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eXStatA Build Thread II - Page 32

post #466 of 566

Use this

 

http://www.mouser.com/search/ProductDetail.aspx?qs=2V4k6Hs0nQk9VCKsIWmecw%3D%3D

post #467 of 566


 

Quote:
Originally Posted by ting.mike View Post

Hi,

I've assembled the PSU completely using the parts from the BOM. In initial check up, everything measures up correctly to the values that are specified on the Cavalli website. The only issue I have is setting the bias voltage. The bias voltage maxes at around 535V, and it won't go any higher (trimpots are already making clicking noise). Any idea what's wrong?

 

I'm getting +300V and -300V rails, T1-T2 360mV, T3-T4 410mV, T1 and T3 to ground measures ~330V.

 

I'm using the 369JX Hammon travo, which is the universal version of the 269JX.

 

Thanks.

 

Alex,

can you help me out on this issue? Looking at the schematic of the PSU, the input from the travo is 250-0-250, then after going through the two diodes, is it possible to get the voltage to be higher than 500V on the high bias terminal?

 

If instead I use a 300-0-300 secondary voltage on the travo (I do that by hooking up the primaries on 200V, instead of 230V), then I didn't have any problem getting up to 600V on the high bias terminal. A friend I talked to recommended changing C5 to the mylar type (I think this is what Al used on his built, looking at the pictures he posted) to help get a higher voltage.

post #468 of 566

I just finished my amp this past weekend.  The amp sounds wonderful.  :)

 

DSC_0643.jpg

 

DSC_0629.jpg

 

DSC_0632.jpg

 

DSC_0634.jpg

 

Wachara C.

post #469 of 566

wow..very nice compact build. Kudos!

post #470 of 566

From your comments about sound, I am assuming that the ExStata drives your DIY stats well too. Congratulations, I think you now own the first complete DIY stat rig - headphones and amp , quite an achievement..dB

post #471 of 566
Thread Starter 
Quote:
Originally Posted by ting.mike View Post


 

Quote:
Originally Posted by ting.mike View Post

Hi,

I've assembled the PSU completely using the parts from the BOM. In initial check up, everything measures up correctly to the values that are specified on the Cavalli website. The only issue I have is setting the bias voltage. The bias voltage maxes at around 535V, and it won't go any higher (trimpots are already making clicking noise). Any idea what's wrong?

 

I'm getting +300V and -300V rails, T1-T2 360mV, T3-T4 410mV, T1 and T3 to ground measures ~330V.

 

I'm using the 369JX Hammon travo, which is the universal version of the 269JX.

 

Thanks.

 

Alex,

can you help me out on this issue? Looking at the schematic of the PSU, the input from the travo is 250-0-250, then after going through the two diodes, is it possible to get the voltage to be higher than 500V on the high bias terminal?

 

If instead I use a 300-0-300 secondary voltage on the travo (I do that by hooking up the primaries on 200V, instead of 230V), then I didn't have any problem getting up to 600V on the high bias terminal. A friend I talked to recommended changing C5 to the mylar type (I think this is what Al used on his built, looking at the pictures he posted) to help get a higher voltage.



Are you measuring the voltage at the test point or at the terminal block?

Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #472 of 566

Thanks, Alex. I measured at the testpoints, exactly as instructed on the website:

 

Bias Supplies

Bias voltages are measured at the testpoints NOT at the terminals on the block.

  • Turn on the PS.
  • Measure from either test point to ground. The instant you touch the DMM to the testpoint is the correct voltage. If the DMM lead stays in contact with the testpoint it will pull the voltage down. Therefore, get the measurement at the moment you touch the testpoint.
  • Adjust the associated trimpot to change the voltage, repeating the process of momentarily touching the testpoint until you have the voltage you want.
  • Do the same for the other bias supply.
  • Power down.
  • You're ready to attach the amplifiers.
post #473 of 566
Thread Starter 

OK. Just checking the simplest thing first. Might you kindly post a close up photo of the bias section of the PS both top and bottom of board? If you have already, just send me back to the right post.

Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #474 of 566
Quote:
Originally Posted by dBel84 View Post

From your comments about sound, I am assuming that the ExStata drives your DIY stats well too. Congratulations, I think you now own the first complete DIY stat rig - headphones and amp , quite an achievement..dB


Hi dBel84,

 

Yes, eXStatA drives my DIY headphones well.

 

This isn't my first DIY stats amp.   :)  I've built an all tubes version of stats amp which sounds pretty good too.

 

Wachara C.


Edited by chinsettawong - 2/8/11 at 4:00pm
post #475 of 566



 



ksc5027 datasheet shows 60 pF typical Cob, and a low current hfe <20 in the graph,  I realize the Cob will go down some with the high working Vce but it really is at "game changing" levels compared to the original ksc5042 part 

 

with that much change in output C I'd want to double the output stage current bias to be able to drive both the transistor parasitic C and headphone load

 

Sanyo 2sc3183 has the same low hfe but much lower Cob - and is current production

 

 

if the ksc5027 added Cob is acceptable then why not mosfet fqp2n80 (or 90, or fqpf insulated case) - similar C on the output - looks like a possible "drop in" - but needs to be checked with a fast scope to see if gate stopper R is needed for stability

 

ixys ixtp01n100 is attractive with ~1/2 the added output parasitic C but would need a couple of LEDs in the source lead of the ccs, mirror Qs to overcome the depletion mode negative gate bias - other ixys parts are lower output C but not in TO-220 and harder to get

 

 

plus how many will just prefer the idea of mosfet output vs bjt

 

 

if the "project owners" want to keep the SS version alive then I think they should select/validate a better output Q replacement part

post #476 of 566
Thread Starter 

Yes, agreed. This is one of the reasons that the KSC5042 was chosen in the first place. As the project owner, I don't expect that there will be any more board runs or group buys. This particular design has served its original purpose.

 

A good solution for anyone who can't find the KSC5042 is to use the Sanyo device.

Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
post #477 of 566

i cannot find the 2sc3183, where should i look?

post #478 of 566

bdent, mcmelectronics.

post #479 of 566

Sorry been busy these two days. Here it is:

 

_MG_5117.jpg

_MG_5119.jpg

 

I also need to add that I'm using a 1000V version for the C5 and C7 (couldn't get the 630V version). One diode and one resistor are soldered under the board since there is no space left.

post #480 of 566
Thread Starter 

Thanks. Sorry to ask for more pics, but you take a close up of the bias section on the underside? As close as you can get with focus.

 

The top side looks ok. If I may ask, what is the white thing that goes from one of the pads on D7 toward the resistor?

Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
Reply
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