BigRedX Posted October 19, 2016 Share Posted October 19, 2016 (edited) [quote name='3below' timestamp='1476909807' post='3158471'] This is what 'surprised' me when I put the LRC configuration and values into the simulator. More so when you think about the 'mudbucker' in an EB3, why would you want to further remove high frequencies. I have treated the pickup simply as a source of ac emf and not factored the pickup's resistance (impedance) and inductance into the circuit. I wonder if my simulation was too simple. More research / exploration needed (or an EE on BC). [/quote] Which EB3 circuit are you modelling? AFAICS the [url="http://www.flyguitars.com/gibson/bass/EB3_schematic2.php"]version 2 circuit[/url] has the choke and capacitor in series which should give a notch filter effect. I don't know what the value of the EB3 chokes were, but using the 1.5H choke from the 355 circuit and a .47µF capacitor gives me a 190Hz notch unless I've got my decimal points in the wrong place... The [url=http://www.flyguitars.com/gibson/bass/EB3_schematic.php]version 1 circuit[/url] appears to do something slightly different since it taps into the filter circuit between the capacitor and the choke. Of course given what we've been told previously it could all be Gibson misinformation! Edited October 19, 2016 by BigRedX Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 19, 2016 Author Share Posted October 19, 2016 [quote name='3below' timestamp='1476914157' post='3158530'] Your understanding is correct in my world of Physics / Electronics, you have described a notch filter. They have a very interesting looking varitone wiring diagram for the 'CT' bass on the website. Might be useful? http://www.guitar-mod.com/wiring/ctimages/ctbass_wiring.gif [/quote] Yes - saw that and took a copy of it for my 'just in case' file. Couldn't quite work out what is going on (there seems to be some connections missing as far as my little brain can make out) but might be a better way of getting three more usable sounds than what I'm trying at the moment Quote Link to comment Share on other sites More sharing options...
3below Posted October 20, 2016 Share Posted October 20, 2016 [quote name='BigRedX' timestamp='1476915336' post='3158547'] Which EB3 circuit are you modelling? AFAICS the [url="http://www.flyguitars.com/gibson/bass/EB3_schematic2.php"]version 2 circuit[/url] has the choke and capacitor in series which should give a notch filter effect. I don't know what the value of the EB3 chokes were, but using the 1.5H choke from the 355 circuit and a .47µF capacitor gives me a 190Hz notch unless I've got my decimal points in the wrong place... The [url="http://www.flyguitars.com/gibson/bass/EB3_schematic.php"]version 1 circuit[/url] appears to do something slightly different since it taps into the filter circuit between the capacitor and the choke. Of course given what we've been told previously it could all be Gibson misinformation! [/quote] Attempting to model a version 1, which when 'redrawn' / deciphered appears to be a parallel CR in series with L. Version 2 makes much more sense as a series band pass filter. Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 (edited) Nice build! As I understand it, the varitone is a notch filter. You can get a RLC notch filter with a resistor, inductor and capacitor in [u]series[/u]. If you put the 22n cap and the transformer in series (to ground) then 22n and 1.5H will give you a notch at about 880 Hz. Any series resistance will not change the frequency, just make the notch less deep. So - I suggest you lift one leg of the 100k resistor (so it is out of circuit) and see how it sounds. Edit - just realised your transormer is parallel to the cap and resisotor too. If you disconnect the resistor and cap and then splice the cap between the volume pot and rotarty switch, you will get everything in series. Edited October 20, 2016 by samhay Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476953614' post='3158690'] Nice build! As I understand it, the varitone is a notch filter. You can get a RLC notch filter with a resistor, inductor and capacitor in [u]series[/u]. If you put the 22n cap and the transformer in series (to ground) then 22n and 1.5H will give you a notch at about 880 Hz. Any series resistance will not change the frequency, just make the notch less deep. So - I suggest you lift one leg of the 100k resistor (so it is out of circuit) and see how it sounds. Edit - just realised your transormer is parallel to the cap and resisotor too. If you disconnect the resistor and cap and then splice the cap between the volume pot and rotarty switch, you will get everything in series. [/quote] Great - it'll only take a few minutes to do that. To be honest, it's one of the reasons I decided to put the three components on a bit of veroboard so I could chop and change to try different things (and correct inevitable errors ). I'll try it later this morning I have made a mental note to do a bit more reading on electrical circuits! In our family when we were youngsters, I only understood