Burn-In: real or imagined? A proposed experiment.

[Spikedart]

speakers. new ones, and ones that have had surrounds replaced definitely can change over time. I guess that could be considered burn in. I noticed this first when I bought a brand-new Ohm F head and it sounded completely different from the other 2 until several months later. the second time was with my first refoam project, a set of version 1 EPI 100's. The bass was absolutely missing and when I ran a pink noise through the amp, I took a snapshot of the frequency response which showed a huge drop starting at around 90 Hz. I thought I had done something wrong, but the shop I bought the foams from said they might not sound right for many hours as the surrounds needed to be broken in. Weeks later I thought they were better and a new snapshot with the same input settings showed solid bass to nearly 50 Hz.

I have read that some capacitors will change their sonic characteristics over time due to usage. I don't know for sure.

[JonL]

Earlier this weekend I installed my new SMMC-2 cartridge on my B&O TX-2 turntable. I thought that this would be a great opportunity to conduct the experiment that Arkay proposed. I recorded three different tracks as soon as the cartridge was installed. The only time the cartridge had on it before the recording was the few seconds it took to set the recording levels on my cassette deck. The first track was the opening song from Emmylou Harris' "Quarter Moon In A Ten Cent Town." This was chosen because it is a track I'm very familiar with. The next was the opening track from Phoebe Snow's "Never Letting Go." I chose this because I'd been listening to the record a bit lately and it struck me as being pretty well recorded, it's an "RL" mastering as well. The last track was the first 5 minutes or so of the Nutcracker Suite from the RCA Victor "Royal Ballet Gala Performances" disc. This is a "TAS Superdisc," and I had never played it before because of it's high value. I wanted to wait until I had a better cartridge to play it. (As an aside, it did have exceptional sound except for some very noticeable distortion on the left channel only during some trumpet passages, and they weren't especially loud. I don't know what's up with that.)

The methodology was as follows. The deck is a Denon DRM-800A that hasn't seen much use in it's entire life (I've owned it since new), and has probably under 10 hours in the last 15 years. I did not clean or demag the heads before this exercise. Tape used was a Sony UX-Pro C-90. I had settled on this tape as a good match for the deck way back when. Unfortunately I had no new tapes, so I am taping over something I don't need to keep. Using a different turntable, I set the deck's bias by switching between source and tape (it's a three head, double dolby deck) and trying to keep the high frequency balance similar. This was done with headphones. Back in the '80s, I was unable to tell the difference between CDs and copies made on this deck. Now, however, I could hear a fairly obvious difference between the LP source and the tape. The LP had a richer midrange. Recordings were made using Dolby C. I then switched in the B&O/Soundsmith. I had to reset the recording level because the Soundsmith has lower output than the Grado on the other table. I set the levels for peaks at +3dB (I can't hear distortion even at +7dB with this deck and tape combination). I then rewound the tape, re-cued the disc, and taped the first song. I stopped the turntable at the end of the song and fast forwarded the tape to allow enough time to record that first song twice more and then I cued up the second song. I followed the same process and again for the last selection. I did not alter the recording level between tracks, nor will I alter it before retaping these selections in 50 or 100 hours. Phono stage is a PAS-3x that is bone stock and original except for the filament supply diodes and capacitors.

I haven't been tracking actual playing time on the cartridge, but I have been keeping track of how many sides I play. I'll figure an average side length and calculate the time. So far I've played 28 sides!

I'll check back in a few weeks when I've got some significant time on the cartridge.

[timofred]

Thank you for offering your "ASS".
It sounds like a very fine proposition.

As I will get a new cart soon, I will get the tape deck hooked up and see what transpires.

[Arkay]

JohnL, looking forward to the results of your experiment; thanks for trying this!

The only question I might have is using a tape deck with so little use on it, only 10 hours in the last 15 years. I wonder if some improvement might not come just from "burning in" (i.e., "waking back up") the tape deck, after so much idleness?! Hopefully --and probably-- that won't be an issue.

[JonL]

The deck's 10 hours in the last 15 years have mostly been accrued in the last six months. It gets some use, but not very much. It hasn't recorded anything in years before this, however. If it means anything, it won't be making any other recordings before the next round in this experiment either. I don't think I'll even remove the tape from the well.

It's by no means a perfect experiment but it ought to show if there is a marked difference due to cartridge burn-in. I think your point about using the deck more before the experiment is a good one. Also, I'd have liked to have a new tape, and perhaps even a metal tape (though I don't think I've ever used one in this deck). It also would have been good procedure to clean and demag the heads, then make some test recordings to make sure everything was "just right." It also would've been a smart idea to run a control recording first... tape a selection with the burned-in Grado just before using the SMMC-2, and then tape the same selection with the Grado at the end of the experiment to make sure that any changes noted were really due to burn in on the SMMC-2. Well the next guy can learn from my mistakes! I was surprised that I had the patience to set everything up before listening to my new "toy." In fact, I got the cartridge on Tuesday or Wednesday, and spent the next few days rearranging my rig's layout, wiring the "special" position on the PAS-3x to accept a 2nd mag pickup input (per the Dynaco original instructions), getting the tape deck set up with "decent" quality interconnects, etc.