Problems using CD4051 analog multiplexer - Page 1
Forum section: electronics / projects

author: Pferd
author_rank: Contributor
timestamp: November 12, 2021, 11:35:56 pm
content: Hello Forum,I am utilizing a binary resistor ladder using two analog multiplexer ICs of the CD4051 type. It is basically 14 resistors (7x 1k5 and 7x12k) in series and the two ICs short out resistors according to their given binary value. The lower 4051 controls the 12k resistors (eg the "tens") and the higher 4051 controls the 1k5 resistors, eg the "ones". They are wired up correctly as far as I know, but somehow it seems that none of the channels is selected no matter which value I give the ICs. The Inhibit Pin is tied to GND, according to the datasheet. Power to the ICs is +/-5V. My circuit has multiple of these constellations and none of them seems to work as it should. Measuring between the common pin and the individual channel pins in resistance mode always reveals a value in the tens of kohms, which doesn´t make sense at all. What am I missing, I´m stuck... I did have a small prototype of that thing utilizing very old RCA 4051s, and it worked just fine. The ones I´m using now are new TIs. I´ll attach a picture of the circuit.Thanks a lot in advance!

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 12, 2021, 11:57:22 pm
content: Swapped Vss and Vee?

author: Pferd
author_rank: Contributor
timestamp: November 13, 2021, 12:03:49 am
content: could this cause that problem? I mean, the board got printed according to my schematic, and in case I swapped them by accident there already, it could well be that they are all swapped around. Thanks for the hint!:)

author: Pferd
author_rank: Contributor
timestamp: November 13, 2021, 12:06:58 am
content: I just checked the datasheet... You're right, I did swap those around...how embarassing... I just hope I didn't blow my ICs this way. Thank you so much for your help!

author: TimFox
author_rank: Super Contributor
timestamp: November 13, 2021, 12:07:55 am
content: I had that problem (Vss and Vee swapped) in a design many years ago. Vss is actually a signal reference input (common connection for the logic input, normally ground).If the (analog) switch input can go below ground, then the power supply voltage Vee must be sufficiently negative to avoid latch-up when the analog input goes one PN diode drop negative below Vee, which is the substrate.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 13, 2021, 12:42:53 am
content: If you look up "transmission gate" schematics you should catch why it doesn't work.Most schematics around i.e.: 4066 won't show Vee though, they're shown for positive only analog switching having the N-MOS tied to GND. (or Vss which will confuse you further...)If your resistor string only sees positive voltages the quick fix would be to cut -5V supply from Vss and tie Vss pin to Vee (here GND).

author: Pferd
author_rank: Contributor
timestamp: November 13, 2021, 07:31:38 pm
content: Thanks for all the helpful information. This was indeed the problem! Unfortunately I have 20 of those ICs in my design:) I did bend up pins 7 and 8 of each IC and crossed them around using some short wire bridges. The 4053s I am also using had the same problem since they are the same power layout. It didn´t seem to damage the ICs though. I suspect because the digital level reference was shifted down to -5V, by permanently tieing the Inhibit- Pin to GND it recognized it as high, which could explain why no channel was active. But nevertheless, the analog signal is very nice now!

author: Kleinstein
author_rank: Super Contributor
timestamp: November 13, 2021, 08:01:15 pm
content: There is anotgher problem with this circuit: The 4051 on resistance of the switches is quite high. This is at least a problem for the upper of the two chips.One can improve this a little, by using 74HC4051, which have lower resitance. It is still no a good circuit.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 13, 2021, 08:38:58 pm
content: looks to me like a similar project I'm currently working on; at least I saw a valve, so I guess it's some kind of versatile guitar preamp.indeed you're better off the 74HC for this purpose; I know about the convenience of the 405x, but during my experiments it turned out, that it's working better with 4066, so 74HC4066.the same is also valid for the usage as QSE/QSD mixer, where bonding 4x 4066 switches gives better sideband rejection than the usage of a a single 4052

