My VTA ST-120 is on the way .....and other loose ramblings of an old fart

Ahhh!   ...it's Saturday!   ....Tube Biasing Day!
The bias on the KT-88s have crept up some to around 57.5mA so tweaked them back to the recommended 55.0mA after a 30 minute warm-up.

Note from Bob on 2/8/20 > The VTA ST-120 recommended bias is 50 milliamps per each output tube and not 55 milliamps as Cletus has mentioned here.

https://dynacotubeaudio.forumotion.com/t3043-vta-st-70-assembly-video-and-new-bias-recommendations-for-all-vta-amps updated recommendations Cletus

VTA ST-120 with 6550, KT88 or KT120 output tubes > recommended bias setting is .50 VDC per each output tube which gives a bias current of 50 milliamps per each output tube.

https://neilyoungarchives.com/#/?_k=os2fmc He has put a lot of his stuff up for free streaming in hi-res audio Cletus - fun to try even if not particularly a fan


https://archive.org/details/GratefulDead?sort=-publicdate áll of their stuff is free on the Internet Archive in various qualities - some pretty high, some pretty low ^^

Roy wrote:https://dynacotubeaudio.forumotion.com/t3043-vta-st-70-assembly-video-and-new-bias-recommendations-for-all-vta-amps  updated recommendations Cletus

VTA ST-120 with 6550, KT88 or KT120 output tubes > recommended bias setting is .50 VDC per each output tube which gives a bias current of 50 milliamps per each output tube.

Jim McShane advises to push the KT-88s at 55mA

Duly noted ^^ I will need the punch to drive my towering infernos anyways..

My saturday was spent fixing up an 80's pioneer turntable - last step after going over all the switches and mechanics is to polish the dust cover up nicely and put it up for sale ^^  then   on to my lovely Dual 721 for a good service job..
Pioneer never really got into making anything high end but they made some nice tonearms imo




I have álmost hit my target of clearing out old stuff before new stuff can come in at the ratio as set by my wife =]

Please don't remind me about turntables  ....having got rid of my Oracle Delphi (had a Hadcock tone arm on it and rolled quite a few cartridges) around 1992

oooooh those were nice indeed
had quite a few here too..
in the end before choosing to just get rid of it all
the dual 721
automatic enough for my wife
and well sounding enough for me with the Shure V15 III

The Dual turntables do not excite me, too much machinery.
However I have a 1019 that is excellent. I think the best one I've seen.

Good engineering yes..
721 was the best DD deck they ever made - style might not appeal ( does not to me ) but
can't argue with the engineering.


good stuff ^^ *skip to 5:50*

My Music Server / DAC

That is a really NSFW case isn't it ^^

Might have found a nice wooden box for mine finally.. Got that same case but smokey black but since we use it for some intensive tasks something with some active really quiet cooling is going to have to get done the folks at Boss dont expect oddities from a 10cm GPIO extender ribbon cable so I can separate the pi and the dac into an all vertical plane - and flip the cinch jacks to the rear =]

Roy wrote:That is a really NSFW case isn't it ^^

Might have found a nice wooden box for mine finally.. Got that same case but smokey black  but since we use it for some intensive tasks something with some active really quiet cooling is going to have to get done the folks at Boss dont expect oddities from a 10cm GPIO extender ribbon cable so I can separate the pi and the dac into an all vertical plane - and flip the cinch jacks to the rear =]

Extended use of mine shows very acceptable temperatures even without heat-sinks.  Use is not even nearing the loads I put on my (heatsinked) Rpi Kodi system.
I have heatsinks that I'll install on this one just for giggles, when my Arctic Silver epoxy finally arrives.

Try some X/H 265 encoded media.. not so good ^^ The Pi3 will go into throttling. Also some of the emulation runs that bit smoother overclocked and cooling there is handy..

Heatsink alone in some tests ( think I linked to those someplace on the forum earlier element14 site gotta sign up though before reading ) shows heatsink alone cán help with intermittant heat spikes but prolonged cpu intensivity so to say a fan is needed to get actual cooling and stopping the pi3 soc going into thermal throttling - the curves work out to about 10mins from what I recall what a heatsink alone gains you - after that performance is same as without a sink at all. And alu sink stuck on w 3m or arctic thermal epoxy is nice but not fool proof - there are some nice ceramic heatsinks of véry low profile mind you that outperform the alu ones quie nicely and are non conductive should they jostle out of place.. the size that fits a pi3 comes to about 4€ from Farnell. Look like flat blue erasers - sponge like structure with microscopic tubules throughout.

foamed ceramic neat huh beats finned aluminium by a wide margin too. There is finned versions also but those are taller..

Yup, those are very good heatsinks!
My Rpi based Kodi video units run really hot, thus the entire aluminum case is the heatsink.
This Music Server DAC will never see such intensive workloads as only FLAC and MP3 files are on there and it has been running non-stop for over a week without any heatsinks at all and the temps at the chips are very well below limits (hotspots are 48*C max). I think the chip begins throttling at around 83*C 
I got some heatsinks which I will install when the Arctic Silver arrives. The heatsink for the CPU bumps on the cap that's on the underside of the Allo Boss, so I will machine a small rebate in the heatsink for some clearance  .....but, so far so good, very impressive indeed.
I try to exclude moving parts in my builds so I try to keep away from fans if at all possible.

Got some Diana Kraul going on on the system now   .....just lover her voice! It sounds so REAL on the ST-120 !

Rpi Heat-sink/case for my personal Kodi Media-center   ----  the case is machined from a solid billet of 6061 aluminum and internal features contact the Rpi chips directly for maximum heat transfer.

^^
That case is just    boss =D


Read Sade is coming out with something new soon  or already has by this time..
This week here has been filled with hmm lemme think.. Miseducation of Lauryn Hill, PJ Harvey albums, too much Foo Fighters lol ( wife )  and one of my fave live albums - Erykah Badu  Baduizm Live ...that set was   magic

And ofcourse the little one here insists on his daily dose of Dire Straits, Johnny Cash, Michael Jackson and the Blind Boys of Alabama  - can't argue with taste XD

Congratulations Cletus that is awesome =]

Me being able to show and tell with our own vta st 120 is just another month away I hope - another home appliance and bits and pieces of our car that fell off/ground to a halt threw a wrench into the planned purchase lol but my kid is sooo ready to help his dad..

This morning he came to me with a collection of cardboard from the paper recycling drawer and some of the tubes my neighbour gave me from his collection and my extech meter and said daddy can we build the amplifier today?

CletusB
As Roy said, that's awesome news. Thermionic valves rule!

Daughter bought a used car and it came with "music"  .....had to troubleshoot that system yesterday and had to endure the gross insult and assault on my ears!
2x 15" sub-woofers occupy the trunk and blast their way through the backrest of the rear seat. A pair of 6x9" mid-range speakers with coaxial tweeters and a couple dreadful piezos. This thing is driven by a huge and I do mean HUGE power-amp that sports a chrome skull whose eyes light-up red as power indicators. A 4-way electronic crossover manages the splits into that gynormous amp.
I managed to sort out the initial problem (a disconnected interconnect), then I decided to tweak the x-over some (found every knob turned to the max) and tossed those piezos as far as I could throw.
Got it to "sound much better" (not sure if that's really a possibility) .....but man, I still consider that rig an insult and rape of my auditory passages.
But, at the end of the day, she's happy that dad fixed her "music" and I scored a bunch of points!

Just got myself a MiniDSP UMIK-1 and Room EQ Wizard.
So, been playing with it and looking at the response graphs from my three primary listening positions (Studio sweetspot, Dining Table and Living Room):
Not that I'm really looking to adjust anything at this point, since I really like the sound of it all as is (I just like to be able to quantify stuff).




The Impedance Plots look like this:

.....And can arrive at this with a couple tweaks to the passive crossover .....sonically, not sure yet which I prefer (need to walk away from it for a bit)

IMHO Best sonic compromise, physically tweaking the passive crossover (instrumentation vs listening) at this time: