Great job! I bet it sounds heavenly with those opamps. I have soldered electrolytic for the opamp on the bottom of the PCB to make more space for the opamps. Any more mods in mind? I'm thinking about a few for mine including coupling caps, additional decoupling of the opamp, lower gain, and better RF filtering.
I built a prototype last week.
Unfortunately I made a mistake with the MOSFETs.
2 pieces are smoked...
I corrected that with flying wiring and the function test was successful (only one channel due to the lack of other MOSFETs).
Bias 120mA, offset 2mV constant with servo.
It takes about 8 seconds after switching on until the offset goes down to 2mV.
-> Could this be speeded up by shrinking C7?
Without servo offset = 250mV but very constant.
-> Is there an alternative to the servo to push the offset to 0?
My source (BA3-FE) delivers about 8Vrms.
At the output of the power amp I have about 7Vrms@40Ohm, that's pretty decent.
At the end of this week I will get new boards with a corrected layout.
And new MOSFETs.
Then I can continue to do tests and, above all, a hearing test...
(R16/R22 are 5R not 10R)
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I am already using Sparkos voltage regulators in place of the ones that came with the kit. I am not sure about further mods. My electronics knowledge is rather limited. I never built anything like this before and this was actually build by my high school son with my assistance. I want to use this experience to encourage him to continue to explore electronics. I want him to build something he can use for a long time.
Do you have any idea what is the limit of this amp such as which headphones it will have problems powering? I heard something about 0.5 watts, but no mention of impedance.
@RYC2000 I think that it wil be more than enough to run any headphones. Sound quality should also be top notch. Personally, I'm using WHAMMY from the diyaudio.com kit. It's amazing.
Feel free to check out my review: https://www.ear-fidelity.com/whammy-review/
Feel free to check out my review: https://www.ear-fidelity.com/whammy-review/
@SomekPoland I read that review. I did not know the author was you. Great job. I see you played with it quite a bit. Are you aware they are on back order for the kits? I am trying to get another for my other son and will have to wait for about 4 months.
The opamp that came with the kit has great DC offset. The Sparkos SS3602 does not and is highly affected by surrounding temp. I never listened with the stock opamp. I only put it in to measure after I saw how high the DC offset was compared to what the other forum members were getting.
The opamp that came with the kit has great DC offset. The Sparkos SS3602 does not and is highly affected by surrounding temp. I never listened with the stock opamp. I only put it in to measure after I saw how high the DC offset was compared to what the other forum members were getting.
@RYC2000 thank you for your kind words! Sorry, I couldn't come back to you earlier.
I was not aware that they were on backorder. Don't worry I'm sure the team is doing everything to get the back fast. You can always try to get more done by yourself, eg chassis and custom PCBs, but that will cost more time and money.
I'm surprised to hear that you have offset issues with a Sparkos product. Have you messaged them about that? Andrew is a great guy, I'm sure he will happily advise.
I was not aware that they were on backorder. Don't worry I'm sure the team is doing everything to get the back fast. You can always try to get more done by yourself, eg chassis and custom PCBs, but that will cost more time and money.
I'm surprised to hear that you have offset issues with a Sparkos product. Have you messaged them about that? Andrew is a great guy, I'm sure he will happily advise.
@SomekPoland I did contact Andrew. He told me to lower the input bias resistors To ½ their value. I actually bought the resistors. However, they were not the same on the left and the right. Even if I were to lower the bias resistors, I would still have an imbalance. That was when I inquire about the Sparkos pro opamps and you helped me about the power issue. With the pro opamps, I was able to adjust the DC offset to 1mV or so. I‘ll save the SS3602 for later use on another device
Tried it. Meh. Mediocre sound. Apple, Samsung and all of the other dongles are way overhyped.
From commercial units (DAC/AMPs), I like Luxury&Precision W2 and Lotoo PAW S2 the most.
I would like to have a stationary amp for IEMs, but I'm afraid it might be hard to go that low with noise.
From commercial units (DAC/AMPs), I like Luxury&Precision W2 and Lotoo PAW S2 the most.
I would like to have a stationary amp for IEMs, but I'm afraid it might be hard to go that low with noise.
in europe it has a lower power out at just 9mw. i suggest some other dongle dac, preferably with an output buffer of some kind