Fender Deluxe Reverb - too clean!
David P. Mottaz
WAY clean. Even turned up all the way. Twangy clean. Both channels.
I would like that old Fender overdriven tone. What's my best bet here?
I do not want to start replacing parts etc. That can get carried away
to the point where I am saying "maybe if I just replace the transformer..."
Can the reverb in/out be used for this? Like just connect the reverb out/
in to each other and use the reverb control for gain? It's all tube driven,
maybe that would work.
How about replacing the 12at7 tubes with 12ax7 tubes? I understand them to
be higher-gain direct replacements. Any help/suggestions? Thanks a ton.
--
-Dave
NATHAN PHILLIP STEWART
>I have an old all tube black-face Fender Deluxe Reverb amp and it is
>WAY clean. Even turned up all the way. Twangy clean. Both channels.
>
>I would like that old Fender overdriven tone. What's my best bet here?
>I do not want to start replacing parts etc. That can get carried away
>to the point where I am saying "maybe if I just replace the transformer..."
>
guess you've got several. If you've got 12AT7's in gain stages, you are
loosing quite a bit of gain. Try 12AX7's. (Dan Torres's newsletter mentions
a new Sovtek 12AX7 that's a higher gain tube - from what I saw it's not
just a 7025, or maybe it's made to real 7025 specs instead of called the
best of your 12AX7's 7025s.) Also, David Hicks's company has a Fender
Mender which plugs into two tube sockets, and I'm sketchy here, but it
uses the reverb channel for a gain boost I believe. I called up Hick's
Electronics yesterday for lit. on the Speaker Tweaker, and his answering
machine has a demo of an otherwise stock Blackface Deluxe and a Strat
that really sings. It's got a lot more gain than I expected (and more than
I normally would care to use, but just don't turn it up as far).
Nate
STEVE SCHULTZ
>--
>-Dave
Dear Dave,
Too bad it's too clean.... :-)
There is nothing you can do about it. I repeat, nothing you can do about.
Well, there is one thing,....you can send it to me and and let me worry
about it. (For those of you with only radio, my tongue is planted firmly in
my cheek.)
Seriously, use an external overdrive box (take your pick) and leave the amp
alone. I had my '65 Super Reverb wired so that channel 1 preamp overdrove
channel 2 and regretted it. My best guitar buddy is looking to have the mod
he commissioned on his '65 Vibrolux Reverb reversed and have the amp
returned to its original state.
There was a device called the ICE CUBE that plugged into the reverb to give
some gain boost, but I don't know if that was ever reliable.
I'm sure others will disagree with me on this. If you really want to add a
gain stage somewhere, take it to a really reliable shop with a good
reputation for performing these types of modifications.
Otherwise, enjoy the clean sound it makes.
Good luck,
Steve Schultz (steve....@stpaul.ncr.com) NCR Network Products Div.
**** Coming Soon! Comments & Opinion Disclaimer Grand Re-Opening! ****
John Hernandez
|> In article <22hdcb$3...@uc.msc.edu> d...@msc.edu (David P. Mottaz) writes:
|>
|> >I have an old all tube black-face Fender Deluxe Reverb amp and it is
|> >WAY clean. Even turned up all the way. Twangy clean. Both channels.
|>
|> >I would like that old Fender overdriven tone. What's my best bet here?
|> >I do not want to start replacing parts etc. That can get carried away
|> >to the point where I am saying "maybe if I just replace the transformer..."
|>
|> >Can the reverb in/out be used for this? Like just connect the reverb out/
|> >in to each other and use the reverb control for gain? It's all tube driven,
|> >maybe that would work.
|>
|> >How about replacing the 12at7 tubes with 12ax7 tubes? I understand them to
|> >be higher-gain direct replacements. Any help/suggestions? Thanks a ton.
|>
|> >--
|> >-Dave
|>
|> Dear Dave,
|>
|> Too bad it's too clean.... :-)
|>
|> There is nothing you can do about it. I repeat, nothing you can do about.
