Attenuator Rant & Myths!

[Gene Ballzz]

First, let me say that this is intended as a discussion about passive attenuators, especially in the affordable “sub - $500” price range. While the active, re-amping units, such as the Fryette Power Station, BadCat Unleash, WAZA TAE, etc, etc, are wonderful devices, with many great features, they simply don’t fall into the intended discussion category and are not really attenuators, even if they are marketed as such.

Also, please understand that I really have no dog in this fight, other than being a very old guitarist who has been chasing a rather elusive means of taming the volume of amps that are simply too loud, when cranked to their tonal “sweet spot” while still retaining full range tonal characteristics, dynamic response and feel. While I do actually build “one off” attenuators for some folks, the small fees I charge (less than $5 an hour for my time) do not really qualify as a business. I simply want to share the liberation obtained through the use of a really great and simple, passive attenuator that won’t break most guitarists’ bank accounts. I also strongly encourage the DIY approach and am willing to actively assist with tips, diagrams, etc, for those who have at least some experience with the use of a drill, simple hand tools and soldering equipment. The cost for materials for DIY is between $100 & $150, depending on the sourcing, and a little less than $300 for me to assemble a simple one for you. Trust me when I say that putting together a cosmetically acceptable unit, while fairly simple and easy, is VERY time consuming, especially for a one off, first time build! If even the simplest of these units were produced commercially, the price would need to end up at $500 or more!

Bottom line here is that when it comes to “affordable” passive attenuators, there is the @JohnH design and then all the others! While MOST commercially available attenuators have proven themselves to be safe for use, within their stated design and use limits, sonically the @JohnH design is far superior in nearly every way, and there are many features, bells and whistles that can be fairly easily added to the build, if desired. Some of these features, I won’t do, as I’ve not found standards for them that I’m comfortable with, or implementing them becomes too complicated and/or more time consumptive than I want to deal with.

Now on to the myth that “All Attenuators Suck Tone!” Yes, although most attenuators will knock volume down, while allowing an amp to be cranked to its “sweet spot” almost all of them do indeed suck tone, response and feel as the volume goes down. How much these losses are perceived has a lot to do with how much of your targeted tone and sound is achieved by the direct interaction of a guitar plugged generally direct into an amp, as opposed to being created through multiple stomp/pedal/foot/thingies! And unfortunately, once the volume goes below a certain point, the capabilities of harmonic feedback become reduced, with any volume reduction method. With that said, the @JohnH design retains more of what we all want than any other unit out there!

Here's a link to the thread detailing DIY building of the @JohnH attenuator:

Simple Attenuators - Design And Testing

Background Passive attenuators are wired between the amp output and the speakers. Their function is to absorb most of the output power of the amp, feeding a smaller amount to the speaker itself. This allows the amp output stage to run at higher power, letting the glorious tone of a good valve...

www.marshallforum.com

Contact me privately for any assistance!

Rant Over!
Gene

 

[Dave_11]

Building one of these has been on my "want to do" list for several months, but one thing holding me back is wading through the above linked thread, trying to figure out which build I need for my Ori20, which parts I need, etc. Maybe that's laziness on my part, but I think it would be great if there was a resource that listed appropriate builds/attenuation levels for various Marshall amps, or various amp wattages. It would also be great to have a parts/supplier list for these builds. One pedal website has links to Excel sheets with Mouser parts numbers for their builds. I don't know if something like this would be possible for the attenuator, or if you have to source from various suppliers. Or maybe all this already exists in the Simple Attenuator thread and I've just been to lazy to look it up...

 

[purpleplexi]

Torn between getting Gene to make me one, doing it myself, doing nothing or picking up the tone king iron man that I've just been offered at a similar price.
So difficult.

 

[paul-e-mann]

Torn between getting Gene to make me one, doing it myself, doing nothing or picking up the tone king iron man that I've just been offered at a similar price.
So difficult.

I was in the same spot, the quickest easiest solution was get a good deal on a power brake which I have found to sound great in my opinion.

