Advice: which amp to build?

toxtoth

Member
2017-03-03 10:45 pm
I'm looking for advice on which amp to build given the parts that I have left over from various other projects...

I have two high current transformers, 40-0-40 at 800VA each.

i have eight 10,000uf 100v caps

I also have a bunch of 2sa1943 and 2sc5200 transistors and various other components left over.

I'm not too bothered by raw power; more interested in clarity and detail. I quite like dry and clinical sound. This is to drive my front mains.

whats the best Class A or Class AB option?

any suggestions much appreciated!
 
A simple class AB amp with no frills is DestroyerX (poster) dx-blame Mk III - HX
It was posted here. Shown with 64 v rails, your 80 VCT transformer will provide 55. It has 5 pairs O.T.
Usually in this class amps have a VI limiter and speaker protection. The schematic above doesn't have those. More profitably you could buy a 1500-3000 W amp for parts or repair from Peavey, Crown, QSC, and put the transistors in. But those will have transformers & heat sinks. I found I could put MJL21194/93 instead of TO3 transistors by sawing the corners off. I don't know if the same trick will work for 2sa1943 2sc5200.
Much simpler is a honeybadger board available from diyaudio store in the selector strip at the top. But that requires 60 v rails and is only 150 w/ch. It uses 3 pairs 2SA1943 2SC5200.
I can't imagine the heat sink required for a 800 VA class A amp. About the size of a microwave oven I imagine, with a 12" diameter fan.
I usually recommend inexperienced people build a single supply speaker capacitor amp first because if they made a bad solder joint a direct transistor coupled amp will produce DC and damage or destroy your speaker. Some of the commercial amps listed above have effective speaker protection involving proven relays. Speaker protection add on boards via ebay-amazon-alibaba usually have undersized relays that will likely weld the contacts constantly on if a fault occurs. Especially using 10000 uf rail capacitors at high voltage.
50-70 W/ch speaker capacitor amps are Apex AX6, Bigun TGM8, recent Elvee Oldfashioned with a twist, and the amps listed in this thread: A collection of vintage, single supply, low to medium power amplifiers for Daniel - diyAudio
 
Last edited:

toxtoth

Member
2017-03-03 10:45 pm
great suggestions - thank you

i'm not a completely novice but i'm not an expert either. the amp i've worked the most on is the Myryad MXA series (now defunct). I love these amps but i don't see them mentioned much

i would be looking to build something similar - class AB, separate regulated input stage, triple emitter follower

interestingly these amps also feature DC servo which i don't see mentioned much here

are there any DIY designs with these types of features? at first glance it looks like the honey badger is not dissimilar???
 

Attachments

  • Screenshot 2019-11-16 at 22.02.59.png
    Screenshot 2019-11-16 at 22.02.59.png
    582.9 KB · Views: 223
  • Screenshot 2019-11-16 at 22.02.47.jpg
    Screenshot 2019-11-16 at 22.02.47.jpg
    572.8 KB · Views: 223
DX Blame Mk III - HX is a CCS input stage, triple emitter follower output. Doug Self & John Curl believe CCS input stage is better than voltage regulation. Honey Badger is a CCS input stage.
Peavey CS800x and CX800s are regulated input triple emitter follower output, but the input stage is an op amp. Pretty good one, compared to the 1st 2nd 3rd generation CS800 amps which had a noisy op amp.
But the only building you'll do on those is patching the circuit boards where the lands are burnt off. The Peaveys have differential input for long line noise (hum) rejection, and input echo to other amps, which you might find unnecessary or confusing.
I use voltage regulated first stage because the wire count is a lot lower, and I build point to point. Bare circuit board with holes drilled in it. Retro Amp 50W Single Supply - Page 22 - diyAudio AX6 when simmed shows about .06% HD someone said. I like the sound of mine.
 
Last edited: