nikongod
DIY-ku
- Joined
- Jan 24, 2005
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cobaltmute:
Thanks for telling me how to do that: Its been ages since I have read HTML code, but I guess its time to relearn that.
Quote:
This last bit is the problem.
Dont worry about the tubes. What you need to worry about to design a (at least half) decent amp of ANY kind is exactly what you dont know, thats OK, admitting you dont know it is how you go out and learn it.
Before you think about more schematics & topologies and whatnot you need to go out and figure out what it is you are trying to accomplish. That is the key. Are you trying to put 100v into a 300ohm load? Are you trying to put 2a into 32ohms? Do you want an output impedance less than 0.0001ohms? what *EXACTLY* are you trying to do? For sure you could design an amp that would accomplish these feats, but do you have any real need for that beyond mental masturbation and bragging rights?
The really good news is you probably have most of what you need to figure this out. the DV337 should be able to drive a sennheiser to dumb volumes. Measure the ac voltage that it takes (its much much better if your meter will accurately display less than 2vac). If your meter has AC current, do that to or just crunch the numbers. Test it out on a grado too. learn for yourself exactly what it takes to drive these headphones. people love to spout rules about how to drive a senn, How many people are just parrots repeating unconditional rules they dont understand?
Perhaps even more telling, and where many people stray (IMO) is what it takes to drive these headphones to your own listening levels (for this you will almost certainly need a meter that displays less than 2vac with good precision). Does it matter that someone else's amp can put 20v into 300ohms when you only use 0.25v? I would say hardly so, what matters is that YOUR amp sounds nice at realistic volumes. does this necessarily mean that an amp that only puts out 2.5v (0.25v+20db headroom) WILL sound better? not at all, but the odds are stacked in your favor.
Now would be as good of a time as any to figure out what output impedance you need. Guess what, its not going to be zero with tube output stages. If you need that (and maybe you do, although I have not found that to be the case) have fun with SS stuff & hybrids. Again figure out what you NEED. The DV amps have kind of high output impedances for testing, so build a cmoy with a 500ohm pot on the output to adjust output impedance. Try a bunch of things out with a bunch of headphones.
So far you have spent the cost of building a cmoy plus a cheap 500ohm pot (and a meter that can display less than 2vac, if you dont have that) and learned a bunch.
Quote:
Dont worry about the tubes. Worry about what you need out of the amp.
After you have figured out what you need out of the amp you can work the rest backwards from the output. You will probably be surprised how well things fall into place.
Quote:
The amps are totally different, even with the same tubes the amps would sound and work differently. By not using a cathode follower (unless you really want to use a Mu follower, in which case you owe it to yourself to listen to a few mu follower amps to help you change your mind) you have already changed the sound of the amp a great deal. Pentodes make great CCS's, why not use one? There are a couple disadvantages in a parafeed amp: you need higher voltage rails than with a SS CCS and you need a second heater supply.
Thanks for telling me how to do that: Its been ages since I have read HTML code, but I guess its time to relearn that.
Quote:
Unfortunately, right now all I can do is calculator math gymnastics. I don't have the money yet for parts or testing equipment (I plan to get a cheap oscilloscope and signal generator even though I know that they TECHNICALLY aren't essential pieces of equipment) yet. It wont be until mid next month that I will have the money to start going in at this. So in the mean time it's calculate away while trying to grasp better the nuance of tube amp design. At this point, my weakest areas of knowledge are at the "ends", meaning input and output considerations and calculations, and tube selection itself.
This last bit is the problem.
Dont worry about the tubes. What you need to worry about to design a (at least half) decent amp of ANY kind is exactly what you dont know, thats OK, admitting you dont know it is how you go out and learn it.
Before you think about more schematics & topologies and whatnot you need to go out and figure out what it is you are trying to accomplish. That is the key. Are you trying to put 100v into a 300ohm load? Are you trying to put 2a into 32ohms? Do you want an output impedance less than 0.0001ohms? what *EXACTLY* are you trying to do? For sure you could design an amp that would accomplish these feats, but do you have any real need for that beyond mental masturbation and bragging rights?
The really good news is you probably have most of what you need to figure this out. the DV337 should be able to drive a sennheiser to dumb volumes. Measure the ac voltage that it takes (its much much better if your meter will accurately display less than 2vac). If your meter has AC current, do that to or just crunch the numbers. Test it out on a grado too. learn for yourself exactly what it takes to drive these headphones. people love to spout rules about how to drive a senn, How many people are just parrots repeating unconditional rules they dont understand?
Perhaps even more telling, and where many people stray (IMO) is what it takes to drive these headphones to your own listening levels (for this you will almost certainly need a meter that displays less than 2vac with good precision). Does it matter that someone else's amp can put 20v into 300ohms when you only use 0.25v? I would say hardly so, what matters is that YOUR amp sounds nice at realistic volumes. does this necessarily mean that an amp that only puts out 2.5v (0.25v+20db headroom) WILL sound better? not at all, but the odds are stacked in your favor.
Now would be as good of a time as any to figure out what output impedance you need. Guess what, its not going to be zero with tube output stages. If you need that (and maybe you do, although I have not found that to be the case) have fun with SS stuff & hybrids. Again figure out what you NEED. The DV amps have kind of high output impedances for testing, so build a cmoy with a 500ohm pot on the output to adjust output impedance. Try a bunch of things out with a bunch of headphones.
So far you have spent the cost of building a cmoy plus a cheap 500ohm pot (and a meter that can display less than 2vac, if you dont have that) and learned a bunch.
Quote:
I found a GREAT resource on //feed but how that interrelates with the design of the tube stage and accompanying passive elements I have seen little. When it comes to tube selection, I just don't know that many yet. There are soooo many so having an idea of what tubes offer the gain I am looking for along with the Vg I am looking for, along with the Iq I am looking for, and the grid/V swing I am looking for (if I go pentode top) is more just google searches for "low-mu medium grid" and/or luck of the draw. Not the most expedient of means to find such things but also pretty interesting in its own right.
Dont worry about the tubes. Worry about what you need out of the amp.
After you have figured out what you need out of the amp you can work the rest backwards from the output. You will probably be surprised how well things fall into place.
Quote:
When it comes to using a pentode as the top tube, there are 2 things: finding a tube that has the same Iq as the lower triode (haven't looked too far into this so this may prove to be a non issue), and my 337 already has a pentode in it so I was hoping to go all triode and see how different it would sound =D
The amps are totally different, even with the same tubes the amps would sound and work differently. By not using a cathode follower (unless you really want to use a Mu follower, in which case you owe it to yourself to listen to a few mu follower amps to help you change your mind) you have already changed the sound of the amp a great deal. Pentodes make great CCS's, why not use one? There are a couple disadvantages in a parafeed amp: you need higher voltage rails than with a SS CCS and you need a second heater supply.