NOS Tube Recommendation for Quicksilver Phono Pre Amp

RCA Clear Tops.

Buy from Andy at Vintage Tube Service 

@onhwy61 gain (mu) is one of the differnces. there are more, and all are significant. 5751 is not a drop-in substitute for 12AX7. they are not interhangeable. any such substitutions are circuit dependent. check with the builder, manufacturer, designer to find out what substitutions are ok. 

@larryi , I'm embarrassed that I didn't know this (I only upgraded from a vintage console ~1 year ago, so I'm still steep on the learning curve). The worst part is, my TT is only ~2 ft from the phono stage on the same rack! I was using that ridiculously long cable (originally bought for my R2R which is across the room) because the cable I ordered specifically for my new QS phono stage hasn't arrived yet (it should be here tomorrow according to USPS tracking). 

Last night, I took that long cable out and swapped in the 1M Raven Audio Soniquil RCA interconnect cable I was using for my Cassette deck. The sound INSTANTLY improved. A LOT. The invisible wool blanket over my speakers is gone. 

I'm still interested in rolling the tubes at some point, but the urgency is gone. I think I'm going to start with switching the input tube to a Raytheon/RCA 5751 with windmill getter or the GE 5751 triple mica. When I finally pull the trigger, I'll update this thread with the results, but for now, I think the problem has been resolved.

Thanks again for all the help

P.S. kudos for identifying the correct issue early in this thread... you had the right idea all along!!

@crawfishdaddi

Thanks for the information. The model I have calls for all AX7 tubes. I use both 5751 and AX7 type tubes!!

The sound issue you mention DOES sound like a loading issue which will have a much bigger impact on sound than would tube choice.  The VERY long cable to your phono stage would add a lot of capacitance.  The best thing is to find a way to locate the phono stage nearer to the table; a long run from the phono stage to line stage or the amp will be far less of an issue than a long run from the table to the phono stage.  If you must have a long run from the turntable, you should be looking for the lowest capacitance cables and you should make sure the phono stage is not set to add anything additional.

@yogiboy, here is the tube layout diagram from Quicksilver’s website (input tube should be the 12AX7 closest to the RCA inputs, gain tube should be the other 12AX7 and the cathode follower is the single 12AT7):

@crawfishdaddi I have that preamp. The only tube location that is labeled is the gain tube. Can you please tell me where is the cathode and the input tube position located?

Thanks!

While some of the more “famous” NOS tubes are still available the quiet ones that are needed for a phono stage generally are not. Most important, make sure you get tubes suitable for a phono stage. Unless you have VERY deep pockets I think you’ll find that most NOS tubes will be too noisy even though they’re advertised or you’re told that they are not.

Reach out to Brent Jesse. Most knowledgeable guy I know, and carries a HUGE selection of NOS tubes of all varieties https://www.audiotubes.com/

1. The 5751 can be substituted for the 12AX7, but ONLY in the input position. Using it in the gain position will cause the phono pre to not operate correctly.

By "not operate correctly" I am sure he means that the RIAA EQ will fall a bit outside of specified +/- error range. It will probably sound quite fine, for the most part, and at no risk of damage anywhere. But sure, it’s best to follow the manufacturer’s / designer’s recommendations here.

Ok, I just talked to Mike at Quicksilver and here is what he said:

1. The 5751 can be substituted for the 12AX7, but ONLY in the input position. Using it in the gain position will cause the phono pre to not operate correctly. 

2. As I described my issue, he was a little surprised and said that it is an unusual problem to have when using the stock tubes. He went piece by piece through my system checking input/output resistances (all check out). He finally said, "what cables are you running from the turntable into the phono pre?" When I mentioned that I'm still waiting for my Morrow Audio phono cable to arrive, so I'm using a high quality spare RCA that I had lying around for my Reel to Reel across the room, he asked, "across the room? how long is that cable?" 17 ft. Convo stopped there. "oh! the problem is most likely that cable!"