author: Pferd
author_rank: Contributor
timestamp: November 13, 2021, 09:18:52 pm
content: Yes, it is indeed a programmable guitar amplifier. I was playing around with the 4016 and 4066 ICs before aswell, but they were missing the digital level shifter. the 405x ICs have that already built in. I know that circuit isn´t ideal, but in a guitar amplifier things don´t necessarily need to be crazily scientific anyway, meaning it doesn´t matter if it is for example set to volume 30 or volume 31. Considering tolerances it is still around the same area of volume.You are creating a guitar amplifier aswell? What kind if I´m allowed to ask?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 13, 2021, 11:16:43 pm
content: yea, channel separation won't be a big issue in this resistor ladder you have; I recently completed a stompbox router based on 74HC4066; it ran already for many years with 8 channels, now it has 16 mono channel; kind like the Rocktron Patchmate in the 90ies. Running the 74HC4066 from 9VDC seems to be well sufficent for the channel separation signal vs bypass.well half way I'd like to follow the JMP-1 and the other half the analog part of the GSP-2101; by coincidence I could recently buy me a GSP-2101 for 100 swiss bucks; so now I kind of put the project on hold. So far I completed the 7 channel equalizer based on the GE-7, but with digital pots (MCP4451) and the compressor module based on the SSM2166, where I used a switched resistor ladder (noise gate side of the SSM2166) to replace an almost unobitanium 1Meg digital pot, but I used a different approach than you based on a MCP23017.still missing is the overdrive/distortion part and the 'glue logic' to control the stuff; so far I just implemented the equalizer control on an STM32after all I'm disappointed of the compressor part in both, the GSP-2101 and the homebrew SSM2166; they both just don't have the 'bite' of my Boss CS-3

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 08:35:20 am
content: My project is a mixture between JMP1 and Piranha. I chose the 405x ICs mainly because they are widely available and also cheap.What brings up another question I have at the moment... Is it a necessity to have a galvanic isolation on the anode voltage of the tubes? Because this could save me one transformer. All the amplifiers I've researched so far had the anode voltage winding in the main transformer. I was wondering if that is necessary at all. Since I live in a 230V country I might aswell use a fuse, bridge rectifier and some capacitors?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 14, 2021, 10:32:13 am
content: The anode voltage should still be from a transformer and not directly from main. Directly from main would mean that both sides of that supply would have potentially lethal voltage on it. With the normal bridge rectifier boith sides would be away from N / PE.If you have to ask, better don't do that.Directly rectification from mains was done in some old tube radios and TVs, but this was not very safe and with not much external connections.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 14, 2021, 12:02:15 pm
content: for sure the anode voltage should be isolated; since it's a preamp with ECC83 I guess, you could work with a simple boost converter; 10-20mA should be sufficent. On the downside you could introduce RF noise with the boost converter.For my part I got a small (<10VA) transformer 230V->60V + plus HV cascade to supply the valve anode voltage

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 12:17:03 pm
content: I currently have a self built power supply with 3 standard transformers. It's not perfect at all but for testing it does its job at the moment. It puts out +-5, +-6.3 ( I know its overkill to regulate the heater voltage), +-15 and +HV. To produce the HV I have a small print transformer with 230/2x15 backwards after a bigger 230/2x18 transformer. The high voltage is still dropping to 120V which is too less for that circuit, but using bigger transformers would mean it grows even bigger. I had a thought about switching power supplies before but they introduce noise I imagine...

author: Kleinstein
author_rank: Super Contributor
timestamp: November 14, 2021, 12:57:35 pm
content: If the 15 to 230 V transformer is very small, it could be hit by the difference between no load and nominal load voltage. With small transformers (e.g. < 3 VA) the difference can be quite large, like > 150% of no load voltage. When used in reverse the no load ouput voltage would be below some 70% and than with load could drop by another 30-50%.I would avoid a transformer much below 5 VA - in the usual chaep transformer sereis the lowest no load loss is usually around 3 VA. So a smaller transformer is also worse with the power loss.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 14, 2021, 01:07:41 pm
content: didn't make good experience with back-to-back transformers either. the load of 2 ECC83 might be rather small, but the voltage drop from such a setup could be too big in the end. Certainly a HV-cascade is rather high impedance too but it's not an unusual practice to do so for low drain valve circuits.I'd not regulate the filament voltage, but pull it on a higher voltage level than just GND; it shifts the hum on a different place in the amplification curve of the valve where the hum is less critical than on GND level.

