Does a tube amp need a load or can you record straight into a computer?

[Passinwind]

take the pre-amp out, or effects loop out.

In the manual it would say if this cuts off the signal to the power amp.

IME it's much more common in tube guitar heads for the power amp cutoff (if any) to happen at the power amp input jack. In which case, rather than just plugging an open plug in there to break the circuit, a shorting plug (T-S plug with both connectors wired only to each other and plugged into the power amp input jack) is an added measure of protection against hurting anything in the power amp section, when used with a load of some sort on the output transformer side as well. Without knowing what amps or what styles of music are involved it's impossible to guess if the guitarist in question will dig the results though.

 

[bassmandudeguy]

Ok guys thanks for all the awesome replies! This has been very edukashanil!
(How do you guys do the multiple quotes in one reply thing??? I WANT to be an elite poster too!)

@ Seamonkey: In post #11 you stated that your advice is only half idiot proof! Well... as a matter of fact I'm exactly 51% idiot & only 49% idiot savant so... I'm GOOD TO GO RIGHT!?
Oh and thanks for the vote of confidence in my... ability to know more then John D! Unfortunately it's just a ruse. I've been masquerading as a smart person for years. I'm pretty sure John D's wisdom surpasses my own on this topic!

@Passinwind: Ya man thanks for the advice. I was thinking if we did try this we would get our recording signal from either the direct out(if it had one), or the preamp. Also on an unrelated note: I dig ur comment under your avatar pic! I know nothing too! No, but seriously I listened to ur sound clips from your band and I started dancing like a funky chicken on accident! Good stuff bro! Props!

@bassybill: Ya man I lol'd at that too! That'd be a good sig if Stingray is would sign off on that for me! Woot! Btw the band is YOUR sig is DOPE! It reminds me of my highschool Jazzband... except you're band is precisely 9217% better then we were!

@Stumbo: That Tubecube is sweeeet dude! I didn't know something like that even existed! IF this was MY situation I would definitely think about picking one up, however it is my little brother, the broke ass school teacher with a wife and kids, that is having the problem so I'm recommending him to just MIC his cab and go into the Focusrite interface to record.

Anyways thanks for all the suggestions guys! I'm still trying to get the exact information of the amp he's using. I've left a couple messages etc... not sure what his deal is. I'm quite certain he didn't erase as many brain cells as I did last night and I still woke up early got my kid ready for school and am functioning. Well sortof lol, I think that last case of beer might have been one too many!

 

[Passinwind]

(How do you guys do the multiple quotes in one reply thing??? I WANT to be an elite poster too!)

For each post that you want to include, hit the multi-quote button just to the right of the quote button. It'll light up in red, check it out.

Once you've done that on multiple posts, hit "reply" either on the last post you're quoting or at the bottom of the thread. You should now see all the selected posts you want to respond to, with the author's name and post number at the top of each one.

Cut out all the parts you aren't responding to, and place your individual responses under each quoted part.

Profit!

Best of luck, and post more details if you get 'em.

 

[gigslut]

For each post that you want to include, hit the multi-quote button just to the right of the quote button. It'll light up in red, check it out.

Once you've done that on multiple posts, hit "reply" either on the last post you're quoting or at the bottom of the thread. You should now see all the selected posts you want to respond to, with the author's name and post number at the top of each one.

Cut out all the parts you aren't responding to, and place your individual responses under each quoted part.

Profit!

Best of luck, and post more details if you get 'em.

So that's how you do it! Thanks for the tip.

 

[bassmandudeguy]

Oh I didn't see your last comment Passinwind as it was on the second page. Ya I don't know a lot about tube guitar amps except how to identify the really heavy ones from when I was poor roadie lol!

I could probably just make a shorting plug out of and old cheapy plug instead of buying one right? I'm sure my crappy soldering skillz can manage that!

As far as the music.... original stuff somewhere in the realm of Mogwai meets Deathcab for Cutie meets with some Machine Head and Puscifier type stuff. Kinda random band selections there.... we're all over the place in regards to influences. Pretty much we're into anything rock I guess.

 

[Passinwind]

Oh I didn't see your last comment Passinwind as it was on the second page. Ya I don't know a lot about tube guitar amps except how to identify the really heavy ones from when I was poor roadie lol!

