Well I got the amp today! I put the volt meter on DC 200m setting and on the left channel all four outputs read .7 and on the right channel all dour read 1.4
It hasnt been turned on in several years (maybe as many as 10 years). I have turned it on and hooked a speaker to both channels and its playing. Now I'm just letting it sit here turned on for a few hours so it can wake up and stretch. After that I'll test the speaker outputs again.
Are those readings I got, okay? Is there something else I should/can test with my cheap standard meter? Can I figure out how much power each channel puts out and if they are in balance?
It hasnt been turned on in several years (maybe as many as 10 years). I have turned it on and hooked a speaker to both channels and its playing. Now I'm just letting it sit here turned on for a few hours so it can wake up and stretch. After that I'll test the speaker outputs again.
Are those readings I got, okay? Is there something else I should/can test with my cheap standard meter? Can I figure out how much power each channel puts out and if they are in balance?
That certainly seems fine. Run the amp for several hours continuously to let the capacitors reform.
Without other test equipment, after it's burned in, turn off the power and hook up the preamp,
a source, and a pair of (cheaper) speakers. You can judge the balance that way.
A mono recording is best for this purpose, if you have one. The amp is probably better
balanced than your volume control.
I wouldn't worry about the maximum power just now, it's likely to be in spec.
Without other test equipment, after it's burned in, turn off the power and hook up the preamp,
a source, and a pair of (cheaper) speakers. You can judge the balance that way.
A mono recording is best for this purpose, if you have one. The amp is probably better
balanced than your volume control.
I wouldn't worry about the maximum power just now, it's likely to be in spec.
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WAY too much offset. Great amp, but it needs servicing. Recapping, adjust the bias. As I mentioned, I had three of them and am sorry I let them go.
DQ10's. Have not heard them for years. They were /are quite something. I'm with the Ozark DR. pass on a PL. Amazing any still work as they were cheap cheap cheap. Only claim to fame was high power. Carver was clever, but products were cheap.
You can get the schematics on-line if you look. Might even find service manual for any in the line as the basic design was all the same so adjustments the same. Sorry, I had them but deleted my old stuff a few months back. Really, strait forward three stage amp. Only unique feature was the floating bias for the complementary diff FET front end. Do be careful as you can't get any of those parts any more.
What you want is what it will do in spades once in top nick.
DQ10's. Have not heard them for years. They were /are quite something. I'm with the Ozark DR. pass on a PL. Amazing any still work as they were cheap cheap cheap. Only claim to fame was high power. Carver was clever, but products were cheap.
You can get the schematics on-line if you look. Might even find service manual for any in the line as the basic design was all the same so adjustments the same. Sorry, I had them but deleted my old stuff a few months back. Really, strait forward three stage amp. Only unique feature was the floating bias for the complementary diff FET front end. Do be careful as you can't get any of those parts any more.
What you want is what it will do in spades once in top nick.
"WAY too much offset."
Those numbers are in mV, not V, and are fine.
Just what you'd expect from a DC servo.
Those numbers are in mV, not V, and are fine.
Just what you'd expect from a DC servo.
If it were mine, I'd run it for 3-4 hours, but not overnight.
I like to be around when equipment is running.
Make sure there is plenty of ventilation (don't place the amp on carpeting).
If it plays when you hook up the speakers, you certainly got your money's worth.
Now you'll have to buy some high end speakers with 1 ohm impedance dips
to use that high current.
I like to be around when equipment is running.
Make sure there is plenty of ventilation (don't place the amp on carpeting).
If it plays when you hook up the speakers, you certainly got your money's worth.
Now you'll have to buy some high end speakers with 1 ohm impedance dips
to use that high current.
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Okay that's what I had in mind, I felt a bit hesitant to leave it on overnight until I trust it a bit more. Will it be a potential issue to play music for these few hours at a low volume? Would it be better to let it sit there doing nothing?
