Ok, got my boards and trying to layout my chassis.
I want to leave space for a stepped attenuator and put some passdy pearl2 phono boards in later.
I think i can put the selector (i have extenders) and the attenuator on the left and stack the pearl boards in the middle.
However i am rather concerned about having ~350v ac lines near boards that have input signals near something thats taking in 0.5mV and general interference from the transformers in general. I could probably put a sheet of metal between the transformers and the pearl boards though.
Any suggestions regarding layout, this is the best ive come up with so far. Its the 300m deep 3u pesante from hifi 2000.
https://onedrive.live.com/redir?res...authkey=!AIiL35ts_VmR5yE&v=3&ithint=photo,JPG
The rca inputs will be on the back panel rather than where they are currently lined up, that was jsut to see how far along they would go.
Cheers
I want to leave space for a stepped attenuator and put some passdy pearl2 phono boards in later.
I think i can put the selector (i have extenders) and the attenuator on the left and stack the pearl boards in the middle.
However i am rather concerned about having ~350v ac lines near boards that have input signals near something thats taking in 0.5mV and general interference from the transformers in general. I could probably put a sheet of metal between the transformers and the pearl boards though.
Any suggestions regarding layout, this is the best ive come up with so far. Its the 300m deep 3u pesante from hifi 2000.
https://onedrive.live.com/redir?res...authkey=!AIiL35ts_VmR5yE&v=3&ithint=photo,JPG
The rca inputs will be on the back panel rather than where they are currently lined up, that was jsut to see how far along they would go.
Cheers
Twist the AC leads as tightly as you can. Try to route them against the chassis, preferably into corners. A shield can indeed be a very good idea.
Thanks sy,
I've got a load of hgc silver hookup wire from hifi collective with the supplied insulation, supposedly 10.5kv dielectric. Does that mean it's ok for the high tension supply or does dielectric rating mean something else. I bought it for all the line inputs but need something for the psu to preamp. I bought some of their mains hookup rated to 600v buts it's slightly too thick for the through holes.
I'm intending on the line inputs being unsheilded. The Seiden selector has contacts between the input contacts. I'm guessing I should connect those to ground?
I've got a load of hgc silver hookup wire from hifi collective with the supplied insulation, supposedly 10.5kv dielectric. Does that mean it's ok for the high tension supply or does dielectric rating mean something else. I bought it for all the line inputs but need something for the psu to preamp. I bought some of their mains hookup rated to 600v buts it's slightly too thick for the through holes.
I'm intending on the line inputs being unsheilded. The Seiden selector has contacts between the input contacts. I'm guessing I should connect those to ground?
Yes, and expensive. The problem is finding any bit of wire kicking about that has suitable insulation. So a short run (a few cm) even of expensive wire is still way cheaper than buying a 1m length plus postage.
Also, what's the best thing to do with all the extra wires from the transformer. There's loads of taps on the primary. I was thinking cut them shortish. Put heat shrink and tape then tie them together and stuff them round the back.
Impasse proposed wiring
http://cinemag.biz/line_input/PDF/CMLI-15-15PCA.pdf
My proposed wiring.
https://onedrive.live.com/redir?res...authkey=!AFDVFtUJRVFJTsA&v=3&ithint=photo,jpg
Hi, am just a bout good to wire everythign up. Have done all the chassis work but need to check a couple of things.
I have 3 grounds on the cinemag. Pin 2, 7 and 6.
Should 2 (the input shield) be connected to the rac ground on input?
Pin 7 (metal can) go directly to chassis star ground?
Pin 6 (output shield) be shorted to Pin 5 (output audio cold signal) via those though hole on the audio board?
What should i do with the input cold signal (would be xlr pin 3) Im guessing that should be connected to input ground.
Output.
Should i leave the output xlr ground isolated from the chassis. The audio ground to chassis is already taken care of at the psu via those diodes and capacitor.
Psu...
Do i need the thermistor between the primary windings? I probably dont as theres barely any capacitance in the psu.
~200mA fuse? (Im on 240v)
Afer the fused PEM, i want to run live to a power switch on the front panel. Would i twist the return length going to the transformer with this?
Also twist the 0v 120v secondary wires in pairs eg 2x (0v/120V).
Is it ok to use a wima X2 275~ 0.01uF as a bounce supression cap?
Have i done anything wrong/dangerous/stupid?
I know i should idealy run power etc round the edges but as the connections are right next to each other it made sense to go direct.
Cheers
D
http://cinemag.biz/line_input/PDF/CMLI-15-15PCA.pdf
My proposed wiring.
https://onedrive.live.com/redir?res...authkey=!AFDVFtUJRVFJTsA&v=3&ithint=photo,jpg
Hi, am just a bout good to wire everythign up. Have done all the chassis work but need to check a couple of things.
