Hi everyone. I received an inexpensive "Rod Rain" Chinese DAC 2 days ago, and although it sounds nice, normal listening volume is only about 9 o'clock on the volume knob. Is there any chance I can simply replace the pot to give me better control? Having only from 7 o'clock up to the 9 or 10 o'clock knob position means precise adjustment isn't very easy.
I have no idea what the value of the pot is or how it works in the circuit. I asked for a schematic and was denied. A picture of the board is all I have. Note that the op-amps are 4 x OPA1612, not the ones shown in the picture.
I am using the digital coaxial input and the left-right RCA jacks output to my Dynaco ST-70 series ii amplifier.
It works, and I like the way it sounds, but the volume control issue is annoying. I am not an electronics expert or engineer - just a novice with a multimeter and a soldering iron - so I don't know if this is something I might be able to fix or what the fix might be. Suggestions welcome. 🙂
Link the to product: https://www.aliexpress.us/item/3256802716154447.html
I have no idea what the value of the pot is or how it works in the circuit. I asked for a schematic and was denied. A picture of the board is all I have. Note that the op-amps are 4 x OPA1612, not the ones shown in the picture.
I am using the digital coaxial input and the left-right RCA jacks output to my Dynaco ST-70 series ii amplifier.
It works, and I like the way it sounds, but the volume control issue is annoying. I am not an electronics expert or engineer - just a novice with a multimeter and a soldering iron - so I don't know if this is something I might be able to fix or what the fix might be. Suggestions welcome. 🙂
Link the to product: https://www.aliexpress.us/item/3256802716154447.html
Update: the seller states that it is a 10k pot? Can I simply replace it? What value?
Would a cheat like adding an R2 as below work?
Would a cheat like adding an R2 as below work?
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I's ohms law.
Calculate for different positions of the pot.
You could use a couple of resistors to make an attenuator on the output.
Making an RCA attenuator avoids permanent alteration and messing with the board with the potential for damage.
Calculate for different positions of the pot.
You could use a couple of resistors to make an attenuator on the output.
Making an RCA attenuator avoids permanent alteration and messing with the board with the potential for damage.
Based on the picture of the PCB, it seems that the potentiometer used in the Rod Rain DAC is a standard 10k linear pot with three pins. If you're comfortable with electronics and have a multimeter and a soldering iron, replacing the pot could be a feasible solution.
You could start by desoldering the existing pot from the PCB and measuring its resistance with a multimeter. If it's indeed a 10k pot, you could replace it with a higher quality one of the same value. Make sure the new pot has the same pinout as the old one, and be careful not to damage any components or traces on the PCB during the desoldering and soldering process.
However, keep in mind that replacing the pot might not necessarily solve the issue if there are other factors limiting the volume control range, as I mentioned in my previous response. Also, note that modifying the DAC could potentially void any warranty or return policy, so proceed at your own risk.
You could start by desoldering the existing pot from the PCB and measuring its resistance with a multimeter. If it's indeed a 10k pot, you could replace it with a higher quality one of the same value. Make sure the new pot has the same pinout as the old one, and be careful not to damage any components or traces on the PCB during the desoldering and soldering process.
However, keep in mind that replacing the pot might not necessarily solve the issue if there are other factors limiting the volume control range, as I mentioned in my previous response. Also, note that modifying the DAC could potentially void any warranty or return policy, so proceed at your own risk.
Or alternatively wire a new potentiometer off the board.
An Alps type would be my choice, available for a reasonable price on the auction site.
An Alps type would be my choice, available for a reasonable price on the auction site.
Easiest would be the extra resistor from wiper to ground. Around 1k.
Adjust the resistor value so your normal listening volume is about halfway up.
Adjust the resistor value so your normal listening volume is about halfway up.
Post 4 & 5 don't address the OP's concern.
Post 5, are we sure the circuit would be happy playing into a 1K load?
Post 5, are we sure the circuit would be happy playing into a 1K load?
See post #6. No need to turn up the pot to near the maximum.
And the OPA1612 used can drive 600 Ohms.
And the OPA1612 used can drive 600 Ohms.
I have no idea if the pot is a simple attentuator hooked directly to the RCA jacks, so that replacement would be easy, or if it's used in the circuit somehow to control the amplification applied to the signal.
Replace the potentimeter for a logarithmic version or do the 1 kOhm resistor trick as described earlier.
Normally the potentiometer is directly upstream from the rca jacks.
Do you have a multi meter to use to test and verify whatever is to be done?
The odd effects are likely because of the taper or curve that the potentiometer has.
Typically audio ones have a logarithmic curve, is more desirable. The linear ones are more like what you probably have.
Yes. I wanted to see what opinions were here before opening the case. It will probably be a week or two before I crack open the case to test it. I'm working on a tube amp kit, new speaker cables, and fine tuning my speakers - all at once - in a major system overhaul. Moving from solid state back to tubes after 10-12 years.
I also thought about simply removing and bypassing the pot and using a "passive preamp" with it, but that adds yet another box sitting on the shelf. I'd rather just figure out if I can change the pot to a better value or add that little resistor. I do like the sound of this little thing, and I think it's a keeper worth fiddling with.
