An audio pre-amplifier,  really bad - Page 1
Forum section: electronics / general

author: joeqsmith
author_rank: Super Contributor
timestamp: January 12, 2025, 10:31:03 pm
content: This has to be some of the worse design/workmanship I have seen for a an actual product.

author: bdunham7
author_rank: Super Contributor
timestamp: January 12, 2025, 11:13:24 pm
content: Some old '70s audio equipment (SAE and maybe Soundcraftsman IIRC) were notorious for their "hand made" internal appearance. That's right up there with the worst, but they had some peers. But what do you want for only $4-5k? If you want a tube preamp that isn't a mangled mess, you'll either need to settle for a Chinese-made one at that price (Prima Luna, which is a bit neater, go for $5k or so) or step up and pay some real money.https://www.dagogo.com/audio-note-m10-signature-preamplifier-review/It's $137k but at least the wiring standards are up there with the average Heathkit power supply.

author: themadhippy
author_rank: Super Contributor
timestamp: January 12, 2025, 11:14:04 pm
content: looks like tom evans has some competition

author: Analog Kid
author_rank: Super Contributor
timestamp: January 13, 2025, 07:54:50 am
content: Quote from: bdunham7 on January 12, 2025, 11:13:24 pmFrom the review:QuoteDidn't know what is a "Finite Elemente Cerabase" so I looked it up (https://www.finite-elemente.eu/en/cera-interfaces/cerabase-classic/):QuoteSo what are they?They're goddamn metal feet that you stick under audio components. Only 880 €Fuck these people. They believe in pure voodoo.(WTF??? Two massive separate power supplies (60 lb. ea.) for a fuckingpreamp??)

author: theHWcave
author_rank: Regular Contributor
timestamp: January 13, 2025, 10:20:04 am
content: Quote from: joeqsmith on January 12, 2025, 10:31:03 pmIn Supratek''s defence, they state its a prototype so workmanship & use of glue, no labels ... makes sense. On the other hand a serial 103 speaks against being a prototype, unless they started at 100 to make it look as if the amps are more commercially successful. Also it has been savagely butchered by someone. I could understand if components were removed as parts-donation to other amps but why snip-off the leads of the output transformers? Possibly they sold this for parts and wanted to make sure that it can't be revived.It would be nice to see the inside of a production unit for comparison. On the whole, I am not into audiophoolery but appreciate insights into the design and build of any piece of electronics as an opportunity to learn of good & bad choices.

author: tszaboo
author_rank: Super Contributor
timestamp: January 13, 2025, 10:53:20 am
content: Quote from: joeqsmith on January 12, 2025, 10:31:03 pmIt has an Alkaline battery at the front. Designed to fail.Also, the wiring is by design:https://supratekaudio.blogspot.com/2019/04/wiring.htmlQuoteThere you go, PCBs reduce Magic by 10%, measurable by ear.

author: squadchannel
author_rank: Frequent Contributor
timestamp: January 13, 2025, 10:57:14 am
content: tom evans aprooved.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 13, 2025, 08:32:30 pm
content: Quote from: squadchannel on January 13, 2025, 10:57:14 amThose can't be good connections.And those two stubs that extend beyond the terminal strip: are those some kind of audiophool inductance stubs? micro-antennae? some way to "tune" the circuit? or just sloppy work?

author: Simmed
author_rank: Frequent Contributor
timestamp: January 13, 2025, 08:53:01 pm
content: i dont understand the brown putty thing

author: Analog Kid
author_rank: Super Contributor
timestamp: January 13, 2025, 08:54:15 pm
content: Must be "soundstage adjustment strips" or some such.

author: temperance
author_rank: Super Contributor
timestamp: January 13, 2025, 09:57:12 pm
content: Quote from: Analog Kid on January 13, 2025, 08:54:15 pmNo, that's the crow modifier for if you live in an area with overhead utility lines with crows gathering between 7 and 9h30 AM. The secret is in the pattern.

author: Analog Kid
author_rank: Super Contributor
timestamp: January 14, 2025, 01:23:31 am
content: And why in the world does apreamplifier need huge output transformers?Every tube audio amplifier circuit I've ever seen requires no transformers between stages until one comes to the push-pull (or class A single-ended) output stage.

author: bdunham7
author_rank: Super Contributor
timestamp: January 14, 2025, 04:02:02 am
content: Quote from: Analog Kid on January 14, 2025, 01:23:31 amThe next question is why you need a preamp at all. The trend nowadays seems to be very expensive "preamps" that don't even have a phono stage so they're line in to line out. I suppose you need a volume control...

author: coppercone2
author_rank: Super Contributor
timestamp: January 14, 2025, 07:51:14 am
content: I call that"bush in the back yard in the winter"But glued caps, I thought 95% of these people waned them glued down with silicone. I thought I was the only one that was actually interested in a axial capacitor bracket.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 14, 2025, 11:02:10 am
content: The "amplifier" looks like a show-piece, that should not be used. With the exposed glass tube I don't think it would not pass the safty standards.It it still pretty looking from the outside.

author: iMo
author_rank: Super Contributor
timestamp: January 14, 2025, 01:46:54 pm
content: I can myself hardly imagine I would buy an "electronics something costing more than $10" from a smaller manufacturer without seeing details of the internals, regardless how nice it would look like from outside..

author: themadhippy
author_rank: Super Contributor
timestamp: January 14, 2025, 02:31:54 pm
content: Quotesource selection and as you say volume control

author: Analog Kid
author_rank: Super Contributor
timestamp: January 14, 2025, 09:40:28 pm
content: Quote from: themadhippy on January 14, 2025, 02:31:54 pm2-pole multi-throw rotary switch, ganged potentiometer and you're done.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 15, 2025, 05:36:55 pm
content: Quote from: bdunham7 on January 14, 2025, 04:02:02 amI built a pre-amp for my sister exactly for the reason you mention, lack of a phono input on modern amps. A few years back I repaired my dad's old record player and ran into the same problem. Since I have rebuilt his old amplifier and tuner.https://www.eevblog.com/forum/projects/my-dads-vintage-hi-fi-fisher-amplifier-kx-100/