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 01:45:50 pm
content: I can totally agree to that, since this is what I experienced aswell. It is a 1.5VA transformer. With no load it has a 245V output, but with the tubes in the sockets it has 120V for both and with only a single one it has around 160V. So it is certainly overloaded.I still want to use as few transformers as possible. The cascade sounds interesting, but I've never done this before. Maybe there is a good example of using one somewhere.I know there are special tube transformers, even in print form but I don't want to use specialized parts if possible. I thought about using a small 12v transformer without any regulation for the heaters and untie it from the GND (the center point of the heaters is currently at GND).I could even drive the Opamps with the +-5V rails, so I could exclude the +-15 aswell.

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 01:47:30 pm
content: And because the anode voltage is that low I get a really nasty clipping on the tube for the clean channel.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 14, 2021, 02:08:00 pm
content: if you heat the ECC83 with 12,6V, so the middle of the two filaments is floating, you can shift the filament voltage there on about half of the anode voltage, so ~80-90V by a voltage divider which can serve at the same time as a bleeder for the HV rectifing caps.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 14, 2021, 02:48:05 pm
content: Hi Pferd and the group,You might want to look at the circuit around U5.If you analyze this circuit:As you increase the value of R4, Rgain, the amplitude output will decrease.The output will become zero when:R3/R4 = R1/R2If you increase R4 further, the amplitude will start to increase. The signal will change from being inverted to not inverted.In your circuit R4 is programmable resistor.Regards,Jay_Diddy_B

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 03:00:27 pm
content: @Jay_Diddy_B, I am aware of that, and am even making use of that for the equalization stage. This way I can cut and boost the frequency bands utilizing this circuit. And for the volume for example it is as follows:R4 total is 94,5k, R3 is 95k, so there is a bit of security headroom to avoid it flipping to inverted where I don't want it to

author: Zero999
author_rank: Super Contributor
timestamp: November 14, 2021, 06:19:54 pm
content: Quote from: Pferd on November 12, 2021, 11:35:56 pmDid you know you can take a screenshot, by pressing the print screen key, pasting it into MS Paint and saving it as a .png file. It saves having to take a picture with your phone, reduces the image size and makes it clearer.Unfortunately it's likely you've damaged the IC, due to revering the supply voltage, but fortunately they're not expensive and are easy to get.Why not use a digital potentiometer, rather than trying to make your own?

author: Pferd
author_rank: Contributor
timestamp: November 14, 2021, 06:42:49 pm
content: I know, it was just easier for the moment to quickly take a picture:)Well, they look like they are working still... VDD was at the right place so I just flipped VEE and VSS. I don't know exactly how the ICs deal with that. The only thing I know is that none of them got warm at all during that false condition.Why I don't use Digital Pots? that's a question I can't even answer correctly... I don't know. I know that Microchip makes some affordable ones, but mostly for the 0-5V range. I would need more advanced ones suited for +-15V. They are not so easy to get and for example ones from Maxim can set you back like 5 Euros a piece.For other channel switching operations in my circuit (quite a few) I am already using 4053 ICs so I thought why not making everything with cheap 40xx ICs. I know it is not perfect or time-adequate, but I just wanted to try it this way.The original JMP1 for example was using toshiba TC9170 and TC9176 electronic volume ICs. They are specialized parts from the 90s and if one of them breaks tomorrow I have a big problem. You might be able to get one old stock on ebay, but if you do find one its around 10 Euros.I just don't want to include specialized parts not knowing how long a manufacturer keeps them alive. The 40xx ICs were made in the masses by several manufacturers and they are in production even today. It might be strange thinking, but I want to have my amplifier for a long time. Hope this makes sense.It would be something else if I had a company making that thing, then I could go out and buy a whole lot of those digital pots not having to worry about money or running out of availability of parts so much.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 14, 2021, 07:01:46 pm
content: there are ways to get the signal compatible with 5V devices like digital pots; I think I saw certain approaches in Douglas Selfs 'Self on Audio', I'll have to take look there by occasion. To avoid this problem, I used for my digitally control equalizer LMV722 opamps which have comparable parameters like a NE5532 or a LM833 but run from a single 5V supply

