DIY amp for kit 281s

Discussion in 'Home Theater Projects' started by Jordan_Brulotte, Jan 10, 2005.

  1. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    Hey guys. On my quest to build a complete DIY home theatre, I started thinking about building an amp to run the kit 281s, LCC, and 81s that I will be putting together. Now the most popular DIY amp I've seen so far is the Gainclone found HERE. Now this amp will be primarily used for HT use, and as the 281s are not that efficient, I was wondering how well a gainclone would work. From what I hear, the sound quality from these DIY amps is quite good, but do they have the Oomph I'd need for home theatre? I've heard of some people running 2 paralleled for 120w output per channel, but I have not seen it , nor have I seen schematics for this. I also have not seen anyone build a 5 channel or more amp.

    Basically, my question is this... are the suitable for what I'd be running on them, and for future upgrades? If not, are there kits or DIY amps out there that I have not heard about which may prove to be better solutions?

    Thanks
     
  2. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    I don't know about the GainClone amps. I do know that the larger ASKA modules will certainly power a 4 ohm load.
     
  3. Michael R Price

    Michael R Price Screenwriter

    Joined:
    Jul 22, 2001
    Messages:
    1,591
    Likes Received:
    0
  4. MarkRoberts

    MarkRoberts Stunt Coordinator

    Joined:
    Oct 20, 2002
    Messages:
    167
    Likes Received:
    0
    Go here check out the class d section particularly the ucd 180 or ucd 400 threads. I haven't built them or heard them playing santa this year set me back quite a bit[​IMG] Oh you can google hypex amp modules and find thier site. I read that if you order from them it will save you some $ over ordering from adire. They also carry the ucd's.
     
  5. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    I was under the impression that class D amps were mostly used for subwoofers, as their output isn't as clean as other varieties.
     
  6. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    The high-end switchers; ICE modules or UCD are fine. The cheap switchers should be avoided.
     
  7. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    Thanks for the help so far guys!

    What are your opinions of the Passlabs Zen, and Aleph amps? Once again these appear to be designed more for high efficient speakers.

    The Hypex modules look interesting, but my main reason for wanting a DIY amp is so I have another project to work on and put together myself from scratch.

    I should point out that I'd like to keep my budget between $400-$800 CND ($330-660 US). This will be for 5 channels, either all in one amp casing or as 5 monoblocks. As an "artist" a DIY amp will give me a TON of creative license with the look.

    Thanks again guys.
     
  8. Michael R Price

    Michael R Price Screenwriter

    Joined:
    Jul 22, 2001
    Messages:
    1,591
    Likes Received:
    0
    The Zens and Alephs sound great, but they're probably not powerful enough. I have a Zen V4 and it's incredibly anemic sounding despite really special midrange and treble quality. An Aleph 5 or larger sounds very good (got to listen to one... very relaxed and detailed, but without the addictive power of the big Class AB amps). The UCD400 modules look like a great choice especially for saving time+effort relative to building an amp from scratch. And judging from the initial response, they probably sound as good as anything else you could build with that kind of power.

    Unfortunately, I don't think you can build 5 channels of appropriate amplifiers for US$660. The sym amp project cost me $400 for two monoblocks; and the UCD modules cost $300 per channel plus power supply costs. Power electronics (transformers, heatsinks, etc) are relatively expensive and when 200 or 300 watts are required to really get the speakers going, a quality amplifier is an investment whether you build it or not. You could try some combination of gainclones, but it just doesn't seem practical given the 84-87db efficiency of the speakers. I would go for a stereo amp or two monoblocks if you're looking for a DIY project, then use commercial amplifiers for the rest until you can afford to build better ones.
     
  9. eric nyhof

    eric nyhof Stunt Coordinator

    Joined:
    Mar 10, 2002
    Messages:
    74
    Likes Received:
    0
    Jordan,
    I am in the same boat as you, looking for a DIY amp to run some 4 ohm speakers. I'm leaning to the gainclone kit from www.chipamp.com when it becomes available again.
    I'm going to order 2 kits to run 2 chips per channel.

    There is a spreadsheet available from National that will give power output for the LM3875 (gainclone). With 2 amps in parallel with an 18 V transformer (25V rails) you will get 95 watts per channel, and give you the 4 ohm stability.

    I think the kits will be available at the end of Jan.
     
  10. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    Eric, I can follow diagrams or schematics, but I am not very good at imagining the circuit in my head... How would 2 of these kits actually be wired in parallel. I assume that it is not as simple as just connecting the input and outputs in parallel.

    Do you have a schematic for paralleled gainclones?
     
  11. Paul Spencer

    Paul Spencer Stunt Coordinator

    Joined:
    Sep 15, 2003
    Messages:
    159
    Likes Received:
    0
    Jordan,

    I think the issue with gainclones is not so much their stability at 4 ohms or their power but rather that they have a lot of protection built into their chips, hence if pushed to clipping, they sound bad. They should not be used at a level where they will clip or come close to it, hence I think they are best suited to active speakers. I intend to use mine to drive a tweeter.

    I know a guy who built a gainclone and we compared it to a rotel, the latter sounded just slightly better, but he wanted to build a lot of channels, and there was a rotel of comparable power and number of channels that was actually CHEAPER! Although this depends on how much you spend on the case, connectors, etc.

    Aksa kits are worth considering, I've met Hugh from Aksa, he came to a DIY speaker event here in Melbourne that I organised, and I can tell you that he is a good person to deal with.

    Another option is kits from Elliott Sound Products (another Aussie, now I'm getting Patriotic!) ... They have a good amp that is a bit more serious than chip amps - their P3A. Rod is also good to deal with. I have bought some of his PCBs.
     
  12. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    Thanks Paul, I did not realize that the GC's sound quality would change so drastically when pushed hard. I'm getting a lot of good info from you guys and I appreciate it.

    The Aksa kits look good, but they are out of my price range, as they are nearly $630 for 2 channels.

    The ESP P3A looks great too. Paul, do you happen to know if it comes as a kit, because it looks as though only the PCB can be ordered from him. This amp looks promising.

    I'm not going to give up! Even with my modest budget I'm sure I'll figure something out.

    I hope my dream of a full DIY theatre wont go up in smoke [​IMG] .
     
  13. Paul Spencer

    Paul Spencer Stunt Coordinator

    Joined:
    Sep 15, 2003
    Messages:
    159
    Likes Received:
    0
    Jordan,

    I did an estimate of the cost of a chip amp vs an ESP P3A power amp. The cost of the latter was not much more. The most expensive parts are the case (not that bad if you just buy sheet metal, but quite expensive if you buy a pre made case ... also not so bad if you get sheet metal fabricators to cut and bend some sheets) ... the heatsinks and the transformer. The inputs connectors can be a bit pricey if you get nice ones and use a lot of them. I think I estimated the ESP P3A would cost about AU $250 to build.

    So, in a nutshell, I think it's worth the extra cost (not much more) to go with an ESP P3A unless you are sure you will never push it to near clipping levels (and that is only going to happen in an active speaker).

    I can't say I've heard the nasty clipping effect on a chip amp, I'm only going from what Rod Elliott wrote up on his blurb about the chip amp. I assume it's a general characteristic of gain clones, since they would use probably the same chip.

    One nice feature of the ESP chip amp (gainclone) is that it has a mute function built into the chip. This means there is no thump when you turn it on/off.
     
  14. MarkRoberts

    MarkRoberts Stunt Coordinator

    Joined:
    Oct 20, 2002
    Messages:
    167
    Likes Received:
    0
    I understand your disire to build the amps from scratch but it might prove cheaper to start with modules. It is going to be hard to hit 5 channels for $660.00 If you order the ucd's straight from here It looks like the ucd 180 would cost around 120.00 USD ea and the ucd 400 160.00USD with shipping. I estimated the shipping costs and taxes since I don't think the site will calculate it right now. You could always shoot them an email if you want to know for sure. Shipping might not be so bad if you order all 5 modules at once. After you figure power supply(s) and transformer(s)you will be over budget I think [​IMG]
    You might want to consider this it is only 9.96 over your budget before shipping and is 150W X 5 into 8 ohms. Or save a little more and go for an outlaw 7100 and bi-amp your 281's since you will have 7 channels at your disposal [​IMG] Can't vouch for the sound quality of the AMC but I am sure you could find a opinion or two around here.
     
  15. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    hehe ya I'm starting to become depressed...[​IMG]

    I'm still going to investigate the P3A from ESP that Paul and others have mentioned a bit more. Looks good and may still fit into my budget.

    Mark, I've already decided that if I can't go DIY, then the outlaw 7100 is probably my top choice [​IMG] . Great minds think a like eh? My other choice will be the Rotel RMB 1075.

    They are both outside my DIY budget, but they are proven to be quite good amps, with quality compnents. Plus the extra cost would more than pay for the work I'd do building my own.

    Thanks again for all the help!
     
  16. Michael R Price

    Michael R Price Screenwriter

    Joined:
    Jul 22, 2001
    Messages:
    1,591
    Likes Received:
    0
    As depressing as the cost is, the DIY amps are a good cut above anything you can buy at the the equivalent price. You may also like the sound of a smaller DIY amp like a Gainclone or P3A better than a commercial amp even if they're less powerful. But my honest opinion is, if you're going to go to all the trouble of building amplifiers, you might as well invest in something robust that will really work its best with the Adire speakers. It couldn't hurt to use regular amps and build something for the front channels! Though given the choice, I'd buy the 7100 and actively bi-amp. [​IMG]
     
  17. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    I am not completely familiar with the inputs cups that come with the 281s... do they have dual inputs?

    To be honest I am not quite up to speed on bi-amping at all. I will definately have to read up more on this topic.

