Clips of my new pedal

[LyleCaldwell]

This is the preamp from a Korg SDD-3000, tweaked for guitar use, with a series/parallel loop, adjustable switchable boost, and a 9.6vdc output for powering attached stompboxes.

(the below is repasted from a forum post - a U2 forum, hence the choice of clips, and forgive some of the explanations which are obvious to you but not to the intended readers of the post.  The pedal isn't just a "U2" pedal - in front of a Marshall it sounds like a better Marshall, ranging from AC/DC to old ZZ Top - I'll have clips of that later)



http://psionicaudio.com/main/SDD%20Clips.mp3

OK, did some quick clips.  There are a few spots where the volume
fluctuates and there are some static pops - this was caused by the
boost level pot, which is hanging out of the case, and then bouncing
slightly on the floor when I tapped my foot in time.  Not worth
redoing, as there will be newer clips soon enough.

Also you can hear some background noise in the sections where the
boost is on a lot - this will be greatly reduced in the final version,
due to some upcoming cap value changes and also due to the
pedal having the bottom off in this test, so no full shield.

The signal path is Strat > Preamp pedal > PODxt Pro > Korg DL8000R in loop >
PODxt XLR outs > MOTU 1224.  Recorded in mono.  Didn't put the Korg in
the pedal's loop becase I have the loop disabled in the prototype
right now while I mode the send/return level circuits.

Anyway, the first thing you'll hear are some recognizable harmonics,
played first just with the clean AC30 sound on the PODxt Pro, then
with the preamp on with no boost but a healthy level, and then with
the boost on.

Then you'll hear a recognizable part that starts with just the preamp,
then the boost comes in.  Due to how amps react, including the POD,
you don't get a huge volume increase, as the amp can only do so much
before compressing and distorting - which is exactly what we want.  If
this were a Twin Reverb, which has a much cleaner input with more
headroom, the sound would have gotten much louder without so much
overdrive.

Then another recognizable part, including the fun of tapping a digital
delay in real time.  Again it starts with just the preamp, then the
boost comes in.

Then something badly played but the sound is quite good (IMO).

Please forgive all timing errors - I do much better with a band or
click.

[nunocaldeira]

Man, that sounds like U2... not my kind of music but it sounds really great.

Congratulations for your build.

Post again when finished .


Nuno Caldeira

[LyleCaldwell]

Thanks.  It sounds like U2 because I was using the AC30 sim in the POD and the mod delay with dotted eighths (and playing U2 style).  The group that spawned interest in this pedal is a U2 forum, so that's what the first clips reflect (already have 80 orders from that group).

But the pedal doesn't just do U2.  It works with many different amps for many different styles.  Here's a post I did yesterday, trying it out with some very non-U2 amps:

Today I took the working prototype to two stores in town to test it
with a variety of tube amps and different guitars.  The results were
interesting and have led to some very slight design changes that I'll
address below.  These will only slightly delay the pedal's production,
but will be well worth it.

I went to the first store and tried the following, using a new Clapton
sig Strat and a '59 RI Les Paul:

First, I tried it through a Bogner Shiva, using the clean(er) channel.
  This is an open-backed 1x12 with 6L6s and reverb.  I think the
speaker was a V30.  The clean(ish) channel is voiced like a Fender,
without sounding like any particular Fender (though IMO it's most like
a Super Reverb or early BF Bassman).  The results with the preamp were
very good when the gain was just above unison to about 3/4 of the gain
available without using the boost.  Over that level, or with the boost
engaged at a hot level, the highs out of the amp were kinda harsh and
too aggressive.  Still a good sound, but not smooth enough for lead
playing.  On the other hand, single note definition was great, as was
voice definition and dynamics - with the amp loud and the boost
cranked, I could play softly and still get clean sounds - but sustain
and attitude were on tap.  Only reservation are the harsh highs when
boosted a lot.

Next I tried an 18W handwired Marshall reissue, which is an
open-backed 1x12 combo using EL84s.  I believe it had a Celestion
G12H30 in it.  This amp had no true clean - with the volume on 2 it
was loud and in your face.  Turning on the preamp just above unity
sounded like classic AC/DC.  Turning on the boost turned it into
classic ZZ Top.  No harsh high end when boosted with this EL84 based amp.

