Re: New Pi 5 (Diversity - good or bad ?)

On 17/01/2025 06:01, 186282@ud0s4.net wrote:

No. He (and his dad)  built his  own guitar, but I think the pickups were P90s. The amp was always a (number of)  Vox AC30(s), well known for a unique sound due to stuff you wouldn't be interested in

    Hey, we're tekkies here - we're interested in lots
   of stuff  🙂
    From May's sound, it's clear the amp has a somewhat
   exaggerated higher-end response with some interesting
   harmonics. A lot of the older transistor amps had
   a kinda 'hard' sound too and kinda heavier on the
   odd harmonics. Dunno if that was inherent, or
   by-design - intentionally emulating the AC30 sound.

The AC30 is a development of the original Mullard application note to use four EL84s - a small pentode - as a 25W power amplifier. Subesquent units used a pair of EL34s.
Being British, when it needed more gain, instead of adding an extra tube, they simply *removed the negative feedback* from the power amplifier.
You don't care much about distortion in a guitar amplifier.
Of course this had another effect, instead of just increasing the gain it increased the output impedance so much (~100ohm) that the loudspeakers were practically current driven, rather than voltage driven.
This had two effects. The first one was a result of the induction of the loudspeaker voice coil. Normally with a constant volatage, you get constant-ish output with frequency. But with a high impedance feed the loudspeakers got effectively a 6dB per octave treble boost all the way from somewhere around 1kHz. To tame this they added a simple 'tone control' that rolled off the treble only.
The other effect was that the loudspeaker cone was no longer tightly controlled by the amplifier - it was free to flap. And it so happens that the two 12" loudspeakers and the open backed cabinet had both a nice woodenish  cardboardy sort of sound and a massive bass resonance peak at around 100Hz, which is very close to and lies between bottom E and bottom A on the guitar.
All this made for a classic 'boom and chink' sound perfect  for the beat groups of the era, and all with as few valves (tubes) as they could get away with.
British amps sounded good because they were in fact BAD. Whilst a Fender is a reasonable copy of a hi fi amplifier of the period, British designs were over driven done on the cheap and had in many cases horrible distortion.
The Marshall being the prime example of 'all of the above'.  The classic 'attack' is caused by the amplifier having plenty of HT voltage - until you want to sustain power. Then the mains transformers sighs and gives up.
So a 'power chord' has a sharp attack and then sustains at lower volume...
--
It is the folly of too many to mistake the echo of a London coffee-house for the voice of the kingdom.
Jonathan Swift