Hi all,
I've been very interested in power scaling for a long time. I read Kevin O'Connors books a couple of years ago, and after reading a lot on this board, I started wondering how the different "products" (so to speak) differ from each other.
http://geocities.com/ge0ne0/
On this link, a simple version of one of Kevin's circuits are presented. How does this differ from e.g. Dana's VVR? If Dana (or anyone else) could shed some light on this, that'd be awesome.
Kind regards, Jake
VVR, Power Scaling, DIY-methods - how do they differ?
Moderators: pompeiisneaks, Colossal
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Hi Jake,
One quick comment about the link posted, it is a simple design with no provision for current clamping besides the 20 ohm 5W r to protect the mosfet. I don't think it is KOC's as it uses the dual ganged pot.
I have not studied the VVR as I have purchased KOC kits and books in the past. A general statement, that may have changed, is that the KOC kits have more more regulators allowing more nodes to be scaled than the others if this is something that is desired / needed. The more expensive KOC kits are also flexible allowing one to make "on the fly" changes, for example have different PS levels w/ different channels etc., have instant "solo" headroom or use an expression pedal etc.
It seems that both KOC PS kits and Dana's VVR are very popular giving testament to their effectiveness and need. Truly, something we as end users and builders should appreciate.
Hope this helps.
John
One quick comment about the link posted, it is a simple design with no provision for current clamping besides the 20 ohm 5W r to protect the mosfet. I don't think it is KOC's as it uses the dual ganged pot.
I have not studied the VVR as I have purchased KOC kits and books in the past. A general statement, that may have changed, is that the KOC kits have more more regulators allowing more nodes to be scaled than the others if this is something that is desired / needed. The more expensive KOC kits are also flexible allowing one to make "on the fly" changes, for example have different PS levels w/ different channels etc., have instant "solo" headroom or use an expression pedal etc.
It seems that both KOC PS kits and Dana's VVR are very popular giving testament to their effectiveness and need. Truly, something we as end users and builders should appreciate.
Hope this helps.
John
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Hi John,
Thanks for your reply, much appreciated! What I'm trying to do, is get my head around this. I'm the kinda guy who can't wait to get a piece of gear, to open it up and learn from how other people do stuff. Destroyed a lot of things as a kid that way
I see your point. The design posted on that page does have a dual-pot, as it's also used to control the bias. I sadly haven't got KOC's books anymore, so I can't check it with the stuff he proposed. I'm amazed as the London Power-kits and their flexability, but this is just for my own needs and as a student I'm broke enough as it is!
Dana's VVR is, as you say, very popular, so I'm really hoping he chimes in!
Kind regards, Jake
Thanks for your reply, much appreciated! What I'm trying to do, is get my head around this. I'm the kinda guy who can't wait to get a piece of gear, to open it up and learn from how other people do stuff. Destroyed a lot of things as a kid that way
I see your point. The design posted on that page does have a dual-pot, as it's also used to control the bias. I sadly haven't got KOC's books anymore, so I can't check it with the stuff he proposed. I'm amazed as the London Power-kits and their flexability, but this is just for my own needs and as a student I'm broke enough as it is!
Dana's VVR is, as you say, very popular, so I'm really hoping he chimes in!
Kind regards, Jake
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Another thing I've been wondering about is, regarding that pot and the pot in the KOC stuff that I remember is implemented in a way somewhat similar to that, which kind of pot they use. The Alpha-stuff commonly available isn't rated for 400-500Volts as far as I know!
Anyone got a suggestion for this?
Kind regards, Jake
Anyone got a suggestion for this?
Kind regards, Jake
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Jake,
The PEC 2 watt "military" pots are what I have used.
John
The PEC 2 watt "military" pots are what I have used.
John
Re: VVR, Power Scaling, DIY-methods - how do they differ?
I don't have a clue what KOC is using. I have never read any of his books or installed any of his circuits so I really am at a loss to comment on how they differ circuit wise. My goal was to come up with a inexpensive way to make the B+ Variable in my own amps and that is exactly what my circuit does. I also haven't tried the circuit in the link but it looks like it would probably work. I am not so sure I like a couple of his value choices and I'm also not crazy about circuits that are posted annomously on the internet.
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Hi Dana,
Thanks for your response. I am not accusing any party of ripping another party off. That being said, I don't think there's anything wrong with learning from smart minds. That's what our society is all about anyways.
So for the sake of discussion, can you tell me how and what you would do it differently?
I'm not much for blindly implementing "anonymous internet-ideas" in my expensive amplifiers, so I demoed the circuit first, using it as a dimmer for a light-bulb, and it worked pretty much right off the bat, with bias-regulation and all. However, I'm very interested in learning how I can make it better in terms of reliability. I can't afford KOC's books right now, so I'll have to wait for a kind gift from my parents for my birtshday in the end of june.
Any help is of course very appreciated!
Kind regards, Jake
Thanks for your response. I am not accusing any party of ripping another party off. That being said, I don't think there's anything wrong with learning from smart minds. That's what our society is all about anyways.
So for the sake of discussion, can you tell me how and what you would do it differently?
I'm not much for blindly implementing "anonymous internet-ideas" in my expensive amplifiers, so I demoed the circuit first, using it as a dimmer for a light-bulb, and it worked pretty much right off the bat, with bias-regulation and all. However, I'm very interested in learning how I can make it better in terms of reliability. I can't afford KOC's books right now, so I'll have to wait for a kind gift from my parents for my birtshday in the end of june.
Any help is of course very appreciated!
Kind regards, Jake
PS vs VVR
Jake,
I have built amps with both. I prefer Dana's VVR. Here's why:
1. Cost: Much less money than PS
2. Simplicity: Much simpler to build and far fewer components.
3. Space: VVR takes up much less space. This is especially important when retrofitting.
4. Sound: This is subjective, of course, but I believe the VVR is more transparent. The PS circuit tends to suck the warmth out of the amp the lower you go. At 75% power and up they're about equal in terms of transparency.
Troubleshooting: Because Trainwrecks (especially the Express) is such a touchy circuit I found it much more difficult to tame with the addition of the PS circuit vs the VVR circuit. Again that goes back to simplicity.
If you're gonna simply scale the whole amp. I highly recommend the VVR.
The ONLY caveat (currently) is that the VVR is limited to <50W amps... until someone here goes down that road, at least, and tries paralleling the mosfets. As I recall the PS circuit is not limited.
I have also read all of the TUT series of books. Great books! I have applied a lot of his recommendations into amps that I've built. I've also built amps that didn't adhere to many of Kevin's 'rules' and they were dead quiet and sounded fantastic. (such as using can caps. He recommends not using them due to the ground loop they create) I have not done a head to head, but I can't hear the difference. I use KOC's books as a best practices guide. He would probably be the first to admit that if you can repeatedly build an amp that's dead quiet, sounds great, and can stand up to road abuse then who cares how it's wired inside or what components you used.
I hope this helps with your decision.
My $0.02.
Sincerely,
Steve
I have built amps with both. I prefer Dana's VVR. Here's why:
1. Cost: Much less money than PS
2. Simplicity: Much simpler to build and far fewer components.
3. Space: VVR takes up much less space. This is especially important when retrofitting.
4. Sound: This is subjective, of course, but I believe the VVR is more transparent. The PS circuit tends to suck the warmth out of the amp the lower you go. At 75% power and up they're about equal in terms of transparency.
Troubleshooting: Because Trainwrecks (especially the Express) is such a touchy circuit I found it much more difficult to tame with the addition of the PS circuit vs the VVR circuit. Again that goes back to simplicity.
If you're gonna simply scale the whole amp. I highly recommend the VVR.
The ONLY caveat (currently) is that the VVR is limited to <50W amps... until someone here goes down that road, at least, and tries paralleling the mosfets. As I recall the PS circuit is not limited.
I have also read all of the TUT series of books. Great books! I have applied a lot of his recommendations into amps that I've built. I've also built amps that didn't adhere to many of Kevin's 'rules' and they were dead quiet and sounded fantastic. (such as using can caps. He recommends not using them due to the ground loop they create) I have not done a head to head, but I can't hear the difference. I use KOC's books as a best practices guide. He would probably be the first to admit that if you can repeatedly build an amp that's dead quiet, sounds great, and can stand up to road abuse then who cares how it's wired inside or what components you used.
I hope this helps with your decision.
My $0.02.
Sincerely,
Steve
Re: VVR, Power Scaling, DIY-methods - how do they differ?
I am interested in this as well.
I have a simple 2 x 6v6 amp I just recently finished and after trying a couple master volume circuits in it I'm not quite satisfied with the results so far.
My amp is cathode biased so apparently the top circuit would be the one to try.
So Jake, you built the circuit you posted?
I have a simple 2 x 6v6 amp I just recently finished and after trying a couple master volume circuits in it I'm not quite satisfied with the results so far.
My amp is cathode biased so apparently the top circuit would be the one to try.
So Jake, you built the circuit you posted?
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Hi Steve,
That too was my thoughts towards the KOC-systems. His books are, as you say, an excellent collection of personal thoughts and oppinions of a knowledgeble person, but of course not the only truth out there
From what I've seen of the VVR, it should be kinda similar in operation to the circuit that I've posted. But of course, when I've got a bit of money, I'd like to check out Dana's version. I too am for either scaling the whole amp, or just the power section - the KOC stuff get's a bit too complicated for my tastes, and when it comes to the preamp, it still is the easiest place to tailor without having to dissapate a vast amount of energy.
@ Structo:
I've only built it for testing purposes. I've been using a fixed circuit similar to this one for a couple of years, to help lower the voltage in the screen grids in my buddies Marshalls, as Marshall puts 470-490 Volts there, without regards to the datasheet specifying 425 Volts as a maximum.
For your cathode bias'ed amp, it should be pretty straight foward. As far as I can see, the only thing that can go wrong is the MOSFET burning out, leaving you with 0 Volts on the B+ supply.
Kind regards, Jake
That too was my thoughts towards the KOC-systems. His books are, as you say, an excellent collection of personal thoughts and oppinions of a knowledgeble person, but of course not the only truth out there
From what I've seen of the VVR, it should be kinda similar in operation to the circuit that I've posted. But of course, when I've got a bit of money, I'd like to check out Dana's version. I too am for either scaling the whole amp, or just the power section - the KOC stuff get's a bit too complicated for my tastes, and when it comes to the preamp, it still is the easiest place to tailor without having to dissapate a vast amount of energy.
@ Structo:
I've only built it for testing purposes. I've been using a fixed circuit similar to this one for a couple of years, to help lower the voltage in the screen grids in my buddies Marshalls, as Marshall puts 470-490 Volts there, without regards to the datasheet specifying 425 Volts as a maximum.
For your cathode bias'ed amp, it should be pretty straight foward. As far as I can see, the only thing that can go wrong is the MOSFET burning out, leaving you with 0 Volts on the B+ supply.
Kind regards, Jake
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Gents,
I would speculate the greatest difference in tone from the various circuits mentioned is from the implementation of one to the whole amp vs the power tubes only, not the design or designer.
As we all know, the use of master volumes to limit the drive to the power tubes WILL change the tone. By scaling the whole amp, the drive level is more of an "automatic" limiting. Like everything, there is usually more than one way to do things. Seems that life, and amp building, is a comprimise of things.
John
I would speculate the greatest difference in tone from the various circuits mentioned is from the implementation of one to the whole amp vs the power tubes only, not the design or designer.
As we all know, the use of master volumes to limit the drive to the power tubes WILL change the tone. By scaling the whole amp, the drive level is more of an "automatic" limiting. Like everything, there is usually more than one way to do things. Seems that life, and amp building, is a comprimise of things.
John
Re: VVR, Power Scaling, DIY-methods - how do they differ?
I have done some amps with cathode biased VVR and some with fixed bias version based on Danas constructions. I scaled my whole Plexi Lead (50W) and I am not very happy with it soundwise. In near future I am going to scale only power tubes of it despite I am not going to put any PPIMV to it. PPIMV is needed if you want to drive preamp very hard and scale poweramp to bedroom level. At the moment VVR solution works technically flawlessly but I do not like my Plexi`s distorted sound. When scaling whole amp, it kills all dynamics and three dimensional sound of the amp. All in all I think that VVR or PS is the best alternative to traditional MV:s not altering amp basic sound too much. Big hand to Dana of his work when developing cost efficient VVR solutions for us in this tube amp building community. HarryRe: VVR, Power Scaling, DIY-methods - how do they differ?
Thanks John and Harry for your posts.
Harry, I don't think that PS can give you the Plexi crunch at bedroom level. Just like with a dummy load, a bit reduction works fine, but clamping 50W down to 1W will kill the sound. And why? Because our ears aren't linear, because the speakers aren't linear, and the way the amp operates at such distortion, neither is it!
Kind regards, Jake
Harry, I don't think that PS can give you the Plexi crunch at bedroom level. Just like with a dummy load, a bit reduction works fine, but clamping 50W down to 1W will kill the sound. And why? Because our ears aren't linear, because the speakers aren't linear, and the way the amp operates at such distortion, neither is it!
Kind regards, Jake
Re: VVR, Power Scaling, DIY-methods - how do they differ?
Jake!I fully agree with you in this matter of bedroom level issues. I do not use my plexi at home, but use it for lead playing with my band. I put VVR in it to tame some of that infernal noise level. I know that famous plexi sound is based mainly on PI and poweramp distortion. I am just building one 1987 Plexi Lead to one guy. I will scale only powerstage with it. When it is ready, it is easier to compare which scaling method is better for that amp. I think that any amp with bedroom level sounds completely different compared to an amp played in band playing level. BTW if you want to look and listen my amps also plexi, go here www.bluetone.fi Harry
Re: VVR, Power Scaling, DIY-methods - how do they differ?
well, of course when you drop a 50W or 100W amp down to "bedroom" levels, it ain't gonna sound the same, or more importantly, feel the same. I think there is a threshold, below which, you are not going to get "good" results, or at least, not AS good. Remember, volume effects bass response. The more volume, the louder the bass will be. Also, you won't get the "wind in your face" feel of having a huge stack giving you all it has got.
Question to those who have done the VVR approach and dropped the voltage on the whole amp, as opposed to just the power tubes, how has this come out for you with a 50W D***** style amp? Liked it, hated it? I have been wondering how dropping the voltages on the preamps would effect the tone.
Question to those who have done the VVR approach and dropped the voltage on the whole amp, as opposed to just the power tubes, how has this come out for you with a 50W D***** style amp? Liked it, hated it? I have been wondering how dropping the voltages on the preamps would effect the tone.