Next I tried a Savage Rohr 15, which is a 15W 1x15 combo using EL84s.
  I don't know what speaker was in it, but it sounded very good.  Not
quite an AC30 on normal channel, not quite an AC15.  I'd be interested
in hearing this amp with the 2x10 or 1x12 option.  The preamp
instantly turned this into a variation of the classic Edge sound,
though a little darker with more low end (I think the 15" speaker
caused this).  The boost had that "Sort of Homecoming/Wild Horses"
feel, where instead of distorting like a hard rock/metal sound, the
harmonics just rushed together and the sustain went on for days.  This
was very, very pleasing to me.  No harsh highs when boosted - again,
this is with EL84s (and a 15" speaker).

I then went to another friend's store and tried a Carr Rambler (a very
unique and wonderful Class A amp using 6L6s and no feedback loop -
right in between a Vox and a really great blackfaced Fender).  Here I
also tried a Line 6 Echo Park (worked flawlessly with the preamp's
9.6vdc power supply and sounded fantastic in the loop). The guitars
used were an Anderson Tele-style and a PRS CE-22 with an all-mahogany
body.  I used the Carr in Pentode-power mode, for those playing the
home game.  I don't remember if the Carr I used was the 1x12 or the 2x12.

Through the Carr, it had the same great qualities as the Savage, but
was more articulate and cleaned up even better when played quietly.
The attack was faster when I really hit it hard.  This was a sound I
loved very much.  Both guitars sounded unique with the preamp and the
Carr, even when the boost was on full - they retained all the
characteristics that make someone buy an Anderson or PRS in the first
place. No mush or generic OD sound.  That said, when the boost was
really cranked, the slight harshness was there like it was with the
Bogner (which also used 6L6s).

In addition to the harsh high end with the 6L6s based amps, the gain
available from the preamp alone (no Boost engaged) was enough to clip
the input of the Boss DD3 I brought along for these tests. BTW, the
Line6 Echo Park did not clip at those same levels.

So, realizing that I need to address the harsh highs with some amps
(only when the boost is cranked - we're talking over 20dB of available
gain here), and that I need to prevent digital clipping with a delay
in the loop, I'm making the following changes to the design:

The serial-only Dry Level knob is going away.  It wasn't needed
anyway, as I had thought.

I'm adding a Send Level knob in place of the current Loop Level (which
attenuated the loop return, not the send).  The Send Level will
attenuate the signal sent through the loop, so the preamp can slam an
amp input without slamming the input of a digital delay (or other
digital effect).

I'm adding a Return Level knob, where the center position is unity
(same as the dry).  If you want to turn the delay/loop level down in
relation to the dry sound when in parallel mode, this is where it's
done.  Or if you turn down the Send Level to avoid clipping, this knob
can be turned up to keep the delay level as hot as needed (even over
unison if you want).

That will take care of the delay/loop level and digital clipping.  Now
for the sometimes harsh boost:

I'm putting in a tone control knob.  The tone control will be out of
the circuit when on 10.  It will function like a standard guitar tone
control, though the behind the scenes circuit is quite different.  The
tone control will only affect Boost mode. I will have to play around
with the right frequency to roll off at, but I think around 5K-7K
should be about right.

This will bring the total knob count to five.  Updated mockup images
to come, as will clips of the pedal as it exists today (tonight).

First I have to experiment with some very tiny (5pF to 10pF) caps in
parallel with the boost gain pot, to eliminate some very high
frequency hiss.  I don't expect the hiss to be present or at worst
very audible in the final version - this is what prototypes are for,
right?

[nunocaldeira]

80 orders! wow...

Do you build for a living?

[LyleCaldwell]

Nope.  I'm a computer consultant.  But I may be taking a side job as a pedal maker.  Total accident, I swear.  I just got tired of saying "I wish someone would make this" so I decided to make it.

[nunocaldeira]

80 orders seems a good starting point. I wish someone would like me to build a pedal (I built one for a friend). And I would like to sell some. Not for business, but to pay the hobbie. I like building pedals but it is not cheap. Last month I spent 150 euros in Banzai's stuff. Not talking about the components I get from a local store, or the paint, or the Tools (I bought *everything* this year).

Good luck,

Nuno Caldeira

[koolimy]

Wow, I think it sounds really good!
Good luck with selling them...

[LyleCaldwell]

I've made and sold about 8 custom rack interfaces (with 5 more and two custom power supplies in the works right now), 13 modern versions of the Guyatone Zoom, and have 80 pre-orders from word of mouth in just one internet forum for this preamp.

