2. amps-preamps
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New system/room, upgrade amp or preamp first?

Hi all! This is my first post here but I've been an active A'gon'er for many years.

I recently built myself a listening room in the basement. Nothing too exotic in terms of the actual room construction, but I do have 4 OC703 acoustic panels on the wall for front wall reflections and for first reflections. I had a friend build cabinets and I did the crossovers and assembly of Troels Graven's ScanSpeak 3-way Discovery monitors. Just got them done yesterday, they sound very good but need a while to break-in.

I am currently using Jriver set to DoP, out via USB to a Schiit Loki DAC, then on to a Marantz SR-685 5.1 receiver acting as a preamp, and finally on to a B&K AV5000 5.1 separate amp (5 x 105), obviously only using two of those channels. I have the sub out of the Marantz y'd and connecting to two BIC F12's, used only to fill in the lowend. They aren't the most musical subs obviously but they do a fine job to my ears for 45-50Hz and below. They provide a satisfying weight to the sound without dominating the room.

So, I'm pretty OK with the DAC and source. I'm basically using two repurposed home theater components so those are next on my list to upgrade. The room is small, 13 x 10 (speakers are 82" apart, my chair is 82" back from the center point, about 3' from the back wall). I have kicked around an integrated amp but I do prefer separates if I'm being honest. If I have a $1500 budget for ONE component, what should I be looking at first - addressing the AVR-turned-preamp, or the B&K amplifier? The item not chosen for upgrade at this point will be addressed in another 2-3 months.

It's tough to judge a system with such new speakers but so far, the sound is well-dimensioned for both width and depth, though depth is a bit shallow. Voicing is wonderful, thanks in part to the 4" ScanSpeak midrange (wired out of phase with the woofer and tweet).

My listening tastes are varied but primarily I prefer Rock, Metal, and am starting to get more into blues and jazz. I do some orchestral stuff here and there as well as instrumental concerts (violins and piano). Any and all opinions are welcome, I can clarify whatever is necessary. Thanks!
toddrhodes
toddrhodes OP
49 posts
 
Al - thank you so much for that response, it truly is helpful. The plan all along has been to treat the rear wall, I just haven't gotten to it yet but the concern is heard and will be handled post-haste. I have plenty of material left to make another 4" trap - my other thought was to put up a GIK Monster trap (7" thick IIRC) with a diffuser panel on the front of it to treat that space. A friend of mine also turned me onto a bass trap idea using upholstered 12" pipe insulation from OC to sit in the rear corner of the room. I just need to find a source for the insulation.

Regarding the Pre1, I noticed as well it does not have a pre-out, however I found a few references to people using the tape-out to drive the sub inputs. I unfortunately don't know what this terminology means but it is a buffered output that basically is identical to whatever source input is selected on the front panel. The manual suggests I can use both the XLR outs and RCA outs simultaneously as well, so a simple XLR-RCA adapter could fill that need as well.

Again - thank you for your effort and time in digging up that information, I really do appreciate it!

Todd
almarg's avatar
almarg
9,670 posts
 
You're welcome, Todd.

Tape outs are not usually suitable for connection to subs, because they are almost always "ahead" of the volume control in the preamp's signal path. So the volume of the signal sent to the sub would not vary as you vary the setting of the volume control. The alternative of using the sub's volume control and continually having to coordinate its setting with the setting of the preamp's volume control is probably impractical as a long-term solution.

I did notice that the Pre1 provides a pair of jacks labelled "loop," but I'm not sure what they do. And I note that the RCA input of the sub is adjacent to a switch selecting which of two receiver types is providing the signal to that input, a Pro-Logic receiver of a Digital SomethingOrOther (I can't tell what it says) Receiver. I'm wondering if that MIGHT be suggestive of the need to provide the sub's RCA input with an LFE (low frequency effects) type signal, rather than a full-range signal. And, finally, most XLR-to-RCA adapters short the inverted signal on XLR pin 3 to ground (XLR pin 1), and the XLR outputs of some equipment cannot tolerate that without the possibility of misbehavior or even damage. I suspect that modestly priced solid state equipment such as the Pre1 may be particularly likely to have that difficulty. I'll mention, though, that relatively expensive Cardas adapters can be ordered with pin 3 left open, as it should be for actively driven XLR outputs. Or a cable supplier could customize an adapter cable which does the same. (Pin 3 SHOULD be shorted to pin 1, btw, when adapting RCA outputs to XLR inputs).

So while it's possible that line-level connections from the Pre1 to the subs could be successfully implemented, there are a considerable number of uncertainties involved, at least as far as I've been able to determine. But as I indicated earlier I see no problem with speaker-level connections, as long as when you upgrade the amp you avoid those having bridged or balanced outputs.

Regards,
-- Al
toddrhodes OP
49 posts
 
Al, hopefully this pastes well, but the text of the Pre1 manual reads:

XLR Output Jacks for Left and
Right Channels
These outputs go to your power amplifier or
active crossover if it has XLR inputs. They
use the standard Male XLR pinout pattern of:
1 - Gnd
2 - Plus Signal
3 - Minus Signal

• RCA Output Jacks for Left and
Right Channels
These RCA outputs can be used instead of,
or in addition to, the main XLR outputs to your
power amplifier, active crossover, or
sub-woofer

Since neither my amp nor my sub accept balanced ins, it looks like your observation of using the adapters is probably still in play so I would likely just go with the speaker-level option for the subs. The subs operate in a very narrow window and are just there to troll the depths, so to say. I don't expect much if anything out of them above even 50 Hz, roughly.

The loop feature is listed as being useful for sources which have their own internal volume control, the preamp is bypassed entirely. Specifically useful as a HT-Bypass mode of operation.

Thanks Al!
toddrhodes OP
49 posts
 
I will throw this out there, just to get feedback - am I loony for thinking a simple single-ended Y out of the preamp would be doable until I (ideally) find a balanced amp so as to use enable both sets of outputs concurrently? Not dismissing the high-level input option, just curious.
toddrhodes OP
49 posts
 
Seller and I have agreed on $950 plus shipping. Can't wait for it to show up!
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