[analogmart]

The Discreet stage can also be made to output +-15 voltage but you would require to change the 180 ohm resistor to a lower value like 50 to 100ohms.

Hi Nick,
From your suggestion in the past, I trimmed blue pot on PCB and got around 14.9 V +/- stable.
Yes, I waited about 30 minutes and repeated measuring a result. Nothing was wrong since that day 
(I'm not sure, may be I live in 220V. country)

Do I still need to change resistor as your recommended or just change a resistor
with return blue pot to 12V. position?

Hi dexsam,
Which capacitors I need to change for dealing with Burson and what's value that they recommend?

Funny part start again....BTW, my burson is the old version, like Tan uses.

Regards,
Mart
 

[PromitheusAudio]

Mart
If you can get 14.9Volts stable then you don't have to change the resistor.
how much the regulator can regulate depends on your mains voltage
here in my office we are 205volts, and at home 220volts. Malaysia specs their voltage at 240voltages

the burson really looks much different that what i have. Can't comment how it would effect our boards

also from what i did to help out a local customer we bought the fame 10nF MKP Roderstein stuff and bypass across +v supply to ground, -v supply to ground and +V supply to -Vsupply. Really improves the burson quite a far bit. ITs hard to solder them though

[tanchiro58]

also from what i did to help out a local customer we bought the fame 10nF MKP Roderstein stuff and bypass across +v supply to ground, -v supply to ground and +V supply to -Vsupply. Really improves the burson quite a far bit. ITs hard to solder them though

Nick,

Are they little square turquoise blue colors (Vishay 1837 MKPs?)? They are exceptionally excellent to bypass the Burson Discrete opamps and sound good too. I got the stable voltage between 11.30 to 12.30 VDC (pin4 and pin7 regarding to ground 0VDC) as you told me to adjust the other days but the Burson run warm would that be normal?

Analomart,

Do your Burson run warm or hot? In Fountain Valley (Southern California-USA) I always have 118-120V.

Many thanks,
Tan

[Dexsam]

Burson's Mr Jack advises me to flip over the discrete op amps so that the heat trapped under the pcb can dissipate easily.  So I did exactly that and the Burson discretes now sit the right side up (see photo) and everything else remain the same.


I realised Nic's double stage regulator could not raise the voltage beyond the 13.8V level.

On the output dc offset, Nic explanation is plausible and I only wish I could adjust it.  BTW your figure of 20mV to 80mV should be positive or negative or doesn't matter?  Trouble is, I am getting in the region of 500mV and I am afraid the constant magnetising of the transformer core will affect the sound.  The bursons have no provision for offset null as in normal IC op amps since pins 1 and 5 are not used. So how do we adjust the offset then?  By adjusting the V+ and V- supplies to do the balancing act?

On bypass caps, bursons recomend from 0.1 to 1uF, I used 0.1uF.  Nic says 10nF MKP which is 0.01uF and they sound very good according to him.  Where can I buy those 10nF MKP?

Some of you have different (earlier) Bursons - I cant imagine, can you post the photo?  Thanks

[PromitheusAudio]

The offset does not matter whether positive or negative but if its 500mv then its way too high and like you say it would magnetize the core. You might want to fix this quickly. I believe the heat is cause because of the high offset driving the core. and would damage the burson if this continues. The transformer would probably take a longer time to be magnetize. As there is an airgap
You have pretty much isolate the burson from our board except for the loading/gain resistors and have even done a separate power supply.
Is the offset postive or negative? if its negative you would want to increase the positive voltage to offset it and vice versa.
Without the offset capability of the opamp, the best bet is to get in touch with burson if the increase in supply voltage does not help.

[tanchiro58]

Some of you have different (earlier) Bursons - I cant imagine, can you post the photo?  Thanks

Dexsam,

I got the early version of Burson opamps with Vishay 0.01uF 1837 MKP and here are the pictures (sorry for not enough clarity!!!)

[analogmart]

Hi Tanchiro58,
I have around 210V in the day and around 230 -240 V at night and
It's just warm around opamp area, eventhough I leave DAC on 24 hours. 

My Burson opamp should be as same as Tanchiro's except
mine still in white copper case. I also use my old stock, MIT o.47 uf
for bypassing leg 4 and 7 without comparing result with other values.

I will try to change resistor as nick recommend cause it should be optimal for circuit
Mart

[tanchiro58]

I will try to change resistor as nick recommend cause it should be optimal for circuit
Mart

Mart,

Get either Riken or AN tantalum resistors which will sound extraordinarily beautiful!!! I will replace them soon.

Tan

[Dexsam]

Tan,  nice pictures you have there.  I notice a few differences, maybe Nic can eloborate.  Your DAC board looks like very close to the wood base (touching?), there's an air gap about 10mm in mine as the pcb sits on studbolts.  The output to the trans is twisted pair of cables (black) whereas in mine, its single strand solid core copper wire run parallel, no twisting.  The Bursons are essentially the same, only the lead out wires are different and looks like you inserted them into the IC sockets?  Can the top lid be put on with the Burson in place?  I notice cut pieces of black foam stuck to the top of the electrolytic caps, what are those? 

For me, I will be changing the power supply to variable type using LM317/337 in place of the LM7815/7915 and individually adjust the supply rails to the Bursons to achieve the near zero dc offset following Nic advice.  Will check out those tantalum caps Tan mentioned. Cheers.

