Attenuator Rant & Myths!

[Gene Ballzz]

@JohnH & @Gene Ballzz : you should be proud of what you have done. When the internet was first invented this is the sort of things that people (and me!) hoped for it.

I had a look at the other thread, but only a few pages of it, and admire johnh’s engineering work, and Gene’s hands on application.

I just bought a DSL1CR. It is already very nice at low volumes, but I will soon try a volume box in the effects loop (cheap build). If that fails, or regardless of that, this attenuator build sounds exciting, even if I am not great with a soldering iron.

I have a question, and maybe John already replied on the other post - which I will read through the next days / weeks. Why the -7 dB reactive and the rest resistive? And would there be other higher attenuation reactive first step possible build?

My interest is apartment playing, so practical volumes are 65-75 dB (I know, that is very low), and I’d like to crunch the clean channel of the dsl1.

Once again, brilliant work on this. So kind of you!

By design, the reactive -7db stage is always on and active and it provides all the reactive function for all the rest of the stages! In other words, when that reactive -7db stage is in circuit, all the other stages are also reactive. @JohnH can explain it better, but generally -7db is the "sweet spot" in the maths for all the other stages to be in even increments.

Just Sayin'
Gene

 

[JohnH]

Hi @[email protected]

The job of the reactive part of a 'reactive' attenuator is to show the amp an impedance that is similar to that of a speaker, so that the amp can respond to it as if it was driving a speaker directly, even though the real speaker is far down-stream. So in our design, as Gene notes, it's stage 1 that has to be reactive since that is the only one connected to the amp. After that, we just sample a signal from it and gradually reduce it over a number of further stages, without changing it further. Resistors are best for that, and they absorb a controlled amount of the amps power until the level is reduced as needed.

 

[LoudStroud]

Are you located in the states? I'd love to have an experienced, gigging player do a side by side shootout comparison of the 50 watt JohnH and that Harley Benton PA-250! Maybe I could arrange to temporarily send you one for that purpose, if you have time and/or inclination. Given that , IIRC, you have two identical SV20H rigs, there couldn't be a better and more simple/convenient comparison! If you love the JohnH you could buy it, or simply send it back to me, all on my dime, of course.

Let Me Know?
Gene

Hey Gene. Sorry to just now be responding and I appreciate you extending that offer. I’d love to hear the JohnH attenuator. And would be cool to compare the two units, Although I wouldn’t be surprised at all if the John H design is higher quality sonically.

Unfortunately would not be able to A/B with my two SV20’s side by side, as that rig stays out with the band gear. However, I do have an SV20C here at the house I could run into a 212 cab with old greenbacks. Could properly record examples comparing the two attenuators at their equivalent dB cut settings.

It’ll be next month before I could consider doing it. Touch base in February? And yes, I’m stateside. Great idea! Thanks again for offering.

 

[K Dub]

@LoudStroud I would be interested in an A/B comparison through the 110 SV20C combo speaker as well.

 

[Gene Ballzz]

Hey Gene. Sorry to just now be responding and I appreciate you extending that offer. I’d love to hear the JohnH attenuator. And would be cool to compare the two units, Although I wouldn’t be surprised at all if the John H design is higher quality sonically.

Unfortunately would not be able to A/B with my two SV20’s side by side, as that rig stays out with the band gear. However, I do have an SV20C here at the house I could run into a 212 cab with old greenbacks. Could properly record examples comparing the two attenuators at their equivalent dB cut settings.

It’ll be next month before I could consider doing it. Touch base in February? And yes, I’m stateside. Great idea! Thanks again for offering.

That sounds great! It'll likely be next month before I can get an extra one finished that isn't earmarked for a new home! Along, about early February, I'll touch base by startig a "Conversation." At that point we can swap real emails, phone #s, send to address, etc.

Thanks Again,
Gene

 

[LoudStroud]

That sounds great! It'll likely be next month before I can get an extra one finished that isn't earmarked for a new home! Along, about early February, I'll touch base by startig a "Conversation." At that point we can swap real emails, phone #s, send to address, etc.

Thanks Again,
Gene

Sounds great Gene. Looking forward!
Peter

 

[Crunchifyable]

That's interesting about the air brake discussion. My own attenuator is based on the air brake and has only three components (two 25 ohm resistors and a rheostat acting as a volume control).

And that's basically my own issue if I use my attenuator the amp will always see a 25 ohm load typically.

Is there tone loss? Probably. That's also probably indistinguishable from volume loss.

My own conclusion is that if I'm using an attenuator it means the amp is designed wrong or I'm using the amp wrong.

In fact I believe that adding or modifying a master volume would have better results than an attenuator, because most of the sound is coming from the preamplifier section and if the power amp is distorting it's going to sound bad anyway.

