Hi Shawn,
Amazing job.
May I suggest that you deserve any stray DC300's in the area. You've certainly become a DC300 expert!.
-Chris
Amazing job.
May I suggest that you deserve any stray DC300's in the area. You've certainly become a DC300 expert!.
-Chris
Hi Shawn, I was just thinking, how about a Crown/Amcron DC 300a owners club?
Just a thought................................
S
Just a thought................................
S
re post 338,
there's those damned manufacturers and their Mega Farads again.
Tom Waits,
WELL DONE!! 😎
there's those damned manufacturers and their Mega Farads again.
Tom Waits,
WELL DONE!! 😎
Crown
Shawn
What can I say! ( bloody great jpb well done ) Your the king who is wearing the Crown!!!!
I have been away working all week but I am delighted to see your work
The web site is a great Idea
Please listen to it and give us a few remarks stating the associated equipment etc
As you know I have 1 of these and I am well pleased with it
Out of interest how have you set it up re bias etc
My very best regards Trev
Shawn
What can I say! ( bloody great jpb well done ) Your the king who is wearing the Crown!!!!
I have been away working all week but I am delighted to see your work
The web site is a great Idea
Please listen to it and give us a few remarks stating the associated equipment etc
As you know I have 1 of these and I am well pleased with it
Out of interest how have you set it up re bias etc
My very best regards Trev
Re: Crown
Send them my way indeed. I need number two to start experimenting with the modifications we discussed earlier on in this thread.
I'b be the only member? Heck were is the local DIY Audio Toronto Chapter?
MFD, that's those Americans back when they really hated metric. Must have been the 70's. 😉
It will probably stay in service mode for another week but in the interim I may try to hook it up to some other speakers. I can say for certain it is sounding entirely different from when I last used it as it did have some problems. I adjusted the potentiometers and measured for the voltages listed on the schematic but I'm very interested in what the factory procedures are to be certain.
Thank you folks for the kind words. It sure is a special interest job and I can't wait to see it detailed and assembled. The entire tear down and rebuild was fun and you kind of have this road map in front of you. (I took many more photos of the dismantling process that did not get posted here) The board layout in the service manual is much different than the board layout I have. It was very difficult to balance information from what was on paper vs. the original boards in my hands yet both were required.
The hardest part was turning it on again. 😉 I have more questions to follow and I still need some more help...
Cheers,
Shawn.
anatech said:
Send them my way indeed. I need number two to start experimenting with the modifications we discussed earlier on in this thread.
stewartwen said:
I'b be the only member? Heck were is the local DIY Audio Toronto Chapter?
AndrewT said:
MFD, that's those Americans back when they really hated metric. Must have been the 70's. 😉
latala said:
It will probably stay in service mode for another week but in the interim I may try to hook it up to some other speakers. I can say for certain it is sounding entirely different from when I last used it as it did have some problems. I adjusted the potentiometers and measured for the voltages listed on the schematic but I'm very interested in what the factory procedures are to be certain.
Thank you folks for the kind words. It sure is a special interest job and I can't wait to see it detailed and assembled. The entire tear down and rebuild was fun and you kind of have this road map in front of you. (I took many more photos of the dismantling process that did not get posted here) The board layout in the service manual is much different than the board layout I have. It was very difficult to balance information from what was on paper vs. the original boards in my hands yet both were required.
The hardest part was turning it on again. 😉 I have more questions to follow and I still need some more help...
Cheers,
Shawn.
Hi Shawn,
I don't think anyone would mind trying to help you out sir. You've really done a good job, and the fact is that you finished it. There is a lot to be said for that.
Re: Toronto DIY club. I'd love to hook up with our local members some time. We may need to wait for the snow season to be done and over with though.
-Chris
I don't think anyone would mind trying to help you out sir. You've really done a good job, and the fact is that you finished it. There is a lot to be said for that.
Re: Toronto DIY club. I'd love to hook up with our local members some time. We may need to wait for the snow season to be done and over with though.
-Chris
anatech said:
Do we need to get a members list and fees going to start a TO club or is there already one in existence? Chris, we kind of talked about this on a past thread a little while back. You've been around the block a few times, I’ve chaired a few social committees in my time, perhaps you & I can get something started? Off line discussion?
Shawn.
Hi Shawn,
Sure. Don't know about the fees thing. Might want to get a loose collection of guys in the area and see where they want to go. I'm not that mobile at the moment.
-Chris
Sure. Don't know about the fees thing. Might want to get a loose collection of guys in the area and see where they want to go. I'm not that mobile at the moment.
-Chris
Micro phonic Inputs
As I said earlier I still have some questions/ issues:
The amp runs and sounds fine but when the source is disconnected from the amplifier the input wiring become micro phonic. If you tap the wire, the sound is picked up and amplified. Also, when you place your ear close to the speakers, it sounds like open mic background noise?
Another issue I have is a nasty discharge sound when the unit is turned off. It sounds as though it could be harmful to speakers but it too is no longer present when the input source is connected. Perhaps related?
Any thoughts?
Rock On,
Shawn.
As I said earlier I still have some questions/ issues:
The amp runs and sounds fine but when the source is disconnected from the amplifier the input wiring become micro phonic. If you tap the wire, the sound is picked up and amplified. Also, when you place your ear close to the speakers, it sounds like open mic background noise?
Another issue I have is a nasty discharge sound when the unit is turned off. It sounds as though it could be harmful to speakers but it too is no longer present when the input source is connected. Perhaps related?
Any thoughts?
Rock On,
Shawn.
It sounds to me like you have some stability issues going on there 🙁
I presume you are refering to the wiring internal to the amp? (some coax cable can be noisy in it's own right, especially if feeding into a fairly high impedance, hence "noiseless" microphone cable being available.... not that I have the schematic or specs at hand!)
If the amp is oscillating at some RF frequency then any movement of the cables can frequency modulate the oscillation and sometimes be heard in the output of the amp. If you have an oscilloscope then try looking for supersonic nasties at the output of the amp.... and even at the input! Be carefull though. It would be prudent to fit say 2Amp fast blow fuses to the + & - supply rails when experimenting here 'cos such conditions can cause cross conduction in the output devices and subequent release of the magic smoke
😉
I presume you are refering to the wiring internal to the amp? (some coax cable can be noisy in it's own right, especially if feeding into a fairly high impedance, hence "noiseless" microphone cable being available.... not that I have the schematic or specs at hand!)
If the amp is oscillating at some RF frequency then any movement of the cables can frequency modulate the oscillation and sometimes be heard in the output of the amp. If you have an oscilloscope then try looking for supersonic nasties at the output of the amp.... and even at the input! Be carefull though. It would be prudent to fit say 2Amp fast blow fuses to the + & - supply rails when experimenting here 'cos such conditions can cause cross conduction in the output devices and subequent release of the magic smoke
😉
By all means, the output needs to be viewed on a scope, especially with this much work and changes from stock parts.
Hi Shawn,
Are you using a coupling cap on the input? Make sure you do so that source resistance does not change your DC offset voltage. Really high impedance circuits will pick up the changes in capacitance from a shielded cable being struck. An RC across your input is always a good idea and was stock on this amp I believe.
-Chris
Are you using a coupling cap on the input? Make sure you do so that source resistance does not change your DC offset voltage. Really high impedance circuits will pick up the changes in capacitance from a shielded cable being struck. An RC across your input is always a good idea and was stock on this amp I believe.
-Chris
Hi Shawn,
1: Check your grounds. I.e. zero ohms from the input gnd to power supply ground.
2: I can't see an input capacitor on the scematic, I presume it is on the input socket, check to see that it's there. If not try 1uF.
3: Try putting a 47K resistor directly across the input from signal to shield.
Cheers
Q
PS....what Chris said while I was typing...
1: Check your grounds. I.e. zero ohms from the input gnd to power supply ground.
2: I can't see an input capacitor on the scematic, I presume it is on the input socket, check to see that it's there. If not try 1uF.
3: Try putting a 47K resistor directly across the input from signal to shield.
Cheers
Q
PS....what Chris said while I was typing...
jez said:
In my current set up I have physical coaxial cable feeding the boards left and right. Both channels display the identical characteristics…hmn.
High Impedance…Hmn. Yes Sir! This thing needs to be analyzed and measured: A) to see if it is ok. B) to see if the work changed its performance. Great comment and I need help in this department. Please share your comments in my up coming post regarding testing.EchoWars said:
anatech said:
DC300A…DC stands for direct current amplification. Crown called it a laboratory amplifier. There is no DC blocking/ coupling cap in this schematic that I am aware of. Correct me if I am wrong. Again I read High Impedance…Hmn.
quasi said:Hi Shawn,
1: Check your grounds. I.e. zero ohms from the input gnd to power supply ground.
2: I can't see an input capacitor on the scematic, I presume it is on the input socket, check to see that it's there. If not try 1uF.
3: Try putting a 47K resistor directly across the input from signal to shield.
Cheers
Q
PS....what Chris said while I was typing...
