UFW-10/ULW-10 replacement plate amplifier (Dayton SA240) info thread

dane · 06/28/2010, 11:18 AM

This thread is to gather and disperse information for those who are looking to repair a busted UFW-10 / ULW-10 subwoofer from AV123 that might be out of warantee. AV123 has been using a modified Dayton SA240 as their own warantee replacement plate amp for the ULW/UFW-10 subs recently, and the unofficial consensus is that it provides good performance for a vast majority of their users. That only the heaviest bass users will find the Dayton amp a little shy in power output (..but those users are likely to be wanting a larger sub anyway. )

Where to buy Dayton plate amp
- Dayton SA240 240W Subwoofer Amplifier
- Dayton SA240-B 240W Subwoofer Amplifier with Boost
- Datasheet

Differences between SA240 and SA240B
I think the only difference between the two amps is that the SA240B already has a 6dB boost applied at 30Hz. I don't know if this is through adjustment of R35/R36 (see below) or something else. If it is simply by an adjustment of R35/R36 (which is what I suspect is the case), then the S240B is not necessary since AV123's mod uses different resistors values in those two locations anyway. If anyone has any information to the contrary, let me know and I will update this section accordingly.

Modification for UFW/ULW
To be clear-- the Dayton SA240/SA240B should work just fine without modification. The modification listed below adds a 5dB gain centered around 35Hz, which could easily be done with an outboard EQ system if you're not inclined to do the mod yourself. The mod involves removing the four corner screws of the SA240 and removing the back plastic cover. Then pull off the two gain & freq knobs, unscrew the nut on each knob, remove the screw between the line level inputs, and remove the screw from the inside on the riser card that holds the two switches (off/on and norm/rev). That's all pretty easy. The next part involves some narrow pinchers and a soldering iron to remove the two existing R35 and R36 resistors, and then finding the right resistor values to put in their place (see below). The soldering part may not be everyone's cup of tea, however. The datasheet above indicates where R35 and R36 are located. Once replaced with their new values, reassembly the board assembly to the back heat sink plate and replace the top black cover and screw it all back together. (Make sure you do not have any leftover parts! ) For reference, I had tools at my disposal, am a degreed electrical engineer with over 10 years experience, and having never done the mod before it took me about an hour to do the mod, set-up to clean-up.

If you are comfortable with the above modification, then "simply" follow the instructions on the datasheet (linked above) to...

change R35 to 4.7k-ohm, axial lead (through-hole, not surface-mount), 1% tolerance, 1/8th watt
change R36 to 210k-ohm, axial lead (through-hole, not surface-mount), 1% tolerance, 1/8th watt

Unfortunately I did not take pictures while I was performing the modification above. I was tired and just wanted to get it done. If you are not comfortable with the above modification then you can use either the stock SA240 just fine, or choose to use the stock SA240-B that had a 6dB boost at 30Hz. That is very close to the modification results (5dB boost at 35Hz). Alternatively you can use an outboard EQ system like R-DES, a Behringer Feedback Destroyer, or many others.

Sources for Resistors
- Local: Radio Shack, most local electronics repair shops, ...
- Online: Digikey, Newark, Mouser, Jameco, ...

cheers,
..dane

dane · 07-13-10, 08:18 AM

Quote:

Originally Posted by Istari

Thanks for the info - my one question is though, that's a 240W amp..the UFW-10 has long been sold as containing a 500W amp...what's the deal?

Yes, and they have had problems getting their 500W amps to perform reliably in recent years. Some say poor design, some say poor supply chain (black market parts). The cause at this point is fairly moot. AV123 itself is using a modified Dayton SA240 for their own warantee replacement amps at this point.

The Dayton 240W amp will work fine. In terms of dB SPL, doubling the amplifier output power will result in a 3dB increase of output SPL ("loudness"). A 3dB change to the human ear is "slightly louder." To the human ear, "doubling" in volume/loudness requires an change of approx. 10dB, which requires a change of 10x of electrical power.

