WHY ME???
Hi,
John,
LOL.
Tony,
Personally,I'd like to hear from Brett what it is he finds so seductive in the Genalex (GEC USA) design.
Has he heard it before and so on...
Also,I received the circuit diagram of the (heavily) modded Quicksilver KT88 amps and found it needlessly complicated.
I am rather familiar with the Quicksilver 8417 amp and like the elegance of the driver and splitter design.
It also sounds great and is a promising amp provided we find OPTs that can live up to the expectations.
It can be improved upon quite easily and more importantly it is a very good start for any newcomer to DIY tubebuilding.
Just my opinion of course but at least I have heard it before,loved it and to top it all off other people seem to share my enthusiasm about it.
Cheers,
Hi,
John,
LOL.
Tony,
Personally,I'd like to hear from Brett what it is he finds so seductive in the Genalex (GEC USA) design.
Has he heard it before and so on...
Also,I received the circuit diagram of the (heavily) modded Quicksilver KT88 amps and found it needlessly complicated.
I am rather familiar with the Quicksilver 8417 amp and like the elegance of the driver and splitter design.
It also sounds great and is a promising amp provided we find OPTs that can live up to the expectations.
It can be improved upon quite easily and more importantly it is a very good start for any newcomer to DIY tubebuilding.
Just my opinion of course but at least I have heard it before,loved it and to top it all off other people seem to share my enthusiasm about it.
Cheers,
Elaboration
I feel a trap but here goes...
Well, the output devices are high impedance.
We want them to drive a low impedance with (some) damping factor.
What can we do? The only solution is copious amounts of negative feedback
What does this do? It drives these high impedance devices harder and harder until they eventually deliver enough current into the load.
It just aint natural
My feeling is that OTL done well might sound very similar SS, and done badly will sound like
In all seriousness, as mentioned in one of my earliest posts, I have doubts about the distortion spectrum produced with this topology, especially when working hard. I'm sure it's unique - but unsure if it's pleasant.
I feel a trap
but here goes...Well, the output devices are high impedance.
We want them to drive a low impedance with (some) damping factor.
What can we do? The only solution is copious amounts of negative feedback
What does this do? It drives these high impedance devices harder and harder until they eventually deliver enough current into the load.It just aint natural
My feeling is that OTL done well might sound very similar SS, and done badly will sound like
In all seriousness, as mentioned in one of my earliest posts, I have doubts about the distortion spectrum produced with this topology, especially when working hard. I'm sure it's unique - but unsure if it's pleasant.
I LOVE "BOOBY" TRAPS.
Hi,
We're drifting but here goes:
Example of a very common tube as used in OTL amp:
6080/6AS7G Ri=280R/plate.
//sections > 140R
Take ten in // =14R
Apply NFB (from speaker to cathode of 1st stage) > Zo =0.014R depending on NFB.
Take the same valve and hook it up in a typical OTL arrangement
i.e floating between B+ and B-,plot the valve and bingo:nothing but straight vertical lines.
The trick is you need to keep them there.
Now try to regulate these and you will soon understand you''ll need an extra couple of valves to get there.
Never said it was easy....once you hear a good one though,you're hooked for life.
A lot of SS gear uses the same topology but I still have to hear one sounding as open,dynamic,transparant as an OTL though.
They sound like no amp at all,they follow the source.
No,the only big risk with very low impedance valves is that they can start to act as diodes and get into thermal runaway.
I've seen that with the 6C33C but never on a 6080.
I've abused my OTLs in ways a transistor amp would have gone belly up at once.
Can you imagine driving loads where you actually see the binding posts (in my case these big WBTs) go cherry red and the amp still singing?
No,I didn't run that situation for hours and I'm not saying they're the perfect amp for any speaker either.
Is there any valve amp out there that can deliver more current than an OTL?
Don't think so.
\rant
Cheers,
Hi,
We're drifting but here goes:
Example of a very common tube as used in OTL amp:
6080/6AS7G Ri=280R/plate.
//sections > 140R
Take ten in // =14R
Apply NFB (from speaker to cathode of 1st stage) > Zo =0.014R depending on NFB.
