Forums - How do you perceive SE34I.3 "hum" NEARFI

Rizlaw

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How do you perceive SE34I.3 "hum" NEARFI
03/10/13 at 17:13:58

My new Rachael hums through my Omega Super 3E speakers (94db efficient 8ohm speakers). The amp in centered on my desk, 2 feet from my chest. The speakers are at the desk's corners and approximately 3 feet from my ears. Steve and I have ruled out all other hum inducing factors. The hum is clearly being caused by the amp. The amp has been back to Steve for repairs but that's not what this post is about. I'm also not talking about the mechanical hum from the amp which is now very low and inaudible when music is playing at any level.

Question 1:

What I'd like to find out from other Rachael owners, who may be listening nearfield to similarly efficient speakers, is what they hear or don't hear concerning amp hum from their speakers.

Steve tells me that with a 94db speaker I should near no hum from the speakers unless I put my ear right up to the speaker cone. In my case, that's not true and it's very distracting during low level music. I also can not use the amp's line outs to my powered subwoofer because it makes the hum worse.

Question 2:

Also, the "hum/noise" rating of the different Decware amps are inconsistent in description:

Mono Torii = -90db
Torii III = -90db
Mini Torii = Too low to hear
SE34I.3 = less than 1.5mv
Super Zen = less than 1.5mv

What does "less than 1.5mv" mean and why isn't it spec'd to a -xx db number like the two top amps; or, given a word description like the Mini Torii?

I've been trying to reach Steve since March 6th about this but I can't. I just found out this morning from a forum post by "Longbowbbs" that he's at Axponia from March 8-10, but his answering machine doesn't tell you that he's away and the shop is closed.

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opnlybafld Ex Member	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #1 - 03/10/13 at 18:39:55 If you have the amp hooked to the speakers with no source plugged in you still have hum?
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Rizlaw

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #2 - 03/10/13 at 19:18:34

Openlybafld,

The answer is YES, I did mention that in the original post where I wrote: Quote:

Steve and I have ruled out all other hum inducing factors.

This is not a source, tube or ground induced hum. It's a hum, apparently, inherent in the amp. It is made obvious when you are using a single driver, high efficiency, crossover-less speaker (Omega Super 3E). If I connect the Rachael to my MMGs, which have crossovers and are significantly less efficient, the hum is so low as to be virtually inaudible. However, I didn't buy this amp for MMGs. Of course, this doesn't change the hum I hear in my subwoofer through the Rachael's line outputs.

What I'm trying to determine, is whether this hum is, for example, greater in the SE34I.3 than any of the Torii amps and why. Perhaps I'm wrong about this, but it seems that such a simple SET circuit should be very quiet compared to more complex circuits like the Toriis.

Nothing I read about the Rachael on the website, in the manual or discussed with Steve before purchase, suggested I would experience this type of hum issue in my desktop nearfield setup. For me, the hum significantly detracts from my use and enjoyment of the amp. It's not what I expected. Nevertheless, since getting the amp back from Steve, apart from a new mechanical issue that has surfaced with the input selector switch, I love the way it looks and sounds.

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opnlybafld

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #3 - 03/10/13 at 19:36:32

The reason I asked is because you said hooking up a powered sub with ICs made it worse, which would indicate a ground issue.

Are your MMG's in another room?
I had a ss class A amp that hummed in a spare bedroom system, but when connected in my larger main room it was not noticeable.
Apparently it was a combination of something amiss in the electrical circuit and a 60hz room resonance in the smaller room.

Would it be possible to take your system over to a friend's house?

Lin
PS I have a pair of Omega Super 3i's with the new drivers. Amazing!

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Rizlaw

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #4 - 03/10/13 at 20:15:37

It's positively not a ground issue and the sub only made it worse in the sense that it added its own hum to that of the Omegas; it didn't make the Omegas hum more. It's simply a question of the Rachael passing the hum via the speaker connections and the line out connections. As Steve explained it to me, the line outs are connected to the output transformer just like the speaker outputs are, so the same sound (hum included) is passed to both the main speakers and any other component connected to the "line outputs".

