Allan Holdsworth's "Harness"

Paul Marossy · July 16, 2007, 11:38:01 AM

This question is for anyone who might be familiar with this device that's not a power attenuator. I've looked at these pictures, and am baffled by how it works/what it does (other than what it says in the manual). Holdsworth apparently hand made these himself. He's a freakin' genius in more than one area!

Mark Hammer · July 16, 2007, 01:50:24 PM

Without the description, I could swear that it's a pinball game I played once.

The "springy things" are undoubtedly heater coils, not dissimilar from what you find in toaster ovens or toasters. I would assume that they are not pushed to the point where they would normally glow orange or generate heat

Paul Marossy · July 16, 2007, 02:04:49 PM

Yeah, I was just thinking that those must be resistive heater elements.

GFR · July 16, 2007, 02:06:58 PM

I've read an interview with Holdsworth in Guitar Player magazine. He said he was doing some experiments with recording techniques - he would run a mesa boogie amp into a dummy load and speaker emulator (that's problably this thing), then run the output of this into another mesa boogie amp, mic the cab and record that... Talk about high gain...

Paul Marossy · July 16, 2007, 02:18:26 PM

Yeah, but he claims that his "Harness" is not a speaker emulator, either. So, what the heck is it?!

EDIT: My current thoughts are that it somehow takes the amplifier output, dissipates the excess heat caused by knocking the power level down and somehow does impedance matching to some line level outputs.

Paul Marossy · July 16, 2007, 02:38:34 PM

Here's a link to the owners manual, it might give us some clues...

http://www.fingerprintsweb.net/forum/upload/harness-manual.pdf

Mark Hammer · July 16, 2007, 02:50:22 PM

"Not a speaker emulator" will depend on what you mean by "emulate". It doesn't appear to be designed to emulate the characteristics of any particular speaker or cabinet, so it's not an "emulator" in that sense. On the other hand, it certainly attempts to "emulate" or mimic the electronic characteristics of a speaker, as seen by the amp's power section. In that sense, it falls into the same broad category as the Power Brake, Hot Plate, and similar products. From the looks of the innards, he's using a different approach, but the goal is still the same: high-current/low-load levels in, line-level out.

Paul Marossy · July 16, 2007, 02:53:26 PM

QuoteFrom the looks of the innards, he's using a different approach, but the goal is still the same: high-current/low-load levels in, line-level out.

Yeah, it would seem to be. I am really curious as to exactly what his approach is - it's an almost mystical looking device. It's also different in that it's designed for stereo processors, not for a mono signal to be put between an amp and a speaker.

soulsonic · July 16, 2007, 03:03:03 PM

Quote from: Mark Hammer on July 16, 2007, 01:50:24 PM

The "springy things" are undoubtedly heater coils, not dissimilar from what you find in toaster ovens or toasters. I would assume that they are not pushed to the point where they would normally glow orange or generate heat

I"m sure they will absolutely generate heat - potentially alot depending on how much power you put into it.

It is a dummy load with a line out..... more like a Palmer Speaker Simulator than a Hot Plate, but without a cab sim filter on the line out. Anyone have any ideas about what those white ceramic cylinders are? There's enough of them in the circuit that they must be important.

Paul Marossy · July 16, 2007, 03:06:26 PM

QuoteAnyone have any ideas about what those white ceramic cylinders are? There's enough of them in the circuit that they must be important.

Those are what I'm most curious about.

soulsonic · July 16, 2007, 03:13:06 PM

Okay, I looked through the manual. The Harness is a "Slaving Box". It's primary purpose is for slaving one amp to another. That's probably why he won't call it a speaker emulator. In the instructions it says "Patent Applied For" in several places. Someone should try looking up the patent for this. If he was granted the patent, the schematic and description of how it works is considered public domain and free to view (like any patent).

Mark Hammer · July 16, 2007, 03:15:44 PM

1) It's rated for 100W. Your toaster is intended to pass far more current than that. My guess is they will be warm, but far fromred hot.

2) From the photo, it seems like the leads coming from the white ceramic cylinders are magnet wire, in which case the cylinders are simply hand wound chokes/inductors.

Paul Marossy · July 16, 2007, 03:18:57 PM

Yeah, I was thinking that they were probably inductors. Good idea on the patent search, that would be a good resource.

EDIT: Did a quick patent search, couldn't find anything. I think that Allan may have sold his idea to Rocktron for their "Juice Extractor" product.

d95err · July 16, 2007, 03:30:39 PM

My guess would be inductors too. It's probably some kind of reactive dummy load.

Aiken has an article about reactive speaker loads:

http://www.aikenamps.com/spkrload.html

Paul Marossy · July 16, 2007, 05:44:08 PM

QuoteThe Harness is a "Slaving Box". It's primary purpose is for slaving one amp to another.

Well... yes and no. What he's really doing is using tube amp distortion, and sending the output of that to "The Harness", the output of which is running in stereo to stereo processors and then to a stereo power amp (or pair of amps, which is what he seems to prefer).

QuoteIt's probably some kind of reactive dummy load.

It appears to be something along those lines, but a little fancier since it's stereo.

soulsonic · July 16, 2007, 06:03:47 PM

Even though he puts a big emphasis in the manual on the use of stereo effects, the unit itself is mono. 1 input jack, 1 output jack.
I'm not sure what the extra controls and switches are for, and that brings up an important note: this is not a stock unit - it has some added features which are not described in the manual. It says clearly on the chassis that it's a "custom" unit - so who knows what's going on in there.

Is the unit yours? Can you take it apart further so we may study it closer? If I had the thing in front of me, I could have the whole thing traced and figured out in probably less than an hour - it looks like a very simple circuit.

Paul Marossy · July 16, 2007, 06:08:11 PM

I don't have the unit myself, unfortunately. The one in the pictures looks like it's a stereo unit to me - looks like two input jacks and two output jacks...

aron · July 16, 2007, 06:28:48 PM

Maybe this helps a little. I remember reading about the resistive element.

http://www.duncanamps.com/technical/dummyload.html
http://people.sinclair.edu/nickreeder/EET150/mod07.htm

Paul Marossy · July 16, 2007, 11:21:30 PM

My mistake, I guess it is mono, I thought one of those switches on the back was a jack...

goosonique · July 16, 2007, 11:36:46 PM

Very interesting indeed

QuoteAnyone have any ideas about what those white ceramic cylinders are?

Looks like spools to me .... btw i totally dig Allan's worx...lots of tricks!

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Allan Holdsworth's "Harness"