AudioCircle
Audio/Video Gear and Systems => Tube-o-phile Circle => Topic started by: -Richard- on 30 Sep 2011, 02:10 am
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The Almarro A318B is a new amplifier for me... my current "research" has brought me to it because of the 18 watts per channel it is rated as having (not the A model which has problems with extension and exhibits less power)... it uses the infamous 6C33C Russian double triode tube (Lamm loves to use this tube, Quick-Silver also has an amp that uses it) that helped to make the Russian mig airplanes fly.
The 6C33B has 3 nipples on the top... quite "sexy" in its way... the reviews are good... although not "consistent" with some reviewers contradicting others on where it plays (detailed, not detailed, more like SS, could be dry, anything but dry and so on). That tells me that it must reflect, perhaps more than some other SET amps, the auxiliary equipment being used... or perhaps it has a somewhat mercurial nature.
Does anyone here have experience with this amplifier? If so what is your take on it? Also, could you compare it to a 2A3 or 45 tube SET if you also have experience with that as well?
One thing I have heard is that the 6C33C double triode tube will probably need to be replaced every 9 months assuming it is played 2 hours every day... I was told that they are around $40 to $50 per tube ($100 the pair)... but I have not checked those prices myself.
Thanks in advance for any feedback.
With Warmest Regards ~ Richard
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Hello:
Never listen this amp, looks it sound good, but if it sound bad, the guilty is not the 6C33 tube.
There is various amps sounding great with this tube.
I bought my 6C33 tubes direct from Moscow at GSTube at 10 Euros each:
http://www.gstube.com/catalog/?key=6C33&bl=&mmm=0&aaa=0&valuta=978
About the 6C33 time life I found this below, by Victor Khomenko-BAT:
6C33 TIME LIFE:
At 50% stress it is virtually indefinite, at 95% it is in the few months category.
It would help if you could quote the plate voltage and plate current that is seen by the tubes.
Plate voltage is the DC voltage measured if you put one probe on the plate and the other on the cathode. To measure plate or bias current, you most likely would have to measure the voltage drop across a cathode resistor, if one is present. Then calculate the current using Ohm's Law. Sorry, if you already know all this. In my amps, the 6C33Cs see about 42W plate dissipation (plate voltage X plate current), and the tubes last for years.
I think they are rated or 60W max. They get blazing hot, no matter what, due to the filaments. This causes trouble with the tube socket. You might want to check out your tube sockets, if you determine that you are operating the tubes within safe limits and still getting rapid failures.
The tube is rated 60W, at 45W(the tube not the amp) steady state plate dissipation you can expect years of service. When your stress gets into 55W or so, expect months. Some tubes will start losing their getters fast at power at levels approaching 60W.
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Hi Fullrangeman ~
I am deeply indebted to you for your thorough insights into the 6C33 tube issues. I have read several posts/reviews that are consistent with your observations... but no one has clearly laid-out the specs and measurements as you have and it is very helpful.
It is interesting that Lamm uses the 6C33C tube in its $30,000 SET amplifier.
I am speaking with a dealer today who is looking up the plate current for me... I will ask him for the plate voltage as well. I mentioned to him the issue with the sockets... he claims that there has been no failures that he is aware of... but that is just one person and I do not think he sells many of them.
It seems this tube has a reputation for sounding quite extraordinarily rich in the mid-range... with unexpectedly deep bass and "airy" highs that do not exhibit any glare. That it can generate high watts for an SET is one of its unique characteristics... and of course it can keep you warm during cold winters... I have read that it is blazing hot. But I am excited about it apparently sounding somewhere between a 2A3 and 845 tube. Apparently not as "detailed" as a 45 tube but extraordinarily musical. One reviewer said a tube for the heart and not the head... still, Srajan's review counters that by suggesting it sounds like his Yamamoto 45?... so it is anyone's guess what it would sound like on my OB's.
What amp are you using, Fullrangeman, that uses the 6C33 tube? Also what is the circuit typology and how does it sound to you.
I am also deeply grateful to you for supplying a link to your Russian tube source. Thanks so much.
With Warmest Regards ~ Richard
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Dear Richard:
Thankyou for your kind words. Iam yet running a sterille SolidState amp(a old Carver Silver 9T), but Iam storing 6C33 and GM70 tubes, as the price is low now.
