That was me. But as a bass player whose looked at lots of bass amp schematics and am currently designing a compressor pedal Im sticking to 5534s and TL072s like Ashdown, G&K, Fender, not to mention SSL and Neve. The sound is in the design.
Heres a design for a guit pedal comp, but you can use the the pre and output sections to do what you want, at least a sterting point.
http://www.thatcorp.com/pedals/4316 Battery-Powered One Knob Squeezer.pdf
Lots of other info on there guit pedals page
http://www.thatcorp.com/pedals/4316 Battery-Powered One Knob Squeezer.pdf
Lots of other info on there guit pedals page
+1000 😎
Problem is you must know how to design and have an idea as to what is needed to reach this or that sound.
Inspiration is helped by manuals, datasheets and experimentation.
If you have no clue, then you try to reach that by using parts which are "supposed" to sound in a particular way.
In this case Inspiration comes from reading salesmen brochures, random Forums here and there and maybe following some self proclaimed Guru.
Plus getting a degree at "Youtube University" 🙄
You're both right in the matter of fact. I just don't have that much time and knowledge to go into so many details so I refered to a schematic that i heard it's actually good, and put in this tone circuit as it's the same used in one of my favourite onboard bass preamps - Aguilar. I don't know its full design, but i found an information that the OBP-2 uses the same tone circuit (baxandall) and I used that in this preamp. That part is "design".
Now i know that is not everything, but is what i have. Also i build this stuff from time to time, having deeper knowledge and understanding about it requires much more than that. That's why i'm here in the forum, if i knew all of that and what to do i probably wouldn't be asking for help, or at least would probably start somewhere that would make more "sense" to the guys that have deeper knowledge on this. And yeah, i'm no pro at this so i had to start somewhere, which lead to another thing, making me aware of stuff i didn't know, so i very appreciate all the input from all the members that contributed in any way, regardless if it's something i prefer or not. That's just a matter of taste, as well as choice on a brand for an amplifier etc.
I understand your point of view on this, i get that, just i don't understand electronics as you guys do. So as i said in my first post and several times, i'm open to anything that will help me get the desired result, even if that is a completely different schematic, just i wouldn't know to design it or to play with some critical components, which means i'd need more "baby steps".
cbdb thanks for the links, i'll have a look and see if i can extract something out of that.
Now i know that is not everything, but is what i have. Also i build this stuff from time to time, having deeper knowledge and understanding about it requires much more than that. That's why i'm here in the forum, if i knew all of that and what to do i probably wouldn't be asking for help, or at least would probably start somewhere that would make more "sense" to the guys that have deeper knowledge on this. And yeah, i'm no pro at this so i had to start somewhere, which lead to another thing, making me aware of stuff i didn't know, so i very appreciate all the input from all the members that contributed in any way, regardless if it's something i prefer or not. That's just a matter of taste, as well as choice on a brand for an amplifier etc.
I understand your point of view on this, i get that, just i don't understand electronics as you guys do. So as i said in my first post and several times, i'm open to anything that will help me get the desired result, even if that is a completely different schematic, just i wouldn't know to design it or to play with some critical components, which means i'd need more "baby steps".
cbdb thanks for the links, i'll have a look and see if i can extract something out of that.
Last edited:
You shouldn't even put NE5534s and TL072s in the same reference--they are COMPLETELY different opamps. The NE5534 is THE classic bipolar design, having been used by Neve, SSL, and many other SOTA console manufacturers.; this is due to its awesome sound. A TL072 is a noisy, weak old JFET design that wouldn't be used in any of of those consoles and not one I would recommend for anything. If you like FETs, the OPA1642s and 1656s are FAR superior.
TL072 is as old as NE5534. The voltage noise figure with 18nV/sqrt(Hz) of TL072 far exceeds the 5nV/squrt(Hz) of NE5534. But these numbers are in many cases quite irrelevant. And for a high impedance source like a magnetic pickup the audible noise of NE5534 far exceeds the noise of TL072. Being a bipolar device, the current noise becomes dominant.
Due to their restricted output level these oldies work best with +-15V supplies. For battery operation there are better options available nowadays, like OPA2196, for instance.
Last edited:
It's certainly true that a bipolar device has more current noise than an FET one. But, comparing an NE5534 to a TL072 with a guitar pickup---let's say ~10KΩ source impedance with ~ 5KΩ source resistance at 40mV out---the 5534 will STILL be ~ 5db quieter. An OPA1642/52/56 will be another db quieter than that. A TL072 is just too damn noisy for my tastes, and starts to really suffer when driving anything less than ~ a 10KΩ load.
Obviously you never tried that in real life. Assuming a source resistance of 10k for a guitar pickup? You are joking.
