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90db and 6 Ohms do the job? (Read 2078 times)
gingerly
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90db and 6 Ohms do the job?
04/14/19 at 01:48:07
 
Prospective new Zen Triode owner here, wondering if my Nola Contender speakers (which measure 90db sensitivity and 6 Ohms fairly flat across the frequency range) might play well together in my smaller listening room.
Carl Marchisotto, the designer, LOVES tubes, so I'm leaning toward them possibly being quite compatible?

Any thoughts?
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Rivieraranch
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Re: 90db and 6 Ohms do the job?
Reply #1 - 04/14/19 at 13:21:30
 
Let me gingerly attempt to answer your question. I recall using Von  Schweikert monitors that were not all that efficient, maybe 89 dB. Then I also used Decware Trapeziums which are also 89 dB. Both were used with a 2watt Zen. The key is that you have a return policy for the amp if it doesnít drive your speakers to your liking. Just try it.
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MINI TORII ANNIVERSARY MODIFIED; SE84UFO; ZSTAGE; MONOLITH SPEAKERS; TECHNICS SL1200MK2 KAB MODDED TT; ONKYO 6 DISC CD; MARANTZ 2226B; SCHIIT MULTIBIT DAC; SENNHEISER HD-580 headphones
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slop
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Re: 90db and 6 Ohms do the job?
Reply #2 - 04/14/19 at 13:23:38
 
I've listened to the zen with Nola boxers in my living room and while it was good, the Nola's seemed to like an amp with a smidge more power and dampening. I'd look at some of decwares pp designs and talk w steve for sure. The contenders are great!
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gingerly
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Re: 90db and 6 Ohms do the job?
Reply #3 - 04/14/19 at 17:34:29
 
Good point about the eval period Mr. Ranch.

slop,

I LOVE my Contenders, and listened to many speakers (including the Boxers), including ones thousands of dollars more, and ones much more lauded (mid-range Harbeth, etc.).

Is the Zen Integrated (SE34I.5) a different circuit, or just two Super Zen Triodes (SE84UFO)?

I will definitely plan to talk to Steve.
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alper_yilmaz
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Re: 90db and 6 Ohms do the job?
Reply #4 - 04/14/19 at 22:42:10
 
Hi Gingerly.

I used to drive my 91dB, 4-ohm B&W's with my SE84UFO quite fine.  Before upgrading it to the SE84UFO25, I wanted to try it with my 88.5dB, 8-ohm ProAc's and even though it was not giving me kidney-stone removing volume, it is more than satisfactory!  With these amps, there is so much detail that you really do not want to crank it up anyway.  So if the specs of your speakers are true to the published specs (you'd never know in this industry if producers are providing the correct specs), I would say any Zen Triode amp would be more than enough to give you satisfactory volume levels.  My experience with the SE84UFO25 is even better; so my B&W's are not seeing any playing time anymore.

You need to consider one more thing though.  Whereas the EL84/SV83-based amps by Decware need 1.5V to reach full output, the EL34-based Rachael would need 2.5V.  So the latter would be happier seeing a source with higher gain.  In other words, a 2V-output source like a standard CD player might not feed the Rachael properly; so you would like a buffer stage or preamp before it.  

Of course, Steve would be giving you much more precise responses; definitely you should talk to him...

Cheers,

Alper
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Mac Mini with Roon, Rega RP6, Rotel RCD-1070 & Marantz CD6005; Hegel HD30 & Copland DAC215; Decware SE84UFO25, Decware SE34I.2+ & Copland CTA405; ProAc D28, B&W DM630 & Rega RS1; Stein and BlackNoise filters; DH Labs power, interconnect and speaker cables
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gingerly
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Re: 90db and 6 Ohms do the job?
Reply #5 - 05/22/19 at 23:28:30
 
Alper,

My DAC puts out 2v, so I think I will be OK. Listening will be primarily ripped/hi-res digital, with some vinyl.

Thanks everyone! I put in my order. I'll report back how it works out! Smiley
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gingerly
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Re: 90db and 6 Ohms do the job?
Reply #6 - 12/17/19 at 18:27:40
 
So, I've had my SE84UFO2 for a couple of months now.

At first I was using it with input straight from my DAC (a Micromega MyDAC with 2v output), the source being an older MacBook Air with Audirvana. This was amazing right out of the box, but the bass lacked solidity and felt a little slow and disconnected from the rest of the music. Still... the darkness of the space between notes, the shimmer of the highs and the separateness of the instruments was simply spectacular. At this point I was wondering if I could just live with the lack of bass articulation and weight.

Enter a Benchmark DAC1 I borrowed from work. With an impressive amount of variable output that goes much higher than the MyDAC, I wondered if using this as my preamp might make a difference. What a surprise this was. Despite my bias about adding extra components into the mix, and my general experience that the DAC1 was generally too dry to really enjoy sound wise, this was a COMPLETE sea-change. After tweaking the volume on the SE84UFO2, keeping it at about 3/4, the bass was back in spades, deep and fast, and playing along with the rest quite nicely. It all sounds so effortless, fast, and clean. It is, without doubt one of the finest pieces of amplification I have ever heard. Certainly a contender for my memory of the Audio Note Ongaku I heard years ago, but with a clarity I truly DON'T remember, if at the cost of some saturation in the color. I LOVE this thing!

