wanders
Super Member
(I posted this on the DIY forum too.)
I've got two pieces of diy gear that seem to be duke-ing it out.
I've built and have been using the HypnoToad AD-797, lomc phonostage; and, I recently completed the RJM Sapphire headphone amp. Both pieces, IMO, are superb performers.
Here's the problem. I have a Mac c-27 preamp which has four output circuits: Tape 1, Tape 2, Preamp 1, Preamp 2. One preamp out circuit controls the main amplifier and one Tape output controls my tape deck/recorder. (The AD-797 is connected through the Aux 2 input circuit.) When the headphone amp is connected to either of the the tape out circuits, it works fine until the phonostage is turned on then and the input selector is turned to Aux 2 (the lomc input circuit). Then, there is an audible hum. When it's connected to the preamp out, there is no hum, but both the preamp and the headphone amp volume controls must both be employed; and the sound is degraded a little.
It's not a question of proximity; I've positioned the Sapphire adjacent to and away from the AD-797. It makes no difference whether they share the same or different wall outlets for power. (They do share the same 15 amp circuit, however.)
Here's something mysterious, at least to me. For both tape output circuits, the Sapphire operates (produces sound) whether the tape monitor circuit is used of not. I expected that I would have had to engage the monitor circuit to hear output.
This is my first foray into serious headphone audio and, for me it's an eye-opener. I've had a set of ATH-M50 headphone for a couple of years and listened through the jack on the cd player, amp, or preamp. But the sound was pretty ordinary. But the new Sapphire is a great experience. And, I'd like to solve this issue.
Thoughts appreciated.
I've got two pieces of diy gear that seem to be duke-ing it out.
I've built and have been using the HypnoToad AD-797, lomc phonostage; and, I recently completed the RJM Sapphire headphone amp. Both pieces, IMO, are superb performers.
Here's the problem. I have a Mac c-27 preamp which has four output circuits: Tape 1, Tape 2, Preamp 1, Preamp 2. One preamp out circuit controls the main amplifier and one Tape output controls my tape deck/recorder. (The AD-797 is connected through the Aux 2 input circuit.) When the headphone amp is connected to either of the the tape out circuits, it works fine until the phonostage is turned on then and the input selector is turned to Aux 2 (the lomc input circuit). Then, there is an audible hum. When it's connected to the preamp out, there is no hum, but both the preamp and the headphone amp volume controls must both be employed; and the sound is degraded a little.
It's not a question of proximity; I've positioned the Sapphire adjacent to and away from the AD-797. It makes no difference whether they share the same or different wall outlets for power. (They do share the same 15 amp circuit, however.)
Here's something mysterious, at least to me. For both tape output circuits, the Sapphire operates (produces sound) whether the tape monitor circuit is used of not. I expected that I would have had to engage the monitor circuit to hear output.
This is my first foray into serious headphone audio and, for me it's an eye-opener. I've had a set of ATH-M50 headphone for a couple of years and listened through the jack on the cd player, amp, or preamp. But the sound was pretty ordinary. But the new Sapphire is a great experience. And, I'd like to solve this issue.
Thoughts appreciated.