No, I'm not joking--are you? I perhaps underestimated the source impedance by a little bit, but not by much. I looked it up, and a typical Strat pickup is ~6KΩ of DC resistance and about 2.2 Henrys of inductance. That works out to about 15KΩ of source impedance at 1KHz---a little higher than I previously said. It STILL results in about 4.4 db more noise from the 5534 than from the TL072.But that's at 1KHz---if you go up in frequency, the FET device will naturally perform better---the two devices in question will be about the same noise at ~3KHz---so above that, the 072 is quieter, below that, the 5534 is quieter. But, in my experience, I've heard TL072s in many pedals, and they're all NOISY!! I'd still use an OPA1642/52/56 for a guitar preamp if I were choosing.
Last edited:
The noise you perceive from the P.U. is filtered by its self resonance peak being in the ballpark of 2~5kHz. And so you should consider this impedance, which may reach 1MOhm at peak and may be averaged by 100kOhms. At this place the JFET definitely outperforms any bipolar input stage.
Reducing audible noise in my amps has always been on top focus for me. In the 70's I placed a JFET buffer-amp into my strat, screed the innards with tin, replaced the original single coils by stacked humbuckers. Any electric guitar of my own (i.e. a total of 2 pieces!) and my electrified dreadnought are modified that way.
Well, I never used much pedals, building my own stuff but I know about these poor designs - using 100kOhm pots all the way - to name just one culprit. The resulting noise in most cases is dominated by poor design and will not improve significantly by swapping the op-amps. So the conclusion their noise is due to poor TL072 needs verification.
If you look at active ceramic PUs as found in many acoustic guitars you will find the infamous TL064. The most noisy of them all, but with lowest power consumption. Considering the high impedance of these sources this choice works fine in real world.
Last edited:
It's quite true that poor design will dominate any opamp selection; but why start out with a noise generator like the TL072 to begin with? Especially when there are many devices available these days that are MUCH better; an OPA1642 is only a coupla bucks!
There's too much to figure out regarding op amp noise and its relation to impedance and f, but much less headache to just go with an op amp with good enough specs, most of those are around or below $10. This technique works way better for me when building just one or two preamps. So why not save yourself some time unless you're making 50 or 100 pcs.
I've already purchased OPA1642, seems to have really good specs and is in the Sound Plus category, current draw isn't perfect for batt but not that bad either at 1.8mA per amp. OPA1692 has near perfect specs about everything except that it's bi-polar. I'd prefer FET, they definitely tend to have fuller more organic sound.
The design of this circuit is about to be tested when I get all the parts, the tone circuit design is already used in a top of the line preamps so that bit should be ok, I'll see how it will sound in this circuit.
I've already purchased OPA1642, seems to have really good specs and is in the Sound Plus category, current draw isn't perfect for batt but not that bad either at 1.8mA per amp. OPA1692 has near perfect specs about everything except that it's bi-polar. I'd prefer FET, they definitely tend to have fuller more organic sound.
The design of this circuit is about to be tested when I get all the parts, the tone circuit design is already used in a top of the line preamps so that bit should be ok, I'll see how it will sound in this circuit.
You are right ... to a point 🙂 BUT playing out of the football field.
We are talking Musical Instrument electronics here.
make superlative stuff for a niche use: Recording/Radio/TV studios and are used (those which stand transport abuse) in live sound reamplification.
Market share? ... maybe 10.000 worldwide in the last 40 years or so.
But those are the "wrong brands" to quote.
Think instead Fender, Marshall, Ampeg, Laney, Crate, Peavey, Hughes & Kettner, and hundreds more, the most popular Op Amp used by them is TL072, by far.
WHY?: because it´s COMPETENT to do its job and then some.
Think tens of MILLIONS.
Are they all fools? ... doubt so.
Is it because of the price?
Not really, cents difference.
They simply WORK.
In fact, many onboard instrument preamps use even LOWER SPECS TL062 😱 , the weak TL072 cousin, just because it eats 1/5 of the idle current and is still adequate, go figure.
Even more, a couple use ABYSMAL specs "programmable Op Amps" such as LM4250, specifically as revered Bass preamps 😎
I heard nobody complain about Queen´s Bass sound, for example, (quite the contrary) even if their Music Man Bass uses such "horror".
Simply different needs and specs to match.
Last edited:
My feelings exactly, many of the most poular amps and pedals in the world use the TL072 as an input amp. What do they know?
IIRC, the '5534 actually derives from an older HIGH-price opamp, for strain-gauges, which stopped production before it found its audio market. And that was before the TL07x appeared.
The TL07x also had a parent, the LF351, but was specifically designed to UNDER-cut the price using clever then-new processing.
However within its limits the TL07x is so good that EVERY recording has been through a dozen of the little failures.
The TL07x also had a parent, the LF351, but was specifically designed to UNDER-cut the price using clever then-new processing.
However within its limits the TL07x is so good that EVERY recording has been through a dozen of the little failures.
A question about the voltage divider in this circuit. Can I increase the value of the two 4k7 resistors (increasing the impedance of the power supply in other words) to get the divider to draw less current? If so, what is the maximum it can go without having any adverse effect?
Or is it better to use IC voltage divider for that purpose instead of the resistors and caps?
Also, I decided to use two OPA145, it has so far the best specs with very low power requirement and supports single power supply and it's a FET input which is better for an instrument.
So, considering all this what is the best way to deal with the power section now to have it draw as less current as possible? I know converting this to single supply will take some modification of the circuit, which I tend to avoid if the current can be lowered in symmetrical. But will convert to single with some help if it's a way better way for battery.
Or is it better to use IC voltage divider for that purpose instead of the resistors and caps?
Also, I decided to use two OPA145, it has so far the best specs with very low power requirement and supports single power supply and it's a FET input which is better for an instrument.
So, considering all this what is the best way to deal with the power section now to have it draw as less current as possible? I know converting this to single supply will take some modification of the circuit, which I tend to avoid if the current can be lowered in symmetrical. But will convert to single with some help if it's a way better way for battery.
Last edited:
Yes. Buffer it with an op-amp. Not sure what you mean by 'IC voltage divider' , but a single op-amp channel will do very well. Since you'll probably want to use another JFET-input device, you can raise the resistor values a ton -- 100k would not be unreasonable. Just be sure to consider power-up/power-down when you design the capacitor AC bypassing. You'll probably want to have approximately matching values going to each rail -- ground and +9V -- both to reduce thumps, AND strain on the op-amp input.
Have you removed the interstage coupling caps? -- just curious.
Regards
Have you removed the interstage coupling caps? -- just curious.
Regards
I'm using 2 opamps (2 separate IC's) as the OPA145 is single amp only, the dual is not out yet, but in total 2 amps, no more.
For the IC voltage divider I meant TLE2426, sorry i should have stated that. Using it doesn't require any resistors, just one cap parallel to the batt and even than may not be necessary but not sure.
But I'm trying to avoid modifying the circuit again cause I already designed the PCB at 25x25mm, would rather just use 2x 47k resistors instead of the two 4k7, but if that would cause any problems I would do the redisign for the TLE2426.
I'll post the latest schematic later when I get back home, I'm not for every bit that you're referring to. I did some research to get familiar with some stuff but not everything yet related to this circuit.
This is exactly what the TLE2426 is designed for, so it'll work.
47k might be OK -- have to see the new schematic to do anything more than guess.
Regards
edit:This might be useful -- just stumbled onto it: https://www.ti.com/lit/an/sboa059/sboa059.pdf?ts=1594362661651
47k might be OK -- have to see the new schematic to do anything more than guess.
Regards
edit:This might be useful -- just stumbled onto it: https://www.ti.com/lit/an/sboa059/sboa059.pdf?ts=1594362661651
Last edited:
By reading that article there seems to be more work to redesign the circuit from symmetrical to single power supply than to put the TLE2426 in place. Not sure what is the best way for OPA145, but says it can operate smoothly either way. I'm in pursuit of lowest power consumption, OPA145 seems great for that and in every other aspect for this purpose, just to work out the power supply. TLE is also very low on power, i think it was about 170uA.
OPA145 specs: https://www.ti.com/lit/ds/symlink/o...l=https%3A%2F%2Fwww.ti.com%2Fproduct%2FOPA145
I've added the buffered splitter instead of the resistor/cap network, so here are both circuits.
I've been playing around with the tone control so don't let the too many components and text confuse you. I found some guy that made it easier to calculate and adjust the freq you want with more standard component values so i incorporated that too. So all the mods are avaialbe on one PCB so i wouldn't have to redesign new PCB for every variation id' want to try, will just use the relevant components on one PCB when testing and whichever gets me closest to what i want.
Also i have left out proper connectors and have not attached them in the schematic. The pads for pots, in, out etc are scattered on the PCB to save space, i want this to be really small. But still the schematic should make sense without those connected.
OPA145 specs: https://www.ti.com/lit/ds/symlink/o...l=https%3A%2F%2Fwww.ti.com%2Fproduct%2FOPA145
I've added the buffered splitter instead of the resistor/cap network, so here are both circuits.
I've been playing around with the tone control so don't let the too many components and text confuse you. I found some guy that made it easier to calculate and adjust the freq you want with more standard component values so i incorporated that too. So all the mods are avaialbe on one PCB so i wouldn't have to redesign new PCB for every variation id' want to try, will just use the relevant components on one PCB when testing and whichever gets me closest to what i want.
Also i have left out proper connectors and have not attached them in the schematic. The pads for pots, in, out etc are scattered on the PCB to save space, i want this to be really small. But still the schematic should make sense without those connected.
Attachments
Last edited: