almarg 2)The miniDSP 2x4 has a very low input impedance of 6K.
I'm going through the same impedance woes, with yet to arrive a Minidsp 2 x 4 HD to do some bass (<150hz) only experiments with, it's 10kohm input, a little higher than the 2x4. I sent a email off to tech dept of mini dsp to see if the analogue inputs are a fet based input, if so then "maybe" the 10kohm smd load resistors can be swapped out for >50kohm? This should be an easy way out if the source has high output impedance. Cheers George |
Stringreen, I have been told the same by other people as well. I am too far down the road now. Maybe in the future I'll reconfigure. I have been fine tuning it and it sounds pretty good right now. Still needs more impact but I have some options. |
Have not heard that exact amp but have heard Crown Class D amps at the gym and I own other Class D amps.
One thing is all Class D amps have very high damping factor including that one and the ones I use. Good ones do bass in particular extremely well, better than most anything else. Hence their popularity for use in powered subwoofers. When I first heard mine, I thought bass was gone also in comparison but turned out to just be more dimensional, articulate and clean in stark comparison to prior which was more towards stereotypical "one note" fatter bass which many may be used to and may seem like more or better but is not IMHO.
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Stringreen what Class D amps have you heard and what are you comparing them to?
thanks.
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That power supply is pretty hefty. The specs are 4.16 amp if you are doing the +12V DC model. This is fine if you are powering a several items like the miniDSP (which is very low current draw and uses basic op amps). It's fine even for adding Antimode 2.0 into the mix. This power supply has a lot of capacitance. The capicators they use could be better, but the price is right for what they give you. If you need a split power supply (i.e. +15V / -15V), then you'll need a different power supply. |
Class D's are fine for subs, but even the best ones are pretty poor in the upper mids and highs. Also, It is FAR better to use a good stereo amp than to biamp with dissimilar amps. Biwireing is good, biamping is not.
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Aux,
BTW that supply looks nice. I would like to power 2-3 pieces of equipment with that. All low current draw. Do you think I would have to buy 3 or add connectors to supply multiple devices?
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Aux,
right now I have a mindsp in the circuit. Since I am in an audio club I am fortunate to have loaner equipment available. So today someone lent me a Dahlquist LP-1. I know vintage Lol! It has a higher input impedance so I want to what the effect of that is.
On a related note,at this meeting the host was using GR Research dual 12 OB woofers with the A370PEQ amps. It sounded very good. I like OB stuff. However it is around 3K for that alone. Ultimately I would like to build a pair next summer. Hopefully I can save some money DIY. |
Which crossover are you using? minDSP or Antimode 2.0? The Antimode is probably a much better unit then the miniDSP (as it’s 6 times as expensive, lol.), but keep in mind it is still a DSP (which means A/D -> DSP crossover -> D/A). If you like the way it sounds, I’m sure it will benefit strongly from a hefty 12V linear power supply such as this: http://www.ebay.com/itm/121970182193?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT Or many others that are available. It's hard to say if this will be better than a Bryston crossover, but I know you're trying less expensive options first. |
Caps installed. deeper low end response. PLayiing with Xo for best Xo point.
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OK so today I got some improvements. I got the good caps from Modwright and installed in my KAW 100SE. That sings sweet now. I had the woofer amp plugged into a power conditioner, I plugged them directly into the wall. I worked with the Xo points/slopes and now it's beginning to sound much better. Not perfect but it has come a long way. Now i still have some caps Dan sent me to install on the LS100 that he says will improve the bass response. I'll do that tomorrow.
Stay tuned :) |
I've never had great let alone decent results bi-amping my speakers even using 4 channels out of 5 on my audio refinement multi 5 amp. I do bi wire all on the speaker end with Tekton 6.5t monitors in the past and currently ProAc Studio 148 mini towers. |
Bingo :)
BTW I see a parasound 2125 for $340. 150wpc. a little bit newer that the hca series and still cheap. 35amp and 33k input imp.
