Just wondering what types of caps you blokes use for treble bleed/fizz/ice pick reduction in high gain amps and where you prefer to fit them?
I want to try some different types, from the film caps I have been using, to hear what, if any, tone differences there are.
Also, do you hear much difference in tone between; anode (plate) resistor bypass, anode to ground, after coupling cap to ground, grid to ground, before grid-stopper to ground.
Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
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Stevem
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Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
The more caps you have in any circuit the more potential adverse problems you can have!
I would first try something far easier and cost basically nothing in parts.
Solder a lenght of wire to the plate of a preamp tube that is long enough to rap around that gain stages unsheilded grid wire 2 to 4 times (depending on the change in frequency response you get ) spread out across the length of 1”.
This will introduce inverse feedback and cut back on some of the unwanted top.
Be sure to insulate the end of this wire with shrink tubing!
This will have the most effect on gain stages that are clipping the hardest.
Note that since with large enough signal input to a gain stage, that at a certain overdrive level the gain stage will jump right into cut off on the bottom of the input wave, while still possibility growing into saturation clipping on the top half of the wave.
Determining this point of clipping is where having a Scope can save some time and allow you to clearly see what’s going on besides hearing it!
The cut off of the input signal produces much more of the fast increase of brash harmonics that you want to gain control over then does the saturation and clipping that takes place to the top of the wave form!
What this all means is that whatever you try out will need to likely be done on two gain stages to completely smooth things out should you want such.
Forgive my hand drawn picture, but this is how phase changes with/ to any signal going thru a gain stage.
I would first try something far easier and cost basically nothing in parts.
Solder a lenght of wire to the plate of a preamp tube that is long enough to rap around that gain stages unsheilded grid wire 2 to 4 times (depending on the change in frequency response you get ) spread out across the length of 1”.
This will introduce inverse feedback and cut back on some of the unwanted top.
Be sure to insulate the end of this wire with shrink tubing!
This will have the most effect on gain stages that are clipping the hardest.
Note that since with large enough signal input to a gain stage, that at a certain overdrive level the gain stage will jump right into cut off on the bottom of the input wave, while still possibility growing into saturation clipping on the top half of the wave.
Determining this point of clipping is where having a Scope can save some time and allow you to clearly see what’s going on besides hearing it!
The cut off of the input signal produces much more of the fast increase of brash harmonics that you want to gain control over then does the saturation and clipping that takes place to the top of the wave form!
What this all means is that whatever you try out will need to likely be done on two gain stages to completely smooth things out should you want such.
Forgive my hand drawn picture, but this is how phase changes with/ to any signal going thru a gain stage.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
Stevem,
I haven't had any adverse problems with my high gain amp work, related to treble reducing caps but, that is an interesting idea to try.
So you use bare wire and only insulate the end? Should the wire be wrapped tight?
My scope is my friend.
I haven't had any adverse problems with my high gain amp work, related to treble reducing caps but, that is an interesting idea to try.
So you use bare wire and only insulate the end? Should the wire be wrapped tight?
My scope is my friend.
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I recall Dumble tends to use 'anode to grid', and 'anode to cathode' caps to achieve treble roll off, others here might be able to provide more detail / schematic examples.
As for the former, I can't see how the degree of clipping might affect the degree of feedback.
And with the latter, my experience is (and my oscilloscope shows) that the opposite is actually the case, ie that the 'cut off' bottom peaks tend to be more rounded that the upper 'grid clipped' peaks, unless the cathode is left unbypassed.
In regard of valve operation, 'saturation' is a specific thing, it means that anode current can't increase any further due to the electron cloud generated by the cathode being depleted. My understanding is that receiving valves aren't operated anywhere near saturation, ie there's always a significant surplus in the electron cloud around the cathode.
Apologies for the pedantry, I acknowledge that ‘saturation’ tends to be used colloquially to have the same meaning as 'overdrive', but as this is a technical forum, it’s best to not use the terminology that we got inappropriately.
Could you clarify how you have determined the above 2 points?Stevem wrote: ↑Thu Apr 01, 2021 11:31 am...
This will have the most effect on gain stages that are clipping the hardest.
...
The cut off of the input signal produces much more of the fast increase of brash harmonics that you want to gain control over then does the saturation and clipping that takes place to the top of the wave form!
...
As for the former, I can't see how the degree of clipping might affect the degree of feedback.
And with the latter, my experience is (and my oscilloscope shows) that the opposite is actually the case, ie that the 'cut off' bottom peaks tend to be more rounded that the upper 'grid clipped' peaks, unless the cathode is left unbypassed.
In regard of valve operation, 'saturation' is a specific thing, it means that anode current can't increase any further due to the electron cloud generated by the cathode being depleted. My understanding is that receiving valves aren't operated anywhere near saturation, ie there's always a significant surplus in the electron cloud around the cathode.
