Audio Amplifiers

There has been a few "tube" amps where the tubes weren't connected to anything they just had an LED glowing through to bottom

-Lasse

Those are the optimum design ;-) ...Jim Thompson

I know. I've been tempted to plug my ears and provide the optimum solid state curve-fit to toob distortion... just for the money >:-}

Yep. It appears they're making a big-time come-back. Reading photography magazine at doctor's office yesterday... there are some serious $5K-$10K FILM cameras being reviewed... $5K-$10K BODY ONLY ;-) ...Jim Thompson

Wow. I guess some people have figured out that the film photography is a richer experience overall than digital, for all its relative disadvantages. Turntables are selling out again, so I guess film cameras might also enjoy a revival. Better get me an old classic Leica or Hassleblad before they become unobtainable!

ECC83s, yes I've got quite a lot of those; Mullards mostly. Anyone remember Mullard?

Yep. I still own an ancient, belt-drive, Rek-o-Cut turntable. I probably should avail myself of various softwares to copy platters to CD's... I have quite a few 33RPM records. ...Jim Thompson

Yep. One of my several toob builds when I was a kid used ECC83's in the preamp and KT88's in the output.

(I grew up in a radio & TV repair shop and my dad provided me with an account at the local parts wholesaler ;-) ...Jim Thompson

Absolutely. They used to have some very sharp guys, including the ones who designed Hanbury Brown's photon correlator, all with discrete BJTs.

Cheers

Phil Hobbs

Now compare that with the usual surface noise output from a MM pickup playing a LP.

.... Phil

British firm, taken over by Philips a long time ago - 1927.

When I was a post-doc at Southampton - 1971 to 1973 - Mullard had a semiconductor plant just down the road.

They made those weird looking transistors in a long cylindrical domed glass package coated in black paint, did they not? If you scraped the paint off you got a photo transistor IIRC.

Red dot = collector.

.... Phil

Also film has improved out of all recognition. By putting formate ions in the emulsion, reciprocity failure has been eliminated, and in fact one photon can expose _two_ grains of halide. See J. Belloni et al., Nature V. 402, p. 865 (Dec. 1999). Dunno if you can buy it like that, but there's no reason you couldn't.

Cheers

Phil Hobbs

Yep ;-) ...Jim Thompson

I was going to say OC71 and OCP71

I thought most OC71s were potted in white gunk whereas a true OCP71 was clear?

Yes, it was. The same for OC70's. The gunk was translucent, so the phototransistors still worked.

I made a rough telephone (around 1960) using an incadescent lamp as a transmitter and a scraped OC70 as the receiver. The lamp did modulate when there was audio in series of the DC feed. I used car headlight reflectors to increase the communication distance to around 10 m.

Wow. If anyone else had told me that, I'd have scoffed at them.

Not calling you a liar by any means, but I'm finding it hard to see how such a lamp could respond fast enough to the frequencies of the human voice - at *any* distance!

Mild misstatement on my part. There's a multiplication gain of 2, but only one grain per photon.

CHeers

Phil Hobbs