Building a symmetrical PSU B1 buffer

parodielin · 2011-04-15 8:20 pm

Salas said:
Don't guess, fix the wires secure and use your DMM in resistance mode to check there is GND continuity (near zero Ohm) on all wired stuff for any pot setting.

I saw three "Ground" positions on the board - one at the center of the V+ and V- and the other two at the center of Input and Output. Did I miss anyone else?

Salas · 2011-04-15 8:23 pm

Those spots will do. Check there is still continuity between those 3 spots after assembly, using the iron etc.

parodielin · 2011-04-15 8:33 pm

Salas said:
Those spots will do. Check there is still continuity between those 3 spots after assembly, using the iron etc.

I haven't re-solder the wires to the board yet. But for now, it is zero on three grounds across different volume pot settings. When it's powered, the output shows .002 (Direct current mode set to 2m) on both sides w/ volume turns to maximum. Does .002 mean 0.002 mA?

I'm letting it run without hooking up to any other machine. Right now the reading are .003 ~ .005.

Salas · 2011-04-15 8:45 pm

Direct Voltage mode 0.002 when set to Volts range is 2mV. Direct current mode is when using the DMM in series with a broken circuit so to see the amount of current travelling.

parodielin · 2011-04-15 8:54 pm

Salas said:
Direct Voltage mode 0.002 when set to Volts range is 2mV. Direct current mode is when using the DMM in series with a broken circuit so to see the amount of current travelling.

That helps. I recheck the vdc:

R: 1.5 mV
L: 2.1 mV

These value are taken after the system is on, not connecting to anything, for a while. These readings don't seem to change when I adjust both volume pot settings.

I guess now I feel much better to put it back to the chain. The Emotiva is on the way back to the factory. I still have the ClassDAudio amp or a Lepai Tripath TA2020 ($20) amp that I can test. I'll find a few cheap desktop speakers.

Salas · 2011-04-15 9:09 pm

Better safe than sorry. Though nobody not having done expert investigation with instruments on site can guarantee there is no other weird issue with the Emotiva when driven from DC coupled 220R source impedance, a successful test on another amp will build confidence to take your risks. At least hook up a dinky speaker or a cheap RadioShack spare mini woofer driver on the Emotiva not to kill good speakers if you dare a new test and the same bad stuff occurs again for some weird reason. Be sure no RCA centre pin was/is mixed with ground.

parodielin · 2011-04-15 9:55 pm

Salas said:
Better safe than sorry. Though nobody not having done expert investigation with instruments on site can guarantee there is no other weird issue with the Emotiva when driven from DC coupled 220R source impedance, a successful test on another amp will build confidence to take your risks. At least hook up a dinky speaker or a cheap RadioShack spare mini woofer driver on the Emotiva not to kill good speakers if you dare a new test and the same bad stuff occurs again for some weird reason. Be sure no RCA centre pin was/is mixed with ground.

Just soldered the wires directly to the PCB. All measurements are consistent. I start to think I might be ready to go.

Is the DC offset different on the Left and Right normal?

Also, I'm actually thinking about building a F5. Would Burning Amp 2 a better or less risky when using with the DCB1?

Salas · 2011-04-15 10:00 pm

Go on the $20 amp and PC speakers first.

Emotiva, I never heard of it if the fire squad calls around.

About Pass, I built no amps of those series, although I have examined and listened to F5, I had messed with a couple of Zens back old, better others reply.

parodielin · 2011-04-15 10:05 pm

Salas said:
Go on the $20 amp and PC speakers first. Emotiva, I never heard of it if the fire squad calls around. About Pass, I built no amps of those series, although I have examined and listened to F5, I had messed with a couple of Zens back old, better others reply.

Of course, the Lepai Class T will be the first one and I won't hook up with my Scanspeak Revelators or Raal Ribbon yet.

The freight cost for Emotiva was $34 back to the factory. So it's not so bad. It is the weight (89 lbs) that almost kills me.

I am letting the DCB1 burn in right now. My B1 is a hum city without a metal enclosure. Would DCB1 "survive" without metal enclosure?

Salas · 2011-04-15 10:38 pm

Grounding issues you got most probably. X1 gain is not prone to obvious hum even naked, its not a X1000 phono stage.

parodielin · 2011-04-16 12:27 am

Salas said:
Grounding issues you got most probably. X1 gain is not prone to obvious hum even naked, its not a X1000 phono stage.

Salas,

It's working! Should have been more careful the first time that would save me two tweeters and one Emotiva trip. The DC offset is consistently around 1.5-2.2mV on both channels.

It's driving the Lepai Class T amp. This little guy is quite good for it's price. I connected to two 6 ohm Mission speakers. It is no hum when running naked, well, in a cardboard box.

Now I want to add LightSpeed to it.

Thanks a lot!

Salas · 2011-04-16 12:30 am

parodielin · 2011-04-16 12:43 am

Salas said:

With the LightSpeed, it needs a 5vdc. Uriah said I can use the 10 vdc from the DCB1. Just to make sure I know how to connect it, should I connect the V+ to the regulator + (from 10 vdc to 5 vdc) and the G to the regulator -?

Salas · 2011-04-16 12:51 am

G to GND, not reg-. Else smoke.

I presume, check with Uriah.

parodielin · 2011-04-16 4:10 am

Salas said:
G to GND, not reg-. Else smoke. I presume, check with Uriah.

Yes, G to GND. I will use the Alpha 25K mono pots before building the LightSpeed. I soldered all LDRs tonight. I'm not sure if my soldering skill is good enough to do "Solder LDRs with care". I am ordering another 20K stereo pot just in case...

Going to vacation next week. Hopefully, when I'm back, I have "enough confidence" to put DCB1 into expensive speakers.

parodielin · 2011-04-16 5:43 pm

Fuses and IEC Power Jack

I plan to use this IEC Power Jack:

IEC Power Jack Chassis Mount with 10A Fuse Holder

It comes with a fuse holder. The BOM says 750mA T Slow for 115V.

Would this fuse (800mA) work?

Littelfuse 800mA GDC Type 5 x 20mm Slo-Blo Fuse 5 Pcs.

Or should I pick 600mA? Couldn't find 750mA over PE.

Would this switch work?

SPST Round Rocker Switch w/Red Illumination 12VDC

Thanks. I am now being very careful and re-evaluate what I thought I knew...

Marra · 2011-04-16 5:55 pm

Surely you'll need a mains switch not one rated at 12 volts?

parodielin · 2011-04-17 1:22 am

Marra said:
Surely you'll need a mains switch not one rated at 12 volts?

What parameters should I be looking for a mains switch? Like 250 VAC?

Would the 800 mA fuse work?

william2001 · 2011-04-17 2:04 am

I would guess this switch is the one you want: SPST Round Rocker Switch w/Red Illumination 125VAC

I like the large DPDT switches myself (I use the 060-310). Bit of a pain to cut the hole though. The fuses you found should be OK.

AndrewT · 2011-04-17 12:41 pm

william2001 said:
I ....guess.....SPST Round Rocker Switch w/Red Illumination 125VAC

I like the large DPDT switches myself

stop guessing.
In some Countries that Single Pole switch is not allowed as the mains switch.
It is only 125Vac.

Building a symmetrical PSU B1 buffer

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