Simple Attenuators - Design And Testing

[EC Strat]

I'm planning to build a 100W M2, so I would like to know if I should give it a try to the Amphenol Jacks or stick with Cliff UK.

I bought some Amphenol jacks from Tubedepot with solder lugs along with some tubes, back in november. But I think those jacks from Mouser "532-ACJS-PHOP" are Amphenol with pins for pcb mounting.
TubeDepot never sent them to me due to tubes shortage. I had to cancel the tubes so they could ship me the jacks alone (bad experience). I'm still waiting (overseas shipping).

What jacks are tougher, Amphenol or Cliff UK??
According to datasheets, Amphenol hold up to 10A and +1.000 cycles, while Cliff UK hold up to 5A and +10.000 cycles, but I don't know if datasheets are trustworthy when comparing 2 different brands.

thank you for linking those items - saved me a ton of time

 

[Gene Ballzz]

Yeah, the Amphenol are at least a sturdy/robust as the CLIFF UK, but you probably don't want to deal with the added hassle of using the PCB mount units. A good source for switches and jacks:

https://www.tubesandmore.com

And FWIW, knowing what part of the planet yer at can help with sourcing suggestions!

Best To Ya,
Gene

 

[EC Strat]

Yeah, the Amphenol are at least a sturdy/robust as the CLIFF UK, but you probably don't want to deal with the added hassle of using the PCB mount units. A good source for switches and jacks:

https://www.tubesandmore.com

And FWIW, knowing what part of the planet yer at can help with sourcing suggestions!

Best To Ya,
Gene

Oh sorry - I’m in the USA

 

[donwagar]

I don't know if this was mentioned, if I recall correctly, you need stereo (TRS) jacks for the footswitch. I just order all of them as TRS.

Edit: I looked back, yes John did mention this.

 

[Paul L Ewing]

I wouldn't even think about making anything for an attenuator since a small error or something breaking down can toast your amp. Any repair will I am sure exceed the $100 USD I paid for the Bugera PS-1 Power Soak that Mike Soldano designed. I have been using it for years with zero problems. At the price, performance, heavy build and reliability it is a no-brainer to buy.

 

[Graham G]

I wouldn't even think about making anything for an attenuator since a small error or something breaking down can toast your amp. Any repair will I am sure exceed the $100 USD I paid for the Bugera PS-1 Power Soak that Mike Soldano designed. I have been using it for years with zero problems. At the price, performance, heavy build and reliability it is a no-brainer to buy.

Please don't think i'm trying to start an argument or trying to be a smart arse, but before i built Johns attenuator i thought pretty much the same as you, so i bought a PS1 & did a gig with it & didn't think the Amp sounded that great with the PS1(maybe a bit dead sounding), so i decided to build the M2 & to me the PS1 sounds "shit"(for want of a better word) in comparison(i think i commented so in a post), if i was you i'd build an M2(or have a tech build it if you prefer) & do a comparison, i suspect you may well think the same.
Cheers, Graham.

 

[diego_cl]

I wouldn't even think about making anything for an attenuator since a small error or something breaking down can toast your amp. Any repair will I am sure exceed the $100 USD I paid for the Bugera PS-1 Power Soak that Mike Soldano designed. I have been using it for years with zero problems. At the price, performance, heavy build and reliability it is a no-brainer to buy.

I had a Harley Benton PA-100 (I think it's a clone of the Bugera PS-1) and the attenuation pot was like a low pass filter... the attenuation muffled the tone. A 50W Marshall sounded like a subwoofer if cranked at bedroom level, pretty unusable. With a 22W Deluxe Reverb it wasn't nearly as bad, the tone suck was notorious but pretty acceptable.

The M2 attenuator is so much better, especially when attenuating a lot of dB. Anyway a quiet 12" speaker isn't inspiring, but that's not the attenuator fault.

 

[Gene Ballzz]

I wouldn't even think about making anything for an attenuator since a small error or something breaking down can toast your amp. Any repair will I am sure exceed the $100 USD I paid for the Bugera PS-1 Power Soak that Mike Soldano designed. I have been using it for years with zero problems. At the price, performance, heavy build and reliability it is a no-brainer to buy.

