Under - biasing on purpose
- Thread starter Makymak
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Mak,
Here's an excerpt from a Sony user manual to give you a frame of reference. The theory applies regardless of the manufacturer.
So it is a common thing but the trade off is high freq roll-off vs. increased distortion ... and it will be influenced with other factors:
Internal calibrated condition of any particular deck with a manual bias adjustment
The grade of the tape
The recording level
The quality & complexity of the content
And most importantly, your ears ...
Here's an excerpt from a Sony user manual to give you a frame of reference. The theory applies regardless of the manufacturer.
So it is a common thing but the trade off is high freq roll-off vs. increased distortion ... and it will be influenced with other factors:
Internal calibrated condition of any particular deck with a manual bias adjustment
The grade of the tape
The recording level
The quality & complexity of the content
And most importantly, your ears ...
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My Pioneer CT-A9X has the option of selecting under-bias, peak-bias, or over-bias in the auto calibration process:
Pioneer CT-A9X Cassette Deck Review price specs - Hi-Fi Classic (hifi-classic.net)
"Another feature of the Pioneer CT-A9X is its auto-ble (for bias, level, and equalization) system, which optimizes the key recording parameters for the specific tape being used. Computer-controlled circuits record a series of test signals on the tape, play them back, and adjust the bias, recording level, and equalization for optimum frequency response and maximum output level (MOL) characteristics. The process takes about 11 seconds, after which the tape rewinds to its initial position, and the settings are stored in the recorder's memory until it is shut off or the calibration process is repeated. The auto-ble system is put into operation by pressing one of three buttons, marked under bias, peak bias, and OVER BIAS. Normally the peak bias button is used, but the others give a user the option of slightly adjusting the recorder's performance to suit individual preferences."
Nando.
Pioneer CT-A9X Cassette Deck Review price specs - Hi-Fi Classic (hifi-classic.net)
"Another feature of the Pioneer CT-A9X is its auto-ble (for bias, level, and equalization) system, which optimizes the key recording parameters for the specific tape being used. Computer-controlled circuits record a series of test signals on the tape, play them back, and adjust the bias, recording level, and equalization for optimum frequency response and maximum output level (MOL) characteristics. The process takes about 11 seconds, after which the tape rewinds to its initial position, and the settings are stored in the recorder's memory until it is shut off or the calibration process is repeated. The auto-ble system is put into operation by pressing one of three buttons, marked under bias, peak bias, and OVER BIAS. Normally the peak bias button is used, but the others give a user the option of slightly adjusting the recorder's performance to suit individual preferences."
Nando.
It occurs to me that if you must make a sacrifice in order to get a tape to sound flat, maybe you need a different tape?
For me, across all audio junk I mess with, my goal is always an accurate reproduction of what was originally recorded, and if I’m recording, to capture the performance as accurately as possible.
I do recognize that boosting the treble “enhances” the sound of recordings- and that “louder” sounds better, but I do my best to keep out of those traps…
For me, across all audio junk I mess with, my goal is always an accurate reproduction of what was originally recorded, and if I’m recording, to capture the performance as accurately as possible.
I do recognize that boosting the treble “enhances” the sound of recordings- and that “louder” sounds better, but I do my best to keep out of those traps…
Some recordings need help... regardless of the medium. Short of pulling them into the digital domain and altering them, a quick remedy often times is a little bias nudge. It just depends.
I can be anal about 'fidelity' and 'as the artist or producer intended' too but it's not an all or nothing in my mind.
Sometimes the recording isn't optimal. Lots of reasons for why that can be. The way I figure it, if you're going to dedicate part of your time to listen to something and most likely listen to it again & again ... then 'helping' it is a good thing. I mean ... tone and eq controls were created for real reasons. So how is a touch in one direction or the other in terms of bias sacrilegious?
<<<< exit stage left
I can be anal about 'fidelity' and 'as the artist or producer intended' too but it's not an all or nothing in my mind.
Sometimes the recording isn't optimal. Lots of reasons for why that can be. The way I figure it, if you're going to dedicate part of your time to listen to something and most likely listen to it again & again ... then 'helping' it is a good thing. I mean ... tone and eq controls were created for real reasons. So how is a touch in one direction or the other in terms of bias sacrilegious?
<<<< exit stage left
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Well, you make a good point- tone controls (and loudness switch).
I use them. Even balance controls from time to time.
But as far as the tape goes, I don’t necessarily want to mess with that. I’ll run something through an EQ (Although I don’t currently have an analogue one) or use tone controls, when dubbing, to get a tape to sound the way I want it to.
But messing with the bias, although not a big deal in the grand scheme, is not a way I’d want to alter the tone or frequency response of a recording.
And maybe I’m in the minority, but that’s okay. Anyone can use their gear as they see fit.
I use them. Even balance controls from time to time.
But as far as the tape goes, I don’t necessarily want to mess with that. I’ll run something through an EQ (Although I don’t currently have an analogue one) or use tone controls, when dubbing, to get a tape to sound the way I want it to.
But messing with the bias, although not a big deal in the grand scheme, is not a way I’d want to alter the tone or frequency response of a recording.
And maybe I’m in the minority, but that’s okay. Anyone can use their gear as they see fit.
I have taken that attitude throughout my entire chain, including when I was recording. If I wanted a different sound, I used a different mic. Didn't tweak the EQ on the mixer. Dunno if that helped any but the few amateur recordings I made sounded okay, if a little dry. But then, the room didn't have a lot of natural reverberation in it - lots of carpet and angled walls/ceiling.
That said, I'm kind of intrigued by what this little $150 box offers; I just can't use it on my Exposure amp as there's no way to return the signal to the amp section after sending from the preamp.
https://www.theabsolutesound.com/articles/schiit-audio-loki-mini-equalizer
https://www.theabsolutesound.com/articles/schiit-audio-loki-mini-equalizer
I usually do not intervene in original EQ. My POV is that the artist/producer knows better. If I have to alter EQ, I would use my Technics SH-GE70 which has a tape loop chain connections unless my format is digital so then, I use a computer (and Steinberg's Wavelab).
I wouldn't consider to use the bias adjustment for brighten the recording as I'm a "like - it - flat", too. But, as my original question says, the high frequency losses a ferric tape suffers through the years and playback sequences due to wear, magnetostriction (if such a thing exists - yes, opening another can of worms
) or physical decay, could be counterbalanced by giving a tiny bit of less bias than acquired. And to answer to myself, the things are getting more complicated as some major challenges arise: how much under - bias is needed to have a flat FR when the tape is stabilized and no more hf losses occur? How many passes a tape needs to reach the "no more hf losses" point? And the obvious challenge is that till the tape reaches this point, the recording won't sound as it should; it will be brighter...
I wouldn't consider to use the bias adjustment for brighten the recording as I'm a "like - it - flat", too. But, as my original question says, the high frequency losses a ferric tape suffers through the years and playback sequences due to wear, magnetostriction (if such a thing exists - yes, opening another can of worms
) or physical decay, could be counterbalanced by giving a tiny bit of less bias than acquired. And to answer to myself, the things are getting more complicated as some major challenges arise: how much under - bias is needed to have a flat FR when the tape is stabilized and no more hf losses occur? How many passes a tape needs to reach the "no more hf losses" point? And the obvious challenge is that till the tape reaches this point, the recording won't sound as it should; it will be brighter...
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