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Amplifier Modules and PCBs For Sale

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Sylph-D100 repeat measurements, using OPA1656, LRS-350-36 adjusted to 38V
Motu Ultralite MK5 ADC, SMSL DO100 DAC (can drive the output up to 16Vrms)
Needs a DAC with 5Vrms out to drive the amp into 20Vrms (100W 4ohms)
Dominant 2nd harmonic due to inductor selection.

sylph-d100 5w right ch.png

left ch 5w 4r.png


Sylph-D400 5W 4ohms using Motu Ultralite MK5 DAC + ADC.
Using a better DAC can improve noise by 1dB to 2dB, so expect the actual SINAD to get around 98dB~99dB at 52V supply. (I used UL-MK5 DAC since it has better THD than DO100, the DO100 has better noise performance)

Medium gain PFFB can reach 29Vrms (210W 4 ohms) at 93dB SINAD. Onset of clipping (1% THD+N) starts at around 29.6Vrms using 52V supply.

Note that all other TPA3255 Stereo BTL variant can only reach around 160W at the onset of clipping. So Mono PBTL mode has an additional 50W unclipped power advantage.


D400 5w4r.png
 
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454Casull said:
Can you show measurements at 5 kHz and multitone as well?
Click to expand...
I can but my measurements might not be as accurate, so might as well wait till I send a sample to ASR once the preamp is available (before the year ends).
Preamp is single channel per board (4 layer), accepts single DC 24V to 55V. Buck converters to generate +/- 17.5V opamp supply rails. LM317/337 post regulators, no need to use ultra low noise post regulators. Has jumpers for SE in/out, I think 6x voltage gain is sufficient.. Selectable output resistor value (will serve as the R_IN for pffb of D100 and D400 to enable deep PFFB mode :devilish: )
 
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Deleted member 148505

JLesterP said:
Preamp is single channel per board (4 layer), accepts single DC 24V to 55V. Buck converters to generate +/- 17.5V opamp supply rails. LM317/337 post regulators, no need to use ultra low noise post regulators. Has jumpers for SE in/out, I think 6x voltage gain is sufficient.. Selectable output resistor value (will serve as the R_IN for pffb of D100 and D400 to enable deep PFFB mode :devilish: )
Click to expand...

  • Changed the design to stereo so that it can be useful for other applications. (such as bridging 4x SE irs2092 modules)
  • Voltage gain fixed to 5 (same for SE/BAL input)
  • Vertically mounted to save space (40mm * 100mm)
  • Default opamps are OPA1602(gain) + NE5532(buffer)
  • Deep PFFB for Sylph-D100 and D400, (I will also try this on a modified low gain myref)

1690309380943.png

1690310052211.png
 
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Deleted member 148505

Preamp assembled look, this looks tiny in person. Opamp voltages at +/-17.6V
14dB gain OPA1602 and 0dB gain NE5532
I can only measure around -106dB THD+N at 21.5Vrms out. (Using SE-450-48 power supply)
Will try other opamps specially OPA1612 on the gain stage.

1691078010774.png
 
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Deleted member 148505

THD+N result of the preamp using different opamps.
Setup: Motu UL MK-5 DAC 1.2Vrms out, preamp at 5.9Vrms out going to UL-MK5 ADC.

UL-MK5 DAC+ADC loopback @1.2Vrms
1.2V loopback.png


Preamp with OPA1612 + OPA1602
opa1612+opa1602.png


OPA1612 + OPA1656 has 2dBc worse N (wasn't able to capture)

Preamp OPA1656 + OPA1602
opa1656+opa1602.png



I tried deep PFFB mode, the performance is very picky on the proximity and wiring, so I think it's not recommended to just create a preamp and slap it to any TPA3255 module. (you might get worse SINAD than a non-PFFB amp depending on the wiring). It's doable but you need to have a measurement equipment to optimize the wiring / connections.
 
