Sorry for the large number of posts. but as I understand it - if you pull out the left opa1612, then there should be no sound in the left channel! why is he still there !? the same thing with the right channel! I checked - everything was soldered according to the scheme. third opa1612, legs 1, 2, 3 are used by the left channel, and legs 5, 6, 7 are used by the right channel.
Vref-L and Vref-R are derived from the AVCC voltage for each channel. They are shown in the AVCC schematic attached to post #3003 in this thread. The only thing the Vref signals are used for is in the I/V conversion opamp circuit. The Vref for each channel goes to the non-inverting input of the I/V opamps which causes their outputs to have a DC offset.
The DC offset can be removed if desired by adjusting the Vref voltage divider resistor values a little different from what is shown on the AVCC schematic.
Please check that you have Vref signals hooked up properly to the I/V opamps then let us know if there has been any change in the wheezing symptoms. If no change, then we can look into that a little deeper.
EDIT: Attached below is a pic of the bottom of my dac. The blue and yellow wires are the dac outputs that go down to the output stage board attached to the end of the dac board. The yellow wires that remain unsoldered are the Vref wires for each channel. They were soldered to the AVCC board after the pic was taken.
The DC offset can be removed if desired by adjusting the Vref voltage divider resistor values a little different from what is shown on the AVCC schematic.
Please check that you have Vref signals hooked up properly to the I/V opamps then let us know if there has been any change in the wheezing symptoms. If no change, then we can look into that a little deeper.
EDIT: Attached below is a pic of the bottom of my dac. The blue and yellow wires are the dac outputs that go down to the output stage board attached to the end of the dac board. The yellow wires that remain unsoldered are the Vref wires for each channel. They were soldered to the AVCC board after the pic was taken.
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The doc came up in another thread: FS: LynxAudio DAC D60
What I noticed was on the second page, 2nd paragraph of: https://www.diyaudio.com/forums/att...s-lynxaudio-dac-d60-dac_lynx_d60v1_en_opt-pdf
...also a schematic is down lower in the same document so you can see what power supplies the original designer was referring to.
What I noticed was on the second page, 2nd paragraph of: https://www.diyaudio.com/forums/att...s-lynxaudio-dac-d60-dac_lynx_d60v1_en_opt-pdf
...also a schematic is down lower in the same document so you can see what power supplies the original designer was referring to.
Every single monolithic regulator has sounded awful in a power amp supply IME, distinct loss of dynamics and weight.
Where an unregulated supply (just rectifier and filter caps) is an option like with high PSRR chip amps (LM3886, OPA1622) its very clear the unregulated supply doesn't have this problem. All that mains ripple on the supply has to come with a tradeoff, but it is much more slight than anyone would expect and worthy tradeoff compared to the regs.
As a test I got a couple of cheap 9V Alkalines to the power an OPA1622.
They do not have the issue of monolithic regulators, nor does it have the tradeoffs of an unregulated mains supply.
Somehow these cheap batts are the best amp power supply I've heard,
The sound has a slight ''roughness'' to it (noise?) but I expected so much worse from the most inferior battery type.
There were 3uf+0.1uf film caps on the output, thats all.
btw part of this was to see if the unregulated mains supply wasn't just creating some ''effect'' that made these amps sound more euphonic. Its seems the problem really is inherent to the monolithic series regs.
Where an unregulated supply (just rectifier and filter caps) is an option like with high PSRR chip amps (LM3886, OPA1622) its very clear the unregulated supply doesn't have this problem. All that mains ripple on the supply has to come with a tradeoff, but it is much more slight than anyone would expect and worthy tradeoff compared to the regs.
As a test I got a couple of cheap 9V Alkalines to the power an OPA1622.
They do not have the issue of monolithic regulators, nor does it have the tradeoffs of an unregulated mains supply.
Somehow these cheap batts are the best amp power supply I've heard,
The sound has a slight ''roughness'' to it (noise?) but I expected so much worse from the most inferior battery type.
There were 3uf+0.1uf film caps on the output, thats all.
btw part of this was to see if the unregulated mains supply wasn't just creating some ''effect'' that made these amps sound more euphonic. Its seems the problem really is inherent to the monolithic series regs.
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Also some more battery noise tests: http://www.hoffmann-hochfrequenz.de/downloads/NoiseMeasurementsOnChemicalBatteries.pdf
Indeed, if one can regard a regulated power source as an amplifier, then the best linearity would be expected from the ones working in A-class. The regs quiescent current should equal up to the output current for these.
