Condenser coupling vs Direct coupling

mufster

Well-Known Member
I have an Hitachi HMA-6500 on the way. Until I get my hands on an accompanying pre amp I will use one of my integrated amps as a pre. On the back of the Hitachi there is a switch labelled condenser coupling/Direct coupling. What is the difference and which one should I set it at? I think the amp I may use to is my Sansui QR-6500 or my Oponica SM-4646. I just want to make sure I don't blow something by having it on the wrong setting.

Thanks in advance.

Paul
 
The safest one to use is 'condenser' (not working on steam engines are we?) coupling. This is the setting to use until you can ascertain whether or not the gear you are driving the amp with, puts out any DC.
 
The safest one to use is 'condenser' (not working on steam engines are we?) coupling. This is the setting to use until you can ascertain whether or not the gear you are driving the amp with, puts out any DC.

Thanks for clearing that up Hyperion. So if it works ok on condensor setting, what could happen if I flip the switch to direct? Should I only switch when the amp is powered off?

Paul
 
Yes, only operate that switch (on the power amp) with the power off, and even if you KNOW there is no DC on the output of the pre-amp, you should only operate the switch with the power amp gain controls turned down to minimum/zero.
 
Yes, only operate that switch (on the power amp) with the power off, and even if you KNOW there is no DC on the output of the pre-amp, you should only operate the switch with the power amp gain controls turned down to minimum/zero.

Thank you for the advice. Rrally appreciate it.

Paul
 
I have an Hitachi HMA-6500 on the way. Until I get my hands on an accompanying pre amp I will use one of my integrated amps as a pre. On the back of the Hitachi there is a switch labelled condenser coupling/Direct coupling. What is the difference and which one should I set it at? I think the amp I may use to is my Sansui QR-6500 or my Oponica SM-4646. I just want to make sure I don't blow something by having it on the wrong setting.

Thanks in advance.

Paul

That amplifier is direct coupled from input to output, no capacitors coupling the signal from input to output. There was a period in which some manufactures made a big deal of their amplifiers being able to pass and amplify a DC input right through the gain stages to the speaker outputs. That can be a real issue if there is any DC leakage from the preamp that is driving the amplifier as it will be amplified with the same gain as if it were a signal, which is AC. Putting the switch in the condenser position simply inserts a capacitor in line with the input of the amplifier to block any incoming direct current that might be present. Practically all power amps have this DC blocking at their inputs and practically all preamp designs have them at their outputs. I would leave the switch in the condenser position to protect those expensive and difficult to service mosfets as well as the woofer in the speakers.
 
That amplifier is direct coupled from input to output, no capacitors coupling the signal from input to output. There was a period in which some manufactures made a big deal of their amplifiers being able to pass and amplify a DC input right through the gain stages to the speaker outputs. That can be a real issue if there is any DC leakage from the preamp that is driving the amplifier as it will be amplified with the same gain as if it were a signal, which is AC. Putting the switch in the condenser position simply inserts a capacitor in line with the input of the amplifier to block any incoming direct current that might be present. Practically all power amps have this DC blocking at their inputs and practically all preamp designs have them at their outputs. I would leave the switch in the condenser position to protect those expensive and difficult to service mosfets as well as the woofer in the speakers.

Thanks. Yep, gonna leave it on condenser coupling to be on the safe side.

Again, to all the advice from everyone. Thank you so much!

Paul
 
A switch cannot bypass ( or set on ) ALL cap coupling on all stages.

I think ( as there is a switch like this on my Nikko Alpha 220 ) the switch is
only there to bypass INPUT caps, not all caps on every stages.

Not to worry about caps at output stages.
 
Update. I put it on condenser coupling and it works fine with my Optonica SM-4646 as a pre. However, I have just snagged the pre for this power amp, a HCA-6500 and wondered do I now switch to direct coupling?

Thanks in advance.

Paul
 
I would try it, but with all the caveats that I mentioned in operation, like set any coupling switches FIRST, all gains at zero/min then power on pre-amp first, wait a few seconds then power on the power amp.

Watch / listen for any abnormalities.
 
A Sony power amplifier I have has this switch on the back as well. In the manual it states to only use the switch for testing. It didn't state what tests but it is better to leave it in "normal" mode for reasons stated above. With all the burnt resistors I had to replace I'm guessing someone ran it in "DC" mode.
 
I have an HA-7700 (Hitachi) with the same switch. In direct coupling mode I can detect the slightest improvement in clarity so I leave it there.

Here is an excerpt from the service manual for it....

And, here is what Wualta told me in another thread on it.
http://mail.audiokarma.net/forums/showthread.php?t=525980&page=2
"The DIRECT/CAPACITOR switch is normally left in the DIRECT position. The manual says you should check for DC from sources by flipping the switch and listening for pops! Which would certainly work as a test for DC, but could be unnerving for the owner. On my Hitachi MOSFET amps, the sound is noticeably better with switch in DIRECT."

On mine I didn't hear any pops while flipping the switch back and forth while on. I'm not advocating that practice. Just saying mine obviously had very low dc, but it is also an integrated so the pre is built in.
 

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