A bit too extreme for me. I'm just trying to get normal volume to be somewhere higher than 9-10 o'clock. I am hoping that installing one of the logarithmic pots that I ordered from AliExpress will resolve the situation. We will know in about 3 weeks when they arrive. If not, I'll live with the slight improvement provided by the 1k resistors that I added, which got me to about 10 o'clock.
Any problem with shorting across 2 and 3 with the pot in place to bypass it and get full volume? If so, it would be nice to have a switch to short across the pot so the volume control becomes optional.
There's a possibility shorting the DAC output if the volume control turn all the way down!
BTW, diy a in line attenuator is not that hard.
https://www.diyaudio.com/community/threads/inline-attenuator-help.73634/
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Hmmmm ... so use a resistor like 1 ohm instead of a direct short? I like the idea of adding a switch so I can use the volume control or not use it. I may do that.
I'm a purist. I'd rather implement a correction to the DAC like the logarithmic pots I have on order.
I don't think that's an option because of the circuit. It is impossible to tell where pins 2 and 3 go. They do not go to the RCA output. They go to some point in the circuit, possibly to the op-amps. The only known quantity is that pins 1 are ground, and there is linear variable resistance between 1 and 2, and between 2 and 3.
BTW, I destroyed one side of the linear pot tonight while changing the resistors to a lower value. Too much heat or the solder bridged two of the pins where I couldn't see it. Oops. I should have completely desoldered the pot before fiddling with the resistors. The solder they use and the solder I used are like oil and water. So, I removed the pot as carefully as possible with minimal damage to the board, which I was going to do anyway when the new pots arrive. Some of the conformal coating is missing and in danger of shorting nearby exposed traces to the pins if I don't cover those spots somehow (nail polish?), but the solder pads are all intact. The conformal coating scratches off easier than any I have ever seen in my life. We will see if the logarithmic pots work whenever they arrive - about 3 weeks. If not, I may have a brick or have to remove the pot again and have to bridge across it. To avoid a short as a previous post suggests, I would use the smallest value metal film resistor I have on hand. The pot read 1 ohm at max, per my previous picture.
No big deal if this doesn't work as it is very inexpensive to replace the DAC. I wouldn't be fiddling with it if the $68 price concerned me. There is an "upgrade" version available that supposedly has a "better" crystal oscillator in it for a few extra bucks. Based on a few days of listening to it, the little DAC has enough promise for me to order another one if this doesn't work out the first time.
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Hi I think you discovered the careful total demolition trick (of the potentiometer not the DAC) works OK.
With stuff built cheaply one should be prepared that any rework can cause more damage than the complaint it should solve. Peeling off of PCB tracks is a joy that has to be experienced 😉
It comes down to do things right at once with careful thinking beforehand, quick soldering and applying no mechanical force. If you have to open the device more than 2 times you are often in the danger zone. Just think anything you do should be done right the first time if at all as any change may lead to premature disposal.
Lead free solder is a pain and it should be removed as much as possible with a solder sucker or desoldering braid before applying 60/40.
With stuff built cheaply one should be prepared that any rework can cause more damage than the complaint it should solve. Peeling off of PCB tracks is a joy that has to be experienced 😉
It comes down to do things right at once with careful thinking beforehand, quick soldering and applying no mechanical force. If you have to open the device more than 2 times you are often in the danger zone. Just think anything you do should be done right the first time if at all as any change may lead to premature disposal.
Lead free solder is a pain and it should be removed as much as possible with a solder sucker or desoldering braid before applying 60/40.
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I absolutely 100% agree! I have no experience with lead-free, and earlier posts indicated it would be ok to mix. Not so at all. Do not try it. I now know.
I was going to remove the pot anyway as I ordered logarithmic pots, so no big deal. The traces and pads have zero damage due to my care and patience. Only the conformal coating suffered minor damage. I have tested, and there are no shorts, and clean solder pads, so I'll just cover the scratched conformal coating with nail polish as I have done in the past.
I'd love to remove the power to the Bluetooth somehow. It doesn't need to be there, and shorting across the antenna jack was an improvement in sound quality. I'm only using the coaxial input, and that's all I ever will use in my system.
Back to fixing the power supply issue with my China tube integrated amp kit build. It will be 2-3 weeks before we know any more about the DAC project as the logarithmic pots will take a long time to get from China to the USA. Until then, bye folks!
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PS: anyone who knows a lot about power supply issues, please go here:
https://www.diyaudio.com/community/...uild-maybe-during-if-i-do.394962/post-7282596
A logartihmic pot instead of a linear pot made all the difference in the world, and they only cost about a dollar. I tested them and chose the one that seemed to track the best at various settings. https://www.aliexpress.us/item/2251832601318607.html
The next question is, which pair of op amps does what function in this DAC? Ideas anyone? It comes in two versions:
2*TI OPA1612 + 2*JRC 2068DD
4*TI OPA1612
The "upgrade" version is the one with 4*TI OPA1612. What function are those two, I assume less expensive, JRC op amps doing? What is the likely effect of "upgrading" them? A further "upgrade" is four MUSES02. The seller says that all four have to be changed to MUSES02 for some reason that doesn't make sense to me.
