6u10 or 6ac10 triple triodes, 6jn6 or 6jm6 or 6gv5 outputs, 12 pin compactrons brew your own.....
You can download PCB design program from Express PCB and print on hi gloss paper to etch your own PCB's.
Just giving you ideas on possible directions, tools, associated costs. There are many ways to design and fab an amp, have fun!!!!!!!!
You can download PCB design program from Express PCB and print on hi gloss paper to etch your own PCB's.
Just giving you ideas on possible directions, tools, associated costs. There are many ways to design and fab an amp, have fun!!!!!!!!
Ezra,
I really think you're putting the cart before the horse by deciding on preamp tubes before you've decided on a topology or calculated your requirements. I like your choice to use compactrons. Why not? But it will probably take you longer because there is less experience available to draw upon from folks and far fewer examples to learn from.
How are you going to wire up those triple triodes? Which circuit? It will become more obvious which tubes will work once you know that.
..Todd
I really think you're putting the cart before the horse by deciding on preamp tubes before you've decided on a topology or calculated your requirements. I like your choice to use compactrons. Why not? But it will probably take you longer because there is less experience available to draw upon from folks and far fewer examples to learn from.
How are you going to wire up those triple triodes? Which circuit? It will become more obvious which tubes will work once you know that.
..Todd
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I've been actually arguing with myself how to meet all of my requirements, and decided on a topology for the whole thing, opinions welcomed and encouraged:
for 1 channel:
I've been basically going on Frank's tube datasheet pages and looking for "ttt" and "pt" tubes and have a few possible candidates.
Ezra
for 1 channel:
- a triple triode compactron for the preamp. I'm curious to see what 3 triodes in parallel sound like, but I'm planning on adding switches to go from series to parallel between each stage.
- a pair of triode+pentode compactrons operating in push pull and wired for ultralinear mode. Expected output transformer is something of this kind:EDCOR Electronics Corporation. CXPP21-MS-8.6K
- Solid state rectified power section, with probably an Edcor transformer there too.
I've been basically going on Frank's tube datasheet pages and looking for "ttt" and "pt" tubes and have a few possible candidates.
Ezra
Wiring three triodes in series or parallel, to see what that sounds like, doesn't make much sense to me. And switching between the two makes even less sense.
I could be wrong since I'm not a tube amp rocket scientist, but it sounds to me like you need to read up on the very basics of tube amplifier circuits and learn how the circuits work to amplify audio.
..Todd
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Another option on the cheap could be the old 6n1p / el84 PP...
Many variations exist from:
-purely resistor loaded and