author: Zero999
author_rank: Super Contributor
timestamp: November 15, 2021, 11:14:48 am
content: Quote from: Pferd on November 14, 2021, 06:42:49 pmI found the MCP45HV31-104 on Mouser and it's not that expensive.https://www.mouser.co.uk/datasheet/2/268/20005304A-347268.pdfhttps://www.mouser.co.uk/ProductDetail/Microchip/MCP45HV31-104E-ST?qs=sGAEpiMZZMsX%252BY3VKDPZyDmk%2F7K7pp5vGOCPiD6M3Qtywf8IqRh4%252Bw%3D%3DQuote from: Pferd on November 13, 2021, 09:18:52 pmYou need the 74HC4316, which has a built-in level shifter.https://www.farnell.com/datasheets/308789.pdfhttps://uk.farnell.com/nexperia/74hc4316d-652/analogue-switch-quad-spst-soic/dp/2445219If you're set on making your own digital variable resistor, use two 74HC4316, and eight resistors: 400R, 800R, 1k6, 3k2, 6k4, 12k8, 25k6 and 51k2 (you might want to use the nearest E24, or E96 value for convenience), each bypassed by an analogue switch, to give a value ranging from 0, (in theory, but it will be more like 480R, due to the resistance of the switches) to 102k.https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#ListsI don't know why you'd do that, as it will probably work out more expensive than the MCP45HV31-104.Also note that it's the signal level that matters. The op-amps in your circuit can be powered off +/-15V, with the analogue switches run off +/-5V and it will work, so long as the signal through the analogue switches doesn't exceed +/-5V.It's also possible to use a 5V digital potentiometer, in a +/-15V circuit, by running it off 5V and biasing it at 2.5V, so long as the signal doesn't swing beyond +/-2.5V.The example below will work, as long as the input voltage doesn't exceed +/-2.5V. The output of the op-amp, can be much higher, as it's the voltage swing across U1 which matters. R1 and R2 bias it at 2.5V, so if the signal swings from -2.5V, to +2.5V, the voltage on U1 will range from 0V to 5V. It's also possible to do a similar thing with analogue switches run off 5V.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 15, 2021, 12:33:11 pm
content: Yup, that's a charming approach; spares a lot of headache

author: Pferd
author_rank: Contributor
timestamp: November 15, 2021, 05:01:42 pm
content: Thanks for the messages. And yes, the MCP...HV31/51 pots could work aswell. It's just a lot of options here. In fact I spent the last half year choosing back and forth between the various solutions till it nearly drove me crazy. The agony of choice...The 4316 is a pretty modern chip, right? It's like a better version of the old 4016 plus a level shifter.I get the idea of referencing the signal to 2.5V to get the swing from 0 to 5V, but doesn't that introduce some other problems? For example when fitting this into the rest of the circuit that's all referenced to GND?I have been thinking about running my opamps from the +-5V aswell, so I don't risk overloading my 4051s.Some of the old 4053 datasheets even state that the analog level on the switches is not limited to the supply voltage. Correct me if I'm wrong, but I think I do remember reading about 20Vpp in one of those old datasheets. There are for example no measurable clamping diodes on those switch pins, at least on the ones I tested so far.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 15, 2021, 05:21:38 pm
content: The old 405x are still limited to the supply. They can however use a supply up to +-10 V (20 V total with some types). For even higher voltages there are the DG408/9. In normal times they were also relatively affordable and available from multiple sources (though the cheap ones mainly Vishay).There is also the option to use an multiplying DAC (DAC08 , AD7523, TLC7528 or similar). One can also build the corresponding circuit with HC4053 switches. So a similar effor as the shown circuit, but less sensitive to the on resistance and working also for a higher signal voltage as the switches are current steering.Audio Levels may want a more log scale for the gain. A linear adjustment may not really use all steps. and still have a limtied range.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 15, 2021, 05:39:15 pm
content: Quote from: Kleinstein on November 15, 2021, 05:21:38 pmThat's a good point here.If you're using a digital pot for adjusting audio levels, a log scale is the way to go. If you're implementing your own digital pot, you can do that. If you're gonna use an off-the-shelf one, it will limit your options.You can read this:https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/1828.htmlThere are dedicated volume control ICs too. TI has a few PGAxxx chips that are pretty good, but definitely not cheap. Cirrus also have some. There's an 8-channel version that could be used if you need a number of channels, in a single package. It IS expensive.