I haven't made a single Rat or SD9 clone.  In order to sell, you have to make something someone else doesn't make, or you have to make it extremely and obviously better.  I have no desire (or ability) to go up against Keeley, Fuller, or RG/Mark Hammer/etc.  Any one of those guys could have made this preamp.  But they didn't.  I've also invested a lot, and if the first 20 people say "it sucks" then I am not only out of business but will have to buy them back and eat about $4000.  So A) it's a risk and B) I am doing everything I can to make sure all 20 love it. 

No suckage allowed.

I have made two of RG's excellent Neovibes.  One for myself and another for a friend, and I only charged him for the parts.  That's RG's design and I won't try to profit from it.

If I could have purchased this pre, or the rack interface/mixer I needed, I wouldn't be making them. 

[LyleCaldwell]

Wow, I think it sounds really good!
Good luck with selling them...

Thanks!  I should have clips of the second prototype through real amps in about 2 weeks.  Will sound even better.

[nunocaldeira]

I've made and sold about 8 custom rack interfaces (with 5 more and two custom power supplies in the works right now), 13 modern versions of the Guyatone Zoom, and have 80 pre-orders from word of mouth in just one internet forum for this preamp.

I haven't made a single Rat or SD9 clone.  In order to sell, you have to make something someone else doesn't make, or you have to make it extremely and obviously better.  I have no desire (or ability) to go up against Keeley, Fuller, or RG/Mark Hammer/etc.  Any one of those guys could have made this preamp.  But they didn't.  I've also invested a lot, and if the first 20 people say "it sucks" then I am not only out of business but will have to buy them back and eat about $4000.  So A) it's a risk and B) I am doing everything I can to make sure all 20 love it. 

No suckage allowed.

I have made two of RG's excellent Neovibes.  One for myself and another for a friend, and I only charged him for the parts.  That's RG's design and I won't try to profit from it.

If I could have purchased this pre, or the rack interface/mixer I needed, I wouldn't be making them. 

Makes sense.  I didn´t charge my friend for the JFet Vulcan I built for him. But I would do it with Tub3 Scr34m3r clones and other stuff like that.
Sorry I'm getting a lot Off-Topic.

[TryingToDo613]

Can you tell us how you got the schematic and how you are doing the digital chip thing, and how you got the chip of course. It is a digital delay of course. -ph

[LyleCaldwell]

I got the schematic by tracing out  and measuring just the preamp of an SDD-3000, then adding the series/parallel loop, the boost, a tone control, and various level controls of my own.

I'm only using the analog preamp from the SDD.  This allows you to use the preamp with any modern delay, so you can get the sound of the SDD but with modern features like tap tempo, MIDI control, presets, multi-taps, etc.  Or you can stick a delay pedal in the loop and get close to the sound of the $900 Korg, but also have delay trails and parallel delays like a rack system can offer.

The digital delay in the SDD-3000 isn't that remarkable.  It's the preamp and its affect on the delays that are so valuable.  The delay in that clip came from a Korg DL8000R, and I get the same results with a 2290 and an Eventide Eclipse.  I got results almost as nice with a Line6 Echo Park, and I got usable results with a cheap Boss DD3 (with delay trails!).

[TryingToDo613]

I'm whoozy. I think this is over my head. Since you used that eventide word I suspect you are in the space of advanced studio gear. I did just score a Korg SDD-3300 Programmable Triple Digital Delay on ebay after reading your posts to see if it's cool. Could you tell us what the pedal actually does and what part of it made that U2 sound, not that I'm a U2 fan really. -ph

[LyleCaldwell]

Whoa, you should know that there is a world of difference between an SDD-3000 and an SDD-3300, which is not that great a delay unit.

The pedal has a preamp stage with adjustable gain, capable of attentuation to unity to modest gain increases up to full overdrive.  After this stage there is a loop which can be configured as series or parallel, and the loop is footswitchable.  After the loop return (and both the send and return have level controls) there is an additional boost stage, which is adjustable with its own tone control, and this boost is also foot switchable.

So when used with a single channel amp it effectively gives three channels, or just variations on whatever sound you want to use it on.  Lots of applications.  It's not a "U2 pedal" but it is based on the preamp in the SDD-3000 which is a large part of the classic U2 sound (also used by Daniel Lanois). 

But forget about the SDD-3000.  Think of it as a clean boost to OD with a switchable loop followed by another stage of boost.  It's great on Marshalls as well - clips of that will be coming soon with the second prototype.

[TryingToDo613]

That makes sense, thanks. Now I understand the novelty of it. It's like having two boost pedals and putting whatever you want between them, to dumb it down a bit. That unit specifically is known for having a nicely usable preamp so you copied it, instead of using an amz or other boost that is known to us. Thanks. -ph