ImPasse Preamplifier

[SY]

Back panel mounting is good for me- the transformers I have on hand are not PCB mount. .

 

[luvdunhill]

well, so I'm thinking about doing something crazy... this article was so well-written, that I've perhaps tricked myself into thinking I learned a thing or two.. and like any good teacher, there are just enough nuggets of wisdom to make the inspired (or stupid) student to go out on their own and make their own mistakes and maybe learn a thing or two int he process... so, I'd like to try the D3A version (while we wait for Jack's boards) and was thinking for ease of use, that perhaps a single bottle for the output would be nice. Any recommendations here? Surely one more hint couldn't hurt

 

[jackinnj]

(while we wait for Jack's boards)

As soon as I hear from CineMag I'll be able to send them out.

The Red Light Boards have been delayed as I try to figure out ways to reduce the expense.

 

[luvdunhill]

As soon as I hear from CineMag I'll be able to send them out.

The Red Light Boards have been delayed as I try to figure out ways to reduce the expense.

awesome! What about putting C106,C107 near the heater pins of the 6SN7, as suggested on page 14 of the article?

 

[jackinnj]

I learned a long time ago, that keeping the filaments out of the PCB made life immeasureably easier. These caps are a pair of 10nf/600V ceramics -- so I will provide a pair of vias to which they can be attached -- the filament wiring is up to you

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

 

[jlsem]

Never build a project from a magazine article until the next issue comes out.

What are the actual values of the gate stoppers? The article says 300R while the parts list say 120R. And what does that make R5? Are there any other similar errors?

John

 

[SY]

Wow, nice eye for detail! The real answer is, it doesn't matter. In my prototype, I used 300R. The 120R in the parts list is carried over from a similar set of CCS I built for my phono stage, where I used (for similar reasons, convenience) 120R. Either value will work here- the article states that it's pretty noncritical.

R5 is 300R, but that value is specific to the batch of FETs I had on hand; as I said in the article, that value might have to be adjusted.

 

[jlsem]

I thought that might be the case from reading your other articles and posts. It turns out I have everything for this project on hand except the FETs. I may try it out.

John

 

[luvdunhill]

I thought that might be the case from reading your other articles and posts. It turns out I have everything for this project on hand except the FETs. I may try it out.

John

make sure you don't look at the schematic then, as they are drawn as P-channel MOSFETs

 

[jlsem]

An even sharper eye than mine.

John

 

[jackinnj]

Mouser has the Supertex Depletion MOSFETs -- you want the ones in the TO-220 package.

 

[Andypairo]

Where is possible to get a copy of the AX issue?

Ciao

Andrea

 

[jackinnj]

Where is possible to get a copy of the AX issue?

Ciao

Andrea

http://www.audioxpress.com/

 

[Andypairo]

This is the first place where I looked but they only show the March issue and if I click on the back issues these are available from 2007 or older.

I'd gladly fill a trial subscirption but as it starts from the next issue....

Other options?

Ciao

Andrea

 

[Andypairo]

Hi SY,
would the 6CM7 be up to the task for a "dual mono" (one tube per channel) ImPasse?
1st section is half 6sn7 and second section is beefier (even tough it doen't have the gm of a Ecc88)....

just wondering....

Ciao

Andrea

 

[SY]

It would have a higher source impedance, but still pretty acceptable. I might run that section a bit hotter than in my version, maybe 15mA or so.

The question I'd have is whether the first section is really a 6SN7 or not- since there's no feedback, the linearity is all up to the tube.

 

[luvdunhill]

Hey guys, I'm trying to drum up some interest for a Sowter input transformer group buy. Details here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=139408

 

[wirewiggler]

Funny I was just considering a cinemag group buy, but wanted to wait until I completed my Teres group buy. If you go with cinemags I am in Sowters are a little out of my price range.

Bill

 

[BDP]

I've built many solidstate preamps and amps but no tube stages. In years gone by I actually repaired tube transmitters. Wow that brings back memories.
The AX article has inspired me so I am going to start collecting parts. Hopefully there will be a PCB board group buy. I signed up for the input transformer group buy. Could someone recommend a reliable source for the tubes.

PS: SY We are practically neighbors considering we are out here in the greater Northwest. I'm in the Lewiston, Id/Clarkston, Wa area.

BDP

 

[wirewiggler]

any progress ? I listed wanting a Cinmag with soldered tabs on the group buy but it is dependent on this board layout. Are you planning to a power supply board as well?

Thanks
Bill