Re: Re: My CD63 Transformation
I was just looking at the schematic and it appears as if Q852 pulls the 3.6V secondary down to the required -19.5V for the VF display (VF1, VF2). Q853 turns Q852 on, but if I just tie the base of Q852 to +5V via R854, I should be fine just re-installing Q852, R852, R853, R854, and D853.
As far as the op-amp tied directly to the output, this is not the best idea! Yes, I did it, but it is only temporary. I plan to add short circuit protection, but I need to match the resistor with the max op-amp output current so not to damage the op-amp. The problem is that the OPA627, AD8620 and LM4562 all have different current ratings. According to the datasheets, I have calculated the following serial resistances:
OPA627: 266 Ohm
AD8620: 400 Ohm
LM4562: 521 Ohm
While so far I am able to drive the 50 Ohm load of my cable with the LM4562, I will probably overheat it and degrade performance in the long run. In true purist theory, I should buy 2 Caddock's of each of the above values and swap them in with their respective op-amp in order to do a true comparison between op-amps. But, yikes ... more $$$! Hence the temp solution to run direct.
First will be the clock upgrade and precision comps on the filter to get the most accurate signal to the op-amp that I can with my planned modifications. Then I can due a more accurate comparison.
Will keep y'all posted!
rowemeister said:
Hi and welcome
I noticed in your pics you removed the transistor Q853 and this is needed for the display
Also a clock improves detail and timing
Brent
I was just looking at the schematic and it appears as if Q852 pulls the 3.6V secondary down to the required -19.5V for the VF display (VF1, VF2). Q853 turns Q852 on, but if I just tie the base of Q852 to +5V via R854, I should be fine just re-installing Q852, R852, R853, R854, and D853.
As far as the op-amp tied directly to the output, this is not the best idea! Yes, I did it, but it is only temporary. I plan to add short circuit protection, but I need to match the resistor with the max op-amp output current so not to damage the op-amp. The problem is that the OPA627, AD8620 and LM4562 all have different current ratings. According to the datasheets, I have calculated the following serial resistances:
OPA627: 266 Ohm
AD8620: 400 Ohm
LM4562: 521 Ohm
While so far I am able to drive the 50 Ohm load of my cable with the LM4562, I will probably overheat it and degrade performance in the long run. In true purist theory, I should buy 2 Caddock's of each of the above values and swap them in with their respective op-amp in order to do a true comparison between op-amps. But, yikes ... more $$$! Hence the temp solution to run direct.
First will be the clock upgrade and precision comps on the filter to get the most accurate signal to the op-amp that I can with my planned modifications. Then I can due a more accurate comparison.
Will keep y'all posted!
Re: Re: Re: Re: My CD63 Transformation
You must have a different datasheet than I do! Mine states 45mA output current and 65mA short circuit current! It may be able to meet that short circuit current for an infinite time period, but a 0 Ohm load at 12V is WAY more than the 65mA short circuit rating! In order for the op-amp to work at ideal conditions (i.e. "stated" datasheet parameters), it must work within it's as-designed output current. By increasing this current you can overheat the device which will shorten it's lifespan as well as drive it's noise figures through the roof. Take a look at the OEM configuration ... they use a 470 Ohm load on the LM2114, thus loading it at about 25mA ... which is well below the max 40mA output current it is capable of driving.
poynton said:
You must have a different datasheet than I do! Mine states 45mA output current and 65mA short circuit current! It may be able to meet that short circuit current for an infinite time period, but a 0 Ohm load at 12V is WAY more than the 65mA short circuit rating! In order for the op-amp to work at ideal conditions (i.e. "stated" datasheet parameters), it must work within it's as-designed output current. By increasing this current you can overheat the device which will shorten it's lifespan as well as drive it's noise figures through the roof. Take a look at the OEM configuration ... they use a 470 Ohm load on the LM2114, thus loading it at about 25mA ... which is well below the max 40mA output current it is capable of driving.
