Treble loss

[hywelg]

I had a problem with a pedal board cable and in order to isolate which, I set up an A/B switch so that my guitar signal either went straight to the amp or through the board. All my pedals are true bypass. I did manage to find the problem cable but I also found that some cable types led to a loss of treble (Van Damme in particular was poor, Klotz La Grange is good, Planet Waves was OK suprisingly, George L's was the best, though I now have two more high end cables on order to try them).

I also found by trial and error that the two factor pedals on my board are a source of treble loss. Not massive but significant. Yes I have Byp Typ set to Relay. and they are both in front of the amp input with levels switches set to Guitar. I was suprised, but I guess theres very little I can do about it other than use some sort of loop switcher, which I'd rather avoid as my board is full already.

If anyone has any ideas how to resolve this I'd appreciate it, though I have to admit I'm not hopeful.

[Imerkat]

well, first thing, you still need a buffer on your board. it might still be the fact that they are at the end of the chain, rather than the actual pedals themselves, were the tone is being lost.

If you do have a one your tone is only as good as your first buffer.

If you don't you might wanna turn on the DSP Bypass of one the Factor pedals.

i skipped the trouble and got the Redeemer Circuit from Creation Labs.

[hywelg]

No I don't need a buffer thank you. The treble loss is present when the factor pedals are the ONLY thing in the chain, and on a very short chain at that. It is the pedals that are doing it I'm afraid, not the length of the signal chain.

[wedelich]

Hi hylwelg,

Imerkat is right.  A buffer or DSP bypass is the way to solve the problem.  While cable length can influence the problem, the real culprit is impedance mismatching.  Passive guitars have low output, but higher output impedance.  You need an amp or pedal input with even higher input impedance to make sure that the majority of the signal is "sunk" at the destination and not the source.  Active guitars solve this b/c most onboard pre-amps have very low output impedance, but I don't necessarily like them (other than basses).

The whole "true bypass" thing, in my opinion, is misleading.  It would seem to imply that the most "pure" version of your signal is making its way to the amp, but this is not the case for instruments with passive electronics.  In reality, running a small, high output impedance signal through a bunch of "hard connected" boxes just creates an ill-conditioned signal path for passive instruments.  In your case, without a buffer, the signal is being loaded down at the source (in a frequency dependent lowpass way), the guitar.  The buffered solution actually preserves the signal better as it "opens up" the path for the signal, so to speak. 

Russ

[hywelg]

wedelich:

While cable length can influence the problem, the real culprit is impedance mismatching.

I don't get it. I can run my guitar through 7 pedals and 6-8m of cable and get virtually no loss (when bypassed) of treble, but when I run my guitar through 2 factors, both relay bypassed and a really short cable (same type as previously, George L's) I suffer loss of treble. If I use the same cables and no factors I get no treble loss so its not the cables.

I do understand how impedance mismatching can influence how the cable capacitance leads to treble loss, but how is the impedance being affected when the factors are bypassed? through the relay?.

Let me spell it out again. I ran a switched loop, to both my factors in series with very short George L patch cables. I can switch the loop in and out so I am A/B'ing the tone. I deliberately hide the LED on the loop box so I'm not influencing what I'm hearing. I can tell when the bypassed factors are in circuit., its audible.  Now if I replace the factors and patch cables in the loop with a 5m George L's cable, considerably longer than those patch cables, I cannot tell which is which when A/B'ing. So if the cables are not creating the conditions of which you speak, the Factors are, but how?

[DGillespie]

Hi Hywelg,

So there's a couple different types of impedance in the circuit.  There's the source impedance, which as we were saying is very high, there's the cable impedance which is essentially a capacitor which shunts the cable to ground, and there's the termination impedance which can vary depending on the amp.  The way circuit gets set up creates a low pass filter, the frequency of which is determined by the combination of the source impedance, the total cable capacitance, and the termination impedance.  The cable capacitance is cumulative and some cables have more than others, so as you noticed short runs of some cable can have more of an effect that long runs of another.  On top of all that, you can get accumulated capacitance from where the cable connects to the plug, where the plug connects to the jack, and so on, until the termination.  Often times these things don't make a big deal, but if you have a guitar with a particularly high source impedance and an amp with a particularly high termination impedance a very small capacitance can be noticeable.

So to track down the source of the filtering in your system here's a couple things worth trying.  Try turning your guitar output up or down, this will change the source impedance, and even when corrected for in the amp volume will change the over system treble.  Try swapping out some cables, even the small interconnects between the pedals may have more capacitance than you think if there's a bad connection.  Try putting the Factor pedals in DSP bypass mode, this will change both the termination impedance of the circuit (the Factors have a 1 Megaohm input impedance) and the in circuit capacitance, this can help you determine if the problem may be with a pedal, and if so which one in particular.  Finally, it's possible that one of the pedals may have a bad connection, or a bum relay, but that's the hardest thing to test and fix so it's probably best to rule out all the other stuff first.

Does this explanation help?

[hywelg]

I accept completely what you are saying. I understand the mechanisms that are at work here however the tests I have done lead me to believe the internal capacitance within the factors are what is causing the , admitedly small, treble loss.

Using a George L's cable from my loop box to first the PF, then another to the TF and then back to the loop box with another. Thats six Georgle L's connectors and approx 2foot of cable. I can detect a very small loss of high treble, sparkle if you will, when the loop is switched in and out and both pedals bypassed.  Switching the PF to dsp bypass I get slightly more treble loss and a drop in volume.

Now the remainder of my board consists of 7 pedals.

Turbo Tuner St-200, 7" George L cable to:-
Menatone Blue Collar, 2" George L cable to:-
Menatone TBIAC, 2½" George L cable to:-
XOtic BB, solid connector to
Xotic RC, 2" George L cable to:-
MXR EVH Phase 90, solid connector to
Rothwell Love Squeeze

When these are connected to the loop with two additional George L 7" cables (at the start and the end) I can detect no treble loss whatever. A 5m George L cable  in the loop alone produces no loss. Neither does the recently acquired 5m Providence S102, though the Lava Soar cable does lose an insignificant amount.

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