?
Thanks for the interesting links!
Lcv

Sorry but I'm struggling to grasp the point/Q

I think one of us is missing something. head scratch?
Without the two 68k resistors the hi pass filter won't work.

Or put the other way around the cap will only work as a HPF through a lower Z which is created via the two 68k resistor divider.

By adding the cap creates the HPF filter.
Without the cap the two 68k R's are as you said,
a Voltage divider which has no effect on bass response except to turn down the sensitivity over the whole bandwidth.

You could remove the series R and still get a HPF but the curve would be different, I've not bothered to try it as you actually need a fair bit of attenuation. You don't want V1 to run hard.
Phil.

[phatt]

Oh forgot to mention re posting images,, you will need a hosting site,
I use; https://postimages.org/
It's basic but gets the job done. I'm sure others here will know of better sites.
Phil.

[lcv]

Thanks for your patience Phatt, now I managed to link an image (hopefully..)

https://imgur.com/BNvOzlc

My point is really simple (and minor if you want), I'm just saying that at node "B" you have basically an attenuated version of the signal present at node "A".
If we agree on this, then I'm fine with all the rest.
My original intended question was about the reason why the attenuated signal was chosen , and you explained it well:

.... you actually need a fair bit of attenuation. You don't want V1 to run hard.

Having said that, in my trials using your interfacing circuit I am feeding different kinds of effects and amps inputs.
I tend to use the "A" node as the output, because the non-attenuated signal eases the production of distortion down on the chain...
Hope this clarify
Best Regards
Lcv

[phatt]

Hi Lcv,
Arrh thanks,, Now I see what you mean.
OK yes that gives the HPF slope but it's cutoff point moves and also 5~6dB higher in output.

A screen shot of the circuit should help to clarify what's happening.


All three plots are taken at the grid of V1 (the Green box labeled A)
*Green* is your idea of tapping off at node A
Your drawing just puts the two 68k resistors in series to ground which is shown on my sim.
That just makes 136k to ground and only -3Db drop.
The *Yellow* plot is my box, down ~8Db
The blue plot is the normal HiZ input plot.
Note how the Yellow plot (my box) rolls off the treble a bit harder.

From what you say,,I take it you are inserting this *Before* pedals? If so, it will have some effect but I doubt you would get the full benifit as this needs to be in front of V1 to maximize the effect. V1 is the key point.
I have used it after my Acoustic guitar preamp *in front of pedal board* and it kinda helps the low freq feedbak problems but does little to back off the big signal that still hits V1 grid.

The whole point of this is to reshape the bass while also backing off the early preamp stages and then when you wind up the volume the PI and power valves will do the magic sweet OD.

This makes for a wide area of dynamic response and maximizes power stage compression giving lotsa sustain with far less triode hair on the notes.
A lot of stuff on the market now is all triode fizz and close to impossible to get a decent clean OD effect.

The Tube screamer was set with low gain and really just made the input signal a bit bigger which increased the SPL and added a bit more distortion.
Everyone got caught up with the idea that the TS box created the mojo but it was just a boost accessory. NOT THE MAGIC bullet.
Keep in mind that this has much better effect when the amp is close to full power,, at low volume levels this would sound a bit thin.

If you are into Speed metal and like tones with massive OD/Dist then this will likely be a big disappointment.
But if you want to experiment then go for it.
Phil.

[Cub]

Anybody up for a good laugh? I tried to make Phil's filter box, but failed miserably and I don't know why. At this moment, I'm ashamed to even own a soldering iron.

Here's a little drawing of what I made, could any of you please tell me where I went wrong ? It's in a plastic enclosure for now, perhaps that's worth mentioning. I wanted to try the sound first and then put it in a nice Hammond box later if I liked it.

[phatt]

No don't feel bad,, I'm the idiot. the drawing is actually wrong,
So tis good you have brought it to my attention.
Too late now but I'll repost the right drawing tomorrow.
Excuse me while I go bang my head against the wall.... I'm an efin idiot x100 times.
Phil.

[Cub]

So I did manage to translate the schematic to an accurate build, that's a relief.
Glad the error was caught before someone started making a badge of these boxes.

[phatt]

Hi,
Many years ago a dude by the name of Gil Ayan, made a similar box called (I think) SMOOTH AND SLIM.
He also came up with the input bass reduction mod to the Mesa MK I amp..................... Legend.
John

I did search around and Yes it looks like it's much the same idea with a 2 position switch. I was certain that someone would have worked this out before myself. I worked this out around 2002 so likely Gil made this around the same time.
Phil.

