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Help replacing tubes for the ToriiMK5 (Read 402 times)
Coqui
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Help replacing tubes for the ToriiMK5
04/02/25 at 12:50:56
 
This is my first time replacing tubes for my ToriiMK5 or any other amplifier. I have a loud hum coming from the left channel that I would like to fix. I spoke with Steve and he indicated that it is most likely a bad rectifier, input, and/or tube regulator. I have a few very basic questions:

1) For the tube rectifier, does it matter if it is a 5U4G or a 5U4GB instead of a 5u4? I noticed that Decware has the 5AR4 available but the 5U4G is out of stock. Should I buy a 5AR4?

2) For the input tubes, are there any alternative to using 6N1P or a 6922 tubes?

3) For the input tube regulation, are there any alternative to using the VR75 or VR150?

I know that these are very basic questions. This is my first tube amplifier and the first time I buy any tubes on my own. I would really appreciate the assistance of the more experienced members in this regard. Thanks!
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GroovySauce
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Re: Help replacing tubes for the ToriiMK5
Reply #1 - 04/02/25 at 14:03:27
 
More input tube options: 7DJ8, 6DJ8, E88CC, ECC88, 6N23P, 6N5P

Rectifier: 5U4, 5U4G, 5U4GB, 5AR4, 5Z4 (octal base most have 4 pin base), 5Y3(GT), Some 274b the old ones no modern ones sometimes. The original specs for the 274b isn’t compatible.) the Torii MKV has a 8uf cap and the original 274b required a max of 4uf cap. There are a few others I cannot think of off the top of my head.

VR Tubes: I would stick with the 0A3. You can try 0B3 and 0C3 even 0D3

0A3 – 75 volts = VR75
0B3 – 90 volts
0C3 – 105 volts
0D3 – 150 volts
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Lon
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Re: Help replacing tubes for the ToriiMK5
Reply #2 - 04/02/25 at 14:04:47
 
Both of those rectifiers will work properly in the amp.

There are a number of input tubes that will work as far as I know (I never have had a Torii Mk V, I did have Torii Mk IIIs).In general, in my experience the 6N1P and 6922/6DJ8 types worked best. But 7DJ8, 6N5P and others can work.

You can also use VR90 (0B3) or VR105 (0C3) I believe. I found VR90 (0B3) to be my favorite in the Torii Mk III.

Hopefully Torii Mk V owners will chime in and correct any erroneous information I posted and offer more opinions.
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Coqui
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Re: Help replacing tubes for the ToriiMK5
Reply #3 - 04/02/25 at 16:07:42
 
Thanks so much for your response! I will order tubes with your suggestions in mind. I will report back and let you know if adding new tubes fixes the issue with the noise.
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Coqui
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Re: Help replacing tubes for the ToriiMK5
Reply #4 - 04/02/25 at 16:39:22
 
Hello Lon and GroovySauce,
I ordered a pair of OA3's and a pair of 5U4G's from Decware. I will try replacing the OA3's first and see if that solves the problem. If not, I will replace the 5U4G's. I will consider replacing the input tubes if those two changes do not solve my problem.

Once again, thanks so much for your help!
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Lon
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Re: Help replacing tubes for the ToriiMK5
Reply #5 - 04/02/25 at 17:00:15
 
Good luck, hope one of these pairs does the trick.
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will
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Re: Help replacing tubes for the ToriiMK5
Reply #6 - 04/02/25 at 17:26:07
 
Another way you can get a hum on one side is if an IC has a weak ground connection. I have one I need to replace the end on that is a KLE sort of design with a little ground connector on one side. It has gotten loose, so the IC needs to have a little tension on it to get that little ground nub to connect well and not cause a hum. But I agree, it is often a tube. Why is it good to have spares of each type, for troubleshooting and maybe fixes, but as much for me, having a little variety can be really nice for shaping the sound. This led me to having a ridiculous number of many types gathered over time. And they all sound different, making refining a room's sound by mixing and matching a pretty powerful tool.

I have not heard a MKV either, using a MKIV now that I modified over time to be more resolving, fast, complex. It allows the signal through so easily, I most often prefer less potent tubes, easier/cleaner flow, more powerful tubes can be overstated. Also, my preferences are for a little tube euphonic quality, but more about speed, resolution... lack of smearing, so going for euphonic "warmth" more as subtle musicality enhancement than an obviously "tube sound."

With the MKV design changes, improving stock parts and wires, more resolving output transformers, inverter tubes, lower capacitance rectifier power... guessing yours sounds faster, more spacious and resolved than my MKIV did stock, but not having heard it, and tubes so affected by the amp design, I can only point to tube characteristics you might apply to whatever sound changes in your setting you might prefer.