I had no idea how sensitive the MP-500 (and most MM carts) are to cable capacitance. If this turns out to be the problem, I will feel more than a little sheepish. I'll report back, but many thanks for all the replies in any case (I ended up learning a ton about tubes)!

thanks @mulveling  -great stuff!
I've never actually seen the fabled Mazda silver plate 12AX7 for sale anywhere... I'm starting to think it's only a myth. 

@crawfishdaddi 

OK, now I see you have stated the result seems a bit too warm. So you want something with a bit more "zing". In that case, you should check out the following:

• Mazda silver plate 12AX7 (expensive)
• Telefunken ribbed plate 12AX7
• (Russia) new Tung-Sol 12AX7

Electro Harmonix 12AX7 are fairly bright. I usually don't like them, but they can certainly counter warmth. Later Sylvania 5751 were also pretty bright, and I didn't like them - but who knows, here. 

RCA are weird - most are warm but some of them have been unbearably bright (and those tubes have been from Andy @ VTS with the cleaned pins; wonder if that's related).

If a phono stage has a strong "voicing" on its own, you are not going to fully counteract it with tube rolling. 

@onhwy61...I hear you (you and @dekay are not wrong). I've played about 15-20 records on the new phono stage and I am committed to waiting at least the minimum 30 hours of recommended break-in time before making any changes. 

However, I am getting my ducks in row and trying to learn as much as I can in the event that this coloration issue doesn't go away on its own. I also struggle with the idea that I should just keep waiting for months on end hoping for it to improve (I think a lot of time, people just get used to how it sounds whether it actually improves or not). 

I listen to records 3-4 times a week for a couple hours at a time. At that rate, I feel like 2 months is enough time to know if it's time to roll the tubes. I know that's a little on the impatient side, but what can I say.... I'm obsessed . 

@larryi 5751 and 12AX7 specs differently in a few significant ways. gain is one of them. heater current, plate resistance are 2 others. 

@crawfishdaddi 5751 is not a drop-in substitute for 12AX7, especially not in phono circuit. any such substitutions are circuit-dependent. ask quicksilver if such a substitution is ok in their circuit.

@larryi  thanks for the explanation.

To the OP, I agree with DeKay's first post.  Let the preamp settle in before making changes.  How many albums have you actually listened to for your sonic conclusions?

GE 5751 TM BP are very nice tubes. Looks for the "silver clips" variant that was produced only from 1952 - 1954. It has bracing clips over the plate "ears" that poke out past the micas. Way over-the-top construction. Then the penny pinchers took hold of production, and "quality" features like this dropped off. The "silver clips" tubes sound sweeter (better) than other GE TM BP.

Every 12AX7 / 5751 has its own sound, and nobody can really predict you what you might end up preferring. For me - 5751 generally projected a tighter, more precise image with smooth clean sound. 12AX7 project a larger, slightly less precise image with a ballsy, dynamic sound.

Mazda silver plate 12AX7 are kind of amazing, combining the strength of both types. They have 5751 style "T" plates, which is unusual for a 12AX7 (and also the silver / nickel color). They carry a little extra energy / zing up top, so if your system leans bright they might not work, unless you can balance them out (e.g. with Mullards). But wow, what a tube! DON’T make a mistake of getting Mazda / Cifte silver plate 5751 - those are ridiculously bright, just about unlistenable.

Teles are a nice, good all around 12AX7. Ribbed plates a little more dynamic and details, smooth a little warmer and well...smooth. I prefer ribbed. Don’t way overpay a tube dealer for these. There are tons of them still out there. Buy them all day used (tests strong) and throw out the duds.

Mullards are warm. So warm. Usually too warm.

5751 are close enough to 12AX7, it’s always a safe swap. Most tube circuits are pretty robust and flexible. I’ve accidentally swapped a 12AU7 (5814) into a 12AX7 slot and it sounded better that I would’ve imagined. The measured differences between vintage and new 12AX7 is probably on par with that between vintage 12AX7 and vintage 5751. In a phono stage you might change the EQ a bit, but that's more subtle than you might think. 

Don’t drive yourself crazy with tube rolling, because you can easy get into a habit of liking every new sonic perspective you hear and thinking "this is the one!" every time, and it never ends.