author: Zero999
author_rank: Super Contributor
timestamp: November 15, 2021, 05:39:46 pm
content: Quote from: Pferd on November 15, 2021, 05:01:42 pmYes, it's a more modern part, but as far as I'm aware, it's only available in 74HC, which is limited to +/-5V maximum.QuoteThat's not a problem, if the potentiometer is connected to the rest of the circuit via capacitors, which block DC. The op-amp inputs in the schematic attached to my previous post, swing between -2.5V and +2.5V.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 15, 2021, 06:54:06 pm
content: from my experience so far with guitar related circuits, there's enough headroom running signals through 5VDC devices; in the end it even happened, that I had to reduce the signal level before giving them on the amps.Considering the fact, that stompboxes run from 9V with opamps like a TL074, biased to vcc/2 and an opamp which is far away from being rail to rail, you have about +/-2V maximally +/-2,5V headroom for the signal, while on the other hand many of those audio devices running on 5V are RRIO, it's not really a problem.

author: Pferd
author_rank: Contributor
timestamp: November 15, 2021, 08:38:55 pm
content: Oh, ok, I get it, so the older ones had a overall higher voltage rating. But since I don´t need 20Vpp, I´m fine with the newer ones:)For my project I was studying various digitally controlled preamps from the 90s era, to see how the individual ones accomplish the digital control of the analog circuit. For example the Rocktron piranha was using 4 dual MDACs, Maxim type MX7528. The positive point here is that they did various different configurations to control various different circuits with the same DAC, eg levels and frequency selection.What are those HC4053s you are mentioning? Are they a special kind of the 4053, or do you mean the 74HC4053? I heard the 74 series is better when it comes to the on-resistance.That´s a very good point here. I know that for volume often a log pot is used. My self built ones are all linear, because they are switching up in binary. I had various different approaches using switches to bridge or connect or short resistors, but due to the binary control, which is kind of essential to keep the part count down, I can´t get my head around how I could make one logarithmic one. With those "custom" various resistors utilizing switches it is indeed possible to create a very custom one, but logarithmic is difficult... Using a DAC with for example 8-bit and utilizing an array of the attenuation steps could create a pseudo-logarithmic scale. Would be more than good enough in my case aswell. But I´ll test the amplifier the way it is and then I can start complaining about what I don´t like and improve it. theoretically I can just swap out the attenuation stages I used with more modern ones like DACs or volume control ICs if I need to. It wouldn´t require much except than getting some new boards made. I have to anyway because of the partly embarassing mistakes I made on the first one. I guess working on it during late night hours does show the things I missed in the end:DYes, I do think a headroom of 2V is good enough. Most of the signals in my circuit don´t really exceed 1Vpp.

author: Pferd
author_rank: Contributor
timestamp: November 15, 2021, 10:01:45 pm
content: I just have to ask again about the cascade for the tube supply real quick... I found this circuit on wikipedia on high voltage cascade. Is something like that what you recommended?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 15, 2021, 10:18:07 pm
content: there are no digital log pots; if logarithmic curve is needed, it has to be done in software, what is no big thing.one of the advantages of the way you took (resistor cascade and the 4053) is the possibility of modelling a logarithmic curve, so you could consider it as a feature and not as a bug.the villard cascade is one possible way to create HV, but keep in mind that with every element (diode + cap) more, the internal impedance increases, so it still might make sense using a small (10VA) 230V->60V transformer and only few cascade elements to keep the impedance in an acceptable range.

author: TimFox
author_rank: Super Contributor
timestamp: November 15, 2021, 10:25:14 pm
content: Quote from: HB9EVI on November 15, 2021, 10:18:07 pmThere is a method for digital switching logarithmic voltage dividers: the standard switched attenuator with a binary sequence of attenuation values (in dB). Normally, each cell requires a DPDT (2-C) switch, but I believe that there are less complex switch forms. I remember an article from almost 50 years ago about a switched attenuator network like this for use in a non-linear successive-approximation ADC: I believe it appeared inReview of Scientific Instrumentssometime around 1975, but I don't have the citation. Of course, such an attenuator is subject to serious "major carry" glitches if the high-value attenuators are not sufficiently accurate.

author: Pferd
author_rank: Contributor
timestamp: November 15, 2021, 10:35:05 pm
content: If anybody knows where I can find that article, it would be really interesting for future use maybe, in case I get annoyed by my linear attenuation.And yes, that's what I had in mind, to take the highest voltage standard transformer I can find (230/2x30V I think) and use only a few cascade steps after it. It will at least be in every way better than the two transformers back to back.The circuit in the original amplifier, which was utilizing two ECC83 tubes aswell, drew around 1.7mA at 250V. So I guess I should create a powersupply that is suitable in that range. I'll just try that villard cascade and some extra filter caps.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 15, 2021, 11:44:36 pm
content: Quote from: HB9EVI on November 15, 2021, 10:18:07 pmHere a quick search on Mouser shows 109 logarithmic digital potentiometers.