As I recall, 5U4GBs are generally a little denser and more powerful feeling than STs, while the nice ones (to me) can also be a little more obviously textured, and the signal contrasting spaciousness and a little denser sound more...But some are really close to good 5U4G-STs also, so it is always interesting to see what a tube actually sounds like once in hand.... and all tubes affected by each other, so can't say conclusively what would be best there.... But GB's tendencies for a little more powered sense of signal can be really good, or it can be overstated. In my warm leaning setup, and with the remaining low bass issues I have here, that extra push is more obvious in the bass than elsewhere. So when I was using GBs a lot, I took care to compensate with more open and fast tubes, or the extra bass could off balance with the rest, becoming strong enough to thicken, slow and reduce definition some. Good sound still, but not my thing, needing fast and complex bass that blends smoothly with resolution and speed everywhere else. But if you need a little more weight, bass, density, nice NOS GBs can be pretty cheap, and it might be fun to pick up a few to try and see how you like them.

Nice 5U4G-STs are not all that different in the broader sense, but to me, being a little less powerful feeling in general, they tend to be a little more neutral, and a little less obvious in all they do, nicer ones balanced and more nuanced, which can also be really nice. But this is really general, every tube having its own sound influences.

5AR4/GZ34 generally make the signal faster and more dynamic with a similar signal push as 5U4G types. GZ32s were my preference here, a less forceful, even faster and more open version of the GZ34s sound-wise. But again, they helped here by opening things up, where in a leaner setup, they could be too open, fast, and lean. I have tried some of the new GZ34s, and did not think they were great, but I have a lot of nice tubes I picked up over years, and many of them really pretty exceptional sounding. The last new ones I tried Psvanes, were decent, but, compared to NOS versions, they were a little held back, slightly masked, and flatter the way the system sounds these days. But NOS have gotten really costly, and again it all depends on everything else. So if a punchier sound that sets up contrasts between signal and space might help you get a sound you prefer, trying a pair of new 5AR4s that people rate well could be a fun experiment.

I like, but never loved 6N1Ps in my Toriis, again, preferring less warmth, and more fine detail, speed and space in my setup.  And E88CC/6922s, though many love them, were always a little too forceful for me. So I used nice NOS euro ECC88 types a lot. And before opening up the sound using more resolving and fast amp parts and wires, I tended to use PCC88s, sort of like the GZ rectifiers... tending to be punchier, more open, faster. Lately I am leaning toward using either pretty neutral 6CG7s or transparent, dynamic, and resolving Linlai E-6SN7s with adapters. With the more powerfully expressive and transparent DAC I am working on, those tubes tending warmer, fuller, and smoother (though nicely resolved and complex) compared to the ECC88s types I tend to prefer (early 60s Heerlin made, or Siemens both being notably open, transparent and nicely balanced here). But I go back and forth.

GS pointing out VR ratings, those numbers are voltage drop. So an OA3 drops the voltage before the other tubes less, making it the one that gives the signal most power, which could be right with all else, or overstated. Where an OD3 drops the voltage the most, reducing signal power and giving the most open, nuanced, and delicate sound, which could be right, or too lean depending on all else. But if you need stronger signal power... a more pushed, dense and big sound with more bass power, OA3s are a good choice. And those too all sound different, so if you prefer them, not a bad idea to try other makes if you can find them. I like all VRs with the right company, but OA3s are generally too much here, and though I can get them all to sound really good, so far, I always end up back with OB3s in this setting.

Tubes can be fun, and daunting, especially in a resolving system/room that shows even the finest subtleties of so many different sonic characteristics between types, and with all the tubes within the types. And with practice and luck, finding synergy that takes the whole beyond their individual qualities can be enlightening.... how they blend together enhancing our sonic experience as much as the tubes themselves.

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Coqui
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Re: Help replacing tubes for the ToriiMK5
Reply #7 - 04/02/25 at 19:09:51
 
Wow Will, thanks so much for such a detailed and informative response!! I'm going to copy and paste it into a Word document so that I can study it and keep as a reference. My main concern at this time is getting rid of the hum. It is audible when I am listening a low levels and I find it a bit annoying. The best way that I could describe it is that it sounds like a bathroom fan but not was loud.

I'm just getting my feet wet in this hobby and I look forward to experimenting and finding out what combination of tubes will give me a sound that I really enjoy. Once again, thanks for taking the time and effort to write such a thoughtful response!
Ramón
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will
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Re: Help replacing tubes for the ToriiMK5
Reply #8 - 04/04/25 at 02:39:08
 
Glad to help Ramon.
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Dominick
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Re: Help replacing tubes for the ToriiMK5
Reply #9 - 04/12/25 at 20:45:43
 
Ramon,

Here is a quick response for now.  In terms of the rectifiers Steve recommends at some point to invest in a quality NOS rectifier after you have had your amp for a while.  .I’ll find that post and send it over.  I landed a matched pair of NOS Raytheon 5U4GB rectifiers and I really like them. It’s more dense than stock, and give the Torii a nice big sound.  My amplifier came stock with KT66 power tubes.  I have since moved away from them and now currently use the KT77 tubes and I think all around they are a better fit for my system.  I currently use the OD3 in my system, and while I like them…I plan to switch back to the stock OA3’s.   In Terms of the input tubes… I run  a pair of Tesla Gold Grid 6922s, and out of 6922 tubes… I do like a Tesla is the best so far.  

