EM7 - My First Impression

IkeH · « **on:** 17 Sep 2007, 10:20 pm »

I received my "EM7 2.5W" and "2 Input Toggle Pot in a Box" from Roger last Saturday and I wanted to share my first impression with the circle members. I got them to use with my recently acquired used SAP Quartette speakers with 95db efficiency as I felt that the amp that I had (BTW not made by Roger) was not a very good match for the SAPs.

Right out of the box, the sound was intriguing and I was beginning to feel like I got the music back. Hardly broken in but with EM7 in place, the system sounds detailed, musical, and neutral but on a gentler (i.e. organic/natural as opposed to sterile) side (just like RM-5/RM-9 combo I use in my other system). It certainly plays loud enough for my normal listening levels.

I will post follow-up review later but so far I am very happy with my decision

. Kudos to Roger for coming up with such an ingenious innovative product with great "voice" and a very reasonable price.

I am curious to find about what others may feel about EM-7. Would other owners share their views?

Best Regards,
Isaku

Hogg · « **Reply #1 on:** 18 Sep 2007, 02:07 am »

Isaku,

Is this your first pair of SAP loudspeakers? What speakers did your replace with the SAP's? Thanks.

Jim

Whitese · « **Reply #2 on:** 18 Sep 2007, 03:52 am »

I used mine with PAudio 12" coaxes..upper 90's efficiency....I never felt I missed a thing with them....great amps, simply..!

IkeH · « **Reply #3 on:** 18 Sep 2007, 04:24 am »

Hi Jim,

Yes, this is my first pair of SAP loudspeakers. I am replacing Audio Note AN-K Spe. Do you have SAPs as well?

Isaku

Ericus Rex · « **Reply #4 on:** 5 Dec 2007, 06:49 pm »

Now that you've had a few months with this amp, what is your current impression?

IkeH · « **Reply #5 on:** 13 Dec 2007, 02:05 pm »

Hi Ericus,

Thanks for the email. Sorry it took time, I was not ignoring you but I am on a three week business trip to far east and I have not been checking my Audio Circle.

As I am still on the road, I will can not write a longer review one later but in a summary here's what I think so far.

Bottom line: I think EM-7 is an excellent amp with tremendous value. I recommend EM-7 for consideration to anyone who is looking for an amp for their high efficiency speakers.

Perceptively (I can only say this because I do not have any means to measure), the frequency response is very flat and well extended. The tonal balance is neutral but on a "natural" side with slight warmth. It can be quite detailed (depending on your speakers) so one can hear changes in the upstream quite well. For some, this can be a bit of a challenge as it would require appropriately high quality/performance front-end component (i.e. CDP,DAC, Phono amp, cables etc.)

I tried different speaker cables but as Roger said, it does not require "high-end" cables to sound good. I settled for Cardas SE-11 cable.

I also compared it with several different amps (mostly SE DHT amps) I borrowed from various sources. Everytime I tried something else, I was very impressed how good EM-7 was. Of the amps I tried and I thought was better than EM-7 were in the price range of 6 to 11 times that of EM-7 2.5.

If you or anyone who buy EM-7, I strongly recommend changing the fuse to the HiFi Tuning Fuse. Roger does not believe me but it makes such a difference, increased details and extension without making it bright or harsh, night and day in my case (may depend on your speakers).

I will be back in US next week so please feel free to post more question if you have any.

jeffreybehr · « **Reply #6 on:** 13 Dec 2007, 05:37 pm »

I too love the sounds of my EM7 amps. After I built a pair of hi-sensitivity (97 - 100dB) speakers, I bought a pair of new ASL 845-based SET amps but never fell in love with their sounds...sort of sterile and NOT engaging. Since my peak-reading power meter was indicating I was never driving more than about a Watt into the speakers, I bought an EM7-2.5. Immediately I was pleased with the sounds. While not sounding 'thick', the music had warmth and transparency that were engaging, and over the months the music still sounds great. I've since bought another -2.5 and upgraded it to the 5WPC version, a fairly simple project. I now run the -5 on the bass/midrange drivers and the -2.5 on the tweeters and am very pleased with the sounds from the system.

I've replaced the world's cheapest bindingposts Roger uses and will replace some internal parts, but overall I'm VERY pleased.

BTW the Herbie's tubedamping rings are totally unnecessary, that is their addition is inaudible to me, but I had them so I use them. Same for the old VPI bricks.

jman66 · « **Reply #7 on:** 13 Dec 2007, 06:09 pm »

Quote from: jeffreybehr on 13 Dec 2007, 05:37 pm

I've since bought another -2.5 and upgraded it to the 5WCP version, a fairly simple project.
I've replaced the world's cheapest bindingposts Roger uses and will replace some internal parts, but overall I'm VERY pleased.

