Has anyone tried this L-Pad attenuator idea?

mistermikev · Post by **mistermikev** » 11 Aug 2010, 20:01

Hello,
just wondering if anyone else has attempted the L-pad based attentuator referenced here: http://www.buildyourownclone.com/board/ ... or#p188346

seems like a great idea... and I guess I don't know any reason it wouldn't work... still I'd wrather someone else be the ginea pig on this one!

Mr.Grumpy · Post by **Mr.Grumpy** » 12 Aug 2010, 02:34

I will admit to doing this many (20+) years ago, to a silverface Princeton Reverb.

I bought a 40-watt, 8 ohm L-pad from my local RadioShack, and soldered a 1/4" plug for the input and a 1/4" jack for the output and drilled holes on the back filler panel to hold it. IT WORKED....well sort of. I was able to get distortion at bedroom volumes. Of course, being a surgically clean SF Fender, there's no distortion until the volume is at 8 or above. I jammed for a few minutes with the amps volume all the way up, then I started noticing a "hot electrical" smell, and got nervous that I was cooking my output transformer. I decided my TS-808 sounded pretty much the same and probably wouldn't cook my amplifier, so I only ended up experimenting with it a couple of times.

Cliff Notes:
1) Yes, it works
2) You might blow your amp up, or cook the speaker transformer.

If you are seriously going to try this - use an L-pad with a HIGHER wattage rating than your amp, I suspect many tube amps are conservatively rated for power and will put out more than their rated watts when overdriven. And of course the load impedance MUST match or you could damage your speaker (output) transformer.

culturejam · Post by **culturejam** » 12 Aug 2010, 12:31

I installed one on a Valve Jr and it worked great.

mistermikev · Post by **mistermikev** » 12 Aug 2010, 15:50

thanks for the replies guys!
I've got a 60 watt hot rod deville and I love the tone I get with my ge fuzz blasting the front end and the amp at about 4, but it's a hair loud for my neighborhood...
I was thinking of buying the 8ohm 100w lpad... after all it's only $12!

I guess... a $12 gamble on whether I'll smell the tell tale 'electrical burn smell'... or perhaps I'll just hunt down a proper attenuator on cl...
thanks again for the advice!

DougH · Post by **DougH** » 13 Aug 2010, 15:46

For a purely resistive attenuator, an exact impedance match is not necessary. If you look at a graph of speaker impedance vs. frequency, there are many areas where the impedance will be several times the speaker's rated impedance. The average impedance over the useful freq range is usually much higher than the rated impedance as well. This is why many commercial resistive attenuators are higher impedance (resistance) than the speaker/amp ratings. As much as you can mimic the frequency-dependent varying impedance of a speaker with a resistor- they sound better that way and don't hurt a thing.

For an inductive attenuator I would be more concerned about impedance matching. They will have the freq-dependent impedance spikes similar to a speaker.

aquataur · Post by **aquataur** » 19 Aug 2010, 11:59

Mr.Grumpy wrote:I decided my TS-808 sounded pretty much the same [...]

Cliff Notes:
1) Yes, it works
2) You might blow your amp up, or cook the speaker transformer.

Completely agree with you on this mate. I personally strongly advise against attentuators because they let your amp run at continuous power levels they might not be made for.

Many companies sell attentuators, and most of the time those are the same companies that sell you overpriced output tubes which you will need galore if you use their attenuator.

If you are into serious tube amp tinkering I strongly recommend reading londonpower´s tube amp books by Kevin O´Connor : http://www.londonpower.com/tube-amp-books.htm.

He reveals everything they try to trick you into and he shows how to make it right. He explains about the psychology of hearing at loud levels and how to recreate loud sounds with cool amps.

I am not affiliated with that company, but I have read many of their books and find them by far the best source of information available today.

--helmut

mistermikev · Post by **mistermikev** » 20 Aug 2010, 22:26

ok, so here's what I'll take away from this enlightening discussion:
-either build one of them murder one jobbies... or just get a 5watt tube amp as opposed to getting an attenuator.

culturejam · Post by **culturejam** » 21 Aug 2010, 06:06

mistermikev wrote:-either build one of them murder one jobbies... or just get a 5watt tube amp as opposed to getting an attenuator.

Yeah, that's probably a good plan.

earthtonesaudio · Post by **earthtonesaudio** » 23 Aug 2010, 11:49

mistermikev wrote:ok, so here's what I'll take away from this enlightening discussion:
-either build one of them murder one jobbies... or just get a 5watt tube amp as opposed to getting an attenuator.

Yes. You'll be glad you did when your electric bill comes.

phatt · Post by **phatt** » 23 Aug 2010, 14:35

Hello Mistermike,

Oh that ever lovin attenuator thing always gets a bad rap which is understandable but it's only half of what can be made a very good setup.
By load boxing the Amp and grabbing a line signal via simple voltage divider you can then go crazy as you can then send the signal to another amp.

