Jah Tubby preamp mods continued

Calculus wrote: you should really speak to the makers of these pre's about the mods you're making and maybe get them to make a upgraded version with your input... however that would mean they'd have to be humble enough not to take it as a insult to thier work. But if everyone reads this they may not have a choice.

Hahaha,

Mostec on the test bench

Before I publish the audio test ands plots here are some picture from the inside.

Here on the top left of the board is a wire that seems to be soldered but its not if you pull the wire it comes out. On the picture the colors are not true but the wire is still copper color.
One of the first technique you learn when you study electronics is to put solder on the wire before soldering it to anything else. This for two reason - first to avoid oxidation of the copper wich causes false contact and second to ensure solder makes full contact with the wire thus ensuring as less possible solder resistance.
The wire is also not isolated. You can see the shielding coming out between the white and gray part of the wire. If this touches some supply voltage or opamps output...


On this one you see the xover outputs with blocking caps.
So whats wrong? In absolute nothing but as electronician I just can't believe that is the current production. It looks and is constructed like a prototype.
First why can't this cap be on your proffesionnal boards? And by the way why electrolitic caps?
Second why can't you put some heat shrink tube instead of tape that will inevitabely and slowly fall off? Perhaps you sell your pre's too cheap and you're out of money for spending 30pounds for heatgun?



Here on the top middle where the red wire are soldered you can see a nice antenna.
I think its used for listening to Shaka or Rodigan on KISS FM.
Very nice feature for an pre


Why make expensive machine drilled board by profesionnal company and the bend the pin of the cap around it?


Perhaps I'm too demanding but I'v not learned electronic building of this kind.

The owner of this pre gave it to me because he broke one plastic pot. He asked me to put some metal pots and he sayed he was not satisfied with the build quality. I totaly agree. Why sell it so expensive when its so cheap quality?
This kind of building can explain why this unit is so noisy. With all kill switch off you hear the wind blowing thru your speakers - the wires fly around, antenas, flying components,....
The JTS in comparision is dead quiet.
Even worser I approached my laptop PSU accidentaly near the side of the Mostec pre and I heard it thru the speakers. That because of the aluminium casing wich is not as good as steel against EMI/RFI pertubations. JTS use steel like Lincoln.

I'm just talking about the build quality wich is not at level.
But I like the modularized design, the layout and the VU meters

Soon some audio tests

Raspect
Jo

Joseph Redhemption wrote: Tweeter Box - For sure you will hear the difference. Like on your pre turn one of the graphic eq pot from the 12oclock pos to say 3 or 4 oclock and I bet you will hear. DC - Why run a tune on a Garrard? It must be a Swiss Thorens TD124!!! Lol

Whats the joke about those two players?
are they weack?

I only know that shaka is using a Garrard...




Edited by Rico - 30 December 2008 at 8:35pm

bitzo wrote: sorry but.... this only an equalizer with kill switch, I mean it don't have 3 output (bass, mid, high)