Does anyone know of a easy attenuator circuit?

[Chuck H]

Nearly all the affordable attenuators are purely resistive. Parts for dynamic impedance load attenuators are expensive and must be purchased on line in most cases. In this light a resistive attenuator is the only type that meets the criteria set forth in your OP. The resistive attenuator with the best reputation for tone is probably the Air Brake (Dr. Z or Trainwreck). That particular attenuator runs the load at a considerably higher impedance than rated. Speculation is that because only a small amount of the frequency band is as low as the rated ohms for a guitar speaker a higher general impedance should sound more accurate. This makes some sense too. I haven't tried a higher impedance for my resistive attenuator circuit. It makes me nervous to run an amp flat out into a higher than rated impedance. Though I don't read that people are having any trouble doing it. Any hoo... Some things to consider. Maybe try a resistive load of something like 20 ohms instead of 8.

You still haven't identified your L-pad. Is it the wall mount type with circuits other than resistors inside? Does it look like a simple rheostat?

[daz]

You still haven't identified your L-pad. Is it the wall mount type with circuits other than resistors inside? Does it look like a simple rheostat?

Yes, a 50w rheostat. It was a tweeter level control for a fender 410 bass cab if i recall correctly.

[Tom Phillips]

Yes, a 50w rheostat. It was a tweeter level control for a fender 410 bass cab if i recall correctly.

OK. So that's not an "L-Pad" at all. Just a high power variable resistor.

[daz]

OK. So that's not an "L-Pad" at all. Just a high power variable resistor.

How would it be a variable resistor? It's 8 ohm, and if it were a resistor how would it stay at 8 ohms? I thought a wire wound variable keeps the same ohm value. A resistor definitely doesn't. Fender even calls it an L-pad in it's description. What am i missing?

[Regis]

This page has a good explanation of L-pads. They can be fixed or variable. I've built several of both.

Here is a simple two stage attenuator by Gerald Weber that works good, and a link to some resistors to use that will take any power you throw at it.

[daz]

Yep....2nd 3rd and 4th pics down are what have, a wirewound Lpad. I'll check out that PDF, but Isn't that weber just a fixed Lpad with a couple settings? I've made a few of them with various attenuation levels and they never sounded very good. But from what you guys are saying maybe i just needed to make one with a lot of attenuation so i can really crank it up.

This page has a good explanation of L-pads. They can be fixed or variable. I've built several of both.

Here is a simple two stage attenuator by Gerald Weber that works good, and a link to some resistors to use that will take any power you throw at it.

[Chuck H]

Try to remember that if you like the sound of your amp when it's loud, loud is part of the equation. Or at least 'as loud'. So variable attenuation will be necessary to get the right volume level. And, as I mentioned, some resistive attenuators use a higher resistance to simulate the tone of an active load more accurately. This could still be tried too. There are a few options. I know that you haven't been happy with attenuators in the past. You don't seem to be happy with attenuation now. Are you happy with the sound of your amp when it's power tube clipping WITHOUT an attenuator? I know you don't get much chance to hear it like that. If you're using setting with attenuation that you typically DON'T use when no master volume is employed, perhaps you just don't like the way your amp sounds when operated that way. Attenuator or not.

[daz]

Well thats why i don't want to spend a lot of time or money on it, because DON'T know if i like it like that. I imagine i would because from the CF on back it's like a 800 and i used to gig with those and thats where they sounded best. I love my amp as is at low volume but for one thing....I want the volume control on the guitar to have a wider range of clean to OD than it does, and i'm NOT saying it doesn't do that well *for preamp OD*. My marshalls did not better at low volumes. So i was thinking that with the output adding some OD it would be more dynamic as power amp OD generally is. I could lower the preamp gain and make up that amount in the more dynamic pwr amp OD.

[Chuck H]

Well, the obvious first criteria would be to take the first chance you can to get the amp up loud and find a cranked tone you like. Turn the master all the way up and turn the preamps "stacked" stage drive down a bit. Then crank up the normal (second) volume and adjust from there. If you find settings you like (and I bet you will) use the attenuator with those settings and THEN see if the compromise is unacceptable.

