Greetings to ALL.
I know that this question may have been answered many times here. However, in Googling this question , I find several differing opinions. I have a VHT Special 6 Ultra(designed for modding). I find that this amp in stock condition(except for an upgrade in tubes), is tooo noisy, especially when high gain settings are used. The clean channel isn't bad. I found several mods meant for my amp on Rob Robinette's website. One of these is to add a choke(Hammond 157M). I quote him here ; "Adding a choke to the power supply can help quiet the amplifier by removing buzz and hum." "A choke can also alter the tone of the amp due to the "lag" induced by it's wire wound core." He recommends replacing R43, which is between the HV supply and the HV Power regulator, with the leads of the choke.
I have the choke on order, and will place it there unless there is a good reason to place it otherwise. Robinette does not really explain why this is his choice, but as I said, I have read about placing a choke otherwise, like between the PT and the OT for instance.
I would appreciate any opinions on this matter. I myself have no experience with chokes on tube amps, but I have heard comments that vary widely on the Internet, as to whether a choke will indeed reduce hum and buzz at all.
Tube amp design seems to me, to be rather a 50/50 mix of science and mystery, and as this is my first multiple modification amp, I would take ALL opinions given seriously, before I make my decision. I hope I'm not opening a "can of worms" here, but I need some real world experience, if it's out there.
Thanks in advance for ALL comments,...............tonequester.
I know that this question may have been answered many times here. However, in Googling this question , I find several differing opinions. I have a VHT Special 6 Ultra(designed for modding). I find that this amp in stock condition(except for an upgrade in tubes), is tooo noisy, especially when high gain settings are used. The clean channel isn't bad. I found several mods meant for my amp on Rob Robinette's website. One of these is to add a choke(Hammond 157M). I quote him here ; "Adding a choke to the power supply can help quiet the amplifier by removing buzz and hum." "A choke can also alter the tone of the amp due to the "lag" induced by it's wire wound core." He recommends replacing R43, which is between the HV supply and the HV Power regulator, with the leads of the choke.
I have the choke on order, and will place it there unless there is a good reason to place it otherwise. Robinette does not really explain why this is his choice, but as I said, I have read about placing a choke otherwise, like between the PT and the OT for instance.
I would appreciate any opinions on this matter. I myself have no experience with chokes on tube amps, but I have heard comments that vary widely on the Internet, as to whether a choke will indeed reduce hum and buzz at all.
Tube amp design seems to me, to be rather a 50/50 mix of science and mystery, and as this is my first multiple modification amp, I would take ALL opinions given seriously, before I make my decision. I hope I'm not opening a "can of worms" here, but I need some real world experience, if it's out there.
Thanks in advance for ALL comments,...............tonequester.
For a low power SE amplifier, I see little point of adding a choke, where is the sag coming from - it is not a PP amplifier... Anyway, a choke could reduce the hum & noise but at great expense, I would save it for another project.
It seems from your posts, that you are not too happy with the amp, or perhaps expecting too much from it. Then you may want to consider exchanging for another one, because once any mod is done to it, the value drops a great deal.
It seems from your posts, that you are not too happy with the amp, or perhaps expecting too much from it. Then you may want to consider exchanging for another one, because once any mod is done to it, the value drops a great deal.
reducing high gain noise on my VHT Special 6 ultra.
Greetings jazbo 8.
Thanks for your reply. I didn't mean to come off like I don't like the amp. Actually, It's the best sounding stock amp I've ever had(after re-tubing). It's just a more complex amp than I had expected, originally considering the plain jane Special 6(1 volume,1 tone control). It's more of a high gain amp than I expected. Now, I know that high gain often carries with it a higher noise level, but this one has too much noise in my opinion.
As for the choke, it's like I said. There are many conflicting opinions. According to some articles I have read, including Rob Robinette's VHT modding article. The choke will introduce "sag" due to the inductance of the choke. Other articles claimed that a choke would always improve the tone. At least you agree that it would reduce hum to a degree. There are even conflicting opinions on the best place to insert it into the circuit, as well as it's orientation to the OT and PT. Believe me, I'm not sold on anything yet. The mod's real easy, and easy to change back to original. One thing I need is experience, and since I have ordered the choke, I will probably give it a try at some point. However, I am looking for perhaps a more proven way to deal with the high gain noise. I actually should have lowered the gain by my replacing the first pre-amp tube with a 12ay7(gain 47). That should have cut my gain by about 25%, going by the tubes stated gain factor. I realize that this varies greatly from tube to tube, and brand to brand. Anyway, it made little difference in the way the amp sounds, in volume, AND in how much noise the high gain settings have.
I wish to thank you for being the first to post on this subject. I really appreciate your opinion, and hope to get a few more. If you have another suggestion to help with the noise problem, I'd like to hear it. Probably every member of this forum has more knowledge than I do at this sort of thing. I say one thing for sure. VHT's idea to sell a line of mod friendly amps, hand wired on eyelet board is the best idea since sliced bread in my book !
Thanks again for your reply !..............tonequester.
Greetings jazbo 8.
Thanks for your reply. I didn't mean to come off like I don't like the amp. Actually, It's the best sounding stock amp I've ever had(after re-tubing). It's just a more complex amp than I had expected, originally considering the plain jane Special 6(1 volume,1 tone control). It's more of a high gain amp than I expected. Now, I know that high gain often carries with it a higher noise level, but this one has too much noise in my opinion.
As for the choke, it's like I said. There are many conflicting opinions. According to some articles I have read, including Rob Robinette's VHT modding article. The choke will introduce "sag" due to the inductance of the choke. Other articles claimed that a choke would always improve the tone. At least you agree that it would reduce hum to a degree. There are even conflicting opinions on the best place to insert it into the circuit, as well as it's orientation to the OT and PT. Believe me, I'm not sold on anything yet. The mod's real easy, and easy to change back to original. One thing I need is experience, and since I have ordered the choke, I will probably give it a try at some point. However, I am looking for perhaps a more proven way to deal with the high gain noise. I actually should have lowered the gain by my replacing the first pre-amp tube with a 12ay7(gain 47). That should have cut my gain by about 25%, going by the tubes stated gain factor. I realize that this varies greatly from tube to tube, and brand to brand. Anyway, it made little difference in the way the amp sounds, in volume, AND in how much noise the high gain settings have.
I wish to thank you for being the first to post on this subject. I really appreciate your opinion, and hope to get a few more. If you have another suggestion to help with the noise problem, I'd like to hear it. Probably every member of this forum has more knowledge than I do at this sort of thing. I say one thing for sure. VHT's idea to sell a line of mod friendly amps, hand wired on eyelet board is the best idea since sliced bread in my book !
Thanks again for your reply !..............tonequester.
You are quite welcome. I actually have the Special 6, it's nice little amp but nowhere as versitle as the Ultra. When it is crank'd up, I too hear hum & noise BUT if I play along with backing tracks even at modest volume, they are hardly noticible but, playing by itself in a quiet room, then I can see it being a bit annoying.
Since you like the amp, and it is an easy mod, I would try out the choke, which will reduce the ripple voltage. As a general rule, you want to put the choke as the first element in the filter chain right after the rectifiers, so its effect could be felt for all the following voltage nodes. But trust me, I doubt you can get the B+ voltage to sag much with a Class A SE amp, so to me, that's just a myth. As for its orientation, again a general rule is to place the choke perdendicular/diagonal to the PT, which usually results in the least amount of interference between the two, but each amp's available chassis space and components position below the deck will also need to be factored into the placement of the choke as well.
