Next I'll bring the unit to my buddies Hi-Fi store to test with his variety of headphones (mostly Sennheiser and HiFi Man). I think it's ironic that the last power amp I built was single ended and the headphone amp I built is push-pull!

Here's some preliminary measurements for those who care about such things. I used REW V5.1 to generate automated sweeps into a 38 ohm load, sampled into my Creative Labs external USB soundcard.   The response is flat and the distortion is low. This is with the attenuator wide open so is worst...

Here's pics of the prototype. The casework is an old Carver preamp chassis I picked up at surplus years ago and has housed many projects in the development stage. The power supply is a standard ESA external regulated that I use for all my line-level products (not shown)   I will add the...

thanks Monsterzero -   Unfortunately, when it comes to tubes nothing is "affordable" that can 'do it all', unless it's made in China! That said, it's a pretty simple circuit with a big-ass power supply. This amp will be able to drive low and high impedance 'phones for sure. Pictures to come...

Well, after a long delay in finishing another project I got around to building the prototype headphone amp as discussed above. I went with single-ended input and single-ended output, and can have custom output transformers wound to accommodate both single-ended and balanced output. The circuit...

nahpungnome Mine have the wrinkles too. I think it's anything to worry about. Mine sound fantastic after breaking in. Going to build a nice amp to drive them now.

Yes of course.. female. I work in pro audio and XLR outputs are always male but we're not talking about established standards when it comes to stereo equipment! I think maybe a set of binding posts for speakers (very high-efficiency) would be fun and run them directly off the amp..   I have...

Thanks for the responses!   To address a few questions and points:   Since the output is transformer coupled it's easy to add a balanced output. Looks like 4-pin XLR (male?) wins. 1/4" TRS will be the locking Neutrik connector. There would be a BAL/UNBAL switch.   The line outs would be...

First off, isn't UK line current 50Hz? 60Hz(or 50Hz) hum implies line voltage, and that usually happens when you have the unit too close to a 60(50)Hz source like a large power transformer. Since you've moved the unit around the house and still experience the hum, are you certain it's 60(50)Hz...

I have no experience with your amp or 'phones but I do know that some matches aren't 'made in heaven'. Also, you may want to run the amp and phones for 24 hours with music on shuffle, medium volume, and let them break in. They may sound better (I know my old 448's sounded much better after a...

Hi all,   I've been lurking around here for a while now, have made a few posts in the DIY section as well. I'm mostly a hobbyist but have a small side business building tube audio equipment; I don't make much (if any) $$ doing this, it's basically a self-supporting hobby.   I recently got...

Thank you for letting us know what's going on with you. Under the circumstances it's easy to understand your absence. Please take care of yourself and do what is most important for your health. Be well and good luck with the surgery.  

Wakibaki - What's going on man?

Yes, do take care, sir.. eat healthy and be healthy. Let's hope those scans are benign. :)

Yes, of course - dual primary. As for voicing, there are so many variables that can affect the sound one could devote a ton of time to one circuit 'voicing' different parts, wires, sockets, connectors, layouts..

Epstien, I like your circuit, very sexy. Next time I come across some dual secondary interstage trannys I'll give it a try. Takes the whole capacitor voicing issue off the table.   Here's a link to a place that sells new compactron sockets, 9, 10, 12 pin, etc. in CERAMIC...

Quote: Very neat build on the inside too. Great job.

Great looking colors! Love that Edcor Iron. What is the configuration?  

Great work W. You've thought things through very well indeed. So is the amp with the smaller transformers the reverb ones? How did that work out sound-wise? I think you've done a good job of proving that 'cheap' iron can be utilized in these amps to good effect. I use 70V 4W speaker transformers...

Looks like you've been busy! So this is for the second build?

Quote: Thanks so much! The enclosure is surplus, it used to house an Avid 8X8 Digital I/O box for Pro Tools ('90's vintage) that I picked up at a local recycler for 15 bucks. The front panel is my design and machined and engraved by Front Panel Express, also local to Seattle. The PCB is...

Yup. A 40 cent part!

This is my recent build: Here's a prototype headphone amp / linestage that I built for my brother. I is a two stage design using 12au7a's and output transformers, Quam 70V 4W speaker transformers in fact. The gain is 1.5 using the 2W input tap. There are 3 stereo inputs, a headphone output...

Quote: I had it made for me! It's a double sided PCB with tinned plating, I usually don't opt for the green enamel coating as it costs more and is just another dielectric. PCB Express has CAD software (their own) that's pretty good. You design it w/ their software and they send the...

*edited* See below