Take the same valve and hook it up in a typical OTL arrangement
i.e floating between B+ and B-,plot the valve and bingo:nothing but straight vertical lines.
The trick is you need to keep them there.
Now try to regulate these and you will soon understand you''ll need an extra couple of valves to get there.
Never said it was easy....once you hear a good one though,you're hooked for life.
A lot of SS gear uses the same topology but I still have to hear one sounding as open,dynamic,transparant as an OTL though.
They sound like no amp at all,they follow the source.
No,the only big risk with very low impedance valves is that they can start to act as diodes and get into thermal runaway.
I've seen that with the 6C33C but never on a 6080.
I've abused my OTLs in ways a transistor amp would have gone belly up at once.
Can you imagine driving loads where you actually see the binding posts (in my case these big WBTs) go cherry red and the amp still singing?
No,I didn't run that situation for hours and I'm not saying they're the perfect amp for any speaker either.
Is there any valve amp out there that can deliver more current than an OTL?
Don't think so.
\rant
Cheers,
OTL
Let's put this another way...
Many of us on the Tubes Forum, like tubes because they are close to linear before the (optional)application of NFB.
I feel that this is probably the main thing that makes them better than SS.
Therefore why run them in a non-linear mode (before feedback is applied), making them behave little different to a high impedance FET?
I don't doubt that good results are obtainable with careful design. It's whether it's the best use of effort.
Of course what I need is to do it myself and see....
BTW I'm still thinking about your maths.
Let's put this another way...
Many of us on the Tubes Forum, like tubes because they are close to linear before the (optional)application of NFB.
I feel that this is probably the main thing that makes them better than SS.
Therefore why run them in a non-linear mode (before feedback is applied), making them behave little different to a high impedance FET?
I don't doubt that good results are obtainable with careful design. It's whether it's the best use of effort.
Of course what I need is to do it myself and see....
BTW I'm still thinking about your maths.
INCLUDING ME
Hi,
The circuit is linear as is.
NFB is used to:
a) reduce Zo
b)correct speaker and control speaker behaviour,it has the added advantages to act where it is most useful.
I got carried away it seems: Zo of 0.14R is more like it.
More than adequate I think?
Unless your speakers are uncommon,why not?
Cheers,
Hi,
The circuit is linear as is.
NFB is used to:
a) reduce Zo
b)correct speaker and control speaker behaviour,it has the added advantages to act where it is most useful.
I got carried away it seems: Zo of 0.14R is more like it.
More than adequate I think?
Unless your speakers are uncommon,why not?
Cheers,
Re: DIY 60W
Wow, how about starting simple?
I suggest something modest like a PP EL84. Or even an SE 300B.
60 Watts? My speakers are only 89db sensitive and as I sit typing this I'm enjoying music through a 71A amp that produces all of 1/2 watt peak! Mind you, this isn't always enough, but the 8 watts from a 300B is plenty in my small room.
Anyway, if it isn't enough power, it'll be an excuse to build another amp. If it's your first project, start small. You don't want to be learning how to solder and do metalwork and how to layout components on your ultimate amplifier.
What's most important is that you learn a bit before you build. There are lots of resources available on the web. I didn't read everything in the thread up to now, but I didn't notice anything regarding your level of electronics knowledge. Don't start buying parts until you know at least the basics of electronics!!! If you aren't interested in learning about this stuff, build a kit!!!
Here's an excellent series on tube amps, but you need the basic electronics knowledge first if you haven't already got it:
http://www.audioxpress.com/resource/audioclass/
TStrong_06 said:
Wow, how about starting simple?
I suggest something modest like a PP EL84. Or even an SE 300B.
60 Watts? My speakers are only 89db sensitive and as I sit typing this I'm enjoying music through a 71A amp that produces all of 1/2 watt peak! Mind you, this isn't always enough, but the 8 watts from a 300B is plenty in my small room.
Anyway, if it isn't enough power, it'll be an excuse to build another amp. If it's your first project, start small. You don't want to be learning how to solder and do metalwork and how to layout components on your ultimate amplifier.
