Making a line out box to use on a valve amp

[Christophano]

Hey there chaps!

I was wondering if anyone had made a line out box on here? The sort I'm thinking of is one that would 'tap' in between the amplifier and speaker.

Like this one here.... [url="http://www.diyguitarist.com/GuitarAmps/LineOutBox.htm"]http://www.diyguitarist.com/GuitarAmps/LineOutBox.htm[/url]

Although I would hard wire it in and screw the box to the inside of my old WEM Dominator 45 Bass. I thought something like this would come in handy for recording and putting the old girl in to my main bass rig to amplify it.

Any thoughts? Good or bad idea?

[The Funk]

You can buy various things like this. I've heard they work quite well.

[joegarcia]

Like these?

[url="http://www.dv247.com/studio-equipment/hughes-and-kettner-red-box-classic-guitar-cabinet-simulator--31912"]http://www.dv247.com/studio-equipment/hugh...imulator--31912[/url]

[Bill Fitzmaurice]

Have a good tech install an XLR out. He only has to tap both sides of the inverter stage, capacitor isolated and resistor padded, with an output level pot for good measure. You probably don't understand a word of that, a good techie will.

[Mr. Foxen]

[quote name='Bill Fitzmaurice' post='1067837' date='Dec 23 2010, 03:14 PM']Have a good tech install an XLR out. He only has to tap both sides of the inverter stage, capacitor isolated and resistor padded, with an output level pot for good measure. You probably don't understand a word of that, a good techie will.[/quote]

Won't this give you a preamp out only, whereas between speaker and amp will give the tone colouration from the power stage also?

[Bill Fitzmaurice]

[quote name='Mr. Foxen' post='1067877' date='Dec 23 2010, 10:59 AM']Won't this give you a preamp out only, whereas between speaker and amp will give the tone colouration from the power stage also?[/quote]Power stage coloration is minimal, especially when compared to that of the speaker. If coloration is what you're trying to capture you need a mic.

[umph]

[quote name='Bill Fitzmaurice' post='1067837' date='Dec 23 2010, 03:14 PM']Have a good tech install an XLR out. He only has to tap both sides of the inverter stage, capacitor isolated and resistor padded, with an output level pot for good measure. You probably don't understand a word of that, a good techie will.[/quote]
not sure that'd be ideal, most splitters aren't to well balanced. I'd much rather just stick a voltage divider on the output and a transformer if you want the balanced output

[Mr. Foxen]

When I say 'colouration' I mean 'distortion'.

[Christophano]

[quote name='Bill Fitzmaurice' post='1067837' date='Dec 23 2010, 03:14 PM']Have a good tech install an XLR out. He only has to tap both sides of the inverter stage, capacitor isolated and resistor padded, with an output level pot for good measure. You probably don't understand a word of that, a good techie will.[/quote]

Yep, I'm with you, still learning so you will have to bare with me....

Would I be right in assuming that when you say the inverter stage, that's the preamp stage? So you are suggesting tapping it with a balanced XLR with appropriate cap and resistor to drop and power down to a suitable level?

That is sort of what I had in mind, but wanted to try and tap the amps raw sound after it had travelled through the EL84's, which is why I was asking about tapping in between the amp and speaker. I could then potentially use my bigger rig to amplify it. It's also something I could easily do myself while the amp is now in bits as I'm replacing the valves, and pots etc.

Thanks for your input on this.

Chris

[umph]

[quote name='Bill Fitzmaurice' post='1068119' date='Dec 23 2010, 07:16 PM']Power stage coloration is minimal, especially when compared to that of the speaker. If coloration is what you're trying to capture you need a mic.[/quote]

i disagree, the coloration of power valves is worth capturing, the added harmonics and compression of power pentodes/tetrodes is very different to that of the smaller triodes and that coupled with the limited response and added distortion of the power transformer gives a notable difference that gives even more noticible as you crank it, especially with an amp like the one the OP is using.

[umph]

also,

[url="http://www.charlestongolf.com/lineout/"]http://www.charlestongolf.com/lineout/[/url]

[url="http://web.archive.org/web/20050627183340/home.cfl.rr.com/dbhammond/Firezog.gif"]http://web.archive.org/web/20050627183340/...ond/Firezog.gif[/url]

hope these are useful, and i'd also make sure the dummy load is rated for atleast 50 continous watts.

[Christophano]

Thanks for that Umph, you are a useful chap to have around! :-) :-)

Cheers chaps.

[Bill Fitzmaurice]

[quote name='Christophano' post='1068247' date='Dec 23 2010, 04:11 PM']Yep, I'm with you, still learning so you will have to bare with me....

Would I be right in assuming that when you say the inverter stage, that's the preamp stage? So you are suggesting tapping it with a balanced XLR with appropriate cap and resistor to drop and power down to a suitable level?

Chris[/quote]Yes. On your schematic you'll find the inverter tube just before the power amp tubes. It inverts the signal 180 degrees to drive half the push-pull, while the other half is driven by the pre-inverted signal. You tap the input and output, DC isolate both taps with a 0.1uF 400v cap, pad it with 100kohms of resistance, run it through a 1meg stereo audio taper pot, send that to the XLR out.
[quote]the added harmonics and compression of power pentodes/tetrodes is very different to that of the smaller triodes and that coupled with the limited response and added distortion of the power transformer gives a notable difference that gives even more noticible as you crank it, especially with an amp like the one the OP is using.[/quote]It still has an order of magnitude less coloration than that delivered by the speaker. If you want the same tone going to the desk as you hear out of the rig only a mic will give it.