The Omegas have been connected to my recently overhauled 50+ year old tube Fisher X202B (got it as a gift when I was a wee lad and have kept it ever since) and to a Classe CAP-2100 (100w SS) on the same dedicated 20 amp electrical circuits (4 separate and dedicated 20 amp AC lines specially installed for my audio system when I was into this hobby big time). Same results in all cases. Both the Fisher and Classe were/are dead quiet (no hums, buzzes, etc.) with the Omegas. As for going to a friends house, that, in my circumstances, is out of the question.

And yes, the new Omegas are exceedingly good and Louis is a super fantastic fellow to deal with IMO.

P.S. I forgot, the MMGs are in the same room as the Omega, behind me in the middle of the room so to speak. I use them for casual listening to conserve tube hours on the Rachael and Fisher. Actually, as watt sucking as they are, they are driven amazingly well by the Rachael (and with little or no hum). I didn't notice any clipping on the Rachael's meters on the few Diana Krall tracks I played while troubleshooting the hum issue.

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opnlybafld Ex Member	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #5 - 03/10/13 at 20:51:15 I assume Steve had no problems with hum when he had it?
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Rizlaw

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Posts: 117

Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #6 - 03/10/13 at 21:31:13

It's dangerous to assume. Have you ever heard the saying:
Quote:

When you ass-u-me it makes an "ass" out of "U" and "me".

Not that either one of us is an ass. :) To answer your question. He did find hum as I described when he duplicated my setup in his shop (albeit with different speakers). He was able to reduced the hum by about half by isolating the transformer with washers and re-routing some wiring. He also said the hum was "within normal limits". I don't understand what that means since I have no high and low limits to go by. That's why I'm asking other owners about their experince with hum or lack thereof in the nearfield with high efficiency speakers.

Remember, according to Steve, on a 94db speaker, there should be no audible hum at 3 feet; only when your ear is up against the speaker should you hear any hum/noise. By that test, my SE34I.3 is not within normal limits while my Fisher X202B and Classe CAP2100 are.

I don't hear the reduction by half on the Omega speakers in my 3 foot, desktop, nearfield setup. The amp chassis itself sounds a less hummy than before.

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busterfree

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #7 - 03/10/13 at 22:10:07

I am listening near field with the Decware Trapeziums (89 db). I just took out the MT to try the Rachael, and my Rachael is definitely quieter than the MT. My Super Zen is equally as quiet as the Rachael.

I often think about sending the MT back for a check up and upgrade, but I keep on listening to it.

I am confident that you will get the issue resolved.

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busterfree Seasoned Member Posts: 431	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #8 - 03/10/13 at 22:13:20 How do like the Omegas? I have thought about trying the Omega 3T Desktop against the Trapeziums, but I do not "need" another set of speakers
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Rizlaw

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Posts: 117

Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #9 - 03/11/13 at 00:50:16

Busterfree,

So your Rachael is quieter than your Mini Torii, and the Mini Torii's hum/noise rating is "Too low to hear". That reinforces my opinion that my Rachael is not as quiet as she should be and that's why I still hear hum. On the other hand, 89db Trapeziums are 5db less efficient than Omega Super 3Es, nevertheless you still perceive the MT to be noiser than the Rachael on your speakers.

As for how I like my Omega Super 3Es. I think they are exceptionally good. At first I didn't care for them, but now with over 100 hours, I've made a 180 degree opinion turn. They are very fast (almost electrostatic fast). On a smaller scale, they remind me alot of my old Acoustat, Beveridge and full Levinson HQD (Two 24" Hartley Subs, four Quads in custom stands, and two Decca Ribbon Super Tweeters) systems. On the plus side for the Omegas, they won't self-destruct every week (if you've owned these electrostats you know what I mean). The Omegas are articulate, smooth from bottom to top and have an exceptionally good 3D soundstage for a small point source monitor. I imagine they would sound even better in a more "non nearfield" setup. More room to sonically blossom. With the Rachael, the bottom end is surprising powerful down to 50Hz and maybe a little lower. Not so when connected with my more powerful Classe SS amp or even my Fisher X202B. The top end is smooth and sweet as far as I can hear (to about 15k for my old ears). The crossover-less single full range speaker concept also imparts a subtle, but noticable continuity/body to instruments (if that makes any sense to you). Instruments that span a wide frequency range, and would normally use 2 or 3 speakers to reproduce their sound, just sound more fleshed out and whole. Low level listening, one of the main reasons I selected this speaker and amp combination, is wonderful. A lot of speakers/amp combination just can't play well at low levels. Details and clarity go missing. This, I believe, has much to do with Steve's "first watt" motto. "If it sucks why continue?" Well the Rachael/Omega combo don't suck! They shine. It's the first time I've owned this type of single full range cone speaker and it has made a positive impression on me. Finally, the build quality is really something to behold, especially Level 3 finishes like Bubinga (an African rosewood)veneer. I'm fairly certain you'd have to pay 2-3 times as much to get this level of craftsmanship from one of the big name speaker companies.

