Looking for amp for weird amp to drive weird subwoofer

[jhaider]

I'm looking for an amp that may well be a unicorn, but doesn't hurt to ask. The criteria are below, with detailed reasons why they are what they are following:

1. Small - let's say outer bounds of 8.5" (i.e. half rack), 1 RU height (could be taller if it's attractive), and 12" depth
2. Signal sensing turn-on
3. High voltage swing for high power at high impedance: 600W into 8 Ohms would be very nice, but half that is likely fine. The matching amp (which I have but is too large to place anywhere useful to drive the sub) is rated 300W.
4. High gain: give full output or close to it from a 1.2V unbalanced input
5. Flat FR down low
6. Either no fans or variable and quiet fans
7. Cost significantly less than a second unit of the amp currently in use but that I will need to repurpose somewhere else in the near future, Powersoft Mezzo 604AD.

Do not care about:

1. Low impedance drive capability (see below)
2. Frequency response load dependency
3. Built-in DSP (will use Monoprice HTP-1 PEQ for any needed transform + DLBC for calibration)

Any candidates?

I've already ruled out a couple:

• AudioControl Bijou 600. @amirm's review of the Rialto variant (they seem to be the same except for the case) showed LF behavior unsuitable for my use case, that correlated with Sound & Vision's measurements of the previous version.
• QSC SPA2-200. I have some positive history with the line (used the SPA4-100 model to run the height speakers in our old house), but SPA2-200 needs more input voltage than my source (JL Audio JLINK wireless receiver) can provide to get to full power.
• Parasound Zamp v3. Tried it. Need more voltage swing.
• Powersoft Mezzo 602A - power is right, cost while less than the fancy model (2 vs 4 channels, no Dante input) is still way too high for this use case. Also, I'm not even sure who distributes Powersoft in the US any more. I'm 99% sure I bought my 604AD from Full Compass, but they don't seem to carry the line any longer. I don't recognize the shops offering this amp that I see in a search (which isn't necessarily pro or con, just that they're not known to me).

Why such a weird amp? The use case is driving an weird subwoofer off a wireless receiver as part of a multisub system. The sub is an Artison RCC300 I picked up because I was looking for a small, zero-vibration subwoofer and was intrigued by this design after seeing some posts from @Chris Brunhaver and @Mr. Widget about them. To my surprise, the impedance of the system is 10 Ohms or higher over its whole bandwidth, which is why voltage swing is the first criterion (N.B. the cabinet was also unstuffed; filling the back half with Ultratouch recycled denim insulation knocked out a couple wobbles in the impedance curve, damped the impedance peak by about 30 Ohms, and lowered the system Q a bit:

I also took out an individual woofer (the baffle is cleverly engineered; I think they even use the woofer magnets to hold the steel grille in place!) and measured it, which shows that despite the high impedance the woofers are wired in parallel (as was clear from viewing the wiring as well):

 

[Hayabusa]

https://apollonaudio.com/product/apollon-nc1200-slm-monoblock-amplifier/ ?

edit: O, no signal sensing...

 

[Blumlein 88]

Would the QSC amp you list work for you bridged? Doubles power output. Reaches that at 1.23 volts input. Would seem ideal for what you need.

https://www.monoprice.com/product?p_id=605030

This Monoprice amp bridged also fits except for no signal sensing. That is probably going to be the fly in the ointment in general. I assume you mean an amp that will go into standby after a period of no signal and not one that can be triggered by another device.

 

[Blumlein 88]

This should work for you. Can be bridged into 450 watts with .7 volt for rated output. Has signal sensing input. It does have volume controls, but you don't have use it after you set the level.

Don't know much about this brand.

Amazon.com

Also sold by Crutchfield where they'll give you home trial period to see if it works I think.

OSD XMP300

Dual-source/dual-zone stereo power amplifier

www.crutchfield.com

Here is the owner's manual.

https://www.osdaudio.com/mm5/graphics/pdfs/XMP300-manual-2018.pdf

This indicates the power rating is somewhat bogus. Maybe 200 or 225 watts rms when bridged into 8 ohms. Or my guess is probably more like 150 watts bridged. If you can get a free home trial with return privileges might work.

2-Channel 150W/Channel, Class D Stereo Power Amplifier, Priority Input and A/B Switching - XMP300

Check out the deal on 2-Channel 150W/Channel, Class D Stereo Power Amplifier, Priority Input and A/B Switching - XMP300 at OSDAudio.com

www.osdaudio.com

 

[Blumlein 88]

Extron XPA 1002 Plus Amplifier Review

This is a review and detailed measurements of the Extron XPA 1002 Plus class D amplifier. I am told used ones go for just $50 to $60 on ebay. Having been designed for the custom integration market, the unit is quite compact and runs very cool. I like the signal and limiter/protection LEDs...

www.audiosciencereview.com

These people make an XPA 2002 which also can be bridged. Is auto sensing. I'm not sure where to buy them, other than ebay. They've made this model for a number of years and it sure is not attractive.

Request Rejected

 

[jhaider]

Would the QSC amp you list work for you bridged? Doubles power output. Reaches that at 1.23 volts input. Would seem ideal for what you need.

That’s 1.23V balanced though. Don’t you have to double that for unbalanced? Otherwise agree this one would be perfect: signal sensing, compact, fanless, high voltage, known quantity to an extent.

I assume you mean an amp that will go into standby after a period of no signal and not one that can be triggered by another device.

Yep. The JLINK receiver doesn’t have a 12V trigger and no way to string any cables to this location. I haven’t tried but would be shocked if the JLINK drew enough power to trigger outlets on a sensing strip.

The Extron is interesting. I only saw 70V versions of that amp when looking. I’ll keep looking. The OSD is too big.

A couple others I “saw” this morning.

Russound A2100 - a little less power than I was targeting, but right input sensitivity, size, and price (several on eBay for around $400 new, which feels reasonable for the application - I just ordered one to try). Properly NRTL safety certified too. I wonder what chip it uses. Hopefully it’s a useful stopgap even if it isn’t the final answer.

Paradigm X-500/MartinLogan ML500 - I’d like to spend less, but otherwise looks like a great fit.

PS: @Hayabusa this use case isn’t a $1500 amp application. If so Powersoft Mezzo 602 or 604 (either one can do 600W into 1 channel) would have been the easy answer and no thread needed.

 

[Sokel]

IcePower 1200as2,all that you asked and more (including signal sensing,clip indicators,all kinds of protections and warnings,even analog outputs for VU meters).
(It's the module inside the Peachtree 500 amp,Amir measured but without the audiophile board in front)
If you can slap it in box yourself fine,its ready to go as is,,otherwise goes around 1k euro cased as I see around.

Edit,scrap it,I overlooked the 1.2V sens,needs 5V to full output despite the 26db gain.

 

[Blumlein 88]

RCA to XLR converter

Ultra-high performance, completely transparent RCA to true balanced XLR converter module. Ready for integration into you DIY audio projects.

orchardaudio.com

This is a bit pricey for what it does. But it is a clean active conversion to balanced output including up to 8 db gain. Price is $299. Might greatly increase the number of possible solutions for you.

If the Russound is enough obviously a much better deal for barely more than this converter.

There are similar devices doing what the above converter does for less than $100. Lots of complaints they either cause hum (definitely bad for subs) or have audible noise.

Sescom makes one which is probably good. Not sure the cost.

Sescom Pro Audio Cables, Converters, Adapters and Extenders

Since 1975, Sescom has been the leader in professional audio cables, converters, extenders and more. We serve the television production, rental, live events, stage and sound, sports, educational, and government markets due to our competitive pricing and dedication to quality production.

www.sescom.com

Amir reviewed the reverse converter and its seems okay. If it is $90 for one channel that is I assume all you need for a sub.

Sescom SES-BUB-1206 XLR to RCA Converter Review

This is a review and detailed measurements of the Sescom SES-BUB-1206 XLR balanced to RCA active converter. It was kindly drop shipped by a member and costs US $90. The converter comes in the typical, robust metal box. I like that the power supply connector has screw lock. Note that this is...

www.audiosciencereview.com

 

[jhaider]

RCA to XLR converter

Ultra-high performance, completely transparent RCA to true balanced XLR converter module. Ready for integration into you DIY audio projects.

orchardaudio.com

There are similar devices doing what the above converter does for less than $100. Lots of complaints they either cause hum (definitely bad for subs) or have audible noise.

I've had to use such devices before. A long time ago I tried to drive multisubs controlled by an OG miniDSP 2x4 (I think 0.7V output?) with NHT A1 monoblocs (Outlaw later simplified the faceplate and sold that design as well, bench test here.). I tried a couple. ART had one but the bass FR was unacceptable. I settled on one from Samson I think that performed well. Blue box with grey corners. But the issue is simply boxes: I don't want a third one. As it is there's already the wireless receiver and amp. I don't think there's any more room to hide boxes under the sub on the legs I bought for it. I also don't want a second wall-wart behind the piano.

The Russound amp is here. I haven't had a chance to hook it up, but I did peer inside. It seems like a nicely built little thing. I'll make a separate teardown thread when time permits but here's a sneak peak.



I know little to nothing about electronics but I can read part numbers. It looks like the Class D amp is an IRS2092S (2x) and the output devices are 5x (???) IRFB4019.

@amirm measured a DIY IRS2092 (same thing?) based amp - results were poor for full-range usage but may be just fine for an inefficient and high impedance sub. I don't know how the PS or output devices compare, but Amir pulled 150W/8Ohm and what looks like potentially 640W/8Ohm bridged. So I'm optimistic thing little thing will work for my weird use case. It appears SVS SB3000 uses the same amp chips as well.

 

[waynel]

I'm looking for an amp that may well be a unicorn, but doesn't hurt to ask. The criteria are below, with detailed reasons why they are what they are following:

1. Small - let's say outer bounds of 8.5" (i.e. half rack), 1 RU height (could be taller if it's attractive), and 12" depth
2. Signal sensing turn-on
3. High voltage swing for high power at high impedance: 600W into 8 Ohms would be very nice, but half that is likely fine. The matching amp (which I have but is too large to place anywhere useful to drive the sub) is rated 300W.
4. High gain: give full output or close to it from a 1.2V unbalanced input
5. Flat FR down low
6. Either no fans or variable and quiet fans
7. Cost significantly less than a second unit of the amp currently in use but that I will need to repurpose somewhere else in the near future, Powersoft Mezzo 604AD.

Do not care about:

1. Low impedance drive capability (see below)
2. Frequency response load dependency
3. Built-in DSP (will use Monoprice HTP-1 PEQ for any needed transform + DLBC for calibration)

Any candidates?

I've already ruled out a couple:

• AudioControl Bijou 600. @amirm's review of the Rialto variant (they seem to be the same except for the case) showed LF behavior unsuitable for my use case, that correlated with Sound & Vision's measurements of the previous version.
• QSC SPA2-200. I have some positive history with the line (used the SPA4-100 model to run the height speakers in our old house), but SPA2-200 needs more input voltage than my source (JL Audio JLINK wireless receiver) can provide to get to full power.
• Parasound Zamp v3. Tried it. Need more voltage swing.
• Powersoft Mezzo 602A - power is right, cost while less than the fancy model (2 vs 4 channels, no Dante input) is still way too high for this use case. Also, I'm not even sure who distributes Powersoft in the US any more. I'm 99% sure I bought my 604AD from Full Compass, but they don't seem to carry the line any longer. I don't recognize the shops offering this amp that I see in a search (which isn't necessarily pro or con, just that they're not known to me).

Why such a weird amp? The use case is driving an weird subwoofer off a wireless receiver as part of a multisub system. The sub is an Artison RCC300 I picked up because I was looking for a small, zero-vibration subwoofer and was intrigued by this design after seeing some posts from @Chris Brunhaver and @Mr. Widget about them. To my surprise, the impedance of the system is 10 Ohms or higher over its whole bandwidth, which is why voltage swing is the first criterion (N.B. the cabinet was also unstuffed; filling the back half with Ultratouch recycled denim insulation knocked out a couple wobbles in the impedance curve, damped the impedance peak by about 30 Ohms, and lowered the system Q a bit:

View attachment 314306

I also took out an individual woofer (the baffle is cleverly engineered; I think they even use the woofer magnets to hold the steel grille in place!) and measured it, which shows that despite the high impedance the woofers are wired in parallel (as was clear from viewing the wiring as well):

View attachment 314307

Why not just buy a better powered sub? Looks like a pretty weak sub so a better powered one might be less money than an amp. A rhythmik l12 or an SVS sub 1000 pro will vastly outperform it.

 

[jhaider]

Why not just buy a better powered sub? Looks like a pretty weak sub so a better powered one might be less money than an amp. A rhythmik l12 or an SVS sub 1000 pro will vastly outperform it.

Unhelpful and out of scope.

Perhaps there’s more than you know or understand behind the decision making process and constraints here.

 

[waynel]

Unhelpful and out of scope.

Perhaps there’s more than you know or understand behind the decision making process and constraints here.

Are you willing to explain? It seemed like an $800 amp
was quite a lot to drive a pair of 5”x8” woofers.

 

[jhaider]

Are you willing to explain?

Subwoofer near a piano - terrible idea?

We recently bought an upright/console piano for our living room (replacing a digital keyboard) and as a result of room reconfiguration (the keyboard had an HVAC under it) one of the 5 subs had to go. The sub itself was modest (an older NHT model called Verve, a wide-but thin closed box with 2...

www.audiosciencereview.com

It seemed like an $800 amp
was quite a lot to drive a pair of 5”x8” woofers.

I’m not sure what $800 amp was involved. The original amp pressed into service (Powersoft Mezzo 604AD) is stupid expensive for the job (about a grand more than your figure) but happens to be available until some renovations are complete. The amp I’m currently considering as a replacement was about half your figure.