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6V6 EH upgrading to NOS RCA. What should I be expecting?

kingdavidy2k

Member
Messages
2,259
im looking to upgrade the EHX 6V6s on my Princeton Reverb (12" Celestion V-Type Speaker, Vibroverb OT, DR PT).
The preamp section has already got NOS tubes:
From V1-V4:
RCA Long Grey Plate 12ax7
Mullard CV4024
Tungsram 12ax7
Telefunken 12ax7.

What should I hear differently if I upgrade the EHX to NOS RCA relabelled to Sylvania VT107a?

As I have a friend who's selling a matched pair.

Should I get it or won't it have much difference to the EHX?

Many thanks,
David
 

DaveKS

Member
Messages
16,704
Power tubes usually not a profound change like preamp tubes can be. But RCA are coveted 6v6 for a reason. Probably just nice little bump in richness and harmonics if you OD them.

Don't know what he's asking but you'll usually get at a minimum 5x the tube life if not way more, but depends on how hard you push them. If it's a good price for matched set try em' I doubt you'll be disappointed unless their bad.
 

Blue Strat

Member
Messages
30,192
First thing you should do is have a competent source verify that those are actually RCAs. I doubt they are as I've never seen that particular relabeling in my inspection of over 120,000 tubes. Those 2 items look very similar until you compare the top mica spacers.
 

RussB

low rent hobbyist
Messages
11,158
A lot will depend on just how used up those tubes are. Are they truly NOS or just old tubes?
 

kingdavidy2k

Member
Messages
2,259
First thing you should do is have a competent source verify that those are actually RCAs. I doubt they are as I've never seen that particular relabeling in my inspection of over 120,000 tubes. Those 2 items look very similar until you compare the top mica spacers.
Here's the photo of the 2 tubes: 2 in the middle

Do they look like RCAs?
 

Snakebite

Member
Messages
13
It would be very interesting to know just why your friend believes that these tubes, which say Sylvania, are in fact RCA. I'm NOT saying that they aren't, just that I've not heard that one. Also, the term Matched Pair is greatly over used. Very few people have the means to match tubes properly.

First off, you need to have large numbers of tubes on hand from which to select from. You need a quality Mutual Conductance tube checker to find tubes that have a balanced conductance factor. Then you need a good test circuit and a means to measure the idle current through each tube under a fixed situation so as to find tubes that have a balanced current flow. The best you can get is to actually use the amp that they are going to be used in for your testing. After you do all that, then you can know that you have a set of Matched Tubes. I had a very large stock of New Old Stock tubes... many civilian tubes and large quantities of Military stock tubes. I was able to truly match up tubes. The other way is to buy them from a reputable dealer who has access to the needed stock of tubes, the equipment, and the know-how to match tubes.

As for what to expect.... if the tubes are as you believe, then they should sound good. For a given bias set... they should have a bit more Head-Room than the EH tubes that you have been using. If the bias is set a little on the cold side the tubes should last you a long time... but most folks end up setting them a little hot. They do have a higher rating than the EH tubes and will handle a bit more dissipation. The RCA tubes are indeed a good tube... but IMO, a good set of NOS Phillips tubes from Military stock sound just as good, and you can buy them for a much better price ... you can also get a good sound out of some JJ 6V6S tubes. I must say that my preference is toward more headroom than many folks.. I'm an old guy, and don't do as much distortion as some folks do.

Just the view from my saddle pard.

Snakebite
 

Blue Strat

Member
Messages
30,192
No two of those tubes are the same and none of them are RCAs. The brand markings on them are accurate.
 
Last edited:

Blue Strat

Member
Messages
30,192
It would be very interesting to know just why your friend believes that these tubes, which say Sylvania, are in fact RCA. I'm NOT saying that they aren't, just that I've not heard that one.
Rebranding has been very common throughout tube history. Understanding what to look for INSIDE the glass is the only way to reveal the real identity of the manufacturer. RCAs branded as something else is extremely rare, much more so than the other way around.
 

logdrum

Member
Messages
2,116
Rebranding has been very common throughout tube history. Understanding what to look for INSIDE the glass is the only way to reveal the real identity of the manufacturer. RCAs branded as something else is extremely rare, much more so than the other way around.
BlueStrat,

I have pulled pairs of 6V6 from junked Hammond M2's (so OUS - Old Used Stock). They both say Hammond and RCA. Could they possibly be not RCA's? Is there a page with pictures to verify?

Anyway to the OP - my experience is limited to the Hammond-maybe RCA and Brimar 6v6. The difference is when you overdrive the amp. In fact the newer ones may be have more sparkle low volumes but would fizz out if you cranked the treble and flub out when you push the bass, the old ones would not do that. When cranked you have soft clipping and the bass remains tighter longer and gradually crumbles instead of farting out. I hope you get the picture I have tried on both a Mesa Blue Angel and on the Mesa Heartbreaker.
 

Blue Strat

Member
Messages
30,192
BlueStrat,

I have pulled pairs of 6V6 from junked Hammond M2's (so OUS - Old Used Stock). They both say Hammond and RCA. Could they possibly be not RCA's? Is there a page with pictures to verify?
That's a special case. Those would be RCAs. The cases we're talking about in this thread don't involve OEMs (like Hammond), the involve only tube manufacturing names.

There are photos all over the net. I don't think anyone's interested in devoting time and energy to provide specific, free, information that involves no revenue.
 

kingdavidy2k

Member
Messages
2,259
The difference is when you overdrive the amp. In fact the newer ones may be have more sparkle low volumes but would fizz out if you cranked the treble and flub out when you push the bass, the old ones would not do that. When cranked you have soft clipping and the bass remains tighter longer and gradually crumbles instead of farting out. I hope you get the picture I have tried on both a Mesa Blue Angel and on the Mesa Heartbreaker.
Yes this is what I found as well with rolling tubes for my Top Hat Club Royale.
I find I like New JJs better at low volume and found NOS tubes sounds a bit dull. But with the master wide open, those "mellow" attributes of NOSs really does it magic (soft clipping, no high end fizz, tight yet crumbly bass).

It's easy with my Top Hat cause it doesn't need any biassing with rolling tubes.

Maybe the best way to go for my Princeton is to first get a bias probe as it's got a bias pot. That way I can just put EH back if I don't end up liking the NOS.
 

RussB

low rent hobbyist
Messages
11,158
Yes this is what I found as well with rolling tubes for my Top Hat Club Royale.
I find I like New JJs better at low volume and found NOS tubes sounds a bit dull. But with the master wide open, those "mellow" attributes of NOSs really does it magic (soft clipping, no high end fizz, tight yet crumbly bass).

It's easy with my Top Hat cause it doesn't need any biassing with rolling tubes.

Maybe the best way to go for my Princeton is to first get a bias probe as it's got a bias pot. That way I can just put EH back if I don't end up liking the NOS.

A NOS tube dull compared to a JJ?

When you say "NOS" are you talking about NEW tubes or just old tubes?
 

kingdavidy2k

Member
Messages
2,259
I should say less sparkle at low volume. Definitely not dull.
The NOS I'm referring to is Phillips Miniwatt EL84. Maybe that model is particularly have less high end?
 

RussB

low rent hobbyist
Messages
11,158
I should say less sparkle at low volume. Definitely not dull.
The NOS I'm referring to is Phillips Miniwatt EL84. Maybe that model is particularly have less high end?


I don't know why, but I thought you were talking about 12AX7's. Sorry for the confusion
 

Blue Strat

Member
Messages
30,192
He said that the construction is the same as the RCA and he sent me this as his base as well:
Whoever "he is" is wrong. Anyone can see that the top micas are different. If you could see through the gray coating, you'd see that the plates are completely different too.

This doesn't say that they're RCAs. He says "look and sound the same" which is a subjective claim. If anyone is saying that any of the tubes in your photo above are made by RCA, they're 100% wrong.

Sometimes you get what you pay for. In fact, if the price listed above was for any 2 of the tubes in your photo, you got less than what you paid for.
 

ripgtr

Member
Messages
9,688
I have RCA 6v6s in my SFDR
Before that, I had Tung Sol "reissue". which are the same factory as the EH tubes, I believe.
I did some testing, recording into the daw, then re-amping.
Setting the bias on each set of tubes and recording, then comparing. Listening and using analysis tools.
The difference was not huge between the TS and RCA. The TS was a little more compressed, the RCA a little nicer on the top end, but it was minor.
I like the RCA and I have them and left them in.
Power tubes don't make a Lot of dif in the sound, if they are working correctly and biased correctly.
Longevity is supposed to be an issue with new tubes. I never really had an issue with the new ones, now the old ones are in the amp and will probably outlast me, so ...
So, don't expect a huge difference all other things being equal.
 

kingdavidy2k

Member
Messages
2,259
Whoever "he is" is wrong. Anyone can see that the top micas are different. If you could see through the gray coating, you'd see that the plates are completely different too.



This doesn't say that they're RCAs. He says "look and sound the same" which is a subjective claim. If anyone is saying that any of the tubes in your photo above are made by RCA, they're 100% wrong.

Sometimes you get what you pay for. In fact, if the price listed above was for any 2 of the tubes in your photo, you got less than what you paid for.
Thanks for your input Blue Strat.
I think I'll pass on the offer from my friend and look for an actual RCAs.

What I'm looking for is something with tight bass, soft mids, and shimmery top end. Something with a lot of clarity.
I don't overdrive my Princeton. I set it around 3 at home, 4-6 for gigs/rehearsals.
I get my drive from pedals.
Is the RCA right for what I'm after or would you suggest something else?

Many thanks
 




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