Jeffreybehr, please do elaborate on the 2.5 to 5.0 upgrade process as well as the other mods you performed. aa

Ericus Rex · « **Reply #8 on:** 13 Dec 2007, 08:11 pm »

Thanks so much for answering! Sounds right up my alley! Now I just have to get some more efficient speakers and wait for some money to fall into my lap....

I currently own Roger's RM-5 and RM-9 and am amazed at them each time I sit down for a listen. The RM-5 is simple when you look at its guts but the sound is so satisfying. My curiosity about this little amp is piqued.

jeffreybehr · « **Reply #9 on:** 14 Dec 2007, 07:38 am »

Ericus: "The RM-5 is simple when you look at its guts but the sound is so satisfying."

Sounds just like an EM7 amp. It's a very simple 2-stage amp. The 2.5WPC version uses what the industry calls cathode bias and what I call passive bias, 'passive' because the tube biases itself just like a preamp triode does. Each output transformer uses 2 identical secondary windings which are placed in parallel or series (using jumpers if you have the 2-pairs-of-terminals-per-channel version) for low- or high-impedance speakers. The 13EM7 tubes I've had, and that's been probably over 50*, have been universally quiet and reliable but, apparently because the circuit uses NO NFB, have differing gains in-circuit and need to be matched for gain. Roger sells gain-matched tubes at reasonable prices.

I have replaced the 2 pairs of output bindingposts with one pair of the larger AudioNote silver-plated ones (#67306, here... http://www.partsconnexion.com/catalog/connectors.html ); if I did it again, I'd use the smaller AudioNote silvers OR some Cardas all-copper versions from Sonic Craft. I've replaced the 0.047/400VDC coupling caps with Cardas Golden Ratios, my 2nd-favorite cap, and when I do some powersupply work, probably I'll replace them with SoniCap Platinums. I've hardwired one pair of IC cables and will do the same for the other amp, as I believe in eliminating mechanical and solder joints when possible and practicable.

The 5WPC version uses a higher-Voltage and -current power transformer, changes a few resistor and capacitors, and uses an active bias system (that the industry calls 'fixed bias' even tho it's not fixed). Since Roger hasn't released the upgrade kit, probably I shouldn't say much more about it except that if you can solder, most-probably you can install this yourself.

I've not yet seen or heard the -12M, but that should be another great value, being a 12-Watt Single-Ended-Triode monoamp** for some-$900. It uses one small-triode section for gain, the other as a cathode follower, and the 2 large-triode sections in parallel to deliver its 12 Watts.

* My wife calls me Mr. Excess for good reason.

** I HATE the term 'monoblock'. Every time I read it, I wonder if that person uses the term 'stereoblock' for 2-channel amps.

jman66 · « **Reply #10 on:** 14 Dec 2007, 10:11 am »

thanks for the details!
BTW, I think the upgrade kit is official, it's just not posted on the MR website:
http://www.audiocircle.com/index.php?topic=48191.msg434111#msg434111

jeffreybehr · « **Reply #11 on:** 14 Dec 2007, 06:07 pm »

That page is blank for me.

lcrim · « **Reply #12 on:** 14 Dec 2007, 06:23 pm »

I've had my EM7 amp for about a year now. When I first received it, I didn't have appropriate speakers for it yet. I was waiting on a pair of Omega Compact Hemps, then on the stands but all was together by January. I have a fairly high gain preamp, the modded Eastern Electric Minimax @ 18 dB and it works well with the 96 dB Compact Hemp speakers. I swapped the spades on the AntiCable speaker cables for banana plugs and the binding posts caused me no further trouble. When I purchased my unit only the 2.5 watt unit was available and I paid a slight premium over present prices but overall I still consider it a good value. I also have a Decware Select SET in my bedroom system, so I have two of the most atypical sounding SET amps in creation.
I find the EM7 a very transparent sounding amp, I don't think of it as tubey sounding at all. The EE preamp, especially with all the tube rolling I've done, is more on the warmer and romantic side, and the whole system reacts very noticeably to upstream changes. The EM7 is a very quiet amp, I have no idea what the S/N ratio is but it must be quite high. Roger has always been first rate to deal with and its been educational. Tube life has been fantastic. This system is pretty highly resolving and as I listen to a lot of vinyl, the stuff going on in the background at recording sessions has become very apparent.
I've sorta reached a point where all the components fit together and the sound is quite decent. There were some threads a short time ago about using the Hemp drivers with higher power amps but I just don't have the desire to change right now. At the new lower price this unit is a steal.

skite30 · « **Reply #13 on:** 14 Dec 2007, 08:22 pm »

I have the em7 2.5 amp and I am curious about the differences between it and the 5 watt version.

jman66 · « **Reply #14 on:** 14 Dec 2007, 09:10 pm »

Quote from: jeffreybehr on 14 Dec 2007, 06:07 pm

That page is blank for me.

