The Stax Thread III

[TheAbyss2022]

My ss amp needs warm-up too but around 45 min.

Factors such as the ambient temp in the room will also determine how long a full warm up will take. I think it did warm up within 2-3 hours if the room had the heating on.

 

[mbrennwa]

The high-voltage transistors used in many of these amps generate a lot of heat, and they get really upset if that heat is not dissipated away fast enough.

Overheating transistors are the result of a poor design or build. That's not specific to e-stats or audio, but is true for all transistor electronics in general. If you experienced these issues only with estat amps, then that's because these amps were not designed/built very well, while all your other electronic devices were fine. My class-A loudspeaker amps run very hot, but there's no problem at all after many years of using them.

 

[Philimon]

niiice

Minidsp EARS, 252s

For comparison (dont feel like unpacking the external hard drive with old measurements for overlay):

^ test-fit. I left the dust filters in place for these measurements though I may remove later if want more highs.

^ I slightly modified the headband by shaving off the small bumpers that limit max headband adjustment. I have a big head plus the thicker pads need more room…

^ small vents (1x2mm) for air pressure relief.

 

[mulveling]

My Carbon CC is left on 24/7 and it gets a little hot when the heating is on at night but I haven't had any issues in the past few months with it being left on. I leave it on because there is around a 5 hour warm up lol.

The offboard heat sinking for KGSShv and Carbons is generally ample, and you can trust Mjolnir to makes amps that operate well within reasonable parameters. The long warm-up is perhaps an undesirable side effect of having such ample heat sinking (takes a long time to hit temp equilibrium and optimal operation point), but certainly preferable to the alternative! Tubes never need much warm up time to sound their best.

Overheating transistors are the result of a poor design or build. That's not specific to e-stats or audio in general. If you experienced these issues only with estat amps, then that's because these amps were not designed/built very well, while all your other electronic devices were fine. My class-A loudspeaker amps run very hot, but there's no problem at all after many years of using them.

Yes, of course. I'm just reporting my experiences with owning & trying dozens of each component type across head-fi and 2ch (which is much my passion these days), and what gave me problems. Adding to the challenge of these e-stat amps, is the fact that if any transistors go down, it's often long OOP and hard to find genuine replacements.

 

[Rob80b]

Yes it sounds a little flat and dull for the first couple of hours. People think its only the tube amps that require warm up but actually the SS amps take even longer to properly warm up and the upside is the ability to just leave them on 24/7 to rectify this issue.

I was noticing that, the overall sound appeared to be less stressed when left on for a few hours before listening, thought it may have been my imagination... but was then wondering if it's in combination with the charging of the diaphragms themselves and steady capacitance. With dynamic drivers there may be some slight change with continual use and then that eventual evens out but with the electrostatics this appears to be on going each time they are turned on.

 

[mulveling]

I've never noticed a warm-up or "charge up" time for e-stat headphones themselves. My understanding is their diaphragm coatings are meant to ensure they take a full charge very quickly, and hold it evenly. If the coating fails (e.g. from abuse), you may have problems. I've had two 009 that sound exactly the same, for over 10 years now, and never noticed a difference if I freshly plugged one in after the other had been in for a while. There's been some past kerfuffle about certain amplifiers that supply their 580V bias derived from a musical signal (which entails a slow start), and hopefully that's not a thing anymore (it was one of the Audio Valves).

The components I've noticed with protracted warm up times have always had SS components. The BHSE is a prime example that sounds its best after a good while on - I've heard it myself - and I'm sure due to the transistors, not tubes. All the "pure" tube gear I've owned has gotten where it needs to go pretty quick, no more than 10 minutes max. The DIY T2's are not quite pure tube, but they also don't take too long to warm up, and sound great from the go.

 

[alota]

I've never noticed a warm-up or "charge up" time for e-stat headphones themselves. My understanding is their diaphragm coatings are meant to ensure they take a full charge very quickly, and hold it evenly. If the coating fails (e.g. from abuse), you may have problems. I've had two 009 that sound exactly the same, for over 10 years now, and never noticed a difference if I freshly plugged one in after the other had been in for a while. There's been some past kerfuffle about certain amplifiers that supply their 580V bias derived from a musical signal (which entails a slow start), and hopefully that's not a thing anymore (it was one of the Audio Valves).

