John Curl's Blowtorch preamplifier part II

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Scott,

I don't know why you keep supporting the microdiode bit. The usual explanation for tapping a bad microphone is that there is a cold solder joint or oxidized connection that is temporarily restored by passing a higher voltage or current through it. If you compare the voltage generated by tapping to normal use it is easily 80 dB greater.

I keep telling you there ain't no microdiodes. :)

A much better explanation is that evil spirits are resisting the sound and banging them on their heads gets them to leave.
 
Scott,

I don't know why you keep supporting the microdiode bit. The usual explanation for tapping a bad microphone is that there is a cold solder joint or oxidized connection that is temporarily restored by passing a higher voltage or current through it.

Have a sense of humor, the only controversy was that you are simply making/braking a true Ohmic connection there are no 10 or 100mV gaps jumped.
 
One of my Aussie mates was an old friend of T.E. and it came up in conversation because one of our well off colleagues had him play a private concert in his basement theater (I wasn't invited).

Well you missed something special, TE has to be experienced live.

A good friend (RIP) was his sound engineer for 18 months or so. My friend
said of Tommy, he does two types of gigs, really really good ones and
incredible ones... and this guy was a perfectionist.

Over here, when I was young we were spoilt for music. You could catch Tommy, Phil and Bucky (Banjo player) in Goldrush at local pub. The
quality of musicianship was incredible.

YouTube

That's Tommy's brother Phil on electric.

T
 
John, I'm turning 68 in a couple of weeks and there are just too many things going on with my family to ever get to the PA projects sitting on my bench. The Parasound amp that I found here used was a big 6 channel home theater thing that I don't need. I was thinking of maybe a used A23, is this a decent implementation of your work?
 
Yes Scott, an A23 should work out OK. I normally use its predecessor, the HCA1000 that I have used for the last 25 years or so. In fact, I thought that it went out just today after all these years, but fortunately, I only accidently turned on the larger (reference) power amp underneath it, that overheated the 1000 after awhile, but I was thinking that I would have to replace it with an A23. It drives Met7's very well, but watch out for the bias. It is relatively easy to adjust, but often they 'underbias' at the factory. 15-30mV across one emitter resistor is important to keep the Xover distortion to a minimum. It is a simple pot adjust.
 
Here are some schematics for the Parasound A23. It is the least expensive amp that I have designed at the moment.
 

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  • A23-AMP2 - 4190A main board.pdf
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