things that moved and my brother only understood things that didn't - that's why I ended up as a mechanical engineer and he ended up as an electronics engineer Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 OK, folks I've done a few experiments up to the point that MrsAndyjr1515 has 'reminded' me that there are more pressing things to do today I've basically wired it like this (as far as my little brain can work out): ...which my newly acquired education tells me is a Band Stop Filter. The results are interesting, and I think as the notch filter has been described:[list] [*]With a 100k resistor, definitely different to the mudbucker alone. Similar to the bucker with the tone turned right down, but less boomy. Very quiet in comparison, though. [*]With 2off 100k resistors in parallel (ie 50 ohms?) it is louder - not as loud as the clean mudbucker but again bassier, fluffier but without the boom of the bucker with tone right down [*]With no resistor, similar in volume and tone to the mudbucker with the tone wound right down [/list] If I have understood the theory right of what the notch is trying to do and what the resistor is doing within it, I think the above is what could be predicted? Anyway - must go and do some other stuff! Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 >I think the above is what could be predicted? Yes - that sounds about right. The mudbucker has considerable resisance - perhaps 30k, so you probably won't want to add much additional resistance to get this work (2 x 100k resistors in parallel are 50k total resistance). I have seen some design(s) that use a resistor to balance between pickups, but these are mixed before the signal makes it to the volume control. The transformer will have somewhat variable inductance (this varies with frequency) and non-negligable resistance. If the resistance is more than a few k ohms then the notch becomes very broad. Are you using a blue LT44 transformer from Maplin? Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476967398' post='3158874'] >I think the above is what could be predicted? Yes - that sounds about right. The mudbucker has considerable resisance - perhaps 30k, so you probably won't want to add much additional resistance to get this work (2 x 100k resistors in parallel are 50k total resistance). I have seen some design(s) that use a resistor to balance between pickups, but these are mixed before the signal makes it to the volume control. The transformer will have somewhat variable inductance (this varies with frequency) and non-negligable resistance. If the resistance is more than a few k ohms then the notch becomes very broad. Are you using a blue LT44 transformer from Maplin? [/quote] Hi, samhay No - its a Xicon 42TL021-RC (but is indeed blue ) I wondered about trying a much smaller resistor but don't think I have any in my bits box. Shows how much I know though - I assumed the higher the resistor the narrower the band. If the garage do some magic fixing my car later today, there's a Maplin near where I pick it up from. If so, I'll get a variety of smaller resistors to try them out. What value(s) do you reckon is worth a punt? Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 That transformer is fine - don't rush out to Maplin. Will run some simulations... Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 Ah.....but I DO have a 25k linear pot! Just wired that temporarily and think I'm getting somewhere! With the pot about midway, it's almost same volume as the clean neck pickup, it's in the same tonal range as the neck pickup with tone rolled right off but a tad different. I think this is usable The other two switch positions, taking it through the inductor's split primary and full secondary, make very little difference to going through the full primary. As such, I might have a look to see if, instead, I can use the three positions to bring in three different values of capacitor... Still got no idea what I'm doing but it's immense fun (other than I should be doing other things today ) I will get a trim pot to replace the full size pot so I can use that in the final version. Thanks for all of the input so far, folks. I think I'm starting to clamber up some of the early foothills of the enormous learning curve mountain Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 (edited) Great - sound like we are on the same page. Below is the simulated frequency response of an RLC filter (image a few posts above) with your transformer (1.5H inductance and 148 ohm resistance in series with this inductance) and a 22n capacitor. The top graph shows the output when driven by a perfect voltage source. The bottom graphs shows the same filter driven by a simulated guitar (not mudbucker) pickup. Notice how there is a lot more treble rolled off, and this will get worse with a bigger pickup like the mudbucker. In both cases, the resistor is varied from 1k-100k. As the resistor gets larger, two things happen: 1. The notch gets broader 2. As this resistor works as one half of a voltage divider with the volume pot (I asssumed 500k here), larger resistances give additional signal lose at all frequencies. Bottom line - less resistance is more signal. Also, the original varitones switched in a range of capacitors, and this is still a good thing to do with the rotary switch. I can suggest values if you tell me how many values to suggest... p.s. look like a resistance of about 10k would be a good choice, so it seems the computer agrees with your ears. Edited October 20, 2016 by samhay Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476972286' post='3158922'] Great - sound like we are on the same page. Below is the simulated frequency response of an RLC filter (image a few posts above) with your transformer (1.5H inductance and 148 ohm resistance in series with this inductance) and a 22n capacitor. The top graph shows the output when driven by a perfect voltage source. The bottom graphs shows the same filter driven by a simulated guitar (not mudbucker) pickup. Notice how there is a lot more treble rolled off, and this will get worse with a bigger pickup like the mudbucker. In both cases, the resistor is varied from 1k-100k. As the resistor gets larger, two things happen: 1. The notch gets broader 2. As this resistor works as one half of a voltage divider with the volume pot (I asssumed 500k here), larger resistances give additional signal lose at all frequencies. Bottom line - less resistance is more signal. Also, the original varitones switched in a range of capacitors, and this is still a good thing to do with the rotary switch. I can suggest values if you tell me how many values to suggest... p.s. look like a resistance of about 10k would be a good choice, so it seems the computer agrees with your ears. [/quote] Brilliant! Thank you so much, samhay, BigRedX and 3below And thanks particularly for the above, samhay I have switch positions 4 5 and 6 so it would be three different capacitor values. The present one is, as you say, .022uF Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 (edited) No problem - happy to help. 22n = 0.022 uF gives a notch at ~880 Hz. The original varitones had caps ranging from 1n (0.001 uF) to 220n (0.22 uF) and they used an inductor of 1.5H, which is helpful. Here are some common cap values and the notch frequency: 1n, 4110 Hz 2.2n, 2770 Hz 3.3n, 2260 Hz 4.7n, 1900 Hz 10n, 1300 Hz 15n, 1060 Hz 22n, 880 Hz 33n, 715 Hz 47n, 600 Hz 68n, 500 Hz 100n, 410 Hz 150n, 340 Hz 220n, 280 Hz Do you have any/many other cap values you can experiment with? Edited October 20, 2016 by samhay Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 Thanks again, samhay I've got .011uF; 0.022uF and .047 on hand. If PRS have ever fitted 0.22uF (because that is what seems to be written on the side of a cap out of a PRS circuit, then I may have one of those too I may be able to find a bit of time this eve and I'll try them out. Failing that, it'll be middle of next week. Either way, I'll let you know I'll also order a 0.001uF - it will be waiting for me when I get back Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 220n would make for an incredibly dark tone control on a passive bass or guitar. In any case, I have a good stash of caps and am happy to pop some in the post if you want to try other values. Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476980736' post='3158995'] 220n would make for an incredibly dark tone control on a passive bass or guitar. In any case, I have a good stash of caps and am happy to pop some in the post if you want to try other values. [/quote] If I understand the figures above, doesn't the 220n knock out the low frequency 280Hz? (It must be said that I probably don't understand the figures above ) Quote Link to comment Share on other sites More sharing options...
BigRedX Posted October 20, 2016 Share Posted October 20, 2016 [quote name='Andyjr1515' timestamp='1476970925' post='3158913'] Ah.....but I DO have a 25k linear pot! Just wired that temporarily and think I'm getting somewhere! With the pot about midway, it's almost same volume as the clean neck pickup, it's in the same tonal range as the neck pickup with tone rolled right off but a tad different. I think this is usable The other two switch positions, taking it through the inductor's split primary and full secondary, make very little difference to going through the full primary. As such, I might have a look to see if, instead, I can use the three positions to bring in three different values of capacitor... Still got no idea what I'm doing but it's immense fun (other than I should be doing other things today ) I will get a trim pot to replace the full size pot so I can use that in the final version. Thanks for all of the input so far, folks. I think I'm starting to clamber up some of the early foothills of the enormous learning curve mountain [/quote] The baritone circuit that I have for the Gibson 355 guitar uses 0.001µF, 0.003µF, 0.01µF, 0.03µF and 0.22µF capacitors for the 5 filter positions (the 6th is a bypass) if that helps? Quote Link to comment Share on other sites More sharing options...
