| Buffer for my system? [message #75493] |
Mon, 11 February 2013 11:10  |
mantha3
Messages: 72
Registered: May 2012
Location: Lino Lakes, MN
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Viscount |
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Hi all,
I currently run some 4 PI speakers and I run a pair of subwoofers with them as Wayne advises. Real happy. I have a nice subwoofer that I built with a Morel 12" and then I have an older Boston Acoustics 8" subwoofer. So I run to the plate amps of each of these subwoofers the R/L signal running each in Mono since they are running the blended R/L. One is in the front of the room the 2nd is on the side of the of the room side fire. The sound is nice!
I have a signal source and then run the signal split 3 ways... 1 to the pair of tube amps for the 4PI pair, 1 signal R/L of a plate amp on the subwoofer, 1 signal R/L of a plate amp on the 2nd subwoofer.
Having the signal split 3 ways I was thinking a buffer may be a good idea... Run a Buffer that has an Input and then have it with 3 outputs? I think a buffer would be a good thing to introduce to get a bit better drive behind the 3 way split. Not sure about Tube Buffer or a Pass B1
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| Re: Buffer for my system? [message #75504 is a reply to message #75501] |
Tue, 12 February 2013 10:45  |
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Wayne Parham
Messages: 18793
Registered: January 2001
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Illuminati (33rd Degree) |
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Good advice: I think the gist of what you're saying is correct, and would limit fan-out to a reasonable number of connections.
The thing that concerns me more than drive level is noise immunity, and that having a bunch of unbalanced lines connected together might introduce more noise. If the source output impedance is really low, like 25Ω, then the source/sink will probably do a pretty good job of swamping any noise. Even the typical range of 50Ω to 100Ω outputs are probably fine. But if the output impedance is on the high side, say 250Ω, then it can't do as good a job of clamping the line and noise is potentially more likely. So I guess my real concern with fan-out isn't the drive level but the vulnerability to noise.
As to buffer amps, I think they're good for the noise problem (if one finds they have it) but I wouldn't put one in just to do it. If there is no noise problem, don't. No need to introduce anything into the signal path that isn't necessary.
Boils down to a situation where you just have to see what you have and decide what to do. If you don't have a noise and/or drive problem, don't add a buffer stage.
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| Re: Buffer for my system? [message #75516 is a reply to message #75493] |
Tue, 12 February 2013 18:39 |
Les Winter
Messages: 12
Registered: June 2009
Location: Northern New Jersey
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Chancellor |
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You may not have the problem you think. The tube amp may have an input impedance near 500K which, compared with the others, is neglegable. I would suggest that you can call the sub manufactures and ask what impedances the sub amps are. If I remember correctly, my parts express plate amp was around 18k. A pair of 18k's in parallel is a manageable 9k. The tube amp's presence would then be hardly noticable if at all.
That said, I use a b-1 to avoid having a passive master volume control. Nelson Pass writes about the subjective sound this produces in his B-1 article.
My b-1 works great, adds litte or nothing I can detect and is not finicky to wire up. It is running constantly for several years w/o issues.
good luck.
Les
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