Importance of warm up. I hope this helps someone

Thanks for the input everyone. I always heard warmup was important. I thought I could hear a difference but did not have a good example to go by. There was a big difference. From thin or slightly shrill to a more rounded sound with more bottom end. Mike

I think warm up can be important (and if your CD player doesn't have tubes in it, I recommend you just leave it on all the time), but I am skeptical of the results you report. Cassettes copies are never that good, at least in my experience. When you say the cassette was a "perfect copy" of the CD, did you listen to the new cassette in the exactly the same way you listened to the one you made previously when you decided that it was imperfect? Or did you make this determination by flipping the Tape/Monitor switch on your preamp while you were making the second recording? Rapid A/B switching obscures sonic differences.

Speakers will change response as heat builds up in the voice coils --- you get thermal compression after some minutes of play as the coils inside the drivers warm up. As you play louder the compression will get worse...anywhere from 0.5 to 3DB or more in compression can be expected (enough to be plainly audible). On passive speakers it will also affect the way the passive crossover behaves as the filter will drift slightly.

This effect is volume level and speaker design dependent.....it might possibly be the source of your problem. Certainly, speaker thermal compression could cause the sound to go from a bright sound to a duller sound.

If you have ever played a track very loud (at the beginning) and then found yourself increasing the volume a few minutes later then you have probably experienced speaker thermal compression. (Not to be confused with an old Vinyl trick where the mastering engineer deliberately increased the level at the start of the track to help it sell...as loudness is often interpreted as better sounding)

G'luck!

Drublin, Thanks for your comment. After the tube cd player warmed up there was virtually no difference between the CD and tape. I have a very good tape player. Clean and demagnetize after every tape. I use Kimber KCAG cables. Use silver SST contact enhancer. I correct azimuth for each side. After I have manually set rec current and bias per manual, I then make a test recording and then readjust until I am satisfied that there is little or no perceptible difference. When I go to the other side I then test again and make adjustments. I am a nut about AB comparisons. I do that all the time. I do flip fast from source to tape but leave it for 5-10 secs and then flip back fast. There was only one cassette recording I mentioned.above. I did not record a 2nd time. After CD player warmed up I could tell no discernable difference from the month old cassette. Sometimes when I record I do hear a difference. If I cant get it right I'll junk the tape if its an old one. I always warm up tape player several hours before making a recording. The headphone jack on tape player does sound shrill until it has warmed up a while. I dont need an AB comparison for that one. I know the cassette medium has virtually become extinct. I am a dying breed. It is something I like to do.

Shadorne. Thanks for the tech info about speakers. I was using headphones. I too have noticed loudness levels on begining and end of record. I see that on the tape vu meters. I know the importance of vol levels. I will adjust CD output to same loudness of record when doing AB. When I am recording I often find the correct recording level is when you cannot hear a loudness difference between tape and source. Thanks again for response