Rev. 2.3 boards arrived via FedEx yesterday.
Rev. 2.3 uses the THAT1200 for the differential receiver, LME49720 for the error correction circuit, OPA2277 for the DC servo, and LM3886 for output power. All parts are through hole (PTH, leaded) parts for easy of DIYing.
The unused channel in the LME49720 is configured as a buffer with its input tied to ground. Within the audio band, Rev. 2.3 is identical to Rev. 2.2. Outside the audio band there are two changes: I added a pole in the EMI/RFI filter, so Rev. 2.3 has a bit better EMI/RFI immunity. Also, I used my newfangled custom wound inductor in the Thiele Network (output L||R). This makes the Thiele Network a lot easier to assemble and also allows folks to purchase the inductors ready made if they desire.
The documentation will undergo a major rewrite as it's getting a bit long in the tooth. My plan is to tighten it up and make it easier to find the relevant information while also provide sufficient detail on the inner workings of the circuit that folks can appreciate the engineering behind it.
The first boards shipped today and I expect to have the documentation ready by the time they reach their destination.
Tom
Rev. 2.3 uses the THAT1200 for the differential receiver, LME49720 for the error correction circuit, OPA2277 for the DC servo, and LM3886 for output power. All parts are through hole (PTH, leaded) parts for easy of DIYing.
The unused channel in the LME49720 is configured as a buffer with its input tied to ground. Within the audio band, Rev. 2.3 is identical to Rev. 2.2. Outside the audio band there are two changes: I added a pole in the EMI/RFI filter, so Rev. 2.3 has a bit better EMI/RFI immunity. Also, I used my newfangled custom wound inductor in the Thiele Network (output L||R). This makes the Thiele Network a lot easier to assemble and also allows folks to purchase the inductors ready made if they desire.
The documentation will undergo a major rewrite as it's getting a bit long in the tooth. My plan is to tighten it up and make it easier to find the relevant information while also provide sufficient detail on the inner workings of the circuit that folks can appreciate the engineering behind it.
The first boards shipped today and I expect to have the documentation ready by the time they reach their destination.
Tom
Attachments
Is there a preassembled option? I am running behind on all the work an excitement...
I have two in stock right now. They're on my website. Once they're gone, I'll probably remove the "fully assembled" option. I need to use these for my own testing, so whoever ends up buying will get the best characterized Modulus-86 R2.3 around.
I plan to keep the MOD86 going as a DIY product for as long as practically possible. I'll nudge those who prefer fully assembled modules in the direction of the Modulus-286 R2.0 (when available) and Modulus-686.
Tom
Since I was measuring the Modulus-86 Rev. 2.3 anyway, I thought I'd address a few common questions regarding the MOD86 and switching power supplies.
Below are the THD+N vs output power for my HP 6643A lab supply (actually two of them to form ±30 V) and the Connex Electronic SMPS300RE. If anything, the performance with the SMPS300RE is actually better than with the well-regulated power supply.
The plots that do not show the power supply in the title are with the HP lab supply.
Another common question is the damping factor. For Rev. 2.3, it's a bit over 1900 at 1 kHz. Drops to 660 at 20 kHz.
Rev. 2.2 and below should have slightly lower DF as they use more turns in the output inductor. If I was to guess, I'd estimate a DF around 400 (20 kHz); 1200 (1 kHz) for those.
Needless to say, your speaker cables and connectors will have a greater influence on the DF than the amp.
Tom
Below are the THD+N vs output power for my HP 6643A lab supply (actually two of them to form ±30 V) and the Connex Electronic SMPS300RE. If anything, the performance with the SMPS300RE is actually better than with the well-regulated power supply.
The plots that do not show the power supply in the title are with the HP lab supply.
Another common question is the damping factor. For Rev. 2.3, it's a bit over 1900 at 1 kHz. Drops to 660 at 20 kHz.
Rev. 2.2 and below should have slightly lower DF as they use more turns in the output inductor. If I was to guess, I'd estimate a DF around 400 (20 kHz); 1200 (1 kHz) for those.
Needless to say, your speaker cables and connectors will have a greater influence on the DF than the amp.
Tom
Attachments
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Modulus-86_R2p3_DampingFactor.png -
Modulus-86_R2p3_OutputImpedance.png -
Modulus-86 Rev. 2.3_ THD+N vs Output Power, Power Supply (8 ohm, 20 kHz BW).PNG -
Modulus-86 Rev. 2.3_ Harmonic Spectrum (40 W, 8 ohm, 1 kHz).PNG -
Modulus-86 Rev. 2.3_ Harmonic Spectrum (40 W, 8 ohm, 1 kHz, 1M FFT, 4 averages, SMPS300RE).PNG -
Modulus-86 Rev. 2.3_ Harmonic Spectrum (1 W, 8 ohm, 1 kHz, 1M FFT, 4 averages).PNG -
Modulus-86 Rev. 2.3_ Harmonic Spectrum (1 W, 8 ohm, 1 kHz, 1M FFT, 4 averages, SMPS300RE).png
As most of you know, output impedances of most dynamic loudspeakers hit nadirs below 1khz. Typically less than 500Hz. Given that we are talking about damping factors of 1200-1900 I am now all too certain that I sold my recent thru hole Modulus 86 for all too little unfortunately.
A damping factor of 1900 is 4.2 milliohms and 1200 is 6.66 milliohms folks.
Great work Tom as always!
Best,
Anand
A damping factor of 1900 is 4.2 milliohms and 1200 is 6.66 milliohms folks.
Great work Tom as always!
Best,
Anand
Thank you.
Just dawned on me that I forgot to attach the residual hum & noise plots.
The total integrated noise and hum measures 32 uV (A-weighted); 40 uV (unweighted). Same as the other Modulus-86 Rev. 2.x versions.
Tom
Just dawned on me that I forgot to attach the residual hum & noise plots.
The total integrated noise and hum measures 32 uV (A-weighted); 40 uV (unweighted). Same as the other Modulus-86 Rev. 2.x versions.
Tom
Attachments
Thanks Tom! Just finished the amp this weekend. Bought the boards many months ago, only recently realizing the lme49710 stocks were dwindling fast. Glad I completed now. I'm absolutely lovin' it.
Currently have a makeshift volume control connected it, while I'm waiting for some pcbs to come in for single ended preamp that will go through your THAT driver.
Currently have a makeshift volume control connected it, while I'm waiting for some pcbs to come in for single ended preamp that will go through your THAT driver.
Yes, that's a Mini Dissipante 2U. Transformer is the 160VA Hammond 1182n22, as the Antek AS2222 has been out of stock.
blackskull,
Nice work there with your Modulus-86 build.
Btw, I am using Tom's THAT Driver as a preamp and very happy with it.
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