The components I've noticed with protracted warm up times have always had SS components. The BHSE is a prime example that sounds its best after a good while on - I've heard it myself - and I'm sure due to the transistors, not tubes. All the "pure" tube gear I've owned has gotten where it needs to go pretty quick, no more than 10 minutes max. The DIY T2's are not quite pure tube, but they also don't take too long to warm up, and sound great from the go.

Indeed. Tube's warm up is faster compared to solid state

 

[LarsHP]

The offboard heat sinking for KGSShv and Carbons is generally ample, and you can trust Mjolnir to makes amps that operate well within reasonable parameters. The long warm-up is perhaps an undesirable side effect of having such ample heat sinking (takes a long time to hit temp equilibrium and optimal operation point), but certainly preferable to the alternative! Tubes never need much warm up time to sound their best. (...)

Good point!

My experience with SS amps and DACs is that there seems to be subtle improvement beyond a few hours of warm-up, so I keep my units on 24/7, except for power amps running full class A.

 

[mbrennwa]

The warm-up time is determined by the "thermal inertia", or the heat capacity involved with a certain part. The heat capacity of a transistor is surely less than that of an electron tube, simply based on the size/mass of the parts. In other words, pretty much any transistor will "warm up" much quicker than a tube. However, transistors need (sometimes big) metal heatsinks for power dissipation, while tubes don't (at least those commonly used in audio). Coupling a chunk of metal to a transistor adds a lot "thermal inertia", so it takes much longer to attain thermal equilibrium for the transistor/heatsink. The real "warm-up difference" between solid-state and tube amps is a result of the thermal inertia of the heatsinks, not the tube/transistor parts themselves.

 

[mulveling]

The real "warm-up difference" between solid-state and tube amps is a result of the thermal inertia of the heatsinks, not the tube/transistor parts themselves.

It's the parts too, though. Tubes literally have a "heater" element for getting the cathode up to a very high temp quickly. With transistors, heat is just a waste product.

 

[mbrennwa]

Tubes literally have a "heater" element for getting the cathode up to a very high temp quickly.

Sure. However, the heat dissipation by the heater/filament is usually just a fraction of that due to the plate voltage and current.

 

[Rob80b]

Little show and tell, ....now that I've some Stax it sort of completes the musical circle in a long standing tradition of "Handmade in Japan"...my Miyazawa Flute (new to me) from 2002 and Yamaha upright piano, 1977.


Speaking of flute, if one is into modern classical, this album sounds really good on the Stax.
https://listen.tidal.com/album/301456886

 

[ericj]

I've never noticed a warm-up or "charge up" time for e-stat headphones themselves. My understanding is their diaphragm coatings are meant to ensure they take a full charge very quickly, and hold it evenly. If the coating fails (e.g. from abuse), you may have problems. I've had two 009 that sound exactly the same, for over 10 years now, and never noticed a difference if I freshly plugged one in after the other had been in for a while. There's been some past kerfuffle about certain amplifiers that supply their 580V bias derived from a musical signal (which entails a slow start), and hopefully that's not a thing anymore (it was one of the Audio Valves).

I have, but just the old Magnavox SR-3 variant. It has to sit for quite a while to charge up.

 

[timb5881]

I have, but just the old Magnavox SR-3 variant. It has to sit for quite a while to charge up.

My Realistic HP100 electrostatic, different badge but the same. Anyway if I unplug the bias, it can take over a week to build up a charge when plugged back in.

 

[ericj]

My Realistic HP100 electrostatic, different badge but the same. Anyway if I unplug the bias, it can take over a week to build up a charge when plugged back in.

I wonder if refreshing the parts in the energizer may help, or cleaning connectors, or something like that may help. I don't even know where my stagnavox is right now. It is a pleasing headphone, for what it is. I do know where the superex is, but it's such a wretched pile of crap wrapped around SR-3 drivers that i think of it as more of a future project.