yes, Z220's were high end
& rugged & nearly perfect SQ.
However something a lot of folks ignore the type of (cheaper) internal op amps (the small amplifiers in an amplifier circuit).
As I learned from a friend, by rebuilding the power supply to be bullet proof, then replacing these op amps with very low distortion Burr Brown op amps, the SQ quality of these older become untouchable.
Current price for the Z220's (when you find them ) $200 to $250!.
I paid $832 for my first one in 1988.
Rated conservatively at a TRUE 115 x 4 @ 0.02 THD from 20 to 20KHz these amps have specs which are hard to touch; as so many amps are now just rated at 1000 hz.
However by manipulation of the internals you make an amp almost untouchable in the higher end stuff today, for a price most folks probably wouldn't call high end ($200).
Now consider 115 x 4 at 20 to 20000 at 0.002%THD...Burr Brown mod creates unworldly SQ specs..on the cheap.
I buy Z220's every time I see one, I'm about to buy my fifth.
While its true these might not be digital output, or balanced, and you still have to deal with RCA signals and ground loops; they make an SQ system that is out of this world.
BTW, you can also add optical inputs with mods to help isolate ground loop issues.
& rugged & nearly perfect SQ.
However something a lot of folks ignore the type of (cheaper) internal op amps (the small amplifiers in an amplifier circuit).
As I learned from a friend, by rebuilding the power supply to be bullet proof, then replacing these op amps with very low distortion Burr Brown op amps, the SQ quality of these older become untouchable.
Current price for the Z220's (when you find them ) $200 to $250!.
I paid $832 for my first one in 1988.
Rated conservatively at a TRUE 115 x 4 @ 0.02 THD from 20 to 20KHz these amps have specs which are hard to touch; as so many amps are now just rated at 1000 hz.
However by manipulation of the internals you make an amp almost untouchable in the higher end stuff today, for a price most folks probably wouldn't call high end ($200).
Now consider 115 x 4 at 20 to 20000 at 0.002%THD...Burr Brown mod creates unworldly SQ specs..on the cheap.
I buy Z220's every time I see one, I'm about to buy my fifth.
While its true these might not be digital output, or balanced, and you still have to deal with RCA signals and ground loops; they make an SQ system that is out of this world.
BTW, you can also add optical inputs with mods to help isolate ground loop issues.
Re: yes, Z220's were high end
For some reason, I remember them having balanced inputs. I'll have to take one apart and check that out.
Agreed on the SQ comment, as Zapco had already set the bar with their previous 151/200 models. The Z220 was designed as the replacement, although it was sold alongside the 200A for a year or two.
I think the 151/200 amp module was entirely discrete, no op amps.
lgvenable, welcome to the forum!
My bet is TL072 or a derivative.
lgvenable said:
For some reason, I remember them having balanced inputs. I'll have to take one apart and check that out.
Agreed on the SQ comment, as Zapco had already set the bar with their previous 151/200 models. The Z220 was designed as the replacement, although it was sold alongside the 200A for a year or two.
I think the 151/200 amp module was entirely discrete, no op amps.
lgvenable, welcome to the forum!
ppia600 said:
My bet is TL072 or a derivative.
thanks for the welcome
I fear you guys are far better that this than me, I just have great friends who are ee's, along with a ee brother. I got my degree in Chemistry, so I know a WHOLE lot more chemistry than electronics.
However, as we all do, forums like this are a great learning experience
Thats the great things about forums, they empower the end users by having all sorts of folks with diverse background work on isues (particular to each forum).
At any rate, perhaps they'll stop moderating me soon.
I certainly learned very quickly when it came to reworking the op amps, as I was shocked at the ease in replacing the op amps with Burr Brown's and suddenly your amps are sooooo much better.
Thanks again,
Larry
SQ to the Max.
I fear you guys are far better that this than me, I just have great friends who are ee's, along with a ee brother. I got my degree in Chemistry, so I know a WHOLE lot more chemistry than electronics.
