(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
>On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid>
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> 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.
>
Turn down the volume and listen carefully to the tape transport - is it
squealing during the distorted passages? Does the tape each side of the
head block appear to be running normally or is it shuddering because of
patches of sticky-shed? Rest your finger gently on the feed spool and
feel for any vibration, then try gently putting a bit of load on it
until the tape slows down a fraction. If it is unduly sensitive to the
load test or stops dead with little pressure, there is some sticky gunge
lurking somewhere you haven't looked yet.
>
[...]>in your considered opinion, is the most likely cause of this problem>
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Make a probe to feed the signal into on a high-impedance, high-gain
amplifier and trace the signal through the machine. Is it diistorted at
the playback head? At the volume control? At the line-level output?
At the loudspeaker terminals (you could have a damaged loudspeaker)?
A scope would function in such a role just the same AFAICS., would it
not?
Depending on the type of distortion, it might be quite difficult to see
on a 'scope but very obvious to hear through an amplifier. On a 'scope,
distortion of 10% on a sinewave will show up if you know what you are
looking for - but on complex programme material even 30% may not be
detectable on a 'scope trace. On a listening test, as little as 2% is
detectable on sinewaves and 'clean' programme material - but with
material that has been distorted for 'musical' effect, all bets are off.
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