Hafler DH-500 Question

[shinkamp]

Hello Knowledgeable Audioholics,

Due to a strange circumstance I came to look at my Hafler DH-500 amplifier today. I noticed that the front plate on the amplifier does not have an on/off switch. Almost all images of the DH-500 on the internet have an on/off switch with a red light on the front plate. I looked on the back and there is a small silver toggle switch by where the power cord comes out. I couldn't find any images of this on the internet. I toggled it up and down but the audio didn't seem to change. If the amp was shut off, would the audio continue to work? I don't have a preamp. My amplifier is wired to a high-end Yamaha RX-A3000 receiver. I guess I just assumed that there would be no sound when I toggled that switch. Can anyone shed some light on this for me?

Thanks.

shinkamp

 

[TLS Guy]

Hello Knowledgeable Audioholics,

Due to a strange circumstance I came to look at my Hafler DH-500 amplifier today. I noticed that the front plate on the amplifier does not have an on/off switch. Almost all images of the DH-500 on the internet have an on/off switch with a red light on the front plate. I looked on the back and there is a small silver toggle switch by where the power cord comes out. I couldn't find any images of this on the internet. I toggled it up and down but the audio didn't seem to change. If the amp was shut off, would the audio continue to work? I don't have a preamp. My amplifier is wired to a high-end Yamaha RX-A3000 receiver. I guess I just assumed that there would be no sound when I toggled that switch. Can anyone shed some light on this for me?

Thanks.

shinkamp

From what I can tell, Hafler made a PA version of that amp, which had no power switch. This is probably so it could get switched from a main control center, and they did not want the amp getting accidentally switched off. I have no idea what that rear switch is about, but I can be certain it is not a power switch.

 

[Trebdp83]

Perhaps a DIY mod? Here are some pics of something similar, though this unit is equipped with a switch on the front panel.

 

[TLS Guy]

Perhaps a DIY mod? Here are some pics of something similar, though this unit is equipped with a switch on the front panel.

View attachment 71804View attachment 71806
View attachment 71807

I have researched this further. He has the pro version which has no front switch and that toggle switch on the back changes the fan speed. So if the OP wants to use this amp, he needs to have an external switch unit.

 

[shinkamp]

Hello and thank you to those who replied to my first post. Your answers got me thinking and I decided to open up the DH-500 and see what's inside. The toggle switch is wired with 2 large green wires. One is grounded to the chassis and the other is soldered to the lowest (of the 3) spades where the female power cord pushes into the amp. I also noted that the amp has Nippon Chemi Con (18000 uF, 100 volt) caps and there are 2 (slightly longer than an inch) beige rectangular components which are shedding some white powder. They are labeled Colber 300 Ohm 10% 7W. I may get someone to "freshen up" this amp in the future so any insight into the toggle switch or better components would be greatly appreciated. Attached are some pictures. I'll try not to take up any more of your time after this and thank you very much..
shinkamp