Dummy Loads

DELANEY · Post by **DELANEY** » Sun Jan 22, 2006 3:36 pm

I don't have a schematic of my attenuator yet. But here is the most important part.

http://www.starkelectronic.com/12.htm#7row

My design is only for a 50 watt amp. I know I have more capability, but seeing how hot it gets, I would keep at 50 or under. You could add more series/parallel networks to look like more cabs and dissapate more heat.

It is a 100 watt Mono 8 Ohm LPAD. If you hook it up, according to its instructions, no matter what the output of the speaker is, it keeps a constant 8 to 9 ohms out. I just placed placed a 16 Ohm 35 watt resistor in parallel to the 16 Ohm speaker, to satisfy its need for seeing 8 Ohms. I placed anther 8 Ohms in series with that by paralleling two more 16 Ohm resistors. I basicaly copied the way a 4x12 is wired, substituting 16 Ohm 35 watt resistors to keep the dissapation close to four 30 watt celestions. The beauty of this is that I also use a 30 watt Eminence RED Fang.

I have a theory that the dissapation accross speakers is somehow important. Not the Make or the Model.... Just keep it around 30 watts per 5o watts of rated tube power.

That's the problem, I think with having a 100 watt amp. It calls for a full stack to get the tone. Really maybe a stack and a half.

When I juice my 100 watt 2203 through halfstack of 25 watt blackbacks, I feel like I'm gonna blow the cones. I like the sound of my 30 watt speaker when its seeing about 70% of its rated dissapation.

bmf5150 · Post by **bmf5150** » Sun Jan 22, 2006 4:48 pm

interesting,thanks!

bmf5150 · Post by **bmf5150** » Sun Jan 22, 2006 5:53 pm

does the other resistors go before or after the l pad?

Billy Batz · Post by **Billy Batz** » Sun Jan 22, 2006 7:44 pm

Thats my reservations about getting the 12Ms. I know 80% of the time Ill be using an attenuator with them and I wont be working them so hard they start to really fall apart and break up too much. But that leaves me kind of flat when I want to run the amp full out and I only have one cab that is underpowered.

rockstah · Post by **rockstah** » Sun Jan 22, 2006 9:21 pm

same here Dan - infact if i was to commit to the 20w g12m's i would
need two cabs for sure. im thinking that even with these 12m 25w blackbacks i have. but then what ? i wish i liked the voice of the 30watters

Billy Batz · Post by **Billy Batz** » Sun Jan 22, 2006 9:33 pm

Dont you?

908ssp · Post by **908ssp** » Sun Jan 22, 2006 10:06 pm

You fret the sound of a capacitor then you put a poor sounding attenuator between it and the speaker?

Sorry guys I don't get it. If it cost $400 to get a really transparent sounding attenuator then sign me up.

Oh yea, you don't have to I already bought one.

Del's home made attenuator is made the same way as Weber load Dumps they don't sound horrid just weak and if it was the only alternative I could afford I would go with it in a second. But if you want a better one they are out there.

DELANEY · Post by **DELANEY** » Mon Jan 23, 2006 12:12 am

908ssp wrote:You fret the sound of a capacitor then you put a poor sounding attenuator between it and the speaker?

Sorry guys I don't get it. If it cost $400 to get a really transparent sounding attenuator then sign me up.

Oh yea, you don't have to I already bought one.

Del's home made attenuator is made the same way as Weber load Dumps they don't sound horrid just weak and if it was the only alternative I could afford I would go with it in a second. But if you want a better one they are out there.

I have some questions Alex,

..And yes it is as simple as a load dump. The theory is simple, except you missed that I am trying to keep the same dissappation as a 16 Ohm 30 watt speakers in a 4 x 12 cab. Do you own or have owned a load dump? I have not, so I can't say how it could compare.

But I really don't think it sounds poor, do you think my clip sounds poor?
Why is my attenuator Weak?

Maybe you can elaborate? Please explain why a 400$ attenuator can sound better. I enjoy this kind of explinations beacause they flat out escape me.

Better yet, please post a clip of your amp with the uber-attenuator. I am ready to be impressed. Surely a transparent sounding $400 attenuator should sound omnipotent compared to my cheap homemade job.

