attenuator airbrake

[colossal]

Very nice! What enclosure did you use? Is that a Hammond? I like the black powder coat.

[JMPGuitars]

Very nice! What enclosure did you use? Is that a Hammond? I like the black powder coat.

Thanks! Yes, it's a Hammond. Any enclosure they offer, you can usually find a powder coated version.

Here's the exact parts list I setup on Mouser:

attenuator.xls

That includes everything I used except all the 18AWG wire.

Thanks,
Josh

[JMPGuitars]

Here's the demo of mine: https://youtu.be/3oSZVg2STXw

Most of the demo is okay, but when I turned it down too low, my camera automatically increased the sound level. Oops.

[colossal]

Good work! Despite the camera increasing the volume, you can hear the strings once you are down into bedroom level, so you know it is definitely is doing its thing. How did you find the transparency/tone retention at higher levels of attenuation?

[JMPGuitars]

Good work! Despite the camera increasing the volume, you can hear the strings once you are down into bedroom level, so you know it is definitely is doing its thing. How did you find the transparency/tone retention at higher levels of attenuation?

That's a good point.

I haven't played enough with it to form a solid opinion on the tone retention. There's maybe a drop in trebles, but not bad at all. And that's with the EQ on the amp flat, so it seemed like it would be easy to compensate for. What I really want to do is compare it to my MiniMass and see which one I like better. My first, and biased opinion, is that I like this shiny new one better.

In the short time I have played with it, it sounds pretty transparent to me otherwise. The perception of the change in tone is hard to measure accurately. So I will focus on which unit I think sounds better, and update this eventually.

[katopan]

Good work Josh. Thanks for the report back. Looking forward to seeing if you still like it after the honeymoon period.

[JMPGuitars]

I shared the doc I made: files/JMPGuitars_Break_Wind_Attenuator.pdf

It's also in the Miscellaneous Stuff page: viewtopic.php?f=25&t=24414&p=235766#p235766

I simplified it. The other layouts I've seen weren't very logical.

[ZeroPointEnergy]

OK, great! I want to read up on this thread! I want an economical power soak and dummy load! And I'm on a budget, so a DIY attenuator, sounds just what I was hoping for!

[JimbpGaff]

Great info.

\not sure if I missed in in the threads but is this for a 16 ohm load and how much attenuation will it give.
Jim

[JMPGuitars]

Great info.

\not sure if I missed in in the threads but is this for a 16 ohm load and how much attenuation will it give.
Jim

I posted a demo above. When the attenuation is increased, you can hear the guitar strings in the video. That's pretty significant.

16 ohm is supposedly ideal, but it also works with 8 and 4 ohm loads.

[colossal]

Great info.

not sure if I missed it in the threads but is this for a 16 ohm load and how much attenuation will it give.
Jim

As Josh said, the attenuator will "work" for 4 and 8 ohm loads, but is best suited for 16. See the first page of this thread for a plot of impedance vs. attenuation.

[JimbpGaff]

Can I use a different value Rheostat ?
The 150 ohm 50 watt is hard to come by at the moment in the UK as they all seem to be on back order until the end of the year.
Jim

[colossal]

Can I use a different value Rheostat ?
The 150 ohm 50 watt is hard to come by at the moment in the UK as they all seem to be on back order until the end of the year.
Jim

You can. Lower values will limit attenuation. Higher values will increase it at the expense of increasing impedance.

[JMPGuitars]

Can I use a different value Rheostat ?
The 150 ohm 50 watt is hard to come by at the moment in the UK as they all seem to be on back order until the end of the year.
Jim

You can. Lower values will limit attenuation. Higher values will increase it at the expense of increasing impedance.

Limiting attenuation isn't a bad thing, since there will be less tone sucking that way. BUT there's limited options in that price range. I looked at alternatives, and they get pretty expensive. The RJS125E for example is 125 ohms, and $80. Some other variations were hundreds of dollars.

Personally I got a couple of the RJS150Es on eBay for $40 a piece. There is a seller in the UK selling the 150 also, but not as cheap. The 125 is available on there too, but I dunno about in the UK.

Thanks,
Josh

[JimbpGaff]

Thanks Josh

Just found the one on ebay for $77.00.

A lot of money in these difficult times .

I will have to do some thinking .

The pure resistor attenuator is a cheaper option, But.....
Jim

[JMPGuitars]

Thanks Josh

Just found the one on ebay for $77.00.

A lot of money in these difficult times .

I will have to do some thinking .

The pure resistor attenuator is a cheaper option, But.....
Jim

Yeah, it's not cheap. But it's only $14 more than Mouser sells it for if you can't wait for people to have it in stock. On the other hand, you could build this attenuator without the rheostat, and use the switched section until a better deal on the rheostat becomes available. You can increase the resistance for the lugs and have the switched section attenuate at higher levels in the meantime.

[JimbpGaff]

Thanks Josh.

I will do some thinking .
Jim

[crgfrench]

I'm building a Trainwreck-style attenuator right now and I decided to draw up 4 possible wiring possibilities as schematics. All 4 of these are electrically identical and it is the same circuit. the only difference is the wiring sequence in which R1 is connected in the circuit. I drew all 4 in bypass mode.

Josh posted my #1, "Attenuator Type 1" on 4/29/20 and I don't know the source; its R1 sequence is: Input, R1, Lorlin Switch Pins, "A" (On the Lorlin switch), then Ground.

Mehfuzhoss posted my #2, "TDPRI Layout" on 4/22/20 and I drew up the schematic from that layout; its R1 sequence is: Input, "A", Pins, R1, then Ground.

Katopan posted my #3, "JMP/Audiofanzine Layout" on 4/23/20 and I drew up the schematic from that; its R1 sequence is: Input, Pins, "A", R1, then Ground.

There is a fourth possibility I haven't ever seen, so I drew up #4, "Not Seen in the Wild". Its R1 sequence is Input, R1, "A", Pins, then Ground.

The R2, cap and rheostat structure is common to all four of these wiring possibilities.

[I noticed Josh drew his layout with pin 7 going to the wiper, it was just easier (and electrically the same) for me to draw 7 to the leg in the schematic.]

Trainwreck Airbrake Wiring Possibilities.png

[crgfrench]

I drew up wiring diagrams for all 4 of these schematics, and I like the JMP/Audiofanzine setup the best -- mainly I like the simplicity of daisy-chaining pins 11-5 on the switch. Here is my wiring diagram for that. Note, if you align the centers of the switch and the Rheostat, and face pins 6/7 at the rheostat, the switch knob pointer will point at the pot control when selected (nice from a user interface perspective). With jacks on the short side and resistor mounts on the long sides, the switch and pot will be the only things poking through the face of the enclosure, which is nice for graphics. Mine is going inside a combo cabinet and I added an external speaker out jack to the output.

Attenuator Layout.png

[crgfrench]

I cleaned up that Audiofanzine schematic a bit. You can use 6, 11 and 16 Ohm taps on R2; I decided to use 5, 11 and 17.

Screen Shot 2020-08-01 at 10.59.38 AM.png