[MythSte]

Umph and Mr Fitzmaurice,

Careful, I fear if you two argue the world will fall deaf, or something. I like big glowing tubes.

That is all.

[Christophano]

[quote name='MythSte' post='1068475' date='Dec 24 2010, 06:07 AM']Umph and Mr Fitzmaurice,

Careful, I fear if you two argue the world will fall deaf, or something. I like big glowing tubes.

That is all.

[/quote]

Valve war FTW!

[paul_5]

[quote name='Christophano' post='1068506' date='Dec 24 2010, 08:50 AM']Valve war FTW![/quote]

Looks like we've got ourselves a good, old-fashioned "Tech-off!". YeeeHaaaaw!

Merry Christmas all!.

[Stewart]

Why not just use a DI box (one with a 30 or 40dB pad - there are several) hanging straight of the speaker output ?

[Mr. Foxen]

[quote name='Stewart' post='1068561' date='Dec 24 2010, 10:13 AM']Why not just use a DI box (one with a 30 or 40dB pad - there are several) hanging straight of the speaker output ?[/quote]

It will make the impedance on the output transformer very unhappy.

[Bill Fitzmaurice]

[quote name='Mr. Foxen' post='1068677' date='Dec 24 2010, 07:42 AM']It will make the impedance on the output transformer very unhappy.[/quote]
Only if run alone, and that would be a very bad idea. I always loaded my amps with a direct out to eliminate having to carry another piece of gear, and the DIY cost of adding one came to way less than buying a box.

[the_brow]

Radial JDI is your friend. I have used it as a speaker level DI with many amps and it works really well. Just connect the speaker out of the amp to the JDI input, then the thru put from the JDI to your cab. XLR out from the JDI to the board. Easy and painless.

[Phil Starr]

[quote name='Bill Fitzmaurice' post='1068119' date='Dec 23 2010, 07:16 PM']Power stage coloration is minimal, especially when compared to that of the speaker. If coloration is what you're trying to capture you need a mic.[/quote]


[quote name='umph' post='1068325' date='Dec 23 2010, 10:40 PM']i disagree, the coloration of power valves is worth capturing, the added harmonics and compression of power pentodes/tetrodes is very different to that of the smaller triodes and that coupled with the limited response and added distortion of the power transformer gives a notable difference that gives even more noticible as you crank it, especially with an amp like the one the OP is using.[/quote]

I too love a tech war but the truth is that both are completely right. Bill's method will give you a post fade post tone shaped output. A DI box in the speaker line gives you the shaping caused by the output stages, which is the bit of the valve sound we still can't quite capture any other way but the speaker introduces a whole other level of distortion/sound shaping.

It all depends upon what you want: clean and you DI before the amp, clean but with you retaining tone shaping, go for the BFM method, DI off the speaker lead and you get the valve distortion and tone settings. Mic' up and you get total control at the expense of a lot more fiddling and the expense of a mic.

I'd go for the DI box personally, just because I don't like the idea of fiddling too much with classic old amps and I'm happy for an engineer to fiddle with my sound. That's just personal preference though.

Edited December 27, 2010 by Phil Starr

[TomTFS]

I think the best and EASIEST way to get the full tone, is a DI pre everything, and a Mic on the cab. Just as you would get at most gigs.
The DI picks up the raw sound and is generally used to get nice clean bottom end and the Mic picks up the actual sound of the bass.

It's the industry standard method for a reason.


Edit: Forgot to add, if you're in a venue that's not mic'ing the cab up, it generally means that either:
a.) Your sound Engineer is lazy.
b.) The venue is small enough that there will be enough sound coming from your cab to fill out the sound anyway. you would be surprised quite
how much noise from a cab can still be heard over some of the loudest PA's.

Edited December 27, 2010 by TomTFS

[umph]

[quote name='Phil Starr' post='1069937' date='Dec 27 2010, 08:53 AM']I too love a tech war but the truth is that both are completely right. Bill's method will give you a post fade post tone shaped output. A DI box in the speaker line gives you the shaping caused by the output stages, which is the bit of the valve sound we still can't quite capture any other way but the speaker introduces a whole other level of distortion/sound shaping.

It all depends upon what you want: clean and you DI before the amp, clean but with you retaining tone shaping, go for the BFM method, DI off the speaker lead and you get the valve distortion and tone settings. Mic' up and you get total control at the expense of a lot more fiddling and the expense of a mic.

I'd go for the DI box personally, just because I don't like the idea of fiddling too much with classic old amps and I'm happy for an engineer to fiddle with my sound. That's just personal preference though.[/quote]

Personally my ideal solution would to be to get the transformer rewound with a 600ohm balanced line out. Isn't cheap though and can make for a super hot output if not attenuated properly

[sshorepunk]

Never tried one, but our guitarist uses it. JDI was mentioned earlier, this is the exact one if you want all the valvey goodness from the power stage I guess

[url="http://www.radialeng.com/re-jdx.htm"]Radial JDX[/url]

Anyone else used one?

Tony

[Christophano]

Interesting stuff bheys.

After considering the comments, I have started ordering bits to make a Firezog Line out box. It will incorporate a switch to shut the speaker off and a 100w 8ohm dummy load so I don't fry the thing!

I'm not in to spending loads of money of stuff if I could actually make cheaper while learning about it.

Will post up if/when I get it working!