Say I wanted to build a McIntosh amp from scratch (tubes in preamp only) - Page 1
Forum section: electronics / projects

author: Beamin
author_rank: Super Contributor
timestamp: October 18, 2022, 04:04:45 am
content: Ever since I saw how expensive a Mcintosh tube pre amp, amplifier was I wanted to build one not necessarily a Mc Intosh but any amp, matching and over sizing the parts as I built it. When I was buying my stereo, yes thats right a real 2 channel stereo, those were unheard of in the 2000's, every amp was 5 or 7 channel garbage where sound quality was sacrificed to put a bigger "watts rms" sticker on the front. But fuck all that noise. Why not get a service manual to a McIntosh or similar amp I listened to in the show room, open Digikey and started ordering. I would try this:Order parts that instead of paying extra for tighter tolerances, buy 20 for each one part you need, and put it on the ohm meter, curve tracer,L ,H,F etc, to see how accurate it is and to find matched pairs with the four power transistors. I think you can actually buy them in pairs as it would suck to buy fourty when you need four and still have them not match. There would be no point in building since this is a class AB amp and needs to be clean and even on both sides of the sign wave.Make a board so it fits neatly into an enclosure you already picked out. If the lay out gets too complex break the board down into modululs. Also I would think that with moduals you would have more ground plain on your PCB making for less noise. I would make a separate power supply that I could isolate and prevent noise from getting from the mains into the amp.Find the schematics for a really low noise big power supply (My amp I bought had 0.02% THD, and another super low distortion rating I cant remember, was an order of magnitude cleaner then the nicest amps at circuit city or best buy; the sony was worst at 0.8%, Harmon cardin was 0.08%). Make sure it has a huge beefy transformer (your most expensive part) and Nakamichi chemicon caps and like quality all around. Transformer will no doubt be from china but as long as it doesn't vibrate the lamination's and is wound right there is not much to put into it. You could buy a Furman power conditioner and repurpose the huge torrid transformer (audiophulez say a toroid is better then an E I laminate transformer). OR, with out much fuss turn the conditioner into a power supply, but don't know how hard it is to make negative rails by rewinding the torroid. OR am I an idiot and have no idea how a power supply or AB amp works? Anyways I like the torroid transformer better because you can make the amp flat like a car amp.When if you want to fancy get an arduino and make volume buttons and a remote. Hell you could even build a EQ into it with an array op amps seeing the board to one with 16 channels it looked pretty simple. I think you can also use op amps to make the dancing eq lights.Has anyone here tried this? I know there are MANY here that would see this as an easy project. I wish mr carlsons lab would build something cool like this instead retro looking test equipment. I did start a thread ike this here a long time ago but it got seperated into two different thoughts on the subject and squabbling over who was right. Please dont try to tell me those 4 channel ICs they sell that are complete amps for use in cheap head units has the same sound as two power transistors.

author: bdunham7
author_rank: Super Contributor
timestamp: October 18, 2022, 04:16:32 am
content: How are you going to replicate the custom output transformers? Those are McIntosh in-house proprietary items.

author: Beamin
author_rank: Super Contributor
timestamp: October 18, 2022, 04:19:36 am
content: Quote from: bdunham7 on October 18, 2022, 04:16:32 amThats why I was saying wind the torroid out of a furman power conditioner. What makes those transformers special? Very tight control of having exactly 8200 windings per side or something like that?

author: JDubU
author_rank: Frequent Contributor
timestamp: October 18, 2022, 05:06:13 am
content: Watch this:

author: sahko123
author_rank: Frequent Contributor
timestamp: October 18, 2022, 09:19:43 am
content: If you only want tubes in the preamp stage then you dont need the custom output transformer or even any output transformer.When I built my own amps I used the "First Watt" philosophy which ended up working really well for a small but good 10W amp. If you use quality parts and proper design you can easily get a class AB amp up to a decent 50W with little to no crossover distortion. The preamp stage design is fairly benign and can be easily gotten elsewhere.What is it you are actually looking for in the amp would probably help.

author: jonpaul
author_rank: Super Contributor
timestamp: October 18, 2022, 09:25:04 am
content: see high end hifi forums and groups.Get a junker Macintosh, HH Scott, Fischer or Marantz preamp and amp circa 1960s..1970s, restore it.We have three Marantz 10B FM tuners.Knew Sol Marantz, Sid Smith and Dick SequerraJon

author: bdunham7
author_rank: Super Contributor
timestamp: October 18, 2022, 04:03:07 pm
content: Quote from: sahko123 on October 18, 2022, 09:19:43 amThe topic was replicating a McIntosh amplifier, not a generic one. They use output transformers on their solid state designs.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: October 19, 2022, 07:42:32 am
content: The output transformer needs double C magnetics you need to find first, I couldn't. I bought a 600W toroid transformer, got rid of the coppers and wound by hand. It needs high temperature wire. It ended with a response of 60khz. I also did the same with 400W one the driver transformer. They are huge compared to the original but the work.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 19, 2022, 01:34:22 pm
content: Quote from: Beamin on October 18, 2022, 04:04:45 amIf you want a "sleeper" build, get one of those surround amps for cheap (such as from the used market) and massively upgrade it while minimizing visible changes on the outside.QuoteThe modern TPA3255 will do 0.003% at 100W.