Attenuator roundup?

TimmyO

Guys, I was talking to someone today and the subject of attenuators came up - he'd heard the sometimes popular opinion that the Marshall Powerbrake was to be avoided, whereas I recall something from @ICBM which covered what the PB is a very good option for Marshall amps, whereas some other (Weber, Hotplate ? ) types were a poor option for certain types of amp.

I was wondering if ICM would mind revisiting the topic in the open forum so that we have some reference material to bookmark ? 

Other please also chip in your experiences.

For my part I've had good results with a PB100 and a Torpedo Reload (both with a JCM800) 

Tim 

Fatfingers

I built an Airbrake clone that worked very well with a JCM800 I had.

ICBM

I haven't got much experience with most of the newer models, but of the older ones:

Marshall Powerbrake - excellent, works very well with Marshall-style amps and other 'British' amps which tend to like a high mismatch rather than low. 8 or 16-ohm only.

THD Hotplate - excellent, works very well with Fender and Mesa-style amps which tend to like a low mismatch rather than high. Can be stressful for Marshalls.

(These are both because their impedance curves diverge from a real speaker in those directions.)

Airbrake - purely resistive, seems the best with amps with no negative Feedback (eg Vox, Fender Tweed Deluxe). Expensive for what it is though - the Brake Lite even more so, and the claimed power ratings of both would worry me a bit, especially the 45W for the Lite.

Weber Mass - again rather optimistic power ratings. They sound OK with most amps but not great with any I've tried, and the build quality is a bit questionable. The claim that they use a speaker motor is only partially true, most of the load is still resistive.

Sequis Motherload - excellent, very high quality and good-sounding with any amp I tried it with, but expensive unless you need the speaker-emulating features.

Ultimate Attenuator - avoid. It's actually a dummy load and solid-state reamp system rather than an attenuator, the dummy load is far too high a safe resistance for anything other than a 16-ohm amp, and the build quality is so poor it would not pass EU safety regulations.

Can't think of any others I've tried at the moment...

ThePrettyDamned

I've had great success of a simple l pad on a low watt vox style amp - nothing complicated needed there it seems. 

HHwarner

Iv used both Marshall PB and THD Hotplate with my Marshall amps. The PB wins hands down on my Marshall. Its great and is the only one I use now. Iv gigged with one for probably 2-3 gigs a month for the past 6 years with no problems at all

p90fool

The Jet City Jettenuator works very well with EL84 Jet City amps, and with tweed Champ or Princeton types.

It kills the sparkle in B/F or S/F Princetons or Deluxes, which can work ok with some overdrive pedals, but if you want it for pure amp overdrive I'd look elsewhere. 

My experience with the Marshall Power brake is the same as ICBM's. 

ecc83

I have been thinking about power soaks and the buggering bit of building them is the multiple resistor chain needed to get various attenuations. A few years ago I solved this problem from at least an "engineering" point of view* by the use of a 100V line speaker transformer. This was a 400W rated load box but one that incorporated a (fairly crude) power meter and a speaker output that could be turned to zero.

You still need a Big Mother power resistor to properly load the amp (but would be what, 10% higher than nominal for best sound IC?) but then this is connected to the primary of the 100V traff.

Some numbers: A 30W traff with a 16R load has a stepdown ratio of 4.56:1 and so if you connected that to a (loaded!) 100W amp's 16R tap it would put a ball park 4.8W into a 16R speaker (for 8.77 volts) So you have rather painlessly produced a power drop of  around 13dB without faffing about calculating a resistor chain.

The box was used for some two years on valve amps from 5 to 200watts and never caused a problem (except the 200watter kept burning out the VC pot!) . 100V line traffs are pretty cheap considering the hassle they save you.

*What peeps with better ears than mine thought of the attenuated SOUND I cannot say!

Like to hear the views of the cognoscenti.

Dave.

ICBM

You have just redesigned the Marshall Powerbrake .

That's essentially how it works - a large multi-tap auto-transformer driving a single load resistor. It's unique among commercial attenuators in using this approach as far as I know.

The inductance of the transformer also gives it a reasonable approximation of a speaker impedance curve, although it rises a bit too high at high frequencies.

Exorcist

I was really hesitant about trying an attenuator, if you believe half of what you read you would think they turn your sound to sh*t, and are only good for turning a loud amp down a few DB's. But I shelled out for a jettenuator and its been great. Takes by Fuchs down to home/bedroom levels without killing the tone, and on a few other low wattage amps (tweaker and special 6 ultra) I can crank them to the sweeter levels and it still sounds pretty good to me. Never used one in anger though, only at home. 

ICBM

Exorcist said:

I was really hesitant about trying an attenuator, if you believe half of what you read you would think they turn your sound to sh*t, and are only good for turning a loud amp down a few DB's. But I shelled out for a jettenuator and its been great. Takes by Fuchs down to home/bedroom levels without killing the tone, and on a few other low wattage amps (tweaker and special 6 ultra) I can crank them to the sweeter levels and it still sounds pretty good to me.

I don't understand the hatred for them either. It's true that nothing quite sounds like a cranked amp with the speakers working hard, but attenuation can get you a lot of it at much more sensible volumes.

I think there are several things that a lot of people seem to misunderstand -

First, they will often try the first attenuator they come across with their amp, regardless of whether it's a good combination or not, and if it doesn't sound perfect they will then proclaim that attenuators kill tone and never use one again. This is about as logical as trying one overdrive pedal, finding it doesn't work very well with your particular amp and then saying that all overdrive pedals sound crap.

Second, there's an idea that you can set your amp up for your full-volume stage sound, then turn the attenuator down and it will sound the same but quieter. This won't work - at least partly because your ears don't hear EQ the same at different volumes - what you need to do is set the attenuator to roughly the right level *first*, then dial the amp in for that volume - which might be quite different settings. There are some attenuators which need less amp adjustment than others, but they all do.

Third, the idea that you need to crank the amp right up to get the full power stage distortion, and then attenuate it. If the amp has a master volume this isn't true - you rarely get the best sound that way, it's usually much better to run the amp less hard so neither the attenuator or the master volume is doing all the work - you can often find a 'sweet spot' that way which is better *and* quieter than using either alone. Most amps - even without master volumes - generate a mixture of preamp and power amp distortion anyway, it isn't true that a cranked amp is pure power stage distortion.

It is true that they can often sound a bit strangled or flat at very low settings - this is probably because they damp the speaker movement too heavily, not because they kill the tone of the amp. If you're using high-powered speakers - the ones you need for a big amp turned up loud - it tends to be worse because those speakers tend to need pushing a bit more at very low power inputs anyway.

Lebarque

Swart Night Light was better than the Dr Z Brake Lite for my old PRRI. Great for small combos. Still got it somewhere if anyone wants it.

sweepy

I never really liked the Tone King Iron Man system, on the Sky King I found it fizzy and a real tone suck. The Hot Plate did suit my old Boogies perfectly, so as already mentioned previously it's definitely a case of "Horses for Courses"

pintspiller

My Powerbrake is great with my JMP and I think is ok with Sound City (been a while).

crunchman

I know @ICBM doesn't like it but I prefer Power Scaling in the amp to reduce the voltage on the power valves.  My experience is limited compared with his, but on the few I've tried I genuinely prefer the sound.

Given the cost of a lot of the high end attenuators it could actually a cheaper option.  You also don't have to faff around connecting up the attenuator.

ICBM

crunchman said:

I know @ICBM doesn't like it but I prefer Power Scaling in the amp to reduce the voltage on the power valves.  My experience is limited compared with his, but on the few I've tried I genuinely prefer the sound.

Given the cost of a lot of the high end attenuators it could actually a cheaper option.  You also don't have to faff around connecting up the attenuator.

But you have to faff around heavily modding the amp! Unless you buy one with it as stock, of course… but you can only use it on that one amp.

Fair enough if you prefer the sound though.

I wouldn't assume you've played more than I have with it, I don't think I've tried it on more than about three or four amps. It's a shame because it's a much more elegant solution than wasting most of the power output of the amp, but I just but I really haven't liked it on any amp I've heard it on. I'd much rather have a normal master volume too.

olafgarten

ICBM said:

crunchman said:

I know @ICBM doesn't like it but I prefer Power Scaling in the amp to reduce the voltage on the power valves.  My experience is limited compared with his, but on the few I've tried I genuinely prefer the sound.