What's most important is that you learn a bit before you build. There are lots of resources available on the web. I didn't read everything in the thread up to now, but I didn't notice anything regarding your level of electronics knowledge. Don't start buying parts until you know at least the basics of electronics!!! If you aren't interested in learning about this stuff, build a kit!!!
Here's an excellent series on tube amps, but you need the basic electronics knowledge first if you haven't already got it:
http://www.audioxpress.com/resource/audioclass/
DIY 60W
Jeff: Thanks for your input as well...Gee, I thought that a 60W amp was entry level!! As I only have the Wharfedales and they have a sensitivity of only about 86dB/W, I need something thats going to make them sing (well, as much as they can, I guess). I don't have the moolah right now for new speakers, (preferably another set of B&W CDM1SE's), I will have to make do. I've heard of good things coming from the 300B, but will that work for me (I have a medium size listening area, with lots of 'soft items' such as area rugs, funiture, and drapes and such? Would your suggestion of a P-P EL84 set or SE 300B do the trick?
BTW, I do have some electronics background. Not entirely a novice. But not an electrical engineer either. on a scale of 1 to 10, I would say I'm a 3 or so. I am reading up on electric circuits now, and looking at my girlfriends, college-level circuits book. (She's the engineer out of the bunch...I was a lowly econometrics major )
fdegrove: Now, as Output Transformerless amps go, arent they somewhat finicky. I understand that most tube amps use output transformers to match impedance with the speaker load. Is this an important consideration at my level?
I am learning alot just by asking and reading what you cats post!
Regards
Jeff: Thanks for your input as well...Gee, I thought that a 60W amp was entry level!!
As I only have the Wharfedales and they have a sensitivity of only about 86dB/W, I need something thats going to make them sing (well, as much as they can, I guess). I don't have the moolah right now for new speakers, (preferably another set of B&W CDM1SE's), I will have to make do. I've heard of good things coming from the 300B, but will that work for me (I have a medium size listening area, with lots of 'soft items' such as area rugs, funiture, and drapes and such? Would your suggestion of a P-P EL84 set or SE 300B do the trick?BTW, I do have some electronics background. Not entirely a novice. But not an electrical engineer either.
on a scale of 1 to 10, I would say I'm a 3 or so. I am reading up on electric circuits now, and looking at my girlfriends, college-level circuits book. (She's the engineer out of the bunch...I was a lowly econometrics major )fdegrove: Now, as Output Transformerless amps go, arent they somewhat finicky. I understand that most tube amps use output transformers to match impedance with the speaker load. Is this an important consideration at my level?
I am learning alot just by asking and reading what you cats post!
Regards
F knows of what he talks but I agree with above. Start with something simple if you have not soldered and layed out audio circuits. It is just difficult enough that generally (you might be hte exception of course) you cannot expect to do your "pet" project first off.
Give yourself a little practice. Something like this: http://www.dogstar.dantimax.dk/tubestuf/miniblok.htm
Something really cheap. Fred's piece is worth reading if you don't make it and are starting out just for the discussion of the circuit.
T, did you get my email of online tube info/articles? Those articles and many more like them were there. I'll send it one more try if you want.
Cheers Craig Ryder
TRIODE SET
Hi,
It seems I've seen that circuit before,GA AA SP?
Actually I agree with you Craig,thanks to Freds' explanations and showing the loadlines it will be an interesting starting point for any beginning tube-o-phile.
Even if Tony can't drive his LS with it,it would still make a very good headphone amp and an experience to learn from.
Cheers,
Hi,
It seems I've seen that circuit before,GA AA SP?
Actually I agree with you Craig,thanks to Freds' explanations and showing the loadlines it will be an interesting starting point for any beginning tube-o-phile.
Even if Tony can't drive his LS with it,it would still make a very good headphone amp and an experience to learn from.
Cheers,
Just thought I'd throw my vote in for starting simple as well. I think you would be surprised at how loud a small amplifier will sound on your speakers. I have a ~6watt PP el84 amplifier (They are being run as triodes) that I helped my brother build as his first project. The amplifier started out as a dynaco sca35 and has evolved a long way since then. I have to say that I think this is a great way to start. Unless you love working with metal, this gives you the chance to start with a decent sounding amplifier that already works. The metal work and chassis layout are done for you, but you can easily modify the circuit inside the case. This way you can focus on learning about one section of the amplifier at a time. For example you could start by building a new driver stage for the amplifier. Next maybe you would build a better power supply, etc. etc.
