DCB1 Build

[omishra]

I am assuming you are asking me to check the resistance across the primary wires (i.e between red and black wires) for finding whether if its open or short. The fuse is fine. I also checked by directly connecting to mains.



I have three wires in the secondary blue-white-blue. Its a 15-0-15 30VA transformer. So I am measuring voltage between the blue wire and the white. I get similar voltage between both the blue-white pairs. I believe all DCB1 builds have sourced the R-Core from the same place.

Sorry, my bad. I did not see you are using 15-0-15. I feel primary needs checked. That connectivity test will reveal something.

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[prasen_b]

Sorry, my bad. I did not see you are using 15-0-15. I feel primary needs checked. That connectivity test will reveal something.

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Ok So I measured the resistance of the primary and secondary windings.

Primary Red-Black ->86 ohms
Primary Red-Green -> Infinity
Primary Black-Green -> Infinity
Secondary Blue-White -> 1.5 ohms
Secondary Blue-Blue -> 3 ohms

So no open or short connections I guess?

 

[omishra]

Ok So I measured the resistance of the primary and secondary windings.

Primary Red-Black ->86 ohms
Primary Red-Green -> Infinity
Primary Black-Green -> Infinity
Secondary Blue-White -> 1.5 ohms
Secondary Blue-Blue -> 3 ohms

So no open or short connections I guess?

Ok, all is well here.
With non power condition, now measure resistance between L and N pins of male adapter, after connecting power cable into IEC socket, it must be 86 ohms. It must return through mains power cable, IEC socket and transformer red black wires.
I found once - one cable segment in new power cable was open always.

Or simply try measure 230V mains on red black wires.

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[prasen_b]

Ok, all is well here.
With non power condition, now measure resistance between L and N pins of male adapter, after connecting power cable into IEC socket, it must be 86 ohms. It must return through mains power cable, IEC socket and transformer red black wires.
I found once - one cable segment in new power cable was open always.

Or simply try measure 230V mains on red black wires.

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My mistake I was measuring DC voltage across the secondaries. I measured the AC voltage yesterday and its around 17.5 volts. I connected the OPS and adjusted the output to 10 volts. The transformer is really silent can't tell if its working or not . Thanks to all who helped.

 

[prasen_b]

After a long time I got some time to change the potentiometer (25K) and resolve the hum issues which was due to some bad solder joints in the interconnects. I am really pleased with the result. A big thank you to omishra and sachin.

I was looking to do some suggested upgrades like the ladder type attenuator from diyfidelity and change the internal signal wiring to a Canare interconnect I bought from audiocraft. Apart from this is there any potential in upgrading the power supply. I would also be interested in any other mods tried out by the members here.

 

[saikatbiswas82]

After a long time I got some time to change the potentiometer (25K) and resolve the hum issues which was due to some bad solder joints in the interconnects. I am really pleased with the result. A big thank you to omishra and sachin.

I was looking to do some suggested upgrades like the ladder type attenuator from diyfidelity and change the internal signal wiring to a Canare interconnect I bought from audiocraft. Apart from this is there any potential in upgrading the power supply. I would also be interested in any other mods tried out by the members here.

Are you using 17.5vac transformer for 10vdc output? The difference of ip vs op dc voltage would be huge and it may produce lot of heat on the regulator ICs. Which in turn may reduce the lifespan of those regulators.

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[omishra]

Are you using 17.5vac transformer for 10vdc output? The difference of ip vs op dc voltage would be huge and it may produce lot of heat on the regulator ICs. Which in turn may reduce the lifespan of those regulators.

Sent from a handheld device. Some typos may creep in

That could be 14V difference with 20mA current. So no more than 0.25W to 0.5W dissipation. Small heatsink will be okay. But for 10V output, 12V transformer is appropriate.

 

[prasen_b]

That could be 14V difference with 20mA current. So no more than 0.25W to 0.5W dissipation. Small heatsink will be okay. But for 10V output, 12V transformer is appropriate.

I was asked to use a 15-0-15 30VA transformer. I believe everyone is using the same Trafo rating for their DCB1 build. The voltage on the secondaries was a bit higher at 17.5 but I will check again.

 

[saikatbiswas82]

That could be 14V difference with 20mA current. So no more than 0.25W to 0.5W dissipation. Small heatsink will be okay. But for 10V output, 12V transformer is appropriate.

I was completely unaware of current consumption for dcb1. Thanks a lot for the information. For that small amount of current, I believe there won't be a heating issue.

Dear @omishra, could you please let me know the functions of the output inductors in your regulated psu? How and where to procure those inductors from?

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[jls001]

One tweak (it's not even a mod) you could easily try: the supply for DCB1 is +/-10V. Using the trim pots on the OPS, you could try different voltages like +/-12V, 12.5, 13, 13.5, 14, 14.5, etc and see if you like the sound of a voltage more than the original 10.