Since you like the amp, and it is an easy mod, I would try out the choke, which will reduce the ripple voltage. As a general rule, you want to put the choke as the first element in the filter chain right after the rectifiers, so its effect could be felt for all the following voltage nodes. But trust me, I doubt you can get the B+ voltage to sag much with a Class A SE amp, so to me, that's just a myth. As for its orientation, again a general rule is to place the choke perdendicular/diagonal to the PT, which usually results in the least amount of interference between the two, but each amp's available chassis space and components position below the deck will also need to be factored into the placement of the choke as well.
Hi choke position has to be, if it is enough room, away from power transformers...
and oposite mounting against the windings of power tr...
.
adding the L just after rectifier, would significantly lower the +Vb power supply of the device.
This is the so called "L" input PS.
BUT, adding the C between the rect and Choke will make it again, "C" input.
You can start with lower values of C lets say 10uF to value little less than it was in the amp. Bare in mind Voltage of that condenser if You can put it higher value than all the rest present.
.
Anyway You will have the slight drop of +Vb because of the Dc resistance of copper wire. Inductance preferebly high BUT It is the compromise with physical value, inductance, and Dc resistance of choke...
choke has to be with gap, depending of the current of the device... 🙂
and oposite mounting against the windings of power tr...
.
adding the L just after rectifier, would significantly lower the +Vb power supply of the device.
This is the so called "L" input PS.
BUT, adding the C between the rect and Choke will make it again, "C" input.
You can start with lower values of C lets say 10uF to value little less than it was in the amp. Bare in mind Voltage of that condenser if You can put it higher value than all the rest present.
.
Anyway You will have the slight drop of +Vb because of the Dc resistance of copper wire. Inductance preferebly high BUT It is the compromise with physical value, inductance, and Dc resistance of choke...
choke has to be with gap, depending of the current of the device... 🙂
Zoran is right, I neglected to mention that the choke should be the first series element, it should be used to replace the resistor currently between the first and the second filter caps.
A choke will reduce hum, IF the hum is caused by ripple on the HV supply to start with. It could just as easy be caused by the heater circuit, or magnetic pickup between transformers, coils, wiring, and each other. Basically try it and see. Physical location may take some experimentation so test it first before drilling any holes to mount it.
If you havent used it i recomend you download PSUDII from PSUD2 and make a model of your supply, then you can start replacing the resistors with chokes and experiment with different capacitor sizes and get an idea of what difference it is going to make. I learnt a lot about CRC and CLC design from playing around with that software.
http://www.duncanamps.com/psud2/
If you havent used it i recomend you download PSUDII from PSUD2 and make a model of your supply, then you can start replacing the resistors with chokes and experiment with different capacitor sizes and get an idea of what difference it is going to make. I learnt a lot about CRC and CLC design from playing around with that software.
http://www.duncanamps.com/psud2/
Greetings Guys.
Zoran,Jazbo8, and mcandmar, I truly appreciate the info on choke usefulness, placement, and orientation. I have written all of this down, to check withthe schematic, and compare to the mod instructions from Rob Robinette's website. I don't know if this guy knows his stuff or not. He seems to be the most prolific VHT mod "designer" around so far, but that don't mean much. I'm not learned enough in electronics to do the design myself , but I do learn as I go, and I keep written records of everything, including my posts and replies. If you like sharing your knowledge, you'll find that I am your man. Right now, I have more questions than there are forums, but I take in a little at a time.
Right now, the VHT is my main project. i'm trying for an amp that is as quiet as possible as far as "noise" goes, with very little pre-amp distortion, yet plenty of output tube distortion when needed. Thanks again for sharing with me.............tonequester.
Zoran,Jazbo8, and mcandmar, I truly appreciate the info on choke usefulness, placement, and orientation. I have written all of this down, to check withthe schematic, and compare to the mod instructions from Rob Robinette's website. I don't know if this guy knows his stuff or not. He seems to be the most prolific VHT mod "designer" around so far, but that don't mean much. I'm not learned enough in electronics to do the design myself , but I do learn as I go, and I keep written records of everything, including my posts and replies. If you like sharing your knowledge, you'll find that I am your man. Right now, I have more questions than there are forums, but I take in a little at a time.
