Re: Estimating transformer quality by size
- From: "Andre Jute" <fiultra@xxxxxxxxx>
- Date: 31 Dec 2005 03:10:27 -0800
Ian Iveson wrote:
> Seems to me it should be possible to estimate the likely quality of
> a competently built amplifier by comparing the size of the OPT with
> that of the output valves.
>
> What would be a healthy volume ratio for EI transformers, and how
> much would this change with toroids, C-cores, etc?
>
> So many ready built amplifiers, particularly from the Orient, appear
> to me to have very small OPTs.
>
> cheers, Ian
This is a smart post. All the good transformers I have ever had (over
twenty different brands) were hefty. All the lightweight ones were
crap. Unfortunately, it is also possible to make a big heavy
transformer incompetently, so we cannot put our minds in neutral and
judge by the scales alone.
All the military surplus transformers and chokes I ever had, all good
quality stuff, were hefty.
All the good modern commercial tube amps I have sport massive pieces of
iron.
However, at the commercial end, vintage gear now highly regarded didn't
necessarily have what today we would regard as even adequate iron,
never mind exceptional. An example that sticks in my mind was is the
Peerless TFA-204, said to be the official replacement for the WE91 OPT.
The pair I had, claimed to be wound by Magnequest as a faithful copy of
the original off the Peerless blueprint were twee things. The primary
inductance was around 6H ("around" because the pair I had varied by
10%).
The problem with an undersized tranny isn't just a lack of bass, it is
that it sounds unbalanced because the human ear expects a balance
between bass and treble, so that an amp without anything below 50Hz
should probably not have much extension above about 12kHz. One of the
reasons old tube radios with poor amps and poorer speakers sound so
good is that the amp and the speaker are so well matched to expectation
at the ear.
Andre Jute
.
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