Tube Rolling for Pre-amps?

I have an Audio Research LS-16 that feeds a Madrigal Proceed HPA2 solid state amp. 

I did not choose this equipment; it was given to me. From what I can tell the original owner spent a good bit of time matching up these two components with the speakers, Aerial Acoustics 7Bs.

The tubes in the AR are original. Probably 10-15 years old? But with an extended period of not being used.

The system sounds good to me. I don't need to change anything.

However, I've been told that the tubes are old and may need to be replaced soon. I've also read a little bit about tube rolling but most of the articles I've seen talk mostly about tube rolling with amps and not pre-amps.

So I have some questions:

1) If the original owner wanted a system that sounded like a 'tube' system, why not have a tube amp and pre-amp? Does it make sense to have a tube pre but SS amp?

2) Other than outright failure, how will I know if my tubes _need_ to be replaced?

3) With a SS amp, will changing tubes in the pre-amp have a noticeable impact on SQ? In other words, is tube rolling for a pre-amp played through a SS amp a thing?

4) For someone like myself who is happy with the system and who is also easily frustrated by A/B testing is tube rolling the pre-amp even worthwhile? I can almost always hear a change when comparing various components but only rarely am able to say A is better or worse than B.

( I probably can't even articulate effectively what I look for in terms of SQ except that I like the bass to be tight, precise, well defined and not boomy. I do not like the music to be overly bright or tinny. I like depth and lushness but not overly warm. Not sure if these are things you alter with tubes.)

Thanks for any advice.

@n80 As a person with a tube preamp and a SS amp, I'll share my 2 cents.
  1. Many prefer to have both a tube preamp and a tube amp.  You get the full effect of the tube sound that way (depending on the equipment as some are more "tubey" than others).  However, tubes in a power amp wear much more quickly than preamp tubes and tend to fail more catastrophically than preamp tubes - possibly taking out resistors in the process.  You should be able to get between 5,000 and 10,000 hours from preamp tubes (again, depending on the equipment).
  2. Preamp tubes tend to get noisy before outright failure.  Right now I have a tube in the left channel of my preamp (BAT VK-3i) that sputters a little as it's warming up.  I've got a new set but haven't pulled the preamp out of the rack to replace them yet.  I looked when I ordered the replacements and the last set I bought was in 2012 but I'm not sure of the hours.  Of course if you know someone with a tube tester you could get them to check your tubes. :)
  3. In general, different preamp tubes DO change the sound but not as much as tubes in power amps.  Preamp tube rolling (SS amp or not) is definitely a thing with some people (who have more money than me!).
  4. I would say that, given your description of yourself, it's not worthwhile to just swap tubes.  However, when it's time to replace those tubes, check with folks here to identify the current helpful/honest tube sellers out there and consult with one or more of them.  If you explain what you're after soundwise, my experience is that they will be more than happy to make recommendations within your budget.
I'd love Roger Modjeski or Kevin Hayes to chat here.

Kevin Deal @ Upscale Audio too.

Best audiophile reality TV show you could get.   
I'll add to @djohnson54 comments. I'm an avid tube roller. At one time I was addicted to rolling NOS preamp tubes when I had a SS amp. 
Depending on the design of the preamp, rolling in a different brand or style of tube can make a significant difference to the overall sonics of a system. Characteristics such as dynamics, transparency, soundstage can all be affected. Many audioholics change tubes to take the edge off the highs, or conversely to add extension and "air."  The caveat is that the amp will play a role in how much of a change in sonics you hear. Your SS amp must be revealing enough to hear the changes from the preamp. But you will hear a difference in preamp SQ or sound signature.

Preamp tubes do last a long time; thousands of hours if purchased from a reputable dealer. A dying tube can become noisy or microphonic. But IME, you can tell when a tube has reached its life expectancy when your music begins to sound dull. There may be less extension, a flat image, or less colour or drive to the music.

I'm a firm believer in having a set of spare tubes on hand. For this reason maybe you should start shopping for a replacement set.

Small tubes often don't fail dramatically in the same way that amp power tubes can- but they will lose their high frequency extension and punch over time. It's almost like a new pair of sneakers- more bounce. 
I'm not sure it is worth getting carried away with expensive NOS tubes in your preamp- look at the complement- are they 6Dj8? (that was pretty common then), and there are many types and manufacturers. Obviously, you won't know what the tubes sound like til you hear them in your unit and system. I'd refresh them for sure, but am not up on current production tubes. 
Tubes don’t get old/weak, from age(only use), unless they have a vacuum leak. If you’re really concerned about the remaining life of your 6922s(assuming yours isn’t the MkII), you might send them to theses guys, for testing: I’ve found them accurate, honest and reliable. Regarding your last question, YES- the presentation you’ve described, can be adjusted with the preamp tubes. Any good power amp, will faithfully pass whatever signal it’s fed, so- make it the best you can. ie: NOS Amperex(a little warmer than stock ARC tubes), NOS Mullards(a lot warmer than stock), NOS Siemens(tighter bottom, airier and more detailed/cleaner than stock). There’s no problem, trying just one pair per gain stage, at a time, to see if you like the change. I rolled tubes through a couple different ARC pres, never trying anything but E88CC/7308 (or better) iterations, with gold pins. I settled on the early Sixties, grey shield, Siemens CCa.   I’ve six in my CDP, now(glad I bought extras, way back when). Good information, here: Then again- IF you’re actually happy with your sound, why fix something that isn’t broken? Just don’t go listening to a lot of live music.
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Right. My point is, tube degradation with small tubes is gradual. You may not hear a nasty and don’t necessarily know that it isn’t performing as fully as it could. Testing only tells you so much. For example, I use NOS ribbed Tele 12ax7s in my Lamm SET amps. (None of these are truly ’never used’ -well, maybe once in a while at a significant surcharge over the already premium price for "pulls").  Six months ago or so, I had a sense that the amps weren’t as sparkly in the high frequencies, and nothing else in the system was amiss. I got another pair. Voila! Back to that sound I love. (The replacement pair was noisy, and the vendor swapped them out for another pair that now works fine). And that 10,000 hour figure cited for some of these high grade tubes? Sure. I’ll accept that. But those "NOS" Telefunkens on the market? How many hours have they already clocked?
( I do actually find never used vintage tubes sometimes, but it’s getting harder, and the popular ones, like the 12ax7 Tele--well, good luck. Not trying to be negative, just my reality).
I rolled bags full of 6dj8 equivalents back in the day. Literally- a few full sized shopping bags of them over the years.
You should have a spare set of tubes as I and others have stated. I like the idea of comparing the new pair with yours, then use the tubes that sound best.

Even though your preamp may have sat idle for a long period, the former owner may have put a lot of hours on his system. Or he could have left the preamp powered up for long periods of time.

I do have the MKI which means 4 tubes to replace or try rather than 2.

@rodman99999 : "There’s no problem, trying just one pair per gain stage, at a time, to see if you like the change."

I’m not sure what that means. Does that mean I can just change 2 of the 4 tubes to get an adequate test of SQ?

"NOS Siemens(tighter bottom, airier and more detailed/cleaner than stock)."

That sounds like what I would want. A search reveals that gold pin versions of those tubes go for around $40 - $75 each. Does that sound right? How careful do I need to be to avoid fakes or crappy tubes?

" IF you’re actually happy with your sound, why fix something that isn’t broken? Just don’t go listening to a lot of live music."

I am actually quite happy with the sound, but there’s always that audiophile neurosis that whispers in my ear that maybe it could be better and I just don’t know how bad it sounds right now. But I don’t understand what you mean about live music. Live music recordings? I only have a few, all on vinyl. Not all that crazy about live recordings, but why would live recordings be a problem?

Edit: At Upscale Audio those Siemens tubes are $135 each and their site says they do not sell NOS. Does that mean they are used? How do you know how many hours are on them? Well, its all academic since right now there is no way I'm spending $500+ on a set of tubes. (I realize that's chump change for serious tube rollers).
n80, you have no baseline or reference to judge the SQ of your preamp.

That’s a good description of Siemens. Where are you looking for tubes and which tube type is $40-70 each? There are 6DJ8, 6922, and 7DJ8 variants.
Check Brent Jessee’s selection. Trustworthy seller with good pricing.

@lowrider57  : " n80, you have no baseline or reference to judge the SQ of your preamp."

That's what I'm saying. It is a blessing and a curse! The blessing is that I think it sounds great. The curse is that it might not. ;-)

I don't remember where those prices came from. Just a Google search. I don't know anything about types. This is what comes in the pre-amp:   6922/E88CC dual triode. It takes 4.
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@lowrider57 -Brent Jesse is cool.
@n80- call him, don’t try to decipher that website. It will drive you absolutely bonkers. I didn’t deal with him for years because trying to decode his website was like reading a bad spreadsheet. He’s a really good guy, and knows tubes, isn’t overpriced and is very fair in my experience. He’s also not a BS seller, which in vintage tubes is very common. There are also some mistakes that can be made out of pure ignorance. I’ve made them. I bought some NOS Mullards printed on the glass as "Made in Great Britain" or some such. Turns out, back in the day, tube manufacturers shifted production even to unaffiliated companies given demand and supply. My British tubes were actually made by Amperex in the US. The seller (not Brent) didn’t know that, and neither did I.
A reliable supplier of tubes is pretty essential, unless you really go full geek. I’m sure there are some posters here who qualify (I don’t mean ’geek’ in a bad way, just that you have to dig deep). It’s another part of the history of this hobby that we live with today and is at times fascinating, frustrating and often maddening.
Yes- Only changing two tubes(either V1 & 2, or V3 & 4) will generally provide you with a good slice of what can be expected, if all are swapped. I’ve avoided counterfeits and junk, by only purchasing from reputable tube mongers. ie(for nine pin miniatures): Brent Jesse, Tube Depot, or this guy from whom I’ve purchased the most: Upscale only refuses to sell their NOS tubes, for use in pro audio equipment. They have lots of NOS 6DJ8 types, for home audio. I found everything that Siemens made, after the early/mid 60s, grey shield CCa, a bit too zingy/bright for my tastes, but- that could just be the rest of my system, ears or preference. I only said what I did, about live music, because after extended listening in good, live venues- one sometimes gets spoiled(perhaps, educated) and the average home audio system MAY then sound, "broken".
@elizabeth : It takes an effort to keep the 'inner audiophile' tame. Even some of the stuff I consider to be wacko beckons at times. But I also have an inner Scotsman that delights in high bang-for-buck ratios which becomes a hobby in itself and helps keep my over-the-top hobby tendencies at bay. I love a bargain that fits a need!

@lowrider57  : I don't think I'll end up being a tube geek. Having a back up set makes sense and I'll probably do that if I can do it affordably. But then that's the first step isn't it? Get the back up tubes. Can't resist trying them out. Like the way they sound. Wonder about a different set.............

@rodman99999 : Currently my live music consists of the symphony 3 - 4 times a year, opera maybe once a year. But that's not what I tend to listen to on my system. I go to loud rock shows a few times a year. SQ at those shows is never great. Fun shows though.
Hey all-

I roll current production tubes so I can consistently get the same sound when things wear out. Once I find something I like, I buy a couple sets. That being said, I also have a stash of NOS for reference.
These were the best tubes I tried in my LS16MKI when I had it.

I tried a lot of different tubes with all my ARC gear.  These are really, really good and aren't that expensive.

I was lucky and started buying tubes over 40 years ago when they weren't in vogue like they are now and were cheap.  I have drawers full of tubes.  Could probably retire on what they are worth now...
I got a philips /mazda 6922 from Brent Jessee years ago that I just put into my c-j Classic 2SE and it was juet as described,  breathed new life into my pre.
@mofimadness On the scale of things in the tube world those are quite inexpensive, even for the platinum. What would you say were the characteristics of those tubes?
Another question: Does anyone know which brand of tubes came in the LS-16 MkI from the factory? I can find the type but not the brand. I could pull my pre-amp out and take the lid off to find out but if someone knows that would be a lot easier. The AR database does not say as far as I can tell.
@n80 my preamp also uses 6922 tubes and six of them so I am always on the lookout for a good value. I was turned onto these by someone in the forums here:
It's a 7dj8 and from Upscale at $30 each a steal. I would call the sound very linear with excellent frequency extension and transparency. Not overly warm. And don't stress too much about tube rolling its fun and easy and preamp tubes will last you a good long while.
I'd like to mention that a 7dj8 isa great choice for you. Someone else also said this in passing. It's important to study the equivalent tube types, especially if you're on a budget. Preamp tubes can have a profound impact on the overall sound of a system. 
@n80  The National 7DJ8 platinum is also what I just got for my BAT (replacing Phillips 7DJ8s which were no longer available).  I'd say that's a pretty solid recommendation.  Dick
Think the tube pre and SS power
covered above (also what
i use) pre really defines the sound.
and tube rolling in pre doe make
a differance most of all in a phono input stage as levels lower. I switched fine JJ ecc83
for telefunken and then a Siemens 5751 tube and the midrange opened up even more. And then the sound was good and I stopped.
If you like the system then just enjoy it
Nos ribbed telefunkens- for her pleasure!
@n80- You got me thinking about my tube inventory. I found a NOS pair of these(the exact same vintage/iteration tubes as in the description, except- the printing on mine is still perfect): If you like, I’ll send them(gratus) and you can experiment. They were a tad too warm(for my tastes), when I tried them(maybe 17 years ago). Even if you don’t care for the sound, it should let you know how much impact tube rolling can have.
@rodman99999 : Thank you for your extremely generous offer. I would like to try that. I will PM you with details and arrange to compensate you for shipping, etc.
@n80 - No need for shipping costs to you, only a mailing address. You only cover the return postage(USPS’ smallest prepaid box), if you don’t want to keep them them in your system. No strings!
rodman99999....that's very nice of you!  Those are very decent tubes, so @n80 should hear an improvement with those.

I love this community!
@mofimadness : Very nice indeed. I am often taken aback by the kindness of folks I don't even know. I hope to be able to pass on such kindness in the future.

Now I am a little worried about whether I will hear a difference or not as I don't have a lot of confidence in my ears. I will have my wife listen with me.

@rodman99999 : I have PM'd you my address.

Now that I'm actually going to get to try tube rolling I have some questions: 

Access to the internal of my LS-16 is easy. Just a few screws. I'm assuming the removing and replacing these types of tubes is just a straightforward firm pull up to remove and firm downward pressure to twisting or locking?

Wear gloves to keep oil, etc off the tubes?

When I Google tube changing the issue of biasing comes up, mostly with guitar amps. Is this something I need to worry about with my pre-amp? The manual does not say anything about that.

My pre-amp uses four tubes. Someone said above that I should be able to tell some difference with just two but I'm not sure where to put the two replacement tubes. The layout is like this:

          V1   V2
          V3   V4

Apparently when new the tubes are actually marked V1-V4 for exact location.

If I hear a difference with two will that difference by more pronounced with a full set of four?

If I like what I hear with two of these tubes and decide to get two more how precisely do they second two need to be matched with the first two? Is it okay to buy the same brand and designation or will they all four need to be tested and matched?

Sorry for questions that might seem obvious but this is new to me.


The tubes that the LS16 uses are 9 pin.  Once you turn the tube over, you will see that there are in a circle pattern with a gap between.  Align that gap with the gap in the tube socket and push down firmly until it seats.  I usually will put in and pull out a tube several times to make sure that if there was any residue on the pins, it gets scraped off with a few rotations.

I wear gloves, I was always told that the oil from your fingers will make the tube burn uneven, but Kevin Deal, (probably knows more about tubes than anyone I've meet), says that's bunk.  I still wear them.

You do not normally bias a preamp tube.  So no worries.

This is me, but I would always replace all (4) tubes at one time and all need to be the same.  Yes, there are exceptions, but mixing tubes in this matter, often leads to poor performance.  (I am talking about the OP's ARC LS16 preamp and nothing else because I know that it can vary widely, but this pertains to the LS16).

So yes, get the tubes as close to each other as possible.
@mofimadness : Thanks. I also have some deoxidizing spray that I used to clean and repair the pots on my old receiver. Should I apply this to the pins?
I also have some deoxidizing spray that I used to clean and repair the pots on my old receiver. Should I apply this to the pins?

I have always been told not to do this.  I tried something many years ago and it ruined not only the tubes, but the tube sockets had to be replaced.  I don't remember what it was, (might have been "TWEEK").  I'm sure others have had different results...
What I have is DeOxit. Probably no reason to use it if the pins look good.
There’s no need to match all four, only two between channels(ie: V1 closely performance/readings matched to V2 and V3 needs to match V4).  Nor do tube manufacturers need to be the same, between V1/2 and V3/4. ie: If you like the warmth/sound of whatever two tubes you’ve installed(ie: say these Amperex, in V 1/2), and don’t want any more warmth, you’d want to find a tube that adds no more warmth, or- just leave the original pair alone(in V 3/4). When there are multiple tubes, in the same circuit/channel, it’s common experience, that using different tubes will reinforce the better qualities of each tube and minimize the weaknesses. I’ve not heard of the LS-16’s circuit responding differently(personally). Gold does not oxidize and I’d appreciate it, if these pristine gold tube pins weren’t repeatedly pulled in and out of a socket. Installing them, in either the two positions/sockets closest the rear, or the two closest the front of the unit, should tell you what you need to know. A two-fingertip grip, as close to the base of the tube as possible, pulling straight up and two at the top, pushing straight down, has always worked for me(no bent pins or widened sockets). A cotton glove or sock(pulled over the hand), would be nice/can’t hurt(it’s what I do). I’ll have them on their way to you, tomorrow.
@mofimadness - Was it Kevin, that mentioned having all four of your LS-16’s tubes matched? If so- did he elaborate? Just curious(he does know his stuff).
@rodman99999 : "Gold does not oxidize and I’d appreciate it, if these pristine gold tube pins weren’t repeatedly pulled in and out of a socket"

Got it.

"Nor do tube manufacturers need to be the same"

Wow. That opens up a lot of tuning possibilities.
Was it Kevin, that mentioned having all four of your LS-16’s tubes matched? If so- did he elaborate? Just curious(he does know his stuff).

No, he never said anything about the LS16.  That's just my opinion, just like your opinion on mixing and matching.  I think, that on this preamp, it's not a good idea, but again, it's just my opinion.  I was only an ARC dealer for many years and have owned almost all the preamps that they have made, but, again, this is my experience only.

Some of the older tube preamps benefited greatly from mixing and matching, so it really depends on the circuit.

@n80...Nothing wrong with trying, just don't drive yourself crazy.  Yes, it can and will happen  :-)
@mofimadness - OK(thanks for that). Owned an SP-9 and an SP-11, which were both a ton of fun, to tweak, in various ways. My son wound up with the 9. Never had heard that, regarding the 16 and wanted to be certain, I wasn’t missing something. It’ll be interesting/informative, when we get n80’s input(I hate the word, "feedback"). Happy listening!
To be clear, there is no harm to the unit in using different brands (in pairs as mentioned above)? If I broke this thing I'm sure I'd have a hard to paying for repairs!
No harm will come to your preamp, but- if you’re having second thoughts, please- let me know before morning. Then again, call ARC and ask them. I won’t send the tubes, until I hear back from you. No problem.  Their number:   763-577-9700

To be clear, there is no harm to the unit in using different brands (in pairs as mentioned above)? If I broke this thing I'm sure I'd have a hard to paying for repairs!

There is absolutely nothing you could do mixing and matching tubes to damage your preamp. 

I'd sure take rodman up on his offer.
@mofimadness : I have. Can't wait to give it a try. Already looking for 2 more of those tubes just in case I really like them and want to have all 4 the same.

I've run into a couple of things though. One source says these were counterfeited for a while. I see them on reputable sites for $150 - $200 each. I see them in pairs on eBay for $150. See some individuals on eBay for $45.

Just guessing the eBay offerings are probably not the way to go.
I've had good luck on E-Bay, but I've heard horror stories also.

Here are a few of the top rated tube dealers:

Brent Jesse
Upscale Audio (Kevin Deal)
The Tube Depot
The Tube Store
Jim McShane
Vintage Tube Services (Andy)
There are more, but these seem to be discussed the most.
@rodman99999  : "if you’re having second thoughts"

Oops, sorry, I didn't see this post. No second thoughts at all. Really looking forward to trying this.
ALRIGHTY, THEN!  They'll be on their way, tomorrow.  If you like the sound of them, and you're serious, regarding another pair; these(below) are identical.  When you get my pair, compare them to the pics in this ad (better pics, than the eBay ad) .  ie: The halo getter, the getter support structure, the grey plates and shields, molded creases on top of envelope, gold pins, early Sixties date codes, etc.
@n80, as far as pricing, these tubes are $200+ for 1960s NOS.
They are premium military grade, made in USA, with white lettering (orange lettering cost less). Low noise and should last for years.

Just to give you an idea of pricing when you shop for a 2nd pair:
Brent Jessee offers...
E88CC / 6922 Amperex white PQ type, white label, USA made, gold pins.MATCHED PAIRS. $230.

The PQ version has the same sonics as the Amperex JAN. You may see a pair with one JAN tube matched with a JAN USN. They are the same tube, the USN was sold to the US Navy and are very rare nowadays.

A very generous offer by Rodman.

@lowrider57  : " A very generous offer by Rodman."

The more I research these tubes the more I realize that!
"I’ve had good luck on E-Bay, but I’ve heard horror stories also."

Horror story for me - got curious to try something new after listening to Mullard 2492s. So bought some Amperex Bugle Boys on ebay that fried my pre’s power supply as soon as I powered it up. Ebay seller refunded my purchase but repair was my problem. Between shipping back and forth to the only guy in the U.S. who does repairs on Symphonic Line and parts/labor, it set me back $600.

Eventually bought Telefunken E88CC’s from Kevin Deal to satisfy my urge to explore upon his recommendation, and they’ve been in for the past 5 years. One tube went wonky a month after I bought them and was replaced gratis, and another one went weird about three years ago so bought a replacement. Neither tube claimed any additional victims. I don’t know about lasting 10,000 hours, but they must have 5,000 hours on them and still sound fine.
" You may see a pair with one JAN tube matched with a JAN USN. They are the same tube, the USN was sold to the US Navy and are very rare nowadays." Mine are marked for Joint Army Navy(JAN-CEP) and NAVY (6922) contracts, from ’62’ and ’64. They were last tried(taste tested) in my BAT VK-D5(a $4500 investment, then), without incident. I’ve no doubt, shorted tubes could cause all sorts of havoc, depending on the circuit design/protection. These aren’t. They weren’t nearly as salty, 17 years ago, either(maybe half the current cost). They’re on their way!