Power amplifier DIY builds..

[Audio tech]

Hello to all..

I'm a time serviced electronics tech by trade and have been repairing many brand name amplifiers over the years.

Now, during 2008 my scrap pile was getting a littte out of hand with lots of blown large power amplifier from crown, peavey, marshall valve amps etc..

Mmm a real haven for lots of parts..ie, heatsinks, large transformers and rack cases.. So, one evening during tea, the light bulb goes off above my head of building a 300w per channel power amplifier for my own use..yes I know, it's easier to buy one in the shops..but, to build your own from pcb to end product unit and say..yes here's my one off amp.

So it had to have lots of protection circuits from soft start circuit, short circuit protect, dc offset protection and over heat cut out etc..

The circuit had to be very, very stable into different speaker loads from 4..8..even 16 ohms even bridge mode if needed( but never had to).

Still after 2 weeks of different circuits trials and wham there it was. 300w per channel of clean power, well my speakers seemed to wake up more in sound!

So who else out there has built there audio amp that does what it says on the tin..and non of this so called pmpo stuff and blows up to quick!

Well happy trails to you all.

 

[SIY]

/raises hand

I should qualify this by saying that I design for real-world operation and extensively use measurement to validate them. No voodoo (other than my aesthetic preference for tubes), just engineering.

 

[Audio tech]

Amen to that..

My flare for electronics started in the late 80's in a old tv repair shop helping out the old grumpy tech, this guy would never give up on a tv or vhs player until it worked.

He looked mad doc from back to the future and always happy to solve the ever growing pile of items in the shop.

 

[DonH56]

I have built quite a few preamps and a few power amps but it has been ages. I learned a lot about how not to build a regulated B+ supply for my tube preamp in the process, along with several ways to short-circuit protect power amps...

 

[Audio tech]

Valve amps they have a full warm sound to them..

Spent many a long night working dsl amps with roasted valves..as one guitar player liked to..(he's words..yes I can bias by my ear and like to see the tube glow just right!)

These day's it double sided print and cheap mass production boards that drive us to ..pop the kettle on.

I do like the old school of point to point hand wired design.

 

[SIY]

Valve amps they have a full warm sound to them..

If you engineer them properly (low distortion, flat frequency response, reasonably low output Z), they shouldn't have a sound, warm or otherwise.

edit: To be clear, I'm talking about hifi amps, not instrument amps.

 

[cjfrbw]

I have only rudimentary skills but have managed to repair some simple items with soldering gun and volt meter.

However, I do haunt the DIY boards from time to time. It is like watching foreign language television: watch long enough, and you start to understand the language. I have learned a lot about cascodes, source followers, different kinds of transistors, buffers, open loop vs. feedback, emission vs. deplestion devices, N and P channels, etc. etc., plus the DIY guys seem to have fun (along with the frustrations), so it is refreshing to hear them build and listen to their stuff. It is also educational to watch the builders measure every device and painstakingly match parts, measure, and re-measure. It shows how attention to detail rather than mass assembly can make big differences. The DIY guys also have acute listening skills divorced from the hyperbole of the subjectivist lunatic fringe.

I don't know if I will ever build something myself, but I am tempted from time to time. Also, some of the DIY stuff can be better than mainstream, expensive commercial stuff. For example, my DIY based VFET Pass 20 watt Class A amp is one of the best amps I have ever heard, and is something that is not commecially available (unless you commission somebody to build one for you).

 

[restorer-john]

I've built lots of amplifiers over the years, but only one that was 300+300 watts per channel. (200+200@8/310+310@4)

It was a 1980s ETI-466 design, two mono boards and two massive Australian Ferguson transformers and quad banks of MJ15003/4 outputs all in a 3 unit rackmount aluminium case- heatsinks out the back. Space in the middle for the 4mm bananas and RCA jacks, power lead and fuse- very reminiscent of the Adcom GFA-555 aesthetic.

I ended up selling it to one of my staff who used it for years DJing and then it spent some years doing PA/Disco work at his church for events. Last time I saw him, it's still going strong. Nothing other than active current limiting and rail fuses in that puppy.

Plenty of lower powered MOSFET/Bipolar amps between 50-150watts. I have a partially finished 350+350 Mosfet dual mono that needs a case someplace using Exicon FETs.

I have well and truly lost the desire to build amplifiers- I have way too many superlative commercial offerings to use and many more to rebuild- I get more joy from fixing the unfixable now than making someting that looks DIY.

I've got plenty of amps I've scavenged because (random examples): "those 12 complimentary Sankens are worth a fortune" or "the 1200VA toroids would be an awesome basis for a big monoblock pair" or "these filter caps are just insane - I have to design a nice amp to use them". I've realised it aint going to happen until my boys have grown up and left home.

 

[Audio tech]

My project was just a one off thing as my day job takes up a lot of time plus family life in the mix also.

 

[Audio tech]

If you engineer them properly (low distortion, flat frequency response, reasonably low output Z), they shouldn't have a sound, warm or otherwise.

edit: To be clear, I'm talking about hifi amps, not instrument amps.

The warm sound is a figure of speach..

Had a few conrad Johnson amps on the bench over the years.

There are many amps to choose out there from class A..etc..