Naw, the Deluxe tube layout goes something like this:
5AU4 6v6 6v6 12at7 12ax7 12ax7 12at7 12ax7 12ax7
^ ^
| |
Just pop in
12ax7's there!
I performed this harmless little swap on my silverfaced model. I was quite impressed with the pleasant grit I could obtain at a volume setting of 4 or 5. Throw in a tube screamer type pedal if you like even higher gain at lower volumes. By the way, hold on to the 12at7's. If you ever decide to sell it to someone (like me :)), let them know that you did this.
|> Well, there is one thing,....you can send it to me and and let me worry
|> about it. (For those of you with only radio, my tongue is planted firmly in
|> my cheek.)
|>
|> Seriously, use an external overdrive box (take your pick) and leave the amp
|> alone. I had my '65 Super Reverb wired so that channel 1 preamp overdrove
|> channel 2 and regretted it. My best guitar buddy is looking to have the mod
|> he commissioned on his '65 Vibrolux Reverb reversed and have the amp
|> returned to its original state.
Here I agree...don't mess with the wiring unless you can restore it accurately yourself!
|>
|> There was a device called the ICE CUBE that plugged into the reverb to give
|> some gain boost, but I don't know if that was ever reliable.
|>
|> I'm sure others will disagree with me on this. If you really want to add a
|> gain stage somewhere, take it to a really reliable shop with a good
|> reputation for performing these types of modifications.
|>
|> Otherwise, enjoy the clean sound it makes...
Give it a try,
John
NATHAN PHILLIP STEWART
> Naw, the Deluxe tube layout goes something like this:
>
> 5AU4 6v6 6v6 12at7 12ax7 12ax7 12at7 12ax7 12ax7
> ^ ^
> | |
> Just pop in
> 12ax7's there!
>
> I performed this harmless little swap on my silverfaced model. I was quite impressed with the pleasant grit I could obtain at a volume setting of 4 or 5. Throw in a tube screamer type pedal if you like even higher gain at lower volumes. By the way, hold on to the 12at7's. If you ever decide to sell it to someone (like me :)), let them know that you did this.
While we're on the subject of tube swapping - DO NOT put one of the solid state
rectifiers that plugs into a 5U4 socket. Most 6V6 Fenders are already way over
spec for maximum plate voltage for the 6V6's.
> Here I agree...don't mess with the wiring unless you can restore it accurately yourself!
Do you know what year this Deluxe is? Something that occured to me after my
first reply was maybe this is a CBS with a Blackface on it. I've heard that some
of the transitionals still had black faces. If it's mid-late 65 or maybe even
early 66, this could be the culprit. Have someone take a look at it. If it is,
it shouldn't be too much trouble to convert it. The absolutely clean on 10 made
me think of this possibility. My Bassman is a 72, and even when it was bone
stock, my Zion (old Strat copy - mine's slightly overwound), would still elicit
a fair bit of growl, starting around 6. At 10 it had quite a nice ferocious edge.
I've heard the "Clean on 10" period at Fender lasted only a very short while.
_______________________________________
| | Nathan Stewart
| Marshall | npst...@eos.ncsu.edu
| ________________________ |
| |!!o Q Q Q Q Q Q :: | |
|=======================================| Clockwise is Rockwise!
STEVE SCHULTZ
>|> Dear Dave,
>|>
>|> Too bad it's too clean.... :-)
>|>
>|> There is nothing you can do about it. I repeat, nothing you can do about.
My apologies regarding the previous line...I was trying to be funny. I did
not mean to convey that there was really nothing that could be done.
However, as many people have noted in this electronic medium, it is very
difficult to phrase the audio nuances of humor.
Sounds like Dave got some good advice tube-wise from others more
knowledgeable. It also occurred to me that Dave should check out the
speaker...what is in the Deluxe? Is it the stock Fender blue-label speaker?
