Which trimmer?
Regarding transistors and heatsinks, It depends if the transistor has exposed metal and if the heatsinks are connected to anything else such as ground that would cause a short circuit. Safe thing to do is to use insulators and heat sink compound to mount the power transistors.
https://www.google.com/search?q=to-...i30j0i390l4.8439j0j1&sourceid=chrome&ie=UTF-8
Regarding transistors and heatsinks, It depends if the transistor has exposed metal and if the heatsinks are connected to anything else such as ground that would cause a short circuit. Safe thing to do is to use insulators and heat sink compound to mount the power transistors.
https://www.google.com/search?q=to-...i30j0i390l4.8439j0j1&sourceid=chrome&ie=UTF-8
IIRC the Sanken darlingtons in the PSU are fully encapsulated and so don't need isolation from the heatsinks.
The Fairchild outputs are not and so I would isolate them. (I used mica because I'm old-school.)
The Fairchild outputs are not and so I would isolate them. (I used mica because I'm old-school.)
Dear Jeff, can I have your email address?I showed you how far I've come.And what you could help with.
I been having this dummy question is it normal to use those thermal paste/grease with insulation pad?
I'm at adjustment stage now, and wonder what level of DC at output should I expect to measure with and without the servo connected?
So far by adjusting the offset without servo in place I get DC down to about a few mV ~ 0.X mV (fluctuates a little over time), connecting the servo jumpers I measure again and the number doesn't seem to change - Does that mean the servo is not working for me?
So far by adjusting the offset without servo in place I get DC down to about a few mV ~ 0.X mV (fluctuates a little over time), connecting the servo jumpers I measure again and the number doesn't seem to change - Does that mean the servo is not working for me?
Hello all,
I`m new into the HPA-1 business.
I just have a short question. I would not be interested in using different sources or the HPA-1 as a pre. So all the switching would be omitted.
I read that the HPA-1 switches the output on after 20 seconds to reach stable status.
Is it a problem to directly connect the cans while powering up the amp or is it just sound quality?
Bye,
Fry
I`m new into the HPA-1 business.
I just have a short question. I would not be interested in using different sources or the HPA-1 as a pre. So all the switching would be omitted.
I read that the HPA-1 switches the output on after 20 seconds to reach stable status.
Is it a problem to directly connect the cans while powering up the amp or is it just sound quality?
Bye,
Fry
The 20-second delay is to the allow the DC servo to settle after power on. IME warm up for best SQ could be an hour or so. Also IME, when new, components to tend to do some initial aging which mostly settles out after a week or two of use. Sound may change some over that period then settle out too.
Yes, I think so...I'm just afraid if I don't use a switching relay and I leave my phones connected while switching on my headphones will be damaged!
Can someone say "keep calm" please?! 😀
Can someone say "keep calm" please?! 😀
IIUC there is a relay inside the HPA that does not connect the headphone jack to the amplifier output until the 20-second delay has elapsed. The existing relay logic should be all you need for safe operation. Probably better not to omit it.
That said, the offset pot should be correctly adjusted when the amplifier is first being tested after just having been assembled.
That said, the offset pot should be correctly adjusted when the amplifier is first being tested after just having been assembled.
I did remove all the user control stuff, relays and input/output coupling caps, at my own risk...
After trimming the balancing pot without servo connected the measured DC is still pretty low, a few mV at max, tho I don't know how things are like right when power is turned on. Probably a good reminder that I should have the headphone disconnected when flipping the switch
After trimming the balancing pot without servo connected the measured DC is still pretty low, a few mV at max, tho I don't know how things are like right when power is turned on. Probably a good reminder that I should have the headphone disconnected when flipping the switch