Given the cost of a lot of the high end attenuators it could actually a cheaper option.  You also don't have to faff around connecting up the attenuator.

But you have to faff around heavily modding the amp! Unless you buy one with it as stock, of course… but you can only use it on that one amp.

Fair enough if you prefer the sound though.

I wouldn't assume you've played more than I have with it, I don't think I've tried it on more than about three or four amps. It's a shame because it's a much more elegant solution than wasting most of the power output of the amp, but I just but I really haven't liked it on any amp I've heard it on. I'd much rather have a normal master volume too.

I've found Power Scaling to work very well on Tweed Deluxes, it sounded better than a Hotplate except at very low volumes, where you could talk over it. At those volumes the hotplate was closer to the fully cranked sound. 

Dodge

+1 on the Jettenuator (or Harley Benton version).  It's purely resistive but I've had great results with my old AC30's.  It drops volume even on zero, but it works great for knocking off a bit more to a point.

I've had two Powerbrakes (liked them - only tried with Marshalls), I also like the Marshall SE100 too which was limited in terms of it's attenuation (presets) and I've had MiniMASS 50's which I also quite liked (used with Cornell's and my Superbaby.  I definitely echo @ICBM 's comments about build quality though, they're average at best.  Both of mine had the power resistors rattling around in the chassis when they arrived, and the speaker motor was so tiny.  I've also had some time with the Hotplate which I wasn't overly fussed about but it wasn't bad.  That was with the Cornell's too.

I think people expect too much from attenuators - it doesn't matter what you've got, if you expect the same tone cranked at bedroom volumes you'll be sorely disappointed.  After a point they don't work the speakers enough - that's where other solutions are preferable (i.e. modelling, or my preferred solution is a reative load box and impulses, reamped through studio monitors which could easily be a full range amp / speaker).

crunchman

olafgarten said:

ICBM said:

crunchman said:

I know @ICBM doesn't like it but I prefer Power Scaling in the amp to reduce the voltage on the power valves.  My experience is limited compared with his, but on the few I've tried I genuinely prefer the sound.

Given the cost of a lot of the high end attenuators it could actually a cheaper option.  You also don't have to faff around connecting up the attenuator.

But you have to faff around heavily modding the amp! Unless you buy one with it as stock, of course… but you can only use it on that one amp.

Fair enough if you prefer the sound though.

I wouldn't assume you've played more than I have with it, I don't think I've tried it on more than about three or four amps. It's a shame because it's a much more elegant solution than wasting most of the power output of the amp, but I just but I really haven't liked it on any amp I've heard it on. I'd much rather have a normal master volume too.

I've found Power Scaling to work very well on Tweed Deluxes, it sounded better than a Hotplate except at very low volumes, where you could talk over it. At those volumes the hotplate was closer to the fully cranked sound. 

I've got it on a Lazy J so it's close to a Tweed Deluxe.

I've heard it on one or two other amps as well.  The first time I heard a version of it was on a 65 Amps amp of some description - can't remember which model.  It sounded great on that.

ecc83

ICBM said:

You have just redesigned the Marshall Powerbrake .

Don't think so IC? First off, my idea is not an autotransformer, it has primary and secondary windings*. Then the load goes BEFORE the traff and the latter merely acts as a voltage step down device, i.e. a transformer! This gets around the hassle of a resistive attenuator chain but you would need to feed something like an L pad for a decent attenuated power range. For my application I did not need this and so just used a 5W pot.

It is tempting to assume "wound component therefore inductance like a speaker" ? It ain't necessarily so, A properly terminated transformer does not "look" like an inductance (well bit of leakage inductance) and merely reflects the impedances in the circuit. I will concede that the transformer is NOT being used for its originally intended role so yes, might be a bit more "L" about than theory predicts! This could easily be tamed with some capacitors or a Zobel network. A field ripe for the experimenter I would suggest?

*This gives galvanic isolation and so makes such a soak ideal for recording purposes where earth loops can be a pain.

Dave.

ICBM

Interesting... in that case I think that's a unique approach that hasn't been tried before.

TimmyO

Let's hope there's nobody who works at Behringer reading this ;-) Get it patented quick