why are old school amps worth so much?

People have used series resistors in the speaker output to (sort of) simulate a tube-like sound. All it's doing is letting the impedance curve of the speaker add a bit of 'character' to the sound. It may or may not make it sound better ('better' being completely s
with resistance added voltage amp becomes current drive and distortion gets down.

esa merilainen describes this as simple resistor method:

https://www.current-drive.info/9


The Series Resistor Method​

The simplest means to establish a transconductor in practice is to connect a series resistor at the output of a coventional voltage amplifier. The higher the resistance with respect to the speaker impedance, the purer the amplifier operates in the current-drive mode.

i started a thread about converting amps by current feedback to current drive

https://www.diyaudio.com/community/...-to-current-drive.389985/page-11#post-7436360
 
with resistance added voltage amp becomes current drive and distortion gets down
That refers to a system where the feedback is moved outside of the amp. The resistor I referred to was simply a series resistor. The resistor allowed the changing impedance (across the spectrum) of the speaker to influence the sound due to a changing frequency response of the system as the speaker impedance changed. At points where the impedance increases, the speaker sees more voltage and the output increases. The converse is true where the impedance drops. The resultant sound could be better or worse depending on the impedance curve and the listener's preferences.
 
That refers to a system where the feedback is moved outside of the amp. The resistor I referred to was simply a series resistor. The resistor allowed the changing impedance (across the spectrum) of the speaker to influence the sound due to a changing frequency response of the system as the speaker impedance changed. At points where the impedance increases, the speaker sees more voltage and the output increases. The converse is true where the impedance drops. The resultant sound could be better or worse depending on the impedance curve and the listener's preferences.
This is exactly correct. The interesting 'Psyco-acoustic-effect' is that when some listeners hear the difference between
a transistor amp. (with low O/P impedance) and a tube amp. (with high O/P impedance) they think that because they can hear
a difference , the tube amp. must be better (due to 'rumor & folk law') when in fact they are starting to hear the speakers impedance curve.
This can lead many people astray with false belief.
PS.
It is true that some people may actually prefer the sound of an impedance curve rather than 'flat accurate sound'.
( just insert a resistor and see what think )
 
hey,

That's cool thanks for the literature. Man, we musta sold and installed between the 5 install shops at least hundreds of those P100 amplifiers.

The thing is built right. I remember Alpine came out with an amp, was it a 3002?? 3008? Can't remember the model, but I sure as hell remember opening those up for cutting traces in several places to reroute and isolate signal and power gnd's. Then we'd jump them with a 100 ohm resistor, aka fosgate to get rid of the ground noise.

Then Nakamichi came to us with their ultra super dooper cassette head units and their 100 watt 2 channel "P100 killer". That damn amp had signal and frame grounds common everywhere inside. Idiots. I was just an installer but I knew not to do that. I became very unpopular with the snobs at Nakamichi when I had to spring the news on them. Their solution: plastic mounting brackets! Float the whole damn thing!

Ahhh,, those were the days.

One day Jim Tweeten, the owners son shows up in the parking lot of the install shop, and starts driving golf balls into the surrounding residential streets with what looked like a 9 iron. That made an impression on me, and anyone in his way to be sure. He pretty much lost my support at that moment.

So I eventually ended up parted with Mag hifi and went to the competition to open a radio/stereo/video repair shop that a few years later I bought for $6k and opened my own shop.. ran that 1988 to 2002 or thereabouts. I was looking back this summer and ran some stats.. we were doing 55 chassis repairs/day, over 17,000 annually. That's abuncha solder work! $987,350.00 gross. damn! missed the magic million by 13k.

I left hifi/video for food service in no small part due to ******* policies like from Sony and others, so went into food service on account their electronics gear supports a money making activity, so fixing their stuff has a lot of advantages.$$$. Been doing that since 2006. Plus they love me, from their perspective (and my co workers) I am the miracle electronics tech.

The Kenwood rep was a lot of fun, he'd bring the new line of amplifiers to my shop and we'd beat the hell out of them. He was tickled when I built a jig to bridge those into mono, we'd run those till they smoked. That guy knew exactly what his stuff could do (over some beers in a closed up for the night warranty station).

One time we added a second voice coil to a tweeter and used his amplfiers to make a hi freq servo/amp/speaker. That was fun.

Another time A guy who designed speakers for Speaker Lab was trying to make digital audio recordings of his guitar playing on his HK VCR and his guitar amp delivered 120vac along the VCR signal ground. Blew snot out of it. He had a lot invested so I went through the whole thing and fixed it. I shouldn't have, it was a LOT of work, but to his credit in return he designed and built never sold speaker lab.1 bench reference speaker pairs for my shop benches, those were sweet! Still have one pair.



Sorry to blather on.. I guess I must feel a bit guilty for bailing out of an industry that treated me pretty good overall and I enjoyed it a lot.

Sooo... who has that P100 skin? (schematic)..

Hmmmmmm?

;^)


jg
What was the name of your repair shop? Long time Seattle resident here.