You might try the Mazda/Cifte 12au7's. I swapped out Mullards for the Ciftes in my tube integrated (master sound). I found the Mullards muddy in comparison.
25 responses Add your response
You might want to try the Amperex Holland 12AU7s. Be careful though as they were sometimes "only" rebranded Mullards, you can tell by the etched code. My all time favorite in any position is the direct sub 7316 an Amperex product but now very expensive,
It really sounds like a German tube such as a Telefunken would do the trick. Also you can call Upscale for help since they import Prima Luna they will know what works to bring out the qualities you want.
I have swapped a number of NOS 12au7 in my Primaluna Dialogue One with great success. To my ears the Amperex Bugle Boys are the best. I have failed in my quest for a "reasonably" priced 7316 Amperex mentioned by Mechans above. I also like the RCA Clear Tops Side Getter, the Psvane Shuguang Black Treasure. Frankly, the Mullards were not as clear as the tubes above.
You should also try swapping out the 12ax7 for some Sylvania 5751 Triple Mica black plate and or/grey plate.
Another suggestion, try the NOS Russian Reflector 6n3ce output tube (6L6). This combo of tubes bring this integrated to a whole new level, much, much better.
If 5751s are suitable for this amp then you must try them in place of the 12AX7s. I am an inveterate tube roller and find switching the tube to be the fastest easiest mod you can do yourself. Most amps will tolerate changes to the smal signal tubes, if the pinout is the same.
There are a bunch of good 5751s to try but most everyone wants the "holy Grail"- the late 50s NOS triple mica black plate by Sylvania. I use them and they are truly great, but less rare 5751s work out pretty dammned well, try the RCA white print or Command series, GE are abundantand cheap. a decent place to start, try to get their 5 Star Black Plates, The rarest of the rare are Raytheon windmill getters. They are worth the trouble but very expensive and truly rare, unlike every tube you see on ebetrade. If you just want to dip a toe in the 5751 water the JAN tubes can still be had NOS but watch out as some pretend it is the late 50s early 60s tube. Check the Audio Asylum Trader section lots of reasonably priced tubes for sale, if you can't find what you want here.
All 12AU7s is the manufacturers tube designation for the amp we are discussing. In that event the OP may want to try another direct sub the 5814. The 50s Hytron and later CBS Hytrons are held in high esteem but it is necesarry to them alone to get a feel for the tuybe type. It has what I call the "strong, clean signal" that I find desirable in certain situations.
The RCA 5814 versions are very good and as are many others, try em they shouldn't cost a lot. The other clean strong signal 12AU7 I have some experience with is the Brimar 13D5 which has been around for a few years, but not sure who is selling them now.
As I said earlier if you can find some good Telefunken ECC82s even used testing good you may want to try them. Lets face it most of what is called NOS is just OS and not new.
I don't have a great deal of faith in the RCA 12AU7 clear tops , from personal experience which I admit was a gift of some decent and some unusuable tubes I got in a batch. I don't know much about the others, try Brent Jessies Audiotubes web site, he has some details on the US types. I settled on 7316s a while ago as my 12AU7 of choice and have been hunting them until recently now that prices are really too high for most people. On E Betrade people list them with singles foe $100 and up to start for single tubes. I can't recommend anyone try them at that price.
Current production has gotten much better from all over. My old Pal Joe imports some of the Chinese tubes which he has great faith in. Others have admired the new Gold Lion smasll signal tubes with many other New Sensor tubes.
The 5814s when I last looked were still reasonable, I think the Brimar 13D(X) tubes have gotten a bit more expensive and Teles while Desirable are plentiful as pulls and hit and miss on price. IMHO YMMV etc. etc.
I've continued tinkering and over the last few months of tube rolling repeated, varied A/B comparison has led me to 1 inescapable conclusion.
In the PL Premium Integrated while the GL KT-88's are wonderful tubes with tighter control than the stock PL EL-34's at the frequency extremes, they fail on voices in the crucial mid range, with a dry papery affect. This is not a judgement on the GL KT-88's as I suspect in a different amp the issue would not exist, only a conclusion that in the PL Premium Integrated they aren't the best choice.
Additionally after rolling various 12AU7's in the front sockets (Mullards, Siemens, GL, Groovetube, EH) and then trying other 12Axx varieties its become crystal clear that 12AU7's are not the best sonic choice for the front sockets. No matter what 12AU7 I rolled for the front sockets, the pre sounded compressed and sleepy compared to the CJ PV10A pre feeding the HT input. Rolling in 12AT7's gave immediate improvement in dynamics and "liveliness". Using 12AX7 was similiar but more prone to distort
Where I now get best sound is
Front pre sockets - Amperex 12AT7 (orange world logo)
rear pre sockets - Siemens ECC83 (12AU7)
power tubes - stock PL EL-34
The PL power tubes are not my final destination as they don't have the control of the KT-88's and combined with the NOS Mullard 12AU7's showed distortion artifacts which the Siemens did not.
What this configuration does well is create a lush detailed mid range, good mid bass, and a high frequency end where percussion has both hardness (blocks) and sheen (cymbals). Sound decay is good, not chopped off as it was with 12AU7's.
What this lacks is deep bass control and good "black space" around instruments. All of which I think will be improved with better EL-34's
On the fence at this point for future upgrade between between the SED Winged C EL-34's and NOS Siemens EL-34's.
NOS power tubes are frought with difficulties. They havent been produced, in the case of EL-34s, since the late 70s at best. Finding good ones is tough but I was able to buy some Philips XF3s I believe as a quad that did look new in box. The price exceeded $100/tube so be ready for sticker shock. I am aware that some of the big tube sellers have NOS outputs but rices are commensurate with thheir rarity.
Can you sub in the New Sensor Gold Lion KT77? That would be interesting. I am kind of surprised the KT-88 wasn't good in that amp. Another "super tube to consider is the "Tung Sol" KT-120 if the trannys can handle it, ask uncle Kevy?
Finally I would make a point of trying 2 current products that have worked out well for me. The Electroharmonix 6CA7 "big bottle" and the JJ blue glass E34l (note E34l not EL34 not a typo) very underated, don't try the JJ KT-77. JJs can be bought from a webstore US based called Eurotubes.com.
I will be interested in hearing the result. I noted that no 5751 made your preamp tube list, did you try them?
I may dabble with them at some point but the combination of the Amperex AT7's with the EL34's was like when you turn a knob and it clicks into place.... so many things were suddenly right I didn't feel a need to do more than fine tune the back 12AU7 choice for cleanest sound. I am hoping that when I upgrade the EL34's that the Mullards work well again as they were superb with the KT-88's.
Please try KT120s as I'm still waiting for a tranny failure incident report from anywhere. Also, I haven't raved enough about the Chinese made "preferred" 7025s from the tubestore. They are very "clean" sounding and put a more extended and airy (and maybe accurate) top end into my Jolida at what I think is a relative bargain cost. That part could explain why they don't get as much cred as the more expensive anything else. Don't be afraid to spend less! You can lie about the cost later.
Wolf thanks for the tip about a good 7025. I tried a NOS/OS 7025 many years ago. I think it was RCA, that one trial and a confirmatory message from a friend who tried another NOS/OS 7025, turned me against them.
If it's a Chinese tube it shouldn't cost too much. Your description of a clean sound is what I find in current production 12AX7s from Shuagang, very good tubes, but it is only good if it synergizes with the rest of your system.
I can't stop buying tubes even though I will certainly not live long enough to use them all. So I decided to call myself a tube "collector", this gives me license to keep a hoard of those things. I can't even imagine what I must have spent. I try to ignore that and keep telling myself I will sell them someday. But buyers can be a royal PITA some of the time. I don't tolerate the aggrivation well. So I trade some and sell others very cheaply at a loss I imagine, if I ever remember what I actually paid.
I am, currently living in exile away from most of my gear but bought a Fisher 400 receiver which is all tube. It needed a 12AX7 so did I put one of my precious 5751s in or a telefunken ? No absolutely not I bought a current production JJ 803! It is ridiculous I must admit but I like tubes so....
Prima Luna USA posted recently that they now support KT-120 in all their line. I got mine yesterday, the first 2 hours of break in were rocky with distortion and threw 1 bad tube fault but after that they opened up and roared. They (a) remedy the PL's lack of lower bass and bass slam (b)have more percieved dynamic range and openness. I have no desire at this point to put the KT-88's back in.
so after 10 days of loving the KT-120's my pre and driver complement of tubes has been turned totally upside down. The Amperex 12AT7's are out because of audible gain distortion, all NOS Mullard CV4004's now. I've rolled the KT-88's back in a couple of times but they sound so emasculated in the bass by comparison that I'm back to the KT-120's in short order
so just an update on current tube rolling. The KT-120's continue to sing...just plain better than the cryo GL-KT-88's all around in the amp. And tube distortion in the pre section is more mercilessly exposed. I've acquired some ribbed plate Telefunken 12AU7's for the back pre sockets, cleaner, better bass, more detail that the Siemens I was using. Flipped my entire inventory of 12AU7's through front sockets again with the Teles in back... 12AU7's just sound wrong in the front sockets, low level details fuzzy, more distortion. Had settled on some Mullard 6201's (12AT7) in front, after putting Telefunken in the back sockets they were still detailed but too bright and I isolated them as a source of low level tube distortion. The Amperex world globe 12AT7's are now back in as more musical but their bass waffles, highs are a little rolled. Likely to pop for Tele or better Amperex tubes in the next 30 days.
At this point with the Teles in I have achieved my goal of retiring the CJ PV10A pre and using the PL pre section
Alright, if you have this amp, listen up. Running NOS (1960's)Siemens 12at7 tubes with triple mica in the front sockets and Telefunken 12Au7's in the back sockets is a match made in heaven. Gobs of low level detail, no tube distortion, no edginess and superb low bass tone colors. The CJ PV-10A is completely retired now, sounds veiled compared to the PL integrated with this tube configuration and Rel cap upgrades. Nice to be finally satisfied and ready to focus on other system areas.
Back to this thread after a while. In the past year I have made the following changes
1) the front 0.22UF caps are now clarity CAP MR's
2) the follower 0.1UF caps are Rel CU caps with 0.01 TFT vCAP bypass caps
3) the power tube 0.22UF caps remain Rel theta's because of space limitations but bypassed with Rel Teflon 0.022UF caps
As these changes were made it became clear that the 12AT7's did add distortion, I now run Telefunken 12AU7's for all pre-sockets.
This is detailed, airy but it does not match the CJ for lower midrange weight, had similar criticism when I had Rel 0.22 teflons in the front sockets before the MR's. I have ordered some VCap CU's to replace the Clarity MR's as these are reported to shift balance to improve lower mid range, will report back in a few weeks after they are installed and have some hours on them.
The VCap CU's have been installed now about 5 days and I have about 20 hours on them. This is a very different experience than other capacitors, gobs of impressive but natural background detail. Oddly they seem to require more power for same volume levels but I have seen this before where old gear was masking signal, emphasizing loudest instrument and new gear in showing more detail, and correct harmonic overtones is consuming power across more spectrum. Very pleased, the CJ PV10A pre can no longer compete, sounds colored in comparison. WIll have to be patient as all I read about others use of VCap states 100 hrs as minimum break in time.