    Quick question though. If I Biamp the mains, wont the center channel sound a little bit "off" from the left and right?
     
  18. Paul Spencer

    Paul Spencer Stunt Coordinator

    Joined:
    Sep 15, 2003
    Messages:
    159
    Likes Received:
    0


    My experience has been otherwise. I compared a gainclone to a Rotel (which is cheaper than what they guy spent if you compare 5 channels of the same power), the Rotel was noticeably better. I'm skeptical of such comparisons usually, but in this case I was expecting not to hear any difference at all.

    I can't say it was a proper test. You really need a group of people and a blind test to really judge things impartially. I heard of one such test where no one could consistently pick the expensive amps over the cheap ones. The design engineer of one of the high end expensive amps was not concerned about this at all, his comment was that amps should not have a sound at all until they are pushed into clipping. But the sales people from that same company were indignant to hear such results. In the end it pays to form your own opinion, and to avoid allowing it to be coloured by most of what you hear about "amplifier sound."

    One thing to keep in mind is that of all the components in the signal chain, DVD players, AV processors, amplifiers and so on do the job asked of them vastly more successfully than your speakers and the room.

    I suggest caution with your first diy amp. Don't make it expensive, and don't buy a whole lot of them. Make one and get it right first.

    IMO you don't often save money by making diy amps, although that would depend on the amp itself. If you are looking at "budget audiophile amps" like AMC, NAD, Rotel, etc vs gainclone amps you might find you can match the performance for the same cost at best. You might be at a slight advantage with 2 channel, but with multichannel amps, I doubt you gain in dollar terms. If you want to build a very high end amp, the margins and hype surrounding comercial amps probably make a diy equivalent MUCH more cost effective.

    For 2 channel, an amp to consider is the Alesis Matica RA series. They have been compared to Rotel, NAD etc and they are amazingly cheap - so much so that I intend to get the RA500 with 250w for my speakers later on, I won't bother trying to compete by a diy amp, I would end up spending the same amount if not more. They are nice stylish amps. Some also dispense with a preamp and just use the attenuators. For 2 channel, Rotel are more expensive. You could actually get 3 of the RA300 for $280 each here (I did a quick search) and it would cost you $840 for 6 channels of 150w each (4 ohms).

    That looks like a similar cost to the Outlaw, and similar specs.

    You may wish to mix and match. For your mains you may want more power. ESP also has a high power mosfet amp, which is designed for high fidelity. Also there is the Alesis RA500 with 250w into 4 ohms. Some people think that putting that much power into hifi speakers is dangerous. It's not. I have hooked up my PA amp (which I use for my subs Behringer EP2500 which is class H), to my main speakers, it's quite listenable, and you will be surprised that when you hook up a high powered amp, the speakers can seem to go further than you thought they were capable.

    Now to keep things simple, here's my suggestion:

    Probably one of your best short term options is to go with the Outlaw or something similar. Great bang for buck, you probably won't build something cheaper and better, and the big plus is you hook it up and first time it WORKS! No hum, no problems to fix ... just does the job right away!

    Keep your diy urge, but use it to upgrade. On your first diy amp, it's nice to not rely on it as your only amp, but have something working. Consider an active xo to your mains. Steal one of the channels of power from your outlaw temporarily. Have fun with the case. Then you might want to have a go at a diy amplifier for your tweeter, say have a go at a gainclone, a simple first diy amp what won't be driven hard. I'm working on doing something like this myself, still have to get rid of the hum on my chip amp, and have found that my active xo kit needs work - the 4LR filters aren't the best for my drivers.
     
  19. Jordan_Brulotte

    Jordan_Brulotte Stunt Coordinator

    Joined:
    May 24, 2004
    Messages:
    104
    Likes Received:
    0
    Paul, great advice! I never really thought of it in that way. Having a consumer amp to fall back on is a great idea, as I would not want to be unable to watch movies or listen to music while I am building a DIY amp. Going DIY for upgrades may just be the perfect solution. Small additions here and there as more money is available.

    Sometimes I want to dive in, but at least I check the waters first[​IMG] .

    The Alesis amps do look quite good too. At least I have a bunch of options available to me![​IMG]
     
  20. MarkRoberts

    MarkRoberts Stunt Coordinator

    Joined:
    Oct 20, 2002
    Messages:
    167
    Likes Received:
    0
    You should be able to bi-amp the kit281's no problem they come with dual input cups with a jumper. One set of inputs should go to the tweeter xo and the other should go to the woofer xo. Just use a "Y" to split your pre-amp signal to to channels and use two channels to drive each tower. You could take it farther and use a first order HP filter on the tweeter amp input (pre-amp) side. Don't know how much if any difference would be heard. In theory the speaker xo wouldn't have as much filtering to do. Then you wouldn't be amplifying frequencies that the xo is going to filter anyway. I have a tutorial link somewhere if I find it I'll post it for you.
     

Share This Page