For you guys using the CD4049UBE, how are you guys getting around the gating? No matter what, I hear a slightly unbiased gating sound in the tail of the note. Even when I apply a DC bias to the input, I still hear it. I remember having this problem with the Insanity (subsequent versions). I wonder if it's the make of the chip. For you guys not getting gating, where did you get your chip and what brand etc...?????
I seem to be fairly unlucky with cmos builds ! ... however the best results I've had are from using
TI chips ( 4049UBE ) these are from Smallbear.
I also have some 4069UBE's with an " ST " logo, ( ST Microelectronics ) which seem to be fine.
I think these came from ESR.
My recent UBE-screamer for instance, when set for high gain produces a sort of gated/digital cut off
But low to medium gain is 100% perfect ! ?
MM.
OK, I used (http://www.diystompboxes.com/smfforum/Themes/classic/images/english/search.gif), and found this (http://www.diystompboxes.com/pedals/insanity.GIF) schemo.
Haven`t ever built it, but the large 10µ cap at the inverter`s output might give it a hard time to charge/discharge it with the limited inverter`s drive-capabilty/high output-Z.
I`d try 100nF.
just a thought...
I think it has something to do with the supply voltage, or possibly the supply current. If I use a fresh 9V battery to power it, at high gain settings I do notice the trailing effect. However, if I use a battery that is maybe half drained, the trailing seems to go away. I think it could be more of a current issue, though, because I noticed if using sections as oscillators the pitch is affected by supply current, not voltage.
Justin
QuoteIf I use a fresh 9V battery to power it, at high gain settings I do notice the trailing effect. However, if I use a battery that is maybe half drained, the trailing seems to go away.
Interesting. I am using a low ohm resistor to limit current. I will try different values. I will also try a reduced voltage and see what happens.
I am using a Ti CD4049UBE. I am not making the Insanity. I am trying to breadboard a more simple design as a test.
Thanks!
Aron
That would be a great test. Let me know what you find.
Justin
Quote from: aron on November 08, 2006, 01:25:00 PM
QuoteIf I use a fresh 9V battery to power it, at high gain settings I do notice the trailing effect. However, if I use a battery that is maybe half drained, the trailing seems to go away.
Interesting. I am using a low ohm resistor to limit current. I will try different values. I will also try a reduced voltage and see what happens.
Thanks!
Aron
I just tried using a battery reading 6.4v and it made no difference .... hmmm ... onwards !
( I just had less overall volume )
MM
Quote from: MartyMart on November 09, 2006, 06:29:05 AM
I just tried using a battery reading 6.4v and it made no difference .... hmmm ... onwards !
( I just had less overall volume )
Yeah, hmm.. I just tried it too, and this time it did not work. Maybe I'm just an idiot.
Justin
I won't have time to test until tomorrow. This is very troubling. I wonder how Mark Hammer's pedal works.... is there gating?
Are you guys direct coupling the stages or are you bypassing with a capacitor? I wonder if that makes any difference? (Doubt it).
Quote from: aron on November 09, 2006, 01:16:39 PM
Are you guys direct coupling the stages or are you bypassing with a capacitor? I wonder if that makes any difference? (Doubt it).
You can either way depending on the circuits needs. If you need to you can rebias the signal on the input either through changing the feedback amount or putting on a dedicated bias control like in the schematic Puretube linked to.
Andrew
Quote from: aron on November 09, 2006, 01:16:39 PM
I won't have time to test until tomorrow. This is very troubling. I wonder how Mark Hammer's pedal works.... is there gating?
Are you guys direct coupling the stages or are you bypassing with a capacitor? I wonder if that makes any difference? (Doubt it).
I've never knowingly experienced any sort of gating with 4049-based pedals. I'm not saying I don't encounter it, just that I've never noticed it. Is this the sort of thing that studio quality sound/levels would be required to detect?
I brought one to a store on Saturday for Hairyandy (from the forum here), the guy who makes the Retro-Sonic pedals, and the guy who owns the store to try out. They played it through some sort of boutique-ey Tweed Deluxe and nobody reported any sort of odd nuances to the tail of the notes.
You used the same circuit, Mark?
I used this but without the frequency booster segment, and with a 1-10uf cap between points A and B.
http://img.photobucket.com/albums/v474/mhammer/Forty-Niner.gif
ah: it`s got the inverters decoupled by a 0.1µ...
QuoteIf you need to you can rebias the signal on the input either through changing the feedback amount
Andrew,
Can you elaborate on this? Do you simply mean changing the feedback resistor?
Mark,
I directly coupled 3 stages together, used 100K resistors as feedback resistors. I tried with 1M input resistance to ground and without (like yours). I am assuming your 9V+100uF cap is to pin 1 for supply voltage.
I didn't try decoupling yet.
Thanks,
Aron
One more question - how DO you bias this chip? Is it internally biasing or???? AFAIK Mark's schematic and others do not apply any DC bias to inputs.
Quote from: aron on November 09, 2006, 04:24:56 PM
Mark,
I directly coupled 3 stages together, used 100K resistors as feedback resistors. I tried with 1M input resistance to ground and without (like yours). I am assuming your 9V+100uF cap is to pin 1 for supply voltage.
Yes on the last question.
I've actually never built anything using 4049's without the decoupling. What does the old Hot Tubes use?
The MXR uses coupling.
http://www.montagar.com/~patj/mxrhott.gif
OK, WHY am I not coupling? ???
I can`t contribute to all those known "TSF" & "HT" circuits that flood the web,
coz I never tried them.
But I read that the inverters are automatically biased to Ub/2 by the feedback R from out to in. (Datasheests, App-Notes, & RayMarston).
Also I read that they work like inverting opamps with an (input) series-R
and a feedback-R.
Now when you don`t use a series-R, you`re attempting to rise the gain to infinity,
which doesn`t work with this chip.
The other thing I can imagine is,
that if additionaly to not having a series-input-R
and there being no decoupling cap between the stages,
the individual inverters *might* have slightly different "mid"-voltages
they are trying to bias to with the help of the feedback-resistor,
but that the slight difference between those "mid" voltages is the "threshold"
below which the signal gets "gated".
:icon_question:
yes: I designed a couple of CMOS inverter based circuits over the past year,
but these aren`t comparable in topology with those "wellknown" pedals...
Quote from: aron on November 09, 2006, 04:42:35 PM
The MXR uses decoupling.
http://www.montagar.com/~patj/mxrhott.gif
OK, WHY am I not decoupling? ???
Me thinks you mean 'coupling' capacitors? Decoupling is what you do to the power supply, coupling (as in AC coupled) is what you do in the signal path. You are DC-coupling the stages.
--john
uh yeah - coupling. ;D
From what Puretube said, shouldn't there be series resistors as well? Too bad I can't try it tonight. Anyway, I will find out tomorrow.
Quote from: aron on November 09, 2006, 06:58:55 PM
From what Puretube said, shouldn't there be series resistors as well? Too bad I can't try it tonight. Anyway, I will find out tomorrow.
The series resistor allows you to set the amount of gain just like you would for an inverting amplifier. If you use the series resistors in this way I would get rid of the series resistor in the power supply because this also lowers the gain of the invertors.
--john
some call them coupling caps coz they link 2 stages,
some call them de-coupling caps coz they de-couple 2 stages DC-wise,
some call them blocking caps coz they block DC between 2 stages.
series-input-resistors make the stages more predictable.
series-input-caps serve as frequency-dependant resistors here, too.
the lower the power-supply voltage, the higher the max-gain
(AN-88, fig.5).
don`t expect a max gain of more than 30 to 50 times per stage in practical circuits...
Quote from: aron on November 09, 2006, 04:42:35 PM
The MXR uses coupling.
http://www.montagar.com/~patj/mxrhott.gif
OK, WHY am I not coupling? ???
