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Re: [ARSCLIST] Setting bias on any tape recorder
After aligning the deck for playback, per Richard's list,
there is a simple way to set bias on any machine, recording
on any tape. Use a 1000 Hz test signal and set bias current
for maximum recording sensitivity (VU meter reading).
Then for 15 and 30 ips recording, increase the bias until the
output level drops 0.2 dB. For 3.75 and 7.5 ips recording,
decrease the bias until sensitivity drops 0.1 to 0.2 dB.
One slight problem with this is being able, accurately,
to read such small values on a conventional VU meter!
(This method comes from Jay McKnight, of MRL Labs.)
Another method, also requiring a tone generator, is to
record a low frequency, such as 30 Hz, at a very low
level - at least 20 dB below normal operating level -
and crank up the playback level enough to hear the
output clearly, then adjust bias for the minimum amount
of distortion (modulation noise, actually). This method
allows one to easily adjust the bias by ear, listening for
the cleanest reproduction of the low tone. The point of
minimum modulation noise will very closely match bias
settings arrived at by more elaborate means.
OF COURSE, after setting bias one must always go back and
look at the high frequency response (10 kHz) and readjust the
recording eq for flattest response.
Yes, bias setting is somewhat complicated, but it is good to
remember it is always a matter of compromise, between the
least distortion on the one hand, and the flattest overall high
frequency response on the other.
Doug Pomeroy
===========================================
Date: Sat, 2 Feb 2008 14:37:46 -0500
From: "Richard L. Hess" <arclists@xxxxxxxxxxxxxxx>
Subject: Re: Setting bias and EQ on ANY recorder
At 11:51 PM 2008-01-31, Sammy Jones wrote:
From: Sammy Jones [mailto:sjones69@xxxxxxxxxxxxx]
Subject: Setting bias and EQ on Technics 1520
My problem is in setting the EQ and bias properly to record on this
tape. This is my first time recording tape on a machine with
settable
bias and EQ, and the Technics service manual does not specify how
to do
this. I've found some information on the web for bias setup, but not
EQ.
I have placed a simplified set of instructions in my blog
http://richardhess.com/notes/2008/02/02/aligning-a-tape-recorder/
Please let me know if you have any questions -- I'd prefer you ask
them in the comments section of the blog.
Cheers,
Richard