Ohmage

[Celestial]

Hi, im in a bit of a pickle... lets say an amp is 150 w RMS and has switches 2,4,8 and 16 ohms (Sunn Model T) and an attenuator that is 100 w at 8 ohms only (Palmer PDI-03).. how can i set them without frying something... (without pulling 2 tubes out)

Can i somehow make it work or its a dead on no no?


Thanks in advance!

[Celestial]

Or maybe i can use two attenuators?One for attenuation and the Palmer for cab simulation... but the thing is that the Palmer is a passive device... how would that work? IM CONFUSED!I really want that Palmer PDI 03 speaker sim circuit sound for silent recording... how can i make it work now?

[kxbx]

You need to run the amp such that it only delivers 100W to the load (the attenuator). So this would mean setting the amp to 8 ohms and keeping the volume low enough that you don't exceed 100W. If you don't have some means of measuring the amps output then this is guesswork, I would keep things at the lowest level that gives you the sound you want.

You could also just use two attenuators.

[subprime]

Additionally, you could ask the guy who will be building the model T clone to just make it at a lower wattage because 150 is really way too high.

[Tommy]

According to the specs it is actually:

"Loadbox input impedance: 8 ohm, max input load: 100WRMS (200W with cabinet)"

So, connect it as follows:

Model T set to 8 ohms ---> Palmer PDI-03 ---> 8-ohm cabinet of your choice.

You should be fine as long as you aren't running it full balls out without a cabinet.

[benadrian]

This setup is pretty much a no go, if indeed you don't want to pull tubes. I'm not familiar with how the palmer works, but there's no way to run the amp at 150 watts and safely use the attenuator. theoretically, you could set the volume low and attenuate that signal. But if a distortion pedal is set too loud, or a knob gets moved, or one of many things happen, the result could be melting the attenuator, melting a tube, or melting an output transformer.

This whole situation seems weird. I'm presuming you already have this head, and now you want to silently record with it? Well, pull two power tubes, make sure the bias isn't running out of control in that state, set the amp head to 4 ohms (to compensate for the two missing tubes), and then you can safely use the attenuator for silent recording.

Also, are you trying to pad down the speaker level to record through the Palmer while simultaneously cranking out through a cabinet?

Do you have the Palmer because of the Black Keys? I think EVH used one, and there was a run on them. Every so often some popular guitarist uses one, and they get popular for a couple years, and then they fade out until the next big time dude gets seen with one

[subprime]

I dont understand the desire fo the palmer. But he gets a good bass sound with an MXR DI so whatever.

[benadrian]

I don't mean to knock the Palmer. It seems like it does what it does very well. It's a complicated and very specialized device. I don't know how it fits here.

If he wants to crank a bass though an amp, and the volume is needed, then miking the speaker seems easy enough. If silent recording is desired, then pulling two tubes and using the attenuator and Palmer will work.

I'm just a pragmatist, so I want to know why these choices were made to make sure the planned setup most efficiently meets the needs of the desired sonic result.

[subprime]

He lives in an apartment so he can't crank the amp. He would be using it for guitar primarily I believe.

[benadrian]

Then pull two tubes and use the attenuator for apartment only. Or, look for some direct recording device for apartment only, or look for a cool, small amp for recording.

Using a cranked amp with an attenuator will make a good space heater! I've never really enjoyed the tone of attenuated amps, though.

[subprime]

Well, the thing he wanted about the palmer was the fact that it was both attenuator and DI/cab sim I think (unless I'm mis remembering)

[Celestial]

So many replies! Thanks Lucas for answering some questions for me!

Uhm yeah pretty much spot on... i want to use it in an apartment silently as a cab simulator.I like the Palmer cause everyone is raving about it... i got the impression that its the closest simulator to a real cab.But yeah its a dummy load as well so... silent recording.

How much would the sound change if id mod the amp for 100w usage... or thats effectively just a switch for bypassing 2 tubes?

[ldopa_chicago]

You could mod the amp for 6L6s or something and rebias it so that you get <100W out of it, but I'd just do what benadrian said and pull two tubes (the right two! ask if you don't know!), change the output impedance to the 4Ω setting and run that into the Palmer. It'll sound "different," but then again, so will running that amp into the Palmer in the first place. I'd recommend eventually getting anther amp or a Rusty Box/Sansamp for apartment use.

[subprime]

He doesnt have the amp yet, hes getting it made by a guy for a good price. Seems easier to just get it made at the lower wattage given that. I suggested getting the guy to add a variable wattage switch from 150/100/50 so he could use it for both bass at 150 and guitar at 50 or 100.

[Celestial]

Again, its for guitar use... how does rusty box or a sansamp help me with anything here? And the Sunn is THE TONE i want... nothing else frankly has that sound.Il just pull two tubes then! Or yeah... the variable wattage switch... thats a very good idea!

[Celestial]

And 6l6s sound NOTHING like 6550!

[benadrian]

He doesnt have the amp yet, hes getting it made by a guy for a good price. Seems easier to just get it made at the lower wattage given that. I suggested getting the guy to add a variable wattage switch from 150/100/50 so he could use it for both bass at 150 and guitar at 50 or 100.

That's not exactly an easy or sonically pleasing thing to do.

To my ears, pulling two tubes is pretty damn close. You will lose some transformer saturation, if indeed you are running the amp loud enough to cause transformer saturation with all four tubes. That would be face meltingly loud in the case of a Model T. Other than that, there's not much that can tonally change. The bias of the remaining two tubes will be affected, but probably no so much as to make the amp sound bad.

[subprime]

He doesnt have the amp yet, hes getting it made by a guy for a good price. Seems easier to just get it made at the lower wattage given that. I suggested getting the guy to add a variable wattage switch from 150/100/50 so he could use it for both bass at 150 and guitar at 50 or 100.

That's not exactly an easy or sonically pleasing thing to do.

To my ears, pulling two tubes is pretty damn close. You will lose some transformer saturation, if indeed you are running the amp loud enough to cause transformer saturation with all four tubes. That would be face meltingly loud in the case of a Model T. Other than that, there's not much that can tonally change. The bias of the remaining two tubes will be affected, but probably no so much as to make the amp sound bad.

How would some sort of variable wattage switch change the overall sound? Seems to work well enough in stuff those orange terrors with the 7/15/30 switchs.

[benadrian]

How would some sort of variable wattage switch change the overall sound? Seems to work well enough in stuff those orange terrors with the 7/15/30 switchs.

Well, 30 to 15 is going from four tubes to two tubes. That's pretty sonically close. The 15 to 7 watt switch switched the B+ voltage. This works because Orange has a custom power transformer made with multiple secondary taps for different internal voltages. Also, the amp is cathode biased, so it will self-bias somewhat when the B+ voltage is changed.

The big thing about this, though, is that the sound of the power tubes change when the B+ voltage is lowered. The tone gets darker, and the playing response feels slower. It's not that it gets that much quieter as much as it distorts sooner as you turn it up.

There are a few different ways to scale power in amps. Some involve lowering the B+ like above. We have a Morgan amp here at my work that does this. Some switch from pentode to triode. Some just involve big resistors/speaker soaks. In every case, there is a very noticeable tone shift. Pulling two tubes is the least tonally affecting manner to reduce power in my opinion. Also, this can be done with a switch on the amp if it's more convenient than just physically removing two tubes.

[subprime]

thats what I was thinking it would do, just bypass two of the tubes. Seems like the best option.