The No.1 Website for Pro Audio
Help Calibrating Reel to Reel (Ampex 440b)?
Old 18th February 2020
  #1
Help Calibrating Reel to Reel (Ampex 440b)?

Hello Folks. So I now have a very cool Ampex 440-b 1/4 inch 2 track.

But I'm realizing that after going through the manual and watching online videos, I'm still mystified about how to calibrate it. I've picked this up and put it down several times, but each time get stumped, and as a result, haven't figure it up though its been here for a while.

I can't help imagine this is the sort of thing that someone who knows what they're doing could clear up pretty damn quickly, seems like the whole procedure should take more than 20 minutes if you know what you're doing, but so far the manual has me baffled, and videos only helped so much.

What are the basic steps of calibrating any machine? Seems like alcohol clean, then demagnetize, then levels, azimuth, and bias. Its the specifics that get me confused from there, including below an attempt of mine to gather some info on another thread.

---

A previous poster suggested this for the color I'm looking for: "I recommend a 15 ips, 250 nW/m, IEC 2 calibration tape. MRL makes them." It was also mentioned that for the tone I'm looking for (vintage, thick, Pink Floyd from Dark Side to Animals) would likely require a particular set of settings, but I can't find the exact info (6db biasing?) but I'm not sure about that, nor precisely how to do that (all the manuals explain for 0, is that 6db above or below, and where/how?). I bought the MRL test tape according to that recommendation, Magnetic Reference Lab 21J205 Recording, as well as Recording with the Masters SM468 Analog Tape - R35111 1/4" x 1200', 7" Plastic Reel, Trident Hub, and a standard demagnetizer.

From watching videos online, it seems I should clean the heads with 90 percent alcohol to start. Do I demagnetize before or after that? From what I can tell then, I need to check alignment on the heads with visual inspection. Then set levels to 0db at 0Hz and 10kHz for standard and high freqs for the various heads, but then people in videos start talking about whether or not 0db makes sense, but wasn't clear why. Then I need to adjust azimuth (no idea what that means), I think by recording a 0Hz and 10khz freq, play it back for an oscilloscope set so that it makes a diagonal line, turn the screws (near the tape heads) all the way in one direction till it overshoots, then slowly wean it back to 0db, or is this where I need to get the one curve under the other, but where does the other one come from, and then there's bias and overbiasing (?!), and by this point, I'm over my head.

--

Input of any sort very much appreciated!
Old 19th February 2020
  #2
Gear Addict
 
Jeff A. Roberts's Avatar
 

Show and tell

I think you would benefit greatly by hiring a skilled technician to come to your place and show you how to tweak your machine.

When I learned how to setup a tape machine it was a one-to-one learning experience (with the late great Scot Rivard) and it all made sense as I could ask questions and get immediate answers.

My head would have probably exploded if I had to learn from written text or videos.

In my market (Minnesota/Twin Cities) Eddie Ciletti would be the person to learn from.

Good luck in your quest for knowlege.
Old 22nd February 2020
  #3
Gear Nut
 

Probably best to get a tech in but you will need to de-mag the heads if they haven't been done in a while, and clean all the tape heads and any metal parts in the guides (not the rubber bits) with IPA.
You will ideally wanna do azimuth settings too so make sure you know where those are on the machine + have the correct tool.

You'll need an MRL calibration tape and a chart to work out your levels depending on the type of tape you'll be running and at the desired speed.
If you want it as a colour box then line it up way hotter than what your tape asks for and experiment with level and speed/eq settings.

Do playback heads from MRL tape - for example if you have a tape that's 250nwb/m then a 456 tape would want +4dbu to be considered a healthy level - so line the playback from the MRL to read -4db on the meters when the tones are playing.

I tend to do a general level/eq for playback, and then do azimuth etc.

