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Cascading or slaving tube power amps,
Using a tube power amp and dummy load as a power-tube saturation pedal

First, on the principle that overdrive sounds like power-tube saturation into a dummy load, I tried overdrive pedals in series:

 

guitar

eq

overdrive pedal

eq

overdrive pedal

eq

linear amp

guitar speaker

 

That didn't sound good, no matter what the EQ curves and gain levels.

 

Next, I tried tube power amps in series:

guitar

eq

tube power amp & dummy load

eq

tube power amp & dummy load

eq

linear amp

guitar speaker

 

Think of the latter as:

guitar

eq pedal

power-tube saturation pedal

eq pedal

power-tube saturation pedal

eq pedal

linear amp

guitar speaker

 

 

The latter worked super-great; try it.  The chain I used is:

 

Single-coil neck pickup

 

EQ pedal with moderate smile

Tube power amp at 7% saturation (no-features old PTP tube amp)

Dummy load (Line Out of Hot Plate)

 

EQ pedal with moderate smile

Tube power amp at 7% saturation (Blues Jr, injecting via rev.tank ret.)

Dummy load (Power Brake on next-to-last attenuation, then Radio Shack inline headphone volume control pot)

 

EQ pedal with moderate smile

Solid-state power amp (stereo receiver)

Guitar speaker (Blue Jr's cab)

 

 

This sounds like power-tube squash, multiplied, at any volume.  Connecting headphones instead of the guitar speaker, the sound was interesting but not classic, even with final-eq rolloff applied.  It sounds classic through the guitar speaker.  I'd like to hear it with a good cab-sim filter instead of the guitar speaker -- to see if this circuit could be inserted into a POD between the distortion and timefx stages for better results, or in the fx loop of a well-designed guitar preamp/processor.

 

I'll add this to the Amp Tone Reference & Test Input Library CD-R.

http://www.amptone.com/reamp.htm

 


Cascading a series of UniValve amps; using a UniValve with Line Out as a superior overdrive pedal

 

Congratulations to THD on the great enthusiasm people are showing for the UniValve -- higher than any other NAMM product.  (See ratings at bottom of

http://namm.harmony-central.com/WNAMM01/Content/THD/PR/UniValve.html ).

http://www.amptone.com/thdunivalve.htm - info/links

 

 

This type of processing chain produces a great multiplied power-tube saturation sound at any volume.

 

UniValve #1 at 7% power-tube saturation

UniValve #1's full dummy load and Line Out jack

 

UniValve #2 at 7% power-tube saturation

UniValve #2's power attenuator

Guitar speaker pushed to 3/4 watt

 

 

That is, instead of using overdrive pedal > tube power amp, use tube power amp > tube power amp.

 

I am looking forward to a literal power-tube saturation pedal with an actual traditional power tube such as EL84, wired to always push a dummy load, in a stompbox format.  The UniValve comes very close to this new type of distortion box, a power-tube saturation pedal.  Then I would do this chain:

 

EQ pedal

Power-tube saturation pedal

EQ pedal

Power-tube saturation pedal

EQ pedal

Linear amp

Guitar speaker pushed to 3/4 watt

 

I will demo this chain on the Amp Tone reference/test input library CD-R I'm working on.  It's the most interesting distortion approach I've heard.  Overdrive pedals claim to sound like a cranked tube amp.  If a cranked tube amp is what we want, then we should simply insert a cranked tube amp with dummy load, rather than an overdrive pedal.  It works well for classic sounds (at any volume), unless the buzzy preamp-distortion sound is considered classic.  For the buzzy "Saturday morning guitar store" preamp-dominant sound, remove the first power-tube saturation pedal and insert a Tube Driver-type of preamp-tube distortion pedal.  Fit into the classic chain, this placement results:

 

Compressor pedal

Power-tube saturation pedal

Overdrive pedal

Distortion pedal

Tube power amp

Guitar speaker

 

Since the power-tube saturation pedal is being used as a softer-than-overdrive preamp pedal, for placement, I work backwards from the hard-edged distortion box, to the softer overdrive box, to the softest: the power-tube saturation pedal.  I will set up a BOSS Line Switcher pedal (again) to create a stompbox from a tube power amp and dummy load, and try swapping this pedal's positioning vs. the overdrive and distortion pedal.  In any case, assuming you will use *either* the overdrive pedal or distortion pedal or power-tube saturation pedal, but not combinations, it doesn't matter the relative order.  The main point is that you are stomping on the 3 pedals to swap which type you are using.  Sometimes for preamp distortion you want hard-edged "distortion" clipping, sometimes you want soft "overdrive" clipping, and sometimes you want ultra-soft "power-tube saturation" clipping.  In all cases, later in the chain is a tube power amp with a slight amount of saturation, pushing a guitar speaker (perhaps through a power attenuator).

 

-- Michael Hoffman

Amptone.com

 

p.s. If you are looking forward to receiving the Amp Tone reference and test-input library CD-R I'm going to send out, it would help a lot if you would start gathering clips of album amp tone samples and direct/dry electric guitar playing.  http://www.amptone.com/reamp.htm

 

______________________________________________________

 

> I'm a 2nd year Electrical Engineering major and a guitar freak. I'm

> interested in combining the two and possibly building a guitar amplifier

> from scratch(resistors, capacitors). I'm wondering if anyone out there knows

> anything about how to do such a thing. Also if you have resources, books, or

> web sites that may be of help to me.

 

Eric,

 

There are now many resources for this.

 

http://www.amptone.com/ - ampsresources

http://www.ax84.com/ -- especially check out the concept of the Rail Rocket 3-stage amp, which produces power-tube saturation at any volume.

preamp distortion

low-wattage tube power amp

full dummy load

high-wattage tube power amp

guitar speaker

 

Think of the inner tube power amp and dummy load as a power-tube saturation pedal.  The coolest thing you could do is design and build a power-tube saturation pedal: an EL84 tube power amp, with zero features and minimal parts, in a stompbox format.  You would be the first person to build a to-the-point power-tube saturation pedal as such.  Similar but unfocused products are the Crunch Master, Lawbreaker, UniValve, and Pedaltone - see Amptone.com.

 

I was in Electrical Engineering school when the vacuum tube was first brought together with MIDI -- the ADA MP-1 preamp tube distortion box.  I wanted to create a clone as a senior project, but something wasn't right -- it turned out that preamp distortion is far less important than power-tube saturation.  First, you could build a maximally simple power-tube saturation pedal.  Then, to do an important project, the ultimate project would be a GUI-programmable power-tube saturation pedal.

 

I would use the pedal in alternation with EQ pedals, such as:

 

eq pedal

distortion pedal

 

eq pedal

power-tube saturation pedal

 

eq pedal

power-tube saturation pedal

 

solid state power amp

guitar speaker

 

-- Michael Hoffman

Amptone.com

 


cascading tube amps and dummy loads - "Joe uses an 80's Fender Vibroluxe that's very near stock along with his Acoushall. He has an Altair Power Attenuator, which he'll use with one or the other of those amps, and then run a line out of there to the other amp."

Licho's to-the-point power-tube saturation pedal circuit - I recommend eq > power tube/dummy load/trim pot > eq > high-power amp > guitar speaker pushed above 1 watt > gobo or isolation box/hood/closet/booth. He uses this in the fx loop of his conventional amps and 5-watt DIY amp.

VHT: slaving an amp - "What is slaving? This is a method for using amp heads or combos as a signal source in amp/power amp systems or multiple amp systems. The term simply refers to the practice of using one amp (typically a head or combo) as the "Master" amp or primary tone source, and another (typically a power amp) as the "Slave" amp which does the work of driving the speakers. Slaving allows you to generate just the right blend of preamp and power amp distortion in your Master amp. The resulting output is then attenuated down to a practical signal or line level which can then be routed to a switching system, mixer, effects processor, stereo power amp, recording console or any combination of the above. These kinds of applications are especially useful in live situations where it is desirable to reproduce a variety of different amplifier and distortion characteristics that may have been originally produced in a studio environment with multiple amps and speakers. It usually involves running the Master amplifier "full out" into an enclosed speaker or "Dummy Load" such as a high power resistor or power attenuator. A low level signal is then taken from the Master amp output using the "line output", an external signal attenuator (pad), or some type of speaker emulation device, which is then sent to an effects system, power amp and then to a pair of speaker cabinets. This is not generally considered to be the most practical of systems, but when done right, it's pretty hard to beat. Anyway, who cares about practical when your main objective is ultimate sonic satisfaction?"

harp techniques to min fdbk - "Put in a "pickle plug". Wire a socket from the speaker of your tube amp that directly plugs into the PA or another amp. This is a good way to pop an amp, but some people swear by it. [With conventional Google search of web pages, couldn't find info about pickle plug]. ... Slave two amps. If you have an amp with two inputs, you can run another cable from the input of the first amp to the input of another amp. You can have several amps daisy chained. Some amps have a 'Hot' side which goes through an extra pre-amp stage. Plug your mic in this hole and then run a cable from the 'normal' socket to another amp. You'll get the benefit of an extra pre-amp stage before the second amp. This configuration really kicks ass. The logic here is that two amps on 5 is equal to one amp on 10. (Actually, it's probably a log curve, 5+5=7)"


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