Another question,


Are the Raytheon OD3A tubes as good as the RCA OD3A versions, or about the same?

Edit: Sorry I wrote this as James commented and posted after without reading his, but will leave it as is since it offers more views on sound changes.

VRs are big sonic influencers, more from voltage drop than specific tubes within a type, though like all others that matters too.

OA3s allow the most power to the output tubes of the Torii III and IVs (I don't have a V). This makes all parts of the spectrum more powerful. But bass in the balance is likely the most noticeable, compared to a little milder OB3s, OA3s giving a fuller bigger sound altogether, increased bass fullness also likely contributing to fuller/warmer mids. Stronger upper mids and highs from OA3s usually show more with increased intensity and density rather than necessarily being "brighter," but depending on all else, it can feel bright because more voltage to the power tubes can make the upper mids and highs more consolidated. One tricky part in my Toriis is that "more" bass can result in some smearing/muddling, making the bass fuller/thicker, where, again depending on all else, OB3s can make the bass seem stronger if the OA3s are overly thick... then OB3s tend more articulate and fast and potentially more impactful bass even though the bass in the balance is less powerful... a consideration in evaluation anyway.

In my system/room, where everything is tuned to be warm, but quite fast, spacious and resolving, signal power is too intense with OA3s for me, using OB3s mostly for years. But again, depends on all else.

OC3s let less voltage through than OB3s, and OD3s allow the least. So OD3s will lean the power tube signal the most across the spectrum. There will be notably less bass fullness in the balance, contributing to more open mids and highs that are already less full and more spacious from less signal intensity... so a more open/clear/spacious sound with generally more fine information complexity from less signal consolidation.

From what you say about bass being critical, I suspect you might find changing from OA3s to OD3s too lean, open and clear. My guess anyway.

Will describes my experience with these voltage regulation tubes well, I used them in both the SEUFO3 Monoblocks, Torii Mk II and Torii Mk III and the 0_2 types in my SEWE300B.

In my SEWE300B i am running an unusually structured 0B2 from Holland for the input tube and two British 75C1 for the output tube--an interesting small tube variant of the 0C2 that I really love. This particular combo of voltage regulation tubes hits just right for my system.

Interesting Dom. A ways back, I recall using Hytron OC3s for periods here, and the way they opened my system/room sound and tightened bass was really nice. In this setting, OD3s were alway a little too flat/lean, and though OA3 being a little heavy handed here, and OC3s a little clean here, they both can work beautifully with the right company. I always seem to end up with OB3s though.

For small VRs, I agree with Lon on 75C1, a textured/warm euro version of OC2s that is not veiled or dark here.

RP... Of the O_3s I have tried, comparing ST/coke bottle, short "A" straight bottles, and tall straight bottles of a type, as is pretty usual, shapes, maker, and vintage all seem to influence sonic differences. Guessing because they are more powerful, OA3s may show differences more powerfully.

It has been a really long time, but as I recall, the influences of 50s RCA OA3 STs were the darkest/warmest I tried here, dark if with all else they thickened/smeared lower information, and "warm" when they supported a darker tone without thickness or masking detail complexity and speed too much. Whereas JAN Sylvania STs, early 80s, I recall as more open and cleaner, having similarly strong bass weighting but clearer, less textured… I think both worked here with the right company. Some Amperex short bottles OA3-As are a little warm, but to me better balanced, less bass weighted while also resolving of textures and fine information nicely. Comparatively, here anyway, the RCAs and Sylvanias have a little too much bass weighting, making the cleaner/faster top sort of disparate from the fuller/slower bottom. NOS Russian taller bottle OA3As vary too, but seem to tend more similar to the Amperex, pretty neutral but more open space and articulate and a little less smooth/textured, though still resolving of good textures. Anyway, some rough impressions, and if you are happy with OA3s overall, shape and vintage can give interesting variations if you ever want to play around more with OA3s.

