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Back more years than I care to remember, we used to run a Ampex 3200 
series duplicator line at one of the studios I worked at. As I recall, 
we did do some actual tone burst and square wave measurements to 
determine whether running the line backwards would result in superior 
transient response. I believe we did come to the conclusion that program 
material which contained steep leading wavefronts would benefit from the 
approach.

Another reason, though, was that most of the material we were duping 
were mono and two track stereo programs, which were usually shipped 
heads-out to the users, so we saved a lot of work rewinding the tapes 
after duping.

Scott D. Smith
Chicago Audio Works, Inc.


Tom Fine wrote:
> This backs up what I have experienced here. The reverse-copied tracks 
> can (but don't always) sound "crisper." And yes, Richard is right -- 
> reverse polarity. You will probably hear a difference with that, too.
>
> As I said in my previous post, I'm not sure what's "right" vis-a-vis 
> fidelity since you're not playing it back on the machine on which it 
> was recorded and all head-playback electronics-alignment combos have 
> some sort of sonic signature, be it mild or not.
>
> Finally, Richard is 100% right about low-fidelity oral histories. It 
> gets more debate-worthy when you get into an instance like well-made 
> music recordings that are 1/4-track 7.5IPS and you want to ingest all 
> 4 tracks at once.
>
> Oh, and regarding duplicated tapes ... the unfortunate truth is that 
> there is almost never an azimuth match in the two "sides." The reason, 
> especially with quarter-track 7.5IPS reels duped back in the "golden 
> age" days of the late 50's and early 60's, is that there were two 
> record heads that were almost never in perfect alignment. I think SOME 
> but not all later cassette dupers had 4 stacked tracks, but most 
> formats from the days of Ampex 3000 series dupers had pairs of record 
> heads, one for the "side A" tracks and one for the "side B" tracks. 
> 8-tracks would be four and four, from the heads I've seen and dupers 
> that have been described to me.
>
> The practice I ended up adopting for quarter-track tapes with music is 
> just charge for the time required and ingest one side at a time with 
> an azimuth tweak each time. With home-made tapes, if the azimuth was 
> _really_ well aligned at the factory, you can sometimes get away with 
> a 4-at-once ingestion, but a sharp-eared client can hear the 
> difference with transients and may not like his two sides sounding 
> different.
>
> -- Tom Fine
>
> ----- Original Message ----- From: "Robert Cham" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, October 08, 2009 6:03 PM
> Subject: Re: [ARSCLIST] Reverse engineering
>
>
>> I should think that it isn't relevant to digital copying at all, but 
>> back in the analog '70s we used to high speed dub reel to reel tapes 
>> backwards because seeing a decay as a transient was much easier on 
>> the electronics than an attack, especially a percussive one.  That 
>> was the recommendation of Ampex, who built our duplicators.
>>
>> Bob Cham
>>
>>> Back in the day when duplicating tapes was a day job for me, they 
>>> said that side 2 of cassettes duped ay high speed both sides at once 
>>> would sound better than the side 1 would. Never made much difference 
>>> on cassettes, especially at 64 or 128IPS dupe speed, but some people 
>>> told me copying 2 tracks worked better in reverse too... They said 
>>> the electronics could respond to transients backwardsbetter than 
>>> forwards. I have no empiric evidence of this though.
>>>
>>> Just old tape tales by now, but this had me thinking back... or 
>>> backwards!
>>>
>>> I have transferred some quarter track tapes doing all four tracks at 
>>> once top a four channel A/D, and not noticed a significant 
>>> difference, but it is easier to do them one side at a time as then 
>>> they end up tails out, as long as it is an hourly job and not a mass 
>>> flat fee transfer project.
>>>
>>> Hope this isn't irrelevant!
>>>
>>> Lou
>>> Lou Judson
>>> Intuitive Audio
>>> 415-883-2689
>>>
>>> On Oct 8, 2009, at 1:59 PM, Richard L. Hess wrote:
>>>
>>>>
>>>>> It's not the digital realm, its the way the reel electronics 
>>>>> handle transients and phase
>>>>
>>>> There appears to be waveform differences between playback in the 
>>>> two directions after accounting for the polarity flip. To my ears, 
>>>> this is an acceptable tradeoff for copying oral history tapes in 
>>>> half the time. This is especially true of mid-to-low-fi recordings 
>>>> such as some 3.75 and most 1.88 in/s reels.
>>>>
>>>> Cheers,
>>>>
>>>> Richard
>>
>