Tube Rolling - No Change in Sound

In my Wyetech Opal pre, I substituted NOS Ken Rad VT231's for JAN Philips WGTA's in the input stage, expecting more body and warmth to sound based on Ken Rad reputation. But nothing has happened; I perceive no audible difference from the switch in tubes! What's up with this? This was my first foray into tube rolling.

It could be that you are experiencing the 'weakest chain' issue..that another component is not good enough to reveal the subtle upgrade in another.

Welcome aboard, good luck and God Help you [(:>}
It simply may be that your vt-231's and the new wgta's have a relatively similar sound signature. Now if you had tried a tung sol 6sn7gt round plate or a Sylvania 6sn7w I believe you might hear a difference. Also however, one has to consider that some preamps are not so responsive to tube rolling as others. I have a deHavilland Ultraverve which relies on the 6sn7 tube. Each tube I try sounds unique and different and it is very apparnent each time I roll in a new type. I have tried about every NOS 6sn7 tube out there. I like the RCA vt-231 grey glass, the Sylvania 6sn7w, sylvania 6sn7gt, Raytheon 6sn7wgt...but for overall performance across the spectrum the Tung Sol round plates are hard to least for my pre...but they are expensive and disappearing quickly.
There are four possible explanations.

1. The circuit design of your Wyetech Opal may not be particularly sensitive to variations in tube parameters.

2. While the internal tube design characteristics of the same tube from different manufacturers can vary, it doesn't mean they always do. Your Ken Rad and Philips may have been closer in characteristics than some other combination.

3. There was a difference but it is masked by other aspects of your system.

4. There was a difference but you may not be particularly sensitive to it. Different people listen for different things in music and the change resulting from this tube switch may simply fall in an area that isn't very high on your list of sonic priorities.

It could also be a combination of more than one factor noted above. There are also subcategories (you needed longer burn-in or more listening time/different music in order to hear subtleties, etc.) but you get the idea.

The primary point should be you have tried it for yourself. Even though someone else may have different results from the same experiment is ultimately irrelevant for your situation.
Excellent answer from Mlsstl.
Don't know who told you KenRad VT-231s would add anything to your sound. They are a very transparent tube, adding/taking nothing from the signal(as are the TungSol Round plates, Sylvania VT-231/6SN7GTs and 6sn7Ws). Raytheon, National Union, and RCA VT-231s will all give you a bit more of the sound you're looking for, to various degrees. They are all a little euphonic(warmer) than the others. I've got three matched NOS pairs of the KenRads, for when I can't find(or afford) the TungSols and Sylvania 6SN7Ws that I love so dearly(for the above mentioned reasons).
Msstl's number one response is probably right on...I would have contacted the MFG and asked what tubes in the unit respond most to rolling...just changing tubes out doesn't always change the sound...the KRads are great BTW
Well, trounce me if you want, but I still STRONGLY maintain that the sonic signature of any system is at least 85% determined by the amp and speakers. As for preamps, I think one thing you WILL get out of tube rolling is (maybe) a quieter/lower noise floor (depending on the tube you select.) This is certainly true for tubed phono preamps. But the amp is where I'd look to effect tonal changes through tube-rolling.

Of course if you have a solid state amp, you're going to get the detail and slam for which ss is well known. But if you don't like the sonics, you'll have to roll the whole amp!
Of course if you have a solid state amp, you're going to get the detail and slam for which ss is well known. But if you don't like the sonics, you'll have to roll the whole amp!

Nsgarch (System | Threads | Answers)

I laughed at that! Good one Nsgarch :o)
>>I still STRONGLY maintain that the sonic signature of any system is at least 85% determined by the amp and speakers.<<

IME it's difficult to assess the performance of either component without consideration of the other. The same analogy can be applied to tonearms and cartridges.

That being said, I believe that speakers have the strongest influence on a system's sonic signature followed by sources not the amplifier.

For once, a thread where everybody is right!

FWIW, I have been able to get pretty significant changes in my rig's sound by rolling 6dj8's in a number of different preamps in driver and output stages. The Kenrads definitely added some of the "fat tone" flavor vs. other tubes, especially in an Atma-Sphere MP3, which is relatively good at allowing you to hear the differences in various tubes. Cheers,
I rolled 6922's and experienced little change; however I rolled some 12au7's and experienced dramatic change. They were NOS 50's vintage, this was in a CJ.
Thanks for all the comments. I am not sure I am any more illuminated than when I began, given the diverse views, but I suspect the observation that the pre may not be sensitive to tube-rolling may be the most accurate -- at least with the KenRads. (FYI, my amp is a Krell FPB 300cx.)I wonder if more extensive burn-in (these are NOS tubes) will effect a change. Time will tell.

Thanks again.

Ken-Rad VT231 has been known to deliver excellent bass and sweet mids. Sounds like you didn't get any of that! Well, at least, you will probably be able to easily sell them.
Sure sources (and preamps) affect sonics, but with them, it's basically "what you buy is what you hear" -- they are what they are. The reason the amp+speaker=primary system sonics is because:
A. Once a signal is created (by a source) the amp processes the signal (multiplies it by a huge factor) more radically than any other device (even including equalizers!) A line preamp (not a phono preamp) is really a signal switcher + a buffer stage; it selects a signal (source) and then optimizes it for driving an amplifier; but it doesn't really alter the signal that much; not compared to an amp!
B. The speaker (and the speaker/amp interface, AKA how much the amp likes the speaker it's driving ;-) is the other major factor that determines a system's sound character. Don't tell me about the room treatments, and the cables, and the temperature and the altitude ;-) they're all important. Nevertheless, you can do anything you want upstream, but horns, stats, cones, domes, ribbons, buttons and bows! each have their own unmistakable sonic character -- and you can't make one sound like any of the others (not by any legal means ;-)
I don't know if I agree, in my system amps have made the least difference, speakers the biggest difference by far - then source followed very closely by preamp and lastly amp.

I do agree without question the amp/speaker interface has to be optimal or close to it or you can throw everything out the window.
I am an inveterate tube roller and some circuits will not respond to tube changes.
I tried to cool off a highly modded ARC SP6B pre amp. It already had the reputatation of "legendary gain gone wild." You can't simply swap lower mu tubes to get a more viable midrange and travel on the volume pot. It takes 12AX7s x 6 and only Only 2 are in supposedly real meaningful gain positions.
Try as I might for example with top of the heap 5751s -some real low mu 12AU7s, those almost passed enough current to burn up my spoeaker's voice coils, the amp seemed to care less.
The only result was a change in tone with very, little if any perceptable change in gain
I know it is purely anectdotal and can't hold a candle to the concise asnalysis above. The technical answer is the cathode follower bleeds freely into a leak grid intended to dissipate and not redirect the amplified electron velocity. A very loose lowest impedance pull if you will on the the gain. The other tubes are phase splitters/inverters which have no gain function except as input tubes. That is a matter of keeping the input signal at a predertimined voltage. This is required for the rest of the pre to "hear" the signal.
Now I am going to roll some 6SN7s yes Rodmann even though I have many inluding 4 pairs of TS RPs and Ws tall and short metal bas or black. I also have a few Kentucky Radio , National Union including the gray and several black but today I think I will try TS WGTs - NIB pristine NOS. I am not sure what they will sound like a priori.
Wax, cotton swap
I had not seen that your power amp is a Krell. Indeed theb Ken Rad has a well deserved reputation for bass energy and bass energy. The JAN Phillips WGTA is a quick more transparent 6SN7 and tends to be fairly neutral to thin. I have come to the conclusion that your amp is simply overwhelming the sonic signature of your system. In essence the Krell is going to give you all the bass your speakers can make. No tube is warmer than a Ken Rad and it does not matter if it is a VT 231 a clear glass GT a black glass GT staggered or striaght plated they are either exactly the same tube or have the circuitry that maskes them sound identical. See TubeSeller's site it's a bit old but he and Len Ho agree that there is no real difference. Also check out the permanent 6SN7 thrtead on
Thanks, Mechan. I don't really agree that the Krell is overwhelming my system, or that it is giving all the bass my speakers can handle. Prior to the Wyetech Opal, I had a Hovland HP 100 pre, which was very nice, but the Opal is a big step up and led to both an increase in the depth and tightness of bass. I have had similar results when swapping IC's, PC's. And as the KenRads burn in I am noticing (or at least think I am) a perceptible increase in what I would call the "naturalness" or body in the sound: vocals sound a bit more "real", instruments more true. But it is not a dramatic change from the Philips..

I may move the KenRads from the input to output stages and see if there is any difference.

I had just read that the Ken Rad was essentially the same construction as the archetype flat plate 6SN7 which is the RCA GT. Personally I find the idea understandable if you take the construction by itself. Yes they look alike but that is the extent of it otherwise they sound nothing like eachother. I have heard that a good number of 6SN7 fans find that RCA, in particular, the Grey Glass VT-231 JAN CRC a very "lush" and rich sounding tube.
I can't hear that at all from any of the RCA tubes except for one exception. The 5692 special Red Base long lived if low biased 6SN7 sub. That tube also an invention of RCA. It is often repeated that all and any 5692 that you find no matter how labeled is an RCA product, (not true). While I find it a bit to undefined to be all that great to my ears it is a well respected tube with a devout following willing to pay more for it than all other 6SN7s. The cost remains high but only in the last year or two the Sylvania "W" or it's predecessor the "A" with the JAN CHS 6SN7W metal banded basel and the Tung Sol round plate VT-231 or CTL at this juncture will cost as much or more, to buy very different sonics.
The 5692 will bring a smooth, softer sounding presentation which I attribute it's velvety fuller tones and slower decay (better timbre) but it lacks the definition and IMHO lacks the refinement of the W. The 5692 just doesn't come anywhere near the extension and slam of the Tung Sol or the W.
To be perfectly honest the humble Green letter just no coin base please Sylvania GTB has a Bing Crosby sonorous baritone equal to most of the fancy pants tubes. It is bettered by others in terms of quickness and precision Hytron, National Union- Black glass not grey, the overall fire of the W like JAB CHS WGT not WGTA but some parallel constructed boxed "T" plate Sylvania GT-As are essentially more voltage tolerant higher dissipating Ws just to confuse you. The number of possibilities are enormous but get horribly expensive if you include the CV181 from Great Britain with the Brimar 6SN7GTY made for export ECC32 or a holy grail MOV B65 pair costing about $700-800. The softer and fuller toned tubes to try are the one time king of the hill RCA Red Base the earliest being the best and high guarded from microphony which plagues them all. The Grey glass NU which you really have to hunt down, Other 5692s the Mullard CV181.
Good Luck shoot me an e-mail I can tell you who has themm if they have any. Etc. Cheers