This project is definitely NOT for those with poor soldering skills and/or are not good at following instructions! Of course, that would also apply to making one's own speaker cable, rewiring one's speaker cabinet, etc, ad nauseam! The trick is (much like making sure you stay in your own lane on the road, to avoid fatality) to not make those small errors, check your work for confirmation and use quality components and procedures. If one lacks confidence in those skills, they should certainly NOT tackle this build or benefit from the enjoyment of the results! This project is intended for those somewhat skilled "do it yourselfers" who understand that paying attention to details and testing is the key to any successful outcome!

Most errors and accidents are the result of not paying attention! For example: If a person falls fatally off a cliff while walking with their face and attention buried in a smart phone, where does the fault lie? Is it with the cliff? No. Is it with the smart phone? No! Is it with……?

With that said and what @Graham G and @diego_cl said above, this attenuator design absolutely blows away any and all of the cheaper units, including the Bugera, Weber, etc, in terms of performance, tonal retention, response and feel.

You are of course, entitled to your opinion, and so am I. My opinion is that my skills (I build amplifiers and have been doing a wide variety of electronics repairs for +50 years) are quite likely at least a small step above those of the forced child laborers that are the probable assemblers of the Bugera units!

Of course, I also understand the propensity some have for piddling in others' bowls of Corn Flakes! That's OK too, as long as they're not MY Corn Flakes, as the consequences may be even less pleasurable than amplifier failure!

Enjoy Your PS1 & Your Opinion,
Gene

 

[Point 2 Point]

I lost track of this thread, glad you bumped it up.
As I recall the simple attenuator was / has been redesigned along the way, what is the latest design?
Page # 27?

 

[Freddy G]

This project is definitely NOT for those with poor soldering skills and/or are not good at following instructions! Of course, that would also apply to making one's own speaker cable, rewiring one's speaker cabinet, etc, ad nauseam! The trick is (much like making sure you stay in your own lane on the road, to avoid fatality) to not make those small errors, check your work for confirmation and use quality components and procedures. If one lacks confidence in those skills, they should certainly NOT tackle this build or benefit from the enjoyment of the results! This project is intended for those somewhat skilled "do it yourselfers" who understand that paying attention to details and testing is the key to any successful outcome!

Most errors and accidents are the result of not paying attention! For example: If a person falls fatally off a cliff while walking with their face and attention buried in a smart phone, where does the fault lie? Is it with the cliff? No. Is it with the smart phone? No! Is it with……?

With that said and what @Graham G and @diego_cl said above, this attenuator design absolutely blows away any and all of the cheaper units, including the Bugera, Weber, etc, in terms of performance, tonal retention, response and feel.

You are of course, entitled to your opinion, and so am I. My opinion is that my skills (I build amplifiers and have been doing a wide variety of electronics repairs for +50 years) are quite likely at least a small step above those of the forced child laborers that are the probable assemblers of the Bugera units!

Of course, I also understand the propensity some have for piddling in others' bowls of Corn Flakes! That's OK too, as long as they're not MY Corn Flakes, as the consequences may be even less pleasurable than amplifier failure!

Enjoy Your PS1 & Your Opinion,
Gene

I would like to add that there are not many attenuators I've met that didn't change the sound for the worse. So for me this DIY (I made two of these attenuators for my stereo rig) was worth it, whatever the cost. Because it is astonishing how well it works while keeping the sound AND feel of the amp in tact 100%.

 

[Gene Ballzz]

I would like to add that there are not many attenuators I've met that didn't change the sound for the worse. So for me this DIY (I made two of these attenuators for my stereo rig) was worth it, whatever the cost. Because it is astonishing how well it works while keeping the sound AND feel of the amp in tact 100%.

The fact that "Ears Extraordinare" @Freddy G has seen fit to grace us with his presence on this subject, should be no small testament to the stellar performance this design exhibits! For those who aren't aware, Freddy is one of the finest sound engineers on the planet, excellent luthier/guitar builder, proficient guitarist and all around great guy!

Thanks Freddy,
Gene

 

[JohnH]

I lost track of this thread, glad you bumped it up.
As I recall the simple attenuator was / has been redesigned along the way, what is the latest design?
Page # 27?