However, as we all do, forums like this are a great learning experience
Thats the great things about forums, they empower the end users by having all sorts of folks with diverse background work on isues (particular to each forum).
At any rate, perhaps they'll stop moderating me soon.
I certainly learned very quickly when it came to reworking the op amps, as I was shocked at the ease in replacing the op amps with Burr Brown's and suddenly your amps are sooooo much better.
Thanks again,
Larry
SQ to the Max.
They are easy to put in, and I have not done any, just asking why people say that they don't really do much for the actual sound? Are those people...incorrect?
I would try to test it, but my drive times are pretty short lately when I listen in the car. I know for sure with old analog EQ/crossovers there is quite a difference in sound quality (though mostly at higher volumes), but I really don't know why aside from the quality of the particular unit. Now I have a DSP HU that is not that fantastic but not sorted it out fully.
I would try to test it, but my drive times are pretty short lately when I listen in the car. I know for sure with old analog EQ/crossovers there is quite a difference in sound quality (though mostly at higher volumes), but I really don't know why aside from the quality of the particular unit. Now I have a DSP HU that is not that fantastic but not sorted it out fully.
Old School Alpine Amps
Here's the original catalogue from when the 3558 was their flagship:
http://s432.photobucket.com/albums/qq43/Jamesbealca/
I'll throw in photos of my MRV-F540's (one still brand new and never been used).
Here's the original catalogue from when the 3558 was their flagship:
http://s432.photobucket.com/albums/qq43/Jamesbealca/
I'll throw in photos of my MRV-F540's (one still brand new and never been used).
tsmith1315 said:
That's because all amplifiers sound the same, operational amplifiers included.
Larry, whatcha gonna do with all those Zapcos?
Seriously though, I would change all eight of them if it would make an audible difference. Even just knowing it would decrease distortion to the extent mentioned above would be good enough...
I thought it was all amplifiers (can be EQ'ed to) sound the same, by Clark 
jol50
And op amps are amplifiers, too.
Years ago, Bob Carver issued a challenge to that effect.
He claimed that he could tweak one of his amps sound exactly like ANY amp the challenger presented, and within a fairly short time window.
As I remember, the devil was in his method of verifying success. The whole challenge was pretty much blown off as BS.
I share the skepticism on this subject, but I have to admit it is strictly prejudice and unfounded without testing. A tenfold reduction in distortion is significant.
I would expect that to be more audible in an amp that is already an excellent SQ performer, and therefore able to transfer such detail.
Furthermore, I would expect that the amplifier needs to be connected to a speaker system capable of exposing said detail, and auditioned by a listener with similar capabilities and the desire to do so.
Despite my skepticism, I would be more likely to spend a few extra bucks upgrading op amps than upgrading cables. It could be an inexpensive upgrade to do one amplifier and compare. ppia600 you haven't seared those polks have you? hint hint.
I don't have equipment to measure such changes, has anyone here ever tried it?
speaker:
Wow, thanks for the memory trip. You're right, the AD712 was the in-thing for chic upgraders. That was about the same time the Alpine 7909 dawned on the world...
And op amps are amplifiers, too.
Years ago, Bob Carver issued a challenge to that effect.
He claimed that he could tweak one of his amps sound exactly like ANY amp the challenger presented, and within a fairly short time window.
As I remember, the devil was in his method of verifying success. The whole challenge was pretty much blown off as BS.
I share the skepticism on this subject, but I have to admit it is strictly prejudice and unfounded without testing. A tenfold reduction in distortion is significant.
I would expect that to be more audible in an amp that is already an excellent SQ performer, and therefore able to transfer such detail.
Furthermore, I would expect that the amplifier needs to be connected to a speaker system capable of exposing said detail, and auditioned by a listener with similar capabilities and the desire to do so.
