2. amps-preamps
  3. 1158525202

Need balanced pre with HT bypass/remote/

I recently bought some great used ATC SCM 150ASL active loudspeakers on this site. They are wonderful replacements for my VMPS RM/X's, but they have put my great-sounding Modwright SWL 9.0 SE into a tizzy. Due to the SWL being single-ended there are numerous ground and buzz/hum issues that have arisen because of rca-to-XLR, etc.. Some grounding straps have helped quiet it up in 2 channel but the HT bypass continues to have noise now. Jensen isolators may help, too, but it's getting crazy. Anyway, I'm also susceptible to phase inversion and I use to be able to swap speaker leads when i thought things would sound better that way; I can no longer do that with the ATC's (no speaker leads). The Modwright inverts phase, period.

So, I am in the market for not simply a replacement for the Modwright, but I want a significant upgrade if I'm gonna do this. The table stakes include true balanced outs, remote control, HT bypass (or unity gain-fixed gain), and an invert phase switch if possible. The following are a list of contenders based on my internet surfing over the past couple of days. Any opinions on these would be very helfpul. I've read quite a few user opinions, and most list the Ref 3 as tops, but a couple folks claim they like the new LS26 better, and it's almost half the price (neither are likely available used). The other top contenders would be possiblly available used or new:
* ARC Ref 3
* ARC LS26
* ARC Ref 2 Mk 2
* BAT VK-51SE
* Aesthetix Calypso
* Pass Labs x0.2 (no invert function)

My 2 channel equipment is mainly:
* a wonderful sounding Modwright tubed-modded Denon 3910 for redbook and hirez
* a SOTA Saphire tt into a Dynavector P-75 stage (will soon upgrade SOTA, and possibly Dyna down the line)
* ATC SCM150ASl active speakers with triamps internal

Note: Although I also have a 5.1 and 7.1 setup in this room, driven by the modded 3910 hirez surround and DVD into a Denon 4806 acting as a surround pre (soon to Anthem D2 for balanced needs into ATC surrounds, as well) it's mainly my 2 channel sound I'm focused on now.

Feel free to add a pre of your choice, but it needs to include the basics. Thx much,
Ted
tedmbrady
roberts4152
16 posts
 
Sorry to be late to your question, but I have the same hum issue. I recently bought ATC active 20's and have a single-ended Art Audio DM-VPS tube preamp.

In addition to balanced operation, check the output impedance of any preamps you consider. I don't pretend to understand the engineering, but I do know that the active ATCs generally have very low input impedance (@10k ohms). Therefore, a preamp with low output impedance would be the best match, all other things being equal. Otherwise, you may get rolled off bass. Among the tube preamps you listed, I think the Calypso is the best choice judging by Stereophile impedance measurements, plus the reviews are all very positive on the sonics and musicality. If you check the web page, ARC recommends that virtually all its tube preamps should be matched with power amps having input impedance of at least 20k ohms, so they probably aren't as good a match for your ATCs. I'm pretty sure that BAT preamps also are better matched with higher input impedance amps (even BATs with the six pack, apparently).

Other tube preamps you might consider for balanced operation with low output impedance include Blue Circle as suggested above (but watch out for phase inversion), Sonic Frontiers (supposedly great, but lots of tubes to deal with) and possibly Atma-Sphere.

I am probably going to sell my Art Audio, even though it's terrific, and switch to solid state for now. It's an easier system match and less work than a tube preamp. Hopefully, the sound won't be too edgy.

Good luck.
tedmbrady OP
208 posts
 
Thanks Roberts4152.

Update: I'm currently trying a Bryston SP2, and although it's day job is a pre/pro, the analog 2 channel bypass portion of it is the well-regarded BP26 pre. Although I've lost a little bit of air from the Modwright, it's sound is much much quieter (balanced) and the soundstage is much wider. Tradeoffs, tradeoffs, tradeoffs. My cables for this setup are the measly Mogami/Neutrik balanced cables that I've burnt in for about 200 hrs and so far it sounds very good. I don't think this will be my final setup (I miss the air around instruments) but so far haven't figured out how to match my Modwright to the ATC's without all the hum. Even tried a set of ground lift adapters on the XLR's and while at first they were fine, they began humming later in the session!!?

A second huge variable is that I take delivery of the new Ridge Street Audio Sason speakers next weekend. Long story but the ATC's were simply a great find while I waited for the Sasons to be built. Steve @ Ridge had offered a 45 day trial as he begins to introduce these speakers to the larger market, and I took him up on it. He is driving over from Indiana next Saturday and we'll set em up and compare to ATC's. The comparison is whacked, of course, cuz ATC's are active and use their own amps. Everything past the preamp changes. But it's all about the system, so I'll be using the Modwright, then maybe the SP2, to drive a Krell KSA-100 for now. Will update l8r.

Back to the preamp search, two new and completely pardoxical preamps joined my list. The MBL 5011, and the Bent TAP TVC preamp. One uses incredibly sophisticated (and expensive) topology, the other is a passive pre with active switching (including HT bypass, invert polarity, etc).
gordan's avatar
gordan
2 posts
 
i have another model of active ATCs (20A) and it is quite a pain in the ass to get a good preamp sorted. the speakers are just too picky, and from everything i've heard the standouts were a) electrocompaniet EC4.7, a later version with a gain adjuster on the back, with 0dB setting - for great musicality, flow and involvement but with unfortunately dark upper mids and rolled off highs b) pass labs X2.5 that produces very good sense of natural atmosphere and realism.
don't even think to bring cary near ATCs, they have too much impedance and too much gain for a good match.
the same goes for krell 250p, which is a good electrical match but otherwise it is too sterile and bright.
anyone tried ayre K-5xe?
kwtoxman
25 posts
 
Gordan, it is my understanding that a Cary SLP 2002 preamp has a low output impedance. Unconfirmed it has been mentioned at 440 ohms single ended. I'll try to confirm.

The ATC SCM150ASl input impedance is 10K ohm. This exceeds the general rule of thumb of a min 1:10 ratio that many people on audiogon have previously discussed.

As for gain, one can use lower gain 6FQ7/6CG7 tubes or send the volume board into Cary for a simple mod to lower the gain.

As for the Cary 2002 now that I have listened to it extensively for a couple months I find it amazing. It really opens up the soundstage on my system so so much, and has a sonic signature in between tubey preamps (Eg, early CJ's) and notable neutral tube preamps (Calypso, SF3, etc). It has lots of air and beautiful mids and highs. Tube rolling has shown me I can further tweak the sound quality too. It blew away a $3K SS preamp I tried in my system.

kw..........
More to discover