An audio pre-amplifier, really bad

[joeqsmith]

This has to be some of the worse design/workmanship I have seen for a an actual product. 

[bdunham7]

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.

[themadhippy]

looks like tom evans has some  competition

[Analog Kid]

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.

From the review:

At some point, we inserted Finite Elemente Cerabases under the preamp and its two power supply boxes, which rather significantly improved the sound in all the ways that one might expect.

Didn't know what is a "Finite Elemente Cerabase" so I looked it up (https://www.finite-elemente.eu/en/cera-interfaces/cerabase-classic/):

The top-of-the-line model of the Cerafamily harmonizes transparency and three-dimensionality with precise definition, rich tonality and vibrant dynamics. The newly gained integrity and emotionality of the music enrich the listening experience beyond comparison.

So 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 fucking preamp??)

[theHWcave]

This has to be some of the worse design/workmanship I have seen for a an actual product. 

In 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.

[tszaboo]

This has to be some of the worse design/workmanship I have seen for a an actual product. 

It has an Alkaline battery at the front. Designed to fail.
Also, the wiring is by design:
https://supratekaudio.blogspot.com/2019/04/wiring.html

But all the commercial audio products used printed circuit boards (PCB's) so  I had one designed and made for the first commercial Supratek linestage.

Very quick and easy to build but it didn't sound like a Supratek .

So I asked the PCB designer to do it again, with a different earth configuration , as I hoped that was the problem.

Still not nearly as good as the hard wired prototype. It was ok, but just not as dimensional and open as the hard-wired preamp. It sounded boring.

So I then tried a compromise between a PCB and hard-wiring with small stereo boards containing the electronics components and the signal and output wiring all hard-wired.

This was better but the magic was still not there- it was 90% , but that last 10% was what made the magic happen, and the prototype was still audibly superior.

There you go, PCBs reduce Magic by 10%, measurable by ear.

[squadchannel]

tom evans aprooved.

[Analog Kid]

tom evans aprooved.
(Attachment Link)

Those 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?

[Simmed]

i dont understand the brown putty thing

[Analog Kid]

Must be "soundstage adjustment strips" or some such.

[temperance]

Must be "soundstage adjustment strips" or some such.

No, 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.

[Analog Kid]

And why in the world does a preamplifier 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.

[bdunham7]

And why in the world does a preamplifier 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.

The 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...

[coppercone2]

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.

[Kleinstein]

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.

[iMo]

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..

[themadhippy]

The next question is why you need a preamp at all.

source selection and as you say volume control

[Analog Kid]

The next question is why you need a preamp at all.

source selection and as you say volume control

2-pole multi-throw rotary switch, ganged potentiometer and you're done.

[joeqsmith]

And why in the world does a preamplifier 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.

The 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...

I 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/