Hi Craig,
I think you used the 'output current capability' figure for calculating these resistances. But these values are way too high. As Andy says, nowadays almost every opamp is short-circuit proof. IF you short it, the mentioned current that runs can be endured indefinately. The output current is internally limited and thus is not 12V divided by the output resistance. The other reason for a resistor at the output could be the capacitive load of the following interlink. Some opamps don't like that.
By the way, how come your cable is a 50 ohm load??
Ray
I think you used the 'output current capability' figure for calculating these resistances. But these values are way too high. As Andy says, nowadays almost every opamp is short-circuit proof. IF you short it, the mentioned current that runs can be endured indefinately. The output current is internally limited and thus is not 12V divided by the output resistance. The other reason for a resistor at the output could be the capacitive load of the following interlink. Some opamps don't like that.
By the way, how come your cable is a 50 ohm load??
Ray
6h5c said:
Sorry ... in video world today ... 75 ohm ...
My main concern is the THD figures go up significantly when the amp is not operating under an ideal load. While it is true we need to measure the actual impedance with the amplifier connected, why not just stick a series resitor to be 100% sure we are properly loaded? Some say series resistance is bad, but when using a non-inductive resistor such as a Caddock, I don't see any negative effects. I actually use a Caddock/Black Beauty divider in my Axiom passive preamp with no ill-effects.
Yes, the amp can endure a direct short by it's internal resistance, but at what cost ... heat! At $20/pop, I'd rather spend $4 on a Caddock than reduce the life of the op-amps. Granted, how often will they ever short anyway (likely never). I guess I have been brainwashed by my company and always tend to err on the side of safety!
Re: Re: Re: Re: Re: My CD63 Transformation
Extract from the spec sheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/102945/AD/AD8620.html
Andy
craigtone said:
Extract from the spec sheet
http://pdf1.alldatasheet.com/datasheet-pdf/view/102945/AD/AD8620.html
Andy
Hi Craigtone,
I have read in the LM4562 sheets that it had shortcircuit protection, can't you drive the cable without resistor then?
Did the switch to LM4562 myself and it gave me back the bass i was missing after the removal of the HDAM, the OPA2134 was in place before but this was sounding rather thin after i got rid of the HDAM.
The LM4562 is staying in that for shure!!
It has very detailed high and mids and i'm hearing things i never
have before.
Ray,
Thanks for all your wise words and tons of ideas, i have consumed all this reading and wil try to realise all this my CD67SE.
Why havent someone thought of including the +/- 12volt raygulator and the supplycaps on the FET output print?
Mayby this is sounding better again because it can react faster when its nearby.
By the way if you have a dicrete FET outputprint laying around doing nothing, then i like to buy it from you.
Simon,
How is your external powersupply project sounding after some days of burning in?
Peter
I have read in the LM4562 sheets that it had shortcircuit protection, can't you drive the cable without resistor then?
Did the switch to LM4562 myself and it gave me back the bass i was missing after the removal of the HDAM, the OPA2134 was in place before but this was sounding rather thin after i got rid of the HDAM.
The LM4562 is staying in that for shure!!
It has very detailed high and mids and i'm hearing things i never
have before.
Ray,
Thanks for all your wise words and tons of ideas, i have consumed all this reading and wil try to realise all this my CD67SE.
Why havent someone thought of including the +/- 12volt raygulator and the supplycaps on the FET output print?
Mayby this is sounding better again because it can react faster when its nearby.
By the way if you have a dicrete FET outputprint laying around doing nothing, then i like to buy it from you.
Simon,
How is your external powersupply project sounding after some days of burning in?
Peter
Peter Venema said:
Hi Peter,
You're welcome! I don't have any PCB's laying around, I built the circuit on the player's PCB so far. Jaap developed a nice PCB for the output stage, maybe he has one to spare? His layout is freely available, and etching one is not that hard.