Then do input lineup and work to 0db always.
Again, general level line up at 1k and 10k, then I'll do biasing - levels are different depending on tape but I always overbias by around 3.5db for 15ips, then back to level/eq check..
It's a bit of a process but quite therapeutic.
If you can get a crib sheet made up and a tech in for the first time, it should be much more hassle free.

this website has some great info too http://www.analogrules.com/basicalign.html
Old 23rd February 2020
  #4
Gear Addict
 
FlyingMusician's Avatar
Quote:
Originally Posted by Jeff A. Roberts View Post
I think you would benefit greatly by hiring a skilled technician to come to your place and show you how to tweak your machine.
Agreed, this would be money well spent and you could take notes so the next time you wish or need to calibrate it, you can just follow your own notes instead of the manual. Once you get the hang of it, it's mostly the same process for all tape machines.
Old 23rd February 2020
  #5
Lives for gear
 
vernier's Avatar
Old 23rd February 2020
  #6
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by fromthepuggle View Post
I'm still mystified about how to calibrate it.
Do you have an alignment tape?
Old 25th February 2020
  #7
I do have the MRL calibration tape for 15 ips, 250 nW/m, IEC 2 calibration tape. Started by cleaning the heads with alcohol, then demagnetized (keeping the demag over 3ft from machine to turn on and off).

Googling turned up this as the best written guide: https://www.recordingthemasters.com/machine-adjustment/

Here was the most helpful video:
This was also helpful:
As a total noob, I didn't even know how to thread the tape until watching this one:

After flipping through these, the manual, and a bunch of other videos, I was able to get most of the steps worked out. The manual was really unclear about a variety of things (like the fact that the azimuth "nut" was the one under the screw, wtf?!). This is really the sort of thing that requires a hands on explanation. Someone did PM me with an offer to do it over skype for $100 and hour. Eek.

The big problem at the moment is the freq calibration of this unit seems undoable as it currently is. After setting input levels, checking azimuth (coarse and fine, all good), started frequencies. Pretty solid up until 2k. Then one side starts to drop off with each higher freq, and by 16k, it's so low that adjusting the screw upwards hits its limit. But then at 20k, the problem reverses channels?!

What could cause that? My unscientific guess is a problem with the heads needing retooling or something. I hope not.
Old 25th February 2020
  #8
Lives for snowflakes
 
12ax7's Avatar
 

From the mind of the late (great) Bill Vermillion:
This is an article on tape alignment that comes from doing this more times than I would care to admit, on 1, 2, 4, 8, 16, 24, and 32 track machines!

Of course be sure to clean the tape path before starting.

De-magnetization (every time) is optional in my opinion. There are some that insist it be done every time, but in our studio we felt that it was easier to introduce problems with it. We also checked the machines with a magnetometer, but typically we thoroughly demag'ed the machines only about once every 1 to 2 months.

Some machines were re-aligned several times in one day. This was because we would be working with source tapes recorded on different media, in different studios at different operating levels.

I had one machine that I did a complete re-alignment on three times in the course of one day. Two different 24 track tapes, one Dolby, and a 16 track setup. After doing this that often we got to be able to set up a 24-track machine in 30-40 minutes, which is about the length of time it took me to do my first alignments on two track machines.

Be sure to use a good monaural alignment tape. (They should all be that way.) There are some multi-track tapes that are recorded monaurally and then have guard bands erased after recording. This will make a difference on low speed playback EQ - but I use a method that elminates any problem with low-frequency fringing effects.)

The steps used to align are as follows and are to be done is this order:
1. Physical head alignment (azimuth alignment)
2. Playback level
3. High frequency playback response
4. Bias adjustment
5. Record level
6. Record high frequency response
7. Low frequency playback
Standard procedure for record head alignment was to align play head, and then adjust record head while during recording watching the playback head. Most multi-track machines and a good many two-track machines now have the ability to put the record-head into the playback circuit (often called Sel-Sync*). This is a much more accurate and prefered way to do physical head alignment.

The first tones on the alignment tape are HF alignment tones. If you have a scope you can ajdust by watching the phase. If not available you watch for maximum output at this frequency. I had the luxury of having phase meters at the studio, this makes it all so much easier.

Playback level is then adjusted. Alignment tapes are manufactured to different recording levels. Assuming you have a tape for the level you wish to record, adjust the playback levels to a 0 reading on your meter. To be precise however you should look at the tables for fringe effect that should be included in the manual with the alignment tape.

Fringe effect is a higher output caused by playing tapes that have a wider record track than the width of the playback head. At our studio we compensated for this as we had standard two-track machines, and we had "stereo" machines. The latter use the European spacing for 1/4" two channel tapes of .75mm. The standard two-track spacing is 2mm. If compensation was not made the tapes will vary in playback when played on a different two-channel format machine. Most studios ignore this, however at the higher speeds it is important. At 30 ips the fringe effect will give a 1db too high a reading at 1000Hz! This will throw your alignment off by 1db at the high end of the spectrum.

Once playback level is adjusted it is important to MAKE SURE that this is not touched during the remainder of the alignment procedure.

At this point you can then make your HF playback adjustments to give you flat(est) response from your alignment tape. These playback calibrations are critical as all the rest of the alignment depends on them.

Now that playback is done the next step is bias, which will affect level and record response.

For bias I ALWAYS adjust for minimum modulation noise as that to my ear is the worst part of mag tape.

To do this pick a nice low freqency tone (I always use about 7Hz) and listen to the noise components when playing back. Cut the bottom end of your playback amps if you must because you only want to hear the noise components.

As you start below the bias point you will heard hf noise pulsed at the 7Hz modulation frequency. As you increase the bias the noise will decrease to a point and then start increase with a change in the "tone" of the noise. Go back to the minimum point. If you do this, you will find that you can set the bias more accurately by ear than you can doing the typical 1-3 db overbias at 1kHz or 10kHz (depending on your choices).

The only tape I have found that is can not be done on is the Agfa 468. Minimum modulation noise will overbias the tape 6 to 9 db on this tape.
I had a machine shut down as I overloaded the bias amps when trying this.
(*NOTE - Since this artilce was written, new tapes such as the Ampex 499 have become available. I do not know if this procecure will work properly with them. wjv)
Many recommend 1db overbias at 1kHz. I find that you should use 10kHz for anything less than 15 ips, and for 30 ips use 20kHz. Typically you overbias 3db at these frequencies, but if you have the chart for your particular brand of tape you can find the exact point. However, except for 468 I always use minimum modulation noise. Agfa recommends a 14Khz audio signal for 468, and I don't remember the exact amount of overbias. They will furnish to you if needed.

After the bias is set, the next step is record level. All you do at this point is set the output to be 0 vu by matching the output level to the level you had previously set on playback of the alignment tape.

At this point you can calibrate the record meters if your machine has record calibration controls. Since the PB level has been matched you go to the record metering side (up to this point you have been watching playback metering).

You then adjust the record CALIBRATION (not level) so that the input levels read 0.

Now that you have the record level set you can adjust the HF record response. The standard that many use is to set 10kHz to be at the same playback level of the 1000Hz tone. I personally disagree with this. I try to make the 20kHz level 0 IF the 10Khz region does NOT increase too drastically at this point. In other words, if I can get 20hKz to zero and keep 10Khz no higher than 1.5 to 2db I'll go that way. I would much rather have SMOOTH wide response, than FLAT response that falls off at the high end.

Depending on the ability of your machine, you MAY have to make the high frequency record alignment adjustments at a lower level. Because of the high freqeuncy pre-emphasis some machine's record amps may not take too kindly at 0db at 20Khz before being overdriven. On the other hand, some pro machines, Studer in my experience, have absolutely NO problems at recording at 6db over standard level at 20kHz and above when running at 30ips. The slower the tape speed the more critical this becomes.

Since we have now calibrated the record level against the play level, if your machine has problems in this area, we can now change the levels. Turn the record level down about 10db. Turn the playback up so that your output at 1kHz is zero, and then proceed to do the HF record EQ as this level. If your machine requires this you should also make sure that you are carefull not to "go into the red" when recording on this machine.

One point I disagree with in most the procedures I have seen, is that many say to touch up the alignment (mechanically) after this you have completed these steps.

I have seen that you can change the physical alignment of the playback head or record head at this point and further peak the output (or bring the phase close if monitoring phase).

However, since you have aligned with a stock tape originally I disagree with this. (And this is my own method that we used at the studio - and it seems to work. However I have not had the time or opportunity to test this theory of mine so I may be way off base).

After all this check the phase response at 20kHz, and carefully adjust the bias on one of the record channels to bring the phase to as close to 0 deviation as possible. You may have to touch up rec eq just a bit because of the bias chnage, and you may have to do this once or twice.

I attribute this phenomenon (In my head at least) to the "bias bubble". The signal is recorded on the trailing edge of the record gap, and the amount of bias will affect just exactly where the trailing edge "seems" to be. This varies with the frequency being recorded. Changing the bias while watching the HF phase will show that this does affect the phase response.

EQ doesn't enter into it. Changing bias will affect the HF record response however, but this should only be level sensitive. The only thing I can think of that would account for this is the slight displacement in the track caused by bias. (As I say - this is my own "theory" and I have never had the time/resources to check it thoroughly - so I may be way off base, but record/play sounds really great done that way. I guess all of us a permitted to have at least one ecentricity :-) ).

After you have done the final hf rec eq, you do the lf pb eq. Never set the LF playback eq from the alignment tape. Except for a very few machines, you have NO control over the low frequency record characteristics of your machine and you want to align your LF playback to your LF record.

Doing the above on an ATR102 - I could get the machine flat within +- 1db from about 30Hz to 20kHz. Tweaking the bias, as I mentioned above, I could typically pull in the 20Khz with less than 5 degrees phase shift. I really loved having a phase meter, as opposed to trying to interpolate on a scope. On a Studer A-800 at 30ips, I could get within about +- 1db from 30Hz to well past 20kHz. The Studer 3db down point was at 33kHz. (One hell of a machine!)

If you align your machine very carefully you will hear great differences between tape brands/types.

I have not had a chance to hear the new Scotch high output tapes, but of the rest of the tapes these would be my choices.

For such things as strings, but without any high level peaks, Scotch 250. Wonderfully quiet. Has more print than I'd like. That's why I stay away from this tape on msuic with large peaks or big endings. You will get echo on the first playback. There is very little modulation noise on this tape.

For voices, horns, accoustically generated music, Scotch 226. Doesn't print like 250, very low modulation noise, minimal asperity noise. Good tape.

For pop/rock. (Things that don't have big gaping holes (rest) or low level vocal tracks) Ampex 456. Seem a bit "brighter" or "harder" than the Scotch tapes. Great rock'n'roll tape. But tends to have more asperity noise (but only noticeable in quiet passages).

All the tapes measure the same (in frequency respone on a give machine) but all have slightly different sound characteristics.

(For those who are not familiar with the term "asperity noise", this is a low frequency noise component. We called it "rocks" in the studio because it is what you would imagine large -really large- boulders to sound like hitting one another. This is cause by slight uneven-ness in the oxide coating. You hear it when you have such things as a soft vocal group - or soft horns. Virtually inaudible unless the music has pauses. More noticeable the higher the recording speed).

And to explode one "myth" here. Worn tape head don't ALWAYS show up by having a degraded HF response. In pro machines the heads have a very deep gap. As the head wears the depth of the metal is less while the gap is the same width. The tip-off here is that you INCREASED HF output.

I found this out when fighting a problem on an Ampex MR-70 and Ampex tech support pointed this out to me. (The MR-70 has to be my favorite all time tape recorder - followed by the AT102 for 1/4" and the Studer A-800 and Stevens 821-B for 2". The latter is a true 'hackers' machine. You have to KNOW the machine to love it, otherwise you'll hate it.)

So while the above procedures may not always follow the book, they are themones we adopted in the studio and the machines always sounded good.

A lot of this information came from trial and error, but to give credit where it is due, some of the best information I have received working in the business came from conversations with John Stevens, who built an amazing tape recorder, John French, of JRF in New Jersey, who remanufactures and builds magnetic tape heads, and Gordon McKnight, of Magnetic Reference Laboratories, who make MRL alignment tapes.
* Sel-Sync is a Trademark of Ampex

(Copyright 1991 & 1995 by W.J. Vermillion.)
source: http://www.recordist.com/ampex/docs/align/aligndek.txt
Old 25th February 2020
  #9
Gear Head
 

Quote:
The big problem at the moment is the freq calibration of this unit seems undoable as it currently is. After setting input levels, checking azimuth (coarse and fine, all good), started frequencies. Pretty solid up until 2k. Then one side starts to drop off with each higher freq, and by 16k, it's so low that adjusting the screw upwards hits its limit. But then at 20k, the problem reverses channels?!

What could cause that? My unscientific guess is a problem with the heads needing retooling or something. I hope not.
Is this issue happening on repro while playing from your MRL? Assuming you set up azimuth correctly, try swapping repro cards to see if the problem follows the card. If it doesn’t, try swapping the whole tracks amplifier to see if the problem follows. If not, it may be the heads. I know a good tech who has new old stock heads for a reasonable price.
Old 25th February 2020
  #10
The bias recommendations from the tape makers are not correct. They also vary for each track. To find the best settings use a THD sweep analyzer, 50~10k sweeps. You will find the 1k THD minimum that way and also see the effects at 100 hz and 10k. Tweak the bias and that THD curve will tilt back and forth. More bias = lower 10k hz THD, less bias and you get lower 100 hz THD.
Old 25th February 2020
  #11
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
The bias recommendations from the tape makers are not correct. They also vary for each track. To find the best settings use a THD sweep analyzer, 50~10k sweeps. You will find the 1k THD minimum that way and also see the effects at 100 hz and 10k. Tweak the bias and that THD curve will tilt back and forth. More bias = lower 10k hz THD, less bias and you get lower 100 hz THD.
Sounds like you're pretty close to Bill Vermillion's "school of alignment" then, eh?

One thing I'd like to bring up here is that I really like to set azimuth with a PINK NOISE tape (like from MRL):

Just flip polarity on one of the channels, put 'em in mono, and try to make 'em null.

You can then adjust azimuth 'till it almost completely nulls and gets really quiet.

It will be a VERY obvious when you get it right (almost dead silence).

Do this on both the play head and the record head (by putting the machine in the "sync" mode when setting azimuth for the record heads).

This really does not need to be done very often, but its a good idea to do it from time to time (just to make sure).

Last edited by 12ax7; 25th February 2020 at 09:26 PM..
Old 4 weeks ago
  #12
Azimith as well as basic alignment is done here with an Audio Precision analyzer. They have the most refined test proceedures and azimuth is one of them. I found it's the only way to look deep enough to nail the alignments, so accurate you have choices to make such as less top end THD or less low end THD. One can then optimize each track for each different instrument if desired.

Working at LA studios with it I used to make charts for the recorders and stick them on the sides. Some were done with several tape types such as Ampex 456 and Scotch 250. That way the everyday AE's could duplicate those settings without any guesswork.

I never found a pro recorder in LA that was set properly after an examination with AP. Sony APR's with the MDAC alignment circuits were troublesome as the 1/4 db increments were set so you were either getting too much or not enough, 1/4 db limitations always missed the sweet spot.

Sony JH24's and JH-110C's got the best results after some circuit mods. I got a 32k hz top end at 30 IPS and got THD down from .55% at +3 to .15% at +9 levels on the GP-9 tape. Wow and flutter was not as good as Studer A-800's but replacing the bearings in the Sony's with grade 9 aerospace bearings dropped the wow and flutter in 1/2. Then the 10k hz tones were rock solid.
Old 4 weeks ago
  #13
OMG. This is what I needed. Thank you SOOOOOO much!!!


Quote:
Originally Posted by 12ax7 View Post
From the mind of the late (great) Bill Vermillion:
This is an article on tape alignment that comes from doing this more times than I would care to admit, on 1, 2, 4, 8, 16, 24, and 32 track machines!

Of course be sure to clean the tape path before starting.

De-magnetization (every time) is optional in my opinion. There are some that insist it be done every time, but in our studio we felt that it was easier to introduce problems with it. We also checked the machines with a magnetometer, but typically we thoroughly demag'ed the machines only about once every 1 to 2 months.

Some machines were re-aligned several times in one day. This was because we would be working with source tapes recorded on different media, in different studios at different operating levels.

I had one machine that I did a complete re-alignment on three times in the course of one day. Two different 24 track tapes, one Dolby, and a 16 track setup. After doing this that often we got to be able to set up a 24-track machine in 30-40 minutes, which is about the length of time it took me to do my first alignments on two track machines.

Be sure to use a good monaural alignment tape. (They should all be that way.) There are some multi-track tapes that are recorded monaurally and then have guard bands erased after recording. This will make a difference on low speed playback EQ - but I use a method that elminates any problem with low-frequency fringing effects.)

The steps used to align are as follows and are to be done is this order:
1. Physical head alignment (azimuth alignment)
2. Playback level
3. High frequency playback response
4. Bias adjustment
5. Record level
6. Record high frequency response
7. Low frequency playback
Standard procedure for record head alignment was to align play head, and then adjust record head while during recording watching the playback head. Most multi-track machines and a good many two-track machines now have the ability to put the record-head into the playback circuit (often called Sel-Sync*). This is a much more accurate and prefered way to do physical head alignment.

