Best-sounding attenuator?

[jeremy]

ilike the idea of power scaling but dont know if ive actually tried an amp with it.

Originally Posted by StillLearnin'

if you like your tone, the only one that really keeps it is the Power Brake.

i found that the power brake changed the tone more than the mass. i only still own the old style mass but had a power brake too. ended up selling it after i got the mass.

[MattPete]

Powerscaling works remarkably well, and once you know how it works, it makes you wonder why no one thought if it in the past (although scaling the bias in a fixed-bias amp is understandably tricky).

As for the Weber Mass, I bought a Mass Lite without the treble control. Shortly after I bought mine, they started shipping with a tone control, so maybe that makes a difference. But at least for my version, it sounds like a wet blanket was thrown over the amp and is unusable.

[RLee]

Has anyone tried the power scaling kits from London Power? Looks interesting.

Explanation of it: http://www.londonpower.com/pscaling.htm
Demo: http://www.ratvalveamps.com/power-scaling

The important aspect of the demo is that while the amp sounds cranked, you can easily hear the finger snaps.
But I'm completely skeptical of the claim that you can lower the plate voltage greatly and not alter the tone / character of an amp. And it still suffers from the same flaw as other methods of taming amp output -- speakers sound different at very low levels, output transformers sound different when not pushed near saturation, etc.
Still, though, I'm intrigued.

[ImmortalSix]

Originally Posted by MattPete

Powerscaling works remarkably well, and once you know how it works, it makes you wonder why no one thought if it in the past (although scaling the bias in a fixed-bias amp is understandably tricky).

As for the Weber Mass, I bought a Mass Lite without the treble control. Shortly after I bought mine, they started shipping with a tone control, so maybe that makes a difference. But at least for my version, it sounds like a wet blanket was thrown over the amp and is unusable.

I only use my MASS with the +3dB Treble compensation. That sounds equal to the true tone of the amp to me. With it off (0 dB), it sounds as you described, muffled, and with it on +6dB, it has a treble booster sound, like a Brian May tone.

You can see my video demo of the Weber Mini MASS here, where I describe every feature in detail.

Also, check out the newest MASS, they have a ****load of tone controls.

[jeremy]

those tone controls are only for the direct out. i do like the footswitchable bypass though

[RLee]

I ran across this youtube demo of the mass, and this guy cracked me up:
http://www.youtube.com/watch?v=oo5gxyUWQ2Q

[MattPete]

Originally Posted by RLee

Has anyone tried the power scaling kits from London Power? Looks interesting.

Yep, I've installed it in a Metropoulos Plexi. Arena sound at bedroom volumes. It works as advertised.

[RLee]

Originally Posted by MattPete

Yep, I've installed it in a Metropoulos Plexi. Arena sound at bedroom volumes. It works as advertised.

The harmony central reviews were really negative for it.

[RLee]

Found another attenuator that I think I may go with, called the TubeCube. Website here: http://www.thetubecube.com/component...mart/Itemid,1/

But the products seem to be available only via ebay currently. I find the guy's candidness and very reasonable pricing very refreshing, amidst all the overpriced and over-hyped products from the big manufacturers. I mean, these are essentially simple circuits, there is no excuse for companies charging $300-$700.

[MattPete]

Originally Posted by RLee

The harmony central reviews were really negative for it.

I'd take those Harmony Central reviews with a huge grain of salt. The original kits were a little green (as were the instructions), but the concept is sound. A simpler variant for cathode biased amps was designed by the 18watt community (VVR mod) and sounds great.

Suhr Badger with Powerscaling:

Long and detailed (8:30 gives a good example of scaling):
http://www.youtube.com/watch?v=HBUxUB-6qjw

Short:
http://www.youtube.com/watch?v=2Ooh4x6GuXA



Soultone Powerscaled Plexi at bedroom levels:
http://www.youtube.com/watch?v=qrIkBnlR5lw

2:40 on up gives a great demonstration of power scaling:
http://www.youtube.com/watch?v=24KWL...eature=related

[RLee]

Originally Posted by MattPete

I'd take those Harmony Central reviews with a huge grain of salt. The original kits were a little green (as were the instructions), but the concept is sound. A simpler variant for cathode biased amps was designed by the 18watt community (VVR mod) and sounds great.

Suhr Badger with Powerscaling:

Long and detailed (8:30 gives a good example of scaling):
http://www.youtube.com/watch?v=HBUxUB-6qjw

Short:
http://www.youtube.com/watch?v=2Ooh4x6GuXA



Soultone Powerscaled Plexi at bedroom levels:
http://www.youtube.com/watch?v=qrIkBnlR5lw

2:40 on up gives a great demonstration of power scaling:
http://www.youtube.com/watch?v=24KWL...eature=related

Thanks for the links. The last video there was really quite surprising and revealing... in a good way. Around 2:25, he dials down to max scaling (min volume) and the tone doesn't change much, but -- you can now clearly hear his pick strokes over the sound of the chords! Very impressive.

[MattPete]

The only bad things about powerscaling is (1) it is a permanent change to an amp, instead of an attenuator you can switch between amps, and (2) it's a pain to retrofit (especially PCB board amps).

[Bludave]

I've never used one but i do own a Komet 60. I can say from my experience that the Komet Company makes nothing without it being the best quality.

http://www.kometamps.com/accessories.html

[RLee]

Originally Posted by MattPete

The only bad things about powerscaling is (1) it is a permanent change to an amp, instead of an attenuator you can switch between amps, and (2) it's a pain to retrofit (especially PCB board amps).