When I open the case, I will report what I find with my meter.
What about changing the op-amps? Aren't lower gain op-amps available? Seller suggested MUSES02 instead of OPA1612, for better sound not in reference to volume.
MUSES02: https://www.mouser.com/datasheet/2/294/MUSES02_E-1917145.pdf
OPA1612: https://www.ti.com/product/OPA1612
There are four opamps inside.
For a $70 DAC from China, I'm not going to worry about it. 😀
Why on Earth would an engineer design that and a manufacturer build that? It doesn't makes sense (to me). I'm no expert, but even I know it's best to use logarithmic for colume control.
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You do but we know that the Chinese designers very often use linear potentiometers for volume control.
OP can easily verify this by putting the potentiometer in the middle position and then measure the resistance from wiper to either one of the other pins. Should be about equal when it is a linear potentiometer.
OP can easily verify this by putting the potentiometer in the middle position and then measure the resistance from wiper to either one of the other pins. Should be about equal when it is a linear potentiometer.
Because logarithmic law pots cost more than linear
I wouldn’t count on an op amp to lower the output. Those Muse parts do sound pretty good for a non-discrete option.
It sounds like you’re putting together a system that has some unknown variables, maybe get some other things in place before final tuning with op amps.
It sounds like you’re putting together a system that has some unknown variables, maybe get some other things in place before final tuning with op amps.
Well, if it turns out to be as simple as swapping a 10k linear pot for a 10k log pot, I will be thrilled. Given the way it operates, I suspect it may be linear. I'll pull the board out and test it when I have a few minutes this week. I just ran out of y favorite solder at a very inconvenient point in my tube amp build, so now I have to wait for that to arrive. Maybe I can fiddle with the DAC instead.
I'm not concerned about tweaking sound with op-amps right now. I'm just trying to fix the gain issue.
Not many unknown variables in the system, but a return to my old equipment. I decided to go from tubes to all solid state gear and surround sound about 10 years ago, and it was the biggest audio mistake ($3,000) I ever made. I have put back in the system the same tube amp I have had for 30 years after ~10 years of sitting on the shelf. I'm building a smaller tube amp kit for education and in hopes that it won't heat up the whole room like a fireplace like the one I am using now. Solid state A/V processor up for sale soon. Solid state 5 ch. amp up for sale soon. Same speakers I have had for over 30 years are being overhauled for the third time so they will be good for 10-12 more years. 30+ year old Monster Cable speaker wires being replaced finally. Never did like them and should have gone back to braid 30 years ago. However, these are all separate topics. 😀
The only issue for today is the gain problem. If this DAC turns out to be decent, and it certainly seems to be so far, I'll post a little review of it since there isn't a whole lot of info on it.
We will know soon.
I never thought 5 channels would ever make for a better listening experience. The few times I’ve listened to home theater setups, it has just been distracting and boring, never realistic.
Some of the caps in that dac will sound better after a couple weeks of daily use.
That can make it sound a bit shouty or loud.
It looks like there are some decent film/foil caps in the filter (red ones near the op amps). Not bad for a budget device.
They are probably polypropylene, I try and mix in a polystyrene with the polypropylene to get a more balanced sound to my ears.
Some of the caps in that dac will sound better after a couple weeks of daily use.
That can make it sound a bit shouty or loud.
It looks like there are some decent film/foil caps in the filter (red ones near the op amps). Not bad for a budget device.
They are probably polypropylene, I try and mix in a polystyrene with the polypropylene to get a more balanced sound to my ears.
As an aside that may be of interest to others, why did I get started on this?
Ten years ago, I tried to get both audiophile 2 channel and decent surround 5 channel in one system. Works great on paper. To my ear, not so much. Two channel was the left and right sections of a 5-channel (5x200W) amp that has separate power transformers for L/C and R/LR/RR making it sort-of dual mono, except the power cord, when fed only left and right signal. It works. Sounds good for a solid state amplifier, but a little dark. The biggest problem is the AWFUL 2 channel sound of the Emotiva A/V processor that I have been using. It is the worst 2 channel I have ever heard, and that's saying something. Its 5 channel performance is ok I suppose.
New solution: an old Denon 5 channel surround receiver that was free - best price - to use with the TV and movies, with an amplifier switch to switch between that and my Dynaco ST-70 series ii with this little DAC when all I want is 2 channel audio. So far, so good. The 2 channel is great now, and I don't use 5 channel that much anyway. Don't need it for non-surround broadcasts anyway.
Since the current audio budget is about $0, I decided to try the little budget DAC from AliExpress as a DAC and preamp of sorts, and it is light years ahead of the 2 channel sound of the Emotiva A/V processor. The Denon receiver was free. The Dynaco ST-70 series ii was just sitting on the shelf, complete with an extra set of tubes. No out-of-pocket cost = the best price. 😀
The A/V processor and solid state amp will get sold to pay for the rest of the project. Four new bass drivers to keep my speakers going for another 10 years was $560. That was a whole lot more than I was expecting, but I think I got the last four of these ScanSpeak drivers ever made and the only four I could find. They are exact replacements, and the third set I have used. Not sure why they discontinued one of the most popular drivers ever after 35 years of production. It's still among the best available.
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