[hellomoto]

Thanks ArtemF and Beftus!
 
Could you just describe a little bit more how to differenciate the pins of the power jack, using the multimeter?
 
I also would like to know what would be a good wire setup for the amp: which material, which gauge (inside the amp, not for the link between the amp and the source)? What about that:
http://cgi.ebay.fr/25-22-AWG-Silver-Teflon-Wire-White-red-19-strands-/380230270671?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item58877d7ecf
 
or that:
http://cgi.ebay.fr/50-feet-stranded-28-AWG-Silver-Teflon-Wire-White-Red-/380213369681?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item58867b9b51
 
About the LED, i already bought the ones describe in the BOM from DIYForums, it show how to put it in the PCB, but not how to put it when you haven't a PCB.

Thanks!
 
Antoine

 

[the_equalizer]

 
Quote:

I finally finished my 17EW8 version of this amp last week.  It's been working fine and sounds great.  There is one issue though.  When I turn it on the power supply cycles on and off for several seconds.  It seems to be taking longer and longer each time it is turned on.  The first few times it was turned on only took about 3 or 4 cycles. Last night it took about 30 seconds before the tubes lit up and the PS stopped cycling.  All the voltages are correct according to the schematic.  
 
Is this a big problem and if so what do I do to fix it?  I used the equalizers schematic and parts are exactly as listed.  The PS is a Cisco 48V 380ma version that I got from evilbay.  
 
It's not in its finished case yet so no pics yet. 

That's perfectly normal. When cold, the heaters look like a short circuit to the PSU; which then starts, dumps a bit of current into the heaters and shuts down. It then re-starts, dumps some more current into the heaters and shuts down again.  The tube heaters start increasing their temperature with the current dumps until eventually they no longer look like a short circuit to the PSU which is then able to sustain the required current; so the tubes start glowing and the amp comes on normally.
 
As to the increasing turn on time, I'd monitor it for a few days but 30 seconds is really OK.
 
cheers!

 

[c12mech]

Thanks for the quick reply.  That's what I thought was going on from reading some of the early posts in this thread.  I just was not sure if it would hurt the PSU. 
 
As for the amp itself, it has made a huge difference in the way my DT880's sound.  I can hear peoples conversations in the background during one live performance that I listen to regularly.  I think I'm just going to keep listening to this thing for a while before I decide to upgrade.  I'm thinking Bijou or CK²III, I know they are both completely different animals, but isn't that the fun of diying.  Right now though for the money I don't think the SSMH can be beat.
 

 

[hellomoto]

Double post error, sorry!

 

[wiisus]

Thanks for the pics!  Those are exactly what I needed.

 

[wiisus]

Just wondering, how difficult would it be to add a S/PDIF-in to this?

 

[FallenAngel]

Uhm... it's not a DAC.

 

[the_equalizer]

 
Quote:

Thanks for the quick reply.  That's what I thought was going on from reading some of the early posts in this thread.  I just was not sure if it would hurt the PSU. 
 
As for the amp itself, it has made a huge difference in the way my DT880's sound.  I can hear peoples conversations in the background during one live performance that I listen to regularly.  I think I'm just going to keep listening to this thing for a while before I decide to upgrade.  I'm thinking Bijou or CK²III, I know they are both completely different animals, but isn't that the fun of diying.  Right now though for the money I don't think the SSMH can be beat.
 

Glad to hear you're enjoying it with your Beyers. I agree, for the money, it's a really great little amp.
 
cheers!

 

[c12mech]

I got home tonight and tried to turn on my amp and it does not seem to want to come on.  The PSU cycled for more than 2 minutes and still the tubes did not light up.  I pulled out my dmm and took some measurements.  The PSU reads 48V at the output.  When I plug it into the amp, where I should get 48V I'm getting 5~6V.  At pin 6 on both tubes I get ~3V.  At pin 4 I get 0V. 
 
I checked the grounds and they are good.  Nothing is burned and all the other checks with the meter read good.  I'm at a loss here.  Did both mosfets die at the same time?  They are both isolated from the heat sinks and have heat shrink around all the pins.  It worked fine last night and now nothing.  Any help would be appreciated.
 
Bryant

 

[ArtemF]

It looks like your power supply units do not like the cold heaters. I mean they do not withstand the
initial current. There are two solutions: 1) buy a more powerful PSU. 2) Install a switch (or two switches)
that will allow you first to start one channel, then the second one.
 
 

 

[ArtemF]

add-on - if the mosfets die they can do it in two ways: always open and completely burnt when there's no conductivity at all.
In the second case there will be no load so the PSU voltage will not drop. If we're dealing with the first case then they will
not act as current limiters and the PSU will not be able to feed the heaters with 48V because of high current.
Put 1K resistor instead of one of the heaters so you'll be able to check if the problem is in the
weak PSU that doesn't want to feed two cold heaters.
 
 

 

[Beftus]

Quote:

About the LED, i already bought the ones describe in the BOM from DIYForums, it show how to put it in the PCB, but not how to put it when you haven't a PCB.

Thanks!
 
Antoine

 
Connect the LEDs right after the on/off switch like this: 
http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/705#post_4510827

 

[c12mech]

 
Quote:

add-on - if the mosfets die they can do it in two ways: always open and completely burnt when there's no conductivity at all.
In the second case there will be no load so the PSU voltage will not drop. If we're dealing with the first case then they will
not act as current limiters and the PSU will not be able to feed the heaters with 48V because of high current.
Put 1K resistor instead of one of the heaters so you'll be able to check if the problem is in the
weak PSU that doesn't want to feed two cold heaters.
 
 

I'm thinking it is the PSU.  When I turn it on now it does not cycle.  It still reads 48V with no load but only ~5V with a load.  If I pull out one tube and put in a 1K resistor and it works I'll know that is the problem.  I assume that is what you meant by that.  At that point I'll just add a switch inline to start one and then the other.  If that does not work I may just build a power supply for it that can handle the load. 
 

 

[ArtemF]

that's exactly what I meant. If the PSU can power one channel and if you do the same test for the second channel
(just to make sure they are identical and there are no surprises to expect) then you know for sure that you need
either a more powerful PSU or separate power switches for the channels.

 

[the_equalizer]

 
Quote:

I got home tonight and tried to turn on my amp and it does not seem to want to come on.  The PSU cycled for more than 2 minutes and still the tubes did not light up.  I pulled out my dmm and took some measurements.  The PSU reads 48V at the output.  When I plug it into the amp, where I should get 48V I'm getting 5~6V.  At pin 6 on both tubes I get ~3V.  At pin 4 I get 0V. 
 
I checked the grounds and they are good.  Nothing is burned and all the other checks with the meter read good.  I'm at a loss here.  Did both mosfets die at the same time?  They are both isolated from the heat sinks and have heat shrink around all the pins.  It worked fine last night and now nothing.  Any help would be appreciated.
 
Bryant

 
 
Wow, that's certainly new. I agree with ArtemF's suggestion about inserting a 1K resistor in series with the tube filament. There are 1A Cisco PSU's out there that might help solve your problem, in case it's the PSU.
 
cheers!