Low cost gainclone vs discrete

[angel]

Hello,

I'm looking to build a cheap ~2x10Wrms@4ohm amp for a friend of mine, and am wondering whether a gainclone or discrete design would be likely to give the best price/performance tradeoff below ~USD250. 4x5Wrms would also do the trick.

The speakers to be driven are ported 2-way d'Appolitos that are nominally 4 ohm and support biamping. They are efficient enough that when driven with my own amp, the meter shows peaks of about 2W or so at plenty loud volume.

I have prior experience with constructing amps, and think I've cut off many of my thumbs by now (), but I'd like to avoid surface mounting if possible.

[officeboy]

Well considering parts for a chip amp can be as little at $5-10 per channel. Add in a pot for volume control, and a transformer..
Pretty easy to get 35W per channel with a 3875 for easily under $100 if you don't go crazy on the chasse.
National lists the LM3875 as $2.40... hard to beat that with discrete parts for an amp.
I know my aleph-x will be a lot more then that.

[Nuuk]

Yes, that is almost a 'no contest'!

'Build your friend a Gainclone and he will be a friend for life'

[till]

with gainclone you will have the most power for your money in a sensible range of 30 to 50W.

With very high efficient speakers i would go for a discrete simple low wattage class a like http://www.passdiy.com/projects/zenlite1.htm or http://www.passdiy.com/pdf/sonofzen.pdf

[moving_electron]

Originally posted by officeboy
Well considering parts for a chip amp can be as little at $5-10 per channel. Add in a pot for volume control, and a transformer..
Pretty easy to get 35W per channel with a 3875 for easily under $100 if you don't go crazy on the chasse.
National lists the LM3875 as $2.40... hard to beat that with discrete parts for an amp.
I know my aleph-x will be a lot more then that.

If you are building it for a friend and s(he) is putting up the money for the components, I imagine that you would tend to cut down on the personal time you might normally use to build enclosures from scratch, scrounge components etc. Your objective might be to efficiently implement a very good sounding and well finished result.

In that case you will likely purchase items fairly ready to go. If you built the Brian GT premium kit with a Par-Metal box with enough space to add regulated power supply later, new transformer, reasonably nice connectors etc. Your cost will be closer to $250 by the time you include shipping and all those little things you need.

I think you would be much better to set $250 as an expectation for your friend.

To expand on earlier comments, in the power range that the gainclone currently excels, I think it is fair to say that there really is nothing that compares to the sound quality and ease of implementation for the price. For some it is the be-all-end-all. Others are implementing discrete and tube amplifiers and enjoy the results those bring. Arguments about the "best" amp will likely continue throughout at least our lifetimes. I hope so, it makes all of these types better!

But questions of whether it is the ultimate etc. aside, there is almost no one who doesn't agree that a properly implemented gainclone is a very good sounding amp and the most bang for the buck in it's power range.

[sreten]

Hmmm..... JMO

A 10W / 4ohm JHL, DoZ or Hiraga is within budget,
but more difficult to make and requires much bigger
heatsinks and more attention to the power supply.

Attention to detail is important for top performance.

Only worth doing if the rest of the system is seriously aimed
to top quality and towards musical not "Hifi" reproduction.

Otherwise go for a chip amp with regulated supplies.

sreten.

[moving_electron]

Angel,

It looks to me like adding a regulated power supply costs about $65 USD before tax.


Sreten,

In your experience, what speaker efficiency would be required with a 10w class A amp if:

1) the goal was to be able to play music reasonably loud occasionally (would have to speak fairly loud to talk to a nearby person but not have to shout)

and

2) lower frequencies were handled by a sub crossed over at 80hz

What if there were stereo subs instead crossed over at 150Hz or 200Hz?

[till]

lets say at 90dB you are not able to talk to another person without shouting direct in the ear. Also at 90dB you will experience hear damage after one or two CDs of listening. Lets say we want 6dB peaks over the 90db average leve. So a 90dB at1W aand 1m speaker would need 4 Watt in caseit is 1m away from your ear. I think 8 Watt in case it is away 2m ? not sure about that.

[officeboy]

Originally posted by moving_electron
Angel,
It looks to me like adding a regulated power supply costs about $65 USD before tax.

Buying everything from digikey (shopping around you could get way better deals then that) $23 is my total; so are you talking dual regulated supplies. Or are you including the transformer?

Or using Caddock resistors in the supply?

[moving_electron]

Originally posted by officeboy



Buying everything from digikey (shopping around you could get way better deals then that) $23 is my total; so are you talking dual regulated supplies. Or are you including the transformer?

Or using Caddock resistors in the supply?

Hmm.

I am not sure which prices I looked up and which I just put down an estimate for. The diode cost is kind of a duplicate because presumably you could use the MUR860 diodes ($1.09 each) and the 47uF caps that come with the brianGT kit. But I was figuring the incremental cost assuming I added the regulated supply in a couple of months and kept the kit PSU intact for some other project. Likewise the 1000uF caps that come with the kit would get used elsewhere.

Anyway here were my numbers based on Predja's design http://users.verat.net/~pedjarogic/a...e/supplies.htm
and carlosfm comments:
Gainclone Power Supply Design thread

SB560 diodes (8) = .44 x 8 = $2.64
LM338T (2) = 2.11 x 2 = $4.22
47nf poly (4) [Wima MKS] = 2.00 x4 = $8.00 (probably made a mistake here may need only 2)
33uF caps BG = 1.75 x 4 = $7.00
47uf caps = 2.00 x2 = $4.00
Resistors = did not add anything, assumed I had them
Variable resistor multiturn = 3.00 x2 = $6.00
4700 uF caps (4) = $5.00 x 4 = $20.00 ( I probably figured 63V overkill)
1n4002 prot diodes (2) = .30 x 2= .60
____________________________
Total = $52.46 USD

I figured shipping, some veroboard, standoffs etc. would add another $13.00 or so bringing the total to $65.00.

$23.00 sounds alot better though! I hope you are right!