Biasing
- Thread starter iangerber
- Start date
thinbrownline
New member
Hi iangerber
I understand what you are asking, but you may be mixing concepts here.
Setting the correct bias current for the tape is one thing, but it doesn't equate to what level you put on the tape.
What I think you are asking is, if I use a tape that is capable of handling signals 9 dB above Ampex operating level (eg. Ampex 499 and the ATR tape), do I need the meters to go to +9 to get that level onto the tape?
And the answer is, it depends on how you have lined up your machine. Typically if you are aligning for a +9 tape, you will set the machine so that a signal that is +9 on the tape will read, say, 0VU or +3VU on your meter. That way, you are putting +9 on the tape when the meter is bouncing around at the top of the scale.
To do this with an alignment tape that's recorded at 185nWb/m (Ampex operating level), you would adjust the machine so that the tones all read -6VU when playing the tape. Then when you record a signal that reads +3VU, it is actually putting +9 on the tape.
Make sense?
Good luck with your alignment.
Regards
David Ollard
Thin Brown Line
Multitrack Analog to Digital Transfers - Reel to Reel Tape Transfer - Audio Tape Transfer to Wave Files for Pro Tools and other DAW - Digitize Open Reel Tapes - Thin Brown Line
I understand what you are asking, but you may be mixing concepts here.
Setting the correct bias current for the tape is one thing, but it doesn't equate to what level you put on the tape.
What I think you are asking is, if I use a tape that is capable of handling signals 9 dB above Ampex operating level (eg. Ampex 499 and the ATR tape), do I need the meters to go to +9 to get that level onto the tape?
And the answer is, it depends on how you have lined up your machine. Typically if you are aligning for a +9 tape, you will set the machine so that a signal that is +9 on the tape will read, say, 0VU or +3VU on your meter. That way, you are putting +9 on the tape when the meter is bouncing around at the top of the scale.
To do this with an alignment tape that's recorded at 185nWb/m (Ampex operating level), you would adjust the machine so that the tones all read -6VU when playing the tape. Then when you record a signal that reads +3VU, it is actually putting +9 on the tape.
Make sense?
Good luck with your alignment.
Regards
David Ollard
Thin Brown Line
Multitrack Analog to Digital Transfers - Reel to Reel Tape Transfer - Audio Tape Transfer to Wave Files for Pro Tools and other DAW - Digitize Open Reel Tapes - Thin Brown Line
thinbrownline
New member
A good place to start with tape machine maintenance is always Michael Gore's excellent website analogrules.com.
Here is a link to the alignment page: TAPE RECORDER ALIGNMENT INSTRUCTIONS from BASE/AnalogRules.com
Click on the button on that page that takes you to the printable alignment instructions. Bias is covered very nicely on page 4, but read all of the document anyway... in fact anyone new to tape machine ownership should really read through the entire web site!
Regards
David
Here is a link to the alignment page: TAPE RECORDER ALIGNMENT INSTRUCTIONS from BASE/AnalogRules.com
Click on the button on that page that takes you to the printable alignment instructions. Bias is covered very nicely on page 4, but read all of the document anyway... in fact anyone new to tape machine ownership should really read through the entire web site!
Regards
David
diggy_dude
Now 169% diggier!
I would look for the TRS-8 service manual.
Blue Jinn
Rider of the ARPocalypse
+1 on the manual. Bias and Operating Level are two separate adjustment. E.g. Quantegy 406 and 456 are +3 and +6dB tapes respectively but share the same bias. 499 is a +9 tape which also requires a higher bias. You need a reference tape to set hte operating level. I don't know about the TSR-8, some machines you set the bias off the VU meters some you need an AC Voltmeter.
jpmorris
Tape Wolf
The TSR-8 service manual seems to me to be something that was only handed out reluctantly to service engineers. I've never seen it sold except for the dodgy scanned copies on ebay.
Regarding what you're attempting, I'm not 100% sure whether the TSR-8 goes up to +9 and I figure you're likely to get a lot of crosstalk if you crank it up too high, assuming it can even cope.
It was designed to run at 250nWb/m on Ampex 456 tape, though I have run it with SM900 and 499 on occasion.
Be aware that the machine is a bitch to align because it only has one audio head so you have to keep rewinding and playing it back. On a 3-head machine you would able to to adjust it on the fly. Mine seems to be reasonably decent so I haven't touched it.
I do have the biasing instructions at home, if I remember to look it up.
EDIT: I figure you will need an audio-capable meter - trying to use the VU ladders sounds like a bad idea to me.
Regarding what you're attempting, I'm not 100% sure whether the TSR-8 goes up to +9 and I figure you're likely to get a lot of crosstalk if you crank it up too high, assuming it can even cope.
It was designed to run at 250nWb/m on Ampex 456 tape, though I have run it with SM900 and 499 on occasion.
Be aware that the machine is a bitch to align because it only has one audio head so you have to keep rewinding and playing it back. On a 3-head machine you would able to to adjust it on the fly. Mine seems to be reasonably decent so I haven't touched it.
I do have the biasing instructions at home, if I remember to look it up.
EDIT: I figure you will need an audio-capable meter - trying to use the VU ladders sounds like a bad idea to me.