I'm trying to decide on that age old question of what connection to make from seperate PSU chassis to main amplifier chassis. the criteria I decided were essential were:
a) low cost (so no Amphenol connectors)
b) potentially large number of pins (at least 15)
c) locking (so can't get pulled out by accident)
d) at least one connector must safely take 360Vdc (equals 250v AC rating). Possibly the option of two.
e) common part, not likely to become obsolete
first I agonised over one cable or two, and decided one cable would require too high density, be hard to wire, would be expensive, and would be an uncommon part. Amphenol out the window.
next I did the calculations for number of connectors. Since I'm planning for three stages of DHTs and my system is balanced, this is what I found:
* 12 connections for the filaments of 6DHTs.
* earth
* -15vDC for CCS
* one B+ or maybe two.
that's a minimum of 15 connections. So my eye fell on D connectors. Relatively easy to wire up and available in 15 way which is nicely compact. Some are rated at 500v even, so a single 15 way D connector is not impossible.
but while I was happy with the filaments and the -15v supply on D connectors, I would really like better contacts for B+ and earth. My two choices for an added connector were:
a) speakon plugs in 2,4,8 way
b) XLRs
Speakons are cheap in four way but expensive in 8 way, so 4 way remains a possibility. I'm not quite eliminating them but I'm a bit put off by the following:
1) they're bigger and stick out more than XLRs
2) some idiot might plug a speaker into the PSU box
So XLRs. they offer the possibility of using 4,5,6 or 7 way. Now, I spoke to Neutrik about the voltage rating for these, and it's a bit more complex than you think. Some of their paperwork specifies 50v for the whole range, some specify 150v, some specify different voltages for different connectors. The sales guy in the UK quoted me 250vAC for 3-6 way and 125VAC for the 7 way. Not much agreement here, and the unbranded Chinese ones have no voltage rating. In terms of availability the 5 ways are common, 7 quite rare and gets eliminated because won't handle the voltage. Four and six way are more unusual, and six way is much more expensive. Four way can be had in cheap unbranded. So I'm thinking 4 way right now, with the 15 way D connector, because this gives the biggest pins and widest spacing so with unbranded the chances are they're OK for 250vDC, or at least more likely to be than the 5 way.
I hope you've followed all this. So any suggestions? Anything I've left out like BNC for just the B+ (high voltage)? Never used BNC but it's locking at least. Is my above reasoning reasonable? Bright ideas?
Andy
a) low cost (so no Amphenol connectors)
b) potentially large number of pins (at least 15)
c) locking (so can't get pulled out by accident)
d) at least one connector must safely take 360Vdc (equals 250v AC rating). Possibly the option of two.
e) common part, not likely to become obsolete
first I agonised over one cable or two, and decided one cable would require too high density, be hard to wire, would be expensive, and would be an uncommon part. Amphenol out the window.
next I did the calculations for number of connectors. Since I'm planning for three stages of DHTs and my system is balanced, this is what I found:
* 12 connections for the filaments of 6DHTs.
* earth
* -15vDC for CCS
* one B+ or maybe two.
that's a minimum of 15 connections. So my eye fell on D connectors. Relatively easy to wire up and available in 15 way which is nicely compact. Some are rated at 500v even, so a single 15 way D connector is not impossible.
but while I was happy with the filaments and the -15v supply on D connectors, I would really like better contacts for B+ and earth. My two choices for an added connector were:
a) speakon plugs in 2,4,8 way
b) XLRs
Speakons are cheap in four way but expensive in 8 way, so 4 way remains a possibility. I'm not quite eliminating them but I'm a bit put off by the following:
1) they're bigger and stick out more than XLRs
2) some idiot might plug a speaker into the PSU box
So XLRs. they offer the possibility of using 4,5,6 or 7 way. Now, I spoke to Neutrik about the voltage rating for these, and it's a bit more complex than you think. Some of their paperwork specifies 50v for the whole range, some specify 150v, some specify different voltages for different connectors. The sales guy in the UK quoted me 250vAC for 3-6 way and 125VAC for the 7 way. Not much agreement here, and the unbranded Chinese ones have no voltage rating. In terms of availability the 5 ways are common, 7 quite rare and gets eliminated because won't handle the voltage. Four and six way are more unusual, and six way is much more expensive. Four way can be had in cheap unbranded. So I'm thinking 4 way right now, with the 15 way D connector, because this gives the biggest pins and widest spacing so with unbranded the chances are they're OK for 250vDC, or at least more likely to be than the 5 way.