Most OB3s I have are STs, and they vary also, generally not a whole lot, but enough when you get serious about tuning with tubes for those variations to be real choices. For them, though each production time seems to have sonic variations, I think a primary sound difference has to do with how they were made internally, a visual reference for that, between the earlier ones and the later ones, one has offset center wires rising out to bottom internal glass blob, and the others, the middle wire centered… Close, but one tends a little more complex and the other a little more open clear... but still those with the same construction I have all sound a little different. The only OB3s I have that are short bottle A's are Raytheons and I thought first they might be mislabelled since the internal gas color is orange like OA3s, and OB3 STs the gas lights  blue. But sound-wise, they did seem closer to OB3s to me as I recall... I did not go deep in listening to them though as I preferred ST shapes, being a little more complex and warm sounding to me.

One area of thought comes to mind relative to tubes and how they influence the whole while building/modifying, and/or tuning with system or room parts and components. Something I am always trying to keep going here is having a relatively neutral set of balances as a baseline to do other system work from… trying to avoid compensations in balancing the system/room sound while inadvertently off-balancing the thing I am working on, spectrally, in speed, and/or resolution.

So here, with my new DAC my main focus, and stock, once fully burned in especially (which took a long time), it tended hyper expressive… “too good” for my resolving and easy flow system... and having done loads of experiments to "find its sound," I feel like it is time to check myself. I think the DAC is getting really good, still beautifully resolving and complex, but less pushed, more relaxed. But before going further, may be time to pull out my other DACs….  to find out if, or how much of my challenges around tuning this DAC are it, or the rest of the system/room.

Since I have been doing modification so long, I have been super careful, as careful as I can, to hold a warmish, but neutral baseline sound with all the many balances pretty balanced...like natural sounding immediacy and speeds bottom to top, or harmonic complexity and decays having natural and complete balances bottom to top. To support this, I change out speakers now and then, cables, take pre-stages in and out… just trying to maintain baseline balances in hopes of all changes I make being relatively well balanced.

My baseline DACs are more similar than not in these balances. And one of those, the Tranquility, was designed by a friend and his development team using extensive blind testing for parts, tested through multiple reference system/rooms, and using lots of quality DACs of the time and really good analog for cross referencing. And this guy being a super discerning listener, I trust that it is well balanced. The Tranquility, though modified some by then, was my reference when I modified my Gustard. Each has their own character, but they have very similar balances overall. I tested the Gustard a month or so ago, and all seemed pretty well then with the new DAC tuning, but that was a lot of experiments ago, so time for a more conclusive test.

In that vein, back to VRs and tubes, not sure what inputs or rectifiers you are using, but the RCA OA3s tending a little toward strongish bass and warmth, and as I recall Raytheon OC2s… pretty clear and neutral, but with a little more warmish textural feeling than RCAs of the same type...and here, Mullard reproduction EL34s can sound pretty good with the right company. But that takes some effort comparatively for me, as independently, to me they tend a little darkish, slowish and a little veiled for the type, while being a little concentrated mids up, so I don’t use them. But what I am thinking… if most tubes independently lean toward bass and maybe a little veiled, and if the MKIII is tuned to fuller, bassier settings, this “bias” could influence how other system things and the room are tuned, possibly making them a little extra resolving and neutral/clean as compensation???

Anyway, I just have found that if I can avoid compensation, whether changing a resistor or cap or component, or room treatment..... it is easier to find more refined tuning as I go, my experience of course, and VRs play into it for sure.

Good point James, in part why I usually don't recommend tubes and talk mainly about their sound tendencies ...and I guess finally all tubes are influenced by all else really. That Steve has dug into VRs as filters and sound adjusters is a cool thing I really like... a great tuning tool. In the Toriis I am familiar with, the III and IV, the small O_2 VRs most directly influence inputs, and the O_3s, the power tubes... then of course, the inputs influence the outputs@#$%^&*(. But still, I find each input and each VR has its tendencies, and each power tube and the VR before them have their characters and tendencies. Still, I agree, sonically they end up more or less as one... and one or the other can make the other "better" or "worse!"

