On the bench is an LM4610 based preamplifier board. I put it through a few tests to check the performance. Seems to be in the $18 - 25 range on eBay fully assembled. Watch to see if the board is worth your time.
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Man, when you first showed the signal on the Oscilloscope, I had no problem seeing the high hz crap from the power supply rolling along the 1000hz signal. Need some 10uf caps on the power supply. Unless that was an artifact of the Scope. Good luck with your dad. Been there, done that. We're all pulling for you here.
John ...please do more vids on transistor based amplifiers like single and dual rails power supply(doesn't have to be hi watt amps). And explain (in theory) how these amps really work. Your Darlington video made me want to learn more for you. Thanks John 😁
"The LM4610 is a DC controlled tone (bass/treble), volume and balance circuit for stereo applications in car radio,. TV and audio systems. It also features National's 3D-Sound Circuitry which can be externally adjusted via a simple RC Network. An additional control input allows loudness compensation". the link to the datasheet. it explains a lot about why this board sounds the way it does. pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/LM4610.pdf
That was exactly my thought. Someone may have thought that a "volume" control needed a audio taper. But since this is voltage control, the taper might be handled on the chip.
Some of the clone NE5532 have a lot of noise. I suspect they're not actually ne5532 but some older opamp design or just seconds that didn't make spec. Be interesting to swap the opamp for a know good one and see what happens to the hiss.
Tone controls lower the output. It is necessary to give yourself headroom for boosting certain frequencies. This is only necessary if you want the center of each pot to be 'no change'. That op amp is there just to boost the voltage back up to line level. It also acts as a buffer though, to keep the load impedance on the ic consistent and not variable based on the impedance of the amp you plug into.
Greetings: Before you go, I could not help but suspect that the volume pot is linear taper instead of logarithmic (audio taper). You can check with an ohmmeter seeing if the resistance at wiper centered is equal between wiper and ground and wiper and max. I haven't checked the chip spec's to see what it expects for input, but if you use an external log pot wired across.the existing one and only replace the original wiper connection with the new one, you should have more audio level before the midpoint. Hope this helps.
NICER preamp... Most of the 'usual suspects' gear does not have either, or both, the balance. contro and a loudness contour circuit. All we really need for automotive use is an inverter(i use a yuan jing 80 watter) to run the 5532 i.c. All i really would like to see added is an input selector switching arrangement. Best wishes for your dad & you.. God bless. BRIAN.
Normally i use 17-0-17@0.5A transformer then bridge rectifier then capacitors(2200uF each rail) Then 7815 and 7915 _ then de-coupling capacitors on the op-amp (1 for each channel) .. When i had 7812 -7912 with 12-0-12 . 100hz noise is picked up- So to get 15vdc i use 17vac and keeps the noise a low _
I wonder how that chip compares to the older LM1036N. Probably changing the gain resistors on the op amp would increase the output and change the position on the volume control
Some types of NSC's audio chips need exactly 10nF bypass caps on its supply and control lines to eliminate hiss noise. Any type of 10nF cap works well. Cheers from Indonesia
I'm breadboarding a guitar preamp for a chip power amp. Doing my head in.. I'm converting a circuit I found online for a solid state Marshall amplifier, with split 15v, and trying to convert to single 12v supply...first stage seems ok, but not getting voltage correct from the 2nd..tried powering Vdd/2 on non inverting and inverting, swapping stuff..must have killed half of a tl072. I hate it when I can't get something to work..my life is a misery untill its fixed :) gonna go watch some of our older preamp vids..think you did one using ne5532's...maybe that can point me the right path
Doug Self developed a pretty nice tone control preamp. Not sure about boards or a kit for it. It won't be cheap. I'm an audio minimalist. The only control my amp has (besides a power switch) is a volume control. Sound engineers will tell you the tone controls, or better yet, an equalizer, are great for correcting speaker frequency response issues or to an extent, room acoustics problems. They are correct. However, I found a set of speakers that, imho, need no correction and my room acoustics are good enough (but far from perfect) for me.
Yesterday I ordered components to built and test a preamp circuit I found. It uses a TDA1524A. Any toughs on that chip ? Hope the surgery went well. How's your dad ?
I don't have any experience with that chip but it is probably quite similar. The surgery went well and he is in ICU. He will be moved to a room soon for a few more recovery days in the hospital.
Glad to hear that the surgery went well and hope that your dad makes a speedy recovery. Man can't believe the noise that thing maks. somewhere there is a grounding problem with all that induced hum. Would like to see a vid on you sorting out some of those issues with it.
john smith On the schematic I have, there is already a 220nF polypropylene capacitor on pin 3 of the IC. I've seen another schematic that uses a 100nF cap. Do you suggest I add a 47-100uF or replace the 220nF by a 47 or 100nF cap ?
Thanks man for the video, what will works better in this circuit, 2x 3300 25V capacitors or 2x 2200 35V capacitors? I will imput a 32V 1.5 amp power supply.
it would be nice if i knew what your looking at and were to get it however in this case i dont think i would want one. WHAT IS YOUR OPINION OF TUBE AMPS. i think anything that has a tube is insane but im no expert. have you considered making a video on how to build a really expensive pre amp board. HEATH-KIT use to sell such things im sorry their gone have you thought about replacing them.
Wondering about your thoughts on the exact cause of the power supply hum - I've built a couple of these types of kits, oddly they too came from "Banggood" too, seems like the hum thing is a common thread, even seen it mentioned in a few customer reviews - I've played around a bit with different filter caps and been able to make some improvements but I definitely haven't found the cure. Thanks, enjoyed your vid.
I think that the AC circuit is too close to audio signals. I prefer boards that do not have the integrated rectifying circuit - there are plenty of separate power supply boards available that can be positioned close to the transformer.
@@skip1835 Generally between 470nF to 1uF for higher power amplifiers. Say 680nF to 1uF for P.A./ Musician amplifiers of 100w or greater. A 100nF to 220nf would probably do for this pre-amp board.
Any opinions on using laptop chargers for powering those cheap class d boards from china? I have a tda7492 board you've reviewed in the past, and im using a 27v transformer with a rectifier and a buck converter to power it with 20V DC and it would be much easier and cheaper to use one of those laptop power bricks instead.
JohnAudioTech thanks for the reply. Noise is what i'm most concerned about, already had to modify the gain because of high noise when no input was connected, and many audiophiles bash switch mode power supplies saying they are too noisy, but i had no issues using buck or boost converters for powering audio amps.
JohnAudioTech+ I wish and pray for your fathers speedy recovery, I had a 4 way Bypass so I know it's not a easy comeback. Before my operation they either lied to me or something went wrong. They told me I'd be up and running in no time, but in recovery they said it will not be the same and they weren't lying then, but I believe you'll be surprised when you start getting into the high powered amps. How could we have fixed that hiss and noise on this board?
It is like the "stereo wide" effect used on old boomboxes. It takes any difference between the two channels and sends it to the speakers out of phase. It usually doesn't effect the bass. Because stereo recordings often have a lot of reverb added to vocals and some instruments, it can sound like a reverb effect.
I bought few days ago a simple TPA3118 amp and if i pause the music my amp makes buzz noise, also noise become stronger when i touch phone screen. Any tips how to fix ground or add some components?
AS PER DATASHEET PAGE 28 =Grounding - The PVCC decoupling capacitors should connect to GND. All ground should be connected at the IC GND, which should be used as a central ground connection or star ground for the TPA3116D2. doesnt matter the part number all amp ic's use this as "standard configuration"
