Power Attenuators? (home-brewed?!)

[Jono_L]

I reckon I really need an attenuator for the Laney, seeing as I just can't get proper bedroom levels without sacrificing tone big time.

I've been reading up, and I reckon its perfectly feasible to build one, following this site:

http://www.zugster.net/amps/articles/attenuation/

I reckon I'll be going for the Bridged-T setup, and I've already got an Excel spreadsheet running for different attenuation values with different resistors. Looking for around 20dB SPL decrease at max settings (and therefore, reducing the SPL of the amp when put on 7 to around 90dB A-weighted when mic'ed 1m away, which is perfectly acceptable by my standards). Housing the damned thing is a problem though - I have NO idea what I can house the thing in thats available locally, but I'm thinking an aluminium box of some sort. Probably end up rigging a cooling fan or something like that to keep temperatures as cool as possible. Any suggestions in terms of housing such devices?

The project itself should be VERY cheap. It'll cost me the price of 2 jacks, a bunch of resistors, and a switch, which is perfect considering my tight budget right now

So yeah, the point is, has anybody used any attenuation devices before? And even better, has anybody BUILT any attenuation devices before? Most of all, do you reckon that the home-brew method would work for attenuation on a budget?

 

[Stevo]

Re: Power Attenuators? (home-brewed?!)

I have built a couple but I used L-pads, which have variable resistance.

It's also good to have an inductive load, like a speaker, which impedes certain frequencies and puts less stress on your amp.

 

[Jono_L]

Re: Power Attenuators? (home-brewed?!)

Stevo, just wondering, what did you use to house your attenuator in?

 

[Baltar]

Re: Power Attenuators? (home-brewed?!)

hehe, never warmed up such an old thread before

i was thinking about the same thing. but the sheet linked above is not
accessible anymore. does anybody have it or sth similar?

i saw a very unsatisfying descriptiption about the same theory here ..
http://www.amptone.com/diyattenuationcab.htm (scematics would be nice)

at home i have an old sheet regarding db reducing of speakers while
keeping the impedance. i think it's the same - just at other power levels.

how many dB do i have to shred down to approxomately make a 5 w amp
out of an 50w amp.
i know it's a silly question as is, but an estimation would help a lot.

 

[guitarslinger213]

Re: Power Attenuators? (home-brewed?!)

hehe, never warmed up such an old thread before

i was thinking about the same thing. but the sheet linked above is not
accessible anymore. does anybody have it or sth similar?

i saw a very unsatisfying descriptiption about the same theory here ..
http://www.amptone.com/diyattenuationcab.htm (scematics would be nice)

at home i have an old sheet regarding db reducing of speakers while
keeping the impedance. i think it's the same - just at other power levels.

how many dB do i have to shred down to approxomately make a 5 w amp
out of an 50w amp.
i know it's a silly question as is, but an estimation would help a lot.

If my calculations are close, a 12 db reduction will be close to a 6 watt amp. I could be totally wrong HAHAHA:fingersx:

 

[Baltar]

Re: Power Attenuators? (home-brewed?!)

If my calculations are close, a 12 db reduction will be close to a 6 watt amp. I could be totally wrong HAHAHA:fingersx:

an interesting point to start ... i'll give it a try

on question about the implementation.
i don't want to risk my output transformer; for that reduction, you always need
a resistor in parallel to the speaker and one in serial. if i nee do too choose lower
or higher, due to series, how should i decide ... a little higher impedance or lower?
eg if the amp is switched to eight ohms, do i rather go for 7,8 or 8,2 or is that
not really important?

 

[Baltar]

Re: Power Attenuators? (home-brewed?!)

yesterday i tried that out ..

i mounted ceramic hifi-resistors on a heatsink with thermal glue,
reducing the signal by 5,5 dB

the effect is ok, but not satisfying yet.
i need to put the power amps pot about 2 1/2 more than usual and at
some volume it does sound better.

but if i calculated correctly, this reduces my 50w amp to sth like 12w, which
is still too much for home.

i think i keep that box and build a second one for -8 dB soon

 

[Stevo]

Re: Power Attenuators? (home-brewed?!)

Stevo, just wondering, what did you use to house your attenuator in?

I just got a vented metal box at a local electronics store.. it took a lot of abuse but I used it for about 3 years.

 

[Baltar]

Re: Power Attenuators? (home-brewed?!)

what is the big difference between attenuators and l-pads ? ...
the technical part is clear to me, but i mean is there a
difference in sound or risk for the amp?

i ask, because the price difference is huge.
http://www.madisound.com/cgi-bin/index.cgi?keywords=attenuator&cart_id=3D%

i now use a simple voltage divider with some ceramic resistors, which works
but is a little bit unvairable. an l-pad would be a nice solution, but is there
any big disadvantage in l-pads?
why does everyone go for the expensive attenuators

please discuss

 

[schecterplayer]

Re: Power Attenuators? (home-brewed?!)

does anyone have a more detailed overview on what making an attenuator would cost and how you would go about it? I looked at the pages linked to in this thread and im still really confused.