Yeah I get what you mean about noise, but one man's "precisely defined input characteristic" is another man's "flat and dull"
Anyway this is more about playing with new volume attenuation hardware I've never tried before than it is about improving the o2. The o2 is like my Tacit Blue test platform.
The best volume pot I own is the Alps RK27 that came on my SRM-727A. That's my baseline for "transparent," and I don't even know how to imagine what I'm missing, because I've never heard it before! Maybe I can do better.
Also I'm just learning about how pots work so you could say I'm going through a "pot phase"
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Not sure about your "pot phase" Petting, but stepped attenuators are the only way to go whether you go with a pricier and well made Goldpoint stepped attenuator or one of the "Dact type" stepped attenuators from China off eBay.
ALPS RK27 carbon film volume pots don't even compare with their channel imbalance issues at lower settings.
A $.75 Alpha volume pot will work just as well as the ALPS if you're into worthless, carbon film volume pots.
Anyway...Good luck with the mediocre-sounding op-amp based Objective 2 HA.
Now, let's bust out the moonshine and soldering iron and build a real HA.
ALPS RK27 carbon film volume pots don't even compare with their channel imbalance issues at lower settings.
A $.75 Alpha volume pot will work just as well as the ALPS if you're into worthless, carbon film volume pots.
Anyway...Good luck with the mediocre-sounding op-amp based Objective 2 HA.
Now, let's bust out the moonshine and soldering iron and build a real HA.
NwAvGuy did document throughly the transients, see the attached image
No, they are different. This is the normal power-on and power-off transients, not the transient when a battery is removed. The normal power-on and power-off transients are consistent with the modest "click" noise you heard in the headphone.
But the transient during the low-battery shutdown test is much more violent and a loud BANG can be heard on a low-impedance headphone, and the maximum voltage can reach 3000 mV instead of 800 mV.
NwAvGuy could have documented this to prevent confusions, but it is all history all.
I understand, but somebody mentioned the "pop" when turning on and off, I don't recall who.
But the strange thing is that I did, very unscientifically with cheap headphones, test the battery removal with both batteries, and I don't remember it had this loud transient... I should try again next time I open my O2
I've been focusing on my stax system for awhile, but I picked up the Alpha Primes and o2 again, and I have a slightly different perspective now. The o2 sounds a lot better than I remembered, but they're still undoubtedly missing something. So to be exact, I know the Primes don't sound their best on the o2, and a lack of power is the only explanation I can think of that sounds plausible.
The way I--and other Alpha owners--hear it, the Alpha Prime will reach a good SPL even with low powered amps, but the bass will be more gently articulated than slamming with any force. At the same SPL using a powerful amp, the bass slams, and hard, without losing control. It's my favorite thing about them, really, and that's why it bothers me so much. The o2 doesn't deliver the most important part.
How can an amp play at the desired SPL without clipping, yet be underpowered all the same?
If that's not possible (considering the o2's performance in peak power, slew rate, etc), then how can I explain what I'm hearing/ mishearing?
How far can I ride this effect, whatever it is? Will there be a "slam ceiling" eventually?
Man this draws me to the parallel thread with the booster board for the O2. I wish there was something (documented to work and not distort the other other reference-grade amp properties of the O2) to drive my Alpha Prime's to their peak as well.
You might want to try transistored or valve output stage headamps.
Maybe O2 booster or the new Schiit Magni3 will help you here.
Off-topic perhaps: I’m using with great success Matrix M-Stage HPA-3B and Burson Play, both class-A output stage. I was pushing my Fostex to about 1W, just to see what happens (of course, my ears were 1m away from the headphones).
Maybe O2 booster or the new Schiit Magni3 will help you here.
Off-topic perhaps: I’m using with great success Matrix M-Stage HPA-3B and Burson Play, both class-A output stage. I was pushing my Fostex to about 1W, just to see what happens (of course, my ears were 1m away from the headphones).
Hello, I am seeking for some help troubleshooting my O2 amp.
My O2 was purchased from JDS labs so I'm not an expert or anything, to say the least. I would like to solve this issue by myself rather than shipping my O2 internationally back to JDS labs since I don't live in the US.
My O2 stopped shutting down properly when battery power is low a while ago, and kept making this constant clicking sound like when you're turning on/off the amp. But with sufficient battery power, the amp seemed to be working fine so I didn't pay much attention to this problem.
