Toe in the water...

Hi one and all. Amazing how the internet has enabled all this sites participants to create this wonderful resource. I feel like a kid in a sweet shop. These last few weeks since joining I have overdosed on information. I just cant wait to get soldering. There in lies my dilemma - I want to build an amp but am not sure how to match my requirements to one of the many designs available. If I were to bullet point my needs would 'the forum' respond and help narrow down the alternatives?
 
Hello John. Answers in order - very small rooms in the house - mostly 10ft by 10ft - very old house with lots of rooms - brick walls and suspended floors. Varied music - some acoustic, quiet classical, and dub reggae (honest), bit of ambient also. If it has something to say then I like it - hate pop. Lifestyle changes mean I now want to listen relatively quietly, an amp must work without needing to be turned up to come to life, my days of 'full bore' 'full attention' sessions are probably over...shame! Speakers - I have some small high quality speakers (AVI Neutrons but not efficient though maybe 86dB), and some home build in a bigger box slightly more efficient 89dB ?) both very open and I think neutral but definitely dry in the base which I like - my absolute pet hate is wallowy, overblown bass (anything that is seems 'slow') - I am perfectly happy to loose the lowest octave if the rest is snappy and tuneful. Maybe a future project will be a full range driver speaker...
 
I haven't heard much in the way of shop bought stuff to be honest but I am very pleased with my fairly minimalist chip amps. Compared to the Denon PMA-250 they replaced there is no contest. The DX is a step up again from my chip amps (in my opinion)

The Modulus-86 is being well received by what I have read. It is a complex design chasing the absolute best the ic used can give. On the other hand the minimalist Audio Sector LM3875 design has its fans too. Both designers give excellent support on the forum.

If power consumption is less of an issue the Class A Pass Labs designs have a very good reputation. I've never heard one sadly, one day hopefully.

One difficulty for building from a bare pcb is sourcing all the parts and making sure you have the correct lead spacings etc. Some vendors offer a bill of materials with part numbers for easy ordering, others supply boards with all the parts.

The biggest expense generally isn't the amp, it comes from the case, psu, heat sinks, connectors, pots and switches. If you can recycle a used case it can save some money but cost yourself time. It depends which is the more disposable to you.

Hopefully others with more experience than myself will give some input.

John
 
Not a lot of soldering but I now have a good iron with a new tip! Not a problem, will read up on this site and use youtube. Speaking honestly - can you give a quick opinion of the LM3875 against a shop bought amp you might have, for comparison where I should be aiming...

I can give you a brand new opinion if you like having just finished a LM3875 based design last week which is now sitting pride of place in my living room.

For the past 30+ years I've used the much respected A&R Cambridge A60. A great sounding amp that has been rock solid since I bought it for £199 in the early 80s. A loved it's warm smooth sound which, in all honesty has probably degraded over the years but that gradual change will have gone unnoticed by my ears. I still really like it.

The LM3875 however has been something of a revelation. I wasn't sure of the bass initially. It seemed to be more to the fore and certainly punchier than the A60. Not that I didn't like it; it was simply different. Having been playing almost constantly for a week I can say it as pretty much bowled me over as it has bedded in.

As for the midrange/highend? Well I am startled by the clarity. Acoustic guitar and piano is simply wonderful with vocals being a joy.

Safe to say, I am thoroughly enjoying my new baby and discovering new bits in music that I've been listening to for years.
 
Thank you. All comments are truly valued. As a guide I have bought an assembled lm3886 board to get the flavour of a 'chip amp'. Hopefully I won't turn it into a 'french fry'. When its built into an amp I will post a photo - to keep you amused - no sniggering mind... The MX amp you refer to - can I get boards do you know? There are some on eBay ready built - is it like those?
 
Hi Alistair. Thanks for replying. Funnily enough I used to have an A60 ... way back. Glad to hear of your success. You have instantly talked me into checking out the LM3875. I suspected this would happen - lots of happy people's comments - this site is really up beat. Does the amp appear to work at low listening levels (that might be impossible to answer but its just a thought).
 
Heres a simple little lateral mosfet amp.
Its an update of an old Hitach datasheet amp.
I added constant current source to ltp.
I added 2 transistor current mirror.
I added better front end decoupling.
I changed Hitachi mosfets to ALF types.
I added zeners to current limit output.
[IMGDEAD]http://www.ckpr.talktalk.net/lat2.bmp[/IMGDEAD]
 
I have finally answered my own original post question by reading more stuff on this website. It's all in here if you spend long enough digging. Thanks for the chaps who responded, its all useful. I have ordered a stereo LM3886 board ready built, a JLH 1969 class A 10W kit, two LM1875 mono board kits and 2 Burmester 933 mono boards ready populated using Sanken output devices. Quite a spread! And a load of various transformers from eBay of varying sources, and been given bags of electrolytic caps from a talented friend who no longer dabbles with home spun stuff. That was the easy bit. I just cant force myself to spend on the aluminium cases - the are so so so expensive. Near me is an aluminium fabricator (coach builder) who has a lot of aluminium surprise surprise - I will be filling my boots from there later. My analogy of being like 'a kid in a sweet shop' is morphing into 'a teenager with their first girlfriend' - its all beginning to get serious. I wonder if my wife would get me a scope for christmas...It is now clear that the wise amongst you actually measure what you build - I used to think if you cant hear a difference then it doesn't exist or doesn't matter but now I see there are times when an oscillation up beyond our hearing has a horrendous effect within the poor amplifier. So adding bigger caps willy nilly maybe isn't the way to go - there's just a pinch more to it than that. What has surprised me most so far is how difficult the load presented by a speaker is for a designer to deal with. Never saw that one coming.
Q - how would I ask a specific technical question if I cant find a thread already running?
 
Hi,

YMMV but pickup a used Pioneer A300X from epray for about £60,
and then sit and ponder how much it would cost to build anything
that remotely comes close to its build quality. Its a real bargain.

rgds, sreten.

I got one for £45 delivered. Utter steal at that price.
FWIW it includes a more than decent phono stage.

However if your itching to build something go for unusual :
http://sound.westhost.com/project36.htm
http://sound.westhost.com/project37.htm
http://sound.westhost.com/project15.htm
 
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Hi Sreten, yes I want to have a go at something...Damn it!
Thanks for the links - I am going to use the Rod Elliott Capacitance Multiplier for my JLH 1969ClassA boards, so thanks for that. Already ordered parts from Farnell.
The Pioneer A300X was quietly respected in the trade - the A400X scarily so - I had a dealer friend who admitted having a guilty conscience trying to sell more costly amps in his shop - he loved the A400X - said it didn't do anything amazingly and didn't work with difficult (expensive, huge, American ?) speakers but it was entirely musical with all the speakers he sold through his shop. But this is a DIY forum!
Searching for transformers I bought a broken Yamaha AX620 and I too could not believe the components packed in there. It powered up and worked? so the postman must have dropped it quite hard to re seat something!. I could realistically have lived with its character - open, tuneful and slightly warm in the bass - not the bleached cacophony I was expecting. Honestly rather musical. Almost a shame to strip it. Its in bits now. Gave me a 4.56kg frame transformer giving 40 0 40 no load output, mechanically silent and a bag of bits, eBay £20. Bargain. Just need another.
My DIY amp needs to improve on the Yamaha or I'm going backwards. I cannot compete on sophistication of circuitry (understatement) but I can do the opposite - and find out how these low component circuits serve up the music - find that 'thing' that Nelson Pass appreciates.