@larryi @cey , this is great stuff (insights like this are what I was hoping to find when I posted this question). Quick follow-up: if I decided to go with 5751s (several people have reported these clean up the sound in their phono stages), is there a particular position I should avoid so that the RIAA equalization curve isn't disrupted (I will ask the same question when I call Mike over at Quicksilver today and report back)? My current thinking is to put the 5751 in the gain position, and just roll the input and cathode follower tubes with NOS tubes (same tube type).

I'm thinking GE triple mica 5751 for gain, Rayethon/RCA 7025 12AX7 for input, and Telefunken/Amperex Bugle Boy 12AT7 for cathode follower... Also, once I go with a 5751 in the signal path, do I need to make all of the tubes 5751 because of the lower gain?

thanks again

Yes, it has only 70% of the gain of a 12AX7.  Aside from reducing gain, if it is used as part of the equalizer circuit, that lower gain could screw up the equalization curve and mess up the sound that way.

If I'm wrong please correct me.  The 5751 has lower gain than a 12ax7, but the are otherwise interchangeable.  As such either one may or may not be an optimal choice for a particular circuit design, but they will work.

most tube enthusiasts dont know enough to know that that is incorrect, @crawfishdaddi. 

to be clear, 5751 is not a drop-in substitute for 12AX7 . that particular substitution is circuit-dependent. its rarely the case in a phono circuit.

glad to clear that up.

ceylon

Good thought @cey , I ran a quick search of Audiogon and found this:

https://forum.audiogon.com/posts/2446823
 

sounds like 5751s are interchangeable, but I’ll follow up a with a call tomorrow. 

@skiznfliz & @crawfishdaddi 5751 are not a drop-in substitute for 12AX7--thats circuit-dependent, and a phono circuit theyre almost never a substifute for 12AX7. quicksilver will tell you if 5751 can sub for 12AX7 in their phono stage. 

When I needed to replace the tubes in my Phono Preamp, I called the manufacturer, Zesto.  Fortunately, they are a small to mid-sized manufacture and the owner/designer/salesman, George, is a wonderful guy who loves to speak with audiophiles.  

He told me that he listened to many new and several NOS sets of tubes when voicing my Andros 1.2.  His choice for the 'Best Sounding' tube was current production (and inexpensive) JJs gold.

You may want to contact your gear's manufacturer... like George at Zesto, they probably have done their homework!

@ larryi, thanks for the information on Tele-fakes. Perhaps this is why so many folks are reporting that modern-production tubes, of various brands, sound as-good or better-than NOS tubes.

@yogiboy - yep, sure did. 

@cey - great thought... text has been sent!

@russ69 - good to know there are high quality new production tubes out there as an option; the NOS tubes are getting rarer and WAYY too expensive!

@skiznfliz - you're the second person to suggest subbing in 5751s for the 12AX7s and I'm intrigued. I will definitely experiment with this!! Also, I started with the MP-200 and it is an AMAZING cart. It is definitely the sweet spot on the graph of performance vs cost. Upgrading to the MP-500 (before I started running the QS phono stage) was the best sound I've ever gotten out of my system. I was MC cart curious, but now I'm most likely MP-500 for life!!

Finally, if you want to save SERIOUS $$$, order your Nag direct from Japan (https://www.cdjapan.co.jp/product/NEONAG-MP-200). I bought my mp-500 this way and had zero issues. 

Quick follow-up: were those Gold Lyons you put into your Rogue NOS or new run?

Brand new production but they are doing really good things at Gold Lyon. I buy my tubes from Upscale or the original equipment manufacturer. My Gold Lyons came from Upscale. Not really cheap nowadays but I been very satisfied by the 4 different Gold Lyon tubes I have bought.

In my Phono Pre I run GE 5751 Black Plates - Triple Mica’s instead of 12AX7’s and LOVE THEM… The 5751’s make for a great phono pre tube, might want to consider over a 12AX7.