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2021, 12:36:31 am
content: With rotary pots, a cheap quasi-log control can be made by loading the output of a linear pot with a suitable resistance. For example, a “slugging” resistor equal to half the pot value is somewhat “loggish” down to -20 dB.That’s not great for an accurate attenuator, but linear pots are more repeatable than log pots, so this trick is used for mixers, etc., to obtain equal results on multiple channels.

author: Pferd
author_rank: Contributor
timestamp: November 16, 2021, 05:57:38 am
content: I've seen that before I think. And even while I was simulating my circuit in LtSpice I noticed it is a little bit exponential by itself, so I connected it accordingly already to use that bit of logarithm

author: Zero999
author_rank: Super Contributor
timestamp: November 16, 2021, 08:52:18 am
content: Quote from: Pferd on November 15, 2021, 10:01:45 pmI thought you didn't need a higher voltage? The problem with a charge pump is an oscillator is required to drive it, assuming there isn't an AC power supply available, giving ripple on the output.Quote from: Pferd on November 15, 2021, 08:38:55 pmHow about using a digital volume control IC? The PGA2311 has a programmable gain/attenuation from +31.5 dB to −95.5 dB, in 0.5 dB steps. Fair enough, it isn't cheap, but it saves a lot of bother. The only downside is it has fairly stringent power supply requirements of +/-5V, so if you want to run it off batteries, you'll need two 9V batteries and a couple of low drop-out regulators, or a switched mode power supply.https://www.ti.com/lit/ds/symlink/pga2311.pdf

author: Pferd
author_rank: Contributor
timestamp: November 16, 2021, 11:34:50 am
content: I plan on running it off 230V mains anyway, so after the 60V transformer I would have an AC source that can feed my villard cascade. It's 50Hz only, but I think by choosing the right caps it should work.I have to keep my power supply rather small, hence why I willalso try to run the Opamps from sym 5V like the switches rather than sym 15V.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 16, 2021, 03:02:07 pm
content: yup, found some log pots too; likely passed my mind when I was in need for one the last time i searched; problem remains, that the selection is not too big.with a 60VAC transformer you should reach stable reliable ~180VDC with a triple cascade; I used 22u/350V electrolytes for the cascade; it requires though always double checking on which end of the cascade is which polarity

author: Zero999
author_rank: Super Contributor
timestamp: November 16, 2021, 03:08:35 pm
content: Quote from: HB9EVI on November 16, 2021, 03:02:07 pmThe peak voltage of 60VAC RMS is nearly 85V, so you'll get over 180VDC, from a 60V transformer, with a voltage doubler. Unfortunately there will be some ripple. Whether it's acceptable or not, depends on the circuit.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 16, 2021, 03:16:15 pm
content: sure, but I said 'stable' - that includes RC filtering and the actual anode current drain; those were at least the results from my tests with this kind of setup feeding twice time 2 ECC83 triodes.

author: Pferd
author_rank: Contributor
timestamp: November 16, 2021, 08:44:31 pm
content: I´ve done some more testing this evening and solved a few issues I had.At this point I do think against my first assumption that at least some of my 4051s have suffered some damage from the wrong polarity on VEE and VSS. Some of them began losing their channel contact randomly, meaning they jumped into the inhibit state. Maybe this has something to do with the current running backwards out of the INH-pin/module, assumingly. When I touch the resistor ladder at a specific place, which is always different, it starts making contact again. It´s not a loose connection, I checked that many times.But at least while it is making contact it produces a very good and non-noisy sound, exactly what I wantd it to sound like, so it is a good day today anyway. It´s almost entirely silent when turing the guitar volume to zero (at the guitar). The next step would be swapping out the chips to see if that solves the problem.Then I just have to deal with an oscillating op-amp and the power supply. I bridged the oscillating one for now, because it was getting really warm and created nasty loud sqeak-sounds.