importance of ac-adaptors?

Hello,

in consequence of the thread "Mods for Bad Monkey?", I monkey'ed around
with some pedals of the tubescreamer type and several ac-adaptors. I
wanted to know, how dependent these circuits are from the used
ac-adaptors. I tested ...

Ibanez TS7 (808 modded)
Digitech Bad Monkey
MEK Tubedrive TD-1
Boss Bluesdriver BD-2

... with a MIM Strat, maple neck, Fender Tex-Mex Pickups, Neck-Pickup,
blues junior tube-amp and ...

Ibanez AC-109 (regulated) 8,99 V
Boss PSA-230P (regulated) 9,08 V
Digitech PS200R (regulated) 9,39 V
Boss ACA-230G (unregulated) 14,10 V

In this order (with increasing voltage) I noticed:

* the effects became louder.
* the overdrive-character changed.
* more compression of single notes.
* the lower (bass) strings became more compressed and sound flatter.
* more total overdrive.

Also each adaptor seems to have an character of its own. The Ibanez
AC-109 has the most grit/dirt (which I like), the Boss PSA sounds clean
almost too neutral, the Boss ACA makes the biggest difference but
exaggerates all a touch too much. - For each of my "tubescreamers" I can
find one of the adaptors, that I prefer and that makes it an even
better effect-pedal! (and that without the need of internal mods).

My personal conclusions are:
Before I bash a pedal, I will test it with different ac adaptors from
now on. And I'm curious, how *lower* voltages than 9 V will sound
(someone tried that?)

Does someone know something about the "inner resistance/impedance" of
ac-adaptors and its influence?

Thanks for your patience

oz <oz@bluemonk.de> schrieb:

>My personal conclusions are:
>Before I bash a pedal, I will test it with different ac adaptors from
>now on. And I'm curious, how *lower* voltages than 9 V will sound
>(someone tried that?)

You can get some interesting "noise" with lower voltages. The Stab-Pot
on the Z.VEX Fuzz Factory for example tweaks the suply voltage for the
pedal.

Opamp based pedals would go earlyer into clipping if the voltage is to
low. They would work better with higher voltages.

Digital stuff will stop working (or do funny stuff) if the voltage is
to low or die if to hight.

greets
Jürgen
--
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On Sun, 08 Apr 2007 10:22:37 +0200
Juergen Klein <see_text@technik-klein.de> wrote:

> oz <oz@bluemonk.de> schrieb:
> 
> >My personal conclusions are:
> >Before I bash a pedal, I will test it with different ac adaptors from
> >now on. And I'm curious, how *lower* voltages than 9 V will sound
> >(someone tried that?)
> 
> You can get some interesting "noise" with lower voltages. The Stab-Pot
> on the Z.VEX Fuzz Factory for example tweaks the suply voltage for the
> pedal.
> 
> Opamp based pedals would go earlyer into clipping if the voltage is to
> low. They would work better with higher voltages.
> 
> Digital stuff will stop working (or do funny stuff) if the voltage is
> to low or die if to hight.
> 
> greets
> Jürgen

Yes, as far as I know in fuzz face kind of pedals the supplied voltage
is an integral component of the simplistic design (zink-carbon vs.
alkaline, freshness of the battery, sag and so on). I watched the demo
video on zvex.com, where the "Stab"-knob makes a big difference.

But it's also there in overdrive/tubescreamer like designs, only not so
pronounced - that's my guess and what I observed. I wonder, how many
different reviews of a pedal on harm*ny central are the the result of
using just different power supplies or batteries. :-/

This morning I experimented with an adjustable ac adaptor (3V - 12V
regulated, 500 mA, Friwo EP2) and tried some lower voltages 8V and 7V
on my TS7 and BD-2. Significant compared to 9V or higher voltages;
less overdrive, more attack, smoother and more nasal/hollow lead
sound, more articulated bass, less sustain. In suppose this all
means just less compression and *less* clipping than normal (Jürgen?).