I could probably just make a shorting plug out of and old cheapy plug instead of buying one right? I'm sure my crappy soldering skillz can manage that!

Sure, it's a fine way to recycle an old one. May not be strictly necessary in many cases, but think of it as cheap insurance. I used to run one of my guitar amps that way pretty often for both live and recording purposes, but it definitely yields a different sound than also using the power section does.

 

[bassmandudeguy]

For each post that you want to include, hit the multi-quote button just to the right of the quote button. It'll light up in red, check it out.

Eureka! Can't believe I never noticed that button before!

So that's how you do it! Thanks for the tip.

Yea! What he said!

Sure, it's a fine way to recycle an old one. May not be strictly necessary in many cases, but think of it as cheap insurance. I used to run one of my guitar amps that way pretty often for both live and recording purposes, but it definitely yields a different sound than also using the power section does.

Cool. Yea I'll try that next time the soldering iron is out. I'm ok with different. Variety is the spice of life afterall... or that's what I read somewhere anyways!

Thanks again!

 

[CrewsControl]

3) Some solid-state amps let you run without a load, but I don't believe in solid-state amps, so I'm no expert there.

They exist. You can trust me on this one.

 

[Passinwind]

Thanks again!

No worries, but I'd still like to hear what amps your bro is using and make sure he gets things dialed correctly.

 

[bassmandudeguy]

Ya man totally! When I know something, you'll know something! Actually I'll call that tard again right now! Peace.

 

[albertofrog]

Ok. heres the technical reason.

If you want it....

remember Ohms law (V/Z=I) (or voltage divided by impedance equals current)

The output voltage of the power amp tubes is passed through the input coil (primary) of the transfomer and then down to ground.
Practically, the transformer input coil is nothing but a coil of wire, and has no impedance, but due to an effect known as "reflected impedance" it can "see" the impedance that is connected to the output coil (ie the speaker).

so an output transformer with say, 8 ohms load will be seen as approx 8000 ohms (quite enough to limit the current from a power amp tube)

so as an example:

300V on the tube anode divided by 8000 ohms reflected impedance of the speaker = 0.0375 amps. (37mA is fairly normal for a tube current)


However....

if you disconnect the speaker, then the impedance on the output of the transformer disappears, so there is no impedance to reflect.

therefore the "reflected impedance" in the transformer primary disappears and it becomes nothing more than a piece of wire again.


so as an example:

300V on the tube anode divided by 0.1 ohms resistance of a piece of wire = 3000 amps.

...and that is deinitely going to either blow all your tubes or overheat and melt the output transformer...


Now the reason this applies to tube amps and not solid state amps is very simple.

A tube works by amplifiying voltage, so the load is in parallel with the tube.

A SS amp works by amplifying current, so the load is in series with the output circuit of the transistor, so when the speaker is disconnected, it open circuits the output stage, and cuts of the current, so is self limiting.


sorry if thats not too clear, just off the top of my head...

 

[seamonkey]

Heard, read, seen people experience all that almost backwards.

Ohm's law is OK. It's "Impedance" of an AC circuit.

However....

if you disconnect the speaker, then the impedance on the output of the transformer disappears, so there is no impedance to reflect.

So a load means something is there. Nothing there is no load, and open load.

The output impedance with an open load goes to infinity.

Back to ohms law, in any circuit to get the same power with higher impedance's you need higher voltage.

Keep the power the same in your ohms law equations but double the impedance. The voltage goes up.

therefore the "reflected impedance" in the transformer primary disappears and it becomes nothing more than a piece of wire again.

With no load the output impedance is very high, like hitting a brick wall. The impedance on the tube side is like hitting a reinforced brick wall.

Signals coming in hit the wall and reflect back. " Flyback voltage" You have a gas engine ignition coil and high voltage arcs in the tubes or across the transformer windings.

As mentioned before some amps with 1/4" shorting jacks - short the output when no speaker is connected.

If the 1/4" jack shorts the output, then the reflected impedance is also 0 ohms. 0 times anything is 0. It can't develop ac signal voltage across the transformer. Sure tubes can blow from the DC current, but not likely the output transformer.

If no signal is sent to the power amp, then no "AC" impedance funny stuff can happen.

Don't believe me, go check your friendly neighborhood internet.