Sorry for a rambling, incoherent, mini-review. They are two great products. I just wish my Rachael would tone down on the humming. Cry

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Fireblade Seasoned Member Knowledge comes, but wisdom lingers. A.L.Tennyson Posts: 1046	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #10 - 03/11/13 at 01:14:33 FWIW, my Mini does not make any noises that I can hear, even with my ears significantly closer to the speakers than the std reference of 3 ft. My speakers are DM945's, at 94 dB @ 4 Ohms. Therefore, in my case, the Mini's noise is indeed 'too low to hear.'
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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 23464	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #11 - 03/11/13 at 01:18:11 Are you certain the hum is not from elsewhere?
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Rizlaw

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Posts: 117

Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #12 - 03/11/13 at 01:33:50

Lon,

Yes, unless there's a ventriloquist in the room with me. Grin

As I said before, Steve heard it too and claims to have reduced it by half with a few tweaks noted in my posts above. The hum is coming from the amp into the speakers and it has nothing to do with sources, tubes or grounding. I'm not ruling out poltergeists.

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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 23464	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #13 - 03/11/13 at 01:35:37 OK, I didn't read the whole thread. Every time that I've had a hum like this. . . it was a tube. Every time.
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Rizlaw

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Posts: 117

Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #14 - 03/11/13 at 01:45:46

You'd think so. But the first thing I did was swap out all the tubes. Steve even sent me one of his own primo 5u4gB rectifiers and a new set of 6np1-ev's. No difference. Same for the power tubes (EL34 and Treasures). Even put Herbies Halo III Titanium dampers on every tube along with silicone ring dampers Steve sent with the 6np1-evs. Also tried 6922s and NOS Philips 5R4GYS

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Lon Seasoned Member "Love without guts is worthless!" Philip K. Dick Posts: 23464	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #15 - 03/11/13 at 01:51:36 Well. . .one would think not then, though the way tubes are it could still be a tube. I hope you can resolve it!
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busterfree

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #16 - 03/11/13 at 02:04:12

Posted by: Fireblade Posted on: Today at 17:14:33
FWIW, my Mini does not make any noises that I can hear, even with my ears significantly closer to the speakers than the std reference of 3 ft. My speakers are DM945's, at 94 dB @ 4 Ohms.

Therefore, in my case, the Mini's noise is indeed 'too low to hear.'

I agree Fireblade. This is what makes me think I have a problem, but it is not a big enough problem to ship my amp back. I am still on the fence about upgrading it. That would be a good time to check it out.

I using the Rachael right now with Trapeziums and enjoying it. ;D

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Fireblade Seasoned Member Knowledge comes, but wisdom lingers. A.L.Tennyson Posts: 1046	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #17 - 03/11/13 at 13:24:18 IMHO, If you're planning on eventually replacing those speakers with higher sensitive ones, getting rid of that moderate hum is essential.
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Rizlaw

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #18 - 03/11/13 at 15:26:28

Fireblade & Busterfree,

Busterfree, I completely agree with Firebird on getting rid of hum first in your MT before considering higher sensitivity speakers down the road; particularly if you're considering speakers like Omega's cross-over-less fast full range single driver types which don't filter out anything coming into them. You need a pure, quiet and clean signal. The nearfield hum problem I'm having with my Rachael is evidence of that.

It's been so long since I owned Klipshorns (back during the Quadraphonic craze), that I forgot just how revealing truly high efficiency speakers can be; irritating, too, with the wrong electronics.

