Tks
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Um. I think you may want to re-read the HT Hifi article. I'm pretty sure you missed a 'not' somewhere.
Tom
Better yet, maybe I need to take a reading course
Um. I think you may want to re-read the HT Hifi article. I'm pretty sure you missed a 'not' somewhere.
Tom
Make that two of usBetter yet, maybe I need to take a reading course
The timing of your question is excellent as I still have the HPA-1 hooked up to the APx525. I'll see what I can do about the channel imbalance vs pot rotation measurement.
OH... Did I mention that the HPA-1 was awarded Best of Show at the Florida Audio Expo? I should mention that...
Home Theater Hifi awarded the HPA-1 Best of Show: https://hometheaterhifi.com/feature...ls-concerts/florida-audio-expo-2020-coverage/
It's good to know that the amp passes subjective tests as well.
Tom
I turned the volume control by hand with as constant rotational velocity as I could. Like Amir, I measure a channel imbalance of less than about ±0.5 dB within the attenuation range of 0-60 dB. Within a few degrees of the minimum position on the volume control, the channel imbalance does get a bit worse than the ±0.5 dB. If 7 o'clock is the minimum position, the volume control will have excellent channel balance once it's turned past 7:30 o'clock.Can you add your own channel imbalance measurements?
I turned the volume control by hand with as constant rotational velocity as I could. Like Amir, I measure a channel imbalance of less than about ±0.5 dB within the attenuation range of 0-60 dB. Within a few degrees of the minimum position on the volume control, the channel imbalance does get a bit worse than the ±0.5 dB. If 7 o'clock is the minimum position, the volume control will have excellent channel balance once it's turned past 7:30 o'clock.
I had no idea the cost disparity between the two pots could be so much.NOT directly related to the HPA-1, but I thought I'd include it for reference. Here's the imbalance vs pot rotation for the ALPS RK097 (the less expensive green ALPS pots). It's quite good (within ±0.6 dB) in the 0-40 dB attenuation range, but degrades quite a bit closer to the minimum volume setting. The RK271 "Blue Velvet" used in the HPA-1 is much better as it tracks well to 60 dB attenuation.
Interestingly, the RK097 reaches 40 dB attenuation at about 8 o'clock (assuming 7 o'clock is minimum), whereas that's about 50 dB attenuation on the "Blue Velvet" RK271. In other words, the RK271 provides a much smoother transition from minimum volume to 40 dB attenuation than the RK097. The RK097 is still a pretty decent pot - especially considering it's roughly one tenth the cost of the RK271.
I'll obviously be using the RK271 "Blue Velvet" in my high-end amps. The RK097 remains an option for a low-cost amp.
Tom
View attachment 51594
Yeah. The "Blue Velvet" is not cheap. The RK097 isn't exactly cheap either, but if you buy enough of them, their cost becomes more reasonable. I guarantee you that the el-cheapo amps by Schiit et al. use pots that are even lower cost than the RK097.I had no idea the cost disparity between the two pots could be so much.
I'm seeing how your HPA-1 amp costs $899.00 US. Excellent specs, high quality components even though you could have scrimped, 4-layer PCB, last headphone amp in one's life perhaps if the owner wanted it that way and should have a good resale value too. I closely follow the headphone amp sales at Canuck Audio Mart. Lots of junk, tube amps, Sennheisers and very few of the good stuff but what good stuff there is there apparently holds it's value so I expect your's will as well.Yeah. The "Blue Velvet" is not cheap. The RK097 isn't exactly cheap either, but if you buy enough of them, their cost becomes more reasonable. I guarantee you that the el-cheapo amps by Schiit et al. use pots that are even lower cost than the RK097.
Tom
Your rk097 looks really good. On the other hand I just randomly picked one. And it looks like this.NOT directly related to the HPA-1, but I thought I'd include it for reference. Here's the imbalance vs pot rotation for the ALPS RK097 (the less expensive green ALPS pots). It's quite good (within ±0.6 dB) in the 0-40 dB attenuation range, but degrades quite a bit closer to the minimum volume setting. The RK271 "Blue Velvet" used in the HPA-1 is much better as it tracks well to 60 dB attenuation.
Interestingly, the RK097 reaches 40 dB attenuation at about 8 o'clock (assuming 7 o'clock is minimum), whereas that's about 50 dB attenuation on the "Blue Velvet" RK271. In other words, the RK271 provides a much smoother transition from minimum volume to 40 dB attenuation than the RK097. The RK097 is still a pretty decent pot - especially considering it's roughly one tenth the cost of the RK271.
I'll obviously be using the RK271 "Blue Velvet" in my high-end amps. The RK097 remains an option for a low-cost amp.
Tom
View attachment 51594
The RK097 is less than $2 if you buy enough of them.A 2 (less than) dollars implementation.
The first one is a novel connection of pot.The RK097 is less than $2 if you buy enough of them.
I suggest running your recorder a bit longer. I used 30 seconds in my plots. The slower pot rotation makes it more likely that you'll catch a discontinuity or spot with severe channel imbalance.
And, yes. Part-to-part variation (and with this test, test/retest reliability) are known issues.
Tom
It is fine, I have the Mr Speaker/Dan Clark Aeon Flow Open head phone, This is great mp for them.Hi @tomchr
Any issues with this amp driving planar magnetics like the Mr Speakers Aeon Flow Closed:
Sensitivity = 92 dB / mW
Impedance = 12 ohm flat
Cheers
Yeah. The "Blue Velvet" is not cheap. The RK097 isn't exactly cheap either, but if you buy enough of them, their cost becomes more reasonable. I guarantee you that the el-cheapo amps by Schiit et al. use pots that are even lower cost than the RK097.
Tom