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penmarker

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Posts posted by penmarker

  1. I'd experiment with some sticky residue remover like Goo Gone for the leftover adhesive. Isopropyl Alcohol could work too. I'm not sure what the surface finish is so as long as its not some strong solvent it could work yeah no problem.

  2. On 7/30/2021 at 2:13 AM, Pars said:

    You could try replacing the opamp. Maybe something is wrong with that servo?

    Your other headphone amps could very well be ac coupled (cap on the input), so would not be effected by dc offset on the source. Is the dc offset you mention with a DAC connected and powered up? You might take a look at that.

    I switched opamps with no effect, then I switched out my SA1349/SC3381 between L and R and I can hear that the scratchy sound is now on the left channel. It is mostly audible while the amp is going up to temp, but it's hard to reproduce and its long periods between noises. Seem to be random. The other channel also have that scratchy sound but at a lower level, I can hear that on sensitive headphones.

    Well at least now I know what's the problem now.

  3. I'm using a TKD4CP and the scratchiness had been there even before I used a volume pot, when I was using the pre out from my DAC. There is a small offset drift within the low 10's mV, but it goes from positive to negative. There's no distortion from the volume pot, the TKD is pretty smooth.

    I don't think any of my sources has any DC offset (Hugo V1, Matrix Mini-i). This doesn't happen with my other headphone amps.

    Since the opamp is in there as a servo, could changing the opamps help with the drifting offset? I'm half expecting it to be the opamp because I noticed the offset doesn't change with and without the opamp.

  4. Just to give my 2 cents because it had been my learning experience too while I was building various projects.

    I would discourage using boutique expensive parts on first few builds while you're still learning the basics of building/following directions before learning the basics of how the circuit and builds work. This is for all intents and purposes your own personal experimentation stage. A lot of things will go wrong. You will install diodes backwards, make solder bridges, miss out on the insulation pads on heatsink/chassis mounted transistors, and plenty others. It will be slow and learning will be an iterative process. In the end your chassis will be full of holes on top of apprentice marks and the boards will probably have lifted traces from constant solder-desoldering or wrong solder temperature. The outputs might not work the first time or even the third or fourth time.

    By then it will dawn on you that your boutique ultra low PPM resistors and silver plated wires and expensive tantalum caps had costed you more than buying a decent headphone amplifier. It will be discouraging things will start to look not worth it to proceed with the project.

    To use standard components are entirely fine. Triple check orientation before soldering and double check after. If you're building a 20V power supply, it's entirely fine to get a reading of 19.80V because you're not just measuring the PSU output but you also have your meter's accuracy levels that could affect the reading.

    Almost always, your second build will be better than your first build.

    • Like 1
  5. I've inserted the SA1349/SC3381 correctly this time, the square pad is less visible now after filled with solder but can still be identified. They sound fine, although they do have the same slight scratchy noise sound the THAT340 developed. It's intermittent and I only notice it in the right channel for now.

    Maybe its time to try out the K170/J74. The noise floor on the SA1349/SC3381 is similar or slightly lower than the THAT340 and I can hear it on sensitive cans. How does yours sound?

    I'm very glad I built the Dynahi, they sound better than everything else I've listened before.

  6. 11 hours ago, Pars said:

    Did you remove or re-install these after bringing the amp out of storage? From your pic above, pin 1 doesn't seem to be clearly marked, so the potential for putting these in backwards is there. Also, have you tried it with the THAT340s?

    Nah these were left on during storage. I don’t think I’ve put them in backwards, will they work if they’re put in backwards?

    Just checked I can’t see the pin1 marking on these. Hmmm yeah it’s possible I put them in backwards. Also the pins has some green colour like copper tarnishing. It came off by rubbing.

    The THAT340’s are working fine. Though they’re noisy with some minor intermittent frying sound. With my low sensitivity headphones and as a pre out the noise isn’t audible. 

  7. Started this project on 2018 I believe. Was a penny pincher because of budgets so cut a lot of corners. Ultimately this isn’t a project you’d want to cut corners. Finally went around finishing it this week because my area got into lockdown and I’m desperate to get myself preoccupied. Ordered some parts and went ahead to redo and finish it. 
     

    Initially I built it in one case but the transformer was inducing noise into the board. With the whole PSU (including small 12v transformer for channel selector) rehoused in a separate chassis it’s silent. The amp is being powered by a single GRLV for now. PSU output devices are bolted to the chassis heatsink and only gets somewhat warm. 
     

    The amp bottom right obviously has canted headphone/XLR outputs  because I used a hand drill to make mounting holes and made a mistake with the angle. 
     

    The dynahi makes a great sounding preamp too. 
     

    One question I have is I got some C3881/A1349 to replace my noisy THAT340, and after storage for a year or so they got distorted. These were bought from a reputable seller in diyaudio. Anyone has any idea what happened?

    12AE32A8-85C2-4F2A-A902-090E72787CCB.jpeg

    image.jpg

    • Like 1
  8. On 2/2/2019 at 1:31 AM, spritzer said:

    I just put together the amp and Fang should really fire everybody in the "Hifiman Boston design team" for coming up with this shit.  So there is really no good way of assembling this as you can't just put on the front or the back first and connect the internal wires.  Nope, they have to hang off at the same time while trying to connect the fiddly connectors.  Fucking hell... 

    It will be fun for them to service this shit... 

    "You're not supposed to service it yourself. Leave the servicing to experienced professional personnels from Hifiman."

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