In short-- going from a 500W to a 240W amplifier will be "slightly quieter" at peak output. However probably most folks are not actually outputting at peak power output very often (if ever) if their systems are properly tuned. And if they're not picky enough to properly tune their subs, then any distortion at the very high output levels will probably go unnoticed anyway. So for practical application (in my opinion), I think the Dayton amps will work just fine. If you're terribly concerned, then you'll just be stuck trying to find a UFW-10 with an ORIGINAL amp (produced before around 2005) if you're fixed on a UFW family of subwoofers. Owners of UFW-10's of that age have (as far as I know) all reported their subs still rockin' and performing well. (I have two original-amp UFW-10's both working solidly well.)

cheers,
..dane

Mark Seaton · 07-14-10, 09:23 AM

Quote:

Originally Posted by RTRluvr

Now that they're selling DIY UFW-12 subs, is there a higher powered Dayton amp for this function?

Yes, we can help with that too. ;) Yes, there are amps available.

Mr Oczka · 07-14-10, 08:15 PM

A quick question for you experts.... I picked up 2 of the ulw-10 kits and would like to run them together. I have a preamp that does not have a subwoofer out, so I was going to run the left and right speaker lines to the 1st subwoofer. Is it possible to daisychain the 2 subs? Can I do it with 2 of the Dayton amplifiers that are recomended? If so, how would I accomplish this? Thanks for the advise.

crazyeddie · 07-14-10, 11:13 PM

Quote:

Originally Posted by Mr Oczka

A quick question for you experts.... I picked up 2 of the ulw-10 kits and would like to run them together. I have a preamp that does not have a subwoofer out, so I was going to run the left and right speaker lines to the 1st subwoofer. Is it possible to daisychain the 2 subs? Can I do it with 2 of the Dayton amplifiers that are recomended? If so, how would I accomplish this? Thanks for the advise.

Well I'm no expert by any means. But in theory, this should work. It's not like you are running power to it, you are essentially just giving it a signal to process from the speaker level (high level) inputs. So it shouldn't present a power draw to the amp (the one your preamp is hooked up to). But to be sure, you should contact Parts Express and talk to one of their tech's. They are usually very knowledgeable. My other idea is, does the amp that you are running your preamp with, have RCA (low level) outs, to daisy chain to another amp with ? If yes, then run the RCA hookups from there ! Usually the RCA inputs are taken as full range coming into the plate amps preamp, before being processed into a low freq. signal to be output to the driver(s). You might need Y splitter cable if you're already using it to go to another amp. But it might be easier than doubling up at your speaker terminals off the back of your amp just to send an input signal to the plate amp. Like I said, I'm no expert, but I think this should work either way ! Good luck !

rsa · 07-15-10, 01:12 AM

Quote:

Originally Posted by Mark Seaton

Yes, we can help with that too. ;) Yes, there are amps available.

If I may paraphrase your answers to see if I understand: Yes, you have spare OEM UFW-12 amps available (that could be modded to work with OEM UFW-12 drivers). Yes, you can provide a higher power Dayton amp to work optimally with the OEM UFW-12 drivers.

My first thought was to try to buy one of the original 1000W UFW-12 amps from someone who did the Hot Rod upgrade—the Hot Rod upgrade didn't require returning the amplifier—then have the option of standing pat with an original UFW-12, or have Motor City Custom Audio mod the amp.

I think we're sort of on the same page. :)

rsa · 07-15-10, 01:16 AM

Quote:

Originally Posted by Mr Oczka

A quick question for you experts.... I picked up 2 of the ulw-10 kits and would like to run them together. I have a preamp that does not have a subwoofer out, so I was going to run the left and right speaker lines to the 1st subwoofer. Is it possible to daisychain the 2 subs? Can I do it with 2 of the Dayton amplifiers that are recomended?

Here's the manual for the SA-240.

The SA-240's speaker-level outputs are high-passed at 125Hz so, no you can't properly daisy-chain by going to Sub#1's speaker-level inputs, then use Sub#1's speaker-level outputs to connect to Sub#1's speaker-level inputs. Note that the SA-240's line level RCA outputs do pass a full-range signal so they can be daisy-chained in this "in-out-in" fashion.

But you can daisy-chain using the speaker-level inputs only. Run your speaker wire to Sub#1's speaker-level inputs continuing directly from Sub#1's speaker-level inputs to Sub#2's speaker-level inputs.

You could also hook up two pairs of speaker wires at your amplifier and run one pair to each SA-240.

A third option is to run one pair of speaker wires to your subs location and then "T" or "Y" the pair of speaker wires (using additional speaker wire and soldering, crimping or twist-nuts) to create two pairs of speaker wires, running one pair to each SA-240.

Disclaimer: I'll second that it wouldn't hurt to e-mail Parts Express about the method you choose.

dane · 07-18-10, 01:48 PM

Quote:

Originally Posted by Jon L

Arrghh. My ULW-10 with the latest and greatest 500W amp, replaced under warranty at factory, around 2/2009, just died on me. Looks like amp problem again.

How long is warranty on replaced amp, and is the Dayton amp drop-in replacement size-wise, without cutting at sub panels?

yes, the dayton amp mounting plate dimensions are the exact same as the original OEM amp(s). Within 1/8th of an inch, anyway. I did not have to cut or force or jiggle it in, it just exactly fit..

good luck..
..dane

Jon L · 07-27-10, 09:42 PM

My failed 500W amp was still under warranty, so I got the Dayton amp to replace it.

When I opened the sub, it was clear what had happened. Along with the familiar burnt-electronics smell, there were charred areas where one or more electrolytic capacitors appeared to have simply exploded. In fact, I found one charred electrolytic cap loose and rolling inside the cabinet
[...snip...]
Sound-quality wise, the Dayton sounds different from AV123, but most of it is likely due to the 6dB built-in bass boost at 30 Hz of the Dayton. I don't blast the sub in this room, so the lower power seems OK so far.

SteveSatch · 07-27-10, 10:25 PM

Jon, I bought one of the ULW cabinets (no amp) and the Dayton amp. My ULW was drilled for the amp, but had no metal inserts and all the holes in the amp lined up with the holes in the ULW. I never heard the ULW with the original or with the second amp, but it sounds real good for music with the Dayton amp (I went with the $140 Dayton with bass boost).

Jon L · 07-28-10, 12:08 AM

Quote:

Originally Posted by SteveSatch

Jon, I bought one of the ULW cabinets (no amp) and the Dayton amp. My ULW was drilled for the amp, but had no metal inserts and all the holes in the amp lined up with the holes in the ULW. I never heard the ULW with the original or with the second amp, but it sounds real good for music with the Dayton amp (I went with the $140 Dayton with bass boost).

Did your screws have pointy ends to screw into wood? My screws have flat ends, so they can't be just screwed into wood, just metal inserts. I suppose I could go get some pointy screws from hardware store and just screw them into mdf where holes don't line up with metal inserts..

And I agree ULW's sound great, especially for music. I do love my sealed subwoofers for 2-channel music. I actually have two 12" sealed M&K subwoofer boxes to build subs from, but the drivers I have require that I expand the driver opening a little, and the openings for plate amps have some issues with screw/metal inserts as well. Man, I need to get to these subs soon..

I did make one with different veneer for a friend, which looks like this and sounds very nice with that sealed sub sound.

SteveSatch · 07-28-10, 01:06 AM

Yeah, I used pointy ended wood screws. I'd leave the four that work and grab some wood screws and use those for the other holes.

rooftop59 · 08-02-10, 09:47 AM

I did the same thing - ulw10 w/ the dayton amp w/ bass boost and agree that it was an easy install. It looks great, TINY footprint, and sounds pretty darn good at low to medium volumes. However, if I start to crank it (I have a wife and a 2 yr old so cranking it for me is probably still pretty moderate) then the big kick drum hits seem to make the woofer vibrate too much and it distorts a little. I am really bummed because I really like it. Any suggestions?
Peace,
Paul