samhay Posted October 20, 2016 Share Posted October 20, 2016 [quote name='Andyjr1515' timestamp='1476981331' post='3159008'] If I understand the figures above, doesn't the 220n knock out the low frequency 280Hz? (It must be said that I probably don't understand the figures above ) [/quote] That's correct for the notch filter. The corner frequency will be different for a more conventional low pass filter (tone control), but vintage p bass tone controls use 100n, which most consider to be about as dark as anybody would ever need. 220n is darker. Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476989645' post='3159092'] That's correct for the notch filter. The corner frequency will be different for a more conventional low pass filter (tone control), but vintage p bass tone controls use 100n, which most consider to be about as dark as anybody would ever need. 220n is darker. [/quote] Ah - I understand what you are saying. Yes - in normal tone position, a capacitor of .047 is about as high as I go. [url="https://soundcloud.com/andy-rogers-6/eb3-notch-comparisons"]This soundclip here[/url] is not terribly useful because somewhere along the line something is clipping, but it gives some idea of the type of sound coming out. It sounds like an old fashioned moog synthesiser to me (think The Persuaders theme). I announce each of the settings, but on the file, all neck pickup, is : no notch, tone at 10; no notch, tone at zero; notch with .011 capacitor; notch with .047 capacitor; notch with .022. You can't really hear it here, but through the amp the .22 does sound brighter and clearer. However, the .047 is noticeably louder than either of the other capacitors. I'll try and record some better quality samples next week Thanks again for all the input, folks Andy Quote Link to comment Share on other sites More sharing options...
3below Posted October 20, 2016 Share Posted October 20, 2016 (edited) Andy, are you now getting useable or even better tones from the varitone? Samhay, would you be able to model the mark1 RLC circuit? [url="http://www.flyguitars.com/gibson/bass/EB3_schematic.php"]http://www.flyguitar...3_schematic.php[/url] I am still intrigued what tfrequency response this circuit will produce taking account of the pickup as a voltage source with inductance and impedance. I do not have access to suitable modelling software (this tells me I should get some for the day job). Thanks. Edited October 20, 2016 by 3below Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='BigRedX' timestamp='1476988665' post='3159084'] The baritone circuit that I have for the Gibson 355 guitar uses 0.001µF, 0.003µF, 0.01µF, 0.03µF and 0.22µF capacitors for the 5 filter positions (the 6th is a bypass) if that helps? [/quote] That's useful info, BigRedX. I've got a 0.001 cap on order - I'll be interested what it sounds like compared with the others. Quote Link to comment Share on other sites More sharing options...
3below Posted October 20, 2016 Share Posted October 20, 2016 Andyjr: If you have a shopping list of resistors and capacitors pm me. You never know what might turn up in the post Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 (edited) [quote name='3below' timestamp='1476995049' post='3159162'] Andy, are you now getting useable or even better tones from the varitone? Samhay, would you be able to model the mark1 RLC circuit? [url="http://www.flyguitars.com/gibson/bass/EB3_schematic.php"]http://www.flyguitar...3_schematic.php[/url] I am still intrigued what tfrequency response this circuit will produce taking account of the pickup as a voltage source with inductance and impedance. I do not have access to suitable modelling software (this tells me I should get some for the day job). Thanks. [/quote] Hi 3below I'm not convinced there is any really useful difference between the notch capacitor options....probably more a case of picking the best one...but I think the general difference to the main three unnotched settings is dramatic and usable. Very close in some terms to simply dropping down the tone to zero, but in someways quite different. Certainly now got a usable level of volume. Whether it is what it is supposed to sound like, I have no idea, of course, but then again nor will Pete Really grateful for all the effort and info from the three of you though - and I really do now know the difference between a low pass filter, a high pass filter , a band stop filter and a band pass filter. Trust me...that is real real progress for me and which you, BigRedX and samhay are wholly responsible Edited October 20, 2016 by Andyjr1515 Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='3below' timestamp='1476995636' post='3159176'] Andyjr: If you have a shopping list of resistors and capacitors pm me. You never know what might turn up in the post [/quote] That's very kind of you, 3below I think I'm OK - I've ordered a 20k trim pot and a .001 cap that were only a couple of £'s. A three year course in electrical systems and electronics would be useful, though, if you've got a spare one of those lying around Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted October 20, 2016 Author Share Posted October 20, 2016 [quote name='samhay' timestamp='1476980736' post='3158995'] 220n would make for an incredibly dark tone control on a passive bass or guitar. In any case, I have a good stash of caps and am happy to pop some in the post if you want to try other values. [/quote] Thanks also for the offer, samhay I should be OK I think Quote Link to comment Share on other sites More sharing options...
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