For what it is worth he’s my experience with VR  tubes in my Torii Jr v2.
The tubes I tried are the Decware stock Russian version, ‘80’s Sylvania OA3, ‘60’s Westinghouse OA3, OB3, OC3 and ‘50’s RCA mil spec OD3.  As you can see I had a preference for Westinghouse and wanted to compare same Brand and ~Date.  In my TJ, with NOS Mullard EL34’s xf2, my favorite were the Westinghouse OA3 for more lively music that needed more juice and the RCA OD3 for more mellow relaxed music.  They all sounded very good and I really did’t pick up but minor changes.  I found the higher up the letters you go they loose some output volume but pick up a sense of clarity and smoothness.  Steve had mentioned in the Manual they could be more like using a battery.  My new amp can only use OA3 so I am selling off the others.  These tubes are inexpensive so the best way is to buy each version and listen on your amp/tubes.  Have fun with it.

Thanks to everyone chiming in here with your well informed responses.


So, I came up with a few items on E-bay yesterday and placed some orders.

I decided to play it safe and stick with NOS unused and tested tubes to replace my dwindling stock.

I still have not found the remaining supply I had stashed away with extra RCA OA3's (NOS), and extra Raytheon OC2's to cover both sets of voltage regulators required for this amp.  Perhaps someday they will show up when I am not looking for them.

I am going to start hoarding new tubes for future use before they end up being super rare and extremely expensive. I really don't want to use the modern trash tubes that are manufactured today, that is if you can find the tube you need being currently manufactured. (there are a few exceptions)  IF ONLY I COULD FIND A QUALITY MATCHED QUAD OF RUSSIAN MILITARY OLD STOCK EL34 EQUIVALENT TUBES DIRECT FROM THE UKRAINE AT A FAIR PRICE!  That is one thing that I doubt I will find.

The Russian military equivalent of the EL34 tube is the 6P27S (Cyrillic: 6П27C).

The 6P27S is a Soviet-era beam tetrode designed as an analog to the EL34.

Some data I read about the soviet tube version:

Note: While the 6P27S is considered an analog or equivalent, it may not be a direct drop-in replacement in all situations. Some amplifiers might require modifications or adjustments when using the 6P27S instead of the EL34.

So, I know that I MUST have at least a matched pair for each channel (the ToriiMKIII is actually twin mono blocks in one case) I have always ordered matched QUADS for this amp.

Will, I am thinking that if anyone would have experience with these Russian 6P27S tubes, or has a strong understanding of them, you are most likely one to know about them, among a few other's around here.

I am interested in possibly pursuing a quad set of them if they pan out to be a good choice for my amp, AND if I can actually score two matched pairs of them.

The current set of Mullard reissue quad matched cryo'd EL34 tubes that I have in the amplifier now have a great deal of life on them remaining. This set has been in my amp now for five years with roughly 7000 hours on them! They still look exactly like they did new. The getter flashing is still completely intact with zero signs of wear or darkening where the flashing would typically show reduced with age and usage.  These are by far, the best tubes I have ever used by a long shot. These were manufactured in Russia under license by New Sensor from what I understand to be true. These are premium quality and absolutely worth the price, and actually more if you ask me. I seriously doubt that a better set of tubes can be found that are still being produced today, compared to these.

I find not only are they rugged as a Russian tank, but that they are proving to last a very LONG time without fail ( I drive my amp fairly hard all of the time ). These replaced a set of cryogenically treated Electro-Harmonix quad matched tubes from Cryoset which I purchased long before Ron passed away.   I liked those tubes, but they where nowhere near as good as the new Mullard replacements, in ANY aspect.  That set of EH tubes had a very short lifespan.  At best, they were worn out with no more than 4 or 5 thousand hours on them.  When I replaced them with the new Mullard reissues, the sound difference was immensely improved!  