[phatt]

That was incredible! Your tone got a lot closer to _that_ tone than I heard in many TS clone videos. Man, I want to build that box!

While we're on the subject of passive little helpers, what's your opinion on the Defizzerator?
https://paulinthelab.blogspot.com/2017/10/amptweaker-defizzerator-stripboard.html

Hello Cub,, Yes I believe that this is how SRV got THAT tone. But of course no one will ever know
but His brother is still around and I'd bet he has the original splitter box and that would
be the most obvious place to impliment (hide) a couple of resistors and a cap.
Meanwhile the whole teck world has modded a thousand amps and still can't quite nail the sound.

I think the fact that it is just so dead simple they all missed it.
Technical minds tend to assume it must be complex but IMExperimentaion it may well have been this simple.

Here is a dwaring of what is in the box on my video.

[ Image ]

This drawing only shows 5 position so just add another stage for 6 positions.
I used 5n6 which gives you 5n6 down to 1n8 at pos 5,, (1n4 at pos 6 on my box)

Just plug that into a standard Hi Z input of any of those old Amps that Stevie would have used,,,
and Bob is your auntie's husband.
I doubt it will work well on a lot of modern higain Amps as they are more about preamp gain distortion
but suck it and see.

Other stuff I wanted to mention but just not enough time on the Video;
I think this trick does more than just forming a hipass filter.
All Magnetic PU's are inductive and have a distinct hump when looking into a hiZ input.
Better minds can explain the terms but in general I think the hotter PU's and more wire turns the bigger the hump.
But if you load down that input (in this case lower than 100k) then that hump is gone it's then a flat response.
That hump may well be the brittleness I hear on some of those hotrod amp rigs.
Thanks to that very much missed man (Roly Roper RIP peace mate, I miss you)
He has a page on PU's at AVA where it clearly shows in graphics how the input Z loads down that hump.

Page is here; http://ozvalveamps.org/pickups.htm

about halfway down you find the graphs
It explains bare PU, then Cable capacitance,, then input loading.
It's the input loading that shows that hump I'm talking about.
At 100k input Z the hump is gone,, you are down -3dB and the bandwidth is limited to around 4khZ.
EEK we have lost all that treble.

I say think again;
You have heard the clip I posted,, did it; improve treble? improve note definition?
Improve guitar amp interaction? My ears tell me it improves the treble.

By adding the high pass cap you have Refocused the tone response. The treble is now focused in the area of the freq
that the guitar works best.
20/20 bandwidth for guitar amps is just going to make it so much harder to dial in tones,,too much clutter.

Sometimes better is the enemy of good.
IMH experience, this cap trick forms the core of the tonal signature of that famous Texas tone thang. (and likely used by other famous players in the know)
All the amp mod tricks I've heard do not capture the sound for reasons explained above. I'd agree that some are very close but anything on the market that sounds like SRV will cost you a fortune,,,meanwhile a capacitor costs 10cents.

Re the *Defizzerator* best I can make out is that it's a hi CUT filter, not sure how the pot is connected?
I assume it would cut treble and lower the input Z.
Brand names escape me but some really old guitar circuits actually had switchable series caps,, how well they worked I have no idea?
Phil.

Well Hope I have not caused too much confusion
R2 was drawn wrong.
Here is the Corrected Drawing;


Hey Moderator; Is there any way I can delete the Wrong Drawing at top of this page?
Phil.

[Cub]

Well Hope I have not caused too much confusion
R2 was drawn wrong.
Here is the Corrected Drawing;
[ Image ]

Hey Moderator; Is there any way I can delete the Wrong Drawing at top of this page?
Phil.

It was a little mistake and an easy fix, glad it all ironed out so smoothly.

Here are my first impressions with a Tele and a small 15 Watt 1x12 tube amp on low levels (and a 33k resistor between the input and the plate)

After playing with it for a while with all the settings, the bypassed signal now sounds really thick in the lowend, the ears adjust quite quick to this little box! The setting that's the low input without a cut is a little dull and the thinnest two are too thin for this setup to sound useful. The two remaining settings are great and really bring a lot of clarity to this amp without ever sounding too thin or harsh or anything like that.

With any luck, I can try it with a 100 Watt Marshall JVM on top of a 4x12 with G12T75 speakers on Wednesday.