[holderlin]

I've had my promi dac for almost a year and really love it.  In last 3-4 months sometimes when I turned on my gear the DAC wouldn't have sound - the red led light was off.  If I unplugged and re-plugged or flipped the toggle switch on the back the sound would come back.  I asked Nik and he said it was a quirk of the machine and implied that it wouldn't get worse.  However, as time passed, this problem became more frequent. In the last two weeks, the dac cuts out almost every half-hour.  There's a brief fizzling, the sound quickly fades, its silent for varying lengths of time, then it comes back.  The cycle can take 30 seconds to 2 minutes.  I'm wondering if anyone has had a similar experience or has suggestions what might be going on. 

I've e-mailed Nik a couple times about this but haven't received a response.  I'm sure he'll get back to me but he's busy and his responses have been slow in coming so I thought I'd see if anyone here might have some ideas about what I might try to fix the problem. 

Thanks,
Bob

[NewBuyer]

Did you ever receive your separate USB module for your DAC? How is your DAC connected - coax, USB, etc?

Also, is your DAC a standard one (with the chip op-amp outputs), or does it contain the discrete Burson op-amp upgrade?

[holderlin]

Hi,

I received the USB module.  The Dac is connected by RCA coax.  There wasn't a Burson op-amp upgrade at the time I purchased so its the standard op amp. 
Thanks,
Bob

Did you ever receive your separate USB module for your DAC? How is your DAC connected - coax, USB, etc?

Also, is your DAC a standard one (with the chip op-amp outputs), or does it contain the discrete Burson op-amp upgrade?

[holderlin]

Nicholas answered my email and offered to replace the board.  Before he responded I decided to swap out the 75 ohm ic I'd been using. (I had actually been switching between two 75 ohm ics.)   I used an analogue ic and so far the sound hasn't cut out on me.  Nick said he's used 75 ohm without incident.  So far so good.  Has anyone else experienced this problem? I would like to be able to use the new 75 ohm ic I purchased from Burt Grover but I guess I'll have to live without it.  I'll let you know if I find that its definitely the 75 ohm ics.

bob

Hi,

I received the USB module.  The Dac is connected by RCA coax.  There wasn't a Burson op-amp upgrade at the time I purchased so its the standard op amp. 
Thanks,
Bob

Did you ever receive your separate USB module for your DAC? How is your DAC connected - coax, USB, etc?

Also, is your DAC a standard one (with the chip op-amp outputs), or does it contain the discrete Burson op-amp upgrade?

[NewBuyer]

Nicholas answered my email and offered to replace the board.  Before he responded I decided to swap out the 75 ohm ic I'd been using. (I had actually been switching between two 75 ohm ics.)   I used an analogue ic and so far the sound hasn't cut out on me.  Nick said he's used 75 ohm without incident.  So far so good.  Has anyone else experienced this problem? I would like to be able to use the new 75 ohm ic I purchased from Burt Grover but I guess I'll have to live without it.  I'll let you know if I find that its definitely the 75 ohm ics.

bob

Glad you got an email response Bob - many are finding it very difficult to reach Nick lately.   

Interesting that using the proper 75 ohm cable would be a problem... could this mean that the digital input (pulse) transformers Nick is using, are not 75 ohm? Does your DAC have the silver pulse transformer upgrade?

[tanchiro58]

I have own the first version of Promitheus DAC with silver pulse transformer that Nick sent to me for upgrading and I had upgraded myself the Burson Discrete opamps. I have never had issues or whatsoever that stop playing my musics since then. This is an excellent DAC I have ever had to play in my system. It is very balanced and musical. 

[holderlin]

I believe it does have the silver pulse upgrade.  When I bought it, it had all the bells and whistles available from Nick at the time and I think the silver pulse transformer was one of the offerings.

Bob

Nicholas answered my email and offered to replace the board.  Before he responded I decided to swap out the 75 ohm ic I'd been using. (I had actually been switching between two 75 ohm ics.)   I used an analogue ic and so far the sound hasn't cut out on me.  Nick said he's used 75 ohm without incident.  So far so good.  Has anyone else experienced this problem? I would like to be able to use the new 75 ohm ic I purchased from Burt Grover but I guess I'll have to live without it.  I'll let you know if I find that its definitely the 75 ohm ics.

bob

Glad you got an email response Bob - many are finding it very difficult to reach Nick lately.   