Right now, the VHT is my main project. i'm trying for an amp that is as quiet as possible as far as "noise" goes, with very little pre-amp distortion, yet plenty of output tube distortion when needed. Thanks again for sharing with me.............tonequester.
Greetings mike567.
Thanks for your feedback mike. This clarifies the issue for me. I wonder why so many feel that a choke will always make the amp sound better ? I've been posting on amps for months, and there seems to be A LOT of misinformation out there. It sure makes being a beginner tough ! Thanks again for your time and effort in setting me straight...tonequester.
Thanks for your feedback mike. This clarifies the issue for me. I wonder why so many feel that a choke will always make the amp sound better ? I've been posting on amps for months, and there seems to be A LOT of misinformation out there. It sure makes being a beginner tough ! Thanks again for your time and effort in setting me straight...tonequester.
Possibly people need to rationalize doing mods for the sake of doing mods.
There are many kinds of noise in a guitar amp. Hum is just one of them. Any "high gain" amp will tend to have more noise simply because it amplifies more.
But each source of noise has its own cure, even hum can come from 20 different causes. Hum is not generic. As mcandmar points out, the choke might reduce hum but only if the hum is the result of a lack of filtration. Adding filter caps and chokes will have zero effect on gum that comes from the heaters or the power transformer field.
Gainy amps often have more hiss than others. But hiss is a byproduct of gain, not power supply filtering, so chokes won't help that.
Look at it this way, you amp already works, and from your report, it is the best sounding stock amp you ever had. So we can't expect night and day differences. When you get into the online palaver about mod this and mod that, you are also listening to people describing their own tastes.
Imagine it is food, and we are discussing your hamburger. It is the best hamburger you ever ate. Now you want to mod your burger. How about onions? Hey, I love onions, I particularly like them grilled. Someone else prefers them raw. We can have a whole mighty discussion about it. CONFLICTING VIEWS even. And then ketchup or mustard? Bacon? Should the bacon be thin or thick sliced? Bacon crispy or flexible? WHAT can I DO? I have people telling me to use onions or not, one way or another, people telling me to use or not use mustard, et cetera. Is it misinformation? Is it just different opinions? Is it people talking about the different things but using the same words? (If you say "noise" to me, I think something other than hum. If you mean that 60Hz stuff like you get from touching your guitar cord tip, THAT is HUM, not noise.)
There are many kinds of noise in a guitar amp. Hum is just one of them. Any "high gain" amp will tend to have more noise simply because it amplifies more.
But each source of noise has its own cure, even hum can come from 20 different causes. Hum is not generic. As mcandmar points out, the choke might reduce hum but only if the hum is the result of a lack of filtration. Adding filter caps and chokes will have zero effect on gum that comes from the heaters or the power transformer field.
Gainy amps often have more hiss than others. But hiss is a byproduct of gain, not power supply filtering, so chokes won't help that.
Look at it this way, you amp already works, and from your report, it is the best sounding stock amp you ever had. So we can't expect night and day differences. When you get into the online palaver about mod this and mod that, you are also listening to people describing their own tastes.
Imagine it is food, and we are discussing your hamburger. It is the best hamburger you ever ate. Now you want to mod your burger. How about onions? Hey, I love onions, I particularly like them grilled. Someone else prefers them raw. We can have a whole mighty discussion about it. CONFLICTING VIEWS even. And then ketchup or mustard? Bacon? Should the bacon be thin or thick sliced? Bacon crispy or flexible? WHAT can I DO? I have people telling me to use onions or not, one way or another, people telling me to use or not use mustard, et cetera. Is it misinformation? Is it just different opinions? Is it people talking about the different things but using the same words? (If you say "noise" to me, I think something other than hum. If you mean that 60Hz stuff like you get from touching your guitar cord tip, THAT is HUM, not noise.)
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