By the little I know, there is more other ways of get long tube life:
1- Respecting the times of cathode heating, before releasing the high voltage(grid and B+), as shown below:
ABOUT THE 6C33 WARM-UP TIMES: =>> According the Michael Boele 2005 datasheet.
Warm-up time to 90% emission= 120 seconds
Minimum warm-up time is 120 seconds
Warm-up time to steady state = 600 seconds
2- Very Slow turn on, the expensives Joule-Electra OTLs use a Variac to +-15seconds manual turn on the cathode heating, as result Joule-Electra claim his output tubes last 5K hours and even in some custumers long 10K hours on 6C33 tubes.
3- Mandatory two power on switches, one for Cathode heathing, other for the hi voltage(Grid & B+), as used on the Atma-Sphere OTLs.
For more info see the post 12 on this topic at NiteShade sub-forum:
http://www.audiocircle.com/index.php?topic=98777.0
Best wishes in this your purchase,
Gustavo
OBS.: Once I listen an BAT VK75SE(Stereo, Circletron with two 6C33 p/c) and it sounded very good and unfatiguing even after 4 hours listening. :thumb:
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Hi Richard,
It is good to finally be able to help you with a question. You have helped me many times.
I owned the Almarro A318B a couple of years ago and really enjoyed it. I sold it after having it for about one year.
It is one of my favorite amplifiers and that is from a pretty long list that have come and gone.
I will warn you that it generates more heat than any other tube equipment or class a solid state amps I have owned. You have to have an open rack/stand/area and make sure children and pets stay away for safety.
At the time I owned a pair 96db two way speakers using Supravox mid/bass driver with dipole tweeters and ultra premium crossovers. They were incredibly revealing speakers.
The Almarro A318B sounds much more powerful than the rated power. It has serious power and control over the drivers.
I found the sound quality extremely impressive. It provided a huge sound in my room with very linear sound.
I found it very well balanced throughout the frequency spectrum. Your open baffle speakers will probably be a very nice match for this amplifier.
You will have plenty of power to spare.
The only issue I will mention is that I did have some hum with the amp in my system. I understand it was not unique to my A318B. If your system is incredibly revealing which I believe your system is it may or may not pose an issue for you. I guess it depends how critical you are about hum or noise floor.
I am very sensitive to any noise or hum. I prefer trying to get a silent background from my system. I feel that way I get more out of my system.
Even after saying that I have found myself close to buying another one.
It is a fantastic value and wonderful sounding amplifier. I really like Almarro based on my experience with this amplifier.
Their monoblocks they have recently come out with look amazing. If I had deep audio pockets I would love to buy a pair of them. With a 7 month old son audio is taking a backseat!
Good luck with your search and I hope you get to try the A318B out in your system. I highly recommend it if the heat is not an issue in your setup.
Best Regards,
Nick
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Richard,
I owned the A318A some years ago, and I'm not sure how different the B model is from the A (so consider my observations with that in mind). I liked the A well enough, but it didn't sound to me like a SET amp. It sounded like a tube amp, but lacked the DHT qualities of a 300B, 45, or 2A3 amp (which I went back to after the Almarro). I also remember the bias drifting wildly on the 6C33 tubes...it was something I was constantly checking.
FWIW...
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ACRESM22:
Some experts in the 6C33 say it is normal this tube flutter the BIAS in the first 100 hours or so, so this problem not Almarro fault, thus as the Bias is manual, it is need adjust every hour or so.
A word in favor of manual Bias, this is the Bias system that less interferes with the sound.
Regards
P.S.> If the tube is old and do not keep Bias anymore, you know it is time to change the tube, but if the Bias is automatic this control system of tube time life gone.
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Thank you Nick and acresm22... I could not hope for more direct and thoughtful observations and feedback with your experiences with the Almarro A318B.
The "hum" issue may well be too much of a problem for me, Nick... I cannot thank you enough for bringing to that my attention. Also "powerful" as a sound-quality characteristic is not what I am looking for... reading your very thoughtfully written observations has helped me to realize that I am actually looking for a "refined" sense of texture... yes... tonally rich... that is important. But I would love to get violins to sound more transparent for example, if that is possible.
Your observation, acresm22, that it "sounded like a tube amp, but lacked the Directly Heated Triode qualities of a 300B, 45, or 2A3 (tube) amp"... is of very great interest to me.
