Yes it is still PFFB, jumpers are beside the input coupling caps. Bi-polar supply on the opamp is still being used, hence the large SMT component count for the switching and post regulators which occupy more than half of the front end section (leftmost part on the preview pic) and is responsible for higher BOM cost.
Got my Motu UltraLite MK5! =), even with JLE Interface (INA1651+LME49720) on the loopback chain, it can push up to -110dB THD+N with 7.5Vrms out. (the MK5 had replaced my Loxjie D30 + cosmos ADC setup).
Quite more expensive but it makes a simpler and easier setup than using a separate signal generator + ADC.
The ultralite MK5 uses a switching power supply, I'll try to connect it to a power bank to reduce the mains pickup.
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Moving all the measurement equipment away from the mains socket reduced the 60hz pickup while still using the included 15V wall wart supply from the Motu UL MK5. Will try 4*18650 series on the MK5 next time.
I lowered the resistance value of the voltage dividing input resistors feeding the INA1651 which drastically reduced the THD (at the expense of lower input impedance and resistor divider dissipation, thus only up to 60Vrms can be measured) The resulting loopback performance is just 3dB shy of the DAC performance of Motu UL MK5 measured by ASR (attached 2nd pic). Doing some revisions on my JLE interface, will try to add relay on the input to limit the current if an accidental large voltage was entered on DIV1 setting, will check if the TPD2E007 can handle the initial peak dissipation.
I lowered the resistance value of the voltage dividing input resistors feeding the INA1651 which drastically reduced the THD (at the expense of lower input impedance and resistor divider dissipation, thus only up to 60Vrms can be measured) The resulting loopback performance is just 3dB shy of the DAC performance of Motu UL MK5 measured by ASR (attached 2nd pic). Doing some revisions on my JLE interface, will try to add relay on the input to limit the current if an accidental large voltage was entered on DIV1 setting, will check if the TPD2E007 can handle the initial peak dissipation.
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Next version of Sylph-D100 will have a -100dB THD+N performance into 5W 4ohm (using opa1656 in a socketable opamp buffer section). Gain is 14dB so it needs a preamp or a 4Vrms output balanced DAC to reach the clipping power.
Maybe the cheapest way to get an amplifier that crosses 100dB SINAD at 5W 4ohm! Sound is also optimized so it's not just about SINAD.
We'll be opening a pre-order sale some time in April, stock is only around 30pcs (next stock of TPA3251 at Mouser is around June)
With OPA1656, price will be slightly higher, than without opamp.
https://www.sylphaudio.com/product/sylph-d100-tpa3251-stereo-amplifier-module-ready-to-run
Kindly message us at support@sylphaudio.com if you are interested so that we can put you in a queue.
Pic of version 1 (version 2 is almost the same except that PFFB jumpers were removed on the top side, input pin assignment was changed to match xlr numbering)
Maybe the cheapest way to get an amplifier that crosses 100dB SINAD at 5W 4ohm! Sound is also optimized so it's not just about SINAD.
We'll be opening a pre-order sale some time in April, stock is only around 30pcs (next stock of TPA3251 at Mouser is around June)
With OPA1656, price will be slightly higher, than without opamp.
https://www.sylphaudio.com/product/sylph-d100-tpa3251-stereo-amplifier-module-ready-to-run
Kindly message us at support@sylphaudio.com if you are interested so that we can put you in a queue.
Pic of version 1 (version 2 is almost the same except that PFFB jumpers were removed on the top side, input pin assignment was changed to match xlr numbering)
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Sylph-D100 (version P02) Initial power test looks good, it can get unclipped 18Vrms at 4 ohms from 20Hz to 20kHz and is highly stable.
Right channel THD+N 5W at 4Ω using NE5332 opamp and LRS-350-36 adjusted to 37.8V DC.
Result:
-108.1dB THD
-99.6dB THD+N
The noise (+N) part will be better if OPA1656 is used, so it will reach around -100dB or better when measured by an AP system and a good load resistor.
To make the opamp socketable, we had to balance engineering trade-offs between low THD+N and using larger resistor values. We chose larger resistor values as the opamp buffer layout uses only a 2-layer board, and sockets for the opamp, the THD will be good but the noise will be higher.
Using low-value resistors (like 1K ohms for feedback) can lower the noise floor, but if the layout is only a 2 layer board, or if the opamp is socketable, it will introduce errors due to any stray capacitance/inductance on the layout or socket which will increase the distortion (THD part).
THD+N measurements can also be affected by low-quality resistive dummy loads or if loads lower than 4 ohms is used, such as 3.5 to 3.8 ohms.
I will perform THD+N measurements next time with a low quality - resistor dummy load (to check for the worst case) and with OPA1656.
Right channel THD+N 5W at 4Ω using NE5332 opamp and LRS-350-36 adjusted to 37.8V DC.
Result:
-108.1dB THD
-99.6dB THD+N
The noise (+N) part will be better if OPA1656 is used, so it will reach around -100dB or better when measured by an AP system and a good load resistor.
To make the opamp socketable, we had to balance engineering trade-offs between low THD+N and using larger resistor values. We chose larger resistor values as the opamp buffer layout uses only a 2-layer board, and sockets for the opamp, the THD will be good but the noise will be higher.
Using low-value resistors (like 1K ohms for feedback) can lower the noise floor, but if the layout is only a 2 layer board, or if the opamp is socketable, it will introduce errors due to any stray capacitance/inductance on the layout or socket which will increase the distortion (THD part).
THD+N measurements can also be affected by low-quality resistive dummy loads or if loads lower than 4 ohms is used, such as 3.5 to 3.8 ohms.
I will perform THD+N measurements next time with a low quality - resistor dummy load (to check for the worst case) and with OPA1656.
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Regarding the sound of the latest Sylph-D100 with OPA1656, it has softer highs and better details than my KGUSS MA12070, and fuller midrange sound than my Topping PA5 as well as better sparkling highs. Also, it can get 100W at 4ohms if driven by 38VDC supply. I really think it can compete with the best amps out there.
I've opened the sale for the first 5pcs here which can be shipped by early next week, we will ramp up the production once we got all the parts required (ETA 1 month):
https://www.sylphaudio.com/product/sylph-d100-tpa3251-stereo-amplifier-module-ready-to-run
I've opened the sale for the first 5pcs here which can be shipped by early next week, we will ramp up the production once we got all the parts required (ETA 1 month):
https://www.sylphaudio.com/product/sylph-d100-tpa3251-stereo-amplifier-module-ready-to-run
We actually have opened the slot for 16 units which were already sold out, it will be shipped by batch on March 31, April 3, and April 7.
Next pre-order sale would be on April 24 (ship out date after 1 to 2 weeks).