I hope you've followed all this. So any suggestions? Anything I've left out like BNC for just the B+ (high voltage)? Never used BNC but it's locking at least. Is my above reasoning reasonable? Bright ideas?
Andy
Don't ever use an audio-type plug. It's not a matter of if, it's a matter of when someone will accidently plug the wrong thing in. Amphenol connecters at surplus are cheap; I use them exclusively. Jones or Cinch Jones connectors are likewise excellent and widely available from the scrap market.
Don't ever use an audio-type plug. It's not a matter of if, it's a matter of when someone will accidently plug the wrong thing in. >
Hi Sy - do you think that's the case with D connectors and 4,5,6,7 pin XLRs? Surely nobody associates any of those plugs with an amplifier? What on earth would they plug into a 15 way D connector, let alone a 4 pin XLR?
Amphenol connecters at surplus are cheap; I use them exclusively. Jones or Cinch Jones connectors are likewise excellent and widely available from the scrap market.>
Not in the UK, and alas, I'm in London! Andy
Hi Sy - do you think that's the case with D connectors and 4,5,6,7 pin XLRs? Surely nobody associates any of those plugs with an amplifier? What on earth would they plug into a 15 way D connector, let alone a 4 pin XLR?
Amphenol connecters at surplus are cheap; I use them exclusively. Jones or Cinch Jones connectors are likewise excellent and widely available from the scrap market.>
Not in the UK, and alas, I'm in London! Andy
I have Cinch Jones connectors on the umbilical that connects the power supply to my 845SE. There is 1100 volts in that cable. No problems, the amp has lived in South Florida humidity for 3 years. I am using a 18 pin connector. These connectors are still available through some distributors.
The 1100 volt pin is in the corner and the two adjacent pins are not used. Each supply (2 B+, 1 B-, 3 seperate floating DC filament) is completely isolated with a seperate ground lead in the umbilical. The grounds are only joined at the common star on the driver PC board. There a seperate safety ground that connects to the 2 chassis, power cord ground and all other exposed metal. It ties into the signal ground only at the star point. There are two redundant safety ground leads in the umbilical.
This arangement works very well, no hum. I would do it this way again. Put the female connector on the power supply side so there are no exposed pins on the voltage source. I would consider an interlock circuit so that the power supply can't be turned on without the amp connected.
The 1100 volt pin is in the corner and the two adjacent pins are not used. Each supply (2 B+, 1 B-, 3 seperate floating DC filament) is completely isolated with a seperate ground lead in the umbilical. The grounds are only joined at the common star on the driver PC board. There a seperate safety ground that connects to the 2 chassis, power cord ground and all other exposed metal. It ties into the signal ground only at the star point. There are two redundant safety ground leads in the umbilical.
This arangement works very well, no hum. I would do it this way again. Put the female connector on the power supply side so there are no exposed pins on the voltage source. I would consider an interlock circuit so that the power supply can't be turned on without the amp connected.
Thanks guys for the suggestions which I've looked into. the situation in London UK is as follows:
Amphenol - cheapest 14+1 would be £24 for one lead (4 connectors) that's about $45. Too expensive. Looked on ebay in the UK and nothing listed. Shipping from the USA would add significantly to the cost if I bought there. Nice plugs indeed, but doesn't look practical if I needed to make several PSUs and amps. I need to standardise at the outset, and don't want to be dependent on an expensive or unavailable system, and I don't know how many units I'd want in the end. This isn't just for me - I have friends who want stuff.