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oh, I got it. You have to be a member and logged into the forum before they will show you the listings in "The Emporium" section. |
Ok, good luck. the first 10 posts in that "The Emporium" section are just static pinned threads for rules/faq/etc. You have to scroll down further to get to the actual items for sale. |
I do that but I dont get an area where stuff is being sold. I'll try on another computer. |
Emporium: - Go to Emotiva’s main website http://emotiva.com/ - Click on "Community" in the menu bar at the top - Scroll all the way almost to the end. There should be a forum call "The Emporium" - Scroll down. The topic/listing should still be on the first page and titled "XPA-100 GEN 2 PAIR BNIB". |
Lol Aux I have to spend a bit more to get something newer and not so "vintage" ha ha. The parasound is so old that the electrolytic caps are leaking. |
aux, I tried to find the stuff for sale in the emporium but I dont see where the stuff is for sale.
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Wow, I thought we were looking at cheaper alternatives, lol. I would avoid the Adcom. I had an Adcom GFA-545. It was on the warm/slow side and sounded dirty/smeared when compared to other better amps. The Emotiva XPA-2 is definitely a contender if you are considering this and definitely better than the XPA-100 monoblocks. Very strong amp. I do not have any direct experience with the Wyred 4 Sound (or any other ICE based Class D amp). Eric Squires likes the w4s, but I cannot give you an opinion on how well it will control the woofer. It does have a radical 100k ohms input impedance! |
The Parasound amps are the only stereo audiophile amps I have seen that have a volume/level control. The older THX certified multi-channel amps all had level controls, and pro audio amps have level controls. There's a Parasound A23 on Audiogon for $699, but honestly I think you'll get better control with the two XPA-100 monoblocks (and cheaper). You could always wire an Alps potentiometer directly into your RCA interconnect for the woofer amp. It looks like there are cheap passive volume preamp for like $50-60 available. I haven't used ART stuff, but I kind of view them as a lower end item, like Behringer. Not bad, per say, but definitely inexpensive, with Crown and QSC being better quality (but more expensive also). |
W4S St500? Adcom GFA555? emotiva xpa-2? |
The input impedance of the ART (Applied Research and Technology) SLA-2 is 22K unbalanced and 44K balanced, the latter probably corresponding to 22K per leg. Too low to be optimal, or even close to being optimal, when driven in parallel with your Modwright amp by the LS100.
Also, the fact that its rated maximum power into 4 ohms is only 40% higher than its rating into 8 ohms says nothing positive about the robustness of its design.
I’ve used some other ART products for non-audiophile purposes, and in those non-critical applications I found them to be an excellent value. But I suspect that in a high quality audiophile-oriented system they would likely be disappointing, even if no impedance or other technical issues were present.
Regards,
-- Al
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agreed. usually you don't want to put any resistors in line with the woofer, right?. BTW, the speakers are my design and I use mills or mundorf resistors to pad down when needed. high now I have them running wide open!! I was hoping an amp might have some adjustment.. Just got a recommendation from someone about ART SLA-2. Looks to be pro sound. Not sure I want to go that route unless I know for sure its good.
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So, if you have an lpad on the mids/tweeter, you can remove it and have absolutely no wasted power at all! Though, you might want some attenuation somewhere. Even 1 db on the woofer can mean the difference between something "too warm" and something "just right" (or even something "bass shy"). |
BTW, I have to wait for the admin to approve my registration to the emotiva site.
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my woofers are 86-87db sensitivity. My mid/tweeters are 90db,
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Looking at the specs, the gain on these Emotiva amps is 29db, where the gain on your modwright is 26db. If you don’t use an active crossover, you’ll probably want to use a speaker LPAD attenuator (parts express) on the woofers to bring down the level. Or spend more and use a passive preamp before the woofer amplifier. |
Thanks aux I'll check it out. |
If you can swing a couple hundred bucks more, there's a pair of New-in-box Emotiva XPA-100 monoblocks over at the Emotiva lounge "Emporium" forum for $550 + shipping + paypal. These would do better than the XPA-200. The title is "XPA-100 GEN 2 PAIR BNIB". Good luck on your amp hunt. |
Wow- that's a rather scathing indictment on a Crown class D amp. Can't even keep up with an aging and clearly limping conventional solid state amp. Sheesh.
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Wow, yeah the HCA1000 could be as old as 1999. Time for a re-cap job! I’ll hang on til the end, lol! There’s a Emotiva XPA-200 on audiogon for $399. That’s $100 off retail, but amp is probably going to be 3-4 years old max. It has more power supply capacitor bank than the HCA 1000, but transformer is smaller. It’s not going to have the brute force of the larger monoblocks, but it’s definitely cheaper, and I’m sure it will be competitive with the HCA 1000.