 

[Gene Ballzz]

Building one of these has been on my "want to do" list for several months, but one thing holding me back is wading through the above linked thread, trying to figure out which build I need for my Ori20, which parts I need, etc. Maybe that's laziness on my part, but I think it would be great if there was a resource that listed appropriate builds/attenuation levels for various Marshall amps, or various amp wattages. It would also be great to have a parts/supplier list for these builds. One pedal website has links to Excel sheets with Mouser parts numbers for their builds. I don't know if something like this would be possible for the attenuator, or if you have to source from various suppliers. Or maybe all this already exists in the Simple Attenuator thread and I've just been to lazy to look it up...

@Dave_11 ,
I hear ya about that labyrith of a thread! For your use, I'd recommend a simple M2 build. All you really need to determine is whether to build it as a "native" 8Ω or 16Ω unit, depending on the speakers you normally use and what else you may want in the future! While there are many additional bells and whistles that you COULD incorporate, it is my most honest opinion that simple is better! Even for a line out, using a unit like an K&K RedBox (or many other similar units) provides more flexibility and they've already worked out many of the more pleasing compensations, etc.

Feel free to contact me privately for drilling templates, recommended parts sources/lists etc. Well worth the time, $$$ and effort!

Happy Attenuatin'
Gene

 

[Dave_11]

@Dave_11 ,
I hear ya about that labyrith of a thread! For your use, I'd recommend a simple M2 build. All you really need to determine is whether to build it as a "native" 8Ω or 16Ω unit, depending on the speakers you normally use and what else you may want in the future! While there are many additional bells and whistles that you COULD incorporate, it is my most honest opinion that simple is better! Even for a line out, using a unit like an K&K RedBox (or many other similar units) provides more flexibility and they've already worked out many of the more pleasing compensations, etc.

Feel free to contact me privately for drilling templates, recommended parts sources/lists etc. Well worth the time, $$$ and effort!

Happy Attenuatin'
Gene

Thanks for the input Gene. I always admire your friendliness and willingness to help people on this board! I'll pm for the parts lists, etc.

 

[tmingle]

The "Tone Suck" that everyone seems to complain about is 95% due to the Fletcher/Munson effect.
I recorded a loop & tested my JOHNH at 4 different attenuation levels & normalized the clips in Reaper. I cannot hear a difference when played back.
I highly recommend this circuit & would advise building a 100 watt version as a buffer. Overkill is good with expensive tube amp gear!

 

[JohnH]

I'll chip in here too, and obviously, I'm not entirely unbiased! But I really think that one of our M2's or its variants, if considered purely for what it is designed to do, is an attenuator that cannot be beaten at any price. And one built the way Gene builds them is the gold standard for construction.



How can I say that with an honest face? The starting point is to understand what actually it is designed to do. That is, when comparing pure tone independent of volume, playing a tube amp through it into a guitar cab, the sound at every attenuation level is identical to that at full volume, and this is demonstrated by consistent recordings at each level, and then all normalized to the same level so that they can be compared. In this test, there should be no audible difference and negligible visible difference in measured response traces. This applies not only to simple frequency responses, but also to the way tones decay dynamically and respond to the amp at different guitar intensities of playing.



IMO the standard for comparison is therefore not another attenuator, but the full sound of the real unattenuated amp and speaker. Our design achieves this and its been demonstrated now in dozens of builds and several measured tests using different rigs with different amps (eg as described by @tmingle above and recently by @rowandg ). So if that is what an attenuator should do (and that's just my assumption about what it should do), then no other design can beat it because that's what our design already does! So in that statement, its covering not only other passive attenuators but also the expensive active re-amping ones too.



Obviously, the big name units may have more features and these may make them very useful units for many purposes. We can tackle some of them with ours, but Im only talking above about this core function of attenuating an amp to feed a guitar speaker.