Though I would be fine if NOTHING changed now, I admit I am excited to play with tubes, wondering if I can keep the speed and bass, but up the richness. Thus the madness begins...

So, I read some threads on tubes, and get the impression that it is hard to beat the stock video power tubes. I do have some GE EL84's I'll try just for fun. What do people like these days for the input tube, or rectifiers? I curious about the Globe 80's, but it seems hard to find one that doesn't blow quickly? What about the Sophia 274b? Which are the biggest bang for the buck?

I'm planning to pick up an RME ADI DAC2 to replace the Benchmark.
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busterfree
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Re: 90db and 6 Ohms do the job?
Reply #7 - 12/18/19 at 00:18:08
 
I like the Globe 80 with adapter. I blew through several, but I have had one in my SE84UFO25 for quite some time now. Sophia Aqua 274B is also nice but is expensive. I have one that is holding strong in my preamp.

It is nice to build a collection to swap out if you are into that. At least have back up tubes.
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Dominick
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Re: 90db and 6 Ohms do the job?
Reply #8 - 12/18/19 at 04:50:38
 
Gingerly,
I will be purchasing the SE84UFO25 next year, so I have been reading a lot about various tubes lately. †The Sophia Aqua 274B seems to get rave reviews from the guys here. †

I recently read a post about the EML 5u4G and it apparently got high praise right up there with the Sophia.

Here is the link to the product page...

http://www.emissionlabs.com/datasheets/EML5U4G.html

Itís an expensive tube like the Sophia, but if it has the hype that some praise, then it may be worth the purchase. †Personally...once I burn in my amp and start to tube roll...the EML 5u4G will probably be the first tube I consider to purchase and tube roll. †

Here the link to the Decware post about the EML Rectifier...

https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1549474856

The only thing that I would get more clarification on is that in the SE84UFO25 manual, it indicates tha the first capacitor after the rectifier is rated at 47uF. † The specs for the EML tube indicates that that the maximum number of the first capacitor should not exceed 40uF. †If it exceeds that value, the life of the tube would be shortened to like 70%. †While that wouldnít bother me that much, but it also states that itís not good for the capacitor lifetime. †That is what would cause some concern...replacing an external rectifier is one thing, but placing undue stress on the internal capacitor is more of an issue. †Unless... the difference in the values are so small that it nothing to worry about.

If anyone could chime in on what I just posted above, that would be truly helpful.

Dom
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iMac 7 or Google Chromecast Audio, Schiit Bifrost True Multibit DAC, My Audio Cables [MAC] Ultra Silver+ Cables, ZSB, ZSTAGE [Beeswax Caps], DAG Cables, Yamaha THX SS Receiver, Rega P3 Turntable, Velodyne Dual Firing Sub, Decware ERR Radials [Bubbinga Wood].
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Lon
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Re: 90db and 6 Ohms do the job?
Reply #9 - 12/19/19 at 13:40:48
 
Like Juan I have been using Type 80 for some time. I too have found the globe versions to be prone to failure in ways that coke bottle Type 80s are not. And I have one pair of old straight shouldered thin RCA Type 80s, like a 5Y3 but a bit taller, that are exceptional tubes--rich and textured and dynamic. My Taboo amps particularly like this tube.
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JOMAN
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Re: 90db and 6 Ohms do the job?
Reply #10 - 12/20/19 at 03:29:35
 
When I first started to roll tubes I did not appreciate how important the rectifier is.  The rectifier and VR tubes are the tubes that directly affect the power supply and therefore everything downstream.  If I were doing it again I would leave the stock power and input tubes and start with the Rectifier and VR tubes.

When considering the rectifier one also has to consider the first input cap value, and imo you will be taking a significant risk with any rectifier that is designed to work with a cap value significantly lower than 47uF.  Interestingly, the only time I had any short life and catastrophic failures was with tubes that were designed to work with a cap value of 47uF... the Sophia 274B Aqua, two of them.

I have used GZ32ís, 5U4G variants, 5Y3GT, and some others with no issues whatsoever despite the fact that the 5U4G variant was designed to work with a cap value of 40uF at best.  I concluded that as important as getting a rectifier with the right cap value is, itís just as important to get a rectifier that is robust in itís construction. The 5U4G variants that I used were built like the proverbial brick outhouse and often used in B&W TVís.

After the Sophias failed, I didnít want to take a chance again.  The challenge then was to get a rectifier that was at least as good as the Sophiaís were sonically.  After having the Sophia Aqua I could not settle for anything less.

The EML 5U4G was on the short list, a very short list.  However, the 40uF limitation bothered me so I called EML.  The person that I spoke with made it very clear that the tube was designed to work with a cap value of 40uF and could not comment on what sort of life it would have if it was used in a circuit that used a 47uF cap.  I appreciated the candor.