Again, High Impedance, "what Chris said"?
I am certain there is a 820K resistor on my input that is suposed to be a 82K. Big difference there chaps, I'm on it and will post ASAP. Thank you very much. 99% certain
The schematic made me do it, it is a typo but we'll see.Please look at the schematic and tell me I'm not crazy for saying there is no coupling cap, nor should there be one? I thought about putting one in but why not amplify some DC too? I'm being silly, but seriously I think they wanted it this way?
Thanks,
From the Beast & Shawn.
Testing 1,2,3...
OK guys, I have:
Old school Signal generator (HP Audio Oscilator 200AB)
Osciliscope (Hameg HM205-3)
Many DVMs(I just purchased two more)
An old school frequency counter(HP Frequency Meter 500B)
I know the HP's are old but I have the manuals and I have calibrated them. I'm sorry I love tubes too.
What basic test procedures can I go through to check things out without purchasing $$$ for new software/hardware for my PC? Also is there a good dummy load I can build vs. using a large inductive high watt R?
Furthermore, I have access to a cheap digital signal generator and frequency counter as they are around $150 each. I can afford these if you think its a good idea to invest.
Cheers,
Shawn.
OK guys, I have:
Old school Signal generator (HP Audio Oscilator 200AB)
Osciliscope (Hameg HM205-3)
Many DVMs(I just purchased two more)
An old school frequency counter(HP Frequency Meter 500B)
I know the HP's are old but I have the manuals and I have calibrated them. I'm sorry I love tubes too.
What basic test procedures can I go through to check things out without purchasing $$$ for new software/hardware for my PC? Also is there a good dummy load I can build vs. using a large inductive high watt R?
Furthermore, I have access to a cheap digital signal generator and frequency counter as they are around $150 each. I can afford these if you think its a good idea to invest.
Cheers,
Shawn.
Shawn,
Check out HTTP://www.Skycraftsurplus.com they have a 400 watt non-inductive load resistor there for $3.00
PN SK2147
Its 6.6 ohm but well worth the money. You will need to heat sink it.
Check out HTTP://www.Skycraftsurplus.com they have a 400 watt non-inductive load resistor there for $3.00
PN SK2147
Its 6.6 ohm but well worth the money. You will need to heat sink it.
Hi Shawn,
That high input impedance could do it. They may not have installed an input DC blocking cap., but I would. I don't trust anything these days after seeing muting transistors allow the DC control voltage out the rear jacks.
I didn't look at the diagram, but most amps block input DC. Don't feel bad, Krell doesn't either.
-Chris
That high input impedance could do it. They may not have installed an input DC blocking cap., but I would. I don't trust anything these days after seeing muting transistors allow the DC control voltage out the rear jacks.
I didn't look at the diagram, but most amps block input DC. Don't feel bad, Krell doesn't either.
-Chris
1uF
I put a 47k across the input cables and the amp is dead silent, no hum, no 60 cycles, nothing. 😀 Tapping the cable gives a barely audible sound and I am double certain the error is on the 820K resistor. I will adjust and comment further.
I will drop the classic 1uF inline on both inputs. I may be able to manage it into the board and if not I will put it inline with the wire harness.
Thanks!
Now how about a hand with some basic test and measurement?
quasi said:
anatech said:
I put a 47k across the input cables and the amp is dead silent, no hum, no 60 cycles, nothing. 😀 Tapping the cable gives a barely audible sound and I am double certain the error is on the 820K resistor. I will adjust and comment further.
I will drop the classic 1uF inline on both inputs. I may be able to manage it into the board and if not I will put it inline with the wire harness.
Thanks!
Now how about a hand with some basic test and measurement?
Single Audio Taper Pots
Excellent! Also, where can I get a set of single audio taper potentiometers 25k~35k ohm? Not too fancy now but good quality would be nice.
Cheers,
Shawn.
burnedfingers said:
Excellent! Also, where can I get a set of single audio taper potentiometers 25k~35k ohm? Not too fancy now but good quality would be nice.
Cheers,
Shawn.
DC offset
I was mucking about with the DC offset tonight, just messing around until I realised its deadly potential. I took out a woofer on a nice little prototype two-way book shelf I built recently.
It's all good as I still have a few more of those 5 inch woofers. 😉
Cheers,
Shawn.
I was mucking about with the DC offset tonight, just messing around until I realised its deadly potential. I took out a woofer on a nice little prototype two-way book shelf I built recently.
It's all good as I still have a few more of those 5 inch woofers. 😉 Cheers,
Shawn.