I offer My Clip On a CHEAP $25 Attenuator for comparison

Billy Batz · Post by **Billy Batz** » Mon Jan 23, 2006 12:26 am

The clip thing can only really prove that someones better at makign clips provided you agree that neither attenuator will make the amp sound absolutely horrible. If I could try them both in person I would. Its cool your load works for you. The main thing I think I shouldve pointed out from the start Del is I need my attenuator to serve multiple functions- a) adjustable betwen slight stage attenuation and, b) higher home attenuation, c) load for working on the amps, finally, d) a line out along with the load for slave/reamping setups when/if thats needed. The production units do those things. Some of them anyway and $225 for my mass wasnt a lot to pay to have those things. Im sure I couldve built it but hell....

908ssp · Post by **908ssp** » Mon Jan 23, 2006 12:42 am

Dan for the longest time I argued that any attenuator was better then no attenuator unless you had a Maven Peal. But not every amp was made with wattage control and I wanted to play vintage gear. So I bought and experimented with attenuators. My findings are pretty much what most people report that have had more then one attenuator.

Some sound better on one amp then another.

They don't sound bad if you turn down only 3 to 6 db after that they get progressively worse. You can compensate somewhat by adjusting your amp if your amp has any adjustment left.

The tone changes because the highs and lows decrease. There are some good articles on Aiken's site explaining the phenomenon with graphs and an explanation of a means of fooling the amp into not changing tone for testing purposes. He does not follow through with that train of thought and suggest that a similar approach might be used in an attenuator. But that is what Motherload did with the Richter.

Your explanation about impedance is correct to a point. The impedance rating of a speaker is done at 400hz. When measured at 0 Hz or DC it is lower and when measured at 5000 HZ it is much higher 5 to 8 times as high, your load can't do that and that is what makes the tone and feel change. It would not surprise me at all if you need that change to get a good Eddy sound.

By the way your clip sounds great, I wish I could play like that.

Billy Batz · Post by **Billy Batz** » Mon Jan 23, 2006 12:52 am

I get by enough that I dont think Ill ever get a richter or another attenuator but your review has me very interested.

DELANEY · Post by **DELANEY** » Mon Jan 23, 2006 1:01 am

Billy Batz wrote:The clip thing can only really prove that someones better at makign clips provided you agree that neither attenuator will make the amp sound absolutely horrible. If I could try them both in person I would. Its cool your load works for you. The main thing I think I shouldve pointed out from the start Del is I need my attenuator to serve multiple functions- a) adjustable betwen slight stage attenuation and, b) higher home attenuation, c) load for working on the amps, finally, d) a line out along with the load for slave/reamping setups when/if thats needed. The production units do those things. Some of them anyway and $225 for my mass wasnt a lot to pay to have those things. Im sure I couldve built it but hell....

To be honest, I can buy them if I wanted, I was gonna buy a mass for my JTM45. But I had a couple of parts around... ta da.

I built mine with a line out too, but really I have DI boxes going to low Z for I said screw it. But I don't hink a normalized line out works as good as a good recording mic. I understand what you want, and it seems like you got it together.

The real answer for home (recording) playing in the middle of the night when the fams in bed, is to build a closed speaker box, with a mic on one end. It could by about 15x15x30 out of High density composite materials. Put alot of padding inside, and put a nice alnico in there. I recorded kind of that way. Now I just toss alot of padding around a 1x12 and stick it in a closet with a long speaker cord and a Large Diaphram Mic. I can barley hear it, but I run the headphones into the mixing board, and I can hear the sound, and make my adjustments on my amp and attenuator. Works like a champ, I'm gonna build a permenant one soon.

Your right about only proving I can make a decent clip. I realize that the recording aspect is hard enough to master much less make and amp sound good and play guitar fairly decently... I knew it was a curved ball when I pitched it

Billy Batz · Post by **Billy Batz** » Mon Jan 23, 2006 1:07 am

Ive thought a lot about iso boxes in the past. Ive just never taken the step into seriously considering them.

Im not using the line out for DI BTW. I use it to send to a poweramp I have around here. It works 1000x better then high attenuation for extremely low cranked volume. I dont have a UA but I can see why there so good at low volumes since their a load-poweramp type deal. Ive never gotten a recorded DI sound from one of my amps I can live with.

DELANEY · Post by **DELANEY** » Mon Jan 23, 2006 1:19 am

You know I often thought about getting a bunch of dead speakers and ganging them together, and insulating the cones so I could get the real reactive load reflected back to the amp. Now that has got to be transparent!

I look at recone shops and lots of them are unloading Vintage 30's cause they can't get the recone kits for them. I saw one guy selling 8 for 30 bucks plus shipping.

Billy Batz · Post by **Billy Batz** » Mon Jan 23, 2006 10:23 am

Thats what the MASS is only Weber uses one large speaker motor.