Why won't my EBS & Frantone get along?

[scotch]

I have a strange phenomenon going on with a pair of my pedals.

I use an EBS Valve Drive as the primary tone shaper in my setup. I really cannot live without it! It's sort of become "my sound"...

Anyway, I have a Frantone Thunderhead (low freq. booster) that I've used in the past for "special effect" purposes. When I want an extra deep, thunderous bomb - I can flick on the Thunderhead & blow out some PA subs!!! I've run into a problem, however. When the Frantone is after the Valve Drive in my chain, the Frantone sort of "bogs down". The volume drops about 50% and the tone gets totally washed out... Frantone before the EBS works fine, but I don't like that setup as it creates gain staging problems on down the chain. None of my other dozen or so pedals acts strangely with the Frantone, just the Valve Drive (and the Valve Drive works great with everything else as well).

What gives? I guess there is some sort of impedance mismatch going on, but why can't I recreate it with any other pedals? Weird...

Anyone else have an odd set of pedals that refuse to work together?

[bongomania]

Sure, I've run into many combinations of pedals that didn't like each other. Aside from impedance mismatch, one wild speculation is that perhaps the Thunderhead creates its boost by parallel doubling some part of the signal and then flipping the phase of one side, which would wreak all kinds of havoc on a harmonics-based effect like the ValveDrive. Again though, that's just a total shot in the dark as an example of something that could cause that sort of problem.

I would ask Frantone and EBS for the in/output impedances of those specific pedals.

[scotch]

Originally Posted by bongomania

Sure, I've run into many combinations of pedals that didn't like each other. Aside from impedance mismatch, one wild speculation is that perhaps the Thunderhead creates its boost by parallel doubling some part of the signal and then flipping the phase of one side, which would wreak all kinds of havoc on a harmonics-based effect like the ValveDrive. Again though, that's just a total shot in the dark as an example of something that could cause that sort of problem.

I would ask Frantone and EBS for the in/output impedance's of those specific pedals.

Hmmm... Surprisingly, this is the first time I've come across this type of problem.

It would make sense to me that the Thunderhead is doing what you say- it essentially is 2 boosters in parallel: A clean boost independent of the low freq bass boost. Maybe the Frantone just can't take the awesomeness of the Valve Drive?

Valve Drive output impedance is >500k ohms; input is 1 megohm

I've emailed Frantone regarding the Thunderheads specs...

[niftydog]

Originally Posted by scotch

The volume drops about 50% and the tone gets totally washed out...

Classic phase issue.

Originally Posted by scotch

Valve Drive output impedance is >500k ohms; input is 1 megohm

That output impedance figure is extremely high - even 500 ohms is high, let along 500,000 ohms! Sure that's right?

[bongomania]

Same thought here. Even if the z out is really >500 ohms, that demands a very high z in on the Thunderhead for there not to be tone loss.

[scotch]

Originally Posted by niftydog

Classic phase issue.


That output impedance figure is extremely high - even 500 ohms is high, let along 500,000 ohms! Sure that's right?

That's the published spec. There is a surprising quantity of typo's in EBS manuals, though... The "Nominal output level" is -10db (I don't think that applies to this, though).

Phase cancellation is exactly what it sounds like, now that you mention it. Is there any way to remedy this? (eg, reversing the Thunderhead's phase?)

[scotch]

Originally Posted by bongomania

Same thought here. Even if the z out is really >500 ohms, that demands a very high z in on the Thunderhead for there not to be tone loss.

The thing is, all of my other pedals/etc. sound great after the Valve Drive. I'm even using it as my studio recording pre (into a GT Brick).

[bongomania]

A -10dbu output is enough to feed a consumer-grade recording device, or overdrive the input stage on a typical amp, or bypass the preamp into the fx return on a lower-budget amp head. Might be enough to drive a power amp with a low input sensitivity rating. All that's a long way of saying the level is not too low for the Thunderhead input, in fact it can go to a higher level than the Thunderhead expects; and often increasing the signal level is a way to "power through" an impedance mismatch.

So while the impedance is still an issue to research, phase is more likely as a culprit.

In a series connection, if the Thunderhead merely switched your signal's phase, you would not hear that change. So (again in series) the only way the Thunderhead can cause that sort of phase problem is if it actually splits the signal into a parallel path. If it does that, then wholesale flipping the phase of the output would not help.

That's another good question to ask Frantone- so as to not sound like a cloner, you might tell them about the specific issue you're having; that way they will be inclined to tell you exactly what's going on in there, and whether anything can be done.

[bongomania]

Originally Posted by scotch

The thing is, all of my other pedals/etc. sound great after the Valve Drive. I'm even using it as my studio recording pre (into a GT Brick).

Every device is designed with a different z in. It may well be that your other pedals have very high z ins, which is what you need. The Brick certainly does have a very high z in (IIRC).

[scotch]

Many thanks, Bongo - you're a champ!

[scotch]

Well, Frantone was great about responding, but I don't think that I'm going to be able to make these pedals work together!

No answer on the impedance measurements, but here is the exchange w/ Frantone:

"If you give me the serial number of your Thunderhead from the inside of
the baseplate I can look up what version of that pedal you have, but I
will say that the Thunderhead was not designed to be placed after an
overdrive. The deep tone curve of the Thunderhead is such that when
engaged the presence or apparent loudness will not seem as loud as your
overdrive pedal, so of course I would recommend putting the Thunderhead
first if you need the high end boost of your Valve Drive as well. Also
because the Thunderhead is not a bright pedal (it was designed primarily
for bass guitar) by contrast if you put it after the overdrive it would
seem dull by comparison.

Best regards,

Fran"

And:

"Your Thunderhead is one of the first made, back in September of 2002. I
no longer make the Thunderhead so yours is a collector's item. As to
the phase issue, any active filter causes phase rotation, but you can
only have phase cancellation if two parallel lines of audio that get
processed independently converge at some point and then you will notice
phase cancellation if it exists, but this would only happen in your case
if you were running two separate lines.

Best regards,

Fran"

So, it looks like I'll be putting the Thunderhead up for sale(reluctantly)... The Valve Drive is such an important pedal in my setup, I guess I'll get something different in the future for my "low-end-bomb" effect. Maybe a Hogs-Foot or a straight-forward eq pedal (like an Xotic Tri-Logic ).