When you look at other designs, and read reviews about them, we see that they mostly seem to have some inherent issues that need a workaround. Many of them are reported as OK for a few db, or they get fizzy or dull as you turn down. They may have switches to try to compensate, and describe them in terms of allowing for FM effects, or the effects of the room, but I believe really these tweaks are needed to address issues with the circuits. We don't need those, because the issues dont occur. This is achieved by the switching system which once its understood, allows each setting to be optimized. It also allows simple, inexpensive and reliable toggles to be used. It's at the expense of not having a continuous sweep of settings though.

 

[tmingle]

I would like to mention here that my test amp was a DSL40C, which has been well designed from the start to perform well at low volume settings. It gets most of its distortion from the pre-amp tubes. I have connected the FX out to an interface & used IR's with good results. I do believe that the output tubes for this amp do need a certain amount of current flowing thru for a fuller sound though. I find that any volume below 2 on either channel to be weaker sounding, with the sweet spot between 4 & 5. To my ears, volume settings above 6.5 don't really get much louder, just more compressed. IMO, the JohnH attenuator set up for -7db/14db is the perfect companion for the original 40C. I haven't tried it with the 40CR yet because the CR has twin master volumes & the low power switch works much better than the original 40C IMO.

 

[Ufoscorpion]

The "Tone Suck" that everyone seems to complain about is 95% due to the Fletcher/Munson effect.
I recorded a loop & tested my JOHNH at 4 different attenuation levels & normalized the clips in Reaper. I cannot hear a difference when played back.
I highly recommend this circuit & would advise building a 100 watt version as a buffer. Overkill is good with expensive tube amp gear!

The biggest factor that most tend to not consider or understand that cannot be changed it’s simply down to how our hearing works and only compensated for in some way .

 

[Gene Ballzz]

The biggest factor that most tend to not consider or understand that cannot be changed it’s simply down to how our hearing works and only compensated for in some way .

While you are course, absolutely correct, there is another often not considered factor. Many of us need and use an attenuator for controlling stage volume, to keep venue owners happy, and then we put a mic on the speaker to evenly distribute (mix) it throughout the room. If that mic is placed on an amp that has had it's volume squashed and tone/response compromised by a crappy attenuator, that is what the mic "hears!" Now that mic is not subject to the way our hearing works, Fletcher Munson Curve, etc, so when it is placed on an amp with a great sounding, full tonal range/dynamic response @JohnH attenuator, THAT is what the mic hears! Yes, the "on stage" sound may be a bit compromised, but what goes to and through the PA is stellar! This is where the differences really show up and shine!
Just Noticin'
Gene

 

[LoudStroud]

Cool to learn about this @JohnH DIY and will check it out.

Otherwise, I have tried and used so many attenuators over the years and have two current go-to’s. The re-amping Fryette Power Station and the passive Harley Benton PA-250, the latter you need to know about. This model has been available for just over a year and still carries the amazingly reasonable price tag of $133+shipping. Have only found available thru Thomann online store out of Germany. But even shipped totaled under $175.

Works at 8 or 16 ohms, has all of the useful attenuation features, but most importantly, sounds and feels excellent…as far as passive attenuators go. Like all passives, there’s a drop in high-end as you decrease to bedroom volumes. But at stage level, almost indiscernible.

The biggest discrepancy I’ve had with any attenuator is how it affects a clean signal. Many attenuators I’ve tried have not been capable of translating that stellar clean sound of a Marshall Super Lead, Hiwatt or Fender without introducing a slight fizzy crunchy or crackly artifact across the top of the signal. The Tone King models and the Rock Crusher both have this issue (to my ears at least), among others. Cranked distortion masks it. But as soon as you try for a clean tone it’s irritably apparent. Both of these units don’t have that issue.

Also deLisle’s attentuator design that he incorporates into his multi/amp switchers are really clean.

But for bang for the buck, the Harley Benton is unbeatable, except for possibly the @JohnH design, I’m assuming, as you are all describing.

Here’s the link in Thomann store:
https://www.thomannmusic.com/harley_benton_pa_250_power_attenuator.htm

 

[JohnH]

Here's Steven Anthony comparing a Harley-Benton PA-250 to a Fyrette Power Station



He notes that he's focusing on moderate attenuations (9dB is mentioned) and seems to know what he is looking for. Much as he likes the Fryette, he concluded that the HB suits him better for his purposes. It does indeed seem like a step up from the most basic designs. Great how it has fan cooling.

