ron@trsvax.UUCP (10/31/84)
Does anyone have any experience with the Heathkit Sub-woofer system they have? {microsoft,ctvax}!trsvax!ron
jf4@bonnie.UUCP (John Fourney) (03/29/85)
*** REPLACE THIS LINE WITH YOUR MESSAGE *** Here's the situation: I have two headphone signals (walkman + stereo keyboard) that I want to mix together to hear on one headphone. Can you 'Y' this stuff togther directly or do you need a mixer. I tried mixing both left channels and both right channels but the mixer attenuated the signals a lot. Is is possible to mix speaker level signals? Thanks John
fish@ihlpg.UUCP (Bob Fishell) (04/02/85)
> *** REPLACE THIS LINE WITH YOUR MESSAGE *** > Here's the situation: > I have two headphone signals (walkman + stereo keyboard) that I > want to mix together to hear on one headphone. > Can you 'Y' this stuff togther directly or do you need a mixer. > Is is possible to mix speaker level signals? *** AC T YOUR AGE *** It depends on the output impedance and levels of the devices. Generally, it's not a good idea to "y" outputs together, since you'll frequently wind up with two C/S collector circuits glaring at each other -- bad for both of them, especially if they share a ground connection. For higher impedance headphones, e.g. Sennheisers, all you need to do is put a couple of resistors in series with each output device, i.e. R1 device 1 o-/\/\/\/\-:----headphone R2 | device 2 o-/\/\/\/\-' R1=R2=150 ohm. This will provide sufficient isolation, in most cases, to eliminate any problems that might be caused by the amps loading one another down. If you have a floating ground output, you'll have to use two sets of resistors, one on each lead. This scheme will work (I've done it) for headphone jacks as well as speaker drive terminals, as long as you're driving a relatively high impedance. If you have speakers or other low-impedance loads, you'll have to use a mixer. /_\_ Bob Fishell ihnp4!ihlpg!fish
sjc@angband.UUCP (Steve Correll) (04/02/85)
> I have two headphone signals (walkman + stereo keyboard) that I > want to mix together to hear on one headphone. > Can you 'Y' this stuff togther directly or do you need a mixer. > I tried mixing both left channels and both right channels but > the mixer attenuated the signals a lot. > Is is possible to mix speaker level signals? Generally, no. A good audio amplifier strives to present an output (or "source") impedance much lower than that of the speaker, so when you connect two amplifier outputs together, each amp looks almost like a short-circuit to the other. Because high-powered hi-fi amps put out much higher voltage than headphones require, many amps have a fairly large resistor between the last amplifier stage and the headphone output. In such cases, you can mix signals by connecting the headphone outputs together. I suspect that the Walkman lacks such a resistor, however, since its amplifier is low-powered enough to begin with that it matches the characteristics of headphones directly. I don't understand why your mixer attenuates the signals too much. Does the mixer have an output intended for headphones? A mixer output meant to drive an amplifier probably won't produce enough power to drive headphones. -- --Steve Correll sjc@s1-b.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc
don@umd5.UUCP (04/03/85)
> Is is possible to mix speaker level signals? > -John [] Yes, it is quite possible to mix speaker level signals, but one should do so with a resistive network to maintain proper impedances in the system. Use three 2.7 ohm (8 divided by 3 and standardized) 5 watt resistors (5 watts audio is LOUD). Hook them together like this: Input 1 >-------------< Input 2 \ / \ / \ / \ / \ / \ / | ^ Load The resistors form the sides of the triangle. Cheap and effective. -- ----------------------------------------------------------------------------- "Space, the final frontier .." Final, hell! It's the frontier of frontiers !! ----------------------------------------------------------------------------- -==- IDIC -==- (Thanks Bob!) SPOKEN: Chris Sylvain ARPA: don@umd5.ARPA BITNET: don%umd5@umd2 CSNET: don@umd5 UUCP: {seismo, rlgvax, allegra, brl-bmd, nrl-css}!umcp-cs!cvl!umd5!don
aopal@wateng.UUCP (Ajoy Opal) (04/05/85)
> *** REPLACE THIS LINE WITH YOUR MESSAGE *** > Here's the situation: > I have two headphone signals (walkman + stereo keyboard) that I > want to mix together to hear on one headphone. > Can you 'Y' this stuff togther directly or do you need a mixer. > I tried mixing both left channels and both right channels but > the mixer attenuated the signals a lot. > Is is possible to mix speaker level signals? > Thanks > John Yes , it is possible, but if you attempt to mix signals at the output directly one amplifier will basically be attempting to drive the output of one amplifier against another...ie they would blow up, if it were'nt for the short circuit protection provided by the makers of both the stereo keyboard and walkman. A crude way of mixing would be to use three resistors in a "Y" configuration, but this will result in some (maybe a lot ) attenuation in the signal. walman out ---/\/\/\/\----| 20 ohms | | ---- mixed output | | | keyboard ----/\/\/\/----- output 20 ohms the values are not exact. Larger values will attenuate the signal but will provide better mixing. Larger relative vaules of the walkman resistance shall decrease the amount of signal from the walkman, and similarly for the keyboard output. The best place to do the mixing is at some stage prior the output section...and then feed the whole signal to a an output stage. ray
klein@ucbcad.UUCP (04/05/85)
> Input 1 >-------------< Input 2 > \ / > \ / > \ / > \ / > \ / > \ / > | > ^ > Load > Oops, doing a quick analysis of this network shows that the load presented to each amp channel is 7R/11, or in this case, R = 2.7ohms, or 1.72 ohms. The amp will have a very hard time here, and almost none of that power makes it to the 8 ohm load. Also, the load is driven through an R/2 output impedance, so damping factor suffers. Using a resistive network will always mean losing power and damping factor. A big transformer is certainly the best way to do this, ideally, but expensive for good quality. You could also buy speakers with two voice coils, if you have that luxury and are only interested in mixing bass. -- -Mike Klein ...!ucbvax!ucbmerlin:klein (UUCP) klein%ucbmerlin@berkeley (ARPA)
don@umd5.UUCP (04/08/85)
>> Input 1 >-------------< Input 2 >> \ / >> \ / >> \ / >> \ / >> \ / >> \ / >> | >> ^ >> Load >> > Using a resistive network will always mean losing power and damping factor. > -Mike Klein [] Ackk ! Attack of The Memory Bug! (Thanks Mike!) It didn't seem to me that damping factor would be of any consequence for the asker's application, and since he was using low power anyway (headphones), and what's a half a watt among friends, anyway? The revised schematic is: Input 1 >---/\/\/\---o---/\/\/\---< Input 2 | | | | ^ Load The resistors form either half of the top of the "T" and the "|" portion. [Look at the referece book before you post something off the top of your head !!! ... Let that be a lesson to you all !! :^) ] -- ----------------------------------------------------------------------------- "Space, the final frontier .." Final, hell! It's the frontier of frontiers !! ----------------------------------------------------------------------------- -==- IDIC -==- SPOKEN: Chris Sylvain (transient user of Don Preuss' account) ARPA: don@umd5.ARPA BITNET: don%umd5@umd2 CSNET: don@umd5 UUCP: {seismo, rlgvax, allegra, brl-bmd, nrl-css}!umcp-cs!cvl!umd5!don