I think you already know this. Wink

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78 archivist

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #19 - 03/11/13 at 18:01:01

Hi Fireblade,

I've been using Rachel bridged to mono on a full range 15" Audio Nirvana speaker. I definitely get audible hum at three feet, and it would be intolerable if I were using it nearfield. Luckily I'm usually anywhere from six feet and beyond where it doesn't bother me. Similar to your Fisher, my 60 year old H.H. Scott 299a was dead quiet up to one foot of my old Klipsch Heresy's.

78 Arch

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Rizlaw Seasoned Member Posts: 117	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #20 - 03/11/13 at 23:36:57 I heard from Steve this afternoon. He says that the "less than 1.5mv" noise/hum rating for SE34I.3 and Zen amps is equal to about -72db for those who may be interested.
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Palomino Seasoned Member Posts: 2474	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #21 - 03/15/13 at 20:07:48 I have a new Rachael and I get slight hum on 89db 8 ohm drivers, but need to be right next to the driver to hear it. I don't think I would hear it nearfield. Last night I hooked up 89db 4 ohm speakers and noticed no hum what-so-ever. Not sure why hum on 8 ohm and no hum on 4 ohm.
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Rizlaw

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Posts: 117

Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #22 - 03/15/13 at 23:27:44

Palomino, when you say:

Quote:

Not sure why hum on 8 ohm and no hum on 4 ohm.

Here's my take on a possible answer. The "Rachael" has a noise/hum rating of "<1.5mv" or about -72db according to Steve. The amp is designed to be most efficient with 8 ohm speakers from what I've read. From what Steve has told me, the "slight" hum you hear with your ear right next to the speaker driver is normal. It's what you should hear, at worst, so to speak, with speakers in the 94 or less db range. At best, you would hear nothing or perhaps a slight soft hiss. In all cases, from 3 or more feet away, you should hear virtually nothing in terms of noise/hum unless you have 103db, or greater, sensitivity speakers (again, according to what I've been told by Steve). This all assumes, that the hum is not being caused by other factors like: poor grounding, bad tubes, a problem within the amp like a bad solder joint or defective part. There could be a few other factors I'm not knowledgeable enough about to list.

From my own experience, two way speakers with crossovers are going to produce the inherent hum of the amp differently than high efficiency, single full range crossover-less speakers.

In the later speaker design (high efficiency, single full range crossover-less), given an accurate driver, there is nothing to reduce or modify the noise/hum coming from the amp before it gets to the speaker. In the former speaker design (2 way crossover) the crossover can soak up a good deal of the amp's noise (hum) making it very low to inaudible.

For example, on my 4 ohm MMG's, the Rachael produces virtually no hum (nearfield). However, the MMGs are known to be highly inefficient (about 83db) speakers which require a great deal of power. On the other hand, my vintage Allison Six's ( 86db, 2 way crossover @ 4 ohms) produce a hum similar to the hum I hear from my new Omega Super 3E (94db @ 8 ohms). On my Thiel 7.2 speakers which have a complex crossover network and are 86db 4ohm speakers, you can only hear a faint buzz from the Rachael with you ear right up to the woofer cone. So four different speakers with four different audible hum results.

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hifitubes Seasoned Member Posts: 296	Re: How do you perceive SE34I.3 "hum" NEARFI Reply #23 - 03/26/13 at 12:27:15 I'm running USB > Zodiac Gold > Rachel. DEAD QUIET. Barely audible whisper that you can just tell the system is on, and not off. 97db/w Hoyt Bedford.
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Rizlaw

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Re: How do you perceive SE34I.3 "hum" NEARFI
Reply #24 - 03/26/13 at 16:30:10

hifitubes,

I appreciate the info. Steve and I are at a loss to explain why my "Rachael" produced audible (annoying) hum through my speakers, but not through his. As a matter of fact, on the second go round, Steve measured the noise in my modified "Rachael" to be lower than a Torii III.

I've gotta say that in 50+ years of High End audio, I've never met an audio manufacturer and person more concerned and dedicated to resolving legitimate customer problems than Steve.

I'm now waiting on a new Taboo III. I'm praying to the "Tube Gods" this will end my hum issues and allows me to concentrate on my next Decware purchase: perhaps the phone stage.

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