So if the sweet spot is like noon on a clean channel or non master volume amp, sticking something in the effects loop to lower the volume or just using the master volume if the amp has one does the job better than an attenuator.

The only amp I think I have that really needs it is my 6262 (5150 II) that has loud lead channel. But sticking an attenuator on an amp that's only on level one always seems like wrong on some level.

 

[scozz]

…….because most of the sound is coming from the preamplifier section and if the power amp is distorting it's going to sound bad anyway……..

Yeah, most amps these day get the majority of their drive from the preamp section, but not all. I don’t understand your opinion that power amp drive, distortion, “always sounds bad”?

Many amps sound great overdriving the power section, some Marshalls and some Fenders come to mind immediately. Maybe I misunderstood you though?

I get the best results, to my ears, using something close to a 50/50 mix of the master volume drive and preamp drive with my SC20h.

 

[TXOldRedRocker]

Yeah, most amps these day get the majority of their drive from the preamp section, but not all. I don’t understand your opinion that power amp drive, distortion, “always sounds bad”?

Many amps sound great overdriving the power section, some Marshalls and some Fenders come to mind immediately. Maybe I misunderstood you though?

I get the best results, to my ears, using something close to a 50/50 mix of the master volume drive and preamp drive with my SC20h.

Agree scozz.

I don't play at super loud volumes.

On a MV amp, I turn up the Preamp to taste and then turn up the volume to my desired level. Sounds great!

On an attenuated amp, non-MV, crank up the Volume (knob) to taste. Sounds historic!

On an attenuated amp, with MV, crank up the Volume (knob) to taste, then turn Preamp for best possible tone. Sounds famously historic!

 

[scozz]

Agree scozz.

I don't play at super loud volumes.

On a MV amp, I turn up the Preamp to taste and then turn up the volume to my desired level. Sounds great!

On an attenuated amp, non-MV, crank up the Volume (knob) to taste. Sounds historic!

On an attenuated amp, with MV, crank up the Volume (knob) to taste, then turn Preamp for best possible tone. Sounds famously historic!

Absolutely Tex, we’re on the same page bro!

 

[Crunchifyable]

Yeah, most amps these day get the majority of their drive from the preamp section, but not all. I don’t understand your opinion that power amp drive, distortion, “always sounds bad”?

Many amps sound great overdriving the power section, some Marshalls and some Fenders come to mind immediately. Maybe I misunderstood you though?

I get the best results, to my ears, using something close to a 50/50 mix of the master volume drive and preamp drive with my SC20h.

I guess I just meant in my opinion. To me power amp distortion sounds kinda like a dull fuzz pedal and I'm just not a fan. Getting a little compression and high end roll off by getting medium volume like you do with yours isn't necessary a bad thing to my ears. Just maybe hard on the amp and tube set?

Having gone the attenuator route before to see what it was like, I think I came out with the impression that a precise master volume works best for me, with a tube screamer and EQ in front to shape the sound if needed.

 

[scozz]

I guess I just meant in my opinion. To me power amp distortion sounds kinda like a dull fuzz pedal and I'm just not a fan. Getting a little compression and high end roll off by getting medium volume like you do with yours isn't necessary a bad thing to my ears. Just maybe hard on the amp and tube set?

Having gone the attenuator route before to see what it was like, I think I came out with the impression that a precise master volume works best for me, with a tube screamer and EQ in front to shape the sound if needed.

To my ears some of the best tones come from pushing the master in single channel 800 amps. It’s all subjective though isn’t it?

I play pretty loud when my wife’s not home, master around 5 or 6, and the gain around the same, maybe a little higher, in the 20 watt mode, (SC20), It’s pretty loud.

I have no worries about the tubes failing, running a Marshall that way, especially the Marshall Studios. They all have 2 - el34’s for a 20 watt amp soooo,…

Yeah, under normal conditions diming your amp all the time will likely shorten the lifespan of the power tubes.

Enjoy the ride bro, there are many things in life that are completely enjoyable, playing guitar is one of them!

 

[andtheUgly]

"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!"

This is so true. Prior to building my JohnH M2, I have built several copies of (usually vintage) pedals. I try to make them as close as possible to the originals in terms of components and external appearance, although for various reasons usually do my pcb layouts. I often get compliments and "can you make me one?", sadly I don't have the time or enthusiasm to do this for someone else, though I'll give as much advice as they want. While the components are usually cheap (but never cheaper than a manufacturer could bulk buy), the time it takes to make a good build is crippling. Even if I am offered a "good rate" for my time, once I explain how long it may take and therefore the potential cost, it is almost always better to buy a new or second hand unit.

What Gene offers/does is fantastic.