**You now have access to sounds and tone that a single rig player can only dream about.**
Only the *2nd Amplifier drives the speaker*.

There are basically 3 or 4 ways to get Absolute SPL control;

1/Attenuator, can be made to work but a lot of fussin about.
(people make the mistake of loading 8 Ohms with an 8 Ohm Resistor and that puts a fair stress on the output)

2/ London powerscaling (already mentioned) *a brilliant idea* but can have some issues with preamp/poweramp balance.

3/Dana VVR, simple and effective and reasonably priced and simple to setup.
very similar idea to King tuts P Scaling.

4/ Reamplifiy a small tube amp as above.
Downside, You need 2 Amps,,so you carry more gear.
Upside, You get to impliment tone shaping AFTER the poweramp sound as well
as time based efx.
(You can now do tricks that can normally only be done in a studio)

Needless to say,,I went with Reampliying a small PP 10 Watt Valve Amp.
(just the ability to do *post powerstage tone tricks* sold me)

Be aware that if your 2nd amp is a monster higain rig with many stages
it may well hinder your progress. Maybe in through the Efx return
on some rigs might work. Ideally the 2nd amp needs a flat/neutral response.
I actually use a SS keyboard Amp.

Notes on Reamping;
I use a 27 Ohm load as 8 Ohm load on 8 Ohm output
just turns my Amp into a very large, very heavy, High Voltage Tube Screamer. Yuk!
A higher load R allows the PowerStage to breath, so much more rewarding,
an likely puts far less stress on the expensive bits.

Obviously if you wish to soak a 200 watt Marshall Major at 2 in the morning,,

then you need to rethink. Very very low SPL (bedroom) is really
a whole different bunch of issues again.
And you understand like all things electronic there are pros an cons for all these ideas.

Here is a little pic to give you an idea of just how simple it can be done.
Have fun, Phil.

aquataur · Post by **aquataur** » 23 Aug 2010, 21:03

With power soaks you basically transform an amplifier into one huge distortion generator.

Every company´s amp has its own characteristic anyway, but overdriven you nail it to one, or, at best, two different sounds, because the clipping makes all tones even. Unless you are a dedicated rocker, this is a bit weak.

Moreover, in times of PA reinforcement, loud instrument amps are rather hindering than helping. The times of amp stacks in the back of the band for amplification purposes are IMHO over. Some people might have them for image purposes

IMHO all of the desired overdrive and compression effects can readily be achieved at low power points in the sound chain.
The longer I play, the less distortion I can tolerate. An often quoted rock music protagonist, Jimi Hendrix, did, contrary to common believe, play with pretty little distortion.

have fun,

--helmut

DougH · Post by **DougH** » 25 Aug 2010, 12:00

aquataur wrote: The longer I play, the less distortion I can tolerate.

Me too. But I also like my amp up loud without a lot of distortion. Louder always sounds better to me.

FWIW, I've tried reamping and agree it is probably the best route to go if you have to turn down to a low volume level. It works really well, more effective than other methods. Still, I have found that no one particular method does everything for me. It's usually a combination of different things that works the best.

mistermikev · Post by **mistermikev** » 27 Aug 2010, 17:37

I'm not really looking for massive amounts of more distortion... just a hair more breakup at a lower volume.
Ultimately, the problem is my amp is too powerful, and I probably should focus there.

The prob I run into is ideally I'd like a 2-5watt amp with spring reverb and an fx send/ret and two channels and doesn't cost more than say $400 - is that asking too much?

phatt · Post by **phatt** » 29 Aug 2010, 13:58

mistermikev wrote:I'm not really looking for massive amounts of more distortion... just a hair more breakup at a lower volume.
Ultimately, the problem is my amp is too powerful, and I probably should focus there.

The prob I run into is ideally I'd like a 2-5watt amp with spring reverb and an fx send/ret and two channels and doesn't cost more than say $400 - is that asking too much?

Maybe look at some pedals? Some can do the *small amout of breakup* trick quite well.
Even TS type circuits can be made to produce what you ask. Just thowing other ideas around

Phil.

mistermikev · Post by **mistermikev** » 30 Aug 2010, 16:34

oh, I've got pedals on top of pedals... but they all sound better with the amp at about 3 while the pedal is boosting the front like crazy... and a boosted 3 on a 60watt 4x10 hot rod deville is likely to get the cops to my door sooner or later.

I went to gc this weekend and fell in love with the blackstar stack they had... has fx send/ret... no rev but has a good clean sound and wow... that drive channel is off the hook! Not sure if the 'middle ground drive' settings are all that great but the amp would be worth it for the heavy sound alone...

I dunno... I've changed amps so many times in the last 6months!