But 7-8V can be useful, for example the TS7 has a switch for TS9- or
HOT-Mode. The least I is unusable for me normally, but with 7 or 8V it
is much less distorted and harsh an comes back in the overdrive zone.

So for me, the influence of voltage is out of question now. But one
question remains: What is the factor, that makes two ac adaptors with
(nearly) the same voltage sound different?
i.e.
Ibanez AC-109 (regulated) 8,99 V
Boss PSA-230P (regulated) 9,08 V

Is it the remaining ripple content? the impedance? - If so, it
would be interesting to design a power supply, where all these
parameters are variable. When someone uses just one pedal most of the
time, it could make sense to optimize the power that way - or to adapt
it to different types of guitars. Just a few thoughts ...

thnx.

oz <oz@bluemonk.de> schrieb:

...

>>
>> Opamp based pedals would go earlyer into clipping if the voltage is to
>> low. They would work better with higher voltages.
>>

...

>
>This morning I experimented with an adjustable ac adaptor (3V - 12V
>regulated, 500 mA, Friwo EP2) and tried some lower voltages 8V and 7V
>on my TS7 and BD-2. Significant compared to 9V or higher voltages;
>less overdrive, more attack, smoother and more nasal/hollow lead
>sound, more articulated bass, less sustain. In suppose this all
>means just less compression and *less* clipping than normal (Jürgen?).

I mean the clipping of the input-stage of an Opamp only pedal. You
could easyer overdrive the input of an opamp based pedal if it works
with low voltage. The MXR Microamp for example. A MXR Distortion plus
will work as a Microamp at low voltage because it is nothing more than
a Microamp with clipping diodes.

The TS has a transistor output stage. You change the work-point of the
output-stage-transistor and so the sound. Because the output of the op
is lower, the clipping-diodes (0,7V) didn't do theire job. If you
replace them with germanium or shotkey-diodes (0,3V) you will get more
clipping (maby near normal, depends on the voltage and input).
>
>So for me, the influence of voltage is out of question now. But one
>question remains: What is the factor, that makes two ac adaptors with
>(nearly) the same voltage sound different?
>i.e.
>Ibanez AC-109 (regulated) 8,99 V
>Boss PSA-230P (regulated) 9,08 V
>
>Is it the remaining ripple content? the impedance? - If so, it
>would be interesting to design a power supply, where all these
>parameters are variable. When someone uses just one pedal most of the
>time, it could make sense to optimize the power that way - or to adapt
>it to different types of guitars. Just a few thoughts ...

More the output resistance is the diffence between the Ibanez and Boss
PSU. You have to mesure the voltage under load! Not without load.

But I thing it's the wrong way to try to vary the sound by changing
the parameters of the PSU. You have to use different PSU for each
pedal. Better build a very good PSU (good filtering, LM317 regulator,
more than enough current) and vary the parameters in the pedal.

This could be easy done with Z-Diodes, voltage-dividers or a simple
resistor.

For example: A resistor in series could simulate a (bad) zink-carbon
battery. You only have to messure the output resistance and voltage of
a zink-carbon battery (or your favorite PSU) at the point you like the
sound of your pedal.

If the design of the pedal is done well the PSU should not have any
effect on the sound if the voltage and power fits it needs. But like
all mass-products any part with could safe a cent will removed.

So most pedals have to less filtering and voltage-buffering-caps. For
example: only some few caps in the right place of a dynacomp/ross comp
and the sound is a lot better.

--
Mailadress: klein AT technik-klein DOT de
Advertisement to this mail address is prohibited!
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> >This morning I experimented with an adjustable ac adaptor (3V - 12V
> >regulated, 500 mA, Friwo EP2) and tried some lower voltages 8V and 7V
> >on my TS7 and BD-2. Significant compared to 9V or higher voltages;
> >less overdrive, more attack, smoother and more nasal/hollow lead
> >sound, more articulated bass, less sustain. In suppose this all
> >means just less compression and *less* clipping than normal (Jürgen?).
> 
> I mean the clipping of the input-stage of an Opamp only pedal. You
> could easyer overdrive the input of an opamp based pedal if it works
> with low voltage. The MXR Microamp for example. A MXR Distortion plus
> will work as a Microamp at low voltage because it is nothing more than
> a Microamp with clipping diodes.

