The amp will need a few days of burn in from past experience of using vintage Ccore transformers and chokes, not to mention the miflex kpcu caps which sound muffled for the first couple of tens of hours.
It’s built for high impedance dynamics in mind, that’s my headphone of choice even if I desperately tried to like planar and get away from the 650. I’ll need to revisit ZMFs, didn’t like them before but I’m guessing I’ll have a chance of heart with proper amplification. The utopia is pretty spectacular and in full bloom but the difference is not as great as I’d like.
Got it, I understand so not with your Mysphere cans. I believe you like your Myphere-Stellaris pairing.
I like my Eikon and 650 with the Starlett (which I’m demoing). I’m leaning toward getting the Stratus (which I hope to demo before deciding). But then I’m also considering the SR1a or Mysphere as a future purchase. I like tubes, which are associated more with the Mysphere as opposed to the SR1a.
I cannot use MySphere on this amp due to the tube selection. Tube amps are a huge lists of compromises, sure one can try and build a one size fits all master of none but from experience and discussing with other audio enthusiasts it’s better to keep it focused.
The compromise in this case is the 801A, it’s great and hugely appreciated but has a high plate resistance of 5K.
2A3,300B works with an output transformer of 2.5K, 45 needs a 5K, 801A needs a whopping 10-15K.
Now transformers don’t have an impedance, they just reflect what’s on the other side.
Also the higher the tube load the lower the THD but power transfer is not optimal, not an issue for 100+db headphones but still a compromise.
So a ZMF of 120ohm will present 17K to the 801A considering I’m using a 1:12 otp. It’s pretty perfect actually. Some renowned builders go up to 5 times load for output tubes, DNA amps adhere to this philosophy.
To continue, HD650 reflects 43K to the 801A so we’re expecting a super low THD but still plenty of drive.
Now, mysphere 3.2 will have the same 17K as ZMF as its 120ohm as well but 3.1 is only 15ohm and reflects a messily 2K far below the minimum meaning it will be horribly distorted.
I could have optimised the amp for MySphere 3.1 but I couldn’t use the others due to steep trafo ratio.
This is why among other reasons I wanted to have two amps with multiple parts to spare, my big amp the PX4 with Magnequest otps is perfectly suited for all my headphones, bigger amp, more space, more parts, less compromises.
Thanks for the explanation. I hear you on compromises and trade-offs. I generally value specialization of labor over one size fits all (versatility), if the goal is the highest performance in any given category. And even if one could achieve a one size fits all unit, is it worth the cost, weight, etc.
My understanding is that all ZMF dynamic cans are 300 ohm.
Upgrade time, a full vintage C core hermaticaly sealed oil filled parmeko military PSU setup.
Only the top of the top such as Thomas Mayer amps have these sort of crazy setups but in my case, with only 250mW of power into 300ohm I can go as exotic in a reasonably sized chassis.
This is about as good as it gets without going bonkers with F3CC/AMCC cores. Those are reserved for otps.
Speaking of volume, I’ve implemented a new type of attenuation. So far I’ve tried:
cheap generic
ALPS blue
TKD 2CP
Bottlehead BeQuiet 36 steps
Khozmo shunt 47 steps
DIY 40 steps with blore edwards switches and 1% resistors
All of the above have one thing in common, they lower voltage by converting it to heat, say for a 2V typical source, using the pot at 9 o’clock it outputs say 0.5V, that’s 1.5V converted to heat in the voltage divider. Some say this is detrimental to SQ and transformer based volume controls are better suited for ultimate quality, either a TVC or AVC(autoformer). There are also optocouplers but that’s another story.
A major drawback of an AVC/TVC, the switch, a 30 position high end selector switch is £200-300 and even so it’s limiting, I prefer at minimum 40 steps.
Here’s my new volume solution/passive preamp with in built balanced to SE output.
Get some vintage 50 year old silver plated military 15 way 4 pole switches bbm. Ebay auction for 15£
With plenty of patience file extra grooves at equal distance and convert it to a 30 way rotary switch.
50 step AVC volume attenuator, it’s smaller than it looks and sits next to me. Might put an acrylic top panel.
Parts were 700£, a passive preamp of this quality and features is two to four times more, especially in a fancy case.
I’m also interested in a dedicated headphone power amplifier to use with a separate preamp. What are your thoughts/experiences with DIY removing the preamp stage from an amp such as the Schiit Asgard 3?
Experimenting with different input transformers, these have such a large impact on the overall system once at a certain point and IMO make or break the sound.
From left to right, the 2K optional balanced upgrade to the Stellaris, a custom OCC Sowter and a generic cinemag found in EC Af and other high end amps. All of them are above the standard Jensen ISOMax line with Audio Note being unsurprisingly the best by far if the amp/chain is transparent enough.
Yes, all Audio Note transformers in his amps are custom made to Donald’s specifications, off the shelf parts are usually not good enough for the upper high end when one is after the goldilocks operating point.
Something outside of the usual and a first for me, push pull EL84, balanced output in ultra linear configuration without capacitors in the signal path.
I wanted to try the Susvara on a tube amp with balls, this puts out 10W with very low THD, as clear as tubes can get on paper hence the name ultralinear
Step 1: visualise, lay out the components and let them speak. Full double C core for the PSU and Sowter output and input for phase splitting.
Step 2: chassis and 3D printing, tried a tiled approach on a shallow aluminium frame, not the prettiest but real easy if I ever need to change anything.
I know the iron will need a few days to stabilize, all my amps are a bit hazy and congested at first, even so a quick listen with the Susvara showed why I needed this amp, the low end is now in full force, even more so than a similar power solid state amp powered from ultracapacitors.
I remembered you the other day. As someone who’s had 2 650s and 4 6XXs, do you think the modern 650 is worth going to for build quality? Thinkiing about getting one from Sweet Water. I trust you when you mention them sounding identical.