Thank you Gustavo for your in-depth insights into extending the life of the 6C33C tube... I deeply appreciate it.
Admittedly... I think I am looking for that DHT sound... once lived with... it is hard to dismiss it... there is a certain captivating sense of what some reveiwers discribe as a "lite from within" quality. But it has been quite some time sense I have heard it... and I don't know if now it would still sound the same to me.
I live in Ojai, California... not too far from here, in Santa Barbara, there is the Music Academy of the West... a music school for aspiring young talented classical musicians that is considered one of the finest schools of its kind in the world.
Each year in the summer, students from all over the US and the world are invited to the MA of the W to learn directly from the worlds greatest musicians. They open their doors free of charge for visitors interested in attending their workshops, where the students are placed under the microscope to bring their skills to the highest level they are capable of.
Deborah have started to attend these student workshop "performances" which lasts for a week, covering almost every instrument of the classical repertoire. So for several days we listen in various rooms to instruments and voice playing a spectacular range of classical music from very early to just-written.
That experience has changed my sense of what "audio" can actually "grasp" in terms of touching something of what real unamplified voices and instruments actually sound like.
This ongoing experience with real instrumental playing in real rooms has definitely altered my perception of what I am after now in my home listening experience. Also I have taken up the classical guitar... which I am moving into very slowly with no intention of mastering it... I am in the midst of working on a new series of paintings that demand a tremendous amount of time to work out. Still playing it every day... even if it is reviewing simple scales... also brings me back to the sound of "real".
So will the rarefied and highly seductive sound of DHT still create that sense of magic for me, given my recent experience with real instruments and real voice? I just don't know. But if the Almarro does sound more like a well designed "tube" amplifier with a little less of that DHT magic, it may not be what I am looking for.
For anyone interested in some further information about the Almarro A318A SET amplifier, here is a recent email I received from Hiro, the son of the designer:
Dear Mr.Waxberg,
I am answering your questions.
1. What is the plate voltage and plate current of the 6C33C during NORMAL operation in the A318B SET amplifier?
Plate voltage 280V
Plate current 180mA
2. Does the A318B use any feedback? There is conflicting information about this in reviews.
The A318B uses NFB. (Negative Feed Back)
3. Srajan of 6-moons suggests that if the plate voltage is turned up, the "holographic" or dimensional qualities of the tube increase. What is the maximum plate voltage that is safe to run the 6C33 tube and still achieve its desired characteristics?
I think it is depend on types of 6C33C. One we use are capable to 400V.
4. Some reviewers feel that the A318B SET amplifier lacks "detail" and appeals to the "emotional" side of music... which is quite alright... are there replacement tubes for the 1x6SL7, 1x6SN7 tubes that could help to bring out a little more detail?
It could but I have never tested other tubes of 6H8C and 6H9C so I really cannot say my opinion.
5. How much do you charge for tube replacements for the 6C33C's (pairs or singly)?
I have never sold a pair of 6C33C tubes to customer directly. I have sold them to dealers or distributors. I guess your price would be around U.S.$200 for a matched pair of 6C33C with 6 hours of aging.
6. If the amplifier needs servicing, where do I send it to?
Harmonyaudio
ATTN: Jay Waxler
401 Glendora Drive
Bloomington, IN 47408
USA
7. Is there still a 5-year warranty of the A318B SET amplifier?
Almarro used to offer 5 years warranty but I changed it about 3 years ago. Almarro amplifiers are not very expensive amplifier and we cannot afford to offer 5 years warranty. Now it is 1 year warranty.
8. To check biasing during the first 100 hours until the C633C stabilize... what instrument do I need? I have a sound-level meter... will that work?
You only need voltage meter, which you should be able to buy one at Radioshock for $20.
Best regards,
Almarro Products
Hiro
3489-24 Kitagata
Iida Nagano 395-0151/JAPAN
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Thanks everyone for your very helpful and thoughtful insights... I truly appreciate it.
With Warmest Regards ~ Richard
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Dear Richard,
I did not know you are an artist, congratulations for it, in my teenage life, I was very inspired and painted some original paintings and some copies of Striker in oil paint, it is a very relaxing work.
I read in a 318B test it use just 6dB of NFB, the usual in some famous amps are near 20dB or more.
I sent a PM to you about DHT.
Cheers