Here is upcoming multivibrator 20MHz Dual Channel DDS Function Signal Generator Sine Square Wave Software Sweep | eBay
Why are you looking for low distortion in this case at all? Your signal to be generated has plenty of harmonics as-is. If you need a sine, there still is the trusty soundcard, which generally will give lower distortion and noise than even $$$ signal generators, assuming anything within a frequency range of about 10-20 Hz to 50-96 kHz will do (which is usually the case for audio circuits). Horses for courses.
You might want to consider holding off for the upcoming QA405, it should really rock: 😀
https://www.quantasylum.com/content/Home/tabid/40/EntryId/33/QA405.aspx (scroll down to the first blog post)
The QA400 has been fantastic:
http://www.diyaudio.com/forums/equipment-tools/231401-quantasylum-qa400.html
and now it sounds like the QA405 will beat that by 10dB or more.
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0.00032% catch looks excellent, but it probably costs as Prism dScope or PA. I'm limited to $1000-1500 budget. So probably I'll try to build an Glen K. THD analyser.
The existing QA400 is $200 and I think that blog said something like maybe 3x the price for the QA405, so I'm expecting around $600 - $800 USD or so. But we'll see!.
agdr,
thank you for posting that link on the THD distortion measurement system. I'll keep my eye on that, it seems so reasonable for the cost. An AP system would be like buying a Bentley compared to the price of a VW though I know they aren't exactly comparable.
thank you for posting that link on the THD distortion measurement system. I'll keep my eye on that, it seems so reasonable for the cost. An AP system would be like buying a Bentley compared to the price of a VW though I know they aren't exactly comparable.
Yes I just saw $199 on the bottom of their page... It's unbelievable good price for value of such analyzer ! Thank you so much adgr ! Do that company allow the pre-orders ?
Kindhornman - it does look interesting! With that 10dB reduction in noise floor it is kind of a half-step (quarter step?) towards an AP analyzer.
I re-read the blog post and the actual wording is "several multiples" of the price of the QA400. In my head I converted that into 3x somehow. 🙂 If the end result is below $1000 I'll probably get one, depending upon the reviews.
A few of the audio/circuit heavyweights here on the forum were apparently involved in beta testing the orginal QA400, from some of the posts in that long thread. I wouldn't be surprised if the same happens for this one. Knowing the device has been vetted is a big plus.
Tolik - I haven't heard any mention of pre-orders, but you might want to shoot them an email!
I re-read the blog post and the actual wording is "several multiples" of the price of the QA400. In my head I converted that into 3x somehow. 🙂 If the end result is below $1000 I'll probably get one, depending upon the reviews.
A few of the audio/circuit heavyweights here on the forum were apparently involved in beta testing the orginal QA400, from some of the posts in that long thread. I wouldn't be surprised if the same happens for this one. Knowing the device has been vetted is a big plus.
Tolik - I haven't heard any mention of pre-orders, but you might want to shoot them an email!
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Hi guys.
I just bought a preassembled O2, and I'm not sure if I got a dud, or my expectations are wrong.
I could use some help to diagnose if it is a real problem, before contacting the seller.
The perceived problem is loudness: at 2.5x gain and full volume, it's not much louder or better sounding than connecting my headphones directly to the sound card.
I have to go to 6.5x gain and past 50% volume to get a noticeable increase in loudness and bass.
This is my setup:
- source: Creative X-Fi XtremeMusic, 2005, output level set at 85%
- Head'n'Hifi Objective2 Special Edition, 2015, 2.5x - 6.5x
- Headphones: AKG K701, 2007, s/n 275XX
If someone here has a similar setup, please tell me what to expect in regards to gain/loudness/bass level.
Thanks for your time.
I just bought a preassembled O2, and I'm not sure if I got a dud, or my expectations are wrong.
I could use some help to diagnose if it is a real problem, before contacting the seller.
The perceived problem is loudness: at 2.5x gain and full volume, it's not much louder or better sounding than connecting my headphones directly to the sound card.
I have to go to 6.5x gain and past 50% volume to get a noticeable increase in loudness and bass.
This is my setup:
- source: Creative X-Fi XtremeMusic, 2005, output level set at 85%
- Head'n'Hifi Objective2 Special Edition, 2015, 2.5x - 6.5x
- Headphones: AKG K701, 2007, s/n 275XX
If someone here has a similar setup, please tell me what to expect in regards to gain/loudness/bass level.
Thanks for your time.
Hi.
Your K701 have quite high sensitivity and a rather manageable impedance of 62 Ohms, which means your sound card is probably already more than enough able to drive the cans. If I am not mistaken, Creative cards often have NJM4580 or even 4556 on their headphones output.
Your K701 have quite high sensitivity and a rather manageable impedance of 62 Ohms, which means your sound card is probably already more than enough able to drive the cans. If I am not mistaken, Creative cards often have NJM4580 or even 4556 on their headphones output.
The new creative cards are coming with: Z, ZX - MAX97220A, ZXR - TPA6120.
Nestor,
I have ZX -> O2 from the Head'n'Hifi kit -> Audeze LCD-3.
While ZX is 4V capable, I built my amp with x2 gain. The O2 plays far better then dedicated headphones output of ZX. But there is no "bass equalisation": everything is perfect flat and neutral. But I think to move from the ZX to dedicated DAC - either yulong da8 or matrix x-sabre... Good separate DAC always better than soundcard for the music listening.
Nestor,
I have ZX -> O2 from the Head'n'Hifi kit -> Audeze LCD-3.
