Faston connectors for speaker output should be easy to find almost anywhere but input terminal with screw connectors for bare wire with 2,5mm lead spacing is very hard to find (produced by German manufacturer Wago, expensive), so you can use ordinary headers. I've seen them in Conrad (Germany) catalogue.
You may realize that we have evolved our own Oz terminology for electronic parts and this confuses people shopping from other cats. Altronics sell them in a few widths and pack sizes:
Altronics - Connectors - Crimp Connectors
Altronics - Connectors - Crimp Connectors
Awesome... Ian, do you have any idea what the pitch is between the pins on the power connectors and speaker outputs? I seem to remember reading somewhere they are 5.08mm which is roughly the value I measured with a steel ruler.
I wonder whether these would fit:
Altronics - H2094 5mm Pitch PCB Mount 6.3mm Spade Pk 10
I wonder whether these would fit:
Altronics - H2094 5mm Pitch PCB Mount 6.3mm Spade Pk 10
'Not certain what you mean there. You certainly found the 5mm pitch type on the following catalogue page and if ESP specified all 6.3mm width terminals, they will all be specified with the same pin pitch. The optional spacing is 9mm and that is obviously unsuitable.
If it is close to 5mm on the board and BOM, that's what you need.
If it is close to 5mm on the board and BOM, that's what you need.
Thanks for the post and hope you can post pictures of your build in progress.
I have Rod board and now accumulating parts .
Have you consider to power the amp with one of the smps power supply from Connexion ?
to the more knowledgeable here, can i power the P3A with dc 23 V+/- ? I have the F5 amp power supply to reuse ?
kp93300
I have Rod board and now accumulating parts .
Have you consider to power the amp with one of the smps power supply from Connexion ?
to the more knowledgeable here, can i power the P3A with dc 23 V+/- ? I have the F5 amp power supply to reuse ?
kp93300
You can power the amplifier from 23V supplies if you wish though power will be limited to around 20W/8R.
More importantly, SMPS supplies are not isolated from mains power until you include an isolation transformer. As such, DIYaudio rules do not allow discussion on that simple but dangerous arrangement.
I think Andrew might be correct. Many motherboards I have seen were mounted on metal spacers and the ground traces were connected to some mounting screw. So that must have gone to the supply 0V and this must have been effectively isolated from the mains. Though I couldn't say if there was a cap between this point and supply earth(?) or elsewhere.
Some computer chassis did give a tingling feeling though not a direct shock ! When the chassis was connected directly to mains earth this problem vanished.
Some computer chassis did give a tingling feeling though not a direct shock ! When the chassis was connected directly to mains earth this problem vanished.
I must admit that I assumed the transformer provided isolation when I used PC and other switchmode supplies for various heavy duty uses in the past. I simply followed published construction notes and didn't get shocked or detect HV. My concern here, is that none of us knows, without schematics and a genuine safety knowledge of the many types of small and very cheap SMPS supplies, what the potential hazards really are.
However, if we plan to dispute the forum rules, this is not the place to debate it.
Here is an extract from Note 2 of the rules. It does not make exceptions for different design variations or the actual isolation status:
"Certain inherently dangerous topics are not allowed. At this time they include but are not limited to: discussing power supplies directly fed by mains current without a transformer, and mucking about in CRT video monitors. Posts and projects are those of individual members of diyAudio. The forum itself is not in the business of vetting projects or posts for safety, accuracy, performance, reliability, function, or fitness for use...."
I take this not to refer to any internal transformer in the SMPS device, but to an external isolation transformer as has been specified in forum posts on previous occasions.
However, if we plan to dispute the forum rules, this is not the place to debate it.
Here is an extract from Note 2 of the rules. It does not make exceptions for different design variations or the actual isolation status:
"Certain inherently dangerous topics are not allowed. At this time they include but are not limited to: discussing power supplies directly fed by mains current without a transformer, and mucking about in CRT video monitors. Posts and projects are those of individual members of diyAudio. The forum itself is not in the business of vetting projects or posts for safety, accuracy, performance, reliability, function, or fitness for use...."