I'm not that concerned about mods to my amp, the most important thing is the end result. Currently I'm looking at 3 options for taming a 50 watt amp... 1. A Lar/Mar ppimv, which I already have the parts for; 2. An attenuator like the TubeCube or Weber; 3. Power scaling, which is actually less money than an attenuator and may be the best sounding option.

[MattPete]

RLee: What sort of amp would this be for?

[RLee]

A marshall 1987X 50w plexi reissue

[MattPete]

A couple of notes about Plexis, powerscaling, and such.

1) If it's a Plexi, you might want to try a post-phase inverter master volume. No, it's not powerscaling, but the tone is 50% there. Basically, it allows you to overdrive the preamp and phase inverter, but not the poweramp. The key with a Plexi is that comapred to other amps, phase inverter distortion makes up a larger part of the signature sound.

2) As for power scaling: London Power sold power scaling, sells power scaling, and then there is power scaling. The gist of the method is the same, but their is different implementations. What powerscaling does is to scale the voltage going to the poweramp tubes. For fixed biased amps (as opposed to cathode biased), it also needs to scale the bias.

London Power has sold kits (an external box that wires into your amps) and schematics. Even then, they've changed the way they scale (AC vs. DC?). I installed an external scaling module into my Metropoulos Plexi. It's not the neatest install, as it is an external module tucked away inside the cab, and I need to reach around back and inside to twiddle the voltage knob. I installed a PPMIV with the knob coming out of the second speaker jack. In this installation, it acts like the drive compensation (as you turn down the voltage, you also need to turn down the signal sent to the poweramp). They've since change the kit and schematics (DC to AC?) which is much less likely to blow out mosfets, which was an issue for some folks.

Having said all that, I would have preferred to used the schematics (rather than the kit) and install it into the original build, so that I had an cleaner install (e.g controls in front). But, that also takes some planning and scheming on your own (or by your amp tech). It's not plug-and-play: you need to understnad the circuitry before you jump in.

For what it's worth, the 18watt VVR mod is functionally equivalent to powerscaling, except that it does not change bias (cathode-biased amps like 18watts automatically change their bias). The magic of powerscaling is that it also automagically adjust the bias -- which is NOT what a variac does (despite the Harmony Central claims).

[RLee]

Originally Posted by MattPete

A couple of notes about Plexis, powerscaling, and such.

1) If it's a Plexi, you might want to try a post-phase inverter master volume. No, it's not powerscaling, but the tone is 50% there. Basically, it allows you to overdrive the preamp and phase inverter, but not the poweramp. The key with a Plexi is that comapred to other amps, phase inverter distortion makes up a larger part of the signature sound.

2) As for power scaling: London Power sold power scaling, sells power scaling, and then there is power scaling. The gist of the method is the same, but their is different implementations. What powerscaling does is to scale the voltage going to the poweramp tubes. For fixed biased amps (as opposed to cathode biased), it also needs to scale the bias.

London Power has sold kits (an external box that wires into your amps) and schematics. Even then, they've changed the way they scale (AC vs. DC?). I installed an external scaling module into my Metropoulos Plexi. It's not the neatest install, as it is an external module tucked away inside the cab, and I need to reach around back and inside to twiddle the voltage knob. I installed a PPMIV with the knob coming out of the second speaker jack. In this installation, it acts like the drive compensation (as you turn down the voltage, you also need to turn down the signal sent to the poweramp). They've since change the kit and schematics (DC to AC?) which is much less likely to blow out mosfets, which was an issue for some folks.

Having said all that, I would have preferred to used the schematics (rather than the kit) and install it into the original build, so that I had an cleaner install (e.g controls in front). But, that also takes some planning and scheming on your own (or by your amp tech). It's not plug-and-play: you need to understnad the circuitry before you jump in.

For what it's worth, the 18watt VVR mod is functionally equivalent to powerscaling, except that it does not change bias (cathode-biased amps like 18watts automatically change their bias). The magic of powerscaling is that it also automagically adjust the bias -- which is NOT what a variac does (despite the Harmony Central claims).

Thanks for the recommendations... I've been checking out the circuit changes needed for power scaling, both by London Power, and the VVR kits by Hall Amplification. I have no issues with putting in the power scaling, I understand the circuitry very well. But to your other point, my first plan was to put in the PPIMV, and I already have those parts, so I'll probably go ahead and do that first. Who knows, maybe I'll be happy with just that.
But I was very impressed with the youtube demo of power scaling.

[MattPete]

Heck, might as well put in the PPIMV first. That's what I did before I eventually installed powerscaling. Since the PPIMV acts as the drive control for when powerscaling, it was one less thing to worry about when I installed the kit.

Is there a VVR mod with bias-tracking (which is what London Power's powerscaling does)? I installed the VVR mod a year or so ago in my P1-extreme, but back then it only worked for cathode-biased amps (I adapted it from 18watt.com).

[RLee]

Originally Posted by MattPete

Heck, might as well put in the PPIMV first. That's what I did before I eventually installed powerscaling. Since the PPIMV acts as the drive control for when powerscaling, it was one less thing to worry about when I installed the kit.

Is there a VVR mod with bias-tracking (which is what London Power's powerscaling does)? I installed the VVR mod a year or so ago in my P1-extreme, but back then it only worked for cathode-biased amps (I adapted it from 18watt.com).

Yep they now have a kit for fixed-bias amps called the VVR3: http://www.hallamplification.com/main.html?src=/#2,2