@cucu70 .. also check out Salas' Mesmerize pre. The board is available in the diy store. It's kind of like an Iron Pre without transformers and based on using two K170's. It ha a shunt regulator and source selector as well. https://www.diyaudio.com/community/threads/mezmerize-b1-buffer-preamp.213998/ If that tickles your fancy I have a half built Mesmerize that I will probably never finish if you want one.
According to Papa's whitepaper, the impedance at the source pin of the JFET is about 50 ohms, however the standard design has a 1K "safety" resistor in series with the output.
I don't think so. Not with a ~1k output impedance, it will probably sound muffled and distorted. If you want a good headphone amp, I'd look at the ACP+.
The reasons I didn't suggest that is because I don't exactly know how the 1k resistor functions from a safety perspective- I can only speculate that it is to prevent a short on the output from somehow frying the output JFETs. Now it's worth asking what might happen when one connects or disconnects the headphones while the B1 is running, if the 1k resistor is removed. Will there be a current spike? There is a 10uF capacitor there. What might that spike do to either the JFETs or the earphones? What might it do to your ears?
Mr. Pass gives us all these great DIY preamps, and with an eye on safety, they all run off wall warts/power bricks. I wonder if Mr. Pass finds using only one power rail limiting or a challenge. Interestingly after the B1 rev2 which is a virtual ground the designs go back to cap coupling. My first impression was that there were not many wall warts with dual rails, but recently I've taken another look. They need to be cheap and highly available and I have found 3 that fit the bill.
- MEAN WELL GP25A14E-R1B (+5v,+15v,-15v) - Both Mouser and Digikey stock it but it's a bit costly at $35 for more money there is also a 50W version.
- Mixer Power Supply Adapter for Universal 2-16 Channels 4 Pin Mixing Console S9L9 (+48, +15, -15) - Just google for it, they're all over the place and cheap at $11
- 17v Mixer Power Supply Adapter 3-pin (17vAC,0,17vAC) - Just google for it, and it would give you +25v-0--25v rectified, it goes for a whole $19 but can be found for $12
- High-power Mixing Console Mixer Power Supply AC Adapter 17V 1500mA 50W (17vAC,0,17vAC) - Just google for it, this one is a transformer so it would give you +25v-0--25v rectified, it's $25. But it's still that power brick form factor so no one needs to deal with the mains.
Note that the MeanWell above has a very asymmetric negative rail compared to the positive.
These are all very interesting and will be looked into!
These are all very interesting and will be looked into!
As a free soul you can always roll your own power supply. Not wall wart. Transformer. Over-dimensioned. LM317/337. Or something more advanced. Full Hiraga with batteries and supercaps. Whatever you fancy and believe in. (It’s not dialysis you know.)
audiosteve,
I'd like to see the schematic and gerbers for your linear supply. Like the concept.
Thanks
Carl
I'd like to see the schematic and gerbers for your linear supply. Like the concept.
Thanks
Carl
@carlpysd, I'll post something soon, or PM you. I don't want to hijack this thread. @SRMcGee. Yes, Heat sinks would be a very good idea if needed. But not needed for an aplication that draws little current. They were not overlloked but were left out by design. But.. I suppose the TO-220 regulators could be placed so the leads could be bent and the parts bolted to the base of the chassis a a heat sink, if needed, rather than upright.
@carlypysd, check your messages. You have all the files now. Let me know if you have any questions. Let's PM instead of talking here.
how to add gain with any B1 variant? I'm using dcb1 with salas bib supply, many K170+J74 match pair so this rev2 is doable for me.
6dB gain should be enough to give more ompph on M2 or SIT L'amp
6dB gain should be enough to give more ompph on M2 or SIT L'amp
