Best modern 6550 tube for ARC per-amp

that 6550 is not in the signal path, but I bet you will still hear a small difference. 

I would be inclined to try a PSVANE KT88 gray glass tube...

Audible differences can cleanly  be heard with any old Jimmy Buffet song, fellow Parrotheads…

There have been man anecdotal posts over the years regarding tube rolling in ARC Preamp’s, and the 6550 in their power supply definitely changes the sound....and I can “parrot“....ah I mean 
confirm, (😊) , this in my observation as well in my REF 6 SE......
Cheers....

i have….let me look ( press the button ) 5,188 hours, blissful hours on my Ref 5se. In this preamp, this circuit this tube matters. As do tracking the hours on it. ARC recommissioned 2k hours on that tube. I have about that on a NOS New Jersey Tung Sol from the 60’s. It transformed the bass and mid bass in my system even vs a new direct from ARC tube. Andy at Vintage Tube Services. i trust him. 

@mmbl622 
I find in interesting how so many can so passionately claim there is no way a voltage regulator tube in the PS can play a part in SQ.  Well I was a skeptic until yesterday.  I recently got an ARC REF 5SE and wasn't as impressed as I expected moving from the LS27.  My 6550 had about 1800 hours and I swapped a new EH 6550 and was blown away.  I took the time to swap the old one back and then to the new one again and there was no question.  Everything opened up with such better detail.  All the instruments and voices popped and were so precise.  I had read in some thread here a while ago how important these 6550s are in ARC preamps.  I am going to stock up on the Sovtek as that is what ARC ships their units with so that's good enough for me.  

good input ralph

the ref 6 is a true balanced model though... but probably what you say still applies...

question -- would a 6550 that sounds good in an audio amplification role be necessarily a ’good sounding’ one when asked to do voltage regulation, or are certain other characteristics of the tube more important when acting as a regulator?

In any single-ended product the quality of the regulator is certainly quite audible! And while the signal does not go through it, the regulator has to have good linearity just like any power amplifier- and that is exactly what it is. So you want to use a good tube. JJ makes a blue glass variety that is quite nice and not crazy money, also reliable.

Indeed, far from perfect. I could recount/regale endless stories of questionable moves/decisions made over the 40 years in this "hobby"...

@tubegb

So, now one of your proposed strategies is to place a tube of questionable history, possibly fake, and with untold/undetermined hours of use in your $15,000 preamp?

lol...

well i guess we have all scratched the scab off of a healing booboo, make a bloody mess ... sometimes in spite of what is good for us... path to nirvana is often over some rough terrain in parts

So, now one of your proposed strategies is to place a tube of questionable history, possibly fake, and with untold/undetermined hours of use in your $15,000 preamp? Right, makes perfect sense.

Anybody who have experience to compare the sound quality of these tubes:

Re-issue Tung-Sol 6550 vs GE-6550A 
Svetlana 6550 vs GE-6550A

Someone offer me a 2nd hand green words version GE 6550A which is slightly use (asking the seller how many hours is use) at US$78.   Not sure how's the sound quality.

Another concern is not sure how's the condition of this tube because this is a used tube. Although the seller said it is only slightly use , I don't know how many hours it has been used. And I don't have any tester to test it. 

I run various KT88 and 6550's in my ARC Anniversary Reference preamp along with Herbies tube dampers in all spots and can hear a difference between tube brands/dampers,  I also roll 6n6p tubes as a drop in sub for the 6h30p's for a very nice (and cost effective) upgrade...

just a note to the op - who is seeking info here

don’t mind us tired old hacks here on this board doing a little keyboard jousting in the late night... some joust better than others when scotch or burgundy or ........ is involved  :)

what you will hopefully take away substantively from here is that given the ref 6 uses the 6550 in the ps voltage regulator function (and not a primary signal amplification function) replacing that tube for hopes of better SQ is a ’maybe’ proposition - certainly more of a 'maybe' than upgrading the tubes actually handling the music signal (even though that can’t be done on your unit given the 4x 6h30p’s...)

but yes, in practicality, it all matters (more or less is the main issue at hand) and it is just one tube, so it’s hard to waste too much money chasing a ’maybe’ in this case - i would still suggest checking in with greg at arc to get his take/advice - they made the amp, their input is valuable

my post below was only sarcastically referring to your ref 6 as a p-o-s -- hopefully you don’t take that seriously, we all know it is a lovely piece, one of the very best - i have the ref 3, love it, can only imagine how sweet the ref 6 sounds

cheers and good luck

That's another thing I like about JJ, besides the sound quality, which is very near the top, you get a price that is very near the bottom.   
Almost all Tubestore.com tubes come with a 90 day warranty. The warranty on their Preferred Series is 6 months. I have never in nearly 30 years had a tube fail between 90 days and a year. In fact, I don't ever recall a tube failing in under 2 years, except for a couple Preferred Series tubes that blew within one month! The only tubes I would strongly advise against, had the best warranty. The extra you pay would seem to be for the warranty you will use. Hard to imagine anyone seeing the way mine failed would consider that worth the risk.   

All the many others, if they make it past the standard 90 they probably will go a good long time. Paying extra for a one year warranty in other words is a good profit center.

Sophia audio makes some very good sounding tubes. And for a bit extra get a year warranty.

ARC used the Russian SED "winged c" 6550 tubes. These may no longer be available. A good alternate would be a NOS Sylvania or Philips 6550. 

your $15,000 p-o-s minnesota made linestage has a sucky, marginal PS circuit that requires a gold-plated, absolutely best sounding tube (when used in a totally different application) to sound its best!!! yes -- be sure to get your money’s worth now... remember, we can’t take it with we when we expire, right?

now excuse me, need to join my fellow parrots as we listen to some birdland :)

<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>

Why the smiley face at the end? It’s obvious to me you’re being "Mr Know it all". You do have a way of just sounding like a special JERK... Fancy comebacks and all.
YUP That's you, Mr. Yourassholyness, I bow to your crappy reasoning, but I’ll pass on the rude delivery. You need to learn some manners, they don’t cost, they only pay... We can really get nasty if you want....I prefer you learn to be a Gentleman, not a Jerk... Your call.. Your information is overshadowed buy your fragrant continual sarcasm, you keep spewing, at anyone and anyone will do"

Non of the 15,000.00 comment or the sucky PS statement were called for... Learn some figgin’ manners.. No why not, BUT how can we....

Broken record.. Eeyore  or Winnie the Pooh

I’m in the " all tubes matter " column. Not that it has to be some humpty dumpty valve.. A good "one" NEVER hurts.. The quality of the valve and the construct.... OH YEA.. it matters... Super rare NOS NO. High quality, stable, zero noise, ALL go a long ways though...

Just a thought...

Regards

well there you have it, op - the experts and truly knowledgeable have spoken... yes, everything matters... of course it does!... no concern over matters of degree, or relative importance, sensitivity of inputs on the ultimate output/objective function ...

your $15,000 p-o-s minnesota made linestage has a sucky, marginal PS circuit that requires a gold-plated, absolutely best sounding tube (when used in a totally different application) to sound its best!!! yes -- be sure to get your money’s worth now... remember, we can’t take it with we when we expire, right?

now excuse me, need to join my fellow parrots as we listen to some birdland  :)

Brother. Just so you know, by this "logic" the diodes, power supply caps, fuses, transformer, power cord, AC power conditioner- none of that matters because "it does not directly participate in the amplification circuit of the audio signal". The reason they call it "parroting", the bird too is just repeating sounds it knows not the meaning of. And yet, at least it doesn't get too snooty about it. Score one for the bird.

Meanwhile, back in the real world (or at least planet WeCanHear) where tubes do make a difference we can hear: JJ. These are the tubes you are looking for.

op

you do realize that the audio research ref 6 linestage uses its single 6550 tube as a voltage regulator in the power supply section, feeding the 4x 6h30p controlled gain section, right? this has been the case since the ref 2a model... where the power supply/regulation circuit incorporated a single 6550

as such, you do not/will not ’hear’ the 6550 in that unit as it does not directly participate in the amplification circuit of the audio signal... unlike 99% of other amps using that tube as the power tube pushing/pulling the actual musical signal...

given this, i suggest you simply follow arc’s factory guidance on what 6550 tube to use... longevity and adherence to performance spec as designed is more important than any perceived sound quality difference  -- or email greg christensen at arc service/support and ask him what they recommend as an upgraded 6550 for your ref 6 (they may say there is none)

Wow, it's a regulator in the power supply, helps keep the B+ at a constant voltage. Music doesn't pass through the power supply at all. That happens at the output stage.
If the music is modulating the power supply than the power supply is sagging due to poor design, good in a guitar amp, not in a hifi amp. And certainly won't be happening in an ARC amp.

BillWojo

Think about it. The amplification tubes modulate this B+. The cleaner it is, the better the sound. 

All Tubes Matter.

Any 6550 will work fine! That tube is a voltage pass-regulator in the power supply. It is used to regulate the B+ voltage. The music signal does NOT go through it! No effect upon sound quality!

Kevin at Upscale recommends the new TS. Get the highest grade version.
https://upscaleaudio.com/products/tung-sol-6550