Which amplifier design should I build?

[SimontY]

Hi everyone,

For some time I've been enjoying the sound from my LM3886 chip-amp. I built this as a test to see if a cheap DIY amp could sound ok compared to my main amp, which was a Roksan Caspian. Happily, when used with a DIY op-amp-based preamp, the sound is very good indeed.

The time has come to take things further, and I need some advice from those who have built a power amplifier or two. Firstly, I'll give brief details of what I've had and use now.

I started my hi-fi with a Sherwood amp, 50wpc. This was rubbish and when I later upgraded to a Roksan Kandy integrated I was quite happy. This was driving B&W DM602 s2. Then I made DIY speakers (Audax 8" and 1.25"), and all was fine. Then I build another set of much more revealing speakers (Seas Pontus) and the combination was very harsh sounding indeed, if detailed. So I sold my Kandy and upgraded to the Caspian. The sound was a little more detailed and sweeter, but losing out in slam compared to the more powerful amp I previously owned. To be honest, changing the speaker cable made as much difference as this amp upgrade (DNM Reson to Kimber 4PR). Clearly something was wrong there.

So I began to become disillusioned by affordable commercial gear. It just didn't seem to offer value for money for me. And money is one thing I don't have much of.

So I decided to have a crack of building a simple chip amp. Not the usual "gainclone" but a slightly different thing. It was just built as a test really, using £1 heatsinks from a computer fair and the schematic found in the datasheet. I used a 100va 25vac toroid per side and 3,300uF per rail.

The amp sounded pretty good, surprisingly so. I decided the bass could be a lot better so I tried doubling the caps. This slightly ruined the top end, which was later rectified by using the "snubber" of 1R/22nF across the caps. Still the bass was relatively weak so in came a preamp. I got the gutsy sound I wanted but with the grit and grain of a preamp. So the preamp got tweeked and is now good enough.

And now.... it is time to build a better amp!

My first thought was stick with what I know and build an über LM3886, using the same basic circuit but with a 400va frame transformer, nice psu caps (Elna Cerafine maybe) and schottky diodes. Well, the quote for such a custom transformer was £200 so I've decided to step back and rethink the whole idea. What other options are there I could build? Without having to understand too much technical stuff.

The £300 for selling my Roksan Caspian is pretty much my budget, or a little more if needed. What I'm after is an amplifier with the following characteristics:

- at least 50wpc RMS @ 4ohms
- can be point to point wired or uses a good readily available pcb
- excellent sound quality
- not much more than £300 in parts
- preferably class A/B
- easy to get right and not end up smoking!
- good match for 90db/4ohms speakers
- easy to build second set for future active bi-amping

I could state my sonic preferences but I honestly don't feel an amp has much in the way of a sound. The psu and parts are obviously responsible for making the most of a design, but I want to start with a nice, proven design.

One amp that has come to my attention as an excellent candidate is the Rod Elliott P3A:

http://sound.westhost.com/project3a.htm

This amp has the PCBs, the power and reportedly very good sound quality. It also seems like it should be affordable.

I don't want another "pedestrian" sounding amp! I want emotion, deep bass, toe-tapping timing, amazing detail.... Can anyone help me on my quest?

Thanks for reading and sorry for the essay-like post.

Simon

[rabbitz]

Rod's P101 is better than the P3A IMO.

If you really want it all, have a look at an AKSA.

[SimontY]

Originally posted by rabbitz
Rod's P101 is better than the P3A IMO.

If you really want it all, have a look at an AKSA.

Thanks Rabbitz, I'm looking...

Ok, I had noticed the MOSFET amp design on Rod Elliott's site. Rod says it sounds great, or as much as that man will ever say something sounds like anything. This is definitely an amp to consider then!

I've looked at AKSA stuff and it looks great. The Lifeforce 100 looks like a very serious power amp but would triple my budget. It's simply not affordable at this time. I wonder if one can just buy PCBs. I'm still looking.

[SimontY]

OK, looks like the AKSA 100 kit with most things needed for stereo is just under £300. But with transformers and chassis that's gonna be £400 or so. All the happy customers there say a lot about how nice those amps are. Definitely a contender.

As is the cheaper AKSA 55, which as the name suggests supplies a good-enough 55w RMS into 8ohms. This is "only" £180 without case and transformers or import duty and shipping. Factoring in those extras this is about the limit of affordability.

Opinions welcome!

Thanks,
Simon

[richie00boy]

I say wait until the DIY Fest and check out some designs

[Nordic]

Try Destroyer's DX amp.

Using Pretty straight forward, easy to get components, and electronics cost reasonbly low.. components would probably be 20 or 30 dollars leaving the rest for your heatsinks and transformer/s.

And sound very very good... better than my best GC.

[SimontY]

Originally posted by richie00boy
I say wait until the DIY Fest and check out some designs

This has been a thought of mine! But I don't think the environment will allow for being able to tell any difference between amps. Can ask people's opinions of course.

Originally posted by Nordic
Try Destroyer's DX amp.

Using Pretty straight forward, easy to get components, and electronics cost reasonbly low.. components would probably be 20 or 30 dollars leaving the rest for your heatsinks and transformer/s.

And sound very very good... better than my best GC.

Great stuff, I'll look this up tomorrow when I'm not super-tired. Does it have PCBs for sale? I won't make anything that doesn't have a PCB.

Thanks all,
Simon

[gaetan8888]

Hi

From what I've read, the DX amp are very much better than the Rod Elliott P3A

Here's the link for the DX amp;

http://users.tpg.com.au/users/gerskine/dxamp/


Gaetan

[SimontY]

Originally posted by gaetan8888
Hi

From what I've read, the DX amp are very much better than the Rod Elliott P3A

Here's the link for the DX amp;

http://users.tpg.com.au/users/gerskine/dxamp/


Gaetan

Hi Gaetan,

Thanks for the link! I'm reading up on it and it looks very nice. Of course I know nothing about amplifier circuit design so I need to be guided. I will read people's opinions and take my pick... I do enjoy Destroyer X's posts, even when I don't understand them

Cheers
Simon

[Khron]

Personally, in the following weeks / month i hope to start putting together a few Symasym amps. They've gathered a pretty good reputation around here, as far as i could tell. People say they sound real nice, they measure real well (well under 0.01% THD). They're not that much more complex than the Dx amp, and the components should cost roughly the same.

I'm going to put them to work using an SMPS, a diy active crossover, driving some Seas drivers (in some yet-to-be-finished bookshelf speakers).


http://www.lf-pro.net/mbittner/Sym5_...ymasym5_3.html