On Sun, 6 Jul 2003 16:46:41 +0100, "harrogate"
wrote:

I did mine years ago - and the 33 as well. Almost anything you get now will
be better quality than the originals - I think mine originals were Mullard!
Solid aluminium electrolytics will do fine - just make sure the voltage
rating is the same or higher. If you can't get them then try tantalums -
more expensive but equally effective.

I looked into tants but have generally avoided them, especially in the
303 power amplifier because the can fail as a very low impedance short
circuit. Also, the ESR is often higher than for an equivalent solid
aluminium device.

After doing some frequency and phase sweeps on the 33 I built replacement
amp boards using TL074 bi-fet op-amps. The effect was noticable. They went
from a response of 50Hz-18KHz at -1dB to 22Hz-243KHz! Mind you, that may be
because I took the tone controls out of circuit in the process! The only
disadvantage was slightly increased hiss.

One reason for replacing the capacitors is to reduce hiss and,
especially, hum. This is much more audible now that the amplifier is
driving more efficient speakers. It is possible to buy replacement
boards for the 33 which also use IC amplifiers - see the URL in my
earlier post. (I remember the early publicity for an amplifier that
boasted using ICs, providing more than 100 transistors. To which one
might add, every one of them a potential source of noise.)


--
Chris Isbell
Southampton
UK