From: cd@notformail.com   
      
   On Sat, 10 Jan 2026 22:25:54 +0000, liz@poppyrecords.invalid.invalid   
   (Liz Tuddenham) wrote:   
      
   >Cursitor Doom  wrote:   
   >   
   >> On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid   
   >> (Liz Tuddenham) wrote:   
   >>   
   >> >Cursitor Doom  wrote:   
   >> >   
   >> >> On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid   
   >> >> (Liz Tuddenham) wrote:   
   >> >>   
   >> >> >Cursitor Doom  wrote:   
   >> >> >   
   >> >> >> Hi all,   
   >> >> >>   
   >> >> >>  I've identified an issue with my Uher tape recorder and I'd like your   
   >> >> >> opinion. There's a problem with the audio amplifier chain. I've   
   >> >> >> eliminated all other possible causes like dirty heads or faulty tape   
   >> >> >> etc etc. So when I'm listening to playback, the quality is frequently   
   >> >> >> varying from 'pretty good' to 'really quite crappy'   
   >> >> >   
   >> >> >Does it become good and bad at the same places each time you play the   
   >> >> >same tape?  If it does, the problen is in the recording.   
   >> >>   
   >> >> Yes it does. But that recording still had to be processed through the   
   >> >> amp chain.   
   >> >   
   >> >I can't follow your logic.  If the tape sounds good in some places and   
   >> >distorted in others - and these are the the same places each time you   
   >> >play it - the fault is clearly something to do with the tape and not the   
   >> >amplifier.   
   >>   
   >> Makes no sense to me, that observation. The tape is brand new and from   
   >> a well-respected manufacturer. Think about it, the signal on the tape   
   >> didn't get 'impressed' there direct from a microphone or whatever, it   
   >> had to be amplified. It had to pass through the amplifier chain and be   
   >> mixed with the output from the bias oscillator, so whatever defects   
   >> were present at that moment from moment to moment from the amp as the   
   >> tape passed, will be faithfully recorded and re-playable.   
   >> I assume we're not on the same page, so will not address your   
   >> follow-up until we're straight on this one.   
   >   
   >My apologies, I was assuming you were playng back a tape that had been   
   >recorded some time ago and it had recently begun sounding distorted.  I   
   >hadn't realised you were looking for the cause of distortion in the   
   >*recording* amplifier.   
   >   
   >In that case you need to monitor the signal going to the recording head   
   >(preferably just before the point where the high-frequency bias is   
   >added).  If that is clean, suspect there is poor contact between the   
   >head and the tape.  The head-tape contact is far more critical on record   
   >than on playback.   If the bias is varying, that can cause all sorts of   
   >problems but that is much less likely to be happening.  Frequency   
   >modulation of the sound by tape head squeal is another possibility,   
   >especially with new tape that might have a manufacturing defect, or very   
   >old tape that has begun to deteriorate.   
   >   
   >Dirty contacts in the record/playback switch can manifest themselves as   
   >variations in signal level and distortion and are more likley to occur   
   >in a machine that hasn't been used for recording for a long period..   
   >....But, the head-tape contact should be your first suspect.   
   >   
   >My previous remarks about distortion being much easier to detect by   
   >listening, rather than with an oscilloscope, still apply.  If you have a   
   >sinewave signal generator, that will make it much easier to hear   
   >distortion than  trying to spot subtle changes by listening to programme   
   >material.   
      
   Okay; noted, many thanks.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)