Despite my skepticism, I would be more likely to spend a few extra bucks upgrading op amps than upgrading cables. It could be an inexpensive upgrade to do one amplifier and compare. ppia600 you haven't seared those polks have you? hint hint.
I don't have equipment to measure such changes, has anyone here ever tried it?
speaker:
Wow, thanks for the memory trip. You're right, the AD712 was the in-thing for chic upgraders. That was about the same time the Alpine 7909 dawned on the world...
Zapco Heaven
Tim,
I've had an aftermarker competition system, left over from the late 80's early 90's. Around the time I got rid of the car and put the stereo in boxes, I have a low mileage 3000GTVR4 ('92) which I bought in 92. Well the factory stereo has gone south through the years, and now the volume will change intermittently high ot low for no reason.
I said "enough"! I pulled out my boxes and started using eBay to update and get more Z220's. I'm doing 4 Z220's with #5 as a backup. I'm running Boston 6.5 pros and 6.53 pros (front/back), and two 10" 10.5LF subs. Each sub to be drivewn by a mono Z220. Each component set to be driven at 110 to 115 watts/channel by a Z220.
This is much like my system of old. All the sound conditioning is Audiocontrol (4XS and an 4 channel EQQ). I'll proabably end up adding an epicenter, since the I got the Pioneer ipod adapter to g with athe Pioneer HU as well.
I saw the comment, "why would someone want to replace op-amps since the current ones are so good. I disagree. While the op amps in some of the older very good amps (Z220) do work well at 0.02THD. However, if you look at higher end audiophile equipment, amps and components (like my Denon stuff) with Burr Browns, have a very heavy price tag.
They sound great, but you pay for it. As an idea, Burr Browns , which sell for 2.50 to 7 to 8 USD each, along with the proper chip carrier (4/package at $6 on ebay), has you putting about 40.00 into modding the amps with new op amps. Those "very good op amps" cost way way less tha 1 buck each; and in some casses, only pennies each.
Burr Browns are simply more musical, and give better clarity and imaging. If you're into SQ, they will help clean up the signal, really improve the sound.
And considering that we all put acousti-mat type asphaltic lining on the floors of our cars at what cost? My is running 300.00!
While I'll do that to gain what 6 to 12 dB in the car less noise, I'm more than willing to do a $40 or $50 mod to make sure I've got something truly unique..that NO ONE sells ..while decreasing distortion by a factor of 10.
And these are mods that go right to the bottom line in an SQ system, for virtually no money, just some chip carriers, the Burr Browns and 20 minutes per amp. You put in the chip carriers, then if you don't like what you did, you can put the original op ap back in.
At least me, when I'll spend 300 on the floor, $10 extra per amp is a no-brainer.
Larry
Tim,
I've had an aftermarker competition system, left over from the late 80's early 90's. Around the time I got rid of the car and put the stereo in boxes, I have a low mileage 3000GTVR4 ('92) which I bought in 92. Well the factory stereo has gone south through the years, and now the volume will change intermittently high ot low for no reason.
I said "enough"! I pulled out my boxes and started using eBay to update and get more Z220's. I'm doing 4 Z220's with #5 as a backup. I'm running Boston 6.5 pros and 6.53 pros (front/back), and two 10" 10.5LF subs. Each sub to be drivewn by a mono Z220. Each component set to be driven at 110 to 115 watts/channel by a Z220.
This is much like my system of old. All the sound conditioning is Audiocontrol (4XS and an 4 channel EQQ). I'll proabably end up adding an epicenter, since the I got the Pioneer ipod adapter to g with athe Pioneer HU as well.
I saw the comment, "why would someone want to replace op-amps since the current ones are so good. I disagree. While the op amps in some of the older very good amps (Z220) do work well at 0.02THD. However, if you look at higher end audiophile equipment, amps and components (like my Denon stuff) with Burr Browns, have a very heavy price tag.
