NOS Tube Recommendation for Quicksilver Phono Pre Amp

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?

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?  

@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. 

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. 

@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

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. 

@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 . 

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)!

@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):

@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!!