Another matter might be return current termination, how close to the load. The author of the Lynx DACs, although being notorious for including “copyright protections” in the material openly released, has stated elsewhere, that it is of utmost importance to keep all more than 1kHz currents locally bypassed. So these 1R matter then.
thanks for the help Mark! everything is fine now) I can notice that the sound pleasantly surprised me) I’m listening so far on Koss Porta Pro, bought a long time ago. I know, they don’t grab stars from the sky) the next stage is AVCC using the lme 47920 and tps4700 operational amplifier. so far, everything is organized on lme337. I was lucky to be on a business trip in Japan for 1.5 months, where I purchased original parts (not all unfortunately), which are a problem in Russia, in particular in the Far East. dac registers I will edit later. will have to turn to you again for help!) took this time arduino leonardo. The chip protection board has already been purchased. but! I will organize the food at the proper level first. By the way, I like the first filter on akm4137 more.
Guys just a quick status. I know that this is not the pro version thread, but since i learnt a lot on the q2m board i thought it is a good idea to inform you too.
I bought the pro verison of the board.
Made some mods. (Not all possible: CAP. Changes Salas v1.3 PS for analog part. lme49600 based separated Avcc, ic change to lme49720/ 710)
Incredible voice.
https://www.diyaudio.com/forums/dig...pro-9038pro-mods-upgrades-22.html#post6033687
I bought the pro verison of the board.
Made some mods. (Not all possible: CAP. Changes Salas v1.3 PS for analog part. lme49600 based separated Avcc, ic change to lme49720/ 710)
Incredible voice.
https://www.diyaudio.com/forums/dig...pro-9038pro-mods-upgrades-22.html#post6033687
Congratulations on the happy outcome. Good to see you still have an interest in the diy audio hobby.
Why don't you try simple discrete BJT follower reg. If you need significant
current a darlington will work better. These can sound really good especially if
you pre load them and supply a very low noise ref for the base. If you require
more PSRR, cascode 2 of the same.
I agree, batteries just sound really good but after owning a completely
battery powered system for a period, including power amp, I would not
go back. Too much hassle.
TCD
I know this thread is not about amps and amps, but may I ask what batteries do you use for your system (DAC, pre, amps) and which section of the components are fed with battery power? Thanks.
OK, agreed, apologies for slight diversion.
Amps did run off SLA gel cells,
from memory around 10AH. There was only DAC -> Amp, passive vol control.
DAC used a hybrid SS / Tube OP stage (current conveyor type). Tube heaters
ran off SLA 6V (6.4). The heaters actually made a lot of difference. DAC
(PCM63) ran off, from memory 2 x 6V SLA's. The 'HT' was the only non
battery supply, it was LN diodes -> R C L C Filter -> simple BJT cascoded
follower reg. This was all before Li Ion became popular.
This quite a few years ago and I doubt I'll ever go back to batteries.
I think regs can sound as good, you just have to try a lot harder.
cheers
TCD
Happy New Year Mark and others!
I've finally got around to connecting the JLSounds I2SoverUSB to my AK4137 SRC board which in turn is connected to the DAC. Each in isolation (AK4137 to DAC works, JLSounds to DAC) works however I can't get a lock on the USB signal on the AK4137 board.
I've followed the instructions (soldering jumpers on the rear) for using AK DACs on I2SoverUSB but nothing.
Any thoughts?
I've finally got around to connecting the JLSounds I2SoverUSB to my AK4137 SRC board which in turn is connected to the DAC. Each in isolation (AK4137 to DAC works, JLSounds to DAC) works however I can't get a lock on the USB signal on the AK4137 board.
I've followed the instructions (soldering jumpers on the rear) for using AK DACs on I2SoverUSB but nothing.
Any thoughts?
Regarding the JLSounds USB board, just checking to make sure you have the current manual for that. For some reason they had it hidden on their website and they one the had at the download link was for the old version board. If the pictures in manual of the pin header holes look the same as on your board, then it should be the correct manual.
For my own use I have been installing the included 0-ohm SMD resistors at B1, B2, and B3.
For my own use I have been installing the included 0-ohm SMD resistors at B1, B2, and B3.
I'm pretty sure I've got the correct version of the manual, the B1,B2 & B3 for this version of the board are closed, open, closed.
Odd, I've got a somewhat sporadic output, can you confirm which pins on the H3 header need to be connected?
At present I've got:
BCLK_I2S
DATA_I2S
LR_CLK_I2S
GND
VDD
GND
I feel I need to connect these to the AK4137:
DSD_PCM_iso
MUTE_iso