They sound great, but you pay for it. As an idea, Burr Browns , which sell for 2.50 to 7 to 8 USD each, along with the proper chip carrier (4/package at $6 on ebay), has you putting about 40.00 into modding the amps with new op amps. Those "very good op amps" cost way way less tha 1 buck each; and in some casses, only pennies each.
Burr Browns are simply more musical, and give better clarity and imaging. If you're into SQ, they will help clean up the signal, really improve the sound.
And considering that we all put acousti-mat type asphaltic lining on the floors of our cars at what cost? My is running 300.00!
While I'll do that to gain what 6 to 12 dB in the car less noise, I'm more than willing to do a $40 or $50 mod to make sure I've got something truly unique..that NO ONE sells ..while decreasing distortion by a factor of 10.
And these are mods that go right to the bottom line in an SQ system, for virtually no money, just some chip carriers, the Burr Browns and 20 minutes per amp. You put in the chip carriers, then if you don't like what you did, you can put the original op ap back in.
At least me, when I'll spend 300 on the floor, $10 extra per amp is a no-brainer.
Larry
tsmith1315 said:
IIRC, the AD712 was one of the first "super" opamps. Seems like somewhere I've got a sleeve of them kicking around too.
You mention the distortion drop. I witnessed an AD712 swap, before & after, on an older amp that used an AN6556 in the front-end. It has been ~15 years but it was something along the lines of from '0.01' to '0.001'. I may be off on the exact number but the engineer who did the measurements was astounded by the change from only the opamp. Measurements were conducted on an Audio Precision. From a totally subjective standpoint, the AD712 made the amp seem quieter too whereas there had been some background hiss before the swap. To be fair, this could only be heard if you put your ear up to the tweeters but it was definitely gone or below my hearing threshold after the change was made.
I just went and looked up the spec's and the immediate difference is slew rate from 2v (AN6556) to 16v for the AD712. The distortion rate is unpublished for the AN6556 but for the AD712 is is listed as 0.0008%. It would be very interesting to find what the AN6556 actually does and if that was the sole reason for the distortion decrease on the amp above. I will temper my enthusiasm in that the above was not a test. We did not have another identical amplifier to measure against to know that the AD6556 was in-spec. Conceivably, it wasn't and changing in the AD712 only got it back somewhere near original baseline. But, I don't really believe that. Too many times over the years and from too many people I've heard about sound quality changes wrought from opamp swaps. Heck, even Mr. Opamp, Walter Jung has sung their praises in this regard!
In any case most of the 80's & 90's vintage amps used DIP package through-hole opamps in the front-end. Install a set of sockets and you can put in anything compatible from 741's to OPA2132's! (OK, maybe not 741's!) Even if the only audible improvement is a better signal to noise ratio, the cost of upgraded opamps would seem to justify that.
The best op-amp upgrade is NO op-amps at all. Its call a front end bypass.
With today's high drive levels from HU's The input op-amp buffer stage is not needed on most car amps. < especially Vintage amps where 2 volts drove the amp to full power.
Also when you bypass the two or three op-amps stages in front of the average amp you also get to bypass one or more of the very cheap electrolytic caps used to block DC that are directly in the path of the music.
Also try installing a nice Film type cap on the remaining Electrolytic's located just behind the RCAs and just before the Main diff pair of each channel. 100nf or there about should do nicely.
Oh and this cap bypass thing is not my idea, I am plagiarizing a small company by the name of Threshold, and several other sources including the Agilent facility where Mr Linkwitz of Linkwitz- Riley fame came from. And to be honest even my PG Ti passive crossovers use this exact same thing to make compensations for large electrolytic caps used the the Ti crossovers for the Morel driver sets they had a few years back.
Word is this mod cleans up the high end without going to drastic moves such as Op-amp exchanges.
Also you guys might want to look into the current draw those high end op-amps have. As I have been seeing over the years people seem to overlook the basics like how much current that hot rod op-amp draws and how much current does my amp and its limited design have to give to the upgrade ???