In my example I rebuilt the power supply, removed the tone controls and switched the driver tubes to 12ax7's. Since then I have helped him switch to 6n1p's as driver tubes and added a constant current souce to the first stage. The next plan is to try using a interstage transformer for phase splitting, and shunt regulate the driver tubes (probably just using the extra half of the 6n1p). After that he is planning to completely rebuild the amp in a new chassis with a larger power supply (running out of space in the original box ).
Anyways my point being that with this route you can get started right away with an amp that doesn't cost a fortune (sca35's can be purchase for a little over $100 on ebay), experiment with designs you've seen (at least within the realm of PP el84) and learn for yourself what sounds good and what doesn't. Then after you learn about what you are doing and know what you like you can sit down and build something from scratch.
As a note, my current speakers are 87db, and 6 watts is plenty when I listen to his amp. I keep intending to sit down and build a pair of high efficieny speakers, but I always have too many electronics projects that sound like more fun...
In my example I rebuilt the power supply, removed the tone controls and switched the driver tubes to 12ax7's. Since then I have helped him switch to 6n1p's as driver tubes and added a constant current souce to the first stage. The next plan is to try using a interstage transformer for phase splitting, and shunt regulate the driver tubes (probably just using the extra half of the 6n1p). After that he is planning to completely rebuild the amp in a new chassis with a larger power supply (running out of space in the original box
). Anyways my point being that with this route you can get started right away with an amp that doesn't cost a fortune (sca35's can be purchase for a little over $100 on ebay), experiment with designs you've seen (at least within the realm of PP el84) and learn for yourself what sounds good and what doesn't. Then after you learn about what you are doing and know what you like you can sit down and build something from scratch.
As a note, my current speakers are 87db, and 6 watts is plenty when I listen to his amp. I keep intending to sit down and build a pair of high efficieny speakers, but I always have too many electronics projects that sound like more fun...
DIY 60W
Craig:
I did receive it, though, I have had some problem opening it...Please send it once again...Thanks!
dcole:
thanks for your input as well. Those 6Wers do a good job of driving your loudspeakers? interesting...I kinda want the WHOLE experience, from start to finish of doing a new amp...But your route seems to be very expedient and it seems I would learn a lot from it as well.
dhaen:
I cant wait to get started! I want to grow out of my first project as quickly as possible!!!. Truthfully, I would love to start doing a LS-driver. I don't even own a set of real listening headphones.
My next big ambition (after a while, that is) is a tube/SS hybrid or straight SS amp to run my DJing gig! Something around 300-400WPC will do the trick!
fdegrove:
OK, I will wait to tackle the OTL stuff til after my first try...Funny you should mention Xformers. The thing I remember most from High School Physics was 'turns ratios' in transformers, and secondary windings and such. So I think that I have a reasonably good start, but I am definitely in need of more...
Regards,
Tony
Craig:
I did receive it, though, I have had some problem opening it...Please send it once again...Thanks!
dcole:
thanks for your input as well. Those 6Wers do a good job of driving your loudspeakers? interesting...I kinda want the WHOLE experience, from start to finish of doing a new amp...But your route seems to be very expedient and it seems I would learn a lot from it as well.
dhaen:
I cant wait to get started! I want to grow out of my first project as quickly as possible!!!
. Truthfully, I would love to start doing a LS-driver. I don't even own a set of real listening headphones. My next big ambition (after a while, that is) is a tube/SS hybrid or straight SS amp to run my DJing gig! Something around 300-400WPC will do the trick!
fdegrove:
OK, I will wait to tackle the OTL stuff til after my first try...Funny you should mention Xformers. The thing I remember most from High School Physics was 'turns ratios' in transformers, and secondary windings and such. So I think that I have a reasonably good start, but I am definitely in need of more...
Regards,
Tony
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