If I'm not mistaken, the speakers also had a lot to do with achieving the
crunch/warmth around-the-edge sound you are searching for. It's a lot
tougher to get that warmth with a speaker designed to take a lot of power,
like say, an EV 12" with the black-hole heavy magnet on it.
Anyway, I stand by my statement about going to a reputable/qualified shop if
you are looking for a "hot rod mod" of an old amp.
An additional comment: For about a year I used one of the new breed of
Fender tube amps, a Fender Super 60, single 12", single input with with
clean and overdrive channels. It looked OK on paper and sufficed as a clean
practice amp until a resistor went, and it lost all preamp power on the
clean side (it had a 3-year warranty, best part of the deal). That amp
just lacked character... It was really tough to get a good warm sound just
with the amp.
Is it my imagination or a myth that "they don't make them like they used to"?
I've seen some of the prices for the THD, Fender Custom Shop Amps, etc. Wow!
Anyway....Dave, I hope you find what you're looking for....
Peter Jackson,CH237A,,
> I have an old all tube black-face Fender Deluxe Reverb amp and it is
> WAY clean. Even turned up all the way. Twangy clean. Both channels.
Yeah. I have a silverface. It's just the same, but I like it that way!
(I also have a Tremolux that stays clean on 10!)
> I would like that old Fender overdriven tone. What's my best bet here?
Buy a Vibroverb? :-) They start to overdrive on about 4 with humbuckers.
Bassman starts at about 6, but that's too loud for home use.
> How about replacing the 12at7 tubes with 12ax7 tubes? I understand them to
> be higher-gain direct replacements. Any help/suggestions? Thanks a ton.
I doubt that this would make much difference. I'm sorry - but I think you're
stuck with the amp the way it is. Plug a Tele into it and enjoy that twang!
Of course you could always warm it up with a pedal. The Boss OD-2 works
well with Fender amps (so long as you don't use the Turbo setting).
--
Peter Jackson, Dept of Electrical & Computer Eng, Clarkson University
"Opinions expressed are not those of my employer or any other organization"
NATHAN PHILLIP STEWART
of it being a CBS Blackface (scary to think of aint it? all these people
buying blackfaces to get pre-cbs and ending up with a late 65?). In GT TAB II,
Pittman said that the Deluxe was one of the amps that was NOT changed by
CBS-Fender, and even silver faces were pretty much stock black faces for
quite a while. I don't know how far this went.
Anybody know when the Silver face era ended?
Nate
Pasi Korhonen
: Anybody know when the Silver face era ended?
According to the Gruhn book the first 'new' blackfaces were introduced
in 1982.
Pasi
--
p a s i k o r h o n e n p k o r @ p h o e n i x . o u l u . f i
saaristonkatu 3 A 6 90100 oulu finland,europe tel:358-81-377 811
Jerry Woodward
: If I'm not mistaken, the speakers also had a lot to do with achieving the
: crunch/warmth around-the-edge sound you are searching for. It's a lot
: tougher to get that warmth with a speaker designed to take a lot of power,
: like say, an EV 12" with the black-hole heavy magnet on it.
: Steve Schultz (steve....@stpaul.ncr.com) NCR Network Products Div.
: **** Coming Soon! Comments & Opinion Disclaimer Grand Re-Opening! ****
Steve (or anyone else):
I also have a 66 or 67 Deluxe Reverb that sounds pretty clean. I just
got a Les Paul and am in search of that warm, overdriven blues sound. I
am somewhat afraid to crank the amp to high for fear of blowing the speaker--
should I be? Does anyone know how many watts a Deluxe Reverb has? Could
you elaborate on the speaker--would buying an additional speaker help, and
what kind would you suggest? Finally, what kind of boxes would you box
advocates recommend? I've read about power soakers--would they do the trick?
J. Woodward
Univ. of Kentuck
META000
simply sticking in a 12AX7 for a 12AT7 may be misplaced. 12AT7's
are routinely used for reverb drivers in the standard Fender Design.
