[EProvenzano]

I'm looking for suggestions for a 2 channel amp to drive a pair of DIY subwoofers.

What do I have?:
Pair of SCC300 Sonic Craft Subs. These are 12 inch subs with 90db eff. in 3.75 ft^3 sealed enclosures.
I've added a Marchand XM44 and I'd like to do away with the Parts Express Plate amps that I have currently installed.
I recently hooked these subs up to a vintage Sansui receiver and I was suprised to hear a significant improvement over the plate amps.
The subs are crossed at 80hz to Ellis 1801's.

What I'm considering:
Must be $400 USD or less. Will consider used.
I've seen many Adcom GFA555's for sale on Audiogon but don't know if these things are any good....they seem to be a dime a dozen, so to speak.
I've read recommendations for QSC and other Pro amps, but the lower priced offerings usually have a fan, and that is unaccptable for me.

Any thoughts would be appreciated.
Thanks in advance.

Happy New Year!
EP

[Rob Babcock]

I have 2 X 500 Watt Hsu amps for my TN-1220's, but at one time I had the subs hooked up to a Carver a400X amp (200 W @ 8 ohms, 350 @ 4 ohms, if I recall).  Damned if the Carver wasn't ballsier and tighter than my sub amps.  Ultimately I stayed with the Hsu amps (close to as muscular, plus a big fat volume knob, and it has the eq and X-over built in).  Some have claimed the Carvers are loose in the bass dept, but that hasn't been my experience at all.  Plus, they are fanless and run much cooler than my actual sub amps.

You can usually find them pretty reasonably used on Ebay, too.

I haven't heard the Adcoms, but I've been told they work well for subs.  They may get a little hot, though, depending on how hard you drive them (they're Class A/B).

[rosconey]

i used a carver pm350(350wpc-8ohm) it stuggled at times with movies.
bought a hk pa2000 (100 wpc)for 150$ of ubid that worked like a champ till my odyssey monos replaced it.

[Rob Babcock]

Isn't the PM series fan cooled anyway?  They're completely diferent amps than the home ones.  My A series amp never showed any strain even running two subs in stereo with big blockbuster stuff (eg Nuke explosion in "True Lies", the warehouse tanker explosion in "T2:  Judgement Day" or the opening saucer flyover/mothership explosion in "Independance Day").

Odyssy monos- that's a lot of amp for subs!

[Brian Bunge]

I've actually spent some time recently helping Jackman with his SCC300 sub both via PM and phone.  He's using a 3ft^3 enclosure with the Apex Sr. amp.  His biggest problem is pretty much no output below 35-40Hz.  I'm pretty sure that'll be rectified once he removes the 6dB boost on the plate amp.

I don't have any specific amp recommendations but suggest going with no more than 200W or so per sub with the enclosures you're using.  Even 200W has the potential to drive the subs beyond Xmax below 30Hz so there's no need to look for huge amounts of power.

[The Oracle]

EP
Could you tell us the PE stock number please?

The Oracle

[IanATC]

Removed, because alas, I missed the point.

Note to self:  Read the bloody topic thouroughly  

[Brian Bunge]

I think 500W is major overkill for this application.  Sure it gives you plenty of headroom, but if you aren't careful and don't calibrate correctly you'll bottom the driver out quite easily.

[IanATC]

IRemoved because I failed to read the topic completely  

[EProvenzano]

Considering my sub, and I do have some experience with it, I think Brian is accurate in saying I don't need any more than 200 watts.
These subs are more efficient than my monitors and present an easy load too. My goal is a perfect blend with my 1801's so I doubt that I will need more than 200 watts to drive it to the volumes that I require in my music only application (I guess I should have clarified that).

If I remember correctly the PE p/n is 300-794.

Brian why do you think the bass *boost* is affecting Jack's output below 40hz? That seems illogical to me. Shouldn't the *boost* give him more response down low?

I heard Dave's SCC300 with that same amp, albeit in a larger enclosure, and it had a very natural roll off and excellent in room response. I've only done very basic measurements of my subs, and they are producing approx. 24hz F3. They are both corner loaded in my 12x18 room on the short wall.

Thanks for the suggestions for the Carver amps. I'll start keeping an eye on those.
Remember my budget is <$400.

Do the Adcom 555's run hotter than average? I am only a bit concerned with this because I will be enclosing my equipment rack shortly.

Thanks for the suggestions guys! Keep 'em coming.

EP

[EProvenzano]

Hi Ian,
Would you mind explaining why I require more 'watts' in my application?
You mentioned that less power would burn out my VC's. This does not seem logical to me considering these drivers are more efficient than my monitors, that currently run loud enough for me with only 150 watts of power.

I'd appreciate it if you would elaborate your idea a little more.
Thanks very much.

EP

[IanATC]

Removed because I failed to read topic correctly.  

[Brian Bunge]

The bass boost serves 2 functions.  First, just as the name implies, it boosts the response at the corner frequency.  Second, it also acts somewhat as a subsonic filter.  Below the corner frequency, the response will have a 12dB/octave rolloff, which basically kills output below that frequency.  Jackman was saying that he didn't feel he had much response below 40Hz.  It may in fact be due to a null.  I don't know since I haven't heard it.  And just because Dave is using the same amp doesn't mean he left the boost intact.  I for one sure wouldn't.  Not that much boost at that frequency anyway.