I take this not to refer to any internal transformer in the SMPS device, but to an external isolation transformer as has been specified in forum posts on previous occasions.
There is virtually no difference between the two types of transformers - both afford isolation because the secondary winding(s) are gavanically isolated from the primary.
The danger considered here is the use of an SMPS that probably does not have full galvanic isolation between its mains AC input and its DC output. That is why it's necessary to add an isolation transformer before the SMPS when you can't be certain of the power supply's galvanic isolation.
I'm no authority on electrical safety and I don't want to be seen to engage in prohibited discussion. If you are interested, the web is full of references and more authoritative info. relevant to SMPS running on your local supply. It doesn't take a lot of smarts to conduct a search and read up what you need to know about the supplies and how suspect devices usually have no safety info. either. No surprises there, but there may be when you try something silly with the products.
What the forum is saying is that if you do intend to use direct mains connected SMPSs, keep it to yourself, whatever you may think about the isolation and its safety.
The danger considered here is the use of an SMPS that probably does not have full galvanic isolation between its mains AC input and its DC output. That is why it's necessary to add an isolation transformer before the SMPS when you can't be certain of the power supply's galvanic isolation.
I'm no authority on electrical safety and I don't want to be seen to engage in prohibited discussion. If you are interested, the web is full of references and more authoritative info. relevant to SMPS running on your local supply. It doesn't take a lot of smarts to conduct a search and read up what you need to know about the supplies and how suspect devices usually have no safety info. either. No surprises there, but there may be when you try something silly with the products.
What the forum is saying is that if you do intend to use direct mains connected SMPSs, keep it to yourself, whatever you may think about the isolation and its safety.
Understood. I assumed that all SMPS featured a mains isolation transformer; certainly all the computer power supplies that I've lifted the cover off had one.
I can see why cheap Asian PSU's would omit the transformer to cost but why would any DIYer do so to save a few dollars on a one-off design?
PS: I located the quick disconnect PCB tabs at Farnell and added them to my parts order for my next project: Rod's P88 preamp (with P05B supply board). I ordered this transformer to power the preamp: http://au.element14.com/multicomp/mcfe015-15/transformer-15va-2-x-15v/dp/9531670
Bit late to ask for advice but do you think this is a good match for this application?
I can see why cheap Asian PSU's would omit the transformer to cost but why would any DIYer do so to save a few dollars on a one-off design?
PS: I located the quick disconnect PCB tabs at Farnell and added them to my parts order for my next project: Rod's P88 preamp (with P05B supply board). I ordered this transformer to power the preamp: http://au.element14.com/multicomp/mcfe015-15/transformer-15va-2-x-15v/dp/9531670
Bit late to ask for advice but do you think this is a good match for this application?
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There is a lot of discussion of the merits of using a Hypex SMPS in the VSSA thread, from LazyCat, and from other people who are pretty knowledgeable (or seem that way, to me at least).
It is being promoted even to newbies, so that SMPS at least is fairly safe, I assume. I can't really comment beyond that, but here is a link to one of the posts, and one can just follow from there. Probably a lot to be learned from just reading the posts, It has been brought up several times over three months, with no mention of any safety issues, and no reports of any problems. There are pics, links to a lengthy spec, and information on how to modify the supply for better performance.
http://www.diyaudio.com/forums/vend...-lateral-mosfet-amplifier-63.html#post3406373
I have used a very conventional toroidal transformer (that I already had on hand), and a rectifier/filter for my P3A build. Later I switched to a supply with a better filter, and everything works/sounds just fine.
The P3A build was very straightforward, with no surprises or problems, and everything worked the first time. The P3A circuit does not seem to be all that sensitive to power supply issues, but just like any amplifier, it will benefit from a clean supply with low ripple, and little diode switching noise.
I can post more incl. some pics, but Ian or someone else will have to give me a tip or two on what to avoid. Otherwise my posts will just be "moderated", and aside from upsetting people I like, what fun is that?
