You've come along way baby...
Let 'er rip and don't hold back!
It will be a happy amp in a rack full of EQs blasting to high hell in some PA system 
or I could keep it as my secret party weapon. Not bored at all, I'm having a blast! Your sentiment is well recieved, look at my first post.
I'm having fun and this amp deserves it! It is "beastly" and what kid out there with a big frickin pair of speakers wouldn't want an amp like this?
Shawn.
burnedfingers said:Please take it out in the country and either bury it or shoot it. Put it out of its misery at any rate.
You guys must be bored to death..... please try something else to waste your time....
Let 'er rip and don't hold back!
It will be a happy amp in a rack full of EQs blasting to high hell in some PA system or I could keep it as my secret party weapon. Not bored at all, I'm having a blast! Your sentiment is well recieved, look at my first post. I'm having fun and this amp deserves it! It is "beastly" and what kid out there with a big frickin pair of speakers wouldn't want an amp like this?
Shawn.
Attachments
I don't know Shawn........
I think nowdays even the younger crowd might just pass up that jewel in favor of a flame linear or something less disgusting sonically.
Take a look at what they put in their cars.....do you really think the old clown DC300 would be worth anything to them?
Na.... please just take in out into the country and bury it. I'll even pop for the gas to make the trip.
Hell, we could throw it a wake first.....
I think nowdays even the younger crowd might just pass up that jewel in favor of a flame linear or something less disgusting sonically.
Take a look at what they put in their cars.....do you really think the old clown DC300 would be worth anything to them?
Na.... please just take in out into the country and bury it. I'll even pop for the gas to make the trip.
Hell, we could throw it a wake first.....
Dont listen to them Tom
Just restore the amp to as new a condition as possible! Try improved devices
I like the Crown In my collection I have A 400B flame linear (love that name) its my favourite Also i Have a BGW 750c But If my life were amp dependend I would go with the Amcron
The whole point is to keep the sound of that amp and time alive
after all its a classisic from the seventiers.
It would be like comparing a 1975 motor car with a new model
It owes nobody an excuse for its excistance its all ready done 30 years service
As to the lads ideas re the opamp supplies etc go with it and change the devices.
the metal washers are hard anodised alloy but i am under the impression that they are under ideal conditions a one shot device and should be replaced when you change the output devices
Any way I think its a landmark sound against which others can be judged
regards Trev
Just restore the amp to as new a condition as possible! Try improved devices
I like the Crown In my collection I have A 400B flame linear (love that name) its my favourite Also i Have a BGW 750c But If my life were amp dependend I would go with the Amcron
The whole point is to keep the sound of that amp and time alive
after all its a classisic from the seventiers.
It would be like comparing a 1975 motor car with a new model
It owes nobody an excuse for its excistance its all ready done 30 years service
As to the lads ideas re the opamp supplies etc go with it and change the devices.
the metal washers are hard anodised alloy but i am under the impression that they are under ideal conditions a one shot device and should be replaced when you change the output devices
Any way I think its a landmark sound against which others can be judged
regards Trev
burnedfingers said:
You've mistaken me. I'm the kid! Doing this makes me feel like I was a kid again. I remember putting a bid on a set of amps in Glace Bay, Nova Scotia. This older chap was selling his pride as he was hanging up his dreams and getting a day job. In the pile of goodies was a Crown DC300A mounted in the Crown enclosure. That was my first sight of DC300A. I didn't buy it because I purchased some new junk from the music store. I was 16 years old. I remember it like it was yesterday.
To pick up a DC300A (vintage '75) for free in the basement of a dirty old pub? Dream come true, might as well be written in the stars! For me it is all fun. No I'm not a kid anymore but having the skills and knowledge to do this and then actually apply it? Man, I can't think of anything better in the world I'd rather be doing. Well there are a few other things but they don't last all day.
If the DC300A sounds like a sheet of glass then damn yee all, I'm going to make it the best sounding piece of glass it can be. I'm behind the mule and I've got my hands on the plow. Get out of the way naysayer's, I'm coming through....
Trev, I don't listen to nobody if they don't listen to me
I'm just havin my fun, they can hate it, though I don't think it wise to post hate, makes ya look funny.
Shawn.
Some cut-and-paste from my previous posts on Crown:
I have the Crown service manual for that model, the cover actually says:
"300 WATTS AND A CLOUD OF SMOKE"
Basic Service Suggestions for the CROWN DC-300 Amplifier
If anyone needs a copy, let me know. Contains material not found on-line at Crown.
DC300A = broken glass
DC300 = hand-grenade
D150 = broken glass waiting to hand-grenade
PSA2 (SA2) = OK sounding and reliable
BGW uses the LM318 in inverting mode, 70V/µS, vastly better sounding than the 1V/µS µA739 found in the same vintage Crown amps.
If you have a 'C' vintage or newer BGW750, a cap upgrade will make it sound better than 99.9% of most hi-fi amps. Quieter fans are available.
The Crown D60/75 and the PSA2 are OK, you can keep the rest.
The amplifier that PWK measured as having the lowest TIM distortion he had ever measured (in the DFH Vol. 16, No. 8, Sept '77), was the BGW100. While the BGW measures great, a cap upgrade will make it sound even better (the Crown D60/75 will also sound better with similar attention).
Unfortunately there is no easy upgrade for the µA739 Crown used, or the quasi-comp output stages in the early Crown and BGW models. The caps do make a big difference though, and costs are very low for the DIY owner.
"With my limited knowledge of power amps I looked at the schematic on the DC300A and it looks like short of making a new input/driver board I don't see how you could change much to make it better. Maybe removing the all the compensation parts and making a small board to fix the pinout that holds a modern internally compensated op amp."
It's too much work for the end result.
VanAlstine has the right idea for a dead one. Gut it for the chassis and supply, then do a fresh design.
I have the Crown service manual for that model, the cover actually says:
"300 WATTS AND A CLOUD OF SMOKE"
Basic Service Suggestions for the CROWN DC-300 Amplifier
If anyone needs a copy, let me know. Contains material not found on-line at Crown.
DC300A = broken glass
DC300 = hand-grenade
D150 = broken glass waiting to hand-grenade
PSA2 (SA2) = OK sounding and reliable
BGW uses the LM318 in inverting mode, 70V/µS, vastly better sounding than the 1V/µS µA739 found in the same vintage Crown amps.
If you have a 'C' vintage or newer BGW750, a cap upgrade will make it sound better than 99.9% of most hi-fi amps. Quieter fans are available.
The Crown D60/75 and the PSA2 are OK, you can keep the rest.
The amplifier that PWK measured as having the lowest TIM distortion he had ever measured (in the DFH Vol. 16, No. 8, Sept '77), was the BGW100. While the BGW measures great, a cap upgrade will make it sound even better (the Crown D60/75 will also sound better with similar attention).
Unfortunately there is no easy upgrade for the µA739 Crown used, or the quasi-comp output stages in the early Crown and BGW models. The caps do make a big difference though, and costs are very low for the DIY owner.
"With my limited knowledge of power amps I looked at the schematic on the DC300A and it looks like short of making a new input/driver board I don't see how you could change much to make it better. Maybe removing the all the compensation parts and making a small board to fix the pinout that holds a modern internally compensated op amp."
It's too much work for the end result.
VanAlstine has the right idea for a dead one. Gut it for the chassis and supply, then do a fresh design.
I found a used Crown at a music store about a decade ago.
But it's a Crown IMA, the intermodulation analyzer; I really wanted one of these more than an amplifier. Picked up for $35 and passed over a small Crown amplifier, I think it was a DC150. I'd had a manual for years prior to that.
Alas, both meters are non-functional and getting their movements replaced would cost a couple of hundred dollars if I could find someone capable of doing the work. There were other problems as well leading me to suspect the unit got fried by a lightning strike. I shotgunned the small electrolytics and got the oscillators working, but that's all the progress I've been able to make.
Current distortion analyzers are increasingly geriatric Heathkits with distortion floors above .01%; I really want to get things down to at least .001% but can't afford Audio Precision...
But it's a Crown IMA, the intermodulation analyzer; I really wanted one of these more than an amplifier. Picked up for $35 and passed over a small Crown amplifier, I think it was a DC150. I'd had a manual for years prior to that.
Alas, both meters are non-functional and getting their movements replaced would cost a couple of hundred dollars if I could find someone capable of doing the work. There were other problems as well leading me to suspect the unit got fried by a lightning strike. I shotgunned the small electrolytics and got the oscillators working, but that's all the progress I've been able to make.
Current distortion analyzers are increasingly geriatric Heathkits with distortion floors above .01%; I really want to get things down to at least .001% but can't afford Audio Precision...
Shawn,
I don't think there are too many knowledgeable diyers out there that would admit to wanting to own one. Many of us as a course of putting food on the table over the years have actually forced themselves to repair the product for another owner. We haven't enjoyed it but we've done it. The good thing about repairing one is not having to listen to it until its burned in. The bad thing is forcing oneself to listen to music thru it after the bench testing is complete.
Joe... you are too cruel today!
The big ole' crown would be killer for young rock band!
I had plenty of the BGWs...still have one. I use at 25 kHz with 24 ebay piezos to drive the neighbors dogs inside...
These are 69 Roadrunners... with hemi's.
C'mon man... the only you could break those Crowns was to actually tie them to a boat and throw them overboard... and even then you had to turn the power up and let it go for week.
The big ole' crown would be killer for young rock band!
I had plenty of the BGWs...still have one. I use at 25 kHz with 24 ebay piezos to drive the neighbors dogs inside...
These are 69 Roadrunners... with hemi's.
C'mon man... the only you could break those Crowns was to actually tie them to a boat and throw them overboard... and even then you had to turn the power up and let it go for week.
I won't dirt on the sound of the 300, as I haven't experienced it. It's just that audio and semiconductor technology have moved on quite a bit from the time the amp was designed. It will be interesting to see if the amp will reveal a sweeter character when refurbished properly, or whether scrubbing off the dirt will reveal a host of audio warts and sores better left covered. My major concerns would be 1) ditch the cheap carbon pots, and replace them with cermet or plastic, or at least replace them with new parts. The old open frame pots tend to film over and go open circuit. 2) Replace the caps, but you were going to do that anyway 3) Maybe ditch the TO-5 drivers for some modern TO-220s with adequate heat sinks. 4) Replace the outputs with parts that are faster with more linear gain vs. current, and larger SOA.
I had to fix a Flame Linear 400 that had done just that, mostly due to the fact it was DC coupled and was forced to pump DC into a short. I replaced the old Delco output devices with some RCA 2N6678s. I also put in an input coupling cap....
I had to fix a Flame Linear 400 that had done just that, mostly due to the fact it was DC coupled and was forced to pump DC into a short. I replaced the old Delco output devices with some RCA 2N6678s. I also put in an input coupling cap....