Aha, thanks for the clarification. Nice information also about MXR
Microamp <--> MXR Distortion plus. I have the distortion+, but never
made use of it, because I don't like it with strat, only with
humbuckers. I will look at it again. 

> The TS has a transistor output stage. You change the work-point of the
> output-stage-transistor and so the sound. Because the output of the op
> is lower, the clipping-diodes (0,7V) didn't do theire job. If you
> replace them with germanium or shotkey-diodes (0,3V) you will get more
> clipping (maby near normal, depends on the voltage and input).

That might explain the voltage dependency, thanks!

> >So for me, the influence of voltage is out of question now. But one
> >question remains: What is the factor, that makes two ac adaptors with
> >(nearly) the same voltage sound different?
> >i.e.
> >Ibanez AC-109 (regulated) 8,99 V
> >Boss PSA-230P (regulated) 9,08 V
> >
> >Is it the remaining ripple content? the impedance? - If so, it
> >would be interesting to design a power supply, where all these
> >parameters are variable. When someone uses just one pedal most of the
> >time, it could make sense to optimize the power that way - or to adapt
> >it to different types of guitars. Just a few thoughts ...
> 
> More the output resistance is the diffence between the Ibanez and Boss
> PSU. You have to mesure the voltage under load! Not without load.

Load should make no difference here (in theory), because both PSUs are
regulated, and should supply 9V even under load, as long as 200 mA
are not exceeded. But in practice nothing is impossible, so I
now measured the voltage at the power jack of my bad monkey with
both ac adaptors. The guitar and the amp were connected and I strummed
some chords to have real conditions. Both adaptors kept their voltage
absolutely constant, no drop at all. A sag is no explanation here.

But besides I think I found the reason, why using a battery and a PSU at
the *same time* on the bad monkey changes its sound: the battery
voltages can be measured across the ac jack, which means that the
battery interacts with the PSU, when both are connected. Uffz, 9,3V
battery versus 14,1V of the Boss ACA-230G! And I liked the sound of that
stupid setup ...
 
> But I thing it's the wrong way to try to vary the sound by changing
> the parameters of the PSU. You have to use different PSU for each
> pedal. Better build a very good PSU (good filtering, LM317 regulator,
> more than enough current) and vary the parameters in the pedal.

... instead of using different PSUs for each pedal, I'm thinking about
buying just one adjustable model in plural. Then I could adjust the
voltage individually for each pedal. And have a backup always. Of course
the PSU has to be well filtered, regulated and not noisy also. hmm ...
To vary parameters in the pedal is more effective, sure, but
then it will be another pedal, and that is no option for me at the
moment. I find it appealing, having to modify only external variables -
after becoming aware, how important they are with PSUs. 

> This could be easy done with Z-Diodes, voltage-dividers or a simple
> resistor.

Could be done also externally, right?

> For example: A resistor in series could simulate a (bad) zink-carbon
> battery. You only have to messure the output resistance and voltage of
> a zink-carbon battery (or your favorite PSU) at the point you like the
> sound of your pedal.

Or a 1V Zener-diode in row external could provide a drop ... 

> If the design of the pedal is done well the PSU should not have any
> effect on the sound if the voltage and power fits it needs. But like
> all mass-products any part with could safe a cent will removed.

One part, that seems to be removed in the bad monkey is capacitor on the
power input, because the LED goes off instantly when the PSU is
removed :-). This is different on the TS7 for example, where the LED
dims ( --> capacitor). Again, I suppose these impedance-factors have
some influence - but being no e-techie I have no clue.

> So most pedals have to less filtering and voltage-buffering-caps. For
> example: only some few caps in the right place of a dynacomp/ross comp
> and the sound is a lot better.

No doubt.

thnx!