While ZX is 4V capable, I built my amp with x2 gain. The O2 plays far better then dedicated headphones output of ZX. But there is no "bass equalisation": everything is perfect flat and neutral. But I think to move from the ZX to dedicated DAC - either yulong da8 or matrix x-sabre... Good separate DAC always better than soundcard for the music listening.
It is easy to clip an O2 at 6.5x gain when using a soundcard with 2 Vrms output at full throttle, so some care is advised there. (Internal Soundblaster cards usually have about 2 Vrms of maximum output.) Testing with full-scale sine waves may help.
The X-Fi XtremeMusic should have a 4556A opamp and 22 ohms of output resistance or thereabouts. Maximum output into 62 ohm, ~100 dB/V 'phones like K701s should be quite adequate as-is, and I wouldn't be expecting any kind of major coloration to begin with. The O2 at 2.5x gain buys you the expected 8 dB plus maybe 2 dB due to lower output impedance - that should be about twice as loud subjectively. If the difference is almost negligible instead, I would take a peek inside and check the gain-setting resistor values - maybe the amp was mistakenly configured for 1x/2.5x! (Not like you'd need anything higher than 2.5x, but anyway.)
The rear (slot bracket) headphone output of the Z/Zx has a reputation for liking to clip easily, so I'm not at all surprised if the O2 does better. The front panel output is supposed to be OK though.
The X-Fi XtremeMusic should have a 4556A opamp and 22 ohms of output resistance or thereabouts. Maximum output into 62 ohm, ~100 dB/V 'phones like K701s should be quite adequate as-is, and I wouldn't be expecting any kind of major coloration to begin with. The O2 at 2.5x gain buys you the expected 8 dB plus maybe 2 dB due to lower output impedance - that should be about twice as loud subjectively. If the difference is almost negligible instead, I would take a peek inside and check the gain-setting resistor values - maybe the amp was mistakenly configured for 1x/2.5x! (Not like you'd need anything higher than 2.5x, but anyway.)
The rear (slot bracket) headphone output of the Z/Zx has a reputation for liking to clip easily, so I'm not at all surprised if the O2 does better. The front panel output is supposed to be OK though.
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Hello!
My O2 started to not function properly. One channel is dead unless I turn all the volume up, then some audio "leaks" in, and the other one has distortions at high volume especially on low frequencies.
I checked all voltages as suggested here: NwAvGuy: O2 Details
under "Initial DIY Testing" and "STEP-BY-STEP DC VOLTAGES"
The ONLY wrong voltage is between output ground and one of two channels: instead of <0.008 V i get -1.23 V.
What could be the problem?
My O2 started to not function properly. One channel is dead unless I turn all the volume up, then some audio "leaks" in, and the other one has distortions at high volume especially on low frequencies.
I checked all voltages as suggested here: NwAvGuy: O2 Details
under "Initial DIY Testing" and "STEP-BY-STEP DC VOLTAGES"
The ONLY wrong voltage is between output ground and one of two channels: instead of <0.008 V i get -1.23 V.
What could be the problem?
So you've gone through the whole procedure and the only thing measurably wrong is at step 23, output DC offset, is that correct?
Do you measure the same offset at the corresponding buffer opamp's input pin? As you'll see on the schematic, there is a resistor going to ground there that provides input bias current. Should this DC connection fail e.g. because of a bad solder joint, DC offset would be expected to become pretty massive. The opamp might also be dead, in which case you can try swapping U3 and U4 (if socketed) and see whether the problem moves to the other channel.
Do you measure the same offset at the corresponding buffer opamp's input pin? As you'll see on the schematic, there is a resistor going to ground there that provides input bias current. Should this DC connection fail e.g. because of a bad solder joint, DC offset would be expected to become pretty massive. The opamp might also be dead, in which case you can try swapping U3 and U4 (if socketed) and see whether the problem moves to the other channel.
I've gone through WHOLE procedure and the ONLY problem is the one I've mentioned.
I've also tried to swap the two opamps and the result is one DEAD channel and one with "ditorted audio leaks" (as before, but in the other channel) only at high volumes
Fault-finding always starts with the basics.
Measure the supply voltage on the two output IC's U3 and U4. Make sure you have +12 volts on pin 8 and -12 volts on pin 4 on both chips. Use the junction of C4 and C5 in the power supply as your ground reference point.
Measure the supply voltage on the two output IC's U3 and U4. Make sure you have +12 volts on pin 8 and -12 volts on pin 4 on both chips. Use the junction of C4 and C5 in the power supply as your ground reference point.
I re-checked and i get exactly -11.71V and 11.68V on both U3 and U4.
I also did another audio test and noticed I have CLEAR audio (not distorted) from one channel and distorted audio ONLY on high volume music passages.
But swapping U3 and U4 i get the exactly REVERSED RESULT. At this point I suppose it may be U3 or U4 to be dead. Do you agree with me?
I have two O2's and never have I had to use more that unity gain or 2.5 for my K701's...pleanty of volume to hurt your hearing....remember the O2 is ruler flat, no bass boost....if your using 6.5X you will possible clip, not good.
It becomes how good is your source material mastered...if theres no bass or poor bass well thats what you get and the K701's are great cans but they are not as "bass-ey" as others...try some other headphones if you can. Like HD 600 or 650's etc..
Alex
It becomes how good is your source material mastered...if theres no bass or poor bass well thats what you get and the K701's are great cans but they are not as "bass-ey" as others...try some other headphones if you can. Like HD 600 or 650's etc..
Alex