From: liz@poppyrecords.invalid.invalid   
      
   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.   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)