His Master's Noise: A Thoroughly Modern Tube Phono Preamp - Page 37

21st April 2010, 12:00 PM
SY On Hiatus Join Date: Oct 2002 Location: Chicagoland	His Master's Noise: A Thoroughly Modern Tube Phono Preamp After more than 25 years of faithful service, it seemed that it might be time to redo my phono system. After all, I like to think that I've picked up a few tricks in the intervening years... The old system consisted of a VPI HW17-II, a Linn Ittok LVII tonearm, and a Troika cartridge. The Troika was... Click here to read the entire article Last edited by Variac; 2nd April 2011 at 12:17 AM.

30th May 2017

mrdave45

diyAudio Member

Back to the hmn...
I'm struggling to find suitable connectors to get between the psu and phono stage.
I obviously want to make sure that the psu can't have exposed pins with HT on them if not connected.
I did find a 5 pole connector that looked OK but as it had a plastic body I couldn't connect protective earth through that. At least that's what it looks like sy did in the pictures.
The 6 pole version isn't stocked any more.
I don't know how I feel about having a 5 pole cord and then a totally separate earth bond wire connected by screw down binding posts. I would use the crimp type connector that looks like an earth tag that goes over the bolt that gets screwed down so it can only come off it the nut comes completely off too.

31st May 2017

kevinkr

diyAudio Moderator

Take a look at the line of CPC connectors at digikey or mouser. I use these up to 400V or so without problems.

"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine

31st May 2017

mrdave45

diyAudio Member

Do you run protective earth through them?

31st May 2017

lehmanhill

diyAudio Member

I ran an 18 gauge stranded through plastic connectors between my separate psu and phono stage on my EO phono stage build. I know that 18 gauge doesn't sound that big in the event of a failure, but it will pass 16 Amps which should be enough to blow the fuse in the event of a failure. 600 V wire, of course.

I agree with kevinkr, there a lots of connector options at digikey, mouser, etc. A lot of the industrial connectors are good for high voltage and reasonably priced.

1st June 2017

mrdave45

diyAudio Member

cheers. In the end i got an ampehnol c16 3 which is really strudy and the female contacts are well recessed with a dedicated protected earth contact which is more prominent so it would lose contact last.
Ended up getting some 7 core rather than 6 core wire. Could find anything suitable that they would sell per meter. I really dont need a reel of it! 16awg and fits the amphenol and the gland on the other end perfectly.
A bit more than i wanted to spend but this is definitely not going to fall apart or get tugged out leaving either one chassis ungrounded or 300+volts on a pin!
Cheers

1st June 2017

mrdave45

diyAudio Member

My next question is about strip board/perf board. I need to construct the HT supply and HT regs old school.

What do people find best/easiest?

1. perf board, which i think it just single pads that you solder connecting wires along,
2. Strip/Varioboard.
3. Groups of three padboard. I usually find myself wishing these were in strips of 4 or 5 holes.

Ive built a few things on strip and groups of three but usually takes a while (more than a while sometimes) to work out how to lay it out.

Do i also need to worry about high voltages on these things? I cant find any voltage ratings on the datasheets.

I did find some nice strip board in maplin a while back which was fibreglass rather than the cardboardy orange stuff and tinned strips.

1st June 2017

lehmanhill

diyAudio Member

I used some group of 5 padboard that I found at Mouser or Farnell. You can see a picture of it in post 223 of the Equal Opportunity MM Pre thread. The regulators are on another of the same board. Happily, the EO doesn't use quite as high a voltage as the HMN, but I was probably pushing it because the gap between pads isn't that big. I did manage to keep unconnected pads between high voltage and ground on the high voltage circuits.

Given the high voltages in the HMN, I might be tempted to use perf board and high voltage insulated wire from point to point.

Jac

2nd June 2017

mrdave45

diyAudio Member

there was a post recently regarding heater voltages. I think more to do with the equal opportunity amp but i want to just check Ive understood correctly.

For the HMN,

One output board will have the heaters connected to 65v and 71.3v giving a diff of 6.3v
and the other output board would have 65v and 58.7v also giving a difference of 6.3v

Presumably the positive 6.3v and negative 6.3v is because thats an easy way to elevate the voltage using the transformer.

If i tried to use 65v+/-3.15 V then they would be floating and i would also have major problems trying to stop my regulators overheating.

Does it matter which pin (4 or 5) gets the 65v?

Im assuming not but for my OCD I sort of want

Board A
pin 5 71.3v
pin 4 65v

Board B
pin 5 65v
pin4 58.7v

2nd June 2017

mrdave45

diyAudio Member

Ive also noticed that the pcbs i have specify C5 and C4 as X2 rated.
Ive had a look at the impasse schematics and boards and there are caps doing the same job under more stress but no mention of X2 ratings in these cases. Do they actually need to be X2 or are the standard wima mkp ok?

I managed to order 1uF 250v by mistake for C5 (just to add to a stack of 1uF 250v mks4s i already had!), i appreciate that this probably does need to be 400v as until the HV regs stabilise there could be more than 250v across it.

I do have some 2.2uF 400v MKP4 and some 0.68uF and 0.33uF 600v multicaps. But tbh the 0.68 is a bit on the large side for the board.

Would either of these do or does it really need to be 1uF?

2nd June 2017

peafarmer

diyAudio Member

I imagine that the schematic you are looking at assumes that a "line" rated capacitor will be used. I know that the F5 power supply specifies it explicitly.