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 1 
 on: Today at 03:58:34 pm 
Started by leftofthedial - Last post by leftofthedial
Also, FWIW, I see no real reason why setting the record head first would be problematic on a 3 head machine in sync mode.  The A800 has the ability to go as high as 16K in sync mode.  That's not how I have been proceeding, but I'm pretty sure I saw a video of Greg Norman at Electrical do the rec/sync head in sync mode on one of their A820. 

 2 
 on: Today at 01:16:55 pm 
Started by leftofthedial - Last post by leftofthedial
Thanks for all the responses.  I've had the machine for 3 years, but have not used it yet in a recording with a client situation.  I have been taking my time recapping things and working out all the electronic and mechanical stuff as time permits.  I generally doubt that my original hypothesis of zenith being off is actually what is going on. FWIW, I also have not touched anything but the azimuth screws on the head adjustments because I know I will only make it worse if I do.

 3 
 on: October 12, 2019, 12:01:21 pm 
Started by leftofthedial - Last post by mbrebes
Most of the tape machines I have worked on rarely have the azimuth go out on a regular basis, at least when they are all in-house tapes.  If the azimuth goes out, even in a 48 hour period, I would suspect something wrong with the head assembly mechanics.  If you are using tapes that are from out of house, yes the azimuth will need to be checked, but it shouldn't go out while you are working with that same tape.

 4 
 on: October 11, 2019, 04:05:37 pm 
Started by leftofthedial - Last post by RadarDoug2
One thing I meant to cover on the original post. Use a two channel scope to do azimuth. Start with the low frequencies, and satisfy your self that you are on the same cycle of waveform on both channels. This is easy at low frequencies, not so easy at high frequencies. Work your way up in frequency, checking for each frequency that you are on the same cycle of audio. Its very easy to just use 10K and get a cycle out. This then has the head on a slight slant, and azimuth is definitely out!

 5 
 on: October 11, 2019, 04:01:29 pm 
Started by leftofthedial - Last post by RadarDoug2
A couple of things... first, when you do "azimuth", you it on the two exterior channels... as in 1 & 24.  When 1 & 24 are good... all the ones in the middle are good.  When you do "azimuth" you first do the record head... then you record the tone [I generally recommend 15kHz, but I do know some guys the use 20kHz... you can "rough it in with 10kHz, but use that only as a "rough" alignment].  After you get the record head straight [no pun intended], you record the tone and align the repro head... that way the two are exactly in line.

What scares me a bit is you started by saying "that I've had a few years" -- I hope to hell you recorded 15kHz alignment tones [along with the standard 1kHz, 10kHz, 100kHz (on an 800, I usually run my low frequency tone at 50Hz as there is a bit of a "bump" at 100Hz and I find a "larger" sounding low end when I align 800's with a 50Hz tone... but that's for you to decide].  If you didn't -- your azimuth will be WAY out of whack on ALL the previous reels you've had on the machine!!!

Last, and certainly not least... azimuth should actually be checked [along with the alignment of the electronics 1k, 10k, 50Hz] before EVERY session.  If its a "home studio" kind of thing, maybe every 20-25 hours of use... but this is something that you need to stay on top of 100% of the time if you want a recording that sounds correct.

Peace
WOW! Really bad advice Fletcher. You always do the REPRODUCE head first! Then you do the Record head by observing what comes off the reproduce head. You dont do the record head in sync. Some machines have filters on the record head in that position. Also the actual position of the record head azimuth is affected by bias, and the physical position on tape of the recorded signal depends on the transfer function of recording, so just setting record head azimuth in sync does not allow for where on the head recording happens. A subtle but important difference.
Taking azimuth from tracks 1 and 24 is bound to be bad. Very easy to get cycles out at high frequencies. Start with adjacent tracks in the middle of the head. Then work out observing azimuth as you go. If the azimuth varies drastically, you have a head with a bowed gap.
If you always record stereo pairs on adjacent tracks, then the azimuth error will be minimised. If you are multimikig a band, time delays in the room will cover all the strict phase problems.

 6 
 on: October 10, 2019, 02:45:02 pm 
Started by mikezietsman - Last post by klaus
Too little visual information to make an educated guess as to the validity of the conversion and the effect on value: no capsule, inside amp or power supply views. Also: the connectors are no longer Tuchel, but East German copies which are not compatible with Tuchels

If the mics were "factory" converted to U67, there should be Neumann-issued documentation. If not, the value drops, and the mics' intrinsic (usable) value will be your base line for pricing.

Also: always  think of the other end of any Frankenstein deal, i.e. when it's YOUR time to sell: how much explaining will you have to do?

Take all of this into consideration before you bid.

 7 
 on: October 10, 2019, 07:06:59 am 
Started by mikezietsman - Last post by mikezietsman
I'm not sure if it is in the scope of this forum but please could we have a discussion about these microphones:

https://www.ebay.com/itm/Matched-Pair-of-Vintage-Neumann-M269-Microphones-Mics-with-cases-cables-and-PSU/123823697475?hash=item1cd477ae43:g:3SAAAOSwd8hdHVm7

"Factory modified with ef86 to avoid the hassle and expense of ac701k"

As an owner of an unmodified u67 and m269c I know how similar they sound. But surely this modification makes these mics into u67s?

And even though they are factory modified surely there would a be a corresponding drop in value? Or maybe these are just u67s with m269 bottom bells?


Given the "factory modified" line I would personally expect more detailed info about the power supplies and modifications (as well as pictures?)

Anyways, I am not interested in purchasing the microphones but it is an interesting discussion (at least I think)

 8 
 on: October 09, 2019, 10:55:59 am 
Started by leftofthedial - Last post by Timtape
I think the zenith is off on the record head.  Although the service manual implies that is unlikely :).  Obviously something or someone has messed with the head height screws at some point. The ones service manual says to never touch.


Hi, what makes you think the zenith is out?  If the zenith has been correct for some time, the wear flat will be pretty much the same, with maybe a widening at the extreme ends, top and bottom. Normally if zenith has been out for some time, you'd see a head with a wider wear "flat" at either top or bottom of the head. This  leads to upper or lower tracks wearing out before the others, shortening the life of the head. It also means tape pressure across the head tracks is not even, possibly leading to poor tape to head contact (spacing loss) at the place of weakest tape pressure. Like very wide tires on a car, alignment is critical.

I'm not familiar with that machine. Some have no provision for head zenith adjustment. As the manual says, normally the alignment shouldn't go out but all it takes is one turkey to mistake a screw for the azimuth, start fiddling and things start to go pear shaped. I've serviced many tape machines for decades and usually the cause of head misalignment (at least in quality machines) is a local dude "having a go" but not having a clue what he's doing.

As mentioned, inspect the wear "flat" from top to bottom, if necessary with a magnifier in a strong light. 

 

 9 
 on: October 08, 2019, 12:34:03 pm 
Started by leftofthedial - Last post by Fletcher
A couple of things... first, when you do "azimuth", you it on the two exterior channels... as in 1 & 24.  When 1 & 24 are good... all the ones in the middle are good.  When you do "azimuth" you first do the record head... then you record the tone [I generally recommend 15kHz, but I do know some guys the use 20kHz... you can "rough it in with 10kHz, but use that only as a "rough" alignment].  After you get the record head straight [no pun intended], you record the tone and align the repro head... that way the two are exactly in line.

What scares me a bit is you started by saying "that I've had a few years" -- I hope to hell you recorded 15kHz alignment tones [along with the standard 1kHz, 10kHz, 100kHz (on an 800, I usually run my low frequency tone at 50Hz as there is a bit of a "bump" at 100Hz and I find a "larger" sounding low end when I align 800's with a 50Hz tone... but that's for you to decide].  If you didn't -- your azimuth will be WAY out of whack on ALL the previous reels you've had on the machine!!!

Last, and certainly not least... azimuth should actually be checked [along with the alignment of the electronics 1k, 10k, 50Hz] before EVERY session.  If its a "home studio" kind of thing, maybe every 20-25 hours of use... but this is something that you need to stay on top of 100% of the time if you want a recording that sounds correct.

Peace

 10 
 on: October 08, 2019, 12:29:21 pm 
Started by ElvisY - Last post by klaus
Experts recognize most re-diaphragmed capsules even from a photo, but some can only be determined through physical inspection.
I wrote about this before: with each tell-tale sign or investigative method made public, fakers will make it yet one step harder to tell.

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