Quick! Kill it before it spreads!!!The
Electro-Harmonix Hot Tubes,
NOT MXR. That was RG's old typing error that ended up being in mirror sites around the world that used the LEPER's schematic archive from Jaimie Heilman. Honest to god, it couldn't be worse if he had had some youthful indiscretion and briefly appeared in a nudie flick. It's like one of those bad dreams that will simply not go away.
Now, apart from that brief panic attack, yes THAT one, and it does use a combination of coupling caps AND input resistors.
QuoteNever trust a schematic on the web!
:icon_razz:
and: make that the so-called "Vintage E-H Hot Tubes"...
(the current,
not: "re-issue" E-H Hot Tubes works on 2x 12AX7).
And to answer another question from a different thread:
those both have plate-/cathode-/& grid-resistors... :icon_wink:
Yes. My bad. I'm usually good about noting that, and missed it this time.
Of course, it's an even bigger source of misunderstanding when the "old" HT doesn't use tubes, the current one does, the company that makes them in the new form continues to produce catalog items from the same era as the old HT essentially unchanged (e.g., Dr. Q, BMP), and the NAME of the pedal has the word "tubes" in it. Yeesh!! How many potential sources of misunderstanding can you get in one place?! :icon_eek:
Quote from: puretube on November 10, 2006, 01:50:36 AM
some call them coupling caps coz they link 2 stages,
Right AC-coupled
Quote from: puretube on November 10, 2006, 01:50:36 AM
some call them de-coupling caps coz they de-couple 2 stages DC-wise,
Never heard this before.
Quote from: puretube on November 10, 2006, 01:50:36 AM
some call them blocking caps coz they block DC between 2 stages.
Yes, I've heard it referred to in this way as well.
Quote from: puretube on November 10, 2006, 01:50:36 AM
series-input-resistors make the stages more predictable.
series-input-caps serve as frequency-dependant resistors here, too.
agreed.
Quote from: puretube on November 10, 2006, 01:50:36 AM
the lower the power-supply voltage, the higher the max-gain
(AN-88, fig.5).
But
not when it is lowered through a current limiting resistor without heavy
de-coupling caps on the supply pin. (forgot that part before, my bad)
Quote from: puretube on November 10, 2006, 01:50:36 AM
don`t expect a max gain of more than 30 to 50 times per stage in practical circuits...
Yes, for the unbuffered version.
--john
most circuits discussed here for these kinda purposes are talking bout unbuffered...
note:
Quotein practical circuits
... :icon_wink:
Aron`s schemo doesn`t mention "buffered" or not...
I automatically thought they were intended to be... :icon_redface:
btw:
QuoteQuote from: puretube on Today at 07:50:36
some call them de-coupling caps coz they de-couple 2 stages DC-wise,
Never heard this before.
from an old tube-book (1937)
:icon_smile:
Quote from: Mark Hammer on November 10, 2006, 12:55:23 PM
Yes. My bad. I'm usually good about noting that, and missed it this time.
Of course, it's an even bigger source of misunderstanding when the "old" HT doesn't use tubes, the current one does, the company that makes them in the new form continues to produce catalog items from the same era as the old HT essentially unchanged (e.g., Dr. Q, BMP), and the NAME of the pedal has the word "tubes" in it. Yeesh!! How many potential sources of misunderstanding can you get in one place?! :icon_eek:
`
I`s just joking... :icon_smile:
I believe the DC blocking caps worked. It seems to work fine, but there's massive amounts of distortion. So much so that I can't really prototype on my breadboard. There's too much oscillatiion.
I'm going to move toward perfboard.
I'm glad that worked aron, the few that I have problems with DO have blocking/coupling whatever caps
too and still have gating / farting issues ..... :icon_sad:
Still, I have a working Red Lama and a ROG double D !
MM.
Yep, mine have coupling caps as well and I still get the gating at the end of notes, or when the input is below a certain threshold. Since it is oscillating at a low threshold, wouldn't pull down resistors between stages do the trick?
Justin
then which circuit do You use?