The first tones on the alignment tape are HF alignment tones. If you have a scope you can ajdust by watching the phase. If not available you watch for maximum output at this frequency. I had the luxury of having phase meters at the studio, this makes it all so much easier ...
source: http://www.recordist.com/ampex/docs/align/aligndek.txt
[/INDENT]
Old 4 weeks ago
  #14
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by fromthepuggle View Post
This is what I needed. Thank you SOOOOOO much!!!
You're quite welcome!

I learned a lot from Bill (and he was always quite the gentleman).

Stuff like this is starting to become "lost knowledge", so I'm glad to pass it along (as best I can).

If you understand what Bill wrote (and read the maintenance manual for your machine) all you need is a good test tape and basic test gear, and you'll be golden!

The only caveat I would give about that paper is that when Bill wrote it, 3M and Ampex were still making tape (so things might be a bit different with the new stuff maybe?).

...Still, his paper is the most valuable resource about the subject that I know!

Last edited by 12ax7; 4 weeks ago at 10:31 PM.. Reason: Guess
Old 4 weeks ago
  #15
Ok, tried to get this done with the resources above, still not quite there.

1) Still having issues with one channel. I swapped the cards, all cards work on one side, but the other side I see levels on record and playback, but I don't hear the playback except as seeming crosstalk from elsewhere. What could lead to this?

2) The way I'm doing azimuth is recording the signals from the deck and playing back into Logic's goniometer. Repro and playback are producing a nearly perfect vertical line, no oval or circule. This means azimuth is aligned, yes? I've seen this be 45 degress when others adjust, not sure what's going on here, really a noob with this.

3) From what I've found, for 'thick' tape tone, I should bias my RTM911 tape 6db. Is that 6db below 0db? Am I correct that I increase bias adjust all the way up, lower it until there's a rapid 'falling off', that's the peak, set THAT at the bias point? What does 'bias calibrate' screw do then?

4) After reading and watching a lot of sources, the precise order is still a bit of a mystery. Unless I'm wrong, FIRST set playback levels using the FIRST two tones on the playback head. THEN set high freq with the series of tones. THEN do azimuth on repro head, then recording head. THEN do bias.

5) The manual says if its set to 4db output on back, should be calibrated with levels at -4db. Does that mean whenever anything above is supposed to be set at 0db, it's really -4? Does this also mean the biasing point goes down an additional 4db?

6) With eq, I was able to get 63Hz matched perfectly on playback head, but 10kHz the screws didn't let me raise the level enough to match, so I got them at least equal. 16kHz is way low on one side, 20kHz on another. Any ideas on this?

Thanks in advance for any help!
Old 4 weeks ago
  #16
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by fromthepuggle View Post
the precise order is still a bit of a mystery.
It is extremely important to do things in the right order!
If you really want to be thorough (like on the first alignment you do on an old machine):
Go through the entirety of the following two chapters of the Ampex 440B Operation And Maintenance Manual, and do EXACTLY (to the letter) as they say:
Part B: Preventive Maintenace
After completing (to the letter) the instructions in Part B:

...Only THEN go through Part C (and do EXACTLY as it says):
Part C: Adjustment and Alignment
If you follow ALL of these steps religiously, (and in the right order) and it will make all the difference in the world!

Last edited by 12ax7; 4 weeks ago at 07:21 PM.. Reason: Precision
Old 4 weeks ago
  #17
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by fromthepuggle View Post
really a noob with this.
No problem:
Jack Mullin was once a n00b, himself!
Old 4 weeks ago
  #18
Gear Nut
 

Regarding Q#3, you need to overbias, not bias to peak and then back down. You will be measuring past the peak, that is the falling off you are thinking of. Each tape formula will have a guideline, each speed will use different calibration, and setting by ear with subsonic tones is it's own unique process. It's the most subjective part of the alignment, but once you understand the what / why, it becomes an easy process. I've had excellent results using both subsonic artifacts and AP scope measuring 10k, learn both and see what you dig.
Old 4 weeks ago
  #19
Lives for snowflakes
 
12ax7's Avatar
 

Quote:
Originally Posted by jeffsochor View Post
you need to overbias, not bias to peak and then back down.
Yes.
We speak of "dB of Overbias"...

...Meaning that after injecting more and more bias ('till the resultant output level "peaks"), we then continue to INCREASE the level of bias a bit more until the resultant output goes DOWN (by the amount we want).

That's why why we call it "OVERbias".
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump