A '15v' transformer actually puts out 15v RMS which can be too much voltage in some cases.
LT1963 regulators, for example, are rated for a maximum input voltage of 20v. Good to use a cheap LM317/LM337 regulator board adjusted to maybe 18v before the LT1963 regulators to make sure the voltage never goes over 20v. In that case it would be fine to use an 18v transformer too.
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Some further background information:
To estimate transformer ratings, for sine waves like in the power lines the peak voltage is 1.414 times the RMS voltage. The peak to peak voltage is twice the peak voltage. Thus, a 15v transformer would put out 21.21v peak, and the peak to peak would be twice that.
Depending on how heavily an unregulated power supply is loaded (how much current is drawn) the output voltage might vary between the peak voltage and the RMS voltage.
If a single transformer secondary winding is rectified with a full wave bridge rectifier, the peak maximum output voltage will be the peak to peak value of the RMS rating.
Lots more information can be found by looking up an old copy of the Motorola Rectifier Handbook online. There are many other resources as well.
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On a 9038Q2M, the 12 v rails is not a problem at all. It becomes a problem when a dac chip with higher current output, if the feedback resistors in the transimpedance stage is high. Now with the OPA1612 which can swing closer to the rail voltage than the LME49720 it is even less of a problem but neither of them should be an issue on paper.
I am still waiting for my board. With the postal strike it could a lot more time.
Did you find out how low it can be adjusted to?
I would also caution you that despite myself not having received a similar board as yet, that there will be some physical limitations to this board.
I don't know what voltage the input filter caps are rated for but you need to know that the 5534 op amp is possibly powered by the filtered voltage and this should not be more than say around 30V although the 5534 is rated up to 44V! rail to rail. Now the minimum voltage I have found the 5534 to work reliably to is 10V single ended. Anything less can be unstable operation. So for the lower voltage, you want to see a minimum of 10V after rectification and filtering.
Now for the output voltage since FETs are being used as the pass element, they need for the typical currents being passed a minimum of 4-5V higher than the output voltage.
http://www.irf.com/product-info/datasheets/data/irf9z34ns.pdf
I wonder if this is the issue you are having with the 12V you are seeing as maximum. To obtain 15V output you would typically have to see around 20-22V minimum at the filter caps.
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Thank you for the DAC Thread Post List 4, I have some reading to do
Yeah, I should probably make an abridged version of that leaving out things that were of interest to me, but clearly not necessary for help with specific modding tasks and or dac operation.
EDIT: Sorry, forgot to say, "you are welcome!" in return for your thanks. I always try to do that because I want people to know I am happy to be of assistance with dac modding efforts and interests.
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Hi Mikett,
thanks for the advise. I feed the board with 15VAC. Input Filter cap has 23V and opamp V+ to V- has 21V.
Min. adjustable output voltage is 10,5V for the +-12V rails. 5V rail was not connected / tested yet.
So 12,75 max regulation voltage or even 15V (if I know how to do) should be OK, right?
My board looks a little different than the shown one. It is black and has small layout change - looks pritty cool for 20 bugs! ;-)
thanks for the advise. I feed the board with 15VAC. Input Filter cap has 23V and opamp V+ to V- has 21V.
Min. adjustable output voltage is 10,5V for the +-12V rails. 5V rail was not connected / tested yet.
So 12,75 max regulation voltage or even 15V (if I know how to do) should be OK, right?
My board looks a little different than the shown one. It is black and has small layout change - looks pritty cool for 20 bugs! ;-)
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You can simply adjust the trim resistor the other way and see how low the output voltage can get. There should be no need for physically changing the connect portion. I'm very interested in this aspect. I would be curious to know to know if it can make it down to between 3.3 and 3.7V.
if I see this correctly, the reg above has the topology: Vref-LPF-OpAmp-PassTr. I have been using similar homebuilt regs for AVCC from very beginning. since Vref apparently is TL431 and opamp 5534, then the regulated voltage range could be from 2.5V to Vin-2V. locate the voltage divider resistors in FB and set the desired output voltage. it should be 2.5V on op amp negative input. also, it is better to run them with Vin=Vout+4V
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Thank you eziitis. Maybe I will try later, but for now happy with 12,75V.
Markw4, I still have some questions regarding DAC powering:
1) Do you power both VCCA rails with same external powered LDO keeping onboard ferrite filters and Caps for each VCCA rail?
2)Do you power MCU by external PSU (same PSU as 1)?) or from onboard +15V line->7805Vreg(guess you changed it to better one)->AMS1117-3,3?
I am straight thinking how to handle my LP5907-3,3V LDOs probably substituating the ferrite filter resistors for both VCCAs, Clock, DVCC and feeding the currrent 3,3V lines with 5V externally as source for the LDOs. Guess both VCCAs should be fed from same LDO, no?
Markw4, I still have some questions regarding DAC powering:
1) Do you power both VCCA rails with same external powered LDO keeping onboard ferrite filters and Caps for each VCCA rail?
2)Do you power MCU by external PSU (same PSU as 1)?) or from onboard +15V line->7805Vreg(guess you changed it to better one)->AMS1117-3,3?
I am straight thinking how to handle my LP5907-3,3V LDOs probably substituating the ferrite filter resistors for both VCCAs, Clock, DVCC and feeding the currrent 3,3V lines with 5V externally as source for the LDOs. Guess both VCCAs should be fed from same LDO, no?
I am currently tying the two VCCA pins together using a jumper wire between the filter caps on each side of the dac chip, bypassing the inductors. However, the LT1763 is connected in series with one of the inductors. Don't know if it makes any difference. In any case, both VCCA pins should both be fed from the same power supply one way or another.
The MCU is still powered as it was originally. No changes. The external 5v power supply I use feeds the original 3.3v regulator on the board as well as all the new LT1763 regulators.
A simple tweak could improve the performance - if it works, reconfigure the LT304x op amp as a sallen key low pass filter, I need to buy one to try.
TL431 are noisy, I use them in my shunt version of the Super Reg with dedicated 12dB sallen key, ~ 1.5Hz (47K & 2u2F).
Attachments
hi, there,
there is a es9038q2m i2c linux driver on github,
GitHub - VinnyLorrin/ES9038Q2M-Linux_Driver
i'll compiler and try it in next a couple of days.
cheers
there is a es9038q2m i2c linux driver on github,
GitHub - VinnyLorrin/ES9038Q2M-Linux_Driver
i'll compiler and try it in next a couple of days.
cheers
Hi,
for DAC and clock powering by LP5907 LDO I wonder how to handle the info about max output cap size for this reg. It is written in datasheet as maximum output cap size 0,7 to 10 uF. For both VCCA I have 2 tantalium filter caps (probably 10uF each)+ 2 ceramics already on the board. Is it necessary to place a resistor (e.g.47Ohm) or the ferrite bread between the LDO output (with 1uF cap to ground before the bread) and the VCCA / Clock filter caps to not exceed max cap size though?
Would it make sense to place a ferrite bread at AMS1117 (which feeds MCU and DVCC) input to not pollute the 5V rail which also powers the other LDOs for VCCAs and Clock?
another thing about opamps. Markw4 mentioned that AD797 needs resistor before a low ESR filter elko (if bigger than 4,7uF) - I remember a professional German tuner for Linn streamers and oppo and sonos players (Dr. Gert Volk) uses LME49720 with very low ESR FP organic polymer caps (7mOhm, 330uF) in both power lines and feeds them with a bank of caps through a 100 Ohm resistor. No additional ceramics or tantal. He also recommended to place a 100nF film cap over the input power pins if other solution is not feasable. Maybe this would also help for our device to get ridd of the slightly brightness with those opamps?
for DAC and clock powering by LP5907 LDO I wonder how to handle the info about max output cap size for this reg. It is written in datasheet as maximum output cap size 0,7 to 10 uF. For both VCCA I have 2 tantalium filter caps (probably 10uF each)+ 2 ceramics already on the board. Is it necessary to place a resistor (e.g.47Ohm) or the ferrite bread between the LDO output (with 1uF cap to ground before the bread) and the VCCA / Clock filter caps to not exceed max cap size though?
Would it make sense to place a ferrite bread at AMS1117 (which feeds MCU and DVCC) input to not pollute the 5V rail which also powers the other LDOs for VCCAs and Clock?
another thing about opamps. Markw4 mentioned that AD797 needs resistor before a low ESR filter elko (if bigger than 4,7uF) - I remember a professional German tuner for Linn streamers and oppo and sonos players (Dr. Gert Volk) uses LME49720 with very low ESR FP organic polymer caps (7mOhm, 330uF) in both power lines and feeds them with a bank of caps through a 100 Ohm resistor. No additional ceramics or tantal. He also recommended to place a 100nF film cap over the input power pins if other solution is not feasable. Maybe this would also help for our device to get ridd of the slightly brightness with those opamps?
@freezebox, The AD797 data sheet warns about stability issues with decoupling cap size/cap ESR. Other opamps are available that don't have that same issue. I may try an OPA1612 for AVCC, but I think LME49720 can work okay too. No reason why I have to stick with AD797, but if I felt I really needed it then I would add a little series resistance with the AVCC power rails to stabilize it. Probably not worth the bother at this point. Besides, I want to keep the AVCC power rail impedance low.
Regarding remaining brightness, I need to redo harmonic distortion compensation since I added more filter caps and changed opamps to OPA1612. Also, I probably should look at adding a little RF filter between the dac outputs and I/V inputs, just to see what happens with that. That would probably require redoing harmonic distortion compensation one more time though. Another place to look for distortion might be in the interpolation filter, and is why I started looking into using Spartan 6. To the extent that may be a problem, a fix may be a ways off. No time to work on it recently and probably won't get back to it until Katana listening comparisons are over.
Another area affecting distortion is DPLL bandwidth. I was able to get it down to 3 or 4 out of 10 yesterday. It is rather tricky, and dealing with it empirically all the more so. I want to see if I can rig up something to measure with. Have to see on that. I will write some more about all that pretty soon, but the important thing for people to be aware of is that register tweaking is a must for best sound quality and lowest distortion.
Will try to keep picking away at remaining imperfections. However, please remember I am comparing the modded dac to the SOA DAC-3 which uses additional technology that we are not using in order to get its sound. That and well equipped electronics lab to do a lot of measurements. The multi-layer PCB (6 layers?) it uses is well past its 2nd revision. It is also their third dac whereas this is my first, and at rev 2, or maybe only 1.2.
And as I said before, we probably don't need to worry so much about the stuff we are already doing pretty well, we need to worry about the stuff we aren't doing at all.
I also don't know how far we can get using off-the-shelf 100MHz clocks rather than buying reels at a time of custom spec'ed lower frequency clocks. There are lots of issues here if one wants to keep moving towards SOA.
I could probably go on and on, but no use in doing so. It would help if we had a few people caught up to me with their builds so we could compare experiments, or break up experimental work between us in a thoughtful, organized way. How about that?
Regarding remaining brightness, I need to redo harmonic distortion compensation since I added more filter caps and changed opamps to OPA1612. Also, I probably should look at adding a little RF filter between the dac outputs and I/V inputs, just to see what happens with that. That would probably require redoing harmonic distortion compensation one more time though. Another place to look for distortion might be in the interpolation filter, and is why I started looking into using Spartan 6. To the extent that may be a problem, a fix may be a ways off. No time to work on it recently and probably won't get back to it until Katana listening comparisons are over.
Another area affecting distortion is DPLL bandwidth. I was able to get it down to 3 or 4 out of 10 yesterday. It is rather tricky, and dealing with it empirically all the more so. I want to see if I can rig up something to measure with. Have to see on that. I will write some more about all that pretty soon, but the important thing for people to be aware of is that register tweaking is a must for best sound quality and lowest distortion.
Will try to keep picking away at remaining imperfections. However, please remember I am comparing the modded dac to the SOA DAC-3 which uses additional technology that we are not using in order to get its sound. That and well equipped electronics lab to do a lot of measurements. The multi-layer PCB (6 layers?) it uses is well past its 2nd revision. It is also their third dac whereas this is my first, and at rev 2, or maybe only 1.2.
And as I said before, we probably don't need to worry so much about the stuff we are already doing pretty well, we need to worry about the stuff we aren't doing at all.
I also don't know how far we can get using off-the-shelf 100MHz clocks rather than buying reels at a time of custom spec'ed lower frequency clocks. There are lots of issues here if one wants to keep moving towards SOA.
I could probably go on and on, but no use in doing so. It would help if we had a few people caught up to me with their builds so we could compare experiments, or break up experimental work between us in a thoughtful, organized way. How about that?
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Regarding immediate plans, now that Katana 1.2 is here, it is a good time to finish up where I am right now, and do some listening comparisons. Who knows, maybe I will learn something. For that, I need to redo harmonic distortion compensation for the modded dac, and then just leave it at its present iteration.
I will take some time to compare different power configurations, and board choice configurations for Katana. Want to try it with power that Allo recommends, and with power that I use for my modded dac. I figure that will have to be good enough power to go with a $250 dac board, besides its the best I have .
When I get Katana sounding as good as I can, then I will do a careful 3-way listening comparison and let you all know where things stand.
Also, while I have Katana here, I will take some pictures of the boards and if there is interest, I will explain about some of the design details that can be gleaned by inspection.
I will take some time to compare different power configurations, and board choice configurations for Katana. Want to try it with power that Allo recommends, and with power that I use for my modded dac. I figure that will have to be good enough power to go with a $250 dac board, besides its the best I have
. When I get Katana sounding as good as I can, then I will do a careful 3-way listening comparison and let you all know where things stand.
Also, while I have Katana here, I will take some pictures of the boards and if there is interest, I will explain about some of the design details that can be gleaned by inspection.