I also run a set of RCA 5751 Triple Mica Black Plates in my DAC and they do a great job of giving it a more of an analog sound than other tubes I’ve tried.(Mullard Reissues, Sovtek LPS’s, JJ’s, Pisvane’s)

Something to consider…Could also be a mismatch of synergy with your system based upon your cartridge not liking your phono pre or vise versa… Although the Nagaoka MP-500 is an awesome cart !!!  The 200 is my next cart ! 

ask dave thomson at raven audio he also has a lot of NOS tubes for sale. 

your phono amp may not be a good match for the integrated you have. 

pass on mullard,  brinar, amperex/philips and tungsram seem the wrong direction

for your qicksilver.

the raytehon iblack plate s worth a try. 

if you want to spend a lot money, get mazda nickel plate; if you want to spend not as much, get telefunken smooth plate. RCA blackplate have good upper frequency extension as well 

go ahead and start with the top dealer in the US, brnt jessee. hes not the cheapest but not the most expensive, neither. or check with dave thomson at raven audio hes welll-educated on the matter.  

New Teles are JJ (Slovakian).   Even supposedly vintage Teles could be Chinese fakes.  These days, the fakes look pretty authentic—they have the diamond molded into the glass like the real thing.  Anything good has fake copies.  I’ve seen fake Audio Note speaker wire that you can only tell is fake by peeling back the heat shrink cover at the spade or banana plug.  I saw a Western Electric preamp that cost $20k that was totally fake—rusty transformers and all.

Are the diamond bottom NOS several hundred dollars better than the standard telefunken 12ax7s?  

There are new production Telefunkens (Black Diamond) that share only the name with vintage German made Telefunkens.  I have no idea how the new ones sound, but probably very different from the old ones.

The Telefunkens I run in my phono stage are the crazy expensive ECC 803S (equivalent of 12AX7).  I have heard others, but I don’t recall specifics.  

Thanks for the reply @larryi , yes - the loading on both the Technics onboard phono stage and the QS is 47k ohms (which is what the cart calls for). Unfortunately, neither have the ability to change loading settings. 
 

Regarding the telefunkens 12ax7, I’ve noticed there are several different types ranging in price dramatically. Do you have any experience/recommendations on specific type? Are the diamond bottom NOS several hundred dollars better than the standard telefunken 12ax7s?  

Not certain why, but phono input cables, tone arm wires and phono preamps take a lot of use to stabilize (sound as they will long term).

New small signal tubes in well used gear can take 10-50+ hours (maybe where QS’s 30 hours comes from).

There are gizmos (for low signal strength special EQ pathways) available that help simplify the process, but I’ve never tried them (Hagerman comes to mind).

I just wait and listen to music as far as TT’s go.

Here’s a link to the $50 Hagerman gizmo that you run a line source (CD/Tuner/???) through - instead of playing LP’s.

https://hagerman-audio-labs.myshopify.com/collections/accessories/products/iriaa2-inverse-riaa-filter

DeKay

Is the cartridge loading the same for both the new and old phono stage/section?  That warm and "wet blanket" sound can be the product of incorrect loading.  If you have options, try a different setting for loading.  The right value for loading is somewhat dependent on the phono stage, so the optimal value may differ for the two stages so try all options available to you.

Yes, tube choice can make a difference.  You mentioned the options you are considering, but, you did not mention what tube brands/types you started with that you don't like.  This information will help others in offering suggestions on which way to go.

If you are looking for a clear, somewhat lean sound with a lot of "jump." I would suggest Telefunken, but some of those choices can be quite pricey.  

Thanks @russ69 , I will look into the Gold Lyons. Quick follow-up: were those Gold Lyons you put into your Rogue NOS or new run? Also, if you've found a good place to buy some, can you please pass it along?

@dekay, waiting to see how it sounds after the break-in period has definitely occurred to me. I'm struggling with 200+ hours those - that's ~8 months worth of record listening for me!! Can you share any personal experience/rational for waiting that long?

I just ordered Gold Lyon preamp tubes for my Quicksilver Mid-Mono. Looking for a little more extension. Previously I replaced the stock tubes in my Rogue Sphinx V3 with Gold Lyons and it really made a nice improvement. Those aren't cheap tubes anymore but the difference was substantial.

Suggest running the (new?) QS for 200+ hours with the stock tubes without changing/moving anything.

DeKay