I also read a review that compared the EML to certain NOS tubes and the reviewer felt that as good as the EML was certain NOS tubes still had the edge.

Based on those comments and the comments of the person I spoke with at EML I decided to check out some of the more exotic NOS tubes and found that most fell significantly short of the 47uF cap value.  Those were too much of a risk for me, especially at the high prices that many of those tubes were being sold for.

I did end up with the Philips GZ34 Metal base (1 NOS and 1 used) which turned out to be as good sonically as the Sophia Aqua and in certain aspects better.  In fact, in some aspects quite unique from all other rectifiers that I had tried, that is for me and my tastes.

But... the GZ34 Metal base is one expensive tube.  However if it lasts for the next 20 years then it will cost $20.00 per year.  The two Sophiaís lasted for 1.5 years at $200.00 a piece or 267.00 per year.  Cost of initial purchase vs cost of actual use.  

So that no one gets the wrong idea from the above... I am NOT saying that the Sophia 274B Aqua is prone to failure.  That was my experience where as others have had good success with them.  There will be a certain rate of failure with anything that humans produce.

I am saying that the rectifier is very important and that as one purchases the pricier rectifiers risk management is critical.   Unfortunately no one can categorically state which brand or type gives great performance with zero risk.  I came to certain conclusions based on my experience.  Perhaps some of this experience can be of benefit to others.
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Dominick
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Still like that old
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Re: 90db and 6 Ohms do the job?
Reply #11 - 12/20/19 at 14:58:52
 
Quote:
The EML 5U4G was on the short list, a very short list. †However, the 40uF limitation bothered me so I called EML. †The person that I spoke with made it very clear that the tube was designed to work with a cap value of 40uF and could not comment on what sort of life it would have if it was used in a circuit that used a 47uF cap. †I appreciated the candor.


Joman.....when I read the notes section of the EML 5u4G tube, †it indicated that if if the cap exceeded the recommendation of the 40 uF, it would cause not only shorten the life of the tube, but also would place stress on the capacitor and shorten itís life). †

Here is what was listed in the note section...
Quote:
Notes
Note 2) To prevent large charge current peaks, the first capacitor (C1) should NOT be larger than 40uF. If the input capacitor is too large, this will result in heavy AC charge current through this capacitor. This is not good for the rectifier tube, and also not for the capacitor lifetime. The AC capacitor current peaks may cause hum radiation into the preamplifier. With the given C-L-C values in table, the rectifier circuit will work best. For filtering, with oversized components, you will have best results by increasing the choke. Do not oversize capacitor C1, this may increase hum. You can choose the choke large as you want. This will have better results with high voltage rectification.


A shortened tube life since itís an external component doesnít bother me as much ( unless itís something like 1/2 or more) BUT..... weakening the 1st capacitor definitely bothered me since itís an internal component. †

I would really love to find out from Steve his take on using a rectifier that exceeds the 1st capacitor rating of 7uF (40 uF vs 47 uF) and its overall potential damage to not only the 1st capacitor, but the rest of the internal components of the Zen Amp.

I am going to ask my sister who is an electrical engineer, but she designs power systems for buildings and does not build audio amplifiers. So Iím sure her take on the question is going to be very different than Steveís

Dom
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iMac 7 or Google Chromecast Audio, Schiit Bifrost True Multibit DAC, My Audio Cables [MAC] Ultra Silver+ Cables, ZSB, ZSTAGE [Beeswax Caps], DAG Cables, Yamaha THX SS Receiver, Rega P3 Turntable, Velodyne Dual Firing Sub, Decware ERR Radials [Bubbinga Wood].
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JOMAN
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Re: 90db and 6 Ohms do the job?
Reply #12 - 12/20/19 at 16:19:28
 
Dominick,

I did speak with Steve about this, but it was some time ago and I canít recall the details of the conversation other than to say that he indicated that another option is to use a variac on start up.  For me that was a no go.  Also I seem to recall that I mentioned that the AWV 5AS4 (5U4G variant) seemed to work very well and that these had a limitation of a cap of 40uF value, I also noted their very robust construction.  If memory serves, he seemed to indicate that was an offsetting factor that contributed to itís performance.

The research that I did seemed to indicate that there are many variables to take into consideration.  A lot of the information was beyond my limited knowledge on the subject and so I set my criteria for selecting the rectifier on what I could understand:

Choose one that was suitable for use with a 47uF cap, of very solid construction with a record of longevity and exceptional performance, the cost was secondary to those parameters.

So far the end result is far better than expected especially in the positive effect that the rectifier had on the associated tube complement.  The other realization was just how good and exceptional the UFO25 is.  It really deserves the best rectifier that is within ones budget.
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gingerly
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Re: 90db and 6 Ohms do the job?
Reply #13 - 12/20/19 at 22:46:57
 
I love to see a current list of NOS and production rectifiers and input tubes for the Zen amps approved by Steve, but I greatly appreciate all of the input from you great boardmembers nonetheless. Cheesy

If I try anything I will report back on my findings.

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