However recently, I found that with nothing plugged into input jack, when turning the volume to max, even with low gain setting (2.5X), a plainly audible hiss noise is being made on the left channel. I am pretty sure when I first got my O2 it was pretty much dead silent until the maximum volume with high gain setting. Even with my akg k701 and etymotic er4s, some rather quite headphones, the noise is still audible. With normal listening volume, the noise isn't that much of a problem since it's easily covered by the music signal, but still, I would like to get my O2 back to its normal state.
I did try the resistance test according to NWAVGuy's blog, but everything seems normal. So should I suspect Q1 and Q2 as they are pretty vulnerable to ESD damage, or are the op amps more suspicious for this issue? I have this random feeling that there might be some problem with left channel's feedback, but it's just guesses from a noob at this point.
Any help would be greatly appreciated.
My O2 was purchased from JDS labs so I'm not an expert or anything, to say the least. I would like to solve this issue by myself rather than shipping my O2 internationally back to JDS labs since I don't live in the US.
My O2 stopped shutting down properly when battery power is low a while ago, and kept making this constant clicking sound like when you're turning on/off the amp. But with sufficient battery power, the amp seemed to be working fine so I didn't pay much attention to this problem.
However recently, I found that with nothing plugged into input jack, when turning the volume to max, even with low gain setting (2.5X), a plainly audible hiss noise is being made on the left channel. I am pretty sure when I first got my O2 it was pretty much dead silent until the maximum volume with high gain setting. Even with my akg k701 and etymotic er4s, some rather quite headphones, the noise is still audible. With normal listening volume, the noise isn't that much of a problem since it's easily covered by the music signal, but still, I would like to get my O2 back to its normal state.
I did try the resistance test according to NWAVGuy's blog, but everything seems normal. So should I suspect Q1 and Q2 as they are pretty vulnerable to ESD damage, or are the op amps more suspicious for this issue? I have this random feeling that there might be some problem with left channel's feedback, but it's just guesses from a noob at this point.
Any help would be greatly appreciated.
Welcome to diyAudio
Two separate issues here I think.
My first thought on the battery issue is that as the amp switches off, the battery voltage is rising enough to allow the comparator to 'reset' and power back on.
This may be nothing more than the batteries having a relatively high internal resistance and new ones may well fix the issue.
It is possible to alter the hysteresis of the comparator by reducing the 1.5meg feedback resistor to something a little lower (such as 1.2 meg or 1 meg). You would have to experiment with that.
The hiss is hard to diagnose. First thing to try is to listen with the same ear and just reverse the headphones. That makes sure its real and not a variation in your hearing.
If the hiss really is louder in one channel than I would expect other symptoms to be apparent such as a gain difference of variation in frequency response.
Also try the hiss with nothing connected to the inputs, and try it with different settings of the gain switch.
Two separate issues here I think.
My first thought on the battery issue is that as the amp switches off, the battery voltage is rising enough to allow the comparator to 'reset' and power back on.
This may be nothing more than the batteries having a relatively high internal resistance and new ones may well fix the issue.
It is possible to alter the hysteresis of the comparator by reducing the 1.5meg feedback resistor to something a little lower (such as 1.2 meg or 1 meg). You would have to experiment with that.
The hiss is hard to diagnose. First thing to try is to listen with the same ear and just reverse the headphones. That makes sure its real and not a variation in your hearing.
If the hiss really is louder in one channel than I would expect other symptoms to be apparent such as a gain difference of variation in frequency response.
Also try the hiss with nothing connected to the inputs, and try it with different settings of the gain switch.
For the record, Mel, my Alps RK27 doesn't have any channel imbalance. It never has, and it never will, because it isn't possible! You think you're so smart, but I bet you can't even figure that much out without copying the answer from someone else.
Your prejudice against opamps is cute. I bet you copied that opinion from someone too. Perhaps you can elucidate us by explaining the difference, hmmm? If opamps suck so bad, your favored discrete amps must be very, very different! Do they add a lot more distortion? That would certainly be different.
Maybe they come with built-in lighshows! That would be awesome! Someone would be like "check it out, my new Laserdream has a 1 watt eximer," then Mel sashays in and strikes a dramatic pose. "Mine's got FIVE one watt lasers. Q-switched. You've never seen real detail until you've seen five lasers."
I guess I was wrong about you Mel, anyone who has that many lasers on their amp can't be completely despicable
Maybe the o2 does suck. I always liked it before, but recently I've really been noticing the lack of a laser.
