Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on March 09, 2012, 08:31:54 am
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Hi. what would be the best ratio for a line out ? 1/20, 1/10 ? Can I use the extension speaker jack for that purpose ? Two taps of the OT would then be used. I read that the goal was to obtain 1 volt of output. Any bypass cap with any of the voltage divider resistor ? And is there any negative effect on the OT ?
Thanks
Colas
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This is the way a famous brand solved the problem in some of their's amp
Kagliostro
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The "best" combination is the one that gets you the correct voltage out. Line level is ideally .775VAC, however it can be anywhere between .5VAC and 1.5VAC, or really what ever you need.
First, calculate the voltage out from whatever secondary OT tap you want to take the line out from using ohms law (or just measure it if the amp is already built). Then, create a voltage divider to get approximately .775VAC. Since guitar amps can produce power past the their clean RMS output when they are overdriven, design for a little margin for that. Better yet, replace the the bottom half of the divider with a pot.
Try to keep the resistances as low as possible to reduce loading and dulling of the tone. Of course, when you get below a certain point you'll have to use higher wattage resistors.
What size is the amp, and what tap would you like to take it off of? I can walk you through the process since my explanation was pretty sloppy!
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Or, more simply, what signal level is the input of the piece of gear that will receive the signal expecting?
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I guess all ''line in'' inputs from mixing boards are standardized, and anyway, they all have a volume control.
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I guess all ''line in'' inputs from mixing boards are standardized, and anyway, they all have a volume control.
Not even close. There's an enormous difference between pro, semi-pro and consumer gear, just as there are price differences and difference of expectation from the user.
Okay, so it was a not-clear question. Clear question: What will you plug your amp into?
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This is my client's amp and he wants a line out...where is he going to plug it in ? God knows where ! For recording he said. According to what I have read, a voltage divider 10:1 would be ideal, since I have 11 VAC at the speaker out jack with a 1K signal plugged into the guitar jack input, and that a good voltage would be around 1V. What value of resistors would be suited ? I guess not too high, like 1 K and 10 K, what d'you think ?
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Just make the line out variable. Kinda like this...
(http://www.el34world.com/Forum/index.php?action=dlattach;topic=13304.0;attach=28604;image)
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The 10:1 ratio is totally aribitrary. What if you have 50VAC at the speaker? A 10:1 divider will not get you .75VAC! Since you have 11VAC at the speaker, just play around with a voltage divder calc to get in the right range. Sluckey's example is really the best method if you have room for a pot as well.
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> What if you have 50VAC at the speaker?
Then you have 300 Watts in 8 ohms, 600 watts in 4 ohms.
DeLuxe is closer to 9V than 50V.
We need some clue to amp power and impedance. Does not have to be exact, but is it huge medium small, is there a 4 ohm tap or only a 16?
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The gaz, I was talking about 10:1 ratio, since I had 11 V at the speaker jack, in order to end up with 1V or so.
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Yeah, it does work quite nicely with your examples, I just mentioned it because i read that somewhere and it totally confused me at first because I was working with a high wattage amp.