Just dropping in op-amps is not as simple as some of you have described. Yes the physical work is simple enough. But there are a bunch of things that can go wrong.
Just something to think about, and I would keep a scope handy for and look for trouble when you do the deed of op-amp swaps... Good luck to all, and I hope you find some of my dribble interesting....
With today's high drive levels from HU's The input op-amp buffer stage is not needed on most car amps. < especially Vintage amps where 2 volts drove the amp to full power.
Also when you bypass the two or three op-amps stages in front of the average amp you also get to bypass one or more of the very cheap electrolytic caps used to block DC that are directly in the path of the music.
Also try installing a nice Film type cap on the remaining Electrolytic's located just behind the RCAs and just before the Main diff pair of each channel. 100nf or there about should do nicely.
Oh and this cap bypass thing is not my idea, I am plagiarizing a small company by the name of Threshold, and several other sources including the Agilent facility where Mr Linkwitz of Linkwitz- Riley fame came from. And to be honest even my PG Ti passive crossovers use this exact same thing to make compensations for large electrolytic caps used the the Ti crossovers for the Morel driver sets they had a few years back.
Word is this mod cleans up the high end without going to drastic moves such as Op-amp exchanges.
Also you guys might want to look into the current draw those high end op-amps have. As I have been seeing over the years people seem to overlook the basics like how much current that hot rod op-amp draws and how much current does my amp and its limited design have to give to the upgrade ???
Just dropping in op-amps is not as simple as some of you have described. Yes the physical work is simple enough. But there are a bunch of things that can go wrong.
Just something to think about, and I would keep a scope handy for and look for trouble when you do the deed of op-amp swaps... Good luck to all, and I hope you find some of my dribble interesting....
ppia600 said:So no other mods would be necessary, as long as the pinout is the same? Seems too easy. Is there a way to make sure they are genuine burr brown? I noticed a seller talking about restamps that aren't.
if the circuit was designed using a low bandwidth op amp and the layout wasn't done that well (the low bandwidth keeps everything stable) you will have problems with faster op amps. usually, an easy fix is adding bypass caps right at the op amp pins...
Good point djQUAN. Just goes to demonstrate op amp upgrades aren't always plug and play, you gotta do your homework first.
speaker:
I assume noise to be included in distortion measurements unless otherwise indicated. That could help explain the significant decrease in distortion.
ppia600:
Well, not exactly. You want to be sure the part in consideration is drop-in compatible with the one being replaced. Manufacturers will often mention the product as being a drop-in upgrade for standard models like the jfet tl072/074.
If not, look to be sure they don't require external compensation or critical layout considerations, etc.
Read the datasheet carefully and study the circuit/layout where it will be going.
Don't limit yourself to BB, as there are other good products out there like the Analog Devices that speaker mentioned. Other forums here will yield good advice and arguments about compatibility and results.
lgvenable:
Keep us posted on your install progress, maybe with pics?
speaker:
I assume noise to be included in distortion measurements unless otherwise indicated. That could help explain the significant decrease in distortion.
ppia600:
Well, not exactly. You want to be sure the part in consideration is drop-in compatible with the one being replaced. Manufacturers will often mention the product as being a drop-in upgrade for standard models like the jfet tl072/074.
If not, look to be sure they don't require external compensation or critical layout considerations, etc.
Read the datasheet carefully and study the circuit/layout where it will be going.
Don't limit yourself to BB, as there are other good products out there like the Analog Devices that speaker mentioned. Other forums here will yield good advice and arguments about compatibility and results.
lgvenable:
Keep us posted on your install progress, maybe with pics?
1moreamp said:
I thought the purpose of the op amps was for ground loop elimination? Because of the seperation of the optical/led transmitter on one side and the reciever on the other side. If that isn't the case, I'd be interested in bypassing mine, as my deck can supposedly drive a 100ohm impedance at 5Vrms. Is there some thread here I can find more out about doing this, instead of muddying this one?