Post 1 on Page 1 has the latest basic schematic for the M2, which has been updated a few times. its probably due for another update, but its still right for the best base design that we have. If you want to read further, probably skip forward to about page 110. There are wiring layouts on pages 111 and 112, and you can read about a few options and variants from there.

Here's my view on who should build these:

Its not a complicated thing, actually its a very simple circuit with no complicated or active parts, nice big robust components and entirely passive. But, its going to be a key element at the end of a valuable amplifier and so it needs to be done correctly. This means it has to be wired right with the right parts, and the soldering and general construction has to be effective. It doesn't have to be beautiful (but many of them are), but good soldering with the right tools and procedure is neat and well 'flowed'. Its a craft skill that needs to be developed by practice and preferably by experience before tackling the attenuator.

There are quite a lot of wires between parts. You need a pictorial wiring diagram as a visual reference to work off. But you also need to be able to follow the flow of the circuit and for that you need to be able to understand the schematic (ie as on Post 1). My view is that, even though its not essential to understand the electronic theory, a builder of this attenuator should take the time to look at the schematic and understand what it is showing, and then relate that to a wiring layout. The wiring can be based on a layout you make yourself, or, see those on p111 and p112. With those in place , then you can trace your work, check it and correct it and troubleshoot it if needed

For a long time a resisted having the wiring diagrams here. The schematic was then like an 'entrance exam'. Those who can read it are likely to be able to follow through to a successful build. Wiring it up just from a wiring diagram 'paint by numbers' style without relating it to what is being connected to what risks an error going undetected.

Genes wiring diagram on p111 is great and its helped a few builds since. I see it best as a way of helping relate the build layout to the schematic, to step-up the understanding, rather than a lowering of the bar to avoid needing to understand.

Finally, before trying with an amp, it is entirely essential to run some multimeter tests to check resistances.


All that being said, we have maybe 50 or so successful and well-liked builds on this thread, and no amp damage reported to date! For those who can tackle the build, and have time and interest to do so, you can build a much better sounding and more robust attenuator than you can buy for the $.

 

[EC Strat]

Post 1 on Page 1 has the latest basic schematic for the M2, which has been updated a few times. its probably due for another update, but its still right for the best base design that we have. If you want to read further, probably skip forward to about page 110. There are wiring layouts on pages 111 and 112, and you can read about a few options and variants from there.

Here's my view on who should build these:

Its not a complicated thing, actually its a very simple circuit with no complicated or active parts, nice big robust components and entirely passive. But, its going to be a key element at the end of a valuable amplifier and so it needs to be done correctly. This means it has to be wired right with the right parts, and the soldering and general construction has to be effective. It doesn't have to be beautiful (but many of them are), but good soldering with the right tools and procedure is neat and well 'flowed'. Its a craft skill that needs to be developed by practice and preferably by experience before tackling the attenuator.

There are quite a lot of wires between parts. You need a pictorial wiring diagram as a visual reference to work off. But you also need to be able to follow the flow of the circuit and for that you need to be able to understand the schematic (ie as on Post 1). My view is that, even though its not essential to understand the electronic theory, a builder of this attenuator should take the time to look at the schematic and understand what it is showing, and then relate that to a wiring layout. The wiring can be based on a layout you make yourself, or, see those on p111 and p112. With those in place , then you can trace your work, check it and correct it and troubleshoot it if needed

For a long time a resisted having the wiring diagrams here. The schematic was then like an 'entrance exam'. Those who can read it are likely to be able to follow through to a successful build. Wiring it up just from a wiring diagram 'paint by numbers' style without relating it to what is being connected to what risks an error going undetected.

Genes wiring diagram on p111 is great and its helped a few builds since. I see it best as a way of helping relate the build layout to the schematic, to step-up the understanding, rather than a lowering of the bar to avoid needing to understand.

Finally, before trying with an amp, it is entirely essential to run some multimeter tests to check resistances.


All that being said, we have maybe 50 or so successful and well-liked builds on this thread, and no amp damage reported to date! For those who can tackle the build, and have time and interest to do so, you can build a much better sounding and more robust attenuator than you can buy for the $.

My biggest unknown is how I’m going to drill holes in the case - other than that, I’m good to go with the schematic

 

[diego_cl]

My biggest unknown is how I’m going to drill holes in the case - other than that, I’m good to go with the schematic

For me drilling the case was the most laborious part of the build. I had better and faster results using a punch tool with a hammer, a drill bit and a step drill bit.

The punch tool allowed me to use the drill by hand without the need of my shitty portable drill guide. I used that guide before and the holes ended up crooked and it was way too time consuming.

Using a heavy drill bit at once was also a bad idea, because it was slow, imprecise and it shaved the holes in an ugly way.

The notch made by the punch tool allowed me to use a drill by hand without wandering around the surface. The drill bit had to be big enough for the step drill bit and for not flexing with compression, but small enough so it would drill fast. The step drill bit saved me a lot of time. The one thing I didn't like about the step drill bit is the lack of control over the bevels of every hole.

I wish I have a drill press though.

 

[JohnH]

My biggest unknown is how I’m going to drill holes in the case - other than that, I’m good to go with the schematic

Aluminium drills pretty good with normal hand tools. Gene and a few others have superior workshop skills. But I do OK with a careful mark out onto masking tape, very small pilot holes, then two or three sizes of drill to get up to large diameters such as for Jacks or if you have large toggles. A bench vice or equivalent clamping is a must-have and if you have access to a drill-press it is much better but its possible with a hand-held cordless.

I like to buy unpainted cases - then when I've drilled I can clean up my workshop sins and do a black rattle can finish, including into the raw edges of vent holes.

 

[Barnsley Boy]

I wouldn't even think about making anything for an attenuator since a small error or something breaking down can toast your amp. Any repair will I am sure exceed the $100 USD I paid for the Bugera PS-1 Power Soak that Mike Soldano designed. I have been using it for years with zero problems. At the price, performance, heavy build and reliability it is a no-brainer to buy.

I have previously owned a Jettenuator (same as PS-1) which I used to tame my lovely Cornford Roadhouse running into a 2 x 12 with Greenbacks. The amp was a beast. If only @JohnH had come up with the M2 design back then, I would never have sold the Roadhouse. I almost made the same mistake again with my newly aquired JCM900, but thankfully @Gene Ballzz pointed me in the right direction. If you can solder, drill holes and follow instructions as said previously you can build something that blows an L-pad based resistive out of the water.

@Paul L Ewing it really is a great bit of kit. Lots of the builds are crammed into some quite small enclosures which can be challenging if soldering is not your strong point. Also using mini toggles is a bit fiddly. Failing that, buy all the bits and bung a mate who's handy with a soldering iron a few quid/ bucks/ euros/ rubles to do it for you. You won't be sorry .... trust me!

 

[Lancer X]

My biggest unknown is how I’m going to drill holes in the case - other than that, I’m good to go with the schematic

Even a cheap set of step drill bits will make this project (and any future amp chassis mods you tackle) so much easier. As @JohnH said, aluminum is also much, much easier to modify than steel.

A drill press is recommended. I hand-drilled mine, and it made for a pretty physical evening of drill-wrangling.

 

[EC Strat]

Even a cheap set of step drill bits will make this project (and any future amp chassis mods you tackle) so much easier. As @JohnH said, aluminum is also much, much easier to modify than steel.

A drill press is recommended. I hand-drilled mine, and it made for a pretty physical evening of drill-wrangling.

Appreciate the advice

BTW What sized drill bits did you use? Looks like 1/8” bit should do the trick

 

[EC Strat]

Well, parts have all arrived. Got the resistors labeled

@JohnH - I’d like to do a bypass switch - is there a schematic showing that?

 

[JohnH]

Hi @EC Strat , Some do build these in. Can you remind me how many output sockets are you using, ie just one or two in parallel or are you doing the output 3 as well (makes bypass more tricky)

Also, do you really need a bypass? because with a bypass engaged, you could instead just not use an attenuator. After a few tests you are likely to find that just one or two settings are all you use. Unless your use involves often adjusting between attenuated or not, then maybe you dont need one? A bypass switch is switching the full power and current of the amp, and must never be operated unless the amp is off or on standby, whereas with the other switches they can be operated on the fly.