Another CFP output design attempt.
- By de Ocampo
- Solid State
- 70 Replies
...been working on this circuit and something to get my hands busy during vacant days. As I'm getting my grip (and brains) back with LTSpice..please let me know if what I'm doing does not involve redundant parts (and flawed results 🙂).
Closed loop.
PM/GM
Step response @ 1KHz & 20Khz
Clipping point
Series of Fourier test at 1Khz 1W / 20Khz 1W / 1Khz 50W / 20Khz 50W (estimated max power)
Schematic
THD may not be pleasing, I understand it is a Sziklai output..if I wanted to lower THD..H2 level goes down as well (bias current 40ma).
Let me know if the circuit will qualify as a working amp in a real world build.
Thanks!
Closed loop.
PM/GM
Step response @ 1KHz & 20Khz
Clipping point
Series of Fourier test at 1Khz 1W / 20Khz 1W / 1Khz 50W / 20Khz 50W (estimated max power)
Schematic
THD may not be pleasing, I understand it is a Sziklai output..if I wanted to lower THD..H2 level goes down as well (bias current 40ma).
Let me know if the circuit will qualify as a working amp in a real world build.
Thanks!
Improving a cheap chinese PCM1794 DAC
- By pachy
- Digital Line Level
- 97 Replies
Sorry if this board was already discussed but I didn't find anything related to it.
I few years ago I paused my diy audio hobby and sold/gifted everything I had built but an year ago I felt the need to start enjoying music once again. In no more than 1 month time I bought the ATC SCM11 curved speakers which I fell in love with at the first note, built a Raspberry Pi 3 + Volumio streamer, built the PeeCeeBee V4H known to most of you and now I was in need of a new DAC which will be used as my main audio source. The requirements were simple:
– Digital input switching. I wanted to use the same DAC whether I am listening from my DIY Volumio streaming device or watching a movie/playing Xbox.
– Good to exceptional sound quality.
After reading an article by a russian author, the PCM1794 datasheet and talking to a friend of mine who works in a professional audio equipment manufacturing company, I decided to try the PCM1794 from Burr Brown for this project. I did a quick search on Aliexpress for readily available PCBs based on PCM1794 and I came across one that looked well made. The PSU part is well separated utilising:
– Four separate transformer windings with 3 bridge rectifiers (MCU+LCD; digital section PSU; analog section PSU)
– Five on board regulators (LM7805 for the uC/LCD, LT1968-3.3V for the AK4118 and PCM1794 digital supply, LM317(5V) for the PCM1794 analog VCC, LM317/337(+-15V) for the opamp supply.
– Utilized ground planes
The board costed only 47$ so I expected cheap capacitors and probably fake AD827 opamps. After 20 days I received the board. I was right, they used cheap caps(except the big filter Nichicons, which seem good) and the opamps are probably fake at this price so I started planning mods to the board.
The first thing I did was to test the board before doing anything so I know if it works as expected. I plugged in all required windings, plugged my set-top box as digital source with an optical cable and flipped the switch…
F**k… The thing is not even working…
Chinese PCM1794 AK4118 board
The first thing I did was to measure all the supplies. I found out that the LT1968-3.3 had 2.0V at its output so the AK4118/PCM1794 didn’t get enough voltage to work. I desoldered the LT1968 and soldered a LD1117V33. It finally worked. Good thing is I don’t have to return it to the seller and I can start with the mods.
After inspecting the board and following some traces I have annotated the photo of the board of all planned mods for convenience.
I have done the following modifications:
1. Change all big diodes in the rectifier bridge to SB5A0 fast recovery diodes because the old ones were standard Chinese diodes with shady letters on them.
2. I checked all resistor values according to the following OPA1611(single version of OPA1612) schematic and found out that the 8200pF capacitors were actually 220pF(marked on board as 820pF) and the 2700pF were actually 270pF(marked on board as 270pF). Resistor values were right according to this schematic.
OPA1612 as I/V converter
Changed those to Wima FKS2 capacitors with the right values and also changed the 2200pF metallized film capacitors in the feedback of the I/V stage with same value Wima FKS2.
3. Changed all electrolytic capacitors to Nichicon UPS which are low impedance, high temp range capacitors suitable for PSU usage. Some of the capacitors were 47uF instead of the 10uF according to the PCM1794 datasheet.
4. The final thing to do was change two of the AD827(probably fake) to two OPA1612 opamps in the I/V stage and change the third AD827 in the differential to single convertor stage to OPA2132.
I will now let the DAC burn in for a couple dozen hours and I will start listening! The next planned mod is to change all regulators to discrete ones based on a new schematic I am now evaluating. I will combine this DAC in one enclosure with my Volumio streamer and the JLSounds XMOS in the next few days. Any other ideas for possible mods/swaps?
I few years ago I paused my diy audio hobby and sold/gifted everything I had built but an year ago I felt the need to start enjoying music once again. In no more than 1 month time I bought the ATC SCM11 curved speakers which I fell in love with at the first note, built a Raspberry Pi 3 + Volumio streamer, built the PeeCeeBee V4H known to most of you and now I was in need of a new DAC which will be used as my main audio source. The requirements were simple:
– Digital input switching. I wanted to use the same DAC whether I am listening from my DIY Volumio streaming device or watching a movie/playing Xbox.
– Good to exceptional sound quality.
After reading an article by a russian author, the PCM1794 datasheet and talking to a friend of mine who works in a professional audio equipment manufacturing company, I decided to try the PCM1794 from Burr Brown for this project. I did a quick search on Aliexpress for readily available PCBs based on PCM1794 and I came across one that looked well made. The PSU part is well separated utilising:
– Four separate transformer windings with 3 bridge rectifiers (MCU+LCD; digital section PSU; analog section PSU)
– Five on board regulators (LM7805 for the uC/LCD, LT1968-3.3V for the AK4118 and PCM1794 digital supply, LM317(5V) for the PCM1794 analog VCC, LM317/337(+-15V) for the opamp supply.
– Utilized ground planes
The board costed only 47$ so I expected cheap capacitors and probably fake AD827 opamps. After 20 days I received the board. I was right, they used cheap caps(except the big filter Nichicons, which seem good) and the opamps are probably fake at this price so I started planning mods to the board.
The first thing I did was to test the board before doing anything so I know if it works as expected. I plugged in all required windings, plugged my set-top box as digital source with an optical cable and flipped the switch…
F**k… The thing is not even working…
Chinese PCM1794 AK4118 board
The first thing I did was to measure all the supplies. I found out that the LT1968-3.3 had 2.0V at its output so the AK4118/PCM1794 didn’t get enough voltage to work. I desoldered the LT1968 and soldered a LD1117V33. It finally worked. Good thing is I don’t have to return it to the seller and I can start with the mods.
After inspecting the board and following some traces I have annotated the photo of the board of all planned mods for convenience.
I have done the following modifications:
1. Change all big diodes in the rectifier bridge to SB5A0 fast recovery diodes because the old ones were standard Chinese diodes with shady letters on them.
2. I checked all resistor values according to the following OPA1611(single version of OPA1612) schematic and found out that the 8200pF capacitors were actually 220pF(marked on board as 820pF) and the 2700pF were actually 270pF(marked on board as 270pF). Resistor values were right according to this schematic.
OPA1612 as I/V converter
Changed those to Wima FKS2 capacitors with the right values and also changed the 2200pF metallized film capacitors in the feedback of the I/V stage with same value Wima FKS2.
3. Changed all electrolytic capacitors to Nichicon UPS which are low impedance, high temp range capacitors suitable for PSU usage. Some of the capacitors were 47uF instead of the 10uF according to the PCM1794 datasheet.
4. The final thing to do was change two of the AD827(probably fake) to two OPA1612 opamps in the I/V stage and change the third AD827 in the differential to single convertor stage to OPA2132.
I will now let the DAC burn in for a couple dozen hours and I will start listening! The next planned mod is to change all regulators to discrete ones based on a new schematic I am now evaluating. I will combine this DAC in one enclosure with my Volumio streamer and the JLSounds XMOS in the next few days. Any other ideas for possible mods/swaps?
What is this kind of technique used by Apogee?
- By ztwindwalker
- Headphone Systems
- 5 Replies
I didn't find a defused picture of this device(apogee symphony i/o mkII).,So is there someone could say something about"constant current drive headphone AMP"?
New CBT Woofers
- Multi-Way
- 10 Replies
When I heard the new CBTs at CES, I'd assumed that they were using the Dayton ND65 woofers. But they said they weren't, and that it used a new driver with improvements requested by Don Keele.
I believe the original CBTs did something similar; the Dayton ND91 has more BL and a shorting ring iirc. (It's based on the Dayton ND90.)
So...
Let's see what's going on with the new Dayton ND64, versus the old Dayton ND65.
From a quick look at the spec sheet, it looks like:
1) the new ND64 is cheaper
2) the new ND64 has half the xmax
I'd speculate that what they were trying to do is lower the moving mass. The MMS of the ND64 is 16% less than the ND65. This may contribute to it's high frequency extension.
It's a bit odd that Dayton overlooked a couple of other drivers in their stable. For instance, the Tectonic Elements TEBM35 has lower mms, flatter response, and lower cost than both the ND64 and the ND65.
(http://medleysmusings.com/tectonic-elements-tebm35c10-4-miniature-bmr-driver/)
I believe the original CBTs did something similar; the Dayton ND91 has more BL and a shorting ring iirc. (It's based on the Dayton ND90.)
So...
Let's see what's going on with the new Dayton ND64, versus the old Dayton ND65.
From a quick look at the spec sheet, it looks like:
1) the new ND64 is cheaper
2) the new ND64 has half the xmax
I'd speculate that what they were trying to do is lower the moving mass. The MMS of the ND64 is 16% less than the ND65. This may contribute to it's high frequency extension.
It's a bit odd that Dayton overlooked a couple of other drivers in their stable. For instance, the Tectonic Elements TEBM35 has lower mms, flatter response, and lower cost than both the ND64 and the ND65.
(http://medleysmusings.com/tectonic-elements-tebm35c10-4-miniature-bmr-driver/)
Problem with LenearX
- By Stich
- Equipment & Tools
- 0 Replies
Hi,
I have not used the system for a long time, so it happened a couple of days ago, I had to take measurements, and the LinearX system gives an error when measuring the impedance.
I tried to solve the problem by reinstalling Windows 7, but it did not help. I tried to do internal and external calibration, it also does not help.
Sometimes the system fails internal calibration:
Highlighted in red the item that the system sometimes does not pass.
Thanks in advance for your help.
I have not used the system for a long time, so it happened a couple of days ago, I had to take measurements, and the LinearX system gives an error when measuring the impedance.
I tried to solve the problem by reinstalling Windows 7, but it did not help. I tried to do internal and external calibration, it also does not help.
Sometimes the system fails internal calibration:
Highlighted in red the item that the system sometimes does not pass.
Thanks in advance for your help.
Shok Industries 5K mono amp
Good day to everyone. I am repairing a Shok Industries Winner series 5k mono amp which had a blown capacitor in the output section.
I was able to removed the blown caps and cleaned the board which is quite difficult which I did not expect. I was surprised that even
with this blown fault the Output transistors and the gate signasl survived so I believed and hope that replacing the caps will bring it to life completely.
My real help is , what is the value of the 106K 250v capacitors in farad, how does it read or meaning of the values of the capacitor.
Please refer in the picture of the value. Second is , Can I use other capacitor in
other physical form with same value. Thank You in advance bro.
I was able to removed the blown caps and cleaned the board which is quite difficult which I did not expect. I was surprised that even
with this blown fault the Output transistors and the gate signasl survived so I believed and hope that replacing the caps will bring it to life completely.
My real help is , what is the value of the 106K 250v capacitors in farad, how does it read or meaning of the values of the capacitor.
Please refer in the picture of the value. Second is , Can I use other capacitor in
TandyMOS is not your typical amplifier:
- By Elvee
- Solid State
- 44 Replies
It has no diff-pair input, no DC-servo (yet its DC offset is negligible), no complementary output, no adjustments (yet its quiescent current is stable and deterministic), it uses ordinary vertical enhancement NMOS having a normal threshold voltage, yet it is free from the output swing limitations normally associated with such devices. The topology is half non-switching, half class AB and inverting.
In short: an oddity.
It is based on the Tandem topology, which has been evoked here: https://www.diyaudio.com/community/...here-is-the-legacy-thread.387391/post-7059293
I have already described a Tandem-based amplifier: https://www.diyaudio.com/community/threads/tandem-based-amplifiers.388400/post-7074596 but it was essentially a showcase and a test-bed for the concept: the VAS was simply an operational amplifier, thus limiting the power to 10~20W, since HV opamps like the LM143 have mostly disappeared.
It could certainly be used though, and for domestic applications the power is ample enough.
However, DIYaudio members prefer something more substantial, and here it is: the front-end is now completely discrete, meaning the rail voltages can be as high as necessary.
The tandem topology has been adapted to MOS (mostly by Minek), and a clever trick overcomes the limitation caused by the threshold voltages.
The Vth-erasers are simply voltage-memory circuits inserted in series with the gate, to reduce or cancel the threshold voltage, changing the MOS into a zero-threshold type. The circuits themselves are extremely simple: a capacitor paralleled with a shunt-regulating device (LEDs in this case), and fed by a large value resistor.
In principle, the concept could be used in any other amplifier (and I have done it in the Circlomos), but with "normal" amplifiers there is a difficulty: the voltage needs to be very stable and accurate because it will influence the quiescent current.
By contrast, the Tandem stage has its quiescent current tightly controlled by a feedback loop, and the only effect of a non-optimal voltage is a tiny reduction of the output swing: not a big deal.
Unfortunately, MOS transistors do not shine in the tandem topology: with the original semi's line-up, I couldn't bring the THD below 0.85%, even with the tweaks at their optimum. M1 was a IRFD9120 (which explains the 4-pin socket).
With a BSP92 or even a BJT (2N5401), this was reduced to 0.25%.
Better, but a far cry from the BJT tandem: 0.004%.
The inferiority of the MOS version is probably down to the numerous parameter mismatches: a BJT is characterized by the BE PN junction, which becomes a NP junction for the correction transistor, and there is relatively little wiggle room outside of the fundamental exponential V-to-I relationship.
With MOS transistors of different sizes and polarirty, things become much more complicated. It is probably possible to improve the matters by hand-picking transistors having nicely scaled parameters, but I didn't go that far.
Anyway, in this case it does not matter very much, even with the worst-case 0.85%.
The front-end has a huge open-loop gain (almost half a million), and a relatively mediocre THD: between 1.5 and 2%. This THD will dominate, because there is no definite addition rule for THD: in theory, perfectly coherent distortions could add arithmetically, or anti-coherent distortions could even cancel one another (error-correction situation), but such situations only happen when they are deliberately planned for.
In normal cases, you are somewhere in-between. When lots of random processing blocks are cascaded, the end result will tend towards the root of the sum of squares, but in simpler cases, it could be anything but will generally be close to the largest value, in this case ~1.7%.
When the loop is closed, this value will be reduced by the loop-gain, which is substantial, and results in a final THD figure of ~3ppm, thus quite good, but not enough to qualify as a "super-amplifier".
About the front-end:
It could raise eyebrows: it is based on a raw, undegenerated diamond structure, which looks risky and brutal. Howevever, because of the GNFB, Q3/Q4 and Q7/Q8 are forced to have the same current, and the rest of inequalities only have a minor effect.
In practice, it works like a charm: I picked the transistors at random from the drawer, didn't attempt any matching of any sort, yet it worked perfectly.
The schematic has oddities that deserve explanations:
C4 and C5 compensate the negative capacitance generated by M1.
The feedback network is split in two sections: R31/R32 and R30/R4. With a single network, the feedback resistor would need to be quite large if the input impedance has a civilized value, like 10K.
With a large resistor, stray capacitances can have unpredictable effects, which are neatly avoided here.
D15 generates a voltage transmitted by D16 to the "memory" circuit, precharging it.
In cold start conditions, with a large signal applied, M3 is unable to conduct sufficiently to satisfy the FB loop and M1 becomes saturated, leading to an overcurrent in D7 and D8 and the protection diode D9..
M3 is not controlled directly by the signal: it is slave to the upper transistor, via Q12, Q13 and Q14, and if M2 is off, M1 can conduct as much as wants it cannot make M3 conduct if the Vth eraser is not ready.
The precharge voltage is unsufficient to make M3 conduct, but it can as soon as an additional stimulus is added
This is the circuit with a BJT instead of M1: the Vth eraser has been shorted:
This is the 10kHz trangle response, just under the clipping:
The same, clipping:
Squarewave response, also 10kHz:
The measurements were made on this circuit:
I also include a simulation file, but it is not up to date: simulation and reality diverge significantly with this type of circuit
In short: an oddity.
It is based on the Tandem topology, which has been evoked here: https://www.diyaudio.com/community/...here-is-the-legacy-thread.387391/post-7059293
I have already described a Tandem-based amplifier: https://www.diyaudio.com/community/threads/tandem-based-amplifiers.388400/post-7074596 but it was essentially a showcase and a test-bed for the concept: the VAS was simply an operational amplifier, thus limiting the power to 10~20W, since HV opamps like the LM143 have mostly disappeared.
It could certainly be used though, and for domestic applications the power is ample enough.
However, DIYaudio members prefer something more substantial, and here it is: the front-end is now completely discrete, meaning the rail voltages can be as high as necessary.
The tandem topology has been adapted to MOS (mostly by Minek), and a clever trick overcomes the limitation caused by the threshold voltages.
The Vth-erasers are simply voltage-memory circuits inserted in series with the gate, to reduce or cancel the threshold voltage, changing the MOS into a zero-threshold type. The circuits themselves are extremely simple: a capacitor paralleled with a shunt-regulating device (LEDs in this case), and fed by a large value resistor.
In principle, the concept could be used in any other amplifier (and I have done it in the Circlomos), but with "normal" amplifiers there is a difficulty: the voltage needs to be very stable and accurate because it will influence the quiescent current.
By contrast, the Tandem stage has its quiescent current tightly controlled by a feedback loop, and the only effect of a non-optimal voltage is a tiny reduction of the output swing: not a big deal.
Unfortunately, MOS transistors do not shine in the tandem topology: with the original semi's line-up, I couldn't bring the THD below 0.85%, even with the tweaks at their optimum. M1 was a IRFD9120 (which explains the 4-pin socket).
With a BSP92 or even a BJT (2N5401), this was reduced to 0.25%.
Better, but a far cry from the BJT tandem: 0.004%.
The inferiority of the MOS version is probably down to the numerous parameter mismatches: a BJT is characterized by the BE PN junction, which becomes a NP junction for the correction transistor, and there is relatively little wiggle room outside of the fundamental exponential V-to-I relationship.
With MOS transistors of different sizes and polarirty, things become much more complicated. It is probably possible to improve the matters by hand-picking transistors having nicely scaled parameters, but I didn't go that far.
Anyway, in this case it does not matter very much, even with the worst-case 0.85%.
The front-end has a huge open-loop gain (almost half a million), and a relatively mediocre THD: between 1.5 and 2%. This THD will dominate, because there is no definite addition rule for THD: in theory, perfectly coherent distortions could add arithmetically, or anti-coherent distortions could even cancel one another (error-correction situation), but such situations only happen when they are deliberately planned for.
In normal cases, you are somewhere in-between. When lots of random processing blocks are cascaded, the end result will tend towards the root of the sum of squares, but in simpler cases, it could be anything but will generally be close to the largest value, in this case ~1.7%.
When the loop is closed, this value will be reduced by the loop-gain, which is substantial, and results in a final THD figure of ~3ppm, thus quite good, but not enough to qualify as a "super-amplifier".
About the front-end:
It could raise eyebrows: it is based on a raw, undegenerated diamond structure, which looks risky and brutal. Howevever, because of the GNFB, Q3/Q4 and Q7/Q8 are forced to have the same current, and the rest of inequalities only have a minor effect.
In practice, it works like a charm: I picked the transistors at random from the drawer, didn't attempt any matching of any sort, yet it worked perfectly.
The schematic has oddities that deserve explanations:
C4 and C5 compensate the negative capacitance generated by M1.
The feedback network is split in two sections: R31/R32 and R30/R4. With a single network, the feedback resistor would need to be quite large if the input impedance has a civilized value, like 10K.
With a large resistor, stray capacitances can have unpredictable effects, which are neatly avoided here.
D15 generates a voltage transmitted by D16 to the "memory" circuit, precharging it.
In cold start conditions, with a large signal applied, M3 is unable to conduct sufficiently to satisfy the FB loop and M1 becomes saturated, leading to an overcurrent in D7 and D8 and the protection diode D9..
M3 is not controlled directly by the signal: it is slave to the upper transistor, via Q12, Q13 and Q14, and if M2 is off, M1 can conduct as much as wants it cannot make M3 conduct if the Vth eraser is not ready.
The precharge voltage is unsufficient to make M3 conduct, but it can as soon as an additional stimulus is added
This is the circuit with a BJT instead of M1: the Vth eraser has been shorted:
This is the 10kHz trangle response, just under the clipping:
The same, clipping:
Squarewave response, also 10kHz:
The measurements were made on this circuit:
I also include a simulation file, but it is not up to date: simulation and reality diverge significantly with this type of circuit
Attachments
For Sale Neurochrome Differential Preamp, 8 x 2, with input selector board, all fully built.
- Swap Meet
- 27 Replies
Hello,
I'm presently unemployed and am clearing out my extra audio gear.
For sale is a fully built Neurochrome Differential Preamp. 4 stereo diff inputs, 1 stereo diff output. Tom calls this the 8x2. Included is the built input selector board. LEDs were purposely kept long in for the right enclosure which I never made. Haven't used it since about 2017 but it worked fine when put away for storage, so last I knew it worked perfectly.
I've been soldering professionally for 30 years so please have confidence that the build quality is good.
$250 plus shipping from 63025.
I'm presently unemployed and am clearing out my extra audio gear.
For sale is a fully built Neurochrome Differential Preamp. 4 stereo diff inputs, 1 stereo diff output. Tom calls this the 8x2. Included is the built input selector board. LEDs were purposely kept long in for the right enclosure which I never made. Haven't used it since about 2017 but it worked fine when put away for storage, so last I knew it worked perfectly.
I've been soldering professionally for 30 years so please have confidence that the build quality is good.
$250 plus shipping from 63025.
A tip for PCB connectors
- By Pitrus
- Construction Tips
- 13 Replies
Hi all
Problem ... I want to eliminate the hateful wirewrap wiring in an electronics of the 70s by replacing them with connectors that are more congenial to me but above all more practical, there is enough space to change them with something else so my attention has focused on two models that I have at home and with the same pitch (5mm.) to what I will replace.
The wire wrap connections have been placed everywhere in the electronics that I have on hand but it is in the preamp section that is from the tone controls board to the RIAA equalization to the line section that I am in doubt ... for all the rest I have already done and replaced but for now not wanting to influence the recommendations I will not indicate what my choice fell on ... the cables to be connected are 24 AWG.
Solution ... I have 2 types of terminal blocks
like this vertical and if it is the case also at 90 °
This....
or like this JST-XH that allows you to remove faster the connections in case of assistance
for the Jst-Xh I should only cut the "even" feet to insert them in the pcb due to the 5mm spacing. instead of 2.50 but that's not a problem, it cuts easily.
Which of the two would you choose and why? Advantages and advantages?
Problem ... I want to eliminate the hateful wirewrap wiring in an electronics of the 70s by replacing them with connectors that are more congenial to me but above all more practical, there is enough space to change them with something else so my attention has focused on two models that I have at home and with the same pitch (5mm.) to what I will replace.
The wire wrap connections have been placed everywhere in the electronics that I have on hand but it is in the preamp section that is from the tone controls board to the RIAA equalization to the line section that I am in doubt ... for all the rest I have already done and replaced but for now not wanting to influence the recommendations I will not indicate what my choice fell on ... the cables to be connected are 24 AWG.
Solution ... I have 2 types of terminal blocks
like this vertical and if it is the case also at 90 °
This....
or like this JST-XH that allows you to remove faster the connections in case of assistance
for the Jst-Xh I should only cut the "even" feet to insert them in the pcb due to the 5mm spacing. instead of 2.50 but that's not a problem, it cuts easily.
Which of the two would you choose and why? Advantages and advantages?
Soekris R2R board into ANK DAC
- By galyons
- Digital Source
- 9 Replies
I have been experimenting replacing the digital board in my ANK DAC2.1B with the DAM1021 R2R board from Soekris. I am primarily an analog guy, (vinyl and R2R tape), but have been enjoying streaming music from Qobus for a couple of years now. The ANK DAC2.1B, with CS8412 receiver chip and AD1865 DAC chip, is limited to 96/24 streams. Additionally the AD1865 is a 16 bit chip, designed for Redbook. I recently got a good deal on an ANK DAC4.1 Signature, so thought I would play around with the 2.1.
Physically the swap is a straight forward board switch out. I did have to put a small transformer circuit on the SPDIF RCA input, but it is quite simple. The ANK digital power supply feeds the Soekris board. The output from the DAM1021 is fed to the I/V transformers, the the 6922 tube output. to Dueland cast copper output caps. So it was really just desoldering and resoldering the various leads. The result? Well it sounds damn good. But way TOO MUCH good! The DAM1021 has a raw output of 1.4 volts and the ANK DAC a gain of approximately 28. I turned the volume way down on my preamp to get a listenable level, but decided to reduce the gain on the DAM1021 to avoid issues downstream.
The Soekris DAM1021 allows a few ways to reduce gain. One can add a pot and reduce the voltage, therefore reducing the gain. You can reduce gain via the filter files and you can reduce gain via the board system management, I tried the pot. It worked, but the new pot that I received was scratchy and has some dropouts in the resistive strip. Not wanting to battle that, and not fully understanding the system user interface, I just padded down the analog output with a voltage divider on each channel. Not elegant, not technical, but it worked.
I have been listening for a couple of weeks now. I am really enjoying the musical reproduction and the ability to listen to new music, (new to me!) on Qobuz at the higher resolution rates. Too early to do a comparison to the DAC4.1. I still need to sort the final gain solution and try different filters on the Soekris board. but this has been a fun start to the journey!!
Cheers,
Geary
Physically the swap is a straight forward board switch out. I did have to put a small transformer circuit on the SPDIF RCA input, but it is quite simple. The ANK digital power supply feeds the Soekris board. The output from the DAM1021 is fed to the I/V transformers, the the 6922 tube output. to Dueland cast copper output caps. So it was really just desoldering and resoldering the various leads. The result? Well it sounds damn good. But way TOO MUCH good! The DAM1021 has a raw output of 1.4 volts and the ANK DAC a gain of approximately 28. I turned the volume way down on my preamp to get a listenable level, but decided to reduce the gain on the DAM1021 to avoid issues downstream.
The Soekris DAM1021 allows a few ways to reduce gain. One can add a pot and reduce the voltage, therefore reducing the gain. You can reduce gain via the filter files and you can reduce gain via the board system management, I tried the pot. It worked, but the new pot that I received was scratchy and has some dropouts in the resistive strip. Not wanting to battle that, and not fully understanding the system user interface, I just padded down the analog output with a voltage divider on each channel. Not elegant, not technical, but it worked.
I have been listening for a couple of weeks now. I am really enjoying the musical reproduction and the ability to listen to new music, (new to me!) on Qobuz at the higher resolution rates. Too early to do a comparison to the DAC4.1. I still need to sort the final gain solution and try different filters on the Soekris board. but this has been a fun start to the journey!!
Cheers,
Geary
DIYA discovers time travel
- By StevenCrook
- Forum Problems & Feedback
- 2 Replies
Not sure if this is a problem or configuration, but it did make me laugh.
Can anyone tell me what this is?
- By krola
- Everything Else
- 2 Replies
I got this picture from a friend that told me it was of a First Watt J2.
It does not look like any other pictures of a J2 that I have seen, but it says First Watt Power on the red circuit boards
Any ideas?
Thank you
Kris
It does not look like any other pictures of a J2 that I have seen, but it says First Watt Power on the red circuit boards
Any ideas?
Thank you
Kris
Pascal u-pro2s help
I want to use the wake-on-music function of pascal u-pro2s.I find some information on the data sheet but I can not get the application manual.deos anyone have it?could you share with me? Thanks!
Input selector board with LCD/IR and motorized pot
- By jtmsrl
- Construction Tips
- 3 Replies
Attachments
Maslow CNC cuts 4x8 sheet of plywood
- By CharlieLaub
- Equipment & Tools
- 6 Replies
Wow, this could really help me, because I am someone who is very unskilled at woodworking! Precision is about 1/32" inch everywhere, and in the middle of the sheet it is more like 1/64" precision. Not expensive. Can process an entire 4x8 foot sheet of plywood! On the downside, it's very slow. But I am not in a hurry.
This would nicely tuck away to one side in my garage when not in use.
Has anyone bought or used this, or has any good first or second hand info on it?
CNC - Maker Made
This would nicely tuck away to one side in my garage when not in use.
Has anyone bought or used this, or has any good first or second hand info on it?
CNC - Maker Made
Is there counterpart to this rectifier part so I can create a bridged rectifier with 2 TO-2xx pieces?
- By mrjayviper
- Parts
- 9 Replies
So I was browsing digikey and came across this rectifier.
I tried search the catalog for the "other half" (to make a bridged rectifier) but I cannot find it. Is this specifically designed for a full-wave rectifier?
Thanks in advance.
I tried search the catalog for the "other half" (to make a bridged rectifier) but I cannot find it. Is this specifically designed for a full-wave rectifier?
Thanks in advance.
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Locked
A moan about the price of components (drive units) going up.
- By westsounds
- Multi-Way
- 11 Replies
Spare part for Luxman L-230 amplifier case?
- By jamesblonde
- Solid State
- 3 Replies
Hi everyone. I have a Luxman L-230 amp which works perfectly but when I bought it, the front panel end cap on the right side was missing (see part shown in red).
Any idea where I could get a replacement? I could wait to find a dead amp going cheap locally and raid it for parts but i) that could take a long time and ii) knowing me I would prefer to fix the old amp than raid it for parts 😊
Searching Ebay many times hasn't turned up anything. Does anyone know of the equivalent of a car scrap yard for audio gear?
Any idea where I could get a replacement? I could wait to find a dead amp going cheap locally and raid it for parts but i) that could take a long time and ii) knowing me I would prefer to fix the old amp than raid it for parts 😊
Searching Ebay many times hasn't turned up anything. Does anyone know of the equivalent of a car scrap yard for audio gear?
any ideas how it was able to get a V+ and V- using 1 bridge rectifier?
- By mrjayviper
- Power Supplies
- 6 Replies
as above. (pics is from a PCB from aliexpress) Thanks in advance! 🙂