Just keep in mind that I have a Torii MKIV with the 25th Anniversay mods, which is different than yours.  Will’s MKIV is unique in that the majority of the internals are not stock and tuned to his ears.  I would love for someday to experience his amp as I’m sure it’s amazing.  You have to experiment for yourself what you like and what sounds good to your ears..but I have taken Will’s recommendation when I first got my amp, and he has never steered me wrong.
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CAJames
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Re: Help replacing tubes for the ToriiMK5
Reply #10 - 04/12/25 at 21:11:23
 
Here is the post by Steve, emphasis added by me. It is a few years old now and prices have gone up some but I think it still makes a lot of sense if you are new to tube amps.

Quote:
Posted by: Steve Deckert      Posted on: 06/22/20 at 22:08:32

Some great feedback regarding quality tubes...  

The beauty of a tube amp is that you can change the tubes.  You can change the tubes when they grow tired and lazy sounding over time... or you can change the tubes when you grow bored or just want to take a different seat in the music hall so that you can hear the music from a different perspective. So this leads to tube rolling which leads to brands and types... and here is some of what I know that you should know:


Current production vs. New Old Stock. In my experience the only consistently solid tubes on the market today come from Russia. Brands like Mullard, Tungsol, Electro Harmonix, Sovtek, Svetlana. The rights to these brand names have been acquired over the years by New Sensor Corp in the USA, who is predominately a tube supplier for the music industry / guitar amps. They own or partially own factories in Russia.

Decware purchases it's Russian tubes direct from Russia in bulk with the exception of the larger output tubes (EL34/KT66/KT88) which are current production branded tubes imported into the USA. All of the the Russian tubes that we purchase direct from Russia are N.O.S. Russian Military Grade tubes. Many of them have Gold grids, thick glass, high G ratings for missile use, and longer life, in some cases 10,000 hours.  These are ultra-hi-end tubes in disguise and have always been.   To hear how good these tubes are you have to install an American New Old Stock rectifier tube.

My experience with Boutique Chinese brands is mixed. The sound is good, the reliability and or consistency is ridiculous. I have been purchasing samples of these fancy tubes as they come out over the past many years and I have an entire collection of crippled tubes. Even KT88's that cost $1600 a quad drifted out of usable tolerance within days and had to be replaced.

New Old Stock is the real deal. Those who like to push the envelope of what is possible with their amplifier will often go down this path with no regrets. For one thing, the tubes not only sound better, but often last longer, in some cases like with rectifier tubes up to 10 times longer.

Rectifiers are a subject all in their own. Russian rectifiers are acceptable, everything else is a no-go from a reliability standpoint with some rare exceptions that are very pricey. My advise to all Decware amplifier owners is to find yourself a New Old Stock 5U4 or a 5R4 that has never been used and comes in it's original un-molested box. Consider the current production rectifier tube we ship with the amp the best sounding and most attractive  option that will last long enough for you to find a real N.O.S. replacement.

Finding N.O.S. tubes is easy, even on eBay there are millions. Since you only need one or two you will have more to choose from than you know what to do with.  Finding quantity of these tubes is another story. If Decware could secure reliable inventory of 1000's of N.O.S. rectifiers, it is an investment we would gladly make but in 25 years is has yet to happen. Because we can't find N.O.S. tubes in large quantities, even batches of 100 would be gone in less than 30 days, we feel there is no point in even trying.  

For the customer it is easy, just find a N.O.S. 5U4 tube on eBay that is unused, and in it's original box for $40 and it could easily last for 10 years or more and sound better the entire time.

As an amplifier designer, it is possible to create circuits that baby the rectifier tube by limiting inrush current, using smaller capacitors, running higher voltages with a choke and so on.  Correctly done, this can make a Chinese rectifier tube last the full rated 500 hours or more.  The problem with this is that it changes the sound quality of the amplifier well outside what we find acceptable.  So, we have to make a choice, do we design tube amplifiers to baby the crappie rectifier tubes being made today, or do we design amplifiers to use REAL tubes.  Of course the answer has to be REAL tubes, because we make real amps.
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hdrider
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Re: Help replacing tubes for the ToriiMK5
Reply #11 - Yesterday at 19:47:36
 
Coqui - Did you receive your tubes? Did that clear up the hum issue. I hope that other than the hum, things are going well. Happy Listening, Chris.
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Coqui
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Re: Help replacing tubes for the ToriiMK5
Reply #12 - Today at 00:22:49
 
Hello Chris,

Yes, I received the new tubes but the hum persisted. I sent the amp to Decware for repairs after a conversation with Steve. I am a couple of months away from receiving my Rachael and will need to decide which amp I am going to keep long term. I know that you have a Rachael and really like it! I will post my impressions of the Rachael when I get it.

Thanks for asking! I am doing well and I hope that you are well!
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