When I received this amp new back in May of 2012, it came with those sorry low grade Chinese(RUBY) rectifier tubes which sucked so bad, I had to replace them immediately! Those were a bad joke to put it lightly.  I was not happy when I got my amp with those.  I felt cheated when I got the amp with these pathetic cheap tubes which I will NOT use. I remember powering the amp just to watch the arcing inside of these tubes as they rattled away with odd noises. They had to GO!


The amp shipped with JJ el34's to burn in the new amp with until I could afford buying a better set of tubes in the future.

These were not quite the high end Svetlana Winged-C tubes which is stated in the manual. Again, another bitter disappointment where I felt cheated with low quality tubes instead of the Svetlana set which I understood to be part of the amp package. I would have passed on buying this amp if I knew that I had to fork over a huge sum of money on quality tubes just to make it sound good. For what these amps cost, that should never be an issue.

 I decided to replace these with the Cryo'd Electro-Harmonix Quad matched set from Cryoset. These were much superior to the JJ's by a long shot, but still nowhere near as good as the current set of Mullard reissues I am using now.

I like these Mullard reissue el34's so much, that I find it difficult to consider another tube offering. Especially for the price, and knowing from experience that these will last a very long time without fail.  I feel confident that my current set will last me another 3000 hours, but time will tell. Hey, they could go bad tomorrow, just like any other tube. But you know what, I am confident that they won't go bad anytime soon.  I highly recommend these tubes without ANY hesitation. If you get them from Upscale Audio, you stand a good chance of getting quality tubes.

I just pulled the ORIGINAL Electro-Harmonix 6922ES tubes from my amp to see what the set of 6dj8 set of tubes I use in my DAC tube stage sounds like. I just received a high quality set of Russian military 6dj8 equivalents (Matched pair 6N23P / E88CC / 6DJ8 NOS Voskhod (rocket) Silver Shield tubes USSR) which are in the DAC tube stage now.

I am going to order another set of 1975 ERA 6N23P Voskhod NEW Matched pair Tested=100% ( E88CC/ ECC88/ 6922), to try out and compare notes. The 1975 era tubes are claimed to be the best ever made, especially the silver shield.

I find the new Mullard EL34 reissues from Russia to sound rich with accurate tone, full, extended bass which is tight, deep, and highly detailed. The midrange is warm and highly detailed with a very seductive presence. The high frequency range is as good as I could ever expect from any tube. Overall, a very natural and well balanced set of tubes.  That is hard to find with modern current production tubes. These are a SUPER bargain.

I have read some pretty ridiculous reviews of these tubes being used by those in other forums. The most ridiculous thing I read was from a smug guy who most likely has a mediocre amp and system, let alone zero acoustic corrections done to his room, (this of course qualifying him to accurately evaluate this tube or anything else for that matter).

In his absolute final word, he stated that these Mullard reissues sounded OK, but that they really were not that special, and that these tubes were WEAK in the bass department!   That is some very WRONG information there.

That proved to me that he knows absolutely nothing about high end sound systems, or proper acoustics which control the degree of clean bass response in a room. Most likely, he had a budget low grade tube amp which sounds like crap regardless of the tubes used.  I would guess that applies to many people who like to evaluate products and give their opinion based upon their limited setting.  Just thinking about that false review gets me angry as it really irritates me when some guys express unfair views against a product when they really are ignorant of the facts.

I absolutely proved this guy WRONG in my system.  People, do not place much into what the general consensus says about things in general. You really have to evaluate who the source of information is, and what experience they are basing their views upon.


When I hear from members that are long term here at Decware, I have a great deal of faith in what you all tell me. Why, because number one, you have experience, and two, you are truthful, and well knowledgeable of how you convey information. I trust guys like Steve, Will, etc...because they know exactly what they are talking about with the experience to back up the facts.  Plus, I know the equipment and room settings that guys here are using.  That very much helps me to form a clear picture in my mind as to what their information means in regard to my benefit.

I am not ignorant about vacuum tubes in general, but I do not have a great deal of experience trying the tube rolling experience. When I find a set of tubes that I find pleasing, I stop there and don't worry about them until it is time for a new set.  However, I am cautious when it comes time to try new things. I like to gather information from a trusted source to base my decision upon.


I will only recommend tubes which I have personally used based upon my personal experience which has been limited to a respectful degree.  That is where the best advice comes from. We all know that each and every system is going to vary in the end result, and not everyone is going to come up with the same conclusion. That being so, we just have to base our own judgement upon the information as a whole. Nothing is guaranteed, and really, the only way to be sure is through trial and error.  Right now, the Mullard reissues are by far my favorite tube choice. These are the only ones that I would recommend based upon my experience for which I feel absolutely confident in that choice.  Just remember, my system and room acoustics work together as critical parameters in which to reveal these tubes the way they do in MY setting. Your mileage may vary.

Will that change?  Certainly there is always that possibility. When I discover a EL34 which is as durable and great sounding as the set I have now, then perhaps I will give an alternate set a chance if the price is sane.  I have heard that Gold Lion EL34's are a good choice. Maybe in the future I will try a set of those.  Of course, it would be interesting to compare these sets with a set of Decware EL34's in long sessions of A/B testing just to see where the possibility may lead. I have not ruled out the Decware EL34's by any measure. In most cases, I'm sure any one of these choices are a fine one. I know that Steve goes to great lengths in selecting premium tubes which undergo a very high quality process of cryogenic treatment. That alone gives me confidence in buying tubes from him.

As of yesterday, the following sets of tubes are on order:

I bought all five OA3's in the image.








From the same dealer, I bought this set of Raytheon OB2 voltage regulators as back up supplies.


These OB2WA tubes are heavy duty premium military spec versions.






I actually purchased a bulk supply of these Russian military rectifiers back around 2005 when they were just starting to be sold on E-bay around that time direct from old Soviet stock.  I couldn't resist the ridiculous low price which was worth the gamble for trying them out. They were claimed to be direct replacements for a 5U4G rectifier, so because they looked interesting, I wanted to try them out.  They look strange, but they are built for a war zone, and that's no joke!

I had a ToriiMKII at that time which I used KT88's and 5U4 rectifiers which I only used premium old stock RCA, Westinghouse, and Sylvania rectifiers at that time. I was a bit cautious when I made the decision to place these unfamiliar Russian military tubes into my new expensive amplifier.  I took the chance because I just had to know.

I will say this, I was not disappointed with them. They worked perfectly, and I couldn't really tell any difference between these and the high quality rectifiers used before them.  I got these for like two dollars per tube back then, so I bought a case of them new, still in the original container with Russian markings.

I lost that box of tubes with most of my other gear and a HUGE tube supply ( let alone over fifty thousand dollars worth of audiophile LP pressings in pristine condition) due to really bad times in my life in 2009. That ToriiMkII was part of that loss.

I still have extreme anger issues over what happened to me over that very dark period in my life. It took a long time to recover and start enjoying life again. But that is another story.


Since I have experience with these Soviet military rectifiers, I see that they are still cheap and in supply.  I am going to order a set from a Ukraine tube supplier to see how they perform in my current TorriMKIII. I am thinking that I won't be disappointed. As long as they don't damage anything, which I doubt, then they are worth trying at such a low price. I can tell you this from personal examination, they are built for extreme usage and very attractive if not unique.


Here is that set. Note that these are authentic Svetlana 5C3S rectifiers with the OTK factory markings.








The following images are of the Mullard reissue EL34's that are Quad matched with cryogenic treatment from Upscale Audio.

As I said, they look and perform as if new to this day, accumulating nearly 7000 hours on them so far!






These are still available at nearly the same price.




Give them a try, I think you might be impressed as I am.







The A.C.M.E. supply has a lot of good things in store.

(But for how long?)

RPS. If you can cancel the repro Mullard EL34 order, and are interested, I can send you mine. I suspect they had 500-700 hours on them, wanting to be sure they were fully burned in before moving on. Guessing they are also a similar make time as yours. I got one of the first group of Torii IIIs and probably bought these tubes within the first year of two of having the amp. I can't recall where I got them, but I bought most power tubes back then from Ron at Cryotone.

Based on your praise of them in your DIY thread, I tried them again maybe a month or 6 weeks ago, and then again today. Today especially, having tuned my system to be quite clear as a means to test the DAC modifications in a sort of extreme, I think I hear what you are hearing in the Mullards. In this clear setting, they have a classic mid "warmth" to them that is appealing for sure, just not quite my thing considering all things.

I also have a quad of Tungsol EL34s that came with the Torii IV I think, and I don't think I really used them having liked a quad in the MKIII, but not totally loving them for my particular needs. At least in this system and room, they are nicely balanced spectrally and solid, but like many Russian tubes, a little too dense/solid for me, a little too much consolidation of some of the very fine information. Quite nicely made tubes also.

I also have quite a few various inputs, a few 6L6/5881 types, and more notably, some mid 50s Winged C 5U4G-ST equivalent rectifiers and Winged C EL34s, the latter I think coming with my Torii III? Very popular tubes, I need to try these Winged Cs again, the system always improving. But from memory, both to me tended a little warm/full for my needs, and a little disparate in their relationship from bottom to top, the bottom a little slow and thick in relation to relatively well detailed warm resolution of the rest. And not that they could not be tuned to sound quite good...I just tend to prefer tubes that do what I love with less need for compensation to balance them. Just a personal preference really because mixing and matching tubes that have notably different sonic signatures as a means to find balanced beauty can be really good, but with my need for very complex resolution, this can tend to be challenging ultimately. Still I will likely keep the Winged Cs around for a while, as they are interesting to me in the right company.

All that said, in the right settings, I can definitely imagine lots of Russian tubes to be really good, so can get your preferences in your room and system. Just that I am not a complete fan here in this setting, generally wishing for more complexity within the relatively articulate balances they often tend to be good at, and in many cases, I want a little more top extension with very fine detail.

Anyway, if you would like the Mullards and Tungsols, PM your address and I will send them in appreciation for your time in the services.

Hey RPS,

I am glad to find a good home for these tubes. And thank you for your offer of parts and music, but I really am glad to give you these tubes.

Relative to caps, I try to keep my supply at least 400V and most are 600 and above so that I can use them in most applications without much thought, testing, or confusion. Having a lot of parts around and no dedicated workbench, this helps my pathetic mind. And I do have a number of lower value Russian PIO and teflon caps, so thank you for offering but all good there.

Now Music... I would love to hear some of your recordings, and if you could send some on a USB stick, I can load them directly onto the external drive that feeds my tuned up Mac Mini server. I really appreciate it, excited, and will write more in a response to your PM!

Seems we are diverging from VRs, so I thought I would post on your DIY thread some pics of my MKIV where I was gradually able to fit all good sounding film caps into the power supply. As you will see, it is packed though, and I like that you will be making a new base for your MKIII, something I almost did here.

Maybe four years ago, I started moving into my MKIII for more extensive modifications, but then my wife got sick, and the intensity of being her caregiver, and her loss left me overwhelmed, exhausted and emotionally a mess. With all that needs to happen in this crazy world when two become one, and adjusting to life without my partner in work and most all other things, and my best freind of many decades, I realize I am not as strong as I was raised to imagine...  So until this new DAC, I mainly have been working on relatively low key refinements of already tuned things in the system, modifications, system tuning, and immersion in the music good medicine. And now that I am digging in deeper again, enjoying being back to the MKIV quite a lot, there is no real pressure on the MKIII now, my 300B and 845 amps more priorities, but also a little daunting to get to being heavy and high voltage. One day!

I can say though that my changeover to film in the MKIV was too gradual to make conclusive overall observations on the effects. But once I got the capacitance and main cap and bypass choices relatively right for each area of the power supply, each phase was a nice improvement here. So I bet if done all at once, it would have been pretty impressive ...

But I am getting worked up again unrelated to VRs, so how about I write more on this over on your main thread? And thank you for the offer of the parts and music!

freaty