[tanchiro58]

Tan,  nice pictures you have there.  I notice a few differences, maybe Nic can eloborate.  Your DAC board looks like very close to the wood base (touching?), there's an air gap about 10mm in mine as the pcb sits on studbolts.  The output to the trans is twisted pair of cables (black) whereas in mine, its single strand solid core copper wire run parallel, no twisting.  The Bursons are essentially the same, only the lead out wires are different and looks like you inserted them into the IC sockets?  Can the top lid be put on with the Burson in place?  I notice cut pieces of black foam stuck to the top of the electrolytic caps, what are those? 

For me, I will be changing the power supply to variable type using LM317/337 in place of the LM7815/7915 and individually adjust the supply rails to the Bursons to achieve the near zero dc offset following Nic advice.  Will check out those tantalum caps Tan mentioned. Cheers.

Dexsam,

When I got the DAC it was nothing except PCB board, transformers and other components. Since I believe spruce board (pine wood) helps a lot in preventing vibration especially those components on the pcb I modified the Promitheus DAC based on Altmann Attraction DAC model (I own too). I also padded some of black hole pads on every capacitors and chips once again preventing the micro-vibration. I added underneath the output transformers with two pieces of ebony wood too. I also replaced and twisted all the wires of the stock DAC with OFC silver plated wires that I got from my friend. That is why the reason I said about the comparison between Promitheus and Attraction DACs.

Yes, the Burson opamps in my DAC seat on the sockets that Nick gave me the option of swapping different opamps around. Therefore, I absolutely love the sound of my DAC now. I might not need to replace the resistors as Nick suggested since it might change the sound I have right now. Besides the output voltages by the opamps are stable in my DAC.

Tan

[analogmart]

Hi Nick,
Can you show exact picture where 180 Ohm resister located? I found 2 sections on board.
BTW, I measured +/- V. again last night. Voltage dropped from 15.3x to 14.3x stable when
it has burson op-amp loaded. And I found that regulator from both analog and digital section is quite hot,
very hot in digital section. I could not touch it more than 5 seconds. Is this normal?

But Dac is work just find...clean, nice detail and full body with music flows.   
Mart,

[tanchiro58]

Hi Nick,
Can you show exact picture where 180 Ohm resister located? I found 2 sections on board.
BTW, I measured +/- V. again last night. Voltage dropped from 15.3x to 14.3x stable when
it has burson op-amp loaded. And I found that regulator from both analog and digital section is quite hot,
very hot in digital section. I could not touch it more than 5 seconds. Is this normal?

But Dac is work just find...clean, nice detail and full body with music flows.   
Mart,

Mart,

Voltage regulator is always very warm to hot hence it is often attached with heat sink.  My DAC sounds just like yours. 

[hifihy]

My DAC produces a hum in my speakers. Not loud enough to interfere with the music but audible when the volume is turned up (from about 9 o'clock) with just the DAC connected to the amp. Nick suggested that I play around with different placement of the DAC but it didn't help. Has anybody has any experience on this matter?

[dainapoo]

I have the same hum.  I asked about it too.  Nicholas suggested I try different gain settings, but, of course that doesn't solve the problem. It you increase the gain, it just means you hear the hum at a lower volume setting and vice versa - same relative volume.  I'm guessing it's just part of the design.  Before I got the DAC and was using the TVC only, it was dead quiet at any setting.  But I would like to know if you and I are the only ones getting a hum.

Thanks!

[elb]

I have the same problem with the first dac I bought.After five months of constant communication with Nicholas , he sent me a new unit and it hums as well.The hum is actually worse than the original unit.I have given the original to unit to a specialist electronics engineer (audio) to find and fix the problem.

[Copperhead]

Sixteen pages of discussion about the dac, and now this comes up.

Nicholas quoted me 2-3 weeks for delivery, it's been 7 without a word.

He hasn't responded to any of my emails since I paid, not even to confirm that order, or a further order of

a pair of interconnects a few weeks later. Now we hear there is a problem with the dac. And since elb's

replacement was actually worse, he may not even know where the fault lies.

I don't want to be critical, but I'm not happy.

Are hifihy, dainapoo, and elb just the unlucky ones? Or are there more of you out there?

[threeminutes]

As I posted in a separate thread, I have also had a replacement as the first one had a loud hum, but this one has a different problem to the hum in that the sound is only coming through the right channel and the left channel has white noise.

[PTC]

I had the latest version of the Dac that I sold for other reasons but it was dead quiet.Also in defense of the bad press Nick is receiving lately I have bought several items from him and although wait times are somewhat long he never failed to respond to emails.Paul

[threeminutes]

Agree with you PTC, I have always found Nicholas to be polite and helpful and he does respond to emails even if it can take a little time.  Sometimes emails get caught in his spam folder so it can be worth resending any emails for which you haven't received a reply within a week or so.  In regards to my second DAC I beleive that it is likely to be a fault caused in transport as Nicholas has said that he tested the DAC before shipping and it worked fine. 

[highdfever]

Finally got this Sun discrete Opamp from Audio-gd   
http://www.audio-gd.com/enweb/pro/diy/OPA.htm

They claimed this is a revised version and no need to solder anymore bypass cap.  Cant confirm if this is same as Burson but very similar with much cheaper price.  Unfortunately, the new size of this Opamp is too large and cant insert directly to the IC socket, so not able to give any comments yet.