Looking for good class AB amp

[surfparadise]

Hi all,

I’m looking for a really good class AB amp that could fit in 2U chassis.
I’m a beginner but I want try to build an high quality amp (2*100/150watt on 8 ohm)
I would build the honey badger but I think is too big for a 2U enclosure.
My idea is to use the side heatskink of the chassis (for example the dissipante of hifi2000)

I found on AliExpress the L12-2. Seams To be be a good amp but ... I don’t know.
I need as well a guide to build it and which checks I have to do before the first switch on (it’s my first amp)

Could you help me to do the right choice?

Thanks

 

[xrk971]

2U is hard to do unless you go with a SMPS. Most toroidal transformers for 100w amp are going to need at least 3U. But SMPS works well too.

VHEX+ amp by Vzaichenko is good 100w and fits 2U. I have mine in 2U profile heatsink.

 

[surfparadise]

Thank you for your answer.

Ok, so better 3U. Understood.

The honey badger is too difficult to build as first amp?

 

[danny_66]

Another from Vzaichenko: Simpelstark

 

[Sadface]

Thank you for your answer.

Ok, so better 3U. Understood.

The honey badger is too difficult to build as first amp?

One could make an argument that it is a bit too much for a first build.

A common approach is to start with a chipamp. They are cheap and relatively simple to implement well. I would suggest this is a good stepping stone before throwing the much larger dollars at something like the honey badger.

It is plausible to build a satisfactory chipamp for less than the cost of an appropriately sized transformer for a honey badger

 

[indianajo]

A common approach is to start with a chipamp. They are cheap and relatively simple to implement well. I would suggest this is a good stepping stone before throwing the much larger dollars at something like the honey badger.

Chipamps require a professional board built in *****. I've found no boards from anywhere else. I tried to build a LM1875 point to point and it motorboated inexorably. I think layout was the problem: too big.
I've built an AX6 point to point and it fits in a 3.5" tall chassis. AX6 - Page 42 -simresults- diyAudio Driver boards were 3.5"x5"x1". 70 w/ch for 5 seconds with one TO3 output transistor pair. (MJ15003 equivalent). Output transistors were mounted on the heatsink 1.5" from the driver board. If you use MJE15028/29 drivers, and heat sink the drivers & VAS, you should be able to use 2 output transistor pair and get to 120 W/ch. That would need a 500 VA transformer minimum. The dynaco ST120 power transformer I used 450 VA @ 70 v is no longer available; the 500 va toroids tend to be too big for everything I measure for installing them in. For example my LM1875 was a 3.5" tall bud chassis. I found a 36v 3 A triad transformer to fit that.

 

[Sadface]

Chipamps require a professional board built in *****. I've found no boards from anywhere else.

LM3886 Done Right: Best DIY implementation of the LM3886 80W gainclone – Neurochrome

This one is from Canuckstan. Reputably the best but I have no experience with it.

Otherwise if one wanted to spend less there is the Gerber files available for 00940's open source design. Apparently this layout is about as good as one gets without forking out for a neurochrome board (According to Tom from Neurochrome)

An open source layout for LM3886?
I'm sure one could find a USA based PCB fab, otherwise JLCpcb have been very cheap and reliable for me.

Various open source PSU boards exist as well.

I am guessing here, but I would suggest a point to point 100w discrete amp is beyond a first time builder.

 

[osscar]

Hi,

2U case imho will be fine for 2x100W amp..for example Indel TST 450VA toroidal height is 60mm (tme.eu) . I attached picture with my 2U amp (Hiraga + 200VA toroidal transformer, but for sure 450VA will fit or 2x200VA). I aloso attach photo of my Leach amp with 400VA transformer ( if i remember correctly) IMHO "Dissipante" 2U heatsink size will be fine for 2x100-150W only PCB size/mounting type matters.

 

[Ian Finch]

Agreed, 100+W amplifiers have been enclosed in standard 2U rack cases for something like 50 years now. A 400-450 VA transformer is an easy fit if the form factor is typical and only 60-70 mm height + perhaps 5 mm clearance for mounting hardware. A standard 2U rack case is 88mm overall height so plenty of room for a class AB amplifier where heat is seldom a problem unless there really is a need to produce all that power constantly.

 

[surfparadise]

Thank you for your help.

Anyway I think to buy a 3U chassis, so I can use it for different type of projects, instead that buy several chassis for every amp that I will try to build.