My amp is a duplicate of an SE84 but using Transcendar headphone output trannies. I've learned a lot with this build, especially how different rectifier tubes have different voltage output, which may account for the differences in their sound.

I still have to install the anniversary mod's and try to remove a low-level hum, but it sounds fabulous.

+1  :o

Thanks. Yes I did solve it just a couple of days ago. The problem was the power supply. I installed a 15H/75 mA choke between the filter capacitors.  I also installed a 250 ohm/5W resistor in series with the choke to get the B+ power to the correct voltage. Both of these items replace the 1k ohm/5W resistor that is in the stock amp.

As designed, the power supply filtering in the stock SE84UFO is perfectly adequate for its intended use; speakers. It does hum, but you only hear it if you put your ear up close to the speakers. Not exactly a normal listening position, unless you're weird, or have a very small room.
I had a Taboo II amp a few years ago which, I believe, was the first amp Decware put a headphone jack on, and it had a choke in the power supply.

With headphones though it is quite apparent/annoying. Installing the choke smooths out the waveform B+. Now, using the low impedance output (35-300 ohms), the amp is dead quiet. The high impedance output (300-600 ohms) has an almost imperceptible hum, which is masked if a gnat farts from across the room. I use Sennheiser HD800's btw (300 ohms), from the low imp jack.

With 2.3 watts output, I can only run the volume knob at or below 9 o'clock without going deaf. I can't wait to try a nice pair of planar headphones with it.

With the headphone specific output transformers, this amp is amazing. Very dynamic, but also smooth, with a great soundstage. Personally, I think this is the headphone amp Decware should build. But, that's my humble opinion. :-0

I have a question about plate voltage on the SV83 tube. Depending on the rectifier I'm using, I measure anywhere from 300 to 338 volts at the plate.
The SV83 datasheet (Svetlana) lists 300 as the maximum plate voltage.
Am I going to ruin my 83's by running over 300 volts?

Being a charter member of the 'Don't-know-when-to-leave-well-enough-alone' club, I of course had to tweak things a bit. (Won't bore you with the details). All of the silver stuff is Dynamat to dampen the enclosure and some of the capacitors.



This amp continues to amaze (no, that word is too weak). Maybe stupefy is better. The only other amp I've heard that gives a similar sound is the Eddie Current Balancing Act, which I owned at one time, and cost more than three times what it cost me to build this. You name a trait (soundstage, impact, separation, detail, yada yada, and this amp has it in spades. 'Nuff said.

Thanks. Mostly I dampened the chassis (the bottom is also damped) because the Hammond enclosures are about half as thick as the stock SE84, and I don't think you can have enough 'deadness'. The Miflex coupling cap's really need it because the way they're mounted, if I tapped one, it would vibrate, and that can't be good. The PS bypass cap's also, but to a lesser extent.

Sound wise, maybe a tad more focused, but that might also be me faking myself out.

You can damp a component or tube etc. but dampening it. . .not recommended!

Ha, HK I don't necessarily disagree about the chassis, well I do . . . I find benefit sometimes on some chassises. But my point was one can "damp" of do "damping" for vibration and isolation. . . but to "dampen" or do "dampening" is to make things WET.

I read Lons comment as a joke. I did go and double check the dictionary though lol.

HK, What is your thought process on why it doesn't make any sense? Using anti vibration footers sometimes makes an improvement. Mass loading components sometimes is another improvement. I figure dampening the chassis might be another area of improvement.

GroovySauce,

Mainly referring to applying dynamat or other materials internally to equipment chassis. Sorry, should have been more specific. Also, adding this stuff can reduce resale value of equipment.

I use heavy maple audio platforms under most of my equipment with footers. These do import a noticable improvement in clarity.

Using handi wipes or hosing down electronics ... well I'll leave that discussion to others😁

HK

Made a little upgrade to my amp.





It's now a full blown '25'. I also installed four Tesla glass resistors. The sound is spectacular. Increased dynamics, clarity, resolution. The headstage is phenomenal. [Mic drop].