I can simply edit out the main part of the board in photoshop, but frankly I am not sure what is OK to post, and what is not... it is hard to discuss component selection while saying nothing about the circuit...
It is being promoted even to newbies, so that SMPS at least is fairly safe, I assume. I can't really comment beyond that, but here is a link to one of the posts, and one can just follow from there. Probably a lot to be learned from just reading the posts, It has been brought up several times over three months, with no mention of any safety issues, and no reports of any problems. There are pics, links to a lengthy spec, and information on how to modify the supply for better performance.
http://www.diyaudio.com/forums/vend...-lateral-mosfet-amplifier-63.html#post3406373
I have used a very conventional toroidal transformer (that I already had on hand), and a rectifier/filter for my P3A build. Later I switched to a supply with a better filter, and everything works/sounds just fine.
The P3A build was very straightforward, with no surprises or problems, and everything worked the first time. The P3A circuit does not seem to be all that sensitive to power supply issues, but just like any amplifier, it will benefit from a clean supply with low ripple, and little diode switching noise.
I can post more incl. some pics, but Ian or someone else will have to give me a tip or two on what to avoid. Otherwise my posts will just be "moderated", and aside from upsetting people I like, what fun is that?
I can simply edit out the main part of the board in photoshop, but frankly I am not sure what is OK to post, and what is not... it is hard to discuss component selection while saying nothing about the circuit...
@Ranchu32:
You can use standard screw terminals with the P3A boards. The spacing of the holes is correct for those, by accident or on purpose, I don't know. See pic of the edge of the board in this post:
P3A w. screw terminals
The hole size on the P3A boards I have will NOT fit a standard press-in type of flat blade tab connector ("Faston") which come with tapered rectangular pins. Not without a little drilling to ream out the hole. The holes look to be around 1.1-1.2 mm diameter, unplated, and you need a bit more than that for a good fit. I mean those tab connectors that are made from mild steel and tinned, and sold as a break-away strip.
Off-line switching power supplies basically come in two topologies, isolated and non-isolated. The main point of the transformer in "isolated" offline switchers is that the turns ratio can be used as a convenient means to change the output voltage. Presence or absence of a transformer in an off-line switching supply is not an indication of how safe the user may be, although electrical isolation can be a benefit for other reasons besides letting the turns ratio do some of the work. (long way of saying that Ian is correct).
Cheap switching power supplies are not exclusively Asian, we have been making cheap $h-t like that (and throwing it away every few months) since well before Asian manufacturers, and have nobody else to blame.
An off-line supply can be made as safe as anything, depending on what the manufacturer decides, so one would hope that the Hypex are in the "safe" category, because they are being sold to hobbyists.
Here is a link to an old article about switchers and some of their foibles, from TI (remarkably readable):
Off Line SMPS Failure Modes
You can use standard screw terminals with the P3A boards. The spacing of the holes is correct for those, by accident or on purpose, I don't know. See pic of the edge of the board in this post:
P3A w. screw terminals
The hole size on the P3A boards I have will NOT fit a standard press-in type of flat blade tab connector ("Faston") which come with tapered rectangular pins. Not without a little drilling to ream out the hole. The holes look to be around 1.1-1.2 mm diameter, unplated, and you need a bit more than that for a good fit. I mean those tab connectors that are made from mild steel and tinned, and sold as a break-away strip.
With respect, that is not quite right. This an excellent example of "We have met the enemy, and he is... us".
Off-line switching power supplies basically come in two topologies, isolated and non-isolated. The main point of the transformer in "isolated" offline switchers is that the turns ratio can be used as a convenient means to change the output voltage. Presence or absence of a transformer in an off-line switching supply is not an indication of how safe the user may be, although electrical isolation can be a benefit for other reasons besides letting the turns ratio do some of the work. (long way of saying that Ian is correct).
Cheap switching power supplies are not exclusively Asian, we have been making cheap $h-t like that (and throwing it away every few months) since well before Asian manufacturers, and have nobody else to blame.
