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Tubecube 7


steelgtr

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Mine: Tubecube > Cornwalls. / Sovtek EL84M's and a Sovtek 12AX7LPS. (spoiler alert: 2 thumbs up)

 

My previous (and first) tube amp was a Japanese SEP manufactured in the 1960's (6BM8 power tubes--alternating between Matsushita and Sovtek; 2 12ax7's; 1 Sylvania 6x4 rectifier). This had been my best amp for 2 channel music; the separation, depth of sound-stage was noticeably better than my SS amps... One day, I bought the Tubecube on a whim... and powering it up for the first time, I was struck by improved bass in the first few seconds of the first track. No hyperbole--I wasn't "blown away" or anything like that... but, immediately and without any hesitation I could sense this little amp was the clear winner of the two amps. It was obvious. Time passed, and I sold the Japanese amp... .

 

So, for anyone wanting to try tubes for the first time, or those on a budget... I can think of no reservations. The previous post @AndreG. about combining a TubeCube with a Schiit pre sounds like a great idea (room-correction? why, yes, thank you!).

 

[Re: power - even on rare occasions when I've got it playing loud--the volume pot is not over 50%; for normal listening it stays between 15–30%. If you need to be heard through hearing protection at the Canadian lumberjack nationals, obviously, this isn't the amp; but if you're playing music at home with anything Heritage--I would not expect power issues of any kind. Added bonus: for owners of 4 ohm Heritage... we've got 4, 6 and 8 ohm taps.]

 

I'm pressing myself to come up with some negatives... Here's a big one: Its made in China. Can't think of anything else. I wonder what Schiit would need to charge to make their own version of this? The original design is from England, if I recall; MiniwattN2, or something?. I would easily pay much more for one of these, if made here in the U.S--or, somewhere in Europe. But it isn't.

 

 

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  • 5 months later...
  • 2 months later...

 

 

On 4/17/2021 at 2:08 AM, Ole Dollar said:

I have a Tubecube 7 that has NOS Mullard EL84s and 12AX7. Playing through a pair of Heresy speakers and a subwoofer it sounds pretty amazing. Has a great 3D sound stage and good cymbal coverage. The sub picks up the lower frequencies  as the Tubecube is 3.5 watts per channel. Using a iFi DAC and iPhone for tunes. Have taken this setup on vacation with RB51ii bookshelf speakers, fits in a medium size bin. Really is a nice sounding amp and not a fan of the SINO tubes that come with it, amp really came alive when NOS Mullards installed.

So I have to ask a really dumb question, How can you know you are getting new old stock vs say a regular EL84? Tube depot offers NOS for almost 200 but I see Mullard EL84 matched (4 tubes) for 87.00. is "NOS" new old stock meaning some shift in manufacturing has made a serious impact on this tube and the original more desirable? Or is just aesthetic?

Please forgive my ignorance in tube rolling, just beginning the journey.

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8 minutes ago, sbcoffey42 said:

 

 

So I have to ask a really dumb question, How can you know you are getting new old stock vs say a regular EL84? Tube depot offers NOS for almost 200 but I see Mullard EL84 matched (4 tubes) for 87.00. is "NOS" new old stock meaning some shift in manufacturing has made a serious impact on this tube and the original more desirable? Or is just aesthetic?

Please forgive my ignorance in tube rolling, just beginning the journey.

Newly produced EL84 tubes cost between 10 and 25 euros/dollars. Some of them produce great sound. 

NOS EL84 tubes cost more and they date back to the 1950s, 1960s. They are desirable for guitarists for example, because it allows them to create that typical timeperiod sound, if used with the vintage guitar amp. 

Audiophiles like nos tubes because they believe the last longer and were made better, and therefore sound better. 

You can recognize nos tubes by their packaging (can be forged) and by the etching on the glass ( can be forged too). 

I've used new and nos Sovtek tubes with my Tubecube 7, and I can hardly tell the difference. 

Last but not least, the pre-amp tube affects the sound more than the power tubes. 

 

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1 hour ago, sbcoffey42 said:

 

 

So I have to ask a really dumb question, How can you know you are getting new old stock vs say a regular EL84? Tube depot offers NOS for almost 200 but I see Mullard EL84 matched (4 tubes) for 87.00. is "NOS" new old stock meaning some shift in manufacturing has made a serious impact on this tube and the original more desirable? Or is just aesthetic?

Please forgive my ignorance in tube rolling, just beginning the journey.

Your question is very plausible I would say. My answer in short NOS (if one gets no fake) is light years ahead of the new production tubes from New Sensor.

 

Unfortunately, sometimes it is crazy what NOS tubes should cost, but on the other hand it is shocking how bad in comparison today's many fake brands come from one and the same factory in Russia.
A clever American businessman had bought up all the naming rights of old glorious brands as well as Mullard and others.
Below in the link it is about an ECC83 genuine Mullard vs new fake Mullard and not about an EL84, but the analysis is more than sobering.
The only major difference between all the New Sensor brands and accordingly the main investment is in the printing of beautiful colorful outer boxes. These boxes have more in common with the NOS boxes than the tubes themselves.

https://www.effectrode.com/knowledge-base/mullard-ecc83-12ax7-reissue-vs-original-a-physical-comparison/

 

Here is some talk about the manufacturers which are left. Even if the New Sensor brands sound different from each other, the quality is the same.

 

https://forums.stevehoffman.tv/threads/list-of-current-production-tube-valve-manufacturers-and-brands.1043922/

 

long life I have not noticed so far with a single New Sensor tube. The worst was my experience with the most expensive tube, the imitation Gold Lion ECC83. Bought three and all were scratchy and broken after a month. All in a Mcintosh amp where other tubes last 10000 hours.

They have the various New Sensor brands partly spiced with different sound but the product quality is the same lousy with all of the pseudo brands.

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3 hours ago, sbcoffey42 said:

 

 

So I have to ask a really dumb question, How can you know you are getting new old stock vs say a regular EL84? Tube depot offers NOS for almost 200 but I see Mullard EL84 matched (4 tubes) for 87.00. is "NOS" new old stock meaning some shift in manufacturing has made a serious impact on this tube and the original more desirable? Or is just aesthetic?

Please forgive my ignorance in tube rolling, just beginning the journey.

 

The vast majority of tubes being produced today are made in 2 plants, one in Russia and the other in China. The names like Mullard and Tung Sol have been sold and to be used for advertising, they are not the same company that originally made them.

 

Some of the current production tubes are very good but many of your regular audio receiving tubes like EL84 and 12AX7 are not as good as some of the old ones. Since they are no longer in production supply and demand has skyrocketed the price. If your circuit is sensitive to tube quality, usually open loop designs with little to no feedback globally or locally then you will hear differences with all tubes. It's considered good engineering to have the overall circuit performance not critically rely on one specific device's linearity, negative feedback will make differences between tubes a non-issue.

 

 

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12 hours ago, sbcoffey42 said:

 

 

So I have to ask a really dumb question, How can you know you are getting new old stock vs say a regular EL84? Tube depot offers NOS for almost 200 but I see Mullard EL84 matched (4 tubes) for 87.00. is "NOS" new old stock meaning some shift in manufacturing has made a serious impact on this tube and the original more desirable? Or is just aesthetic?

Please forgive my ignorance in tube rolling, just beginning the journey.

I would like to add that my experience with JJ tubes has been quite good. These tubes are manufactured exclusively in Slovakia and only JJ tubes are manufactured there.
This is not brand deception or product lies.

JJ took over (in the 1990s?) the production machines from Tesla in Czech Republic. Tesla tubes had an excellent reputation, e.g. the KT88 was produced under license of Marconi-Osram in good quality for the Eastern Bloc.

Tesla took over the machines for the production of the ECC83 and other tubes from Telefunken in the 70s. These machines were later taken over by JJ.
Due to confusing naming of the different companies, it is defacto so that who buys today the very ordinary simplest and cheapest ECC83 from JJ in reality receives a grid tube which was called ECC803S at Telefunken.

 

https://www.jjtubes.eu/

 

I am just a happy customer and I prefer a company which respects heritage against one with fantasy brand fakes.

 

 

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It looks like tubes may just be the rabbit hole I was looking for. I think it’s time to break out all my tube documentation from electronics school and refresh myself. I can see why people go deep into tubes, with so many factors of design impacting sound how could you ever possibly just settle on one amp.

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The 6P14P is a Russian tube that one can substitute for the EL84 and they can be NOS and bought at a reasonable price. I personally use 6P15P's in my EL84 PP amplifier which work and sound great but one has to connect pin 3 and 6 together at the socket being the EL84 and 6P14P have pins 3 and 6 connected internally and the 6P15P does not. The designer of my EL84 amplifier tested the 6P15P's against the EL84 and agreed with me about sounding as good or better. 

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For 180 bucks I think I am going to go ahead and take the plunge. I have a set of Heresy's so i should be just fine. After reading as much as I could this looks like the right investment to get my legs under me on the tube journey. it seems like if one were so inclined that the caps could be replaced with better ones. I know some of those Chinese caps dry out and pretty much turn into resistors. But in all I can't see any info that says stay away.

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On 1/24/2022 at 1:02 AM, KT88 said:

Your question is very plausible I would say. My answer in short NOS (if one gets no fake) is light years ahead of the new production tubes from New Sensor.