Right now I'm reduced to playing my amp through headphones. Yuck. My attenuator simulates the dynamic impedance of a proper speaker well enough. And I built a box to EQ the signal like the frequency response of a guitar speaker. It's imperfect at best. I accept the compromise because I must. The elements that are missing are the further dynamics of an actual speaker. Being that the dynamic impedance and frequency responses change and react in actual use and power. The static circuits will never do that. And the sheer volume that creates acoustic interaction is missing as well. These elements turn out to be critical IMO. My point is that you can't take away anything without losing something.

[Regis]

I like using attenuators, like I said, I've built and use a number of them. I've given up worrying whether an amp sounds the same at 3db vs 100db. I haven't heard every attenuator on the planet, but a heavily attenuated, overdriven amp is not going to sound the same as an overdriven amp wide open. I know a lot of attenuator manufacturers claim theirs do, but I don't buy it.

One, you're not moving air. You're not getting that physical "whomp" that a loud cabinet delivers.

Two, you're removing the speaker from the equation. At lower volume levels it isn't adding anything or distorting, it's merely reproducing what the amp is giving it.

It's similar to all these effect pedals that claim to put a Marshall in a box, or Dumble, or whatever. Just not the same.


When I want to rock out without cracking the walls, I crank it up, drive the bejesus out of the amp with something like a tube screamer, and it is what it is.

[daz]

I like using attenuators, like I said, I've built and use a number of them. I've given up worrying whether an amp sounds the same at 3db vs 100db.

Thats not my issue. I expect it to sound different. If i didn't why would i even be using one? Unfortunately the Lpad types i've used tend to sound worse, not better like i expect to get from using an attenuator.

[Alan0354]

OK, I have not read the whole thread. I replace one of the 8ohm speaker in my Pro Reverb with a 10ohm power resistor and it works great. I actually did quite detail comparison of different value. Too low resistance will attenuate too much bottom. 10 ohm is the best. I compare with my THD Hotplate at -4dB setting. I definitely think the 10 ohm resistor sounded truer to the amp.

If you are asking for small attenuation like getting a 40W amp down to about 20W, AND you have two speakers, this is the way to go.

It is easy to try, just use a 1W or so resistor to test the sound before you even buy the big resistor. Just try for a minute, if the resistor burn, it burn!!!

[Chuck H]

By disabling a speaker you actually lose more volume than if you simply half the wattage. You also change the cabinet speaker relationships. But, indeed, you're right. If one didn't want to disconnect a speaker to do this, and the amp has an impedance selector available, you could also set the impedance selector to accommodate adding a resistor to the load. ie: using an 8 ohm cabinet you could set the selector for 16 ohms and put a 10 ohm resistor in series with the speaker load. Or set the selector for 4 ohms and put a 10 ohm resistor parallel to the speaker load. Or... In the case of a Marshall, where the primary impedance is typically quite low, you could just leave the selector set properly and add a series resistor equal to the load. This would cut volume via the resistor absorbing half or better the power and the mismatch will reduce efficiency as well. A Marshall amp won't mind. I promise. Many players intentionally run their 16 ohm cabs off the 8 ohm tap on purpose because they think it sounds better. I'll bet if you asked an old school tube guy if EL34's at 480Vp should be run into a 3500 ohm primary or a 7000 ohm primary (assuming you could only pick one or the other) they would pick 7000 ohms.

[Alan0354]

I found putting resistor in series change the sound. So far Putting a resistor in parallel to take about half the power away seems to get me the closest to the original sound. I only detect a slight loss in bass which I can compensate by cranking up the bass a little bit. But yes, the down fall is it only lower by half. I tried any lower resistance combination will change too much.

[daz]

I found putting resistor in series change the sound. So far Putting a resistor in parallel to take about half the power away seems to get me the closest to the original sound. I only detect a slight loss in bass which I can compensate by cranking up the bass a little bit. But yes, the down fall is it only lower by half. I tried any lower resistance combination will change too much.

I've done that with a 8 ohm 100w resistor and my 8 ohm speaker in parallel then set the impedance to 4 ohms. It does work pretty well but it didn't drop the volume near enough to do what i want.