Its a credit to you Shaun
I feel sure that the amp will pay yoy back in heaps re sound quality etc
the unit looks really great
Once again well done
regards Trev
I feel sure that the amp will pay yoy back in heaps re sound quality etc
the unit looks really great
Once again well done
regards Trev
Shawn;
What you did was just great 😉
Saving one of the best amps from old times ever made 😀
Just courious;
I have two DC300 series II (quite different from the original DC300), however as it's quite rare here in Denmark, I was thinking of making a clone using modern components....
Could this be interesting to some her at DIY ???
What you did was just great 😉
Saving one of the best amps from old times ever made 😀
Just courious;
I have two DC300 series II (quite different from the original DC300), however as it's quite rare here in Denmark, I was thinking of making a clone using modern components....
Could this be interesting to some her at DIY ???
Hi ACD,
I don't think I'd build one, but it might be just the ticket for upgrading an earlier amp with PCB problems.
I think that you have a good idea, start a thread when you are ready!
Shawn,
See what you've started now! 😉
-Chris
I don't think I'd build one, but it might be just the ticket for upgrading an earlier amp with PCB problems.
I think that you have a good idea, start a thread when you are ready!
Shawn,
See what you've started now! 😉
-Chris
anatech;
I've been thinking over this for the last 5 years, however I would like some "partisians" before making and have the pcb's made, as I have many other project going....
You know it's quite expencive to have good pcb made !!
However I'll take your advice and start a thread 😉
I've been thinking over this for the last 5 years, however I would like some "partisians" before making and have the pcb's made, as I have many other project going....
You know it's quite expencive to have good pcb made !!
However I'll take your advice and start a thread 😉
Hi ACD,
That's fair enough. You may have more donor amps than Shawn had to work with as a plus.
I think a home brew board is good enough for your project though. If you take it far enough, you may make a substantial upgrade. Retrofitting a new design then becomes very worthwhile for owners of these amps. A commercial board then becomes a reality.
-Chris
That's fair enough. You may have more donor amps than Shawn had to work with as a plus.
I think a home brew board is good enough for your project though. If you take it far enough, you may make a substantial upgrade. Retrofitting a new design then becomes very worthwhile for owners of these amps. A commercial board then becomes a reality.
-Chris
The shrill high frequency response was one thing I hated about the amp.
Shawn, you make all us diyers very proud.😀
Good sound
Thanks Fingers, Jan, Trev & Chris for the good words. The amp really sounds good and so do your comments. 🙂 I'm listening to all kinds of music on it. It all sounds good. I would like to set up a switching system to compare it to some other stuff like the big Quasi I have. Some day...
If I here Jan correctly, you are interested in semi redesign of the DC300 series amplifiers. I have thought about this very much and wanted to engage earlier in this project but the entire process is beyond my capabilities. If I had the time and brains I'd redesign the driver board for some awesome 8pin op amps and incorporate compensation into the design for fast output transistors. I'd design an entirely new PCB that incorporates current semiconductor offerings. If it worked well I would pursure good PCB layout from a professional software package and order a bunch of boards. I would allow it to fit in existing DC300 chassi mounts but open it up so DIY'ers could use the design in their own. I always liked single sided PCB's so the true hard core DIY'er can fabricate their own PCB's. That is my general opinion and I am very interested in participating if I can.
Jan, the DC300A is not so different than the DC300A II, infact they are very similar but it sounds like you know something I don't. Do you have a DC300 II schematic that is vastly different from the DC300A that resides on the Crown web site?
The original DC300 is an entirely different beast but this is not the amp I refurbished. BTW, I would love to own a DC300 original. 🙂
Cheers,
Shawn.
Thanks Fingers, Jan, Trev & Chris for the good words. The amp really sounds good and so do your comments. 🙂 I'm listening to all kinds of music on it. It all sounds good. I would like to set up a switching system to compare it to some other stuff like the big Quasi I have. Some day...
If I here Jan correctly, you are interested in semi redesign of the DC300 series amplifiers. I have thought about this very much and wanted to engage earlier in this project but the entire process is beyond my capabilities. If I had the time and brains I'd redesign the driver board for some awesome 8pin op amps and incorporate compensation into the design for fast output transistors. I'd design an entirely new PCB that incorporates current semiconductor offerings. If it worked well I would pursure good PCB layout from a professional software package and order a bunch of boards. I would allow it to fit in existing DC300 chassi mounts but open it up so DIY'ers could use the design in their own. I always liked single sided PCB's so the true hard core DIY'er can fabricate their own PCB's. That is my general opinion and I am very interested in participating if I can.
Jan, the DC300A is not so different than the DC300A II, infact they are very similar but it sounds like you know something I don't. Do you have a DC300 II schematic that is vastly different from the DC300A that resides on the Crown web site?
The original DC300 is an entirely different beast but this is not the amp I refurbished. BTW, I would love to own a DC300 original. 🙂
Cheers,
Shawn.