Oh well, please check out the topic EM7 Upgradeability in the Music Reference Circle...

jeffreybehr · « **Reply #15 on:** 15 Dec 2007, 04:30 am »

Quote from: skite30 on 14 Dec 2007, 08:22 pm

I have the em7 2.5 amp and I am curious about the differences between it and the 5 watt version.

OTHER than what I discussed above?

skite30 · « **Reply #16 on:** 15 Dec 2007, 04:55 am »

I saw that you have both models and was curious if there was any difference in the sound or if there were any differences that you had noticed. I didn't see where you discussed this and so was curious about it. If I missed the or asked a stupid question please feel free to correct me.

jeffreybehr · « **Reply #17 on:** 15 Dec 2007, 07:06 am »

Skite30: "If I missed th(at) or asked a stupid question please feel free to correct me."

No correction necessary; I just didn't understand what you were asking about. I must state again that I'm no Golden-Eared Audiofile, and sometimes compared with what some of my friends hear, I'm much more a tin-eared audiofool...BUT...I do hear cumulative differences in my system even if that takes weeks. The sounds of my system have improved significantly over the last few years, and I believe the EM7 amps have had something to do with that.

That said, I hear no differences between the 2 amps, and frankly I wouldn't expect to since the vast majority of the circuitry (including all the powersupply caps and resistors) is identical. I think power requirements would be my only consideration between the 2 amps. I felt I wanted more power for the 2 chunks of the system carrying the vast majority of the music.

BTW I rechecked the bias settings in the -5 tonite and found NO change after about 2 weeks of use. I'm loving these amps more and more. aa

Jampot · « **Reply #18 on:** 15 Dec 2007, 09:52 am »

Quote

I now run the -5 on the bass/midrange drivers and the -2.5 on the tweeters and am very pleased with the sounds from the system.

jeffreybehr,

Do you use active crossovers or filtering before the E7s please and may we have some detail?

Jim

jeffreybehr · « **Reply #19 on:** 15 Dec 2007, 04:48 pm »

Jim, I've written so much about my system, some think it's bragging, but here goes.

The L/R speakers are open-baffle line-arrays (OBLAs) that I built around the Sonic Craft 6-1/2" bass/MR drivers.

The 4-Ohm JG65s are wired series/parallel for 8 Ohms and their sensitivity in the midband is 97 - 100dB. These drivers were NOT designed to be tweeters and sound a bit hard in the treble octaves, as does about every nontweeter around, so I use 8 of the inexpensive Dayton magnetic-planar tweeters; these 8-Ohm drivers are wired s/p for 16 Ohms.

The bass is handled VERY well by a pair of (now unobtanium) Sonic Craft SCC300 12" woofers, wired in parallel for 4 Ohms, and driven by 2 channels of an Outlaw 770 multichannel amp.

All crossovers and equalization are done by a dbx-brand DriveRackPA digital speaker-management system... http://www.dbxpro.com/PA/ . For the bass's low-pass filter I use a 4th-order Linkwitz-Riley slope at 45Hz. High-pass into the JG65s is 30Hz, 1st order; the treble is removed with another 4th-order L-R slope at 2kHz. The hi-pass to the tweeters is another 4th-order L-R at 2KHz. Level controls for all 3 sections make balancing the 3 chunks easy. (BTW, this DriveRackPA is stereo and NOT dual-mono.)

Since the DriveRack is professional equipment, it uses XLR connectors, and I added those connectors to the 6 ends of my AQ IC cable myself. Of course the rest of the system is single-ended.

You didn't ask, but the centerchannel speaker is built around an Eminent Technology 12 and adds a 10" woofer, all dipole, of course. This woofer, not surprisingly, is actively filtered, this time by an old Dahlquist LP-1. Two more channels of the Outlaw drive the 2 chnks of this CC.

Here's what all this equipment looks like.

The system sounds very big and spacious with a huge soundstage. I like my music warmly balanced with plenty of bass and a bit dark on top. Image focus is also excellent in spite of having a huge TV in the center.

I think this huge soundstage and excellent centerfocus is assisted by the system living about 7 feet off the front wall. The room is 19' deep, 21' wide, 6.5 - 12' high, and has few parallel surfaces.

If you have more questions, ask...as you can see, I love to write about my big, ugly multichannel system. BTW I've designed and am accumulating material for the 4th-and-final versions of the L/R speakers; they'll be as gorgeous as these are ugly...and a little shallower.