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Hi, I posted a thread relating to this schematic yesterday but as I've read the rules here, it's not okay to hijack a thread so I'm posting this schematic again but with another question.

I'm making a project in which the amplifier circuit is based on this open-source project: https://www.hackster.io/metrowest_a...R-AjRhpRLj0mh6LpKVaK0leOluvmfEOFRofYsBueA4HAU.

The new problem here is that I cannot find the capacitors with red circle in any stores in my place. What could be a good substitute for them?
- I can only find 560pF and 680pF which is near to C4's value and 10nF and 15nF for C2 and C5's value.

Another problem here is that, I also cannot find TL972 OP Amp and I've read other forums and articles that suggests a good alternative, which is MCP6002. Is it really okay to substitute TL972 with MCP6002? Would there be any complications if I substitute it with MCP6002? Since TL972 is a Rail-to-Rail OP Amp and MCP6002 is also a Rail-to-Rail OP AMP.

 

I don't know where you live , but the only place I ever buy is on eBay (I live in Thailand)

You can get everything at a lower price than the store around the corner ...

My life would be very difficult without eBay , I get about 100 deliveries a year.

 

I don't know where you live , but the only place I ever buy is on eBay (I live in Thailand)

I live in Philippines and I cannot find the components on stores near me so I ordered online. I've already ordered the MCP6002 on Lazada which is from China since TL972 is not available on local stores and local online stores. I could have ordered TL972 on Mouser Singapore but the Shipping fee is 12x more expensive than the IC itself and I need the IC within 2 weeks so I resorted with MCP6002.

About the capacitors, I also cannot find it on any stores near me, even online stores which can deliver the item 2-7 days.

 

Hi, I posted a thread relating to this schematic yesterday but as I've read the rules here, it's not okay to hijack a thread so I'm posting this schematic again but with another question.

It's bad form to hijack someone else's thread, but there's absolutely nothing wrong with posting follow-up questions in your own thread (provided that they're related in some way to the thread topic). In fact, it's much preferred over starting multiple threads on the same topic or project.

 

It's bad form to hijack someone else's thread, but there's absolutely nothing wrong with posting follow-up questions in your own thread (provided that they're related in some way to the thread topic). In fact, it's much preferred over starting multiple threads on the same topic or project.

Oh, I thought follow-up questions related to my previous thread is hijacking. I'm sorry. I'm still new to this forum. I guess I'll keep this thread though but I won't make the same mistake again in the future. Thank you.

 

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Hi, I posted a thread relating to this schematic yesterday but as I've read the rules here, it's not okay to hijack a thread so I'm posting this schematic again but with another question.

I'm making a project in which the amplifier circuit is based on this open-source project: https://www.hackster.io/metrowest_a...R-AjRhpRLj0mh6LpKVaK0leOluvmfEOFRofYsBueA4HAU.

The new problem here is that I cannot find the capacitors with red circle in any stores in my place. What could be a good substitute for them?
- I can only find 560pF and 680pF which is near to C4's value and 10nF and 15nF for C2 and C5's value.

Another problem here is that, I also cannot find TL972 OP Amp and I've read other forums and articles that suggests a good alternative, which is MCP6002. Is it really okay to substitute TL972 with MCP6002? Would there be any complications if I substitute it with MCP6002? Since TL972 is a Rail-to-Rail OP Amp and MCP6002 is also a Rail-to-Rail OP AMP.

A couple of the capacitor values look like the tighter spec series - same sort of thing as the E24 series resistors gives you more choice of values than the E12 series. AFAICR: the value spacings are formulated to make it easy to match missing values by series and/or parallel combinations of the lower series parts. Those circuit locations look like they affect frequency response - so you should aim for pretty close to the specified values.

 

I live in Philippines and I cannot find the components on stores near me so I ordered online. I've already ordered the MCP6002 on Lazada which is from China since TL972 is not available on local stores and local online stores. I could have ordered TL972 on Mouser Singapore but the Shipping fee is 12x more expensive than the IC itself and I need the IC within 2 weeks so I resorted with MCP6002.

About the capacitors, I also cannot find it on any stores near me, even online stores which can deliver the item 2-7 days.

The op-amp is probably something the original designer had a big quantity price break on anyway. Chances are your substitution might even be better - use an IC socket and you can try other things later.

 

A couple of the capacitor values look like the tighter spec series - same sort of thing as the E24 series resistors gives you more choice of values than the E12 series. AFAICR: the value spacings are formulated to make it easy to match missing values by series and/or parallel combinations of the lower series parts. Those circuit locations look like they affect frequency response - so you should aim for pretty close to the specified values.

So those capacitors I have encircled with is kind of hard to find? The only capacitors I can find are those with standard values and which is common and widely available on my locality, only 15nf for the 13.6nf and 680pf for the 620pf capacitors. Would it greatly affect the filtering of frequency from the guitar if I'll use those capacitors instead of the capacitors the author have put on the schematic?

The op-amp is probably something the original designer had a big quantity price break on anyway. Chances are your substitution might even be better - use an IC socket and you can try other things later.

Yeah, and maybe the Op Amp he stated might also be common in his place while it's not available on ours. The only difference between the two is that MCP6002 is a general purpose rail-to-rail op amp that produces a lot of noice, the op amp's data sheet tells me that the input voltage noise is 28nV/sqrt hz while the TL972 is a very low noise rail-to-rail op amp in which its noise is just 4nV/sqrt hz. Would the input noise also greatly affect the filtering too?

I can't seem to find any ic sockets for the Op amp since ic sockets for microchips isn't available on our place. Only those 14-18 pinned sockets.

 

680p will most likely be fine instead of the 620p. I'd use a 15 nF to replace the 13.6 nF listed. These subs will have a very small effect on the frequency response of the circuit, but i don't think frequency response is a critical parameter here.

[and I'd suggest a 1N4148 for the output diode. If you have already ordered the 1N400x, that's OK too, but will likely have higher leakage than the 1N4148]

 

680p will most likely be fine instead of the 620p. I'd use a 15 nF to replace the 13.6 nF listed. These subs will have a very small effect on the frequency response of the circuit, but i don't think frequency response is a critical parameter here.

Thank you so much! ^^ I have a follow-up question, I forgot to encircle the 7.4uF capacitors, the only available capacitor would be 2.2uF, would it do if I'll do a four 2.2uF capacitors paralleled with each other? I'm really sorry for the noob question.

[and I'd suggest a 1N4148 for the output diode. If you have already ordered the 1N400x, that's OK too, but will likely have higher leakage than the 1N4148]

I have already soldered the diode >< but as I've searched about 1n4148, the diode seems more appropriate for the circuit because it has a fast recovery time. I'll try go on stores near me tomorrow and I'll try the 1n4148. Thank you. ^^

 

I have a follow-up question, I forgot to encircle the 7.4uF capacitors, the only available capacitor would be 2.2uF, would it do if I'll do a four 2.2uF capacitors paralleled with each other? I'm really sorry for the noob question.

I don't see any 7.4 μF capacitors; where are they? I see two 4.7 μF capacitors, which is a standard value. I agree with @Ylli's comment about the 620 pF and 13.6 nF capacitors; with 680 pF and 15 nF in their place, you'll never hear the difference.

 

Hello,

If you insist to get closer values, you could put an 470 pF and an 150 pF parallel for the 620 pF
and an 12 nF and an 1.5 nF for the 13.6, wich makes 13.5 nF.

Keep in mind that capacitors can have a quite large tollerance.

Bertus

 

Two 4.7 uF caps. These are standard values and you should be able to find them. The values are not critical, and anything near 4.7 uF or more would be OK. I'm sure two 2.2 uF in parallel would be close enough.

 

I don't see any 7.4 μF capacitors; where are they? I see two 4.7 μF capacitors, which is a standard value.

I'm sorry, I've mistyped the value and eventually given a wrong calculation to the 4.7uF caps. I wen't to 2 stores a few hours ago and they can only offer 2.2uF. Although one of those stores offers a 4.7uF cap, it's a 4.7uF 450vdc capacitor which I did not buy.

