ppia600 said:
You're describing an optocoupler or optoisolator. Totally different component.
An operational amplifier can be configured to do a lot of things, and one of them is to fake a balanced input by referencing the signal ground to the inverting input and a coupling capacitor to signal ground. The opamp's huge input impedance sees the reference to signal ground, but the headunit's much lower output impedance can't tell it's there, thus breaking a potential ground loop. Most manufacturers to this day don't implement this; however, Pioneer has done it for 20 years.
Just bypass all that high gain crossover junk and stick the signal right into the non-inverting side of the differential pair through a capacitor. You'll want to properly terminate the input with an RC filter to keep RFI junk out of the amp. It's one resistor to signal ground after the coupling capacitor. Most amps already have this "front end" in place, just remove the Opamp that drives the amplifier-proper. However, you must be careful because some power amplifiers use an opamp as its front end/feedback device rather than a discrete solution. Don't remove that one....Heh. Anyway, I'm simplifying things a great deal, but for experimentation this will work.
ppia600 said:
Typically in 95% of all car amps the first Op-amp is nothing but a buffer input stage to limit loading on any signal source, and to compensate for the large wet cap inline that also blocks any DC component being sent out by your HU or other devices in between.
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A secondary use would be as a gain control also by either a simple voltage divider gain pot inline with the signal < Like PPI > or with a gain pot in the feedback loop to control input level gain via feedback and thusly overall gain of the stage < like PG >.
Any second or third op-amp stages are usually crossover or bass and treble boost gain stages, varying with control concept complexity, i.e. the more bells and whistles the more complex and numerous the use of op-amps.
Then there is the output buffer stage usually on more expensive models that has a set finite given gain so the signal will now be capable of driving the main amp stage to full power with respect to the gain setpoint and the drive signal from the other signal sources connected to the amp.
Loading filter circuits can cause all kinds or issues on how a filter actually performs hence the final output buffer in front of the main amp input.
Now as you were thinking Yes there are isolated input designs out there, Like Rockford Fosgate with there TOPAZ input circuitry that uses op-amps and supply decoupling to isolate the RCAs from any ground loop issues inside the main amp.
Or like my Adcom and PG ZPA amps that have true balanced line inputs. Neither of which use op-amps for there Balanced input at the amp. Everything was done discrete meaning no IC's or Op-amps.
But there were many others that did use op-amps configured into a balanced line configuration like some lower line PG and all ZAPCO that made many a happy customer with there designs that relieved the average car audio buff from noise and ground loop headaches galore.
There are also custom balanced line driver and receiver IC's out there on the market as off the shelf devices so the entire circuitry does not have to be designed as it requires very precise resistors and component layout for best results.
And yes PG, old OPTI Lanzar and ZAPCO and others all used optical feedback devices to send audio side level and signal feedback to the 12 volt side in a honest attempt to prevent ground loop issues while giving reasonable signal feedback for the PWM control circuitry so the Power supply could perform its design task as proficiently as possible < i.e. good power regulation and control with safety feedback for overload shutdown protection including thermal info in some cases.
And yes Pioneer has always used a op-amp noise canceling front-end as did Old Kenwood like in the KAC- series I still own a mint KAC-1020 that uses obsolete KKM-60 < op-amp based > balanced type input circuitry on a ceramic SIP package. And yes all these inputs suffered failures also while doing there designed job of noise cancellation and ground loop isolation. I can't even tell you how many dead Pioneers were nothing more then a defective input and old Kenwood also. I do remember stocking KKM-60 chips by the dozen though he he he... Balanced line setups do fail, but then so do other less acceptable designs also...
Again I hope you find my dribble worthwhile or at least entertaining...
ppia600 said:
It depends on the design. While I have absolutely no objective data to back this up, I have found (with my ears) that amplifiers that have a regulated power supply dedicated to the preamp stage, another to the VA stage and a completely separate output stage supply (regulated or unregulated), the difference in fidelity is striking compared to designs with a voltage divider or zener regulator in those places.
Just my two cents. I don't hand them out too often.
Re: Zapco Heaven
The upgrades can help make a poorly constructed front end sound a little better, but they cannot magically correct other distortion mechanisms in the amplifier. Many car amplifiers have some pretty horrid PSRR numbers directly related to their handling of power supply distribution. Those Korean amps don't benefit. I could name names, but I'd really upset a lot of people that import and distribute their own brands from Korea.
lgvenable said:
The upgrades can help make a poorly constructed front end sound a little better, but they cannot magically correct other distortion mechanisms in the amplifier. Many car amplifiers have some pretty horrid PSRR numbers directly related to their handling of power supply distribution. Those Korean amps don't benefit. I could name names, but I'd really upset a lot of people that import and distribute their own brands from Korea.
Eva said:
1moreamp's reference to damaged inputs was segregated to one particular brand of amplifier. I remember these well, and it really had nothing to do with the input stage failing due to an overdriven input, but rather a secondary failure because of a poor power input ground connection. It was just a design flaw....
That, and their emitter resistor cold solder joints.
Eva said:
Hi Eva,
I own ZPA's and Adcom's with balanced input and can't ever recall seeing a failure of these more dedicated brand names. The specific Pioneer and Kenwood amps were Japanese in origin back then, and I feel that they may have been budget constrained with there design, and implementation hence all the failure's I repaired over the years.
Both Kenwood and Pioneer had very good reputations back then and now. But when you see the same failures time and again as many as I did on these two specific brands, well something is amiss that's for sure.
Plus I have seen some the oddest things done to car amps over the years. Some of which will leave you shaking your head in disbelief and bewilderment.