It reckon the Harley Benton is a resistive design (or else surely a copywriter would have taken the opportunity to call it reactive!). the existence of the knob for below -15dB suggest an L-pad. Id expect this is responsible for any low-volume tone suck, which is due to resistive damping of the speaker in these circuits. I don't think this needs to be treated as inevitable in passive designs - but it is inherent with L-pads.

But , then he comes back with a further vid, this time bringing in an Ironman 2:



The HB wasnt kept and he notes (at about 1.30) how it was changing his sound, 'cleaning it up'. Thats consistent with it being resistive. There were also some issues with the LED.

He likes the Ironman much better, and notes that it gets brighter as you turn down.

We also heard that in Johan Segeborns vid on the Ironman. It has a compensation switch targetted at this issue.

 

[Gene Ballzz]

@JohnH ,
It would be great to get one of your M2 units to either or both of these guys for a shootout!
Just Thinkin'
Gene

 

[tmingle]

Here's Steven Anthony comparing a Harley-Benton PA-250 to a Fyrette Power Station



He notes that he's focusing on moderate attenuations (9dB is mentioned) and seems to know what he is looking for. Much as he likes the Fryette, he concluded that the HB suits him better for his purposes. It does indeed seem like a step up from the most basic designs. Great how it has fan cooling.

It reckon the Harley Benton is a resistive design (or else surely a copywriter would have taken the opportunity to call it reactive!). the existence of the knob for below -15dB suggest an L-pad. Id expect this is responsible for any low-volume tone suck, which is due to resistive damping of the speaker in these circuits. I don't think this needs to be treated as inevitable in passive designs - but it is inherent with L-pads.

But , then he comes back with a further vid, this time bringing in an Ironman 2:



The HB wasnt kept and he notes (at about 1.30) how it was changing his sound, 'cleaning it up'. Thats consistent with it being resistive. There were also some issues with the LED.

He likes the Ironman much better, and notes that it gets brighter as you turn down.

We also heard that in Johan Segeborns vid on the Ironman. It has a compensation switch targetted at this issue.

I'd like to see what Johan Segeborn would do with 1 of your designs. This guy seems to embrace all tonal differences as enhancements to his playing. If a piece of gear does not change the way you play & sound, why would you use it? The only "BAD" tone I've ever heard from Johan was a modeler(AXE-FX?) into a Headrush speaker.

 

[tschrama]

First of all: I applaud the efforts of JohnH. And it is great for the DIY community that he made his efforts public. But all passive attenuator try to solve a multiple tasks which are impossible to achieve in a passive device and his design is just like any other:

1] Provide an equivalent complex load to the tube power amp. This is to ensure that the clipping behavior of the output stage stays unaltered. Easely done with a LC-resonance, allthough JohnH decided to skip this in his design.

2] Provide the speaker with a, constant fraction across frequency, of the output voltage that the power amp delivers to the attenuator load. This is what JohnH design does pretty good, but this is no challinging task. The attenuation graphs JohnH show us are relative to -7dB. I think this is useless as any tonal change happens between the bypass and -7dB setting. After -7dB, there is just a passive, resistive ladder attenuator which due to it's resistive nature can only be tonal neutral.

3] and achieve nr 2] with the same damping factor, or complex output impedance, as the power amp would, realizing that the openloop gain of the power amp collapses during clipping and thus the complex output impedance of the power amp changes during clipping. This is practically impossible whithout using an actual tube power amp.

Thus all passive attenuator has fundamental flaws that users will experince as "tonesuck" .. the only sollution is to device the 3 task and use active elements to achieve them, e.g. reamping, maybe with IRs, or even a reamping tube amp.

