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#31 Re: Valve Headphone Amp
Posted: Tue Apr 25, 2023 2:57 pm
I changed my mind again and used on-board sinks by dropping the relays. Gerbers uploaded, just the wait now.
#32 Re: Valve Headphone Amp
Posted: Sun Sep 03, 2023 7:18 pm
Well it works! Absolutely quiet too. With Sennheiser 650s there's more than enough volume so I don't need any gain.
I'm using it with one of Andrew's general 3 leg reg PCBs, so just a simple LM317 series reg to get me +12V. I wonder if a nice shunt reg might be beneficial here? Any suggestions/thoughts?
I'm wondering about a Jung/Didden superreg which seems highly regarded, but it uses D44H11 transistors which are out of stock at all the usual suspects and it will be a long time before they have any more. Bum.
#33 Re: Valve Headphone Amp
Posted: Sun Sep 10, 2023 9:37 am
I just built the super reg and I got the transistors on Ebay from a guy in the UK. They seem fine. The regulator works a treat.
#34 Re: Valve Headphone Amp
Posted: Mon Sep 11, 2023 7:52 pm
Thanks for the feedback Tony. I've been working my way through the monster thread on DIYAudio for some light relief - like many monster threads there there's a lot of noise between the nuggets. But I've found alternative recommendations for a number of the more tricky parts so may well give it a go.
#35 Re: Valve Headphone Amp
Posted: Tue Sep 12, 2023 1:09 pm
I've PM'ed you the Ebay suppliers I used for the hard to find transistors and the AD825s/
#36 Re: Valve Headphone Amp
Posted: Tue Sep 12, 2023 1:38 pm
#37 Re: Valve Headphone Amp
Posted: Sun Nov 26, 2023 6:31 pm
The SuperReg made a huge difference, it transformed the sound. I've slowly boxed it up, in a similar style to the DAC I boxed recently.
Interestingly though when I put the lid on humming becomes audible and there are vibrations though the chassis. With the lid off there is very quiet humming that can only be heard from say 200mm away. There is no vibration that I can detect touching the trafo lams.
With the lid on it's like a vibrating machine!
It's a steel Hammond chassis. The main box is grounded to PE, the lid isn't really bonded to the box. As the lid gets close to the box, say 5mm, the humming/vibration starts. I'm guessing it's some kind of magnetic field effect?
Might proper bonding of the lid help? Any thoughts or suggestions?
#38 Re: Valve Headphone Amp
Posted: Sun Nov 26, 2023 7:26 pm
Is it mechanical hum or through the headphones?
#39 Re: Valve Headphone Amp
Posted: Sun Nov 26, 2023 8:11 pm
Mechanical, there's nothing I could detect through headphones
#40 Re: Valve Headphone Amp
Posted: Sun Nov 26, 2023 8:33 pm
Stick some damping on the lid then would be my thought. May be the field from the tx moving the lid.
#41 Re: Valve Headphone Amp
Posted: Sun Nov 26, 2023 9:10 pm
Yep that's worth a try.
I can't help thinking though that there's something going on that's not good - very modest vibration increases significantly with the lid in place. The trafo does not seem happy.