One of them (Idon't have my GT TAB-III handy to tell me) may be the
phase splitter, and can be replaced with a higher gain tube, but you
should consider exactly what you want from this baby. Is it pre-amp
tube distortion you want? power-section distortion? simply a bit
more "bite" to the tone?
Your solution may consist of simply buying a couple of high wattage
power resistors (e.g., 8 ohm 20-watt) and wiring up your own "power
soak" to generate more power-section crunch with tolerable levels.
Other things you can do are simply eliminate the negative feedback
resistor to generate more harmonic content. This only involves
desoldering one end of a rsistor, which may easily be resoldered to
original state.
If it's pre-amp distortion you want, why not just stick a level
boosting pre-amp either in your guitar or in a stomp-box. I have a
tiny pre-amp in my guitar (one transistor, low-noise, about a gain
of 5 or so) that makes those tubes sing easily, even with medium
impedance single-coils. Bear in mind that most guitar amps have a
great deal of headroom in terms of what kind of signal they will
tolerate before clipping. Most single-coil pickups don't come
anywhere near that ceiling, and all the finagling, 3-stage gain
controls, master-volumes, yaddah-yaddah-yaddah, are an attempt to
compensate for this by getting the otherwise wimpy signal up to
muscular levels. Indeed, this is what all the pre-amp tube
replacement chit-chat is about, too.
You can also try the channel-1-to-2 patch to drive the
phase-splitter a little harder. Plug into the #1 input on either
the effects or normal channel and run a patch cord from the #2 jack
ofthat channel to the #1 input of the other. You can mix the two
signals by adjusting their respective volume levels. This results
in two versions of your signal hitting whatever tubes they share in
common (phase-splitter and whatever mixing stage there might be).
Incidentally, if you are going to use some kind of outboard pre-amp
stage, it might even be to your advantage to *REDUCE* the gain of
some of your amplifier pre-amp tubes by replacing 12AX7's with
12AT7's, so you can drive the bejesus out of your first few gain
stages (e.g., with a 20db booster) without ending up with something
that's going to require speaker reconing every 3rd power chord.
Another thing you can do is something I got from an old Polyphony
article. Pasive tone controls, like Fender's, eat up signal since
they operate by selectively shunting certain frequencies to ground.
By bypassing the tone section, you retain that signal (although you
lose control over tone) and drive subsequent stages harder.
On standard Fender designs, there is either a 6.8k resistor going
from one side of the bass control to ground, or, if you have a
middle control, a 10k pot in its' place. If you lift that
connection to ground, the tone controls are effectively bypassed,
and the signal is hotter and ballsier. I did this to an old
blackface Tremolux head and made it footswitchable. Since the
tremolo on-ff function simply involves grounding a wire, and the
tone bypass involves that too, I simply stuck in a stereo jack in
place of the mono jack for the footpedal, and stuck two
on-offfootswitches in a chassis with a stereo plug hanging off the
end. Voila, instant "solo" switch. As with the negative feedback
mod, the amp can be easily restored to vintage state.
Believe me, there is tons more grit in that amp than you can
imagine. What you are currently missing is a result of the mismatch
between guitar signal level, amp headroom, and speaker efficiency.
Mark Hammer
NATHAN PHILLIP STEWART
[stuff deleted - also mentioned removing the negative feedback loop]
I removed the feedback loop on my Bassman head (AA270 model), and I got
the volume boost, but very little of the expected low end and high end rolloff,
really none to speak of. On my Bassman though, the feedback loop is tied into
the input o the phase inverter. Most earlier Fenders I saw, the feedback loop
is tied to the grid of the second stage in the phase inverter. As I sit here
trying to remember, is the output from a triode inverted relative to it's
input?, it occurs to me that both can't be. So one would seem to have a POS-
ITIVE feedback loop, which doesn't sound like a good idea to me. Anybody care
to explain?
Nate
I
META000
>.