Hope this is more clearly stated. and Thank you EnvisionAudio for your clarification of the failures. My Best to all.
old school kenwood
My very first kenwood amp from 1986 KAC-9020 still rocks and outlasted all my others. I still have my pull-out kenwood am-fm cassette CD changer controller deck, plus kenwood graphic EQ crossover 9041 with memory, kenwood CD changer, plus alpine 3522 amplifier.
I have kept everything sealed in storage tote. I also have carry tote for radio made out of scuba diving material mint condition. my deck has been stored in it for years.
Everything except alpine amp is original din cable from kenwood. I've considered selling it, but rather sell it as a system due to the din cable issue. what would system like this go for? The only thing missing is the manuals.
I also have alpine 8125 alarm, 8316 interface, and alpine phone, alarm is missing pager. Plus alpine keypad.
My very first kenwood amp from 1986 KAC-9020 still rocks and outlasted all my others. I still have my pull-out kenwood am-fm cassette CD changer controller deck, plus kenwood graphic EQ crossover 9041 with memory, kenwood CD changer, plus alpine 3522 amplifier.
I have kept everything sealed in storage tote. I also have carry tote for radio made out of scuba diving material mint condition. my deck has been stored in it for years.
Everything except alpine amp is original din cable from kenwood. I've considered selling it, but rather sell it as a system due to the din cable issue. what would system like this go for? The only thing missing is the manuals.
I also have alpine 8125 alarm, 8316 interface, and alpine phone, alarm is missing pager. Plus alpine keypad.
my 2 cents
Well after 17 pages I thought I would share some of my favorites.
Big fan of the Autotek BTS and HiFonics....Zed of course.
Dig the old Orions too....some of the best looking amps IMO....especially the moon and star amps....
Here's a small bit of my collection.....oh...really like the SQ of the older Denon amps too.....
Well after 17 pages I thought I would share some of my favorites.
Big fan of the Autotek BTS and HiFonics....Zed of course.
Dig the old Orions too....some of the best looking amps IMO....especially the moon and star amps....
Here's a small bit of my collection.....oh...really like the SQ of the older Denon amps too.....
An externally hosted image should be here but it was not working when we last tested it.
Nahh....the shelf is still straight.....no fish eye...just a "cheap" camera.....
Yeah I dig Zapco too.....but never did get into them personally...Installed quite a few though. I always wanted the "seperates".
I started my addiction with some old Autotek BTS amps....and have been collecting ever since. I dabbled in Orions when I came across a deal I couldnt pass up.....ran 2 250hccas.....and promptly learned the reason for upgraded charging systems....lol.
One of these days I'll get all my toys in one shot.....for that I MIGHT need a fisheye for.....wish i never sold that old canon 17mm......beautiful lense(and more expensive than that 2100 to boot!!!)
Yeah I dig Zapco too.....but never did get into them personally...Installed quite a few though. I always wanted the "seperates".
I started my addiction with some old Autotek BTS amps....and have been collecting ever since. I dabbled in Orions when I came across a deal I couldnt pass up.....ran 2 250hccas.....and promptly learned the reason for upgraded charging systems....lol.
One of these days I'll get all my toys in one shot.....for that I MIGHT need a fisheye for.....wish i never sold that old canon 17mm......beautiful lense(and more expensive than that 2100 to boot!!!)
yep I know the feeling.
Here are the three Zapco Z220's I'm putting into my 3000GTVR4. I did this this week, by removing the upholstery on the seat back, and reinforcing the seat back with galvaneel >>> which is very easy to jig saw).
I used SS pop rivets to mount the plate, then used hot melt to attach the carpet back down. Finally I laid out the first 2 Z220's on the reinforcement on the passenger side rear seat back, and used SS rivets to attach them to the reinforced seat back. (stainless rivets are very hard to drill...and these amps would not be easy pickings for a thief.
At any rate on the drivers seat back, I bent up a galvaneel pedestal to mount the Audiocontrol 4XS (bottom), and the EQQ (top). Truly an old school setup, as these pieces were the heart of an older competition system I had built.
I have 4 Z220's, and was going to use 2 subs (BA 10.5LF), but decided to go w/just one. Next up is the custom cabling to made the shortest possible cable runs.
Any ground loop noise abatement will be mounted under the galvaneel plate by carefully cutting a space in the PUR cushion. Shouldn't miss it. In the 16 years we've owned it, someone has been in the rear seat maybe 20 times?
Here are the three Zapco Z220's I'm putting into my 3000GTVR4. I did this this week, by removing the upholstery on the seat back, and reinforcing the seat back with galvaneel >>> which is very easy to jig saw).
I used SS pop rivets to mount the plate, then used hot melt to attach the carpet back down. Finally I laid out the first 2 Z220's on the reinforcement on the passenger side rear seat back, and used SS rivets to attach them to the reinforced seat back. (stainless rivets are very hard to drill...and these amps would not be easy pickings for a thief.
At any rate on the drivers seat back, I bent up a galvaneel pedestal to mount the Audiocontrol 4XS (bottom), and the EQQ (top). Truly an old school setup, as these pieces were the heart of an older competition system I had built.
I have 4 Z220's, and was going to use 2 subs (BA 10.5LF), but decided to go w/just one. Next up is the custom cabling to made the shortest possible cable runs.
Any ground loop noise abatement will be mounted under the galvaneel plate by carefully cutting a space in the PUR cushion. Shouldn't miss it. In the 16 years we've owned it, someone has been in the rear seat maybe 20 times?
