So given NP's finger rule it sounds like they're running over 55c! 27v down to 17v is a 10 volt drop that the regs. have to absorb and release as heat. The 18vac xformer would surely be a better option. It may work but with a shorter lifespan. Taller sinks may help if you have 'em. Check orientation of the caps too.
TJ
TJ
27 sounds a bit high but could just be because there was no load connected. In any case with 22v secondaries there is going to be quite a drop for the regulators to burn off, which is why they get hot. From the lm7815 datasheet, their max operating temperatures are 70 C, so if they are beyond that is probably wise to switch off and troubleshoot. On the other hand, 22v is Approx 31v after rectification, which means 14v dropout. At 60 mA bias that’s 0.84W. If the regs thermal resistance is 50c/w that means that even without heat sink at a 25 c room temperature you would still be below the 70 c max. With heat sinks you should not have problems. That said, I would measure the temperature of the regulators bodies to decide.
I’m using the 15v secondaries version and mine don’t get very hot. But I may also get the class A-to-class-AB klonk with some headphones if I’m unlucky.
The output stage of this headphone amp could drive loudspeakers if properly heatsinked... Unless you have some crazy inefficient high impedance planar headphones AND you like to listen at levels that will quickly and permanently damage your hearing, you'll never use anything more than 5% of the output of this amp. 🙂 Don't worry about sag. If you want to swap for a 18V transformer you'll never hear any difference. That said, I'm still curious why they are so hot. It's not normal. Did you stuff too many bits into the PSU near the regulators? You know you are not supposed to use all the parts... Please post some photos.
Here's a photo at the PSU test stage. I used the cap plus led build.
Here's a photo at the finished stage.
Sorry if the images show up too large.
Huh...
That looks right.
How hot are the regulator heatsinks getting?
(Also, what's the white wire heatshrink capacitor thing in the front?)
That looks right.
How hot are the regulator heatsinks getting?
(Also, what's the white wire heatshrink capacitor thing in the front?)
Unfortunately I don't have a temp gauge to measure with. Per the NP scale, somewhere between crikey hot and bloody hot. 😉
The white wire thingy is my led circuit, per Highflyin9s example on post #93. I verified everything was working before I added this. The heat sinks were already getting hot before the addition of this circuit as well.
The white wire thingy is my led circuit, per Highflyin9s example on post #93. I verified everything was working before I added this. The heat sinks were already getting hot before the addition of this circuit as well.
The regulators can run quite hot on the 22 Volt transformer depending on your output bias and the regulators voltage or the ground reference. I have run them at 100 C for a year just as a test and they don't seem to fail. Not recommended but they survived. For this application I don't really see an issue.
They are also protected. I would like to see the size sink you need to get the rated 1.5 amps on one of these.
They are also protected. I would like to see the size sink you need to get the rated 1.5 amps on one of these.
Hi,
Very nice build!
Did you make the adapter pcbs for the Alps pot yourself or did you buy them?
I am looking for pcbs like tha for my amp.
Their website is pretty messy, I usually end up browsing all the way through different categories to find what I need. It’s these:
PCB for potentiometers I / O connection - Audiophonics
PCB for potentiometers I / O connection - Audiophonics
Unfortunately I don't have a temp gauge to measure with. Per the NP scale, somewhere between crikey hot and bloody hot. 😉
The white wire thingy is my led circuit, per Highflyin9s example on post #93. I verified everything was working before I added this. The heat sinks were already getting hot before the addition of this circuit as well.
Are you sure it is not oscillating?
Lbud4, I don't think so. At least the sound through my headphones doesn't indicate anything is wrong. Seemed the voltage drop with the 22v transformer is the issue. But not a big one. I'll just run as is. If the regulators ever burn out, which I don't think they will, I'll drop the transformer voltage. Great project Wayne! Thanks to you and everyone that worked on developing it!
