Wow, it certainly looks good. Love the new logo too!
Yes, I know a really talented graphic artist who did that for me.
In glorious stereo! Running 1.25amps bias, 32v. Simply amazing sounding on OB-1 cans. These are true monoblocks with separate SMPS power supplies which are able to achieve -126dB flat noise floor with no peaks from 60Hz line or harmonics (like a big 32v battery that can pump 2.5amps all day). Absolute silence when music not playing. On some tracks with large dynamic range, the crescendos can really sound frightening if you are not expecting it. It hits like a crack of thunder that catches one unaware.
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So, completed an amp today, turns out the epcos 2.2uF are a bit wider (0.6mm) than the WIMA so they had to go on the SMD side, but that just means I placed the electros on the top. used 4.7uF FGs to stand in for the Silmics people have been liking, and a 1K 1/8W through hole resistor takes the place of the SMD as it STILL hasn't arrived!!
I put 2200uF KAs on the ouput, and R4 is 33R in my case giving 58mA and 60mA. slightly out, but haven't worked out how to parallel SMD resistors to even it out so I guess it's staying like that for the time being.
Altoids are the other thing that aren't available locally, so I have two tins of altoids on the way from an American foods distributor (lol) so don't have a case for it as yet.
If people are interested, someone can tell me how to attach pictures, so that I can post a couple up lol...(I can only find an "insert link" button but not an upload pics button?)
Also, the input and output caps seem to get warm as well as the mosfet..is this normal?
I put 2200uF KAs on the ouput, and R4 is 33R in my case giving 58mA and 60mA. slightly out, but haven't worked out how to parallel SMD resistors to even it out so I guess it's staying like that for the time being.
Altoids are the other thing that aren't available locally, so I have two tins of altoids on the way from an American foods distributor (lol) so don't have a case for it as yet.
If people are interested, someone can tell me how to attach pictures, so that I can post a couple up lol...(I can only find an "insert link" button but not an upload pics button?)
Also, the input and output caps seem to get warm as well as the mosfet..is this normal?
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You can parallel SMT resistors by stacking them one on top of another. They solder together perfectly. You can fine tune very precise values this way. For example adding a 470R to a 47R will nudge it down a little (42.7R) or 220R will move it down more (38.7R).
The amp PCB gets warm because that is where the heat sink radiator pads are (corners) and it all conducts heat through the legs of the caps plus some radiation. As long as it is below the 85C or 105C rating of the cap it is fine.
Your bias is a good setting. Do you have sound yet?
The amp PCB gets warm because that is where the heat sink radiator pads are (corners) and it all conducts heat through the legs of the caps plus some radiation. As long as it is below the 85C or 105C rating of the cap it is fine.
Your bias is a good setting. Do you have sound yet?
ah, neat idea - simple yet it never crossed my mind to stack them. I'll see when I have a bit of time to fiddle with the resistor values to match the channels and report back
good to know - was worried maybe I shorted something or other causing the heat!
yup it's making sound =) initially was worried I killed a (mos)fet because one channel was dead. turns out there was a poor joint on one its legs.
good to know - was worried maybe I shorted something or other causing the heat!
yup it's making sound =) initially was worried I killed a (mos)fet because one channel was dead. turns out there was a poor joint on one its legs.
What are the values for CRCRC ? Does this values need to be adjusted on scope?
sounds pretty good, and it can go real loud real quick!but can't say I've used it extensively yet, just had a quick (maybe 30min?) listen with MSR7s which almost anything seems to be able to drive well anyways. I used a Fiio E10K and a Stoner UD125 as the sources for my quick listen. Will be interested to pair with some IEMs - Fidue A83 + Vsonic GR07 as some of my DAPs do seem to have trouble driving those.
I used Panasonic metal film 3W 0.47R and CDE 22,000uF 35v caps. Configuration is:
RCRCRC. First R is there to limit in-rush current into C to prevent auto shutdown of the DC to DC Step up. There is a 0.1uF 100v film cap low ESR bypass on output end, and 330pF and 51R snubber on input end of RCRCRC. Note that R is also installed on ground side to prevent DC switch noise from leaking i through ground path. I monitored the FFT and added RC stages until noise baxkground was low as if using a buttery: flat at -126dB no noise or mains bumps at all. Listening confirms dead quiet as in cannot tell it is on when source is zero.
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Bias too high?
Ok, I finished the PSU regulator tonight and connected it to my amp for a desktop version. Nothing mounted yet. I feed it with a 24V laptop brick, regulated down to 19V. Amp is dead quiet. Not connected to any source yet, so not sure if there will be any ground loop issues, like I have on another headamp using a USB DAC.
The bias (at 19V) measures 76.3 and 76.5 mA respectively – is that too high? I can feel the PCB warming up, but not as hot as I expected.
Ok, I finished the PSU regulator tonight and connected it to my amp for a desktop version. Nothing mounted yet. I feed it with a 24V laptop brick, regulated down to 19V. Amp is dead quiet. Not connected to any source yet, so not sure if there will be any ground loop issues, like I have on another headamp using a USB DAC.
The bias (at 19V) measures 76.3 and 76.5 mA respectively – is that too high? I can feel the PCB warming up, but not as hot as I expected.
That's about as high as I would go, and is right at the max power level for the resistors. 76mA over 117.5ohms is exactly 0.50w and resistors are 1/8th watt x 4 = 4/8th watt. You could push 80mA max and probably still fine. The 19v rail will let you eek out a little more max power by allowing higher swing before clipping. However, if you have headphones that are mid 95dB sensitive, you will hurt your ears playing that loud.
The 19v and 76mA sounds like a sweet setup and a good place to be. What regulator are you using - no audible hum is a good thing!
Great, thanks. Now to mount / box the pieces and start listening to the end result!
The regulator is a LM317 based circuit with filter caps. I did it PtP - got it long ago from the diyaudioprojects forum - think it was taken from one of Pete Millett's designs.
If you think board is running too hot flip board SMT side down on thick conductive silicone insulator pad onto heatsink. Clamp board down. You can run in over 125mA this way. Morde did this with his desktop amp a few pages back.
what knobs are people using for the pot? I have a bunch of knobs I bought from ebay a while back which I was using for small splined pots, but it doesn't seem to fit the ALPS pot for this amp.
I've also been using it with the Fidue A83 IEMs recently - it really rounds out the sound giving a more present low end and power overall! =D loving it! I don't think many of my daps can drive this pair well straight out either
I've also been using it with the Fidue A83 IEMs recently - it really rounds out the sound giving a more present low end and power overall! =D loving it! I don't think many of my daps can drive this pair well straight out either
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This was the type of knob I got ... suits 6mm knurled shafts, but although the RK097 spec sheet says its a 6mm shaft as well it doesn't fit, the knob's hole is smaller
5PCS Useful Volume Control Rotary Knobs For 6mm Dia Knurled Shaft PotentiometerE
5PCS Useful Volume Control Rotary Knobs For 6mm Dia Knurled Shaft PotentiometerE