BUT.... i'm designing a new PCB as we speak to fit in my SA8400. I don't want to rip all the parts out of this player, in case I ever have to reverse the mod, but i'm dying to try it with the FET stage and passive filter. So I decided to make one too
. It's not going to be very different from Jaap's PCB, but MAYBE i'm going to fit part of the PSU on it if there's room.Ray
Attachments
LM4562 opamps - wow!
In the spirit of: "What do blokes do right after sex? Tell their mates!", I'm writing to say how fantastic these LM4562's are! It's less than a half hour since they got delivered, and there is no need going back to my old OP-249's for an A-B-A comparison. These things are so much more transparent and focused that my girlfriend heard the difference two floors away! Absolutely another veil lifted. Thanks for the tip guys, my girl and I really liked it!
In the spirit of: "What do blokes do right after sex? Tell their mates!", I'm writing to say how fantastic these LM4562's are! It's less than a half hour since they got delivered, and there is no need going back to my old OP-249's for an A-B-A comparison. These things are so much more transparent and focused that my girlfriend heard the difference two floors away! Absolutely another veil lifted. Thanks for the tip guys, my girl and I really liked it!
More LM4562 impressions
After some more listening I can characterise the LM4562 a little more. It sounds faster, more dynamic, and has less euphonic haze - very clear. Bass is about the same as my old OP-249's, which were good, but everything else is better. 3D imaging has taken on a whole new level of focus and precision. I now have a favorite dual opamp, with the caveat that in some applications it will reveal problems too clearly.
After some more listening I can characterise the LM4562 a little more. It sounds faster, more dynamic, and has less euphonic haze - very clear. Bass is about the same as my old OP-249's, which were good, but everything else is better. 3D imaging has taken on a whole new level of focus and precision. I now have a favorite dual opamp, with the caveat that in some applications it will reveal problems too clearly.
Peter Venema said:
Peter,
It's sounding good and I still feel it was a very worthwhile upgrade. I've been away for the weekend though so I've not had many chances to listen properly. However I'm more impressed, as we all seem to be, by the LM4562 in my preamp. It's very noticeably "nice" sounding from my pc too! Even games sound unfamiliarly good.
Simon
poynton said:Hi.
I received my second lot of LM4562 today.
Now for the mods!
Andy
Another glowing LM4562 review coming up surely. If the person responsible at National can see this thread he'll surely be congratulating himself somewhat!!!
I might get around to ordering me those DIN connectors tomorrow. Then I can get this last mod more sorted... and the next one
SimontY said:
Thanks to all who replied on this, the WAF (Wife Acceptance Factor) has skyrocketed well above the "acceptable" level
. Parts ordered from Digikey, can't wait. Yippee.She's going to build some LM317/LM337 "Raygulators" from test boards. I was going to buy some of Eddie Wang's PCB's because they look well made (still might), but she reckons a test board will do just as well and will spare the expense of US5$ a PCB ... which I can "maybe" put towards a drop-in Super-reg like Audiocoms or Tents.
I noticed Ray has the LM317-based ones in his pics, has anyone compared these to the commercial Super-regs? Are they worth the extra $$?
k.
I just replaced my CM12.1 / VAM1201 mechanism, so I have recently been fiddling with this.
This site:
http://iangclark.net/projects/CD63/CD63.html
has great instructions on removing the players tray unit. I used it.
Here's a second one with a few tips too, and good pics. http://www.diyparadise.com/cd46/cd46repair.html
The "ribbon cable" connection "Liqourice strap" thingies are not like computer connections, you have to GENTLY lift up the inner connector, then ease out the ribbon cable which is clamped between inner and outer connector.
HTH.
k.
This site:
http://iangclark.net/projects/CD63/CD63.html
has great instructions on removing the players tray unit. I used it.
Here's a second one with a few tips too, and good pics. http://www.diyparadise.com/cd46/cd46repair.html
The "ribbon cable" connection "Liqourice strap" thingies are not like computer connections, you have to GENTLY lift up the inner connector, then ease out the ribbon cable which is clamped between inner and outer connector.
HTH.
k.