Apologies for the pedantry, I acknowledge that ‘saturation’ tends to be used colloquially to have the same meaning as 'overdrive', but as this is a technical forum, it’s best to not use the terminology that we got inappropriately.
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Stevem
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Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
Ngw, the wire should be insulated .
The thicker the insulation the more wraps you may need to use to make for a change being heard.
The thicker the insulation the more wraps you may need to use to make for a change being heard.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
Someone please correct me if I am wrong, but if any given preamp tube is not biased in the exact center of its conductance range, then either the clipping point of the top of the wave and or the cut off point of the bottom of the wave will be different.
With all the verifiables that would have to go into Biasing any given preamp tube to its exact center for balanced voltage gain response then if for instance cut off takes place first on the bottom of the wave while the top is still progressing into harder clipping, then you have the high end / treble response of a different type / sound taking place.
Cut off to me is like a light switch, in that when it’s off that’s it there’s no light anymore ,where as in this example saturation on the top of the wave form once again to use the light example would just get progressively dimmer until there’s no light.
For a wide dynamic play feel in terms of the distorted sound of a amp, I myself have never been fond of the tone produced by fast hard clipping, which is also why I prefer a amp that has little to no global feedback in it.
To get the needed amount of tight bass response that I like for when the amps output stages is pushed hard into clipping I prefer to have enough main filtering and may be SS diodes and no tube recto.
With all the verifiables that would have to go into Biasing any given preamp tube to its exact center for balanced voltage gain response then if for instance cut off takes place first on the bottom of the wave while the top is still progressing into harder clipping, then you have the high end / treble response of a different type / sound taking place.
Cut off to me is like a light switch, in that when it’s off that’s it there’s no light anymore ,where as in this example saturation on the top of the wave form once again to use the light example would just get progressively dimmer until there’s no light.
For a wide dynamic play feel in terms of the distorted sound of a amp, I myself have never been fond of the tone produced by fast hard clipping, which is also why I prefer a amp that has little to no global feedback in it.
To get the needed amount of tight bass response that I like for when the amps output stages is pushed hard into clipping I prefer to have enough main filtering and may be SS diodes and no tube recto.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
For a single ended stage, clipping at the top and bottom will typically be a little different, due to the different mechanisms doing the clipping. Merlin goes into some depth explaining this stuff. http://www.valvewizard.co.uk/Common_Gain_Stage.pdf
How rounded the actual overdriven waveform is at the top compared to the bottom will largely depend on the surrounding circuitry, see p15 onward.
How rounded the actual overdriven waveform is at the top compared to the bottom will largely depend on the surrounding circuitry, see p15 onward.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
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Stevem
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Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
And it’s that surrounding circuitry that biases the tube and other then the voltages applied to the tube and the amount of signal swing your needing by that circuitry for down stream stages, then it’s the tube that is the biggest wild card!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
Stevem,
insulated wire makes more sense.
I dont think a bare wire, attached to HT (and wrapped around the low voltage grid, where you don't expect to find HT), would be a good idea and not something I would do anyway.
pdf64,
thanks for the interest and comments.
The discussion is moving into the description of distortion characteristics.
To hear other opinions and experiences is always interesting in the realm of amp overdrive, but I would still like to hear opinions on treble bypass capacitor types & dielectrics and what your observations have been and what you find to work best.
I also like to hear about overdrive and distortion experiences, since caps have a major effect.
I am sceptical about the 'mystical mojo' surrounding capacitor types used in passive/treble attenuation tone controls, in amps and guitars; but I could be wrong and I am always looking for ways to improve the tone that my customers want to hear, so all info is valuable, even if some of it is discarded.
Thanks for the comments and opinions.
Cheers, Noel
insulated wire makes more sense.
I dont think a bare wire, attached to HT (and wrapped around the low voltage grid, where you don't expect to find HT), would be a good idea and not something I would do anyway.
pdf64,
thanks for the interest and comments.
The discussion is moving into the description of distortion characteristics.
To hear other opinions and experiences is always interesting in the realm of amp overdrive, but I would still like to hear opinions on treble bypass capacitor types & dielectrics and what your observations have been and what you find to work best.
I also like to hear about overdrive and distortion experiences, since caps have a major effect.
I am sceptical about the 'mystical mojo' surrounding capacitor types used in passive/treble attenuation tone controls, in amps and guitars; but I could be wrong and I am always looking for ways to improve the tone that my customers want to hear, so all info is valuable, even if some of it is discarded.
Thanks for the comments and opinions.
Cheers, Noel
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I’m no expert. And, I don’t really go for “high gain” modern amp circuits.
I have tried low pF ceramic disc caps at times to address oscillation issues. I usually only add them as needed, experimenting with where works best for each build.