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Well the parasound amp arrived. And I have to say if I didnt have bad luck I would have no luck at all. I turned it on and it does have more balls than the crown but then I noticed the current limit LED's lighting/ I called Parasound and they said it is probably defective. Sure enough, I opened the unit and the electrolytics are leaking. Thats what I get for buying an old piece of equipment. I'll look for a newer and more powerful amp. Whose got the stamina to hang in there with me ha ha :-P
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New development: A buddy of mine with more equipment than shelves to use this stuff (lol) lent me a Antimode 2.0. Apparently it has a Xo in it. Input impedance not specified. |
Oh, if you do decide to look at the Bryston, be aware they come in several variations. Some have RCA inputs/outputs. Some have XLR. Also, some models have a hard-wired power cord and others have IEC inlet so that you can upgrade the power cord. The $900 agon is hard-wired power with RCA. There is another that's on auction with RCA and IEC power cord. |
Okay, further research on the Krell KBX. It looks like this thing has the crossover frequency/slope hard-coded into the unit by Krell factory and cannot be modified. Krell no longer services these things (possibly), so it may be difficult to impossible to change this KBX to work with you system. And there is no way to "experiment" with different frequencies/slopes, so I'm going to give this KBX a big NO on the recommendation. |
Yep, saw that one. There's a B4 on audiogon/reno-hi-fi for $995. I didn't mention it because it actually has a lower input impedance of 10k ohms. Also, I'm highly suspect about the power supply -- it looks like a basic laptop power supply, so you may have to buy/build a high-quality high-current linear DC power supply to get any sort of performance out of it. I also read that is uses bare JFET transistors with zero feedback instead of full op-amp circuits. The JFETS are biased into Class A, so this crossover will definitely draw some power supply current. I can't comment on the performance of this specific device, but I have seen instances where a bare JFET will sound nice but not have enough brute force to provide enough gain for bass/midbass punch, especially without negative feedback. JFETs in preamp circuits can sound nice - they tend to have a nice rich/lush type of sonic signature, but they are not as crisp/clear as bipolar devices (this is largely a personal preference on sound signature here). The Bryston power supply provides +/-24V (for a total of 48 volts), so the analog circuits definitely have a lot of current to play with for good bass/midbass power. And I confirmed that the circuits are all Class A discrete and use bipolar devices instead of FET based. There's always the Pass XVR-1, which is probably the best of the best, but at $5k+, I suspect it is out of range here. |
Another good x/o is the First Watt B4. All discrete (no opamps), zero feedback. More flexible than the Bryston, with far more available frequencies, and the highly-desirable 4th order-24dB/octave slope, which the Bryston does not provide. $1250 retail, often on sale at Reno Hi-Fi for less. |
The Bryston 10B (that I mentioned above) is likely your best choice for active analog crossover to keep the resolution of your preamp. It has fully discrete analog circuits (probably running in Class A mode) and an excellent power supply. Input impedance is 15k. There’s one on audiogon for $995. They typically sell for well over a thousand. There’s a Krell KBX for $1360 on ebay. It will probably sound more relaxed than the Bryston, but would probably need to be recapped. Also, the front dials do not show crossover frequency steps, so it will be impossible to determine actual crossover frequency without some sort of mic or line measurement device. If you want to go cheaper, you could look at a new Ashly XR-1001, but you’d have to use some special cables (either XLR or 1/4" TRS). It is a pro audio crossover, but it is still fully analog (as opposed to digital/dsp like most of the pro audio crossovers nowadays). Input impedance is 20k ohms balanced (this is probably 10k ohms single ended as I can see a 10k ohm resistor on the input of each XLR leg). You can pick it up for $250 at many musician websites (sweetwater, parts express, etc.). http://s298.photobucket.com/user/maryna1109/media/music/DSCN8468.jpg.html?t=1254515907 The Ashly is not going to be anywhere near the resolution/quality of the Bryston. If I did the Ashly, I would be making significant mods to it. First, Ashly likes to supply power at +/-18V, which is on the high side for normal op amp circuits, but they use normal 7818/7918 regulators. I would be doing the following: - replace the 7818/7918 monolithic regulators with Sparkos Labs discrete regulators and drop the voltage down to +/-15V. - Put in the largest power supply capacitors I could fit in the board/chassis (currently they are only 2 x 1000uf). - Swap out all the op amps with AD797 on dual-channel DIP8 adapters. - Solder 47uf Muse + 0.01uf metallized poly directly to the power pins on each op amp. - Replace all the op amp negative feedback caps with film/foil or silver mica. This is probably $450 worth of components (not including labor).