I think 200W or so of clean power wil be just fine.  I'm quite aware that a plate amp is not the same as an outboard amp.  But, you can kill a driver with too much power just as easily as you can with too little power.  Try putting 2500W into a Tumult with a LT circuit applied.  Voice coil heating occurs from too much power as well.  I know.  I've done it.  And it was clean power.  It's a Crown K2.  Now I'm only using 800W.

If he's going to calibrate the system properly, which I figure he will, then yes I think 500W will work fine.  I've just run into too many people that look at a driver's rated power handling and think the driver can take that much power under any circumstances.  The larger the box, the more efficient the sub and the easier it is to bottom out.  The thermal limits of a driver have nothing to do with it's mechanical limits.

[Val]

Years ago I had an Adcom 555; it did run warm but not overly hot by any means. They should be OK for the task if in good condition.

[EProvenzano]

First, lets not be fooled.  Plate amps do not have the layout of a separate stereo amp.  They have less storage capacitance, and really do not have the same drive power.

A 250 watt plate amp will not have the grunt that a 250 watt QSC, AVA or other component will.

You will be amazed how much cleaner you can get a system to sound with headroom.  The extra "torque"  of a bigger amp will control the sub better in ever aspect from damping, dynamic range, controlling CEMF, and clarity.

If you want an HT ...

Just to clarify.
a/ I am not looking for a plate amp. In fact, I am looking for a separate 2 channel amp because I noticed a significant improvement recently testing a separate amp.

b/ when you say that a higher power amp has more grunt with other qualities like better damping factor etc. I'm assuming that it is those qualities that are important not the extra 'watts'. I would not use the extra watts considering that I will not drive the subs that loud, and if I did they would reach x-max before using all that extra head room.

So far I've learned that more 'watts' means more volume, nothing else...correct me if I'm wrong. The extra watts would be worthless if I'm bottoming out my sub.

That said, what qualities are most important in a strong sub amp? Damping factor?
What is CEMF?

Is it safe to assume that a higher powered amp always has better other qualities, like damping factor?
If this is true then I can appreciate that a higher powered amp may be better, even though I may never use the extra head room. The other qualities would be useful if they are always better in a higher powered amp.

Thanks again for your thoughts.
EP

[zybar]

I am using an Adcom GFA 555 MK II to power the woofers in my RM  40's with very good results.  

BTW, my unit is not in slightest bit warm and it has been running with music for over a day straight as I try and break in the woofers.

You should absolutely be able to get one on Audiogon or E-bay for under $400 and might even get it under $300 if you are lucky.

GW

[IanATC]

Just to clarify.
a/ I am not looking for a plate amp. In fact, I am looking for a separate 2 channel amp because I noticed a significant improvement recently testing a separate amp.

b/ when you say that a higher power amp has more grunt with other qualities like better damping factor etc. I'm assuming that it is those qualities that are important not the extra 'watts'. I would not use the extra watts considering that I will not drive the subs that loud, and if I did they would reach x-max before using a ...

I jumped the gun to start, I admit for whatever reason (this DIY kick I am on)  I kept thinking PLATE AMP.  If I had read your post, I see you are looking for a stereo amp.

CEMF is counter electromotive force, it is what the speaker driver provides, kind of like resisting the  amp pushing it.  Bigger drivers have a higher CEMF usually, but it depends on the voice coil/motor assembly.

You will be fine with any competant 200 wpc stereo amp.  It's best to have one that will double down into 4 ohms.  The adcom, as well as others has enough capacitance, toroidal coil, and output devices to push your sub with ease.  It will do so better than a plate amp is capable of.  As Rob observed, his separates sounded much better than the sub amp he got.  I am not a firm believer in cutting too many corners with current delivery.  I prefer class a/b normally...like the adcom and the majority of stereo amps now.  They do not switch "on demand"  to variable rail voltages for short periods of time like class g,h,t etc.  They have constant power on tap.  

I think you will do fine.  

BTW:  I know someone that has some magnepans and uses the 555 as a sub amp.  Works fine.

[Rob Babcock]

I don't mean to imply the Adcom runs hotter than any other A/B amp, and it does have a good reputation.  But I should point out that with just music you can run your sub 24/7 for weeks without it getting warm.  HT at reference levels is a much harder workout for the sub.  An running Mech Assault thru my Xbox at high volume was a tougher workout for my amp than watching movies (think one long explosion!   )- my sub amp got very hot.

I think how much power you'll need depends on a lot of factors, including not only the output of the subs but also on your room size, listening habits, etc.

Also to clarify, the amps I bought from Hsu aren't plate amps:  they're 19" wide rack-mountable Class A/B bruisers from before they went to switching amps, and I have two of them.  I'd say the extra oomph between one of the Hsu amps vs the Carver in stereo was noticeable but not drastic, and not enough to offset the Hsu amp's greater flexibility.  The big Hsu amp is a helluva a lot better than any plate amp I've seen.