I've not experimented with DCB1 but I'd played around with a similar buffer, and the results were very interesting.

http://www.hifivision.com/diy/63668-bluespower-dual-shunt-regulated-power-supply.html#post714214

It's always great fun to try alternate PSUs. If you have patience, time and inclination try shunt regulated supply.

 

[spirovious]

Powersupply makes lot changes in the sound.Capacitors which I got with powersupply are made by " Samwha". If one uses Elna or Panasonic,sound may improve further.Also voltage of transformer does matter.
For DCB1 even 12-0-12V should be fine as you get around 16+V as DC after rectifier and regulator LM317 needs to convert it to 10-12V. So probably less noise generated. Its is said to have 3V more voltage more than the output voltage(regulated) for better results.

 

[omishra]

I was asked to use a 15-0-15 30VA transformer. I believe everyone is using the same Trafo rating for their DCB1 build. The voltage on the secondaries was a bit higher at 17.5 but I will check again.

You are okay, no need to worry. Continue with that.

Dear @omishra, could you please let me know the functions of the output inductors in your regulated psu? How and where to procure those inductors from?

Sent from a handheld device. Some typos may creep in

These 10mH coils are for low pass filter and with 100uF + 0.1uF and 2 coils you get anything above DC blocked out. You get pure battery like DC. Very much required into phono preamplifier where you amplify 3mV signal. So for low current preamplifier which has its own power capacitors this does not add impedance too. For usage of above 100mA you can replace these by wire jumpers.
They are available on element 14 website. Or mouser.in. sachin can guide more.

Btw there is new version of power supply PCB with separate ground current for each step, AC, bulk capacitors charging-discharging, regulator and filters.

http://s1332.photobucket.com/user/sachu888/media/OPS Rev_zps1nqsemar.jpg.html

 

[saikatbiswas82]

These 10mH coils are for low pass filter and with 100uF + 0.1uF and 2 coils you get anything above DC blocked out. You get pure battery like DC. Very much required into phono preamplifier where you amplify 3mV signal. So for low current preamplifier which has its own power capacitors this does not add impedance too. For usage of above 100mA you can replace these by wire jumpers.
They are available on element 14 website. Or mouser.in. sachin can guide more.

Btw there is new version of power supply PCB with separate ground current for each step, AC, bulk capacitors charging-discharging, regulator and filters.

http://s1332.photobucket.com/user/sachu888/media/OPS Rev_zps1nqsemar.jpg.html

Thanks a lot for the detailed explanation. I'm in process of building some regulated power supply based on lm338t/lt1083 with 2amp or more current requirements. I guess in that case I might not need those output inductors. Correct me if I'm wrong.

I have the older psu kit already. Will look into the newer version as well. Thanks again.

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[omishra]

Thanks a lot for the detailed explanation. I'm in process of building some regulated power supply based on lm338t/lt1083 with 2amp or more current requirements. I guess in that case I might not need those output inductors. Correct me if I'm wrong.

I have the older psu kit already. Will look into the newer version as well. Thanks again.

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For 2A or more, you can bypass those inductors. I won't suggest that PCB also. High current paths must be thick.

 

[Hari Iyer]

Now that the jfet 2sk170BL are practically not available what are the other options for a low noise devices? Also the complentary pair 2SJ074 is extinct.

 

[jls001]

For N-JFET the NXP/Philips Semiconductors' BF862 is as good as the legendary Toshibas.

A nice little preamp built with BF862s:

BF862 Preamp - Page 43 - diyAudio (post#429). Single supply like the original B1.

Available in SMD TO-23 only. No through hole, but if building fresh, a few SMD components shouldn't be too tough to solder.

 

[saikatbiswas82]

Now that the jfet 2sk170BL are practically not available what are the other options for a low noise devices? Also the complentary pair 2SJ074 is extinct.

2sk170/2sj74 matched components are available from diyaudiostore and ebay us.

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[doors666]

For N-JFET the NXP/Philips Semiconductors' BF862 is as good as the legendary Toshibas.

A nice little preamp built with BF862s:

BF862 Preamp - Page 43 - diyAudio (post#429). Single supply like the original B1.

Available in SMD TO-23 only. No through hole, but if building fresh, a few SMD components shouldn't be too tough to solder.

That one is not like b1, that one has gain.
My bumblebee is a like a dcb1 with shunt regulator on a single board. It supports both 2sk170 and bf862.

 

[jls001]

That one is not like b1, that one has gain.
My bumblebee is a like a dcb1 with shunt regulator on a single board. It supports both 2sk170 and bf862.

Neat buffer :thumbsup:

And it's got PS built in. Just add transformer.

Link to schematic please.

 

[doors666]

Neat buffer :thumbsup:

And it's got PS built in. Just add transformer.

Link to schematic please.

Added to the original thread.