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Parasound HCA-750A and HCA-1000A

heeman

Well-Known Member
Famous
You guys know that I am upgrading my 2.1 to a 5.1 system.

I got carried away and have purchased these two amps; Parasound HCA-750A and HCA-1000A.

The HCA-1000A will power my Studio 60's (fronts) and the HCA-750A will power my Studio 20's (rears). My B&K Reference 125.2 will power my center Studio CC V2 (I will use only one channel).

Therefore the Onkyo TX-NR708 will be used as the Preamp/Processor only.

Making slow progress on the system setup, these amps will arrive this week.

Overkill adding these amps...............nah!!! :happy-smileygiantred: :happy-smileygiantred: :banana-rock: :happy-smileygiantred: :happy-smileygiantred: :music-rockout: :music-rockout:
 

DIYer

Well-Known Member
Famous
Wait till you go active crossover. It will double the number of amps. :icon-twisted:
 

heeman

Well-Known Member
Famous
I received the HCA-750A tonight.

The past owner must have been a heavy smoker, the unit smells pretty bad.

I removed the cover vacuumed it out and wipped her down.

Would a good rinse with tuner cleaner help the situation??

The PCB is a very simple, a single sided board, the input power supply capacitors seem a little stressed (a little hump under the vents, probably normal). I powered the amp up and it comes on. I will connect to the Studio 20's tomorrow for a real test drive.
 

Botch

I.Y.A.A.Y.A.S!
Superstar
heeman said:
I received the HCA-750A tonight.

The past owner must have been a heavy smoker, the unit smells pretty bad.

I removed the cover vacuumed it out and wipped her down.

Would a good rinse with tuner cleaner help the situation??

The PCB is a very simple, a single sided board, the input power supply capacitors seem a little stressed (a little hump under the vents, probably normal). I powered the amp up and it comes on. I will connect to the Studio 20's tomorrow for a real test drive.
As a bar musician of many years I recommend air, and lots of it. If you have a breezy porch that's secure, leave her out for a few days.
 

Rope

Well-Known Member
Famous
When purchasing used electronics, and if it's not stated in the description, always ask if the gear is from a smoke free environment, if not, avoid purchasing.

Rope
 

Flint

Dog Faced Pony Soldier
Superstar
Just about every used electronic component I have purchased online wreaked of smoke despite being assured repeatedly by the seller that it was never placed in a smoke filled environment. Smoke ruins electronics as the ash in tobacco smoke is positively charged ions and are attracted to the grounded conductive surfaces, such as pots, sliders and switches.

I recommend getting some Caig cleaning fluids to clean and preserve the pots, switches and connectors.
 

heeman

Well-Known Member
Famous
I hope that I can explain this in written words properly so that you guys can help me out.

I connected the HCA-750A to the Studio 20's.

I took the Input connections from my B&K Amp and connected them to the 750A.

Everything sounded great. Cranked some tunes, put the audio from the TV through it. I wanted to run the amp most of the night while watching TV.

We sat down for Dinner and my wife got up from the kitchen table and said she heard a hum from the speakers, and indeed she did. Here is what I did to try to isolate the problem.

1. I changed Inputs on the receiver. Hum still there.
2. I disconnected the inputs to the 750A and the hum went away.
3. I connected the analog outputs from the SqueezeBox directly to the 750A and NO HUM.
4. I turned off the Yamaha (pre-amp) and left the inputs to the 750A and the hum was still there.

So, I figured that if I hooked up the input back to the B&K Amp, I should here the hum through the Studio 60's.........NO HUM.

I connected the inputs back to the 750A and the hum was there again.

The hum seemed to start after the amp was running for about 2 hours (well heated). I will let it cool down and try again.

I also wiggled the cables feeding the 750A and the hum did not change.

I made these cables a couple of years ago under the instructions of you guys over on the other forum and the are made correctly and I do not have the hum through my current system.

What Gives????? All Input Welcomed!
 

Yesfan70

I'm famous now bitches! vvvvv
Famous
Rope said:
When purchasing used electronics, and if it's not stated in the description, always ask if the gear is from a smoke free environment, if not, avoid purchasing.

Rope

Agreed. "When in doubt, throw it out".



My old man was a heavy smoker. He had a set of Yamaha speakers he gave to me one time. I had the matching bookshelfs and thought this would make a decent 2nd 5.1 system in another room. I never could get that smoke smell out of his speakers, so I dumped them off to my brother who later dumped them off at a Salvation Army store.
 

PaulyT

Behind the Curtain
Staff member
Administrator
Moderator
Superstar
? Heeman, I don't understand how you've got stuff hooked up, between the receiver (yamaha), 750a, and b&K. Why would the two amps (750a and b&k) be connected together?

Or are you saying that you alternated between the b&k and the 750a, powering the (same?) speakers, and that only the 750 made the hum?
 

heeman

Well-Known Member
Famous
I knew that this would be difficult with words.

The 2 amps are not connected together.

To try (burn in) the Parasound 750A. I simply connected it to the Studio 20's.

I unplugged the inputs to the B&K and plugged them into the 750A.

I also unplugged the power cord from the B&K and plugged that into the 750A.

After about 2 hours of running a hum developed.

Above is what I tried to isolate, trouble shoot the hum problem.
 

soundhound

Well-Known Member
If I'm reading correctly, it sounds like a ground loop between your preamp and the power amp. If the hum goes away when the amp is disconnected from anything other than the speakers, then the amp is not producing the hum.
 

heeman

Well-Known Member
Famous
That's what I thought, however it only happened after the amp heated up.

That is what confused me.

Not sure why this ground loop does not exisit with the B&K AMP and the 60's.

It has the same input and same power cord..........just doesn't make much sense.

Anyway................
 

soundhound

Well-Known Member
If the amp only hums when connected to a specific input source (even when hot), then the fault is not likely with the amp. I can't think of anything electronic in your power amp which would produce hum only when connected to one particular input source like your preamp and not another. Of course something could still be wrong with the amp which would require a service tech to sort out, but in my over 30 years of working with amps of all types (and designing the stupid things), it just seems unlikely that it is the fault of the amp.

If the hum was caused by a filter capacitor breaking down (the indentations on the tops of electrolytic capacitors is intentional so that if they short, they will release the internal pressure gracefully and not explode outright), then the amp would hum with nothing connected to its input, but you say that is not the case. Frankly, about the only thing inside an amp which can cause hum is something wrong with the power supply, and more specifically something wrong with the filtering capacitors or decoupling capacitors. The only other cause of hum might be a defective rectifier. None of that stuff is something which you can repair and would have to be repaired by a tech.
 

heeman

Well-Known Member
Famous
Soundhound - thanks all good suff.

Any suggestions on how to eliminate the ground loop hum?

Any idea's what this does not occur when the Yamaha is connected to the B&K Power Amp and only the 750A??

Please educate me!!!!

Also, PM sent.........
 

heeman

Well-Known Member
Famous
Thanks!

I am still confused why, when the only variable is the Power Amp (connected to the same power source) it has this problem and not the other. The Input Voltage source was from the same power cord plugged into the same outlet for God Sakes!!! :angry-tappingfoot:
 
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