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 Judson
>>Intuitive Audio
>>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.