I had one build (on a PCB) that benefited by placing 100pF (I think?) from plate to plate on V1. The amp would howl with treble and volume at max. I tried placing the cap across the either plate resistors, but it only worked between the plates of the first two gain stages.
On a recent build I used a 100pF across the plate resistor of the inverting side of a long tail pair. Honestly, I built with this cap included from the beginning. So, I did not get a before and after impression. The amp sounds great so I’m reluctant to mess with it.
I have tried low pF ceramic disc caps at times to address oscillation issues. I usually only add them as needed, experimenting with where works best for each build.
I had one build (on a PCB) that benefited by placing 100pF (I think?) from plate to plate on V1. The amp would howl with treble and volume at max. I tried placing the cap across the either plate resistors, but it only worked between the plates of the first two gain stages.
On a recent build I used a 100pF across the plate resistor of the inverting side of a long tail pair. Honestly, I built with this cap included from the beginning. So, I did not get a before and after impression. The amp sounds great so I’m reluctant to mess with it.
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I will offer my very non-technical opinion on "Ice Pick" and then let the big brains come in and tell me where I'm misinformed but still hopefully provide some insight
In researching ways to kill the ice pick I had tried anode bypass caps as a solution but every time it killed all the high end upper harmonics that I loved
I also tried this to get rid of squeal/parasitic oscillation with negative results as well. Turns out this is almost always a lead dress problem anyways
Seems that the ice pick is actually in the upper mid frequencies 1.5k-3k range where the human ear is most sensitive
Using anode bypass caps is pretty much a low pass filter at a fairly high frequency well above the ice pick, so once you've removed the ice pick you have also removed much clarity
I can see how they are useful for smoothing the high fizz though if that is what you are trying to achieve
Take a look at the first couple paragraphs here for a better explanation and possible solutions
https://robrobinette.com/Voicing_an_Amp.htm
Edit: Some speakers seem to have the icepick built into them too so make sure that is not the problem
Todd
In researching ways to kill the ice pick I had tried anode bypass caps as a solution but every time it killed all the high end upper harmonics that I loved
I also tried this to get rid of squeal/parasitic oscillation with negative results as well. Turns out this is almost always a lead dress problem anyways
Seems that the ice pick is actually in the upper mid frequencies 1.5k-3k range where the human ear is most sensitive
Using anode bypass caps is pretty much a low pass filter at a fairly high frequency well above the ice pick, so once you've removed the ice pick you have also removed much clarity
I can see how they are useful for smoothing the high fizz though if that is what you are trying to achieve
Take a look at the first couple paragraphs here for a better explanation and possible solutions
https://robrobinette.com/Voicing_an_Amp.htm
Edit: Some speakers seem to have the icepick built into them too so make sure that is not the problem
Todd
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I think the OP question was concerning if the type of capacitor made a difference (not the pros and cons of adding anti-fizz caps)?
I think small caps are very similar in sound, but a ceramic disk or mica cap has the lowest impedance at really high frequencies, so if you have dog hearing you might notice a difference.
I think small caps are very similar in sound, but a ceramic disk or mica cap has the lowest impedance at really high frequencies, so if you have dog hearing you might notice a difference.
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
In that case I use which ever type I have on hand
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I finally got back to this after a few days of very bad internet access, thanks to my service provider.
I am more interested in types of caps (and dielectrics) and where to put them, based on the experience of other members.
My thoughts have been, that using ceramic caps for signal removal, has very little (if any), effect on the rest of the circuit's tone, apart from removing the unwanted part of the signal.
I started this topic to get comments on whether this is other members' experience and if not, what do you blokes recommend.
Although, I would welcome any helpful comments on the pros and cons of anti-fizz caps and alternative fixes.
Cheers, Noel
^^^ What Mark said.by mhuss » Sat Apr 03, 2021 4:45 am
I think the OP question was concerning if the type of capacitor made a difference (not the pros and cons of adding anti-fizz caps)?
I think small caps are very similar in sound, but a ceramic disk or mica cap has the lowest impedance at really high frequencies, so if you have dog hearing you might notice a difference.
I am more interested in types of caps (and dielectrics) and where to put them, based on the experience of other members.
My thoughts have been, that using ceramic caps for signal removal, has very little (if any), effect on the rest of the circuit's tone, apart from removing the unwanted part of the signal.
I started this topic to get comments on whether this is other members' experience and if not, what do you blokes recommend.
Although, I would welcome any helpful comments on the pros and cons of anti-fizz caps and alternative fixes.
Cheers, Noel
Re: Treble bleed/Fizz/Ice Pick reduction Bypass Caps - What types do you blokes use
I’m a fan of LCR polystyrene for sub 1nF axial caps.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!