I’ve seen dbx, Ashly and other analog pro audio crossovers. |
Al, the pioneer is just for testing purposes. If I decide to go for an active XO I will shop for a better one. BTW, I just checked, the input impedance of the parasound is 33k!!!!! Thats great! and the sensitivity is 1.1 for full rated output. This is going to get interesting. I believe I am headed in a better direction. BTW, if you have any suggestions on XO's please suggest. Thanks again. |
Thanks for the update. Although the input impedance of the Crown XLS 1002 is not specified (as Auxinput had indicated earlier), its similarly rated predecessor model, the XLS 1000, was specified as having input impedances of 10K single-ended and 20K balanced. Given also that pro-oriented equipment very often seems to have relatively low input impedances I would think it to be a good bet that the input impedance of the XLS 1002 is the same or similar. 10K happens to be the same, of course, as the specified input impedance of the miniDSP 2x4 HD.
Also, the 20K balanced input impedance probably means 10K per leg (i.e., a 10K load being applied to each of the two signals in the balanced signal pair). And the output stage of the LS100 will see that 10K load in parallel with the 15K to 23K input impedance (at various frequencies) of the KWA 100SE regardless of whether the connection to either amp is via XLR or RCA, since as I indicated earlier the LS100’s XLR output is driven with a single-ended signal.
15K in parallel with 10K is 6K. 23K in parallel with 10K is 6.97K. Both values are of course far below what Dan recommends.
The input impedance of the Pioneer SF-700 Electronic Crossover is spec’d at 100K. Much better! Although it appears that the SF-700 dates back to the early 1970s, so the possibility that it may be in less than top condition is something to keep in mind.
Good luck. Regards,
-- Al
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I bypassed the mindsp and went straight to the crown on the woofer and KWA100SE on the mid/twt. It did sound better. Not wonderful, but better. Next is to try the active XO with a higher input impedance (once I can get it). New amp should be here Thursday. |
almarg, Dan agreed with you. he said 20K is good input impedance 30K is ideal. He is very helpful, one of the nicest guys to deal with. Love his product and his attitude, good karma for sure. I purchased (on his suggestion) 2 output coupling caps to help solve the problem. Your suggestions and help are greatly appreciated. Thanks all was I work through this. I am confident it will be solved in time and with money Lol |
Ill check that later today. I am getting improvement in the system as I work on it. However I would say the bass is not there yet. Ill drive the crown directly from the pre. I would think there would be a sonic difference and will report back. Thanks.
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The XO is a Pioneer SF 700. I will use it only as a low pass at approx
200hz. This is to compare with the mindsp re input impedance and output
voltage. I am using a cap on the input of the Modwright as a hi pass. Just as an experiment, what happens if you bypass the crossover and drive the preamp straight into the power amp driving the subs? The question is, how is the bass then? |
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Aux i got a HCA 1000. They are supposed to have high current capability. If I need to move up the ladder eventually Ill do so.
The XO is a Pioneer SF 700. I will use it only as a low pass at approx 200hz. This is to compare with the mindsp re input impedance and output voltage. I am using a cap on the input of the Modwright as a hi pass. |
atmosphere: we agree. I did find that the phase relationship between drivers was messed up. I had to invert my mid and put the tweeter in positive phase. I use the omnimic and the impulse was negative. Now it is positive. I believe we are saying the same thing :)
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@jimbones , FWIW, polarity is also known as absolute phase. I'm **not** talking about that, instead the phase of just one speaker as opposed to both. We might be talking the same thing, but since there is a bit of interpretation here I thought it a good idea to be certain.
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@jimbones - which Parasound did you buy? Which active crossover does your buddy have? Just call me curious. |
