Denon HA500: Channel Imbalance, Hum, ETC

[avantbored]

Hi all.

Picked up some gear from a local guy who's unloading some unused kit. He's very careful with his components and tends to only buy from other enthusiasts and audiophiles. When gear isn't working functioning, he usually sends it to a reputed shop in my area (Los Angeles).

This is just some anecdotal context to say the issues with the component in the title aren't from a flipper or heir who's out of their depth with audio gear.

The kit I picked up:
Denon HA-500
Denon DL301 MK1
Yamaha M4 (unexpected! been on my list of to-one-day-own amps)

Chief complaint: Denon HA-500 MC Cartridge Amplifier presents channel imbalance (left louder than right) and hum on both channels.

I have this hooked up to the MM of my Nakamichi CA7A (NB: Some of you may be thinking, "Why do you want to hook up a MC head amp to a preamp with a built-in MC stage, and a flexible and very good one at that?" We all get curious!), and the head amp hum hum hums while the left channel sounds fine and the right channel is weak. Some scratchiness while operating the knob (stepped, just to turn it on and off).

I opened up the head amp and didn't see anything, though some caps did wiggle.

Any ideas?

Specs of both the preamps:

Denon HA-500
■ Head amplifier for MC type cartridge
■ Input impedance 100Ω
■ Gain 0dB (PASS), 24dB, 32dB switching
■ Output level 2.5V
■ Frequency band 10-600,000Hz + 0dB -1dB (24dB) 10-600,000Hz + 0dB -3dB (32dB)
■ Total harmonic distortion 0.008% (0.3V output 20-20,000Hz)
■ Intermodulation distortion 0.008% (0.3V output)　
■ Input conversion noise -157dB (RMS, RIAA + IHF-A, input (Short)
■ Channel separation 70dB
■ Power consumption 14W
■ Power supply AC120V 50 / 60Hz
■ Weight 2.2kg
■ Dimensions W12.6 × H7.1 × D30.5cm
■ Release September 1978
■ End of sale 1985


Nakamichi CA7A
Frequency response: 1Hz to 100kHz

Total harmonic distortion: 0.002%

Input sensitivity: 0.16mV (MC), 2.5mV (MM), 150mV (line)

Signal to noise ratio: 84dB (MC), 88dB (MM), 94dB (line)

Output: 150mV (line), 2V (Pre out), 7V (Pre out Max)

Dimensions: 435 x 82 x 310mm

Weight: 7.2kg

 

[hoodie]

The simplest steps would be to make sure that all of your connections are clean and check that the components in the signal chain are properly grounded. Also, try moving the SUT away from any power cables and or power supplies. It might be a bigger issue but doing this might help with the hum that you are hearing.

 

[avantbored]

Thanks for the tips. I performed the following:

1) Moved the HA500 head amp away from power units (pre and power).

2) Into Yamaha C65 and Nakamichi preamp.

--> Moving it and hooking it up to the Yamaha: Hum gone, and stereo image strong. However, after about a day, the left channel dropped. Then:


3) Into Nakamichi.

--> The channels came back. The hum disappeared. Then the left channel died again.


4) Removed the HA500 from the chain. Channels are good and stereo image is good.

5) Back into Nak. Hum returns.

 

[tabarddn51]

Hi, The HA500 head amp is a fantastic sounding unit, (bass is to die for) I have one playing now. However as you found out HUM is a huge problem.
Fix, Open up the unit & remove the Trans, Then set up with a low noise +/-17.5VDC separate power supply with ambilocal cord. Now my system has NO hum, set a 32db.

Cheers
PS I have no channel balance concerns.

 

[jlangloi]

Hi, The HA500 head amp is a fantastic sounding unit, (bass is to die for) I have one playing now. However as you found out HUM is a huge problem.
Fix, Open up the unit & remove the Trans, Then set up with a low noise +/-17.5VDC separate power supply with ambilocal cord. Now my system has NO hum, set a 32db.

Cheers
PS I have no channel balance concerns.

I realize the discussion has been idle for a while, but I am looking for help to clean the contacts on the switch as I have a similar problem as described by avantbored the original author. Can you describe what “remove the Trans” is? Can this be the covered section protecting the extended shaft that runs from the switch knob to the rear of the HA? Thanks

 

[tabarddn51]

Hi, I actually totally removed the 100VAC transformer. Wired in a stand-a-lone +/- DC power supply,

Cheers