I don't know if I can explain it, but the overwhelming majority of
"presence" controls consist of a variable negative feedback network.
That is, there is a resistor on the *speaker* side of the output
transformer (22-56k on many older model Fenders, often 820ohms on
more recent ones) which carries signal back to the phase-splitter.
On amps without negative feedback, the various resistors and caps
connected to the phase splitter go directly to ground (usually 1m
resistors), but on those *with* negative feedback, instead of going
to ground, they go to a small value resistor (about 2-5k in older
models, about 100ohms in newer ones) and THEN to ground. The
negative feedback resistor also connects to this point, so that,
between the negative feedback resistor and connecting resistor, they
act as a voltage divider for the negative feedback (e.g., 820ohm
feedback, connected to 100ohm to ground, reduces the feedback
signal). Presence controls usually run in parallel with the
resistor going to ground, only they have a blocking capacitor (i.e.,
the signal could take one path through the low value R, or another
path through the cap and lower value R, to ground). In a sense
they can create a lower resistance path to gnd for high-freq signals
(clearly Tom, Don, Dave, Nate, and RG will castigate me for this,
but I'm trying to make it simple forthe non-EE types).
So, why am I telling you this? Presence controls introduce negative
feedback to keep harmonic distortion under control. You can
decrease negative feedback (thus unleashing more of the distortion)
by two means: by dividing down the feedback signal via a presence
control, or by simply eliminating the source of it by lifting the
negative feedback resistor. Clearly, the effect this will have
depends on the amount of distortion generated by the design in the
first place (including power-tube distortion, output transformer
distortion, etc.), and the role that speaker impedance plays
(remember, the negative feedback resistor is tied to the same point
at the output as the speakers are.), which is why I suspect that not
all amp designs have them (i.e., why stick in a control that
produces little noticeable effect under anything other than extreme
conditions?).
I lifted the negative feedback resistor from my 59 Princeton (a
single 6v6-based 6-watt/8-inch honey) and noticed more bite
(although a bit less sag, unfortunately). Then, I replaced the
power tube with a 6L6GC (replacing 6V6's with 6L6's is more or less
okay but DO NOT replace 6L6's with 6V6's). Running in single tube
Class A configuration, the 6L6 puts out a bit more power than the
6V6 (under ideal circumstances, with optimal plate voltage, about
twice as much, but remember this is an amp that assumes a 6V6 in the
socket, so the plate voltage is about 2/3 what it could be), but OY
VAY!, the crunch! We're talking ice-pick sound here. We're talking
Johnny Guitar Watson with an overdrive! We're talking Billy Gibbons
with the treble ALL the way up! The reason? Simply that the 6L6
generates about twice as much harmonic distortion as a 6V6 in
Class-A mode, and when you eliminate the negative feedback to keep
it under control.....
All of which suggests that the inidividual with the squeaky clean
Deluxe might want to replace the 6V6's in there with 6L6's. This
will increase your power output, but if you use some power resistors
configured as a kind of power soak alongside your speakers, the
output shouldn't be too much of a problem (HINT: if your speakers
are, say, 8-ohms each, and are wired in parallel, they present a
4-ohm load to your amp. Wire them in series, so they form a 16-ohm
load, and stick an 8-ohm 20-watt power resistor in parallel. This
will divide the output so that your speakers see less of it, and
will provide an output impedance just a tad higher than what the amp
expects to see.)
Jeez, you'd never think that it would take so much frittering to
reverse all the years of R & D that led to high quality sound
reproduction!
Mark Hammer
P.S.: Now that I think of it, would expendable 8-ohm speakers with
the majority of the cone cut out serve a useful function as power
soaks? Bear in mind you want something that poses the same kindof
load but has a reactance as well as a resistance, without creating
sound. Clearly resistors, by themselves have no reactance, and
extra speakers create sound, even though they can divide down the
output. To get them to react like speakers, but eliminate the
sound, you'd have to cut out most of the cone, but leave enough to
suspend the voice coil in the gap so it can move around. Its a bit
like those dummy pickups-without-polepieces that people use to
cancel hum. In the case of those, you want one characteristic of
the pickup (its' antenna-like characteristic for picking up hum
and RF), but not the other (its' capacity to pick up string
vibrations). What I'm suggesting here is keeping one characteristic
of a speaker (its voil-coil reactance and impedance), while
eliminating the other (its' air-moving, sound-producing capacity).
