Why would that cause the distortion, and why with CD and not LP?
- 22 posts total
- 22 posts total
I have no idea. Called VAC this am and they had a couple of troubleshooting ideas, including the balanced/se output switch being in the wrong position. When I rolled the rack to see the switch, I found the S-BAM dangling w/o a pc. If Sean or any or Bobby or any of our tech heads are hanging out and have any ideas, I would be happy to listen...Meanwhile I am one happy camper; the VAC tech said next step was a trip to FL. And many thanks for Brent at VAC who spent about 15 minutes w/me on the phono trying to trouble shoot.
The BAM module is basically an active equalizer with a high pass filter built into it. This reduces driver excursion below port resonance, lowers distortion, reduces power consumption and increases power handling.
Evidently, either your phono system isn't capable of very deep bass and / or the records that you were playing didn't have a lot of deep bass on them. Obviously, the CD's did, which is what caused the distortion that you heard. This is one of the drawbacks of using a vented design without some form of active equalization and / or a steep high pass filter. Now you've actually heard the distortion that i've mentioned many times before when discussing vented designs and the woofer(s) becoming "unloaded". Not pretty, is it?
Glad that you were able to figure things out without any real down-time or great expenditure on your part. Sometimes, as is the case here, the simple stuff is the easiest stuff to overlook. Sean
Sean- I could never disagree with your analysis because I have no knowledge in this area, but I will say that the distortion sounded like it was mostly in the vocal frequency range. and as far as I know, the BAMs (several generations ago) were optional with the VSM. The sound I got was very noticeable and totally unlistenable, even to my son who listens to MP3s played through his cell phone speaker!!!
Obviously, i wasn't there to hear what was going on, so i could be off in left field. Having said that, over-excursion of a mid-woofer can lend a distortion / vibrato effect to midrange and treble frequencies. Don't know if this is what you were hearing, etc... In severe cases of over-excursion, the driver will mechanically bottom out. This sounds VERY scary, as it should. Sean