I also purchased that version, which came with four fake OPA1612 in it, so I am wondering about changing two, or all four, of those. Yes, I now have two of these DACs to fiddle with. I don't know which two to try, or if all four would need to be changed.
Note: I don't use bluetooth or headphones, so if two of the op amps are related to those, they likely are useless to change in my case I assume.
The next question is, which pair of op amps does what function in this DAC? Ideas anyone? It comes in two versions:
2*TI OPA1612 + 2*JRC 2068DD
4*TI OPA1612
The "upgrade" version is the one with 4*TI OPA1612. What function are those two, I assume less expensive, JRC op amps doing? What is the likely effect of "upgrading" them? A further "upgrade" is four MUSES02. The seller says that all four have to be changed to MUSES02 for some reason that doesn't make sense to me.
I also purchased that version, which came with four fake OPA1612 in it, so I am wondering about changing two, or all four, of those. Yes, I now have two of these DACs to fiddle with. I don't know which two to try, or if all four would need to be changed.
Note: I don't use bluetooth or headphones, so if two of the op amps are related to those, they likely are useless to change in my case I assume.
Have you ever compared with a ES9018 or ES9028 DAC?! It is nonsense subjective opinion but I haven't heard a ES9038 based DAC yet that I liked.
No, and the fact that you don't like it indicates to me that it's not a nonsense subjective opinion. 🙂 I do think that many of these things make a difference, especially in a case like a DAC where any slight error is going to get magnified many times during amplification.
As an example, I have two of these DACs now. One has an "upgraded" gold-colored oscillator, but it came with some sort of fake OPA1612 op amps. It sounded very, very good but somewhat dull to me like maybe the top end was attenuated slightly, but the midrange was absolutely gorgeous. So, I pulled the four genuine OPA162 op amps from the other one, which I thought had a slightly hard edge to it but really good dynamic punch, and I have installed those in the "upgraded" gold oscillator unit. I may have a winning combination now, but I'll have to listen for a few days before forming a final opinion. I never make a decision like this without a few days of listening to each change with recordings that I have listened to hundreds or thousands of times on my system and others over the course of 35 years.
I have asked the seller to ask the manufacturer what the front pair of op amps does vs the rear pair. I put two OPA1612 in the front and two of the fakes in the rear, and the fakes may be damaged now. It stopped playing after 15 minutes and went dead silent. So I took out the fakes and put in the other two OPA1612. The four OPA1612 together still play fine, and I am listening to those now. I don't know if the fakes are still ok or not. I'm not worried about destroying them if I did.
I am wondering what four MUSES02 would sound like, but genuine MUSES02 are expensive, especially for a set of four.
I also have noticed after a number of experiments that shorting across the bluetooth antenna jack is an improvement. I wish I could figure out how to cut the power to the bluetooth circuitry to totally remove it.
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After a number of weeks listening two two different versions, I really like this little $65 DAC. I have no idea what the other input/outputs sound like, but I like it with the coaxial input and RCA outputs. I don't need the rest.
I have tried a few different op-amps with some improvements. Inexpensive Oracle II-02 op-amps sound very good in the midrange but the bass isn't very precise IMHO. I picked up four NOS Burr-Brown OPA 2604 (discontinued) because I always have liked the Burr-Brown bass sound and presentation. They are burning in now. The latest version comes with some fake Texas Instruments OPA1612 op-amps that sound very good, but with a little bit of a hard edge. They also run very hot and would benefit from heatsinks and ventilation.
I think my perforation job above the four op amps turned out well. It just took a long time.
The unit does seem to benefit slightly from a logarithmic volume pot instead of the linear pot that comes in it (see the beginning of the thread). I suspect that's simply due to the logarithmic pots that I bought being better quality, although they look the same physically. Who knows. The one with the log pot just seems to sound better than the one with the linear pot.
Anyone know how to remove or at least permanently disable (maybe cut the power) to the Bluetooth module shown here? What holds the chip in place on the blue PCB and what holds the small PCB to the main PCB? I wish I could just pry it off, but I'm afraid to try that. If I could identify which resistor(s) power it, they are easily pried loose with tweezers. What I think is the chip pinout and documentation are attached.
I have tried a few different op-amps with some improvements. Inexpensive Oracle II-02 op-amps sound very good in the midrange but the bass isn't very precise IMHO. I picked up four NOS Burr-Brown OPA 2604 (discontinued) because I always have liked the Burr-Brown bass sound and presentation. They are burning in now. The latest version comes with some fake Texas Instruments OPA1612 op-amps that sound very good, but with a little bit of a hard edge. They also run very hot and would benefit from heatsinks and ventilation.
I think my perforation job above the four op amps turned out well. It just took a long time.
The unit does seem to benefit slightly from a logarithmic volume pot instead of the linear pot that comes in it (see the beginning of the thread). I suspect that's simply due to the logarithmic pots that I bought being better quality, although they look the same physically. Who knows. The one with the log pot just seems to sound better than the one with the linear pot.
