Line out help please

[clinkous]

What would be the best way to add a line out to my AX84 Hi-octane homebuilt amp?AX84_Hi-Octane_101004.pdf

I'm currently using my Peavey Bandit 65 with an EVM12L as the speaker cabinet for this amp. I switch the speaker back and forth between the amps. I would like to try to run a signal from the tube amp into the power amp section of the bandit.

I don't know if tapping off of the speaker output is the way to go as I would like to use the tube amp without a speaker connected. I know the amp needs a load on it. Is there a good way to do this? Should I run it into an attenuator and tap off of the speaker jack or is there a place to insert the line out between the pre and power sections of the tube amp?

Thanks for any suggestions.
Chris

[pdf64]

Tube amps tend to have a far more pleasing response when driving a real speaker, rather than a load resistor.
A speaker has large changes in impedance against frequency, resulting in a bass and treble treble boost, as the amp's output tracks the impedance.
Whereas a resistor just gives a flat response.
So I suggest getting another speaker for the AX84, maybe just a cheap, low power 10".
The line out can then be taken from a potential divider across the speaker output, eg ~10:1, so 10k - 1k or http://bmamps.com/Schematics/fender/30_schem.pdf

[clinkous]

Thanks pdf64!

I'll keep the speaker involved and just come off the output and see how that works.

[Justin Thomas]

I've used that line out system (off the OT 2ndary) for years, and no one has ever complained about it being noisy or problematic. That said, I use it as a SUPPLEMENT to the speaker in the room, or (as right now) to feed to a board so some live streaming folks online can hear me in the mix. I will say in full disclosure I've never heard the results with my own ears, cuz I have a roaring live amp behind me, but like I said, no complaints about "signal to noise" ratio or any hum or buzz or what not. A Jack & 2 resistors - cheap, effective, easy. I like it.

This is a good thread, and also a W/V/I chart to help with the math, c/o Enzo, I believe:

http://music-electronics-forum.com/t10582/

Justin

[Chuck H]

Justin,
Thank you for linking one of my many posts on the "line out" subject. I thought I was going to have to write the whole damn thing again

Seriously though, I usually 'suggest' a forum search in these cases. Rather than spoon feed the info ad nausiam. Sometimes I'll link. But if the info is easily sourced with a forum search I usually don't. Give a man a fish and he'll eat for a day. Teach a man to fish and he'll eat for life

[Justin Thomas]

I haven't yet figured out how to master the "search" function yet, so if anyone would like to repost the instructions for doing it via Giggle again, that'd be great... I still get frustrated on occasion, but I know "kingston" brings that one up!

I'll let em figure out how to use the chart... I've used four different versions of the same line out, so... Have yet to install an adjustable, though - no room for a pot or knob.

Justin

[Leo_Gnardo]

I haven't yet figured out how to master the "search" function yet,

No pro searcher here neither, but in trying I came up with another interesting line out thread McGruff started. Chuck, Ginger & Patlaw had good responses, worth a read:

http://music-electronics-forum.com/t39075/

[olddawg]

Honestly... Unless I use an active DI box I have problems with ground hum every time I try to use a speaker signal derived line out. I tried to use the the line out on my Weber Mini Mass directly into a big Mackie board at my last gig. I gave up and just miced the amp with an SM 58. Having a little of the guitars in the main mix helps prevent an imbalance when standing in one side of the room or another.

[clinkous]

Thanks for the links. Thanks for spoon feeding me as I'm hungry and a lousy fisherman! I promise I tried to search first but it seems I can't find anything until after I post....then it seems to come out of the woodwork.

I certainly appreciate everyone's time spent on any of my posts.

Chris

[Leo_Gnardo]

I certainly appreciate everyone's time spent on any of my posts. Chris

And I appreciate you saying that sir. I'm sure others do as well. Together, we can learn. Because of your post I've sharpened my search skills, not a lot, but every little bit helps. Thank you! LG

Honestly... Unless I use an active DI box I have problems with ground hum every time I try to use a speaker signal derived line out.

While we're mentioning active DI - those with some $$ can find H-K's "Red Box", which does a nice job taking an amp's line out and turning into a signal that reasonably resembles an SM57 mic on a Celestion speaker, at least that's what they claim. Dunno if they're still made but they were about $100 late 80's. Also Rocktron's single rack mount "Juice Extractor", includes about 100W of load resistors plus a DI out with characteristics similar to the Red Box. Also also Groove Tubes had theirs too - sorry I forgot the name - very fancy with a board full of eq & compress/limiter (no external adjustments but plenty of trimpots on the board) to simulate mic response on a speaker.

If you find the signal's way too bright on a simple line out voltage divider, you can parallel a cap across the "lower" resistor, choose a value to taste, roll off some of that sizzle, that can work acceptably for cheap.

[Chuck H]

I promise I tried to search first but it seems I can't find anything until after I post....then it seems to come out of the woodwork.

That actually happens to me all the time. I'll search and search. Then I'll post and explain that a search didn't reveal an answer (because I don't want the crew here to think I didn't even try). Then the next several responses will have links relating to my post. uhgg.

And, FWIW, everyone should learn to fish. It provides a perpetual series of occasions to hope.

[Enzo]

Last time I fished was 1969. We were on a lake in New Jersey. We had been on the shore, dug up a bunch of clams and steamed them. I discovered I hate clams. SO I baited a hook with one and tossed it in. Not long after, a fish bit on it, and I reeled in a fish. I then thought, "Now what the hell am I going to do with a damned dead fish?" So I handed the pole - with fish still on the other end - to some kid standing nearby. Problem solved. Ever since, as far as I know, fish come from the freezer, with breading.

[Chuck H]

It does occur to me on slow days astream that a fish can be purchased and I don't even need to clean it But I'm working on a pair of fly rod builds even now. It's alright Enzo. More room for me at the fishin' hole.

The last time I went fishing was a couple of weeks ago. The end of the beach fishing season for Coho salmon. I did well this year with fifteen fish in 10 stops at my local beach. I have salmon fillets stacked up in my freezer like cord wood

[g1]

I haven't yet figured out how to master the "search" function yet, so if anyone would like to repost the instructions for doing it via Giggle again, that'd be great...

refer to following (you can get to the google advanced search by clicking the gear button on the regular google search page)

The search engin built into the software used for MEF leaves a lot to be desired. I don't think that tboy or the moderators can do anything about that. I have found a better way to search MEF. I use google advanced search at Google Advanced Search and enter music-electronics-forum.com in the "site or domain:" field. It works really well.
Regards,
Tom

[Justin Thomas]

Thanks! Now if I could permanently cripple the @$&#ing Autocorrect, interpretive text fill-in, and Swype on my Kindle, I'd be set! I spend more time fixing ITS mistakes and wrong assumptions about what I type than I do trying to type my thoughts...
Don't bother explaining, I'm still trying to figure out how to bookmark a page with it...

Justin