That's great feedback, thanks.

@@Pham-Dung You can see the updated component values at 8:30 in the video.

@@Pham-Dung Add 10uF in parallel with the existing 4.7uF

@@Pham-Dung Yes, it's all in the video.

@@Pham-Dung No, the type of opamp will not change the gain. You can watch in the video how I change the gain.

Nice work.. at $8 that's quite a lot of value for money. Cheers, Jake

Hi Pete, great to hear you get some good use out of this feature. I always wanted something to easily do some basic measurements on a phono stage as it's always been a bit of a black box. I'll add some features in the future to measure the cartridges as well, it will however require the use of a test record, but I think most of us got a few of those anyway.

Thanks, I'm happy to hear you found the upgrade a big improvement. Cheers, Jake

Thanks

The specified output voltage for MM cartridges (e.g. 5mVrms) is using a standard 5cm/sec grove at 1kHz, however records are often recorded at much higher level, that's why you have an overload factor hence it's a good idea to test at higher voltages to make sure it doesn't clip. Behringer didn't design it, they just slapped their name on it. It's the same preamp, they didn't even change the model number (pp400) Cheers, Jake

Hi, the input is between C3 and VNEG (same as GND). Cheers, Jake

Hi, 1 year later! What op-amp did you end up going with? I was wondering if it's worth adding a discreet one, e.g. from Orange.

Hi David, thanks, I ran the simulation with 75k, it will give you a small dip of around 0.4dB at 1kHz, not too bad, probably not audible. You can try the calculator on www.qsl.net/in3otd/parallr.html to easily find resistor combinations that might get you even closer to 78k. Cheers, Jake

@@TheStuffMade thankyou for the quick response and for running the simulation.

Hi, they should both work, but if you're building this I'd recommend using an 8 pin socket for the opamp so you can easily experiment with different ones, they generally have the same pinout (except special cases like the LM387). Personally I'd probably go with something a bit more modern like the LME49720. Cheers, Jake

Hello, if you remove the two 820pF capacitors (the green ones marked 821 on the board around 3:55 in the video), then you'll get a flat equalization for the treble. Or you can just lift one side of the capacitors and add a switch. Just be careful to only use the switch when your amplifier is off as it will probably generate a very large pop that could damage your speakers. But, I'm sure you are aware the curves for 78s are a bit of a jungle with so many labels using different equalization. Cheers, Jake

@@TheStuffMade That’s great - many thanks Jake :-)

Thanks, the 0603 resistors are also metal film, however you can use any resistor type you like, but it will be very difficult to solder a 1/4 W through hole resistor onto the small 0603 pads. The best way is to use 2 resistors in parallel to get something like the non-standard 78k value, use 82k in parallel with 1.5M, just solder them on top of each other, that's what I did, it gives very close to 78k. Here is a calculator to make odd resistor values: qsl.net/in3otd/parallr.html Cheers, Jake

@@TheStuffMade Thanks a lot jake, I really appreciate your response. I've been looking for 0603 resistors and the closest I could find (thanks to that site you gave me) to get the 78k value in parallel are 100k + 330k. That makes it a value of 76.74k. Do you think that it's ok or is it far off? Thanks!

Hi, I'm still around, just not doing much videos anymore. Anyway, I'm still happy with the mods to the PP400, it a completely different level of preamp with this mod. However I'm not sure the PP500 is the same design and if the mod will work on this model. I haven't seen the inside of the PP500. Cheers, Jake

I'd call ~3dB drop below 500Hz a lot worse than "a bit weak" in the bass region. Your suggestion with the 1Meg to 1.8Meg will still give a deviation of around ~3dB from flat, now you just have a big drop in the upper bass region instead of a drop in the whole bass region. Why not just follow the values I suggest in the video and get a frequency response with a deviation of just ~0.15dB, it's only 5 components per side? Cheers, Jake

@@TheStuffMade When gain is zero at 1khz gain at 500hz is 2.4db RIAA indicates 2.65db error is minimal , not 3db. Gain at 200 is 7.2 db while riaa gives 8db Gain at 100 is 12db while riaa gives 13. So more or less is within 1db. With your setting (taht indeed is perfect) the overall gain is too much for my AT130E that has 5mv output at 5 cm \ sec.

@@MrKkprince No that's not correct, if you only change the 1Meg resistor to 1.8Meg then you'll have a ~2dB dip at around 155Hz, that is definitely audible. But if you just want less gain you can leave the 2k resistor at 2k or maybe change it to 3k. However the standard gain for a 5mV/1kHz/5cm/sec is 40 dB, exactly what my modification sets the gain at. You'll still have good overload margin. Cheers, Jake

Yes, you can connect this directly to a headphone amp, no problem. Cheers, Jake

@@TheStuffMade Thanks!

Hi, the modification I've done here will ensure a flat frequency response (within 0.5dB) and increase the gain by about 5-6dB. I don't have any experience with the Niam Muso, but I suspect it's analog input is optimized for connecting devices like MP3 players, phones and CD players which usually have higher outputs around 2Vrms whereas a phono amplifier usually don't output more than 0.5Vrms. However it can also be your turntable/cartridge having a lower than usual output. What turntable/cartridge are you using?

@@TheStuffMade Hi. Thanks for the reponse. Mine's Audio Technica MM AT3600 if I recall. If I should, how >1kHz band gain can be lowered and increase

Yes, you are correct that a phono preamp should have a response which looks like the RIAA equalisation curve, +20dB @20Hz, 0 @1kHz, -20dB @20kHz, not flat at all. However here, what was applied was a signal source which has the inverse (as explained in response to another comment) - since the circuit clearly performs the RIAA equalisation. Hence the apparently ‘flat’ response is in fact the combination of the inverse RIAA signal source and the RIAA equalisation response of the preamp.

Hi, I haven't had a chance to look at the pp500. Cheers, Jake

Hi Marcel, first I'd make sure you have a solid ground connection between the turntable and the receiver. In my experience the older Denon receivers have decent phono preamps built in, I doubt it's causing the hum issue, but it's worth a try to use the PP400 preamp and just connect it to any of the line inputs, also here make sure you have the ground from the turntable connected to the PP400. The modification in this video is well worth doing if you end up using the PP400. I wouldn't worry about earth ground, but if you do connect earth ground, only do it for the receiver otherwise you could end up with a ground loop. Cheers, Jake

​@@TheStuffMade The receiver in case, Denon DRA-545RD, does not have a proper ground connection. On the Onkyo turntable, all plastic, looking at the service manual and the unit itself, a common wire runs from the two signal grounds to the spindel and into the tone arm without any connection to the cartridge. So that’s not much of a ground I’d say. On the receiver, a proper chassis ground connection can always be made of course. My brother tried with a wire connected to the Denon’s chassis and the aforementioned ‘ground’ wire of the turntable, which made it worse. That’s why I came up with the PP400 solution, without knowing if that would do anything good. What do you think? Cheers, Marcel

It's not going to work out of the box with an MC cartridge, but in theory you could modify it to work. You'd have to increase the gain to 60dB and decrease the input impedance to something like 100 ohm, plus you should probably replace the opamp with a lower noise type because of the added gain. Cheers, Jake

Look at 8:15 here I go though the changed component values, 2 resistors, 2 film capacitors and 1 electrolytic capacitor. Cheers, Jake

Hi Joeri, It depends on how you intend to use the output of the phono preamp. If you want to hook it up to an amplifier then yes, you can just add a 1k-10k pot on the output to control the volume since it's quite low output impedance. However if you want to e.g. drive a pair of headphones directly then it would need more added components like an extra opamp buffer to add a volume control. Cheers, Jake

Sure, you can do that. The values I suggest are to stay within the most common E12 range, but of course there are many valid combinations, you could also use a single resistor from the E48/E96 range at 78.7k. Cheers, Jake

@@TheStuffMade Your knowledge is impressive. I didn't even know E series existed.

Sure, if you don't experience any issues with hum, then you don't need the ground wire. Some turntables combine the ground with the signal ground instead of running a separate wire. Cheers, Jake

Doing the mod will also increase the output level. What cartridge are you using? Cheers, Jake

@@TheStuffMade thanks for the reply, I'm using a Marantz TT320 with the original Marantz cartridge.

@@t0nitoYeah, I believe that's a lowish output cartridge, something like 2.6mV compared to the standard 5mV.

Please save some of the spiked eggnog and whisky for the rest of us, it's not even Christmas yet.

Hi Joao, unfortunately I don't have the time available to handle requests like this, plus is would get very expensive with shipping and everything. I recommend you look for a local maker space or perhaps post your request on the eevblog forum, I have talked to many talented electronics engineers from Brazil on this forum, maybe one of them can help you. Sorry to be of little help. Cheers. Jake

Hi Nico, I replied to your email. Cheers, Jake

@@TheStuffMadehi ! I have sent to you the final schema ! Can you please check it? 😅 thank you in advance

@TheStuffMade : hi can you check my schema please? thank you

That doesn't sound right, what kind of cartridge are you using? make sure it's moving magnet and not a ceramic/piezo type cartridge. Cheers, Jake

Well of course it's most important that you like the sound, but why don't you use the built in phono input on your JVC amp instead? Cheers, Jake

@@TheStuffMade Just sounds better to with it's own preamp. I plan on buying a Schiit Magni

@@TweakedSystems The phono preamp build into your JVC amp is much higher quality than this flawed little $10 box. It's also better than the Schiit Mani. Since you invested $700 in an Ortofon 2M Black cartridge, I'd recommend going a bit more high end on a separate phone preamp with more features, get something with adjustable input impedance and capacitance. Cheers, Jake

@@TheStuffMade something like Cambridge Audio Alva Duo

Sure, you could try a LME49720 and perhaps raise the supply voltage to 20V. Cheers, Jake

I used to have some sample music, but it got flagged for copyright so I had to delete them. Cheers, Jake

@@TheStuffMade I found your work very interesting and in fact the frequency response shows many improvements. As soon as I get what I bought I will test it and if I realize that an improvement is needed, I will make this modification. In the next modifications you could insert the before and after samples on some platforms like Soundcloud or even put them in a cloud like Google Drive and the public links to it. Cheers.

@@karensartori3456 It's a good suggestion thanks. I should probably upload and link some music samples somewhere. Before the modification I found that it sounded like a disconnect between the bass and the rest of the frequency range, that was what got me to investigate further and eventually implement the mod. Cheers, Jake

@@TheStuffMade Great. Keep on doing this great mods. Just a question: if I maintain the 2k resistor it would affect only the gain? I noticed that there is an increase of amplitude in the signal, this could generate any distortion? Or it is safe to do this without distortion?

I'll probably do an update video with more details as I have to additional changes to add., perhaps with a companion document as I did with my recent tube preamp mods. Cheers, Jake

In the phono pre-amp it's part of the feedback loop. And in software the inverse RIAA is applied when the RIAA checkbox is checked.

@@TheStuffMade So you removed the RIAA curve through your modification of the circuit?

Hi @@alphanumeric1529 no, the modification corrects the 3dB+ error in the original design from the manufacturer.

@@TheStuffMade Well in that case how did you confirm that your basic RIAA curve achieved is perfect. because you are using your inverse curve from your own design. so it would negate the effect even if exact RIAA is not achieved during modification. Can I request you to share Ltspice schematic? I would give it a try.

@@yogeshkar The RIAA curve is very well defined, why would you assume I'm not capable of producing an inverse RIAA curve? I did write the whole Audio Analyzer Suite. You can find plenty of models for RIAA and inverse RIAA on the Internet if you need one. Cheers, Jake

That's very unlikely, none of the components were damaged and all their values match what is printed on the circuit board, plus the spice model simulation matches the measurement results. But possibly it's frequency response design flaw matches with your equipment or perhaps you prefer this kind of frequency response, we all have different preferences. However I can say is that it's quite far off from the ideal RIAA equalization.

If you are concerned about the overload factor you can always lower the gain or just increase the supply voltage, the NJM4580 will run with up to 36V. It depends on the output of the cartridge you are using if it will ever be a problem. I started investigating this phono preamp because I could easily hear there was something wrong when playing back records, sure our hearings are all different, but a phono preamp should not have a 3dB difference between low and high frequencies. Cheers, Jake

Hi Jake, Distortions on some of my vinyl digital recordings I made over the last 10-15 years or so (I rarely listen to records directly these days) have been the single most annoying issue, even when heard over less than HiFi-equipment. I solved this only recently by switching to a new cartridge, which has better tracking (having an elliptical stylus rather than conical) and, as I found out only later, also has a lower nominal output that matches now the input sensitivity of my preamp. The old cartridge had merely 2mV more but this appears to have been part of the problem (the recording with the new cartridge has no distortions, and the clippings visible in the previous recordings are gone). As for the deviations from the RIAA curve, there are still the bass and treble adjustments on your main amp that you can use to correct this. You would have no issues with distortions here unlike when making hardware changes resulting in a not properly matched system. You also have to bear in mind that the sound of a vinyl record depends on whatever the recording engineer put on the master recording in the first place, and that can vary wildly, certainly more than the 3dB in the Behringer preamp. So this is all a bit fluid and subjective. In the end, you get used to the overall sound your system produces, but even only occasional distortions are hard to digest, especially of you listen over headphones, and they can't be removed or compensated. So in this respect, I think matching the output and input voltages in your system properly should be of the highest priority,

Hi @@thomassmid8763 I was a bit curious because it can't be that the preamp is clipping already with 20mV input as that is only 6Vpp output, so I decided to redo the measurement and I found that actually it doesn't clip until 32mV and then the output is about 9.2Vpp or 3.2Vrms. you can see a capture of it here: imgur.com/AR8efPH that makes a lot more sense with 12V supply. Of course as I mentioned in my first reply you can always increase the supply voltage, but you will probably start having your line input clipping if it goes much higher. I also checked earlier in the video around 14:13 and see I actually did the first test with 30mV input and no clipping. So the overload margin should never be an issue even with the standard 12V supply. The reason it clipped in the last test is because the PP400 preamp uses fairly large value polar electrolytic coupling capacitors on the output to remove the DC offset and if you just switch on the power and use it right away then these capacitors might not yet have charged up to the center voltage and it will clip at a lower voltage. Anyway, I think records are a very flawed format, you will always get distortion in the range of 1 - 5%, dependent on frequency and where on the record you are, even with a high end cartridge, but personally I enjoy well mastered records, especially older ones (generally before 1990). I'd never buy a new release on vinyl as they usually sound awful and the digital version is much cleaner. However I've noticed one of the problems I have with digital is that it's too easy to switch tracks all the time and never just sit back and enjoy a full album, here the old records have a big advantage. I'd not recommend trying to use the tone controls to try correct the frequency response error in the PP-400 preamp, you'll end up with a peak or a dip in the midrange even if you get the bass level perfect. Cheers, Jake

​@@TheStuffMade Hi Jake, Thanks for doing these further tests. Even if the overload margin is 32 mV this would still not be great though. It would be about 16dB over the input sensitivity of 5.3mV. Even with a 3.5 mV cart it would only be 19dB. The built in phono stage of my Onkyo receiver has 70mV overload margin according to the spec, which equates to 26dB given the 3.5mV input sensitivity. Anyway, I returned now yesterday the PP400 to Amazon. I couldn't test the clipping issue myself with it as I don't have the records available at my present location where this is an issue (it occurs only with a small percentage of records that have apparently been cut a bit 'hot'), but I certainly won't expect any improvement on my built in phono stage in this respect. It sounded a bit dull in comparison as well. However, a further reason why I purchased the PP400 is this: I bought recently a new turntable (used from Ebay), a Marantz direct-drive from the 80s. All the recordings made from this over my Onkyo receiver show a pronounced sharp peak at 33Hz in the spectrum. I bought the PP400 in order to see whether it is the turntable that produces this peak or the built-in phono stage of my receiver. Since I found that this peak also occurred when recording with the PP400, this means it is the turntable. Would you have an idea where this 33Hz frequency could come from (there is also a 16/17 Hz peak which may be related)? One often finds the mains frequency and its harmonics in the spectrum, but this is new to me. It doesn't appear to cause problems as I couldn't hear anything of it in the recording, but it would still be good to know. Thomas

@@thomassmid8763 Hi Thomas, These overload levels are complete marketing BS. Something else will start clipping way earlier than reaching e.g. 26dB, just think about it, if you are listening to music at a moderate level with your amplifier delivering peak 10 Watt to your speakers, then a 26 dB overload would require your amplifier to deliver 3981 Watt into your speakers without clipping. Yes that's close to 4 thousand watt !!!, I don't know any amplifier or speaker that can handle these levels of dynamics. Anyway, on the 17/33 Hz peak issue, my best guess it's the resonance of your cartridge combined with your tonearm, there are some advanced calculations to find out if your arm (heavy or light) is compatible with a specific cartridge, the compliance of the cartridge is important here (often specified as something like e.g. Dynamic compliance: 6.5 x10-6 cm/dyne). It's referring to the hardness of the rubber holding the cantilever on your cartridge vs the mass of your arm, so a heavy arm, like old school aluminum with 1/2" headshell usually works better with a slight stiffer cartridge, but one of the more modern light weight carbon fiber arms work well with a soft suspension cartridge. It's a personal preference, some like the light weight arms, some like the heavier arms. But a bad combination of cartridge and arm can result in some nasty resonances going too high in frequency. Cheers, Jake

Sure you can do that, but this video is meant for people who already own and use this preamp. Cheers, Jake

@@TheStuffMade Good point