dmmartindale (01/01/83)
(this discussion probably belongs in net.audio, but since it started here I'll continue.) Hmm. I just assumed that the decks which didn't have the fancy auto-biasing circuitry would have the usual large collection of trimpots. Any deck which doesn't have a sufficient set of calibration controls probably shouldn't be part of a "hi-fi" system since you simply can't expect good results from it. This would certainly be something to check on when buying a deck, although I would be very surprised if any deck which had decent frequency response lacked the adjustments. For an idea of what to expect, my deck (Harman/Kardon hk200XM) has the following internal tape-specific adjustments: record level, record equalization for each channel for each of 4 tape types - total 16 potentiometers, plus two adjustable inductors. record bias level for each of 4 tape types - 3 pots and two trimmer capacitors. All of the above may need changing if you changed all 4 types of tape your record on; switching one of the four would probably only require changing 5 adjustments. There are also the following adjustments which don't depend on the tape used, but must be set properly nonetheless (and may need occasional readjustment): head azimuth motor speed playback level calibration (two pots) playback equalization (two pots) bias trap (two inductors) Dolby HX threshold (4 pots) level meter calibration (4 pots) Now, most decks won't have the Dolby HX adjustment, but better decks may have a pair of additional playback EQ adjustments or Dolby B or C threshold adjustments. My deck does have a front-panel bias trim adjustment, but I consider it useful in emergencies only because there is no corresponding record equalization adjustment. You can see that an analogue tape deck has a LOT of adjustments that affect its performance, and the only way to get what it's capable of is to get them set properly in the first place, and check them once in a while.
jwb (01/04/83)
The last time I adjusted a tape recorder's bias (admittedly a long time ago) I used a distortion analyzer. I guess I am out of date with respect to high end cassette decks, as I would have thought it would take a rack full of equipment to properly adjust all of the controls which now seem to be available, and which seem to be adjusted by a number of net contributors.
dmmartindale (01/04/83)
Recommended equipment for aligning my HK deck is: two dual channel AC VTVM's frequency counter signal generator distortion analyzer spring tension gauge 4 different test tapes blank tape in 4 different types You probably don't really need more than one single-channel VTVM (or other high-impedance AC voltmeter) if you're willing to spend some more time moving the test lead around while making adjustments. The rest are all necessary. I don't have a distortion analyzer, so I don't set up my own deck - I have the store where I bought it do the work. If I were paying for it separately (it was included in the price of the deck), it would cost about $30 (CDN). I think this is worth it.