I just acquired a matched quad of 1959 Tungsram EL84's for my Oto Se Signature and althought they are electronically matched, the plate structures sligthly differs. Which makes we wonder whether the Oto actualy requires a matched quad of EL84's given its single ended topology (or do two matched pairs suffice) and secondly when using two matched pairs for the Oto how to plug them correctly in positions 1-4 within the amp. Does anyone know, or do I better reach out to AN or PQ directly?
In PP it is super important that the tubes be precisely matched with regard to DC plate current and AC input grid voltage (gm). In a single ended design like the OTO precise matching is not nearly as important. The only real advantage to having two matched pairs in a single ended design that uses a single ganged volume control would only be volume matching between the channels. If you have a true dual mono setup with 2 volume controls then I don't think matching would even matter at all. Since your tubes are already matched then you are set. I don't think that the plate structures being slightly different will make any difference at all as long as the tubes have been electronically matched. As far as plugging them in, I believe matched pair 1 go into V1 and V2 and matched pair 2 go into V3 and V4.
Thank you for the clarification. I don't have an OTO. Was going from memory which obviously is failing.
I have a soro phono SE signature with the E lx he hemp speakers and I would like to extract maybe a little more detail from them. Would getting or trying some other tubes help? And if so, could someone guide me on what brand tubes please?
I have tried a few 12au7 / 12ax7 tubes on my OTO SE Sig (Tung-Sol, JJ 802 / 3s, Gold Lion, JAN Philips). I returned to the Psvane 12au7 and 12ax7 with which the OTO was delivered. For me, the balance is very good as well. For the power tubes, I replaced the Sovtek EL84 with 6p14p-ev which I find excellent.
Fred - user named oregonalex posted about this on December 28 2019. I have just read it as I am doing the same experiment. He tried Telefunken and Mullard for ECC3 and chose Mullard (NOS) and was choosing between Matsushita and the stock Psvane for ECC88. Ended up with Matsushita eventually but there were other variables; drivers Telefunken and ECC82 Brimar/Mazda. By the way, Alex - this was a great post! Very useful to me in my experimentation.
Thanks, chris and Litvin, much appreciated. I did read oregonalex. I guess I'm curious about a wider range of experiences. Also, is $200 for a Mullard tube reasonable in 2021?
I fear they might be. There are not a lot left. Some online stores run them for $500, depending on vintage. The question is whether we really need them! I will play with it some more but I feel that the stock selections by AN are very thoughtful.
In my case so far I only tried the phono stage of the OTO. The original ECC88 was JAN Philips 6DJ8 NOS (stock) but for ECC83 it had in fact another JAN Phillips but 12AY7. The original owner swore that this was how it came. Martin Grennall from AN however replied to my query that they use a variety of NOS in the ECC88 slot, but only use Psvane ECC83 in that position. Interestingly enough, in my M2 stand alone RIAA they used an NOS Soviet tube 6N23P for ECC88 and a new Sovtek for ECC83. Not having anything other than that, I put a Telefunken 12AX7 and kept the original JAN Philips for ECC88. This noticeably increased the gain and shortened the distance I mentioned earlier - between the OTO phono stage and the stand alone M2. Sovtek 12AX7 was also good but audibly harsher, not as smooth as Telefunken. I then swapped the old Soviet 2N23P while keeping the Telefunken in the ECC83 slot, and this screwed things up everywhere - both the Oto and the M2 started to sound worth. I absolutely did not expect such a marked change - the Oto totally rejected the 2N23P becoming flat, while in the circuit in the M2 it sounded well, and vice versa, M2 became too lose with JAN Phillips. Put the original ECC88s back to their respective units, and everything went back to good. With the 12AX7 in the Oto phono I did not have Oregonalex's experience with Telefunken. It sounded very well to my ears. I have a few more coming by mail, will post later. That said, to my ears the stock M2 RIAA does have an advantage over the Oto phono stage even with Telefunken - more "real sound" so speak, fuller, better timbres, more space. FWIW
Thanks, Litvin. I am not an expert but try to state only what I believe to be true: Upgrading the tubes in my Oto has no doubt been an improvement. I would never put the stock tubes back in. They are very decent but it's not difficult to get better tubes that demonstrate more of the amp's potential. I have a NOS Telefunken in my Phono 1 now and it's great, but I'm looking for the best possible tubes for my phono stage now, not just an improvement from the stock tubes. The NOS Mullard Ecc82 preamp tube is arriving in a few days and I'll report back when it's been running for a few days.
P.S. I am sure I don't *need* a $200 ecc88 tube, but I'd love to try one, and it's not a fortune considering the cost of the system as a whole.
Thanks for the help guys. I have put the same plate structure in V1&V3 and V2&V4 positions, just to be sure. Btw the Tungsram EL84's sound very nice in the Oto, no incentive anymore to find other tubes.
Update: I couldn't find any Siemens CCa Ecc88 for the Oto's phono stage, so I jumped on a NOS Mullard E188CC. Will report back on my experience later
No, they are becoming unobtanium-rare. I had a DAC2 clone of sorts that used two ECC88 tubes. At first I had Telefunken E88CC in there, and even though the E88CC is the premium grade version, a pair of CCa still gave a significant improvement. I have since learned that there are several types of CCa, and I don't know exactly which type I had in there. The gray-shield version is the best IIRC.
hello, currently run Cobra with AX Two speakers. want to upgrade so do you think an Oto Phono SE together with Dac 0.1x will be a nice upgrade or should I go another way? thanks
I guess the Cobra will be pretty new so it would be a pity not to give it a chance with some other speakers like the Ks or even Js, depending on your listening room. The Cobra will give you all the power you are likely ever to need, but the OTO Phono SE is also pretty special. But I'd keep the Cobra and upgrade the speakers and see were that takes you.
Peter very kindly sent me a list of tube rolling recommendations for my Audio Note M3 preamp and M2 RIAA phono. A couple of these are pretty difficult to source (Telefunken, etc) unless I go through ebay, but I’ve read rumors that some of the rarer tubes are being faked. Does anyone have any experience with the legitimacy of some of these sellers, or what to look for? I don't mind spending a bit but I don’t want to get taken for a ride. Thanks!
You're looking for legitimate dealers? - Brent Jessee 12AU7 Tubes in Stock - Upscale Audio - Vintage Tube Services (call Andy). - Jim Mcshane Tube & Information Page - Tube World Express
It’s true, a friend of me bought an Amperex Bugle boy and this one happend to be re-painted. There is a lot of fake, like test results often show beter results or don’t belong to the tubes the sell you.
AN-E SPe HE owner. Considering upgrading to AN-E SPe HE Signature. What should I expect to hear? Is it worth the extra ~$12k?