Inputs shorted when not in use on a preamp??

[jbeckva]

Look at this guys... See the grounds connected to the various inputs when not in use? Is that a normal(safe) way of doing it???

 

[Gepetto]

Look at this guys... See the grounds connected to the various inputs when not in use? Is that a normal(safe) way of doing it???

View attachment 10533

unusual Jer and not one I would recommend. Likely wanted a method to reduce crosstalk from the unused inputs

 

[jbeckva]

I have to say the schematic's hosed up somehow in that respect.. let me expand it a little to show something else here.



Look at the LED indicators. Now look again at the switches. Are you scratching your head like me??

FWIW.. this is supposedly for the Harman Kardon Citation 21, for which I just sniped off of ebay. From what I (sort of) can tell, if the tone control defeat is "on", then basically the signal is "straight thru"... with just a 10uF cap in the entire path. Couldn't resist, but hmmm.. this diagram above makes NO sense to me at the moment....

 

[jbeckva]

Also to add.. the voltage rail that is tying all of the LED cathodes together is -24 volts, so at least that would make sense if ground was applied as part of the switch.. but HOW do you get ground to those LED's the way it's being depicted??

 

[Gepetto]

Also to add.. the voltage rail that is tying all of the LED cathodes together is -24 volts, so at least that would make sense if ground was applied as part of the switch.. but HOW do you get ground to those LED's the way it's being depicted??

The seller probably has the ECO supplements for sale in a different auction Jer.

 

[jbeckva]

The seller probably has the ECO supplements for sale in a different auction Jer.

Doubt the seller would have 'em, but yeah... has to be a screwup on the diagram because it wouldn't even light the LED's if it was actually wired that way..

In looking closer tho, I do see a full section of amplification that all signal has to go through. Follow the heavy lines from left to right. I'm just thinking that the discretes can maybe benefit from a good search for "modern" replacements, with the goal being making it sound better and with a lower noise floor. There are a lot of the Q's below not easily found anymore.

That and a few caps that we can replace with the "good stuff"... what do you think, Joe?

 

[Gepetto]

Doubt the seller would have 'em, but yeah... has to be a screwup on the diagram because it wouldn't even light the LED's if it was actually wired that way..

In looking closer tho, I do see a full section of amplification that all signal has to go through. Follow the heavy lines from left to right. I'm just thinking that the discretes can maybe benefit from a good search for "modern" replacements, with the goal being making it sound better and with a lower noise floor. There are a lot of the Q's below not easily found anymore.

That and a few caps that we can replace with the "good stuff"... what do you think, Joe?

View attachment 10535

You are looking at the Japanese transistor plague Jer. Almost entirely died off by now but left a fretful legacy behind of devices that are no longer available and difficult if not impossible to find specs for. The manufacturers also used so many different types in just about every design for no good reason.

Unless something is broken in my Yamaha gear, I leave it alone for the very reason above.

 

[jbeckva]

You are looking at the Japanese transistor plague Jer. Almost entirely died off by now but left a fretful legacy behind of devices that are no longer available and difficult if not impossible to find specs for. The manufacturers also used so many different types in just about every design for no good reason.

Unless something is broken in my Yamaha gear, I leave it alone for the very reason above.

Starting with the final outputs on the right, so far I have been able to find data sheets. The big concern is how these are configured for ECB instead of CBE (yeah I can twist 'em around.. hehe.. been there/done that). What I'm wondering tho is in shopping around for "better" replacements, what specs should I "exceed" in order to realize a better noise figure?

Or.. might just recap... that to me seems pretty easy as I see 4 per channel to effect the biggest bang, at least with the tone controls on bypass and not paying attention to the phono amps (that can come "later")...

 

[laatsch55]

What is it??