NewBuyer;369048 Wrote: > My own naive questions: Is an external buffer essentially a separate > output-stage-in-a-box? Is it really a voltage amplifier / preamp > without a volume control? Does the buffer's high input Z and 6db gain, > allow the previous device's output stage to run in a more optimum range > with less distortion? Does it perhaps filter out ultrasonics from the > audio signal? etc. etc. :)
It -can- be a "separate output-stage-in-a-box". In this case, since it has 6 dB of gain, it is probably a "voltage amplifier / preamp without a volume control". And one would probably be safe in concluding that its core is the items that you mention. (Why not? They already have the PCBs and parts to make them. Gotta use them somewhere.) The 6 dB of gain or high input Z has nothing to do a "more optimum range". So, can it sound better when inserted in the chain, and how? Well, it can. Or not. The best guess that I can give is not far from where you are thinking. I may have mentioned this before, but if I did, just bear with me. Years ago, we produced an outboard D/A box. It had fixed and variable outputs. Both were identical. (OK, one had a pot in front of it.............the rest was identical, ok?) Both originated from the same point inside. Which output sounded better? We felt that the fixed output, run through our preamp (yes, we made preamps at one time as well) sounded better than the variable run straight into the amp. The only guess that we had was that the preamp somehow dealt with the minute amount of HF crud that came out of the D/A than the amp did. Either that, or it provided that little bit of additional filtering to get rid of it. Or both. Speaking of HF crud, here is a small idea on how to deal with it. This might be more helpful in the DIY section, but it is going here for now. Both outputs used a 2-pole RC filter. I think the resistors were 249R and 147R. Or close to that. A Wima FKP to ground at each junction. From the PCB to the RCA jacks was only 2-3 mm of wire. There was a small amount of HF crud on the output. Probably having its origin around the filter chip. Anyway, we found that if we put the second cap *directly* on the RCA jack, instead of the PCB (with that small run of wire), that *all* of the HF crud went away. Obviously, that would not look professional for a $2-3K product. Which is why the only ones that we did that way were the ones we all used in our personal systems. Unfortunately, we never did the straight-vs-variable A/B test after we did that little trick. In retrospect.........well, that was over 15 years ago and in our ignorance, we blew our chance to know. Pat -- ar-t http://www.analogresearch-technology.net ------------------------------------------------------------------------ ar-t's Profile: http://forums.slimdevices.com/member.php?userid=13619 View this thread: http://forums.slimdevices.com/showthread.php?t=56068 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