 

Unfortunately, sometimes it is crazy what NOS tubes should cost, but on the other hand it is shocking how bad in comparison today's many fake brands come from one and the same factory in Russia.
A clever American businessman had bought up all the naming rights of old glorious brands as well as Mullard and others.
Below in the link it is about an ECC83 genuine Mullard vs new fake Mullard and not about an EL84, but the analysis is more than sobering.
The only major difference between all the New Sensor brands and accordingly the main investment is in the printing of beautiful colorful outer boxes. These boxes have more in common with the NOS boxes than the tubes themselves.

https://www.effectrode.com/knowledge-base/mullard-ecc83-12ax7-reissue-vs-original-a-physical-comparison/

 

Here is some talk about the manufacturers which are left. Even if the New Sensor brands sound different from each other, the quality is the same.

 

https://forums.stevehoffman.tv/threads/list-of-current-production-tube-valve-manufacturers-and-brands.1043922/

 

long life I have not noticed so far with a single New Sensor tube. The worst was my experience with the most expensive tube, the imitation Gold Lion ECC83. Bought three and all were scratchy and broken after a month. All in a Mcintosh amp where other tubes last 10000 hours.

They have the various New Sensor brands partly spiced with different sound but the product quality is the same lousy with all of the pseudo brands.

 

Thank you for posting this. I was intrigued by this and checked my tubes.

I have these 12AX7tubes in my possession:

  • NOS Sovtek that came with my Leben CS300 (see picture, on the left, no etching or markings)
  • Genalex made in Russia Gold Lion 
  • New stock Sovtek 12AX7LPS (not in the picture, because they are currently in my Leben amp)

Even if both tubes were made in Russian, I can confirm the observations described at effectrode.com:

  • they feel different: the Gold Lion is thicker and heavier
  • they look different: 
    • The glass:  NOS Sovtek (no etching, no markings),  Gold Lion (beatiful gold printing, markings)
    • the getter: NOS Sovtek (a ring),  Gold Lion (a saucer)
    • the plates:  NOS Sovtek (about 1cm long),  Gold Lion (about 1,5 cm long)

etcetera...

 

The new old stock Sovtek tubes are completely different inside, that's my conclusion. Just look at the picture.

 

Let me explain about the many iterations of the Leben Hifi CS300. The Japanese company's engineer and owner builds and designs them around the stock of tubes he has. When his stock has expired, taking into account replacements for the owners, he buys a new stock of good quality nos tubes, and redesigns the CS300, moving on to the next model: the CS300XS, the CS300F etc.

 

While I'm typing this, I am listening to the Tubecube 7 with the nos Sovtek EL84 and nos Sovtek 12AX7 tubes, connected to my Klipsch RP160Ms (close listening). They sound amazing. .... I wish I could put them back in my Leben CS300, for sure, but unfortunately, one of them is faulty (they were in use for about 15 years), and I have no idea where to buy them.

 

 

 

 

PSX_20220125_084524.jpg

PSX_20220125_084626.jpg

PSX_20220103_103645.jpg

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Will anyone be willing to open one up and take some pictures for us?

 

Has anyone drawn up a schematic from one? I can probably do it from pictures if posted.

 

My guess is it's a simple 12AX7 common cathode gain stage AC coupled to the EL84 wired for pentode operation. I don't think there is any global feedback as the measurements are that great, at 1 watt there is not much above 10kHz. If you stay under 1 watt performance is ok but at 3.5 watts I wouldn't consider it 'hifi' but I am sure it sounds good measurements be damned.

 

There seems to be a huge market for inexpensive tube equipment for people to play around with. I have been thinking of designing a small amplifier like this for forum members except with much better performance.

 

For $200 I am thinking I can do at least 5 watts per channel, I'll shoot for 10 watts but size will need to be larger with less than 1% THD at full output power 20-20kHz.

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12 minutes ago, captainbeefheart said:

If you stay under 1 watt performance is ok but at 3.5 watts I wouldn't consider it 'hifi' but I am sure it sounds good measurements be damned.

 

You are right about that! You need efficient speakers for the Tubecube  7, and it doesn't play extremely loud.

I cannot open mine, because it has screws in the shape of triangles: 🔺

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20 minutes ago, captainbeefheart said:

Will anyone be willing to open one up and take some pictures for us?

 

Has anyone drawn up a schematic from one? I can probably do it from pictures if posted.

 

My guess is it's a simple 12AX7 common cathode gain stage AC coupled to the EL84 wired for pentode operation. I don't think there is any global feedback as the measurements are that great, at 1 watt there is not much above 10kHz. If you stay under 1 watt performance is ok but at 3.5 watts I wouldn't consider it 'hifi' but I am sure it sounds good measurements be damned.

 

There seems to be a huge market for inexpensive tube equipment for people to play around with. I have been thinking of designing a small amplifier like this for forum members except with much better performance.

 

For $200 I am thinking I can do at least 5 watts per channel, I'll shoot for 10 watts but size will need to be larger with less than 1% THD at full output power 20-20kHz.

 

Here there are pictures and schematics:

https://www.diyaudio.com/community/threads/tubecube-7-pcb-inspection.346994/ 

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