sorry Dano-fab fans...

[m_charles]

Hi.

I was searching for some info on re-housing a pedal (not a Dano), and came across  a post about dano-fabs, are they good, bad, etc...?

The main chunk of the discussion got into bypass buffers, cheap vs. expensive. non vs. true bypass etc.
Some were saying the dano's bypass was just as good as any.

First, I'm not a true-bypass die hard, everything has to be metal-film or it sucks kind of guy, but I thought I had noticed something with a dano I had but was in the middle of something so I didn't check.

So today after reading this post, I did a simple test. I grabbed my 2 loop true bypass box. A couple of boss, a couple Ibanez, and an Arion pedal and the dano. I put the Dano in a loop, and one by one put the others in loop# 2. I kept them all in bypass, powered from a vd labs ppower.

the results? Every single pedal/brand had a totally acceptable bypass buffer (even the Arion), except the dan-echo. This is not some nit-picking thing either. All the others sounded more or less the same, but when compared to the Dano, or the dry signal, it was like night and day. What was weird was that the Dano didn't really sound bad, there was no high-end roll-off etc. It was almost too shimmery. Like a mild clean-boost. Maybe even a slight low-cut. any thoughts guys?

But the bottom line: it drastically altered the bypass tone, enough to where I don't want it on my board. I did the test. And again, I have and use many non-true bypass pedals, and I love a good cheap pedal as well.

BTW, I did also test it all with both sides of the looper to be consistant...

chuck

[Meanderthal]

 Hmmm... this was the FAB echo? I don't have that one, just all 3 dirt boxes. Didn't notice any tone-sucking, but I think they all share the same switching/buffer pcb...

Could be true though... 

[m_charles]

It's not really a "tone sucking". I was rating my "test" simply by how well each could approximate a "dry" signal.

It was almost as if all the other pedals got the bypass sound OK, but the dano overcompensated and had too much highs, and shimmer. Like I said above. It wasn't a horrible sound, it just didn't sound anything like the dry sound (or the other's bypass sound).

[Meanderthal]

 OOOOHHHH! Doh! Ya did say that, didn't ya?

Sounds like the input and/or output caps are too small a value... shame they're microscopic, because otherwise it would be an easy fix. 1uf on both ends would do the trick.(provided there's no other small value caps in the audio path of the buffers)

[z1]

thanks for pointing this out! i was thinking about trying some dano pedals but since my very bad bypass experiences with behringer i was sceptic about the bypass on these cheaper pedals...now i know i wont have to try them...

[bioroids]

It was almost as if all the other pedals got the bypass sound OK, but the dano overcompensated and had too much highs, and shimmer. Like I said above. It wasn't a horrible sound, it just didn't sound anything like the dry sound (or the other's bypass sound).

It sounds like the input impedance may be too high. Yes, that can happen, and you get a brigther dry signal in those cases.

BTW for a real cientific test you should have to do a double blind test. I.E. not knowing which pedal was on the chain.

Luck!

Miguel

[Mark Hammer]

Consider....

One of the traditional techniques for managing noise in inherently noisy systems like tape is to use a "double-ended" solution.  Something happens to the otherwise impeccable input signal before it hits the source of noise, and then something else happens after the source of noise which attempts to counterbalance the extreme measures undertaken going in.  Dolby and dbx are both examples of that strategy, as is generic companding.

One of the other tried and true techniques is pre-emphasis/de-emphasis, whereby the treble content of the input signal is boosted before hitting the point where it gets noisy.  When the signal emerges from the source of noise, it is then treble-cut in a complementary manner.  The tonal balance is presumably restored and whatever hiss was accumulated along the way is pleasingly attenuated.

Okay, hold that thought for a moment.

In a great many effects where the effect depends on combining two "copies" of a signal - one altered and one unaltered - what gets called "bypass" is often a single FET that either provides a low-resistance path to the node where the two copies are combined, or else turns into a very high-resistance path such that only one of the copies (the clean unaltered one) makes it to that node.  This is generally true of any delay, chorus, flanger, or phaser that uses solid-state switching.

The node where they are mixed also incorporates the de-emphasis circuit to restore the treble-to-bass balance.  Because that de-emphasis is applied to both the clean and effect signal simultaneously, that automatically implies that the clean signal must pass through the treble-boost pre-emphasis as well, such that the de-emphasis will simply set things right and not produce a dull sound.

Now, before making too sweeping a generalization, I should note that this scenario is NOT compulsory.  It is possible to arrange the circuit such that only the processed copy of the signal undergoes the pre-emphasis/de-emphasis...but it takes more parts and increases cost so companies tend not to do it.  A company like Danelectro which aims to undercut the competition most certainly won't do it.

So, what about those pre-emphasis/de-emphasis components?  Are they precise?  Nah.  I've never seen an instance where anything other than normal 5% resistors and normal tolerance caps were used to produce that tonal shaping.  Given those tolerances, is it possible that the pre-emphasis boost applied to the clean signal (the one you hear in "bypass" mode) is not fully counter-acted by the de-emphasis network?  You betcha.  And I think that's what may be going on.

Here's an illustration, using the venerable Boss DM-2 delay: http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossDM2.jpg
In the upper left hand corner, you will see C3/R6.  Those two components provide greater boost above 2.3khz.  Just below where it says REPEAT RATE, you'll see R36/C29.  That's the de-emphasis network.  You will note that the treble-boosted outpuit of IC1 (pin 7) goes to R32 and to the mixing node at pin 2 of IC1, where the de-emphasis network is applied immediately after the pre-emphasis in the previous op-amp.

If my theory is correct, AND you could identify the relevant components on your board, you would find the functional equivalent of C29 and maybe add a bit of capacitance to it.  That would restore the tonal balance to the clean signal.  You could always try to decrease the pre-emphasis, but working on the de-emphasis earns you greater noise reduction for the processed signal, so it's the better of the two choices.

Kudos to you for having an open mind about bypass switching, and for using a loop selector.  I'll note in passing that being able to detect such differences in clean-bypass tone is made much more possible BY using a loop selector, so that's one more vote in favour of using them.

In the Dave Hunter effects book published just a couple years ago, there is a soundclip CD.  The book itself was disappointing in many ways, but the soundclip CD is excellent.  One of the sets of soundclips is, oddly enough, buffered and unbuffered bypasses, and there ARE audible differences between different manufacturers' buffers in addition to buffered vs unbuffered.  The thing to keep in mind, though, is that the scenario I described above does NOT apply to single-path either/or effects like compressors, boosters, distortions, filters, tremolos, etc., the same way it applies to one-or-both-paths effects like echo, phasers, flangers, etc.

Does what I'm saying seem plausible, and does it make sense?

(Incidentally, I see in a little item in Vintage Guitar this month that the Arion Chorus is now being produced with a 3PDT stompswitch rather than solid-state switching.)

[doug deeper]

the bypass on my dano back talk reverse delay has some major high end roll off,
makes my fender deluxe sound great!

[Mark Hammer]

So maybe the cap tolerances are working in your favour?

[m_charles]

Thanks guys, glad the test helped.

I think the lesson here is simply use a bypass loop if the bypass on your effect if not good, and to be aware that on some "cheap" pedals, the bypass buffer can often be a place where you hear that cheapness...

chuck