So the 200m setting on the meter giving a reading of .7 is less than a millivolt, correct? So eventhough they are different (.7 vs 1.4), its less than a millivolt of difference between them, correct? How many millivolts total and difference is too much? (I bought two of these amps so going to fire up the other one tomorrow)
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Those readings are totally inconsequential. Most amps would be considered OK
and normal with even 50mV or more DC offset.
But I would not recommend leaving a high power amp on for long periods of time
unless you were in the room.
You got TWO of them?
and normal with even 50mV or more DC offset.
But I would not recommend leaving a high power amp on for long periods of time
unless you were in the room.
You got TWO of them?
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Yes, when I got there he actually had two so I got them both!
So these play 6wpc in class A before switching to AB....if I run it in mono and use one amp for each channel, would it still only play 6wpc class A or would it double to 12wpc since the power doubles?
The channels function independently unless bridged.
Bridged for mono, it is a 1kW amp into 4 ohms, but they recommend
in normal use 8 ohms, giving 750W.
https://www.parasound.com/pdfs/vintage/hca2200llom.pdf
Can we assume you have some large speakers?
Bridged for mono, it is a 1kW amp into 4 ohms, but they recommend
in normal use 8 ohms, giving 750W.
https://www.parasound.com/pdfs/vintage/hca2200llom.pdf
Can we assume you have some large speakers?
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What I was mostly wondering is if the class A power increases or if it would still only be 6watts of class A? I couldnt find any info about that.
No, that would require paralleling the stereo outputs, which is not allowed.
The two channels are independent unless bridged.
Mono in this amp (like in most) means connecting the speaker between the
two positive outputs (bridged), and inputting two out-of-phase mono signals.
The needed phase inverter is included internally, connected with the mono switch.
This doubles the output voltage (4x the power of one channel, if the design can handle it).
The two channels are independent unless bridged.
Mono in this amp (like in most) means connecting the speaker between the
two positive outputs (bridged), and inputting two out-of-phase mono signals.
The needed phase inverter is included internally, connected with the mono switch.
This doubles the output voltage (4x the power of one channel, if the design can handle it).
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You would get the same # of class A watts in mono as stereo. The class A region is defined by the bias current - it will leave class A at some fixed current output. When you drop the impedance to 4 ohms, you get the same peak current at half the power - so 3 watts in class A before transitioning to B. When you bridge an amp with 8 ohm load, you add the 4 ohm power from each channel. That puts you back at 6 watts before leaving the class A region.
@rayma @wg_ski sounds good, thanks for the info!
Now I need to find someone to do the mods to these amps. I have good detailed instructions but I just dont understand enough about what's going on in a amp to do that myself.
Now I need to find someone to do the mods to these amps. I have good detailed instructions but I just dont understand enough about what's going on in a amp to do that myself.
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Well, I wouldn't change anything until you've used them for a good while.
You may decide they're fine as they are. And there's always the possibility
of somebody mucking them up, so whoever does eventually work on them
should be able to prove they have successfully done so previously.
You don't want to be his "first". And if the suggestions are not from
(or approved by) JC then I'd think twice, or three times.
You may decide they're fine as they are. And there's always the possibility
of somebody mucking them up, so whoever does eventually work on them
should be able to prove they have successfully done so previously.
You don't want to be his "first". And if the suggestions are not from
(or approved by) JC then I'd think twice, or three times.
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These amps are pretty well-designed as it is... I'd be very hesitant to do much to them. I'd enjoy them as they are.
It sounds to me like you got a pair of good, working amps. Honestly, at this point, I'd be VERY surprised if any issues popped up. These amps are pretty simple.
I bought two of these....Looks like one of them sounds fantastic, the other one is playing but its staticky so it has some issues. After sitting for several hours turned on the DC millivolts in the good sounding amp leveled out to .6 in all outputs. In the staticky amp they measure .6 on the left and zero on the right.
On the staticky amp both channels have that same issue
On the staticky amp both channels have that same issue
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Thinking about the amp that has the static in both channels, I think I've read that these amps mostly keep both channels completely seperate....it seems like that would really reduce the possibilities of what could be causing the same static in both channels. I suppose both channels could have the same damage part, but I figured theres probably something that both channels rely on that might have the issue.