An off-line supply can be made as safe as anything, depending on what the manufacturer decides, so one would hope that the Hypex are in the "safe" category, because they are being sold to hobbyists.
Here is a link to an old article about switchers and some of their foibles, from TI (remarkably readable):
Off Line SMPS Failure Modes
PMI,
Thanks very much for your advice and photograph showing the mounting of the screw tabs.
I took my populated PCB into Jaycar earlier this week to see if their two terminal screw blocks would fit - the pitch was correct however no way there was enough clearance to fit six of them in the power input section (I haven't cut my board in half like you have).
I didn't even think to try 2x three pin blocks rotated 90 degrees as you have done.
Thanks very much for your advice and photograph showing the mounting of the screw tabs.
I took my populated PCB into Jaycar earlier this week to see if their two terminal screw blocks would fit - the pitch was correct however no way there was enough clearance to fit six of them in the power input section (I haven't cut my board in half like you have).
I didn't even think to try 2x three pin blocks rotated 90 degrees as you have done.
Thanks for your input PMI, it highlights what I think is the real problem for implementing SMPS sytems and many other potentially good ideas that are fine when left in the hands of professionals. In my view, Lazy Cat should have considered the safety of his likely newb audience and the spirit of the rules before making that post. Remember, the forum does not propose to vet the safety merits of posts - it should have been reported by aware readers.
Whilst I agree that it may be a good idea for commercial products or very experienced DIYs and professionals to implement SMPSs, take a look at the data sheet attached for the Hypex supply. Is anyone considering the need to securely cover it and protect you or other service persons from ever coming in contact with the live circuits? I don't see any attention drawn to this in the recommendation. Not smart at all!
A typical "design" process goes like this:
A clever dude says "I have used product X in this application and it works fine, no problem or danger.''
An engineer chips in saying "Yes, using this or that qualified product is safe in that application and everyone can use one with confidence".
A newb reads this as anything that looks similar to that qualified product in pics on Ebay will be safe in their applications too.
'Removes lid, tries to alter voltage or whatever to suit requirements or just to see what gives.
Bang - dead - no insurance cover. So sad!
A newb or audio amateur has no clue how SMPS works, how feedback circuits are necessary for regulation but break the isolation between circuits or how failure modes can place large potentials on an interstage transformer's secondary windings. The warnings are not just an out for insurance claims - there have a couple of deaths and many serious shocks recieved by techs and amateurs in my local region over the 20 years I've been here. All have been due to non-isolated supplies like old live chassis TV and SMPS - mostly by inexperience or indiscipline to provide proper isolation.
Whilst I agree that it may be a good idea for commercial products or very experienced DIYs and professionals to implement SMPSs, take a look at the data sheet attached for the Hypex supply. Is anyone considering the need to securely cover it and protect you or other service persons from ever coming in contact with the live circuits? I don't see any attention drawn to this in the recommendation. Not smart at all!
A typical "design" process goes like this:
A clever dude says "I have used product X in this application and it works fine, no problem or danger.''
An engineer chips in saying "Yes, using this or that qualified product is safe in that application and everyone can use one with confidence".
A newb reads this as anything that looks similar to that qualified product in pics on Ebay will be safe in their applications too.
'Removes lid, tries to alter voltage or whatever to suit requirements or just to see what gives.
Bang - dead - no insurance cover. So sad!
A newb or audio amateur has no clue how SMPS works, how feedback circuits are necessary for regulation but break the isolation between circuits or how failure modes can place large potentials on an interstage transformer's secondary windings. The warnings are not just an out for insurance claims - there have a couple of deaths and many serious shocks recieved by techs and amateurs in my local region over the 20 years I've been here. All have been due to non-isolated supplies like old live chassis TV and SMPS - mostly by inexperience or indiscipline to provide proper isolation.