 

[Gene Ballzz]

@tschrama

Please note that even in the very first post of the VERY lengthy @JohnH attenuator thread, the attenuated signal is compared to the unattenuated signal, NOT relative to the -7db signal. While there may well be some graphs throughout the thread that compare to the -7db (or other) signal, the vast majority of analyses provided by JohnH and many others, of various aspects compare to that unattenuated signal.



I have tried nearly every passive attenuator design, from a majority of the manufacturers since the ALTAIR was released in the mid '70s. While your technical treatise may be correct, from a hands on, real world guitarist's perspective, the JohnH design retains much more of the tone and dynamic feel and response thoughout the attenuation range than any other "PASSIVE" unit I've tried. Is it perfect? Certainly not, but choosing what compromises are acceptable and which ones are not (for any individual player) is part of the game of guitarists getting what they want from their rigs. Perfection for many may well be an unattenuated JTM 45/100 or 1959 through a full stack of Greenbacks, cranked to it's sweetest spot, but being able to use such a rig is simply not realistic for most players. Getting as close as we can and retaining the aspects that are most important for each musician is the main goal here! This attenuator design provides more of that, in spades, compared to all others!

This all begs the question: "Have you ever plugged into a JohnH unit and/or physically/sonically compared it to other passive units?" If not, your comments, while likely valid, are mostly well informed armchair suppositions!

Please also understand that I appreciate and respect your technical knowledge, but real world results do not always completely agree with technical analyses.

Just My ,
Gene

 

[tschrama]

Those graphs you quote are not from sound real recordings. My guess is they are calculated, 'predicted' , from the impedeance netwerk. If indeed they are calculated, instead of recorded from a overdriven tube power amp, they provide a false sense of accuracy. They cerntainly fooled you....

The relative to -7dB attenuation grahs are in the same first post of the thread about the design.

For the record, it is obvious that many people like this attenuator design. And that is great! But when trying to analyse its performance, and trying to explain why this design might be better than others.. I feel the analysis provided and the explanaition from JohnH so far is lacking. I explained this to JohnH is his thread some years ago.

Sometimes when I feel up to it, I try to provide the readers with some objective analysis.

And no, I haven't build this attenuator. But again, it is not fundamentally different from other passive attenuators, and suffers from the same fundamental shortcommings.


Cheers... going back to my armchair now.

 

[LargeBoxSmallBox]

The "Tone Suck" that everyone seems to complain about is 95% due to the Fletcher/Munson effect.
I recorded a loop & tested my JOHNH at 4 different attenuation levels & normalized the clips in Reaper. I cannot hear a difference when played back.
I highly recommend this circuit & would advise building a 100 watt version as a buffer. Overkill is good with expensive tube amp gear!

I would have to disagree with this statement, based on my experience with many attenuators. My friends and I have done MUCH testing, and all attenuators are not created equal. To be fair, I have never tried the JohnH attenuator, so I cannot speak to that. The raves it gets make me want to try one someday. But the most transparent attenuator I have used is the Z Air Brake that was licensed from Trainwreck. You just didn't lose any tone from that thing. I would still have mine, except I got the Fryette Power Station, which also does not suck any tone (although, I know, it is not strictly an attenuator so not part of this discussion). But the Fletcher/Munson curve should apply to that unit, too, if all that is true, but tone is not sucked by that unit at lower volumes either. But, yes, the Z Air Brake is amazingly transparent. The only issue is you can't get super low volume with it. But a great unit!

 

[tmingle]

Dirty

Dirty normalized

Clean

Clean normalized

I posted these to Soundcloud a long time ago. I sure can't hear much difference. The test was done with a DSL40C with an Egnater Elite 80. Recorded into a Scarlett using an SM57. I did not fiddle with mic positioning because the point was to see if I could hear a difference. I recorded both clips into the looper function on my TC Flashback delay pedal. I did use an MXR 10 band in the loop of the 40C. Once the tones were dialed in no settings were changed. I merely played the loops & changed switches on the John H unit. I have no need to consider any other attenuators & If I need another for some reason, I will build another 1 of these. I elected to install oversize resistors to allow use of a 100W amp if needed.