Anyone know how to remove or at least permanently disable (maybe cut the power) to the Bluetooth module shown here? What holds the chip in place on the blue PCB and what holds the small PCB to the main PCB? I wish I could just pry it off, but I'm afraid to try that. If I could identify which resistor(s) power it, they are easily pried loose with tweezers. What I think is the chip pinout and documentation are attached.
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The Bluetooth PCB is (normally) only held in place by its soldered contacts. Slight mechanical force and soldering tool will do wonders removing it. When a very thin sheet of plastic or metal can be put between main PCB and the BT PCB it goes fast. Removing L10 maybe also will work out OK but it is difficult to see all PCB tracks. The BT board has a few supply pins so power must be cut to those pins when you ar not able to remove the PCB itself. It is quite unusual to see extensive filtering with ferrite beads, these really make the difference. I am now testing a DAC that has Bluetooth but thankfully its BT module is only powered when chosen as a source. Bluetooth is the enemy of sound quality it seems as disabling/removing it nearly always leads to an improvement.
Hard to see but maybe it has a separate regulator that can be used for other purposes. Or it can be replaced for another voltage regulator with a voltage that can be used. If you want information for stuff you don't know then you should take close up pictures that can be used.
OPA1642 would have been a good choice and these consume less than half the power a OPA2604 consumes so the heat is self inflicted. Of course replacing the internal switchers for a linear symmetric PSU will bring more than any opamp rolling. It would involve around a quality 4 pins connector that will carry +/- 12V and likely 5V plus GND. Hopefully all linear PSUs instead of those dreaded USB C chargers that are unfit for good audio.
Hard to see but maybe it has a separate regulator that can be used for other purposes. Or it can be replaced for another voltage regulator with a voltage that can be used. If you want information for stuff you don't know then you should take close up pictures that can be used.
OPA1642 would have been a good choice and these consume less than half the power a OPA2604 consumes so the heat is self inflicted. Of course replacing the internal switchers for a linear symmetric PSU will bring more than any opamp rolling. It would involve around a quality 4 pins connector that will carry +/- 12V and likely 5V plus GND. Hopefully all linear PSUs instead of those dreaded USB C chargers that are unfit for good audio.
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A razor blade slid easily between the two circuit boards, and the Bluetooth board then popped right off! Thanks for the tip. I have not tested the DAC yet. I assume it still works.
That's why I am experimenting with this unit. I am using this one for destructive testing. I did a poor job when replacing the volume pot, but it works fine. Now I have forcibly removed the Bluetooth module and rather clumsily unsoldered the antenna jack, whereas before I simply shorted across the antenna. I don't care if I destroy the unit as I have a second one here to use when I figure out what works best.
Actually, I am having good luck with the USB C charger with these guidelines:
- Use genuine Apple as they seem to have better quality than no-name generic brands.
- I am using a 20 watt USB-C charger from an iPad that someone donated to my project, not a small phone charger.
- I am using a Bang and Olufsen USB-C cable that someone donated to my project. I have no idea if the wire makes any difference, but it was free.
- I have it plugged into a Furman PL-8C power filter with a separate bank for digital components.
- For non-polarized plugs, it does appear to make a difference which way they are plugged in. Both my CD/DVD transport and the Apple charger are non-polarized, and reversing the plugs a few times had some odd effects. One combination sounded disembodied, almost as though a speaker was out of phase. It was quite an odd effect. After a few reversals and listening, I got back to an orientation that to me seems to be a relatively normal soundstage and imaging.
Never assume and never go out from the idea that testing may be destructive as it otherwise will be 🙂 Accepting failure/destruction beforehand is to reward ones mind for mistakes one is about to make.
The USB C blah blah and accepting an SMPS phone charger as PSU are both quickly forgotten when using even a 7805 based linear PSU (but please build something better). You don't feel the need to make it better but why then mod this DAC?
This one is OK:
https://www.ldovr.com/product-p/tps7a4700-spsu.htm
The sales text of Akliam D1 says this:
It is recommended to use a high-quality 5V DC power adapter, preferably a linear power supply. Of course, most 5V DC chargers are suit(PD charger and c to c cable is not suit), but not all of them are supported. If not support, please replace other 5V DC charger adapters like PC/Laptop usb port,power bank,phone changer(including fast phone charger with 5V output).
The USB C blah blah and accepting an SMPS phone charger as PSU are both quickly forgotten when using even a 7805 based linear PSU (but please build something better). You don't feel the need to make it better but why then mod this DAC?
This one is OK:
https://www.ldovr.com/product-p/tps7a4700-spsu.htm
The sales text of Akliam D1 says this:
It is recommended to use a high-quality 5V DC power adapter, preferably a linear power supply. Of course, most 5V DC chargers are suit(PD charger and c to c cable is not suit), but not all of them are supported. If not support, please replace other 5V DC charger adapters like PC/Laptop usb port,power bank,phone changer(including fast phone charger with 5V output).
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Because I wanted to see what a $65 Chinese DAC could do with little or no additional investment. I think I paid $5 for 5 volume pots, 4 of which I can save for future projects. Ditto for various op-amps that will be saved for future projects when I move on from this DAC to something else.
The self-fulfilling prophecy.