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'No harm in showing simple pics. Rod E. does this on his own site but could I suggest simply not showing the traces in silhouette. Given enough pics, anyone can replicate the layout and circuit of a 1 or 2 layer PCB but making it painfully simple in one take with the traces of a single sided board like this one is, I think, just too obvious......I can post more incl. some pics, but Ian or someone else will have to give me a tip or two on what to avoid. Otherwise my posts will just be "moderated", and aside from upsetting people I like, what fun is that?
I can simply edit out the main part of the board in photoshop, but frankly I am not sure what is OK to post, and what is not... it is hard to discuss component selection while saying nothing about the circuit...
Sorry to any who feel discouraged by what I had said about Ranchu's pics. Could I suggest though, that simply not using backlighting will remove most justifiable concerns. Please continue; show everyone what you wish with just a little forethought so we all benefit from sharing.
There is a generalised circuit diagram on the ESP site which is likely fine for reference. Rod has requested that members link to the site and not post copyright material from the site. That's easy really but I guess anything more than a mouseclick will be too hard for some. Too bad for them.
Thanks for your input PMI, it highlights what I think is the real problem for implementing SMPS sytems and many other potentially good ideas that are fine when left in the hands of professionals. In my view, Lazy Cat should have considered the safety of his likely newb audience and the spirit of the rules before making that post. Remember, the forum does not propose to vet the safety merits of posts - it should have been reported by aware readers.
Whilst I agree that it may be a good idea for commercial products or very experienced DIYs and professionals to implement SMPSs, take a look at the data sheet attached for the Hypex supply. Is anyone considering the need to securely cover it and protect you or other service persons from ever coming in contact with the live circuits? I don't see any attention drawn to this in the recommendation. Not smart at all!
A typical "design" process goes like this:
A clever dude says "I have used product X in this application and it works fine, no problem or danger.''
An engineer chips in saying "Yes, using this or that qualified product is safe in that application and everyone can use one with confidence".
A newb reads this as anything that looks similar to that qualified product in pics on Ebay will be safe in their applications too.
'Removes lid, tries to alter voltage or whatever to suit requirements or just to see what gives.
Bang - dead - no insurance cover. So sad!
A newb or audio amateur has no clue how SMPS works, how feedback circuits are necessary for regulation but break the isolation between circuits or how failure modes can place large potentials on an interstage transformer's secondary windings. The warnings are not just an out for insurance claims - there have a couple of deaths and many serious shocks recieved by techs and amateurs in my local region over the 20 years I've been here. All have been due to non-isolated supplies like old live chassis TV and SMPS - mostly by inexperience or indiscipline to provide proper isolation.
That is why I encouraged PMI to design pcb for Mr. Evil's capacitance multiplier for higher power use with PeeCeeBee (TH version of VSSA) and other symmetrical CFB circuits like Ovation nx (up to 40V rails). I know that SMPS can sound excellent if designed and manufactured in proper way (UK high end manufacturer Chord is using them for 20+ years) but I still do not feel comfortable with the way Hypex or Connex SMPS modules are executed for diy use. Also, their reliability is not that good, and the prices are not that low. I think linear PSU is still the safe bet. One thing to remember is that HF air borne interference is always real possibility with SMPS.
If the intention is to sell as much amp modules as possible, than it is much easier to suggest to buyers where to find ready made SMPS modules than to help them all to build noiseless linear PSUs. For Lazy Cat it is much easier to presume that Hypex SMPS modules are safe for diy users, than to prove it. After all they are claimed to be safe, but are they?
Hi PMI, IAN and ivanlukic
many thnaks for the helpful pictures.
i take heed of the warning about saftey issues with smps.
I am also careful about transformer based linear supplies also
BTW can i use BC550c in place of the BC546 if i intend on powering the board with a about +/- 30V dc ?
cheers
kp93300
many thnaks for the helpful pictures.
i take heed of the warning about saftey issues with smps.
I am also careful about transformer based linear supplies also
BTW can i use BC550c in place of the BC546 if i intend on powering the board with a about +/- 30V dc ?
cheers
kp93300
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