Interesting that using the proper 75 ohm cable would be a problem... could this mean that the digital input (pulse) transformers Nick is using, are not 75 ohm? Does your DAC have the silver pulse transformer upgrade?

[Dexsam]

Hi everyone,

After using the DAC with stock NE5534 op amp, for a month, I ordered the Burson discrete op amps from Australia and received them yesterday. Today (Sat), I tried bending the leads (extra long, new design according to Burson) in shape to suit the DIP8 pins, see picture below, thinking that I could just insert into socket and switch back to ICs anytime.


After many tries, I gave up inserting the Bursons into the IC socket.   So, I removed the IC socket and directly solder the Burson leads onto the PCB.  Finally, its done - see below.  You will notice that the Bursons are inverted - I dont know if its gonna be a problem.  Putting it the other way would obstruct the jumpers (for gain adj). Everything fits well inside and the cover can be closed with a 5 mm gap between Bursons and cover.


Now for the setting of voltage, I have a problem here.  Measuring from ground (G, circled & arrow), the voltages at pins 4 and 7 are measured and adjusted as instructed by Nic.   Problem is, I could not get the SAME voltage for the L & R sides.  The R side is always higher.  If I set the L side to say, +/-12V, the L reading is +12.04V and -12.08V; but the R side reading is +14.38 and -15.02V, such is the difference.  If I set the R side to +/-12V, the L side is measured at only 10~11V.  The 2 voltage adj screws are for positive and negative supplies and the L & R sides should get from the SAME supply, and hence the SAME voltage, but why the difference?  Can Nic please explain here?

Another thing - I measured the output (pin 6) with respect to ground and it is a high +1.14V for L; and +0.61V for R.  I know, this dc voltage is blocked by the output trans, but shouldn't the output be near zero or in the millivolt range at most.  On IC op amps we have the offset null adj. Can Nic explain how to set to zero?

Despite above setback, the sound is there (and good sounding too), no noise etc, at first burning in, but the Bursons runs quite warm after sometime - the pcb is in the region of 50deg C, which I think is too high so I switched it off until I get more assurance.  Anyone has the same experience and would like to share/comment/advise here?

Thanks in advance.

[Oscillate]

Dexsam, I am very interested in your modification experiment using the Burson Discrete
OpAmps. Are you going to solder a "foil capacitor across the power intake (V+ and V-) of
the Discrete Op-Amp", as suggested on the Burson website?

Please keep us posted on your results

[threeminutes]

Has anyone encountered a loud hum (can be heard even when the amp volume is at low levels) with the Promethius DAC?  I have contact Nicholas and I am sure he will get back soon with an answer but was just curious if anyone else had had this problem and if they solved it.

[tanchiro58]

Now for the setting of voltage, I have a problem here.  Measuring from ground (G, circled & arrow), the voltages at pins 4 and 7 are measured and adjusted as instructed by Nic.   Problem is, I could not get the SAME voltage for the L & R sides.  The R side is always higher.  If I set the L side to say, +/-12V, the L reading is +12.04V and -12.08V; but the R side reading is +14.38 and -15.02V, such is the difference.  If I set the R side to +/-12V, the L side is measured at only 10~11V.  The 2 voltage adj screws are for positive and negative supplies and the L & R sides should get from the SAME supply, and hence the SAME voltage, but why the difference?  Can Nic please explain here?

I have a same problems with big different output voltages of the Burson Discrete opamps between two channels. However, you should adjust based on your sonic tastes that come out of the DAC to your whole system. I have a first version DAC and Burson opamps with ground wires hang out. Your problem of getting warm as not usual happens to mine (running cool!!!). I guess you need to bypass pin4 and pin7 as Burson Audio suggested.

Good luck and happy listening,
Tan 

[tanchiro58]

Has anyone encountered a loud hum (can be heard even when the amp volume is at low levels) with the Promethius DAC?  I have contact Nicholas and I am sure he will get back soon with an answer but was just curious if anyone else had had this problem and if they solved it.

This sounds like unsual to me. Did you change or remove anything?

[threeminutes]

I only received it yesterday.  I also checked to make sure it wasn't the amp, cables, or RF, but the noise is clearly coming from the DAC via the line out irrespective if there is a digital signal coming in or not.  To be honest I was hoping for some easy solution so that the item will not have to go back.

[Dexsam]

Dear all,

After posting the problems faced after the direct replacement of NE5534 with Bursons, I receive no replies from Nic, so I contacted Burson.  And they told me this: optimal voltage supply is +/- 15V, and that the capacitors on board the DAC are insufficient (in value).  Hence recalling from somewhere, that Nic's design dont allow such high voltage and the voltage regulation would be poor because the Bursons draw a much higher current that the NE5534 it replaces, I decided to ADD a completely new power supply to cater for Bursons.  The Burson technical supported the idea saying the inadequate power supply is the cause of the 'not outstanding' bass that I complained as quality bass is their strength.

So, in went a new mains transformer with output 15V-0-15V, bridge rectifier, a pair of 2200uF capacitors, bypass capacitors, 15V+/- IC regulators x 4, followed by 4 x 470uF capacitors and at the Bursons end coupled the V+/- (pin 4, 7) with foil capacitors 0.1uF x 4 - maybe a bit overkill but it worked(see picture below - the new trans and voltage regulators on bottom left; yellow cylinders are foil caps).

Now I have no complaints on the sound, and its only running for a couple hours.  Everything is there, the bass is full, solid, the air in voices and cymbals, separation of instruments very clear - all in so much better than IC op amps.  My best investment so far - A$80 for the pair of Bursons and US$25 for the DIY power supply.  The only "problem" left is this : there is still a dc offset at the output and the Bursons run hot still - at about 53deg C steady state.  Burson technical say they run in class A and some heat is produced but I didnt think it is that hot!  So far happy with the upgrade, next would be just replacing the cheap electrolytics on my new power supply with Blackgate capacitors.

Tanchiro - i am surprised that your Bursons run cool - I actually measured the temp and it is the hottest component on the DAC.

Regards.

[tanchiro58]

Tanchiro - i am surprised that your Bursons run cool - I actually measured the temp and it is the hottest component on the DAC.

Hi Dexsam,

I am glad that you have just done an excellent modification. So that means you have eliminated all original power supply to use with your new one. Is this any link that you can provide us to try out a new power supply for the Promitheus DAC?

My Burson Discrete opamps run not too cool (sorry for the mistake) but they are little warm but not hot to too hot. I thought that would be totally normal for a component. However, I still love the balanced sound of my Promitheus DAC compared to my Altmann Attraction DAC (8:10 ratio to my ears).

It is good to know another modified version for the DAC from you. Keep a good work and share with us it would be appreciated.

Many thanks,
Tan
 

[tanchiro58]

I only received it yesterday.  I also checked to make sure it wasn't the amp, cables, or RF, but the noise is clearly coming from the DAC via the line out irrespective if there is a digital signal coming in or not.  To be honest I was hoping for some easy solution so that the item will not have to go back.

Double check your digital cable connection from the source to the DAC. I had a problem once when friend of mine he did for me a DIY silver RCA digital cable and had a loud hum on one channel when I switched to RCA from BNC. First I thought the DIY cable lacked of insulation but yesterday I reconnected to the same connector the hum was not there. It is hard to explain this matter but you need to check step by step. Good luck.

[Dexsam]

Hi Tan,

What I did was, ADD a new power supply which outputs separately two +15V and two -15V (hence the four IC regulators) actually you can use 2 regulators giving one +15v and one -15V with the L & R channels sharing the power supply. In my case there is no sharing (for better separation, I guess), afterall an IC regulator (LM7815 for positive, LM7915 for negative) cost under $1 each.  Then I disconnect the Bursons power supply leads (pin 4 for negative, pin 7 for positive) from the DAC main pcb, and connect to the newly built power supply.  The original power supply from the DAC main pcb is left intact, as it maybe routed to power other parts of the circuit of the DAC.  Now that the Bursons got separate power supply means there is less load for the original power supply - an added advantage.  Of course, not forgetting the Ground (0V) of the power supply is connected to the main pcb ground.  My new transformers have 15V-0-15V (AC) outputs hence giving a rectified but unregulated +/-21Volts DC, more than enough voltage for the regulators to bring down to the required +/-15V.

I just use the standard regulated power supply circuit from the application notes of LM7815/7915 IC regulators (available online)to construct my power supply, nothing fancy; only thing I over design a little on the smoothing capacitors.  Some say LM317 regulators are better, but the LM78XX is good enough and very simple, just one chip.

I am surprised to hear that some using the DAC had 'hum/noise' problems - maybe ground loop issue in the connections.  Mine had no noise nor hum - dead quiet, before and after adding new power supply.

Thanks for reading.

[NewBuyer]

...I receive no replies from Nic, so I contacted Burson.  And they told me this: optimal voltage supply is +/- 15V, and that the capacitors on board the DAC are insufficient (in value)... Nic's design dont allow such high voltage and the voltage regulation would be poor because the Bursons draw a much higher current that the NE5534 it replaces... Burson technical supported the idea saying the inadequate power supply is the cause of the 'not outstanding' bass that I complained as quality bass is their strength...

Dexam I'm glad you were able to build such a nice quality power supply fix for this situation - I wish that I had your skills.

If the stock Promitheus DAC has unsuitably low voltage and insufficient capacitors for the direct Burson mod, this unfortunately might mean that probably users of the DAC who purchased the Burson upgrade directly from Burson and installed it themselves, may have their Burson product performing more poorly than it should, as a result - especially as you reported, in the bass.

Hope you can also fix the further problems, regarding DC offset and heat...

Edit: Nick has already commented later in this thread, about how to fix...

[tanchiro58]

Hi Tan,

What I did was, ADD a new power supply which outputs separately two +15V and two -15V (hence the four IC regulators) actually you can use 2 regulators giving one +15v and one -15V with the L & R channels sharing the power supply. In my case there is no sharing (for better separation, I guess), afterall an IC regulator (LM7815 for positive, LM7915 for negative) cost under $1 each.  Then I disconnect the Bursons power supply leads (pin 4 for negative, pin 7 for positive) from the DAC main pcb, and connect to the newly built power supply.  The original power supply from the DAC main pcb is left intact, as it maybe routed to power other parts of the circuit of the DAC.  Now that the Bursons got separate power supply means there is less load for the original power supply - an added advantage.  Of course, not forgetting the Ground (0V) of the power supply is connected to the main pcb ground.  My new transformers have 15V-0-15V (AC) outputs hence giving a rectified but unregulated +/-21Volts DC, more than enough voltage for the regulators to bring down to the required +/-15V.

I just use the standard regulated power supply circuit from the application notes of LM7815/7915 IC regulators (available online)to construct my power supply, nothing fancy; only thing I over design a little on the smoothing capacitors.  Some say LM317 regulators are better, but the LM78XX is good enough and very simple, just one chip.

I am surprised to hear that some using the DAC had 'hum/noise' problems - maybe ground loop issue in the connections.  Mine had no noise nor hum - dead quiet, before and after adding new power supply.

Thanks for reading.

Dexsam,

Thanks for sharing the modification you did to your DAC by building the Burson opamp's owned PS. It is an excellent idea IMO. But this modification might be overkill in my system since I have enough everything like I said balanced sound that I have never heard. Your DAC is a new version one which is differently built by Nick I guess. I got and inserted the Burson opamps since day one and did not have any problem whatsoever til now.

It would be nice from you if you report later how does the sound change in your system after installing Burson opamp's PS.

[PromitheusAudio]

Actually on our dac board, the power supply for the opamp is made much more stringent due to the 5534 lower PSRR ratio.

Our power transformer is has 2 segments, 1 set of wires is for the digital (3cables braided) and 1 set of wires for analague (opamp onlY, 3 wires braided). This is 20va and is 15-0-15 in balanced winding for noise cancellation. So its 21 volts before the regulator too.
It feeds a lm317L series which has better PSRR than the stock lm317 and then after that each power supply feeds a dedicated discreet regulator. Normally after the discreet regulator there is not much left of voltage headroom for regulation
The power supply before the discrete regulator can be made for +-15volts with a problem. 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. The 2nd stage may require a 120volt main supply. On its own the highest voltage the dac can be set is 13.8volts which is more than adequate headroom for the 5534 but not for the burson.
Again the double stage regulation is a must for lower PSRR 5534.

Also the burson offset voltage depends on voltage and i am not sure they can be trim. The transformer likes to see some offset to linearize the core 20mv to 30mv would be the a good range for sonics reasons. 80mV is not that bad. DO note i prefer the sound with some offset, sound better as the dc forces the core to run in a more linear BH curve

When we install burson, we just swap the 180ohm resistor near the opamp to 50ohms then it would regulated higher.
The burson needs higher to work with because of the transistors and the jfets they used

dexsam
did not get your email. Could have enter our spam filter
COuld have also miss this email, during the last 4 months we are shortage of manpower, we were trim to half our manpower and i was basically doing all the process to cover and make up for it
Things are better now as we are back to full manpower