Molex - I considered this. But what chassis connectors are there, and is it locking? Not clear on this.
I'm still coming back to D connectors for filaments (max 6v, and each tube supplied seperately so low current) and something like a 4 pin XLR for the HT - cheap, locking, universally available.
Bear in mind this needs to be 15 way and that I'm in the UK folks!
I considered crimp - the crimp tools are listed in Farnell at £230 or more - that's nearly $500. Seems a lot of work as well. I've never used this system.
There are non-standard D connectors, in fact, with larger and smaller pins. I'm not familiar with these but maybe I should look again.
Amphenol - cheapest 14+1 would be £24 for one lead (4 connectors) that's about $45. Too expensive. Looked on ebay in the UK and nothing listed. Shipping from the USA would add significantly to the cost if I bought there. Nice plugs indeed, but doesn't look practical if I needed to make several PSUs and amps. I need to standardise at the outset, and don't want to be dependent on an expensive or unavailable system, and I don't know how many units I'd want in the end. This isn't just for me - I have friends who want stuff.
Molex - I considered this. But what chassis connectors are there, and is it locking? Not clear on this.
I'm still coming back to D connectors for filaments (max 6v, and each tube supplied seperately so low current) and something like a 4 pin XLR for the HT - cheap, locking, universally available.
Bear in mind this needs to be 15 way and that I'm in the UK folks!
I considered crimp - the crimp tools are listed in Farnell at £230 or more - that's nearly $500. Seems a lot of work as well. I've never used this system.
There are non-standard D connectors, in fact, with larger and smaller pins. I'm not familiar with these but maybe I should look again.
I've used in the past ITT Cannon connectors, they're great.
For your application, these are the right products.
They're not cheap, but I bought mine (16 pins, cable male + panel female, 700V 4A for each pin) at about 20 Euro / 25 USD.
Ciao,
Giovanni
For your application, these are the right products.
They're not cheap, but I bought mine (16 pins, cable male + panel female, 700V 4A for each pin) at about 20 Euro / 25 USD.
Ciao,
Giovanni
I agree with the Amphenol and ITT Cinch suggestions. The locking-shell circular types are the ultimate (we always called them “circular mil” types). But they are expensive and are fussy with regard to getting all the supporting parts right, the clamps, the insertion tools and making sure you get all the right pin/socket styles, genders and gauges for both ends (all four ends in an umbilical). There are millions of permutations and combinations. I’ve seen junior engineers spend hours and even days specifying these things in military systems. And I’ve watched technicians spend hours and even days wiring them. It won’t be so tough for just 16 wires for audio though.
For a cheaper vintage-style approach, I have used surplus octal sockets and male pin sets (like the bottoms of octal tubes). Find the matching shells to cover the soldered connections on the cables. They aren't locking, but it's pretty hard to pry mine loose anyway, so that’s good enough. (I need a small screw driver to get them loose sometimes). I’ve also found a similar set up using Compactron connectors, all NOS, for pennies. Remember to obey the rule that hot terminals should always be sockets (the female side). In other words, your PS will have female terminals on the chassis connector. The cable will have a male connector to mate with this PS, but a female connector again on the amp side. Then of course male terminals on the amp chassis connector. Makes it harder to zap yourself. If having B+ connected with out heater supplies or vice versa (or a missing negative bias supply – even scarier) could be a problem with a partially engaged connector, or if multiple connectors are used, you can put in a sensing circuit and/or relays for protection. A good locking circular mil connector, however, can be fully trusted.
For a cheaper vintage-style approach, I have used surplus octal sockets and male pin sets (like the bottoms of octal tubes). Find the matching shells to cover the soldered connections on the cables. They aren't locking, but it's pretty hard to pry mine loose anyway, so that’s good enough. (I need a small screw driver to get them loose sometimes). I’ve also found a similar set up using Compactron connectors, all NOS, for pennies. Remember to obey the rule that hot terminals should always be sockets (the female side). In other words, your PS will have female terminals on the chassis connector. The cable will have a male connector to mate with this PS, but a female connector again on the amp side. Then of course male terminals on the amp chassis connector. Makes it harder to zap yourself. If having B+ connected with out heater supplies or vice versa (or a missing negative bias supply – even scarier) could be a problem with a partially engaged connector, or if multiple connectors are used, you can put in a sensing circuit and/or relays for protection. A good locking circular mil connector, however, can be fully trusted.
One thing we've overlooked is that if there are capacitors in the amp chassis, you could get a shock off the male connector at the chassis end.
Using unshrouded connectors would mean having all caps in the PSU and three B+ outputs, input, driver and output. More connections. Speakon connectors are shrouded but only rated 250v.
If we split the umbilical into two connections, the only thing that needs to be in the high voltage connector is the B+. This may offer some solutions - surely there are two way connectors rated for 400v?
Octals would be OK for prototypes but not for the general public. There is a cheap high voltage solution - big of course - which is those big splashproof connectors rated 415v
http://www.rapidonline.com/producti...4=16A+Splashproof+moulded+plug&moduleno=72443
Using unshrouded connectors would mean having all caps in the PSU and three B+ outputs, input, driver and output. More connections. Speakon connectors are shrouded but only rated 250v.
If we split the umbilical into two connections, the only thing that needs to be in the high voltage connector is the B+. This may offer some solutions - surely there are two way connectors rated for 400v?
Octals would be OK for prototypes but not for the general public. There is a cheap high voltage solution - big of course - which is those big splashproof connectors rated 415v
http://www.rapidonline.com/producti...4=16A+Splashproof+moulded+plug&moduleno=72443
Eusebius said:
Good point on the amp-side caps, Eusebius. You could add series diodes inside the amp to prevent back current, or just wait a bit for bleeder resistors to do their jobs; then proceed to disconnect with caution.
"Roger" on octal connectors not being suitable for production - but is that your goal?
Good point on the amp-side caps, Eusebius. You could add series diodes inside the amp to prevent back current, or just wait a bit for bleeder resistors to do their jobs; then proceed to disconnect with caution.>
That's a point - not too keen on diodes but glow tubes are a distinct possibility.
"Roger" on octal connectors not being suitable for production - but is that your goal?>
I get friends asking me to make things, so you have to reckon that once it's out of your hands it could be anywhere. I've seen stuff I made on ebay.
Looked again at splashproof connectors and the four connectors come out total of 22 GBP which is about 40 dollars. That's only 4 ways but rated 415V so that's worth knowing in future.
I suspect there's something in the theatre lighting trade - will look there next.
That's a point - not too keen on diodes but glow tubes are a distinct possibility.
"Roger" on octal connectors not being suitable for production - but is that your goal?>
I get friends asking me to make things, so you have to reckon that once it's out of your hands it could be anywhere. I've seen stuff I made on ebay.
Looked again at splashproof connectors and the four connectors come out total of 22 GBP which is about 40 dollars. That's only 4 ways but rated 415V so that's worth knowing in future.
I suspect there's something in the theatre lighting trade - will look there next.
Eusebius said:
I don't know how you're using glow tubes, but if they are shunt regulators inside the amp, once their voltage decays below the threshold voltage, these tubes will cease conducting and you still could have lethal voltages left on nearby caps. I would always suggest bleeders. They'll drag voltages down to zero - eventually.
We use a lot of the Tyco CPC plastic connectors at work. The prices aren't bad and pins run about 25 cents each. If you're good you won't need to buy an extraction tool 
http://catalog.tycoelectronics.com/...4&P=2335&M=PPROP&BML=&LG=1&I=13&N=1&IDS=27472
http://catalog.tycoelectronics.com/...4&P=2335&M=PPROP&BML=&LG=1&I=13&N=1&IDS=27472
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