Thanks.

Yes, you are correct with the "falling roof" effect where the signal appears to droop or decay over time. This is due to the capacitor's time constant interacting with the 20 Hz low-frequency signal. Thanks.

Thanks.

Thanks for the comment!

Diodes D9 and D8 are protection diodes against the back EMF generated by the speakers or inductive loads. When speakers move, they generate a back EMF-a voltage that opposes the original signal. This can potentially damage the power output transistors or cause distortion in the audio signal. If the back EMF exceeds the safe operating voltage of the power output transistors, it can lead to failure or damage. These diodes help to absorb and dissipate the back EMF, ensuring the amplifier operates properly and delivers clean audio signals to the speakers. I prefer to include them in most of my projects. Thank you for asking.

Thank you for your detailed suggestions! There are 7 RIAA preamps in this series, all built and tested using the same QA configuration. This way, we can directly compare and see which one performs better. The tests were run without tweaking the QA app to ensure impartial results. One preamp achieved an SNR of 79 dB, while the others were around or above 50 dB. Matching the preamp response to the standard curve is a great idea, but it would require redesigning or tweaking the circuit. Noted your suggestion on the linear x-axis display for frequency response. Thanks again!

@ if you load a reverse RIAA curve into the QA, it will plot a perfectly flat response if you’ve got the preamp circuit RIAA design right. When I test phono circuits (baynesaudiolabs.com) I either do this or sometimes use a physical reverse RIAA filter circuit. I wasn’t suggesting you changed your preamp circuit. Good channel which I only found today. I’ll take a look at your back catalogue. Thanks.

Yes at ±50VDC. Thanks.

Thanks.

Where is your current location?

From authorized distributors, this ensures you get genuine parts. Thanks.

Thank you. You are absolutely correct about your comment. I have mentioned how to adjust the crossover distortion issue in Project 58. I hope this will help you in your future projects.

Thanks.

Thanks for watching!

Although the prototype was designed for 8 ohms, the amplifier can also work with a 4-ohm load. This will test the ThermalTrak's ability to control bias and prevent thermal runaway. Thanks.

The versions with a 'DG' suffix are still current (OnSemi, etc) and available (DigiKey, etc), eg NJL1302DG and NJL3281DG

@kiltrash1 mfg discontinued

FYI, you can still buy them at Mouser. Thanks.

FYI, if you go to Onsemi's website, these are listed as "active" devices: NJL3281D/NJL1302D -Pd 200W, and NJL0281/NJL0302D -Pd 180W version. Thanks.

@@buildaudioamps Nice that they started mfg it again. Thanks

Thank you too for watching.

Thank you! Cheers!

Thanks.

Please refer to the schematic diagram. Test results showed otherwise. Thanks.

Totalmente de acuerdo; es un circuito elevador de tensión que, usa señal de conmutación y produce ruido ; se deben usar una power supply convencional con transformador separador, estabilitzador y filtros bobinados o bancos de baterias de 1,5V en serie, hasta obtener los 32V de trabajo. Piensenlo!

for maximalist LT3042, preregulation LM317

@@joancarlescanadas5123 My reference power amplifier is an Icepower 1000ASP, shop.icepoweraudio.com/wp-content/uploads/2023/02/ICEpower1000ASP_Datasheet_1_7.pdf. It does not have a transformer, but is an audiophile professional high quality power amplifier. Thanks.

Thanks

Thank you!

Thanks. BOM is always available free by email request at [email protected]

Ok, thanks.

I'm using an adjustable DC-DC high voltage boost module. You can adjust the input voltage from 8-32VDC to an output of ±45-390VDC. Maximum output current is 200 mA and idles at 15 mA. Thank you.

Those are the recommended load impedance and capacitance from the MM cartridge manufacturer. The AT-VM95C/H that I use, Audio Technica recommends Rl at 47K and Rc from 100 pF to 200 pF. Those values will depend on what MM cartridge you are using.

@@buildaudioamps Thanks, I use a ATVM95E (Audiotechnica) capsule. I suppose that the CL value, between 100pf and 200pf may be appropriate!

@@joancarlescanadas5123 That is correct. Thanks.

@@buildaudioamps Thank you!👍👍👍👍

Thanks.

Thank you, and your suggestion is exactly the best method to create a better PCB layout. However, for a single home-built prototype, it's just impractical. I understand that the prototype has its limits, but the bottom line is that I must share with you and others my music listening experience with it. Listening to various old recordings of vinyl LPs, continues to amuse me with the sound quality it reproduces. It's a simple design that required little effort to build.

@@buildaudioamps it's really not impractical, even if you want to etch the board yourself (which I don't know why you would but fine), you can get a two layer board and use the top side for signal and the bottom side for ground. You can also order it from companies like PCBWay, JLCPCB, etc. A solid ground plane is a must if you're doing any kind of sensitive analog project.

@@InTimeTraveller Thank you.

All resistors are 1% metal film, purchased from a reputable authorized parts online dealer close to home in Texas. Thanks.

The entire prototype is being tested by the audio analyzer, so that's the overall raw test result for THD, THD+N and SNR in stereo.

The project was built according to the schematic diagram on Figure 7 of the Burr-Brown's OPA37 application note SBOS135C. The given RIAA network component values were left unchanged from their original design. I apologize, but the audio analyzer's frequency response test produced that result. Subjectively, the music listening test is satisfactory or excellent while using several MM cartridges on different vinyl LPs. Thank you.

It looks like this because the scale is incorrect, the X axis should use the logarithmic scale. Minor deviations could be caused by loose component tolerances

@@yeoldestuff There is no lin/log option when you run an FR test on the UUT. QuantAsylum's QA400 will output a sweep AF range and displays the result endlessly. All resistors in the prototype are using 1% metal film and affordable 10% film capacitors. Brown-Burr calculated the RIAA network values for us to build, as is. Thanks.

Thank you for your comment.

Thank you for your comment. Smart! However, when converting your project using the OPA37, be sure to check the datasheet first for the correct pinouts of the chip. OPA37 is a single-packaged Opamp, while the popular NE5532 is dual-packaged.

I was going to ask the same question about running on 9 volt batteries have you tried running it off AC to DC transformer? What about lithium battery?

@@jedi-mic Sorry, If I may answer, I'd prefer lithium-ion cells because it will last longer.

Sorry about that; I don't sell boards. Check this out on the website buildaudioamps.com/make-pcbs/

Thanks.

Thank you for your comment. BAA has built and tested 7 RIAA MM cartridge phono preamps, which will be published on this channel as part of a presentation video series on MM cartridge phono preamps. So far, 5 preamps have already been posted and 2 more to go. The RIAA preamp project prototypes are built with active components, namely, vacuum tubes, opamps and discrete transistors. The listening test of all 7 preamps is subjective in nature; using different vinyl record albums, input and output sources, each one has different musical/tone character. Because of this, the task of determining which one is best is both challenging and intriguing. The bottom line is that the presentation video about this series is not a review but as an educational resource for DIYers to build their own phono preamp.