Hmmmmm.......I might be on to something here.
Don Tillman
Organization: North Carolina State University, Project Eos
Date: Sat, 24 Jul 1993 03:19:24 GMT
I removed the feedback loop on my Bassman head (AA270 model), and I got
the volume boost, but very little of the expected low end and high end
rolloff, really none to speak of. On my Bassman though, the feedback
loop is tied into the input o the phase inverter. Most earlier Fenders I
saw, the feedback loop is tied to the grid of the second stage in the
phase inverter. As I sit here trying to remember, is the output from a
triode inverted relative to it's input?,
Generally, yes.
it occurs to me that both can't
be. So one would seem to have a POSITIVE feedback loop, which doesn't
sound like a good idea to me. Anybody care to explain?
Almost all Fender amps have a phase splitter stage that's a differential
amp built from the two halves of a 12AT7, and wired in the standard
noninverting-gain-with-feedback configuration. But there are a couple
exceptions in very old models.
Your AA270 is one of the exceptions; it has the diff amp in is a
standard inverting-gain-with-feedback configuration -- this means the
output transformer windings need to be swapped relative to the other
models so that the power amp is inverting. (It seems the schematic has
the output transformer wired backwards.)
I have no idea why they designed this model differently and then
reverted back so quickly.
Yeah, positive feedback would be a disaster.
-- Don
David Covell - EPG
>boosting pre-amp either in your guitar or in a stomp-box. I have a
Excellent advice. The Fender input stage was designed to minimize distortion
and to accept a very wide range of signal levels. Most Fenders respond well
to a hotter signal, providing a range from sweet to fat to edgy. The
touch-response is heightened too; you'll be able to go from nearly-clean
chords to a biting lead tone by simply picking harder.
Any effects device with variable output gain can be used, though the cheaper
ones such as Digitech (ducking the flames...) will get pretty noisy. The
old Electroharmonix LPB-1 or 2 is ideal for this sort of thing and has lots
of *relatively clean* gain. My Echoplex has both a high-gain and normal
output, and the high-gain one does marvellous things to my Twin and Super
Reverb.
The really good thing about this approach is that you lose a lot less of the
high frequencies by avoiding the injection of extra 12AX7 gain stages ala
Boogie, ADA MP-1, etc. I love my Boogie, but the lead channel lacks the
sparkle of the clean channels; the solution in my case is to run a hotter
signal into the clean channel. Sounds much better, with almost no loss of
top end.
Note that this approach probably won't satisfy those who are looking for
massive crunch and sustain-for-days; the tone is much more subtle. I suppose
if you ran a hot enough signal in that you could drive the input stage into
hard clip but I suspect it would sound pretty bad (and hiss like a thousand
rain storms).
Robert J. Cardinali
In a previous article, ME...@UNB.CA (META000) says:
[mind-boggling explanation of feedback loops, and tone shaping deleted]
...and by the way, Thank You for the above mentioned deleted explanation!
I didn't mean for that deletion tag to be at all insulting. You explained
a complex technology as clearly as anyone I have ever seen do it. Now, as
to the concept described below....Correct me if I am wrong, but the mass of
the cone contributes to the reactance of the voice coil engine. And it
would also affect the impedance, no? I would think that a voice coil
suspended in just a spider might have a boatload of different
characteristics than the original speaker had. Also, Since we are talking
about reducing the volume of the output, or at least having control over
it, how would adding the dummy load accomplish this? Running it in series
with the active speaker? I am missing something here I think.