Shawn;
I've got the service manual for the DC300 II, and there are some differences between the ol DC300A and the newer II 😉
I've got the service manual for the DC300 II, and there are some differences between the ol DC300A and the newer II 😉
DC300A II
Exactly. Some differences but really its the same amp. Here is a peek in the DC300A II. There is the new IOC circuit added and a few component changes on the driver board. Also a few parts were cleaned up from the output board to the speaker terminals.
Other than that it looks itdentical to me. The DC300A's driver board kinda has two star ground areas connected by a link and the DC300A II has a better ground layout with one main ground star. This shifts the components around when you compare the two PCB's but don't let that fool you. Also, the DC300A has additional components to handle higher speed output transistors. I can't see much more difference.
IMO they are almost identical all but a few improvements over an existing design.
So Jan, do you want to modify the DC300 circuitry to improve it?
ACD said:
Exactly. Some differences but really its the same amp. Here is a peek in the DC300A II. There is the new IOC circuit added and a few component changes on the driver board. Also a few parts were cleaned up from the output board to the speaker terminals.
Other than that it looks itdentical to me. The DC300A's driver board kinda has two star ground areas connected by a link and the DC300A II has a better ground layout with one main ground star. This shifts the components around when you compare the two PCB's but don't let that fool you. Also, the DC300A has additional components to handle higher speed output transistors. I can't see much more difference.
IMO they are almost identical all but a few improvements over an existing design.
So Jan, do you want to modify the DC300 circuitry to improve it?
Attachments
My Mistake
Jan, you are right! It is a rev before the II. My Bad. The DC300A II schematic is HERE Still it looks identical to me?
Can you show some pics of the inside of one of your DC300A II's? I'm even more intrigued to learn the differences. Here is a pic of the face of the above, obviously a late model DC300A. Oops. 🙁
Regards,
Shawn.
Jan, you are right! It is a rev before the II. My Bad. The DC300A II schematic is HERE Still it looks identical to me?
Can you show some pics of the inside of one of your DC300A II's? I'm even more intrigued to learn the differences. Here is a pic of the face of the above, obviously a late model DC300A. Oops. 🙁
Regards,
Shawn.
Attachments
Pars said:
Cheers to that Chris. Did you check out the little set of pics at www.dc300a.com ?
I'm very interested in a "new" board layout with upgrades. Jan, lets start a new thread? I guess I'm in the dark regarding the II.
Shawn.
One of my DC300 II are soon having a "service", so I will take some pictures there and post them 😉
Maybe you should follow this thread [http://www.diyaudio.com/forums/showthread.php?s=&postid=1077181#post1077181[/url]
Maybe you should follow this thread [http://www.diyaudio.com/forums/showthread.php?s=&postid=1077181#post1077181[/url]
DC300A II
I just had to see...so I kept looking on the ol Google and I dug up a few glimpses into a DC300A II ...as I said before, its the same amp with a few tweaks and a new face. Unless someone took the face plate off an older model and threw on a version II?
I need to get my hands on another but not for over $300 US as the one going down right now on ebay 😱 . $300 that's crazy but I like it.
Cheers,
Shawn.
I just had to see...so I kept looking on the ol Google and I dug up a few glimpses into a DC300A II ...as I said before, its the same amp with a few tweaks and a new face. Unless someone took the face plate off an older model and threw on a version II?
I need to get my hands on another but not for over $300 US as the one going down right now on ebay 😱 . $300 that's crazy but I like it.
Cheers,
Shawn.
I would like to receive the list of the parts that you used compare to the old ones and a copy of the new PCB that you did. I have a DC300 myself and may try to upgrade it.
Do you have also the modification to reduce the pop sound at startup, shutdown?
Thanks...
algar_emi
Do you have also the modification to reduce the pop sound at startup, shutdown?
Thanks...
algar_emi
"The DC300A II schematic is HERE Still it looks identical to me?"
The DC300AII that I am familiar with has two LF357 J-FET input opamps, not the µA739.
When I sold Crown they would sometimes run out of old style chassis before they ran out of old style circuit boards. I have examples of D150A chassis with D150 circuitry, a common sight.
The DC300AII that I am familiar with has two LF357 J-FET input opamps, not the µA739.
When I sold Crown they would sometimes run out of old style chassis before they ran out of old style circuit boards. I have examples of D150A chassis with D150 circuitry, a common sight.
Algar_emi said:
I will send you some mail. 🙂
djk said:
From everything I've read and looked at and I have not seen it all, Crown was making these DC300A's ~ DC300A II's in a very similar fashion from the mid 70's until the end of production. According to the date code on my original uA739, my amp was built after the final tweaks were made to aid in the fast output transistors & anti-pop/squeal circuit changes but my amp lacked these changes. Which is weird because the service bulletins for these changes are dated for 1974 and 1975. Thats the same date code on my OpAmp. I guess my amp could have been built earlier and someone changed the OpAmp when they repaired it. The repair on my amp could have taken place early in it's life. I find it all very interesting. Jan lives across the pond, so he may have an entirely different story going on in his amps?
Talking to my friend the other day he said the same weird match and placement of components happened alot in auto manufacturing and it becomes obvious when you restore a couple cars of the same make and model.
It's all good. 😀
Shawn.