[OT] What if an active buffer is too bright?

[zooey]

My main guitar has an active buffer in it (Stratoblaster clone), to keep the tone consistent as you turn down the guitar volume. It's been in the shop for a while, just got it back, and in the mean time I've been playing another guitar with no buffer. Apparently I've gotten used to that sound, since it sounds to me like my main one has too much in the way-highs.

 

What I'd like to do is keep the buffer for that tone consistency, but add a fixed cap to roll off some of that very top end.

 

Has anyone done that? Any idea what size capacitor would be appropriate?

 

Thanks.

[Joepeggio]

try to lower the input impedance in the helix global settings. may be a non permanent solution.

 

I'm not sure cap to use. Crack the tone knob just off max?

i personally am not a fan of hard wiring something that may be solved less invasively.

[mikisb]

Hi zooey,

that's easy ;)

 

i do it every day, 'cause i use a c-switch in my guitars.

A good good  guitar cable has about 80 pf/meter, a really bad up to 200 pf/meter. Standard is about 110 pf/m.

So you just have to put a capacity corresponding to yout prefered cable leghts in meters multiplied with 110pf and solder it between hot and ground of the buffers input.

 

Do you have your buffer before or after the volume and tone controls? I suppose it's after the pots because cou can run your guitar passive.

If you have ist after the pots, everything is ok now.

If you have it before the pots you still have to simulate the resistive load of the pots seen by the pickups, in your strat probably 125 KOhms, if you have 2x 250 KOhms pots. But regulary, the buffer ist after the pots so this will not be necessary.

Just in case you don't know: The capacitive load lowers the resonance frequency itself from lets say 8 to 4.5 KHz, where the resistive load lowers the peak wich is reproduced by the resonance frequency, lets say from 10 to 4 dB.

 

A lower input impedance of the helix does'nt help in this case, because with buffer, yout guitar is'nt depending on this while it it without buffer.

 

Using the tone pot to lower the resonance frequency kills the peak completly in the middle and gives you a strong peak just at the end of the range at a much to low frequency, as the capacity of the tone is way to high for this purpose. You'll need probably about 550 pF, not 10 nF or more wich would be 20 times more.

The behaviour of tone controls is'nt absolutly not a linear thing.

[zooey]

Thanks guys.

 

I'm aware of those ballpark cable capacitance numbers. However, my most common setup recently (Helix arrives tomorrow, in theory!) is a quite short (~1 meter) cable into the instrument input of a Focusrite 2i2, which you wouldn't think was enough cable to make much difference between buffered and not, but that's not what I hear. I haven't tried bypassing the buffer yet (it's currently hard wired in), but comparing my buffered main guitar with my completely passive one, the high end difference is striking, and I'm a lot happier with that aspect of the non-buffered one. Doesn't make sense to me.

 

(Both guitars have 3 humbuckers, FWIW. Secondary one is an G&L Ascari GTS HB3, main one is a bastard child built from various parts with a mix of Duncan and Dimarzio pickups and custom wiring.)

 

Michael, am I right that the "c-switch" you're talking about is a multi-position switch to change the cap used for the tone control? Did you put that together yourself? The only references I found were in German, relating to Helmuth Lemme's work, not commercial products. In any case, as I know you understood, I'm talking about a fixed cap for overall tone shaping, not the tone control, which is a whole other thing. I've used various incarnations of the Lawrence Tone-Q for years, but a) TBH, I never used the tone control that much in reality, and b) at least in part that was because the control taper really sucked, and c) the new wiring for my guitar (reason it was in the shop) uses the current Lawrence equivalent, and unless it's mis-wired, which I should check, I don't like it, will try an old one I have around, see if I like that better.

 

Bottom line I guess is that I should just experiment w different size caps and see what I like. I was asking about others' experiences in part to get a ballpark on what size caps to try. I'll also try bypassing the buffer.

[mikisb]

Hi zooey,

 

Yes, all this is in my case inspired by Lemme, who sells C-switches, but i mady mine myself.

To not to talk to much, i try it with pictures.

 

This happens to a Pickup by changing the capacitive load before the first buffer (own measurement), this is a Seymour SH 4 with C-Switch 0-1000 pF and 500 KOhm load.

you will notice that a short cable with 100 pf and a long cable with 1000 pF make a huge difference!!!!!

 

 

This happens to a Pickup with different resistive loads (sum of tone + vol + Amp)

The same SH4 with 106, 207 and 328 Ohms load at 569 pf kapacitive load.

 

So if your buffer is behind two 250 Kohm pots, you have a resistive load of 125 Kohm and a capacitive load from about zero.

 

I cannot know exactly what you're hearing and what of this you don't like. But perhaps these measurements help you to discover the reason and to find the solution ;)

To say that the SH4 does not have a strong resonance, other pickups have far more (depending on the winding, magnet, construction of the Pickup. A strong resonance can sound very characteristic but it can also also kill your ears.

So it's all about your taste and your gear you're using as with passive pickups, this often changes more than a new pickup. Unfortunally, a lot of people won't believe this - a lucky fact for Seymour, Di Marzio..... :D

After all, it's not rocket science, so a lot of Voodo is needed to make money ;)

 

 

 

 

 

 

 

 

[Joepeggio]

Hi zooey,

that's easy ;)

 

i do it every day, 'cause i use a c-switch in my guitars.

A good good guitar cable has about 80 pf/meter, a really bad up to 200 pf/meter. Standard is about 110 pf/m.

So you just have to put a capacity corresponding to yout prefered cable leghts in meters multiplied with 110pf and solder it between hot and ground of the buffers input.

 

Do you have your buffer before or after the volume and tone controls? I suppose it's after the pots because cou can run your guitar passive.

If you have ist after the pots, everything is ok now.

If you have it before the pots you still have to simulate the resistive load of the pots seen by the pickups, in your strat probably 125 KOhms, if you have 2x 250 KOhms pots. But regulary, the buffer ist after the pots so this will not be necessary.

Just in case you don't know: The capacitive load lowers the resonance frequency itself from lets say 8 to 4.5 KHz, where the resistive load lowers the peak wich is reproduced by the resonance frequency, lets say from 10 to 4 dB.

 

A lower input impedance of the helix does'nt help in this case, because with buffer, yout guitar is'nt depending on this while it it without buffer.

 

Using the tone pot to lower the resonance frequency kills the peak completly in the middle and gives you a strong peak just at the end of the range at a much to low frequency, as the capacity of the tone is way to high for this purpose. You'll need probably about 550 pF, not 10 nF or more wich would be 20 times more.

The behaviour of tone controls is'nt absolutly not a linear thing.

great Info. Good to learn. A buffer cant be loaded like a passive pup. Ahhhhhh, output impeadance too low.

[zooey]

Yes, the low output impedance of a buffer is the point of having one, for exactly that reason.

[zooey]

Hi zooey,

 

This happens to a Pickup by changing the capacitive load before the first buffer (own measurement), this is a Seymour SH 4 with C-Switch 0-1000 pF and 500 KOhm load.

[...]

you will notice that a short cable with 100 pf and a long cable with 1000 pF make a huge difference!!!!!

Understood, that's why I want a buffer, to isolate the guitar from the changing outside environment.

 

What I don't get is why the buffer seems to matter so  much with such a short cable. There may be something else going on, but I don't know what.

[mikisb]

there's nothing else going on.

But again: Where in the circuit of the guitar the buffer is positioned? Between Pickups and potentiometers or after the potentiometers?

Or are you comparing different guitars with different pickups? Each pivkup has its individual resonance frequency and "peak strength" and is influenced individually by pots and cables. This all depends on the inductivity and resistance of the pickup coils, how they are solded together and some other details as magnets, magnet position and magnetic materia (as steel) in the coil.

 

Sorry that i'm perhaps a little bit slow in understaning, but a foreign language makes things not easier to me ;)

It would be easy if you could pass by and we could measure your guitar and cable, but from Boston to Germany is not this easy.

[zooey]

I tried bypassing the buffer, and it was a little less bright, but not wildly so. My conclusion is that the big difference is between my two guitars, which is a complete non-surprise. It was different enough that I'd built a new set of Amplitube presets for it, but I thought I'd feel at home going back to my main guitar and its "old" presets. However, it appears my perspective has changed from a month of the other one.

 

That happens over time, for various reasons, just have to roll with it. All of this is kind of irrelevant anyway, since I'm off into Helix-land tomorrow if all goes well. Worth keeping this experience in mind as I go.

 

If anyone cares...

- The buffer is after the volume control, to isolate it from the cable

- I ended up using the old Tone-Q filter, and I like it a lot

[mikisb]

Hi Zooey,

 

sometimes things are just like that ;)

So if the buffer is after the  volume control, the resistive load did'nt change. So it's really just the capacity wich the pickups are missing, with your short cable about 110 pF. With this, there sould be no tonal difference from active to passive, except the bussfer is'nt linear.