I need to replace the tubes in my Rogue 99 line preamp, which uses the 6SN7 tube. I was looking at an online seller who offers the following options with an affordably priced 6SN7 for a few dollars extra:
1. Balanced Triodes 2. High Gain 3. Low Noise and Microphonics 4. Matching
Options 3 and 4 seem most desirable for a preamp. My question is whether it is worth the extra few dollars (approx. $6 per tube) or is it just a pure marketing ploy to get suckers like me to drop more dough?
Multimeter will not do the job,you need a good Tube Tester that can measure transconductance and plate current besides shorts,hum,noise and microphonic.
Thank you all for your responses. I don't even own an multimeter, but as Al advised I'd leave the job to someone who knows what they are doing. Sounds dangerous for an amateur...
You are looking for a platinum matched tubes which are balance in Gm & Ip, non-microphonic and very low noise.It's worth the money if your gear is in push pull configuration,but if it's in cascade,you just need a very low noise and non-microphonic.
There are octal adapter with all pin out, with your amp/preamp switch off,plug the adapter and plug your tube on top of the adapter.Use alligator clip on your multimeter's volt AC and clip them the pin 7 & 8.switch on your equipment and if the reading is about 6.3 volts?that is correct.but if the reading is not 6.3~ ,switch off and turn your meter to dc volts.Switch off your gear before removing those clips.6.0 to 6.7 is normal for tubes with 6.3 filament.
The filaments of a 6SN7 are on pins 7 & 8. If the supply is DC it is probably regulated and spot on unless there is a problem. AC supplies generally depend on the incoming line voltage. If it is consistently high then the filament voltage could be too.
It would have to be checked by touching or connecting the probes of a voltmeter (or a multimeter set to measure volts) to the filament pins of one or more of the tube sockets, under the chassis, or to some other circuit points that are connected to those pins. (To assure a meaningful result the measurement should be done while the tubes are in their sockets, as opposed to removing the tubes and accessing the socket pins from above the chassis). Lethal voltages will be present on some of the other pins on those sockets, as well as elsewhere under the chassis. And if the probe tips were to momentarily come into contact with two adjacent pins simultaneously damage to the component may occur. So it’s a task that is best left to a qualified technician.
Also, regarding the references to 6.3vac and 7vac, many designs provide dc voltages to the tube filaments rather than ac. In those cases, of course, the meter function should be set for dc volts rather than ac volts, and the probes should be connected with appropriate +/- polarity.
I'm a bit frustrated as I've had to replace the tubes just about once a year even though I listen on the weekends only,
Check the filament voltage. If it's much more than 6.3vac then you will need modify your unit to lower the voltage. I have a Sun SV2A3 that was eating 6SN7s and the filament voltage was ~7vac.
+1 for Brent Jessee. I've bought a fair amount of stuff from him over the years. I've also had some good luck with tctubes.com. Four years ago I got an out-of-production NOS Philips JAN 6X5WGT rectifier for $21 + $5.50 s&h from tctubes.
I would also check out Brent Jesse as a tube source. He is honest and prices his stuff reasonably. Has a whole section on the 6SN7 and variants. He usually carries a Baldwin labeled tube which looks and sounds identical to the much more expensive Sylvania chrome top. I have had good results dealing with him over a number of years.
A good 6sn7 with transconductance and plate current within 10% or less triode-triode ,and at least 30% higher than the minimum,not microphonic and low noise is a good candidate bu do not compare brand of 6sn7 tubes if their Gm & Ip are not within 5% of their tested reading Gm & Ip brand-brand since brand with higher test reading will always be on top..
FWIW we find the Tung-Sol tube to be just as unreliable as the EH tube. Both are made in the same plant and the big difference is the color of the base.
Only 2 of the 4 6SN7 tubes have any sonic impact. I can't remember if they are the right 2 slots or left. You can save money buying 2 cheap and 2 vg tubes. I don't think any have to be matched.
"Why don't you call Rogue and purchase exactly what Mark O'Brien, the gentlemen who designed the piece would suggest instead of listening to all the patrons in the euphonic coloration."
Because no two people hear the same or have the same idea of what neutral is. Why do you think there are so many different brands and models? Should we all own the one true neutral system?
It looks like you've done a lot of tweaking to your system, why shouldn't the OP and the rest of us be allowed to do the same? I'm for people listening to whatever the hell they please without getting anyone's approval.
Cdrc, I agree with you only in the sense that there is no reason to expect that tubes purchased from two different reputable sources will exhibit different wear characteristics. As for "euphonics", tubes of one brand do indeed sound different from the same tube type built by a different company, albeit the differences are usually subtle. Thus, one man's "euphonic" is another man's "neutral", and the debate on that can go nowhere. But the reasons for differences in sonics among different 6SN7s are not hard to fathom, if you take a good look at the differences in internal structure and in materials used. Further, how the tubes are used in circuit will also contribute to the apparent sonic character that is attributed to the tube per se.
I always contact Mark and Nick at Rogue first if I have any questions regarding their product. I did so in this case as well. Rogue always offers one of the best customer service experiences in the industry. Nick informed me they no longer us the EH 6SN7 tubes because they found them to be too unreliable, and use Tung-Sol now. I wouldn't expect them to say much more since they probably use new stock tubes for new products to offer the best value to the consumer. I bought a set of 6SN7s from Rogue a few years ago that looked like NOS, but they also lasted about a year with moderate use so I thought why not try something different this time. Perhaps Lewm's suggestion is worth looking into as well.
Thank you all for your responses; I've learned something, as always on here.
Whatever you do don't buy from Matthieuriverin from Quebec. He does not stand behind his tubes when there is an issue. There are more folks than just me that have had issues as well. Buy from Andy or the tubestore.
There is a lot of lore built up around the various brands and types of 6SN7s. Most of all, if your Rogue came with GTA or GTB types, stick with either one of those types. (They have the same max plate voltage of 450V, whereas the GT types are only recommended for up to 275VDC, if my memory serves.) The vendor you asked about seems to be well thought of, so go ahead and spend the extra money, is my advice. But keep in mind that selecting for low noise, balanced triodes (presumably this means that the two triodes in the single glass envelope are balanced vs each other), etc, does not mean that the tubes will necessarily last any longer, which seems to be your main beef. And also keep in mind that 6SN7s are unfortunately prone to go microphonic over time before they die. If you're wearing out tubes prematurely, perhaps Rogue or some competent tech can check the voltages in your unit; maybe there is an issue.
I bought a pair of GE 6sn7gtb's for around 50 dollars that sound very good from top to bottom. They didn't take long to break in and are an excellent value. I didn't buy from Andy.
Thank you, Al and Ralph. I was actually looking at the Sylvania tubes, but this particular era looks a little bit out of my budget. Circa 1970s is very reasonably priced, on the other hand, and I'd think probably better than any new stuff on the market.
Ralph (Atmasphere) beat me to it, as I was just about to post the same comment. The GTAs and GTBs are rated to handle considerably higher plate voltages and power dissipations than the GTs.
But be aware that there are some current production (not vintage) tubes identified as 6SN7s, with no suffix, which meet GTB specs, at least supposedly.
Regarding the original question, I would go for matched/balanced/low noise/etc., as that could very conceivably make a difference.
Also, FWIW, I've been very pleased with ca. 1950s Sylvania 6SN7GTBs in my amp, which I believe requires GTAs or GTBs.
There are three kinds of 6SN7s: GTs, GTAs and GTBs. If the circuit needs one of the latter two and you have been installing GTs, they won't last very long. GTs don't handle as much voltage.
We've been recommending Andy for decades- he is an excellent source.
Thanks everyone. I'm a bit frustrated as I've had to replace the tubes just about once a year even though I listen on the weekends only, and my understanding is that the 6SN7 is one of the most reliable tubes and should last longer than that. Sounds like I should give Andy a call.
Andy is great. But, has top-notch NOS tubes...is expensive...knows he is expensive... and thinks he is worth it - having bought $1k worth of tubes from him, so do I. By all means, get a price. However, for someone who is concerned about $6 and has a $1k -$2k preamp, it may be a better recommendation to more directly answer your question with, "Low noise and microphonic, and matching". Additional consideration- The Tube Store , new tubes mainly, and online audiogon Quebec vendor, "Mathieuvarian", NOS, have proven themselves as well.
Definitely low noise, low microphonics. Matched tubes not so important in a preamp, except for the possibility that the 2 tubes being tested and having close specs may result in a similar life expectancy.
No way to know in advance if it's worth it. If you got a noisy or microphonic tube and had to return it you'd be out the $6 anyways. I'd definitely go for tubes culled for noise and microphonics. Matched pairs maybe not so much but then again I'm not an imaging freak.
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