attenuator airbrake

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Re: attenuator airbrake

Post by JMPGuitars »

I think D fits the motif best.
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Re: attenuator airbrake

Post by ViperDoc »

WOW, I just stumbled onto this thread. I just picked up the pieces for making two of these Airbrakes minus the rheostat only because they're not available. I'll likely build one up with the gold resistor in place of the stat for now. NICE examples. I was simply going to use the layout as posted in the very beginning of this thread, but would you recommend one of the others? Need to re-read this to find out.

The Honey Hush graphic is awesome, man!
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Re: attenuator airbrake

Post by JMPGuitars »

ViperDoc wrote:
Thu 10/01/20 5:59 pm
WOW, I just stumbled onto this thread. I just picked up the pieces for making two of these Airbrakes minus the rheostat only because they're not available. I'll likely build one up with the gold resistor in place of the stat for now. NICE examples. I was simply going to use the layout as posted in the very beginning of this thread, but would you recommend one of the others? Need to re-read this to find out.

The Honey Hush graphic is awesome, man!
This is the project doc I made for it: files/JMPGuitars_Break_Wind_Attenuator.pdf
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Re: attenuator airbrake

Post by crgfrench »

ViperDoc wrote:
Thu 10/01/20 5:59 pm
The Honey Hush graphic is awesome, man!
Thanks!
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Re: attenuator airbrake

Post by crgfrench »

ViperDoc wrote:
Thu 10/01/20 5:59 pm
I just picked up the pieces for making two of these Airbrakes minus the rheostat only because they're not available. I'll likely build one up with the gold resistor in place of the stat for now.
The next ones I build are only going to have the rheostat, the switch doesn't really do much sonically -- 2dB cuts are kind of worthless IMHO; it's once you get to the -10dB to -30dB range that actually accomplishes meaningful volume attenuation.
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Re: attenuator airbrake

Post by JMPGuitars »

crgfrench wrote:
Fri 10/02/20 12:42 am
The next ones I build are only going to have the rheostat, the switch doesn't really do much sonically -- 2dB cuts are kind of worthless IMHO; it's once you get to the -10dB to -30dB range that actually accomplishes meaningful volume attenuation.
You're missing two things:

1. The 2db cuts can be set higher by where you position the tabs.

2. Those 100W resistors are what make the attenuator rated for 100W. Even if you skip the tabs, you still want the resistors to handle the power. The rheostat alone might be enough for an 18watter, but I wouldn't go higher than that without the fat resistors in there.
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Re: attenuator airbrake

Post by crgfrench »

Exactly. The 2 big ohmite hot dogs and the ohmite rheostat.
No lorlin switch.
Here's a schem and layout.
Screen Shot 2020-10-02 at 11.42.38 PM.png
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Re: attenuator airbrake

Post by crgfrench »

Save some dough too!
Screen Shot 2020-10-02 at 11.52.53 PM.png
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Re: attenuator airbrake

Post by crgfrench »

Note, this version has no bypass mode.
So it's going to be -10dB to -30dB output. No full strength.
You could stick a DPDT switch where the Lorlin normally goes and have a bypass mode.
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Re: attenuator airbrake

Post by BlueBoozer »

So I built one of these and have It between my 100W head and 4x12 stack. Intrestingly, the Ohmite 100W resistor on the ground side is heating up like Satan's pocket watch. Is this normal? do I need to cut air holes in the side of this thing? Should I be considering thermal compound?

The other resistor isn't getting as hot and the Rheostat is staying cool also. Just that ground resistor is heating up.

It works great, cranked the amp and on bypass it brought my son and the dog both downstairs to investigate. Cranked up the resistance and we could almost carry on a conversation.
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Re: attenuator airbrake

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BlueBoozer wrote:
Sun 10/11/20 7:46 pm
So I built one of these and have It between my 100W head and 4x12 stack. Intrestingly, the Ohmite 100W resistor on the ground side is heating up like Satan's pocket watch. Is this normal? do I need to cut air holes in the side of this thing? Should I be considering thermal compound?

The other resistor isn't getting as hot and the Rheostat is staying cool also. Just that ground resistor is heating up.

It works great, cranked the amp and on bypass it brought my son and the dog both downstairs to investigate. Cranked up the resistance and we could almost carry on a conversation.
Some people say to use an attenuator rated for double the wattage of your amp, especially if you're going to be attenuating a lot, or for extended periods.

You could try leaving the cover plate open, and see if that has a meaningful effect on the heat issue before drilling any vent holes.

I'm using this with 18W to 40W amps. I don't think I would go above 50W.

Thanks,
Josh
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Re: attenuator airbrake

Post by BlueBoozer »

alrightythen. I'll just use it with my 18 and 50 watt heads. Thanks
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Re: attenuator airbrake

Post by crgfrench »

I've used it on 18W and 36W, never noticed much heating but I didn't test extensively at cranked volumes with the 36. Never used on any amp over 36 yet...
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Re: attenuator airbrake

Post by crgfrench »

JMPGuitars wrote:
Fri 10/02/20 6:39 am
... The 2db cuts can be set higher by where you position the tabs...
With 25 Ohm R1 & R2, You won't get more than -8dB of total attenuation unless you switch on the Rheostat. The first 2dB comes from switching in R1, and the next 6 comes from switching in R2. No real audio value in shoving all the tabs together, for example, to increase one of those 3 cuts at the expense of the others. You won't get more than 6dB total out of R2. So if you increase the cut of first tab by sliding it to add resistance, you're just robbing the other 2 tabs of reduction ability.
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Re: attenuator airbrake

Post by colossal »

JimbpGaff wrote:
Tue 05/12/20 2:58 am
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
There is an impedance mismatch for any given level of attenuation but 16ohm is the least mismatched.

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Re: attenuator airbrake

Post by colossal »

BlueBoozer wrote:
Sun 10/11/20 8:59 pm
alrightythen. I'll just use it with my 18 and 50 watt heads. Thanks
It will handle 18-50W with no issue. If you run a 100W Marshall or a vintage AC30, definitely run the amp at 16 ohms into the Airbrake.
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Re: attenuator airbrake

Post by yello »

I have acquired a few LARGE Ohmite resistors in a parts pile purchase, and I am pondering making either an attenuator to use when playing my amps, or a load device for when I test amps. These are the resistors:

-225w 25 ohm - quantity 2

-225w 50 ohm - quantity 4

If I make an attenuator, I'd like to make a simple version, one that is hard-wired to a certain level of attenuation to keep it simple, and to not over-attenuate as that sounds bad to me. Just something to knock volume down a bit, take the edge off. I mainly play through an 8 ohm cab, so that is what I need to calculate it to work with.

However, I'm not good at the math bit - any tips on where to start calculating and then drawing it up? Which of the above resistors do I use, and do I need the rheostat, etc. from the "Break Wind schematic"? I realize these resistors are overkill, but they are on hand so short of selling/trading them, I'd like to use them.

For a reference, I am looking at the Break Wind schematic by @JMPGuitars, as well as the modified version by @crgfrench, both in previous posts in this thread.
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