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Deleted member 148505

JLesterP said:
THD+N result of the preamp using different opamps.
Setup: Motu UL MK-5 DAC 1.2Vrms out, preamp at 5.9Vrms out going to UL-MK5 ADC.
Click to expand...
Measurements are at 14dB gain, I should have measured it at 0dB gain, just like preamp measurements on ASR.

Preamp 1’s initial sound tests were good; the sound is transparent as expected. No power on/off pop, or any noise even when the wires are (dis)connected and no hiss/hum on mediocrely wired connections. Unclipped output at 23.5Vrms BAL / 11.75Vrms SE(with +/-17.8V rails)

Will repeat the measurements at 0dB gain once I get a low distortion oscillator and a cosmos APU.

This preamp board will also serve as a base design for future projects like a linkwitz-riley crossover for biamping D400 and D100. And as a high performance gain stage for low gain power amps.
 
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rrobot

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JLesterP said:
This preamp board will also serve as a base design for future projects like a linkwitz-riley crossover for biamping D400 and D100. And as a high performance gain stage for low gain power amps.
Click to expand...
Looks really good Lester! Could the preamp board possibly also serve as an adjustable gain (dip switches?) buffer, to trim the gain structure for various active speaker implementations? Biamping is definitely a use case I have in mind.
 
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Deleted member 148505

rrobot said:
Looks really good Lester! Could the preamp board possibly also serve as an adjustable gain (dip switches?) buffer, to trim the gain structure for various active speaker implementations? Biamping is definitely a use case I have in mind.
Click to expand...
Thanks! Hmm there no final design yet, I just covered the basics on this module: balanced in/out with ultra low THD+N capability (gunning for -120dB THD+N at 0dB gain).

Volume pot, relay stepped attenuator, voltage divider dip switches, input selectors / SE to Bal buffer can be placed before this module. Will add onboard balanced to SE buffer on the production version.
 
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Deleted member 148505

I repeated OPA1656 gain stage measurements using SMSL DO100 DAC as a source.
FFT at 14dB (5x) gain. ~1.2Vrms in / ~6Vrms out
-108.7dBc or 0.0003673% THD+N,
At -1dBFS or ~10.6Vrms, it reaches -112dBc which is near the limit of the ADC.
Anyways, just posting for documentation purposes.

opa1656 + opa1602.png


SMSL DO100 to UL-MK5 loopback (~1.2Vrms) (-20dBFS relative to 12V ADC input)
do100 loopback.png
 
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Deleted member 148505

Just promoting our 3pc PCB D400 which is very easy to assemble.
Can survive 20Hz to 20kHz inductive and capacitive tests up to 2Ω load without triggering the fault circuitry. (means no hiccups on most speaker / subwoofer at full power output)
Can reach 31.6Vrms out into 4Ω at -40dBc (250W at 1% THD+N)
I think this can survive a power cube test, stable up to 2Ω which most other amps with deep PFFBs cannot achieve.

1696330205886.png

S400M P05_1 PCB legend - small.jpg

D400 assy small.jpg
 
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Deleted member 148505

yoaudio said:
Any new updates Lester?
Click to expand...
Not manufacturing the D200 yet because TPA3255 BTL PFFB mode cannot produce full power compared with non-PFFB implementation (and vs PFFB PBTL mono). My prototypes can only produce 144-156W into 4Ω with 50-51V supply (before clipping). Compared with D100 TPA3251 which can produce 100W into 4Ω with 38V supply (before clipping).

BTL stereo TPA3255 also clips earlier on 20Hz vs 1kHz tests (around 50W difference). I was able to test the stereo improved PFFB 3eaudio as well and it also behaves the same. (early clipping)

That's why I intuitively know that the Topping PA7 has a dual IC chip once I saw the ASR review, because I know the single chip stereo cannot do it. :D

So, to take advantage of higher power of TPA3255, go with PBTL single chip per ch route. Otherwise, TPA3251 power is enough.

Although I know that TPA3251 and TPA3255 have easily recognizable audible differences. So, if your preferred sound is TPA3255 and you are aware that there is a power tradeoff, BTL stereo TPA3255 with deep PFFB is also good.
 
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