 

Hello,

If you insist to get closer values, you could put an 470 pF and an 150 pF parallel for the 620 pF
and an 12 nF and an 1.5 nF for the 13.6, wich makes 13.5 nF.

Keep in mind that capacitors can have a quite large tollerance.

Bertus

Okay sir, thank you so much. I'll try to find those capacitors on local stores near me, I hope I'll do find them. Our locality doesn't specialized on electronics but on farming so although a component may be standard value and widely available, it might be unavailable on stores near me so I might need to order it online. Thank you so much.

 

Two 4.7 uF caps. These are standard values and you should be able to find them. The values are not critical, and anything near 4.7 uF or more would be OK. I'm sure two 2.2 uF in parallel would be close enough.

I'm sorry, I've mistyped the value thus giving it a wrong calculation. Thank you so much for your help. ^^ I just can't wait to test the amplifier circuit tomorrow. Thank you. ^^

 

The only difference between the two is that MCP6002 is a general purpose rail-to-rail op amp that produces a lot of noice, the op amp's data sheet tells me that the input voltage noise is 28nV/sqrt hz while the TL972 is a very low noise rail-to-rail op amp in which its noise is just 4nV/sqrt hz.

If your input signal source has an extremely low output level, such as a magnetic phono cartridge or a dynamic microphone, then an op amp with 28 nV/√Hz noise would probably not be a good choice for highest possible fidelity. But the fact that your amplifier has a maximum voltage gain of around only 22 suggests this is not so; therefore, I should think the MCP6002 will serve quite well in this circuit.

Further thought on the 4.7 uF capacitors: the one on the bottom is utterly non-critical, and could be anything from 1 uF to 100 uF. The one on the top has an effect on the frequency response of the circuit; make it too small and your low notes won't be amplified as much as the highs.

I think you could change both 4.7 uF capacitors to 10 uF with no ill effects, if 10 uF is more readily available.

 

Thank you so much! ^^ I have a follow-up question, I forgot to encircle the 7.4uF capacitors, the only available capacitor would be 2.2uF, would it do if I'll do a four 2.2uF capacitors paralleled with each other? I'm really sorry for the noob question.



I have already soldered the diode >< but as I've searched about 1n4148, the diode seems more appropriate for the circuit because it has a fast recovery time. I'll try go on stores near me tomorrow and I'll try the 1n4148. Thank you. ^^

The bigger the diode - the greater the junction capacitance. A 1A part could make the output less "bright".

There's loads of similar diodes to the 4148 in the same package style, the 1N914 would do - but there's all kinds of weird and wonderful devices occupy the same type of package. If its for a clipping effect - a germanium diode an option some people go for. It has about 1/3 the Vf, but the knee curve is softer - some musicians hold that sound in high esteem.

 

If your input signal source has an extremely low output level, such as a magnetic phono cartridge or a dynamic microphone, then an op amp with 28 nV/√Hz noise would probably not be a good choice for highest possible fidelity.

This is something from the site written by the author: "The signal coming from the guitar, however, is very low in amplitude and oscillates around 0 V, meaning it contains some negative voltages that the Arduino cannot read.". The input signal is coming from an electric guitar and I don't know if the signal coming from the guitar is considered as extremely low.

Sir, I've already tested the amplifier circuit on Simulink and it wont send any signal to the arduino. Whenever I strum a string, there are no changes in amplitudes, just a straight line. I've run a simulator and here is the image. It's on a 5s period.




I've tested the guitar without the amplifier circuit on simulink and as you can see, whenever I strum a string, there're changes in amplitude.

The simulation is on a 12s period. I strum the low E string once. So this means there's nothing wrong with the code, or the guitar or the jack, it's the amplifier circuit... What can you suggest sir so I can fix the amplifier circuit?

 

I think you could change both 4.7 uF capacitors to 10 uF with no ill effects, if 10 uF is more readily available.

I found a store that sells 4.7uF electrolytic capacitors sir.