I have 3 grounds on the cinemag. Pin 2, 7 and 6.
Should 2 (the input shield) be connected to the rac ground on input?
Pin 7 (metal can) go directly to chassis star ground?
Pin 6 (output shield) be shorted to Pin 5 (output audio cold signal) via those though hole on the audio board?
What should i do with the input cold signal (would be xlr pin 3) Im guessing that should be connected to input ground.
Output.
Should i leave the output xlr ground isolated from the chassis. The audio ground to chassis is already taken care of at the psu via those diodes and capacitor.
Psu...
Do i need the thermistor between the primary windings? I probably dont as theres barely any capacitance in the psu.
~200mA fuse? (Im on 240v)
Afer the fused PEM, i want to run live to a power switch on the front panel. Would i twist the return length going to the transformer with this?
Also twist the 0v 120v secondary wires in pairs eg 2x (0v/120V).
Is it ok to use a wima X2 275~ 0.01uF as a bounce supression cap?
Have i done anything wrong/dangerous/stupid?
I know i should idealy run power etc round the edges but as the connections are right next to each other it made sense to go direct.
Cheers
D
MrDave45, where did you buy the Cinemag transformers ? I've been looking for a source in the UK but haven't found any yet.
i got them as an option with the tech diy kit. It maybe worth looking at sowter, jensen tx also canford audio often have input transformers in. Although they maybe mic transformers. (luhndahl)
Can to chassis ground, input shield to input ground (i.e., the outer conductor of the RCA jack or XLR pin 1, depending on whether your source is balanced or single ended), secondary shield to circuit input ground (i.e., the tail end of the grid and cathode resistors of the first stage).
Cinemag are made to order, take about 4 to 6 weeks. You may be better off using Sowter over there -- very high quality indeed.
Katie and dad. You may have to adjust the input resistor value to suit the sowters output impedance.
Did anyone mange to view the picture I posted regarding my wiring schema? Not sure if it's viewable. I don't seem to be able to get my pics to automatically view.
Thanks for the confirmation of the input transformer sy.
Did anyone mange to view the picture I posted regarding my wiring schema? Not sure if it's viewable. I don't seem to be able to get my pics to automatically view.
Thanks for the confirmation of the input transformer sy.
Finshed impasse build
Finished it!
Minor hitch in the fact that somehow i had put my 6sn7 socket aligned 1 rotation ccw. I remember checking that several times when i soldered it in originally and im not sure how i got that wrong. Luckily it didnt break anything but i should measure the pin voltages before installing the pins next time! First tube build and nervous about plugging in high voltage circuits with bits missing.
Anyway, my layout has no hum even without a shield installed. The wring scheme was also correct (although anyone using this should satisfy themselves that this is indeed the case, I cant be responsible if you decide to follow this, i cant even get the orientation of a tube socket right).
Hooray, i didnt die!
Heres some pictures of the build. You may have to right click and open in another tab.
A big thanks you to all who helped me with this.
Jackinnj for the splendid kit,
Sy for the original design (i think) and his useful comments.
Anyone else too!
My F4 has come to life but its now seriously showing my speakers up. Thats propbably the next project.
D
Finished it!
Minor hitch in the fact that somehow i had put my 6sn7 socket aligned 1 rotation ccw. I remember checking that several times when i soldered it in originally and im not sure how i got that wrong. Luckily it didnt break anything but i should measure the pin voltages before installing the pins next time! First tube build and nervous about plugging in high voltage circuits with bits missing.
Anyway, my layout has no hum even without a shield installed. The wring scheme was also correct (although anyone using this should satisfy themselves that this is indeed the case, I cant be responsible if you decide to follow this, i cant even get the orientation of a tube socket right).
Hooray, i didnt die!
Heres some pictures of the build. You may have to right click and open in another tab.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
A big thanks you to all who helped me with this.
Jackinnj for the splendid kit,
Sy for the original design (i think) and his useful comments.
Anyone else too!
My F4 has come to life but its now seriously showing my speakers up. Thats propbably the next project.
D
Last edited:
ive found out why one drive pictures dont automatically load. Theyre using dynamic links which keep changing. Oh well. Ill look into an alternative.
Beautiful work, Dave! It looks considerably better than mine.
K+D, you can use a higher load impedance, but you'll want to add a Zobel to optimize transient response. That's easily checked with a square wave and a scope to determine the optimum values for that transformer.
K+D, you can use a higher load impedance, but you'll want to add a Zobel to optimize transient response. That's easily checked with a square wave and a scope to determine the optimum values for that transformer.