• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Grounded Grid Preamp Project And Possible Group PCB Buy

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#142
Well, ok, its an imaging tobe for sure.... Used in floroscopic X-Rays.... about 60,000 US new!! The camera tubes are to the right of the closet in the thingy cabinet......
 

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#144
Yes, I have finally just about accrued all the parts I need to build the fist 6SN7 version. I am using 2- 120 to 220 volt step down transfomrers backwards with voltage doublers and a standard zener chain regulator to end up at 360 volts. I plan on running it at +/- 360 volts as was done in the write up. I think we already know that 200 volts is not going to work well with the 6SN7. I am still mulling over using theTB-28 terminal boards that Parts Connection sells to build up the prototype. These terminal boards are slicker than a you know what.

Mark
 
#146
Mark A. replied to an earlier question: "I think that a header could be done but give us some more definite ideas on that if you can. Are you thinking of a standard edge conector type of header?"
Click to expand...
I was thinking of multi-post headers and plugs until members on another thread were considering a similar issue. The solution was to use LONGER wires to allow manipulation of the board for component switching. Doh! 😱 Am I not smart?...or what? That is so simple it is brilliant, elegant. I wish I had thought of it...but can't claim that. Back to lurking...and stop making things more complicated than they need to be.
 
#148
Well, with the trannys I have I need to make use of a voltage doubler set up so it will all be solid state. I prefer solid state power supplies and so do many other manufacturers. ARC seems to be among the more complicated of the solid state supplies overall. I don't think that with this line stage you'd hear any difference between using solid state or tube though. Solid state is just more convenitne for me and much less expensive and at least in the original grid the zener string doesn't generate any excessive noise that matters at all.
Now if I could locate a couple of small Mercury Vapor rectifiers I'd consider using them just because they are very cool!

Mark
 
#150
GeWa,

Jacco said to just enclose yours with his:bigeyes: ......... now you two have to get together!(Just kidding!). Actually all the remaining insulators(yours included) and some boards will go out on Monday morning come hell or high water. I was going to do this yesterday but the Post Ofice was closed by the time I got back from my service call. Everyone that has not received their insulators should look for them in about a week(or less for some countries like Walters and Al's that seem to have itn all together in customs).

Mark
 
#153
I am building the 6SN7 version hardwired. I will shootout SS UF4007 vs a tidy & sonically superior Mullard EZ80 tube.

I have so many chokes in the power supply inclucing the common rail, I bet I both the Mullard & SS will sound the same, but who knows for sure.
 
#154
With regards to using a PCB or hard wiring, has anyone considered a trackless PCB? This would give the best of both worlds. Easy component placement and orientation, plus it would allow hardwiring the components on the reverse side. Pads could be located for attaching off board components or valve holders.

On a side note, does anyone have an idea how this would compare to the AudioNote M7 kit, which is what I am currently using for a pre amp?
 
#157
I used one of these to build my first grounded grid. It's a bit overkill with the number of turrets. My power supply was built across three 5 tab terminal strips.

An externally hosted image should be here but it was not working when we last tested it.


I retired that one and rebuilt using a pcb and 12AT7s. I used some turrets on this PCB for heater wiring and external conections.

An externally hosted image should be here but it was not working when we last tested it.
 
#160
If you guys are OK with a CCS under the cathode node, you can do the PS a whole lot easier. Most CCS are OK with >10VDC. So, a 450 mA/25.2VAC-$6USD Radio Shack TX and $5 of DN2540N5 MOSFET's will make things a whole lot easier.
Click to expand...

Indeed.... you can then eliminate the entire negative power supply and in my case save another $10.00 to12.00. If you go over to the Trancendent web site and nose around the postings you will find exactly what you mentioned there. The main thing is that no one seems to know what the sound outcome is..... So basically no one has done this yet and compared. Bruce also mentions doing this in the book but also gives reasons for not doing it which don't come immediately to my mind.



Good work on that PCB layout JPS!


Mark
 
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