Circuit design for direct amp recording

[Timeline]

I have been thinking about this for my 65 Princeton reverb amp and want to run it by some of you.

On the rear skirt of the amp I was thinking about adding a box inside that allowed me to interrupt the amp-to-speaker plug and insert a wire-wound pot like a power soak. Tapping off of that I would add a second pot for level adjust to a hefty transformer that would take 50ohms up to 300 and feed it to a male chassis mount XLR also mounted on the back rear skirt.

The transformer would totally iso the amp from ground.

Comments?

[ba_hill]

Hi,

You'll want to make sure that the amp always has an 8 ohm or so load on it. You can damage a tube amp by running it without a proper load on it. If your wirewound resistor is somewhere between 4 and 16 ohms you should be fine. Have you considered using an attenuator that has a line out? Something like the Weber MASS

https://taweber.powweb.com/weber/mass.htm

or THD HotPlate

http://www.thdelectronics.com/products/hotplate.htm

might do the trick. Both of those are designed to present an appropriate load to the amp at all times independent of the attenuator level.

Depending on the sound you're after you may find that you'll need speaker simulation of some kind. The output of an amp without a speaker connected doesn't sound much like what we're used to hearing from an amp. In particular, if you're overdriving the amp it'll sound thin and scratchy without a speaker or speaker simulator.

Brian

I have been thinking about this for my 65 Princeton reverb amp and want to run it by some of you.

On the rear skirt of the amp I was thinking about adding a box inside that allowed me to interrupt the amp-to-speaker plug and insert a wire-wound pot like a power soak. Tapping off of that I would add a second pot for level adjust to a hefty transformer that would take 50ohms up to 300 and feed it to a male chassis mount XLR also mounted on the back rear skirt.

The transformer would totally iso the amp from ground.

Comments?

[Timeline]

Thanks Brain. Yea the Wire Wound pots i have are 8ohms and heafty as hell. Would this be a speaker simulator as you suggest? If not what would a speaker sim circuit look like?

The other option is let the speaker be connected and just take a tap but I wanted total "apartment" noise control.

Didn't want to have to buy a box like you suggested because it's $300+ bucks.

You know, cheap and dirty.

[ba_hill]

Hi,

The wirewound pot won't work as a speaker simulator. The frequency and dynamic response of a speaker is complex. You could do the speaker simulation in software. You could use the speaker simulator from a plugin such as (my favorite) ReValver MkII

http://www.alienconnections.com/products_revalverii.htm

or Amplitube 2

http://www.amplitube.com/

or for less money (i.e. free) you could use some speaker impulse responses

http://noisevault.com/nv/index.php?opti ... cat&cat=18

in a convolution plugin such as the one in SonicBirth

http://www.sonicbirth.com/

or (not free) TriTone Digital's ColorTone-Pro

http://www.tritonedigital.com/product_i ... 66c563e62c

Or you could do the speaker simulation in hardware using a Behringer DI

http://www.musiciansfriend.com/product/ ... sku=150934

It's less flexible than any of the software solutions as it only has one speaker cabinet model (a 4x12) but it does work and it's not bad for the money.

I've tried most of the above and these days I'm using ReValver (not just the speaker sim but the whole plugin) for all my home guitar recordings. If you haven't rejected the possiblilty of using an amp simulator check it out. You may find that it'll give you what you're looking for with less hassle and as good or better results than using an amp/attenuator setup.

Some examples from my experiments:

Amp->Weber Attenuator-> Behringer GI100

http://www.arguslounge.com/~brian/EF86.mp3


Amp->Weber Attenuator->ColorTone-Pro with speaker impulses

http://www.arguslounge.com/~brian/UFmix.mp3

ReValver MkII

http://www.arguslounge.com/~brian/WhyNot.mp3

http://www.arguslounge.com/~brian/RMII_Blue.mp3

I don't know what sort of sound you're after so these may not be useful examples but they are some of the things I've done over the last year or so when testing various methods of recording guitar at home.

Brian

Thanks Brain. Yea the Wire Wound pots i have are 8ohms and heafty as hell. Would this be a speaker simulator as you suggest? If not what would a speaker sim circuit look like?

[oldguitars]

Yep, a DI/line type out of an amp sounds awful unless there a speaker simulator. just get a used pod...

[Timeline]

Well I'm still a bit confused.

If these expensive power soak units work, How do the create speaker sim. They must use some sort of circuitry or is what your saying is they all suck?

I really don't want to use a plugin. I like the real thing if I can figure out a way. Maybe I'll just build a baffel for the amp.

[Phil O]

What about this?

http://www.jensen-transformers.com/as/as068.pdf


This circuit doesn't replace the speaker with a load, but you can always substitute a hefty resistor for the speaker.

The wirewound pot won't work as a speaker simulator. The frequency and dynamic response of a speaker is complex.

Actually, a well designed speaker should look as close as possible to purely resistive over it's operating range. A resistive load will protect the amp from damage and should work fine. The only thing you won't get is the characteristics of the particular speaker you're using. Be sure to use a resistor of adequate power. A fixed resistor will do. I can't see any advantage to using a huge pot. If you need to adjust levels, do it after the transformer with a nice audio taper pot.

Phil

[Timeline]

Yes Phil that's was the circuit I was planning in the original thread. Didn't know Dean did a schematic. Thanks.

[ba_hill]

Power soaks do not sound good for direct recording unless they include a speaker simulator. The Weber MASS does not have a speaker simulator and I don't think the THD HotPlate does either. Direct recording is not their main purpose. Their main use is for taming the volume of an amp when you want to overdrive it but not play so loud. If you use one of them you will still need a speaker sim of some sort for direct recording. There are other devices such as these Palmer speaker simulators

http://palmergear.com/recording_studio.shtml

which are designed for direct recording but they are even more expensive than the Weber or THD power soaks.

Well I'm still a bit confused.

If these expensive power soak units work, How do the create speaker sim. They must use some sort of circuitry or is what your saying is they all suck?

I really don't want to use a plugin. I like the real thing if I can figure out a way. Maybe I'll just build a baffel for the amp.

[markwayne]

I have a bunch of H&K Red Boxes (speaker sim) for this application. Just place it between the amp the power soak. I have also used them live to suplement and/or replace a cabinet mic. I love what they do to the tone of most tube amps.

Wayne

[Timeline]

I have a bunch of H&K Red Boxes (speaker sim) for this application. Just place it between the amp the power soak. I have also used them live to suplement and/or replace a cabinet mic. I love what they do to the tone of most tube amps.

Wayne

This might be the answer I'm looking for. Thanks Wayne, I'll check it out.



Added. This is interesting: http://www.amptone.com/g235.htm

[donreynolds]

I used the h&kred box for a long time. I thought it sounded good. you have 2 or 4 speaker sims select switch. runs on a 9v or ac adapter. You can run it line level or straight out of the amp out before the speaker.

Don