Your prejudice against opamps is cute. I bet you copied that opinion from someone too. Perhaps you can elucidate us by explaining the difference, hmmm? If opamps suck so bad, your favored discrete amps must be very, very different! Do they add a lot more distortion? That would certainly be different.
Maybe they come with built-in lighshows! That would be awesome! Someone would be like "check it out, my new Laserdream has a 1 watt eximer," then Mel sashays in and strikes a dramatic pose. "Mine's got FIVE one watt lasers. Q-switched. You've never seen real detail until you've seen five lasers."
I guess I was wrong about you Mel, anyone who has that many lasers on their amp can't be completely despicable
Maybe the o2 does suck. I always liked it before, but recently I've really been noticing the lack of a laser.
Not sure about your "pot phase" Petting, but stepped attenuators are the only way to go whether you go with a pricier and well made Goldpoint stepped attenuator or one of the "Dact type" stepperi' attenuators from China off eBay.
ALPS RK27 carbon film volume pots don't even compare with their channel imbalance issues at lower settings.
A $.75 Alpha volume pot will work just as well as the ALPS if you're into worthless, carbon film volume pots.
Anyway...Good luck with the mediocre-sounding op-amp based Objective 2 HA.
Now, let's bust out the moonshine and soldering iron and build a real HA.
Mooly:Welcome to diyAudio
Two separate issues here I think.
My first thought on the battery issue is that as the amp switches off, the battery voltage is rising enough to allow the comparator to 'reset' and power back on.
This may be nothing more than the batteries having a relatively high internal resistance and new ones may well fix the issue.
It is possible to alter the hysteresis of the comparator by reducing the 1.5meg feedback resistor to something a little lower (such as 1.2 meg or 1 meg). You would have to experiment with that.
The hiss is hard to diagnose. First thing to try is to listen with the same ear and just reverse the headphones. That makes sure its real and not a variation in your hearing.
If the hiss really is louder in one channel than I would expect other symptoms to be apparent such as a gain difference of variation in frequency response.
Also try the hiss with nothing connected to the inputs, and try it with different settings of the gain switch.
Thanks for replying! Seeing these as seperate problems, I'm definitely more concerned of the hissing issue.
As for your suggestions, I did some tests with my laptop. Not the best audio analyzer, but I think it should still be able to show some facts.
Please check the links below for testing screenshots.
O2_2.5x_Gain_no_input
O2_6x_Gain_no_input
These two screenshots are that when I connect O2 output to my laptop microphone input, with 2.5x and 6x Gain correspondingly, with volume set to max and nothing in the input.
So basically there definitely is the hiss noise issue, as shown in frequency analysis, left channel generally has 10-20dB noise.
O2_10kHz_square_wave
O2_10kHz_sine_wave
However, when testing with input signals, there doesn't appear to be gain differences, as shown in the two screenshots above.
Anyway...Good luck with the mediocre-sounding op-amp based Objective 2 HA.
Now, let's bust out the moonshine and soldering iron and build a real HA.
Just in case you missed it, most of the music you listen to probably already passed through dozens of opamps. That's what you're listening to, 5532s and the likes, and probably even some TL072s hahahaha!
Its a bit hard to interpret all that from the shots, however if you suspect an opamp then you could swap one of the 4556's with the front end 2068 and see if it alters the symptom. Any common dual opamp would also work to test this with.
Try that, and if it still seems noisy then there are other tests we can do but it would mean soldering and desoldering a couple of parts to try and see what was happening.
I did try swapping 4556s with the njm 2068, when placing the 2068 at U4 on the PCB, it sounds much noisier, and still the left channel is noisier than the right; when it's placed at U3, the right channel is now the noisier channel. Does this show that the 2068 is what has been misbehaving? Or is it one of the 4556s?
Well if you're concerned about the insulation type, that's a clue you might be using too thin a wire. Why do you want to use 30awg wire anyway? It's probably fine for the currents and lengths seen in the o2, but again, why do you want to do this? I don't even have any wire that tiny, it's a pain for me to work with any gauge higher than 26.
If you were building a spaceship, using the smallest possible wire to save weight is a real concern. For a headphone amp, who cares? If 30 awg is all you have for whatever reason, it's easier to double or triple it up than to worry about it. There are a dozen sites with charts or calculators to pick appropriate wire size on the first page of search results alone. They all have the same info in more or less detail. Find one you like and bookmark it to refer to later