My dad (EE - Cornell 1934) made me a little rat-shack metal project-box
style power soak for my Deluxe (circa 1965 - I don't remember, I sold it in
1972!) that contained a Ohmite (tm) variable resistor. I believe it was a
20 watter, 8 ohm, but I could be wrong. It was about 2 pounds, made out of
ceramic, and got hot as hell when I drove my amp through it hard. It
worked like a charm, and I never had any problems with this amp. I was
BRUTAL with it too...Used to use an Electro Harmonix Power booster on the
input side, with a '67 SG Standard. Cry Baby Waa in there too, for
texture. I got many years of use out of that thing, and loved it dearly.
I rigged a similar unit up later on, and used it on Dual Showmans and
Bassmans. Not a lick of a problem.
>
>P.S.: Now that I think of it, would expendable 8-ohm speakers with
>the majority of the cone cut out serve a useful function as power
>soaks? Bear in mind you want something that poses the same kindof
>load but has a reactance as well as a resistance, without creating
>sound. Clearly resistors, by themselves have no reactance, and
>extra speakers create sound, even though they can divide down the
>output. To get them to react like speakers, but eliminate the
>sound, you'd have to cut out most of the cone, but leave enough to
>suspend the voice coil in the gap so it can move around. Its a bit
>like those dummy pickups-without-polepieces that people use to
>cancel hum. In the case of those, you want one characteristic of
>the pickup (its' antenna-like characteristic for picking up hum
>and RF), but not the other (its' capacity to pick up string
>vibrations). What I'm suggesting here is keeping one characteristic
>of a speaker (its voil-coil reactance and impedance), while
>eliminating the other (its' air-moving, sound-producing capacity).
>Hmmmmm.......I might be on to something here.
>
>
--
Bob Cardinali
ck...@cleveland.freenet.edu
Robert J. Cardinali
In a previous article, dco...@frx702.intel.com (David Covell - EPG) says:
>In article <23JUL93.18...@UNBVM1.CSD.UNB.CA> META000 <ME...@UNB.CA> writes:
>>
>>If it's pre-amp distortion you want, why not just stick a level
>>boosting pre-amp either in your guitar or in a stomp-box. I have a
>
>Excellent advice. The Fender input stage was designed to minimize distortion
>and to accept a very wide range of signal levels. Most Fenders respond well
>to a hotter signal, providing a range from sweet to fat to edgy. The
>touch-response is heightened too; you'll be able to go from nearly-clean
>chords to a biting lead tone by simply picking harder.
>Any effects device with variable output gain can be used, though the cheaper
>ones such as Digitech (ducking the flames...) will get pretty noisy. The
>old Electroharmonix LPB-1 or 2 is ideal for this sort of thing and has lots
>of *relatively clean* gain. My Echoplex has both a high-gain and normal
>output, and the high-gain one does marvellous things to my Twin and Super
>Reverb.
That's what I used for years....the old LPB-1...with the Power Soak
described in a previous post....magic.
--
Bob Cardinali
ck...@cleveland.freenet.edu
META000
>
>In a previous article, ME...@UNB.CA (META000) says:
>
>[mind-boggling explanation of feedback loops, and tone shaping deleted]
>
>.
Thanks for the positive comments. My suggestion about the deconed
speaker was intended to come closer to the "ideal" fake load. You
are absolutely right about the deconed version having dramatically
different operating characteristics, and I suspect some kind of
weight adjustment might be apropos. Having said that, however, it's
unclear to me what, other than an ideal mimicry of the speaker you
want to normally use with that amp, that weight adjustment should
be. Realistically, any appropriately impedance matched speaker/s
will react pretty much the same way, in *ballpark* figures, since
bigger signals will make them move back and forth more, and smaller
signals make them move less. I suspect that's really what you want
from such a dummy load, more than anything else. Other than being
weighted so that the voice-coil doesn't pop out of the frame, the
simulation of the original motion characteristics of the intact
speaker (within limits) is moot (i.e., it doesn't have to have all
the timbral characteristics as well). Your comments about "nominal"
impedance is also spot on. Having a transformer between the
speakers and output stage (as all tube amps and only some transistor
amps do) tends to reduce the need for critical matching of load and
output stage, although one still needs to behave reasonably so as to
avoid transformer meltdown (e.g., running an amp full tilt into a
2-ohm load that ought to be a 16-ohm load is uncool, literally and
figuratively).
Okay, so how does the deconed speaker do it's job?
The amp can only do so much "work" (in physics terms). That "work"
is distributed amongst the output components (speakers, etc.) that,
in turn, do "work". Some of the work that the speakers do is
acoustical (i.e., moving air) but they also waste some of the amp's
work in heat (which most voice coils are designed to keep to a
minimum), even though you might not be able to detect it with your
hand.
When you have more than one speaker attached to the amp, each of
these "workers" takes on half of the work assigned to the output
load by the amp (assuming they are in parallel and of equal
impedances). So, for instance, if you have a 50-watt amp that
should go into an 8-ohm load, running it into two 16-ohm speakers,
each rated for 25 watts capability, should, theoretically be enough.
"Power Soaks" also do work for the amp, but all they do is heat
work, and no mechanical work. The amp will still function if a
resistor that matched the required output resistance, and heat
dissipation characteristics, is substituted for speakers. However,
it would seem that what we want from a guitar amp seems to be a
result of a load that *varies* in a dynamic fashion, rather than a
static load (such as a resistor). There are, no doubt, other ways
of creating a load that varies, but the
speaker-which-moves-no-air-yet-has-an-impedance (sounds like kind of
a hi-tech aboriginal name, doesn't it? maybe more zen-like) struck
me as away of dividing down the work that the amp sends to the
output so thati the desired nominal impedance is maintained. The
remaining active speaker/s has less work to do (since the work is
shared with the dummy load), and the work done by the deconed
speaker results in little or no audible sound.
Practically spoeaking, here's what you'd do. Say you normally have
the amp's output going to two 8-ohm speakers in parallel (making a 4
ohm load). You like the 2 speaker arrangement, but want less
overall volume when really pushing the amp. Wire the two speakers
in *series* so that they now form a 16-ohm load. Now wire up two
deconed 8-ohm speakers in series (or use a 16-ohm one if you have
it), and place them in parallel with your original speakers. You
now have approximately half the work being assigned to the output
load ending up as mere coil movement.
As for "power soaks", you'd do the exact same thing, except instead
of speakers, you'd use appropriate power resistors. As mentioned
earlier, since dividing down the work between multiple components
reduced the amount of work done by each component (many hands make
light work), for a 50-watt amp, use of 20-watt resistors (as in the
above example) should be more than adequate.
One thing I should mention is that part of what some players like is
the speaker "breakup"; that is the distortion created by the actual
speaker itself, rather than some characteristics created by
reactive-load/amp interaction. For example, this is supposedly one
of the desirable characteristics of the old blue-frame Jensens in
older Fenders (which Kendrick has attempted to simulate). In view
of this, whatever one does to divide down the amp output so as to
render part of it useless might want to take this into account.
If you normally send your amp's output to 2-12's, and part of what
you like is the way the speakers break up, maybe what you want to do
is to dis-connect one of the speakers and wire in a dummy load
(either deconedspeaker or power resistors) so that one of the
speakers is being pushed hard enough to break up, while the total
load remains appropriate, and the total air-volume being moved is
reduced (creating a lower volume at the ear). Again, it's a
question of compromise between a number of different factors that
provide the sound aspect you cherish.
Okay guys, I have to finish loading the truck. I'm moving today.
See you in a few months. Mark
P.S. Sounds like you have a pretty cool dad, Bob. Mine was a
machinist and helped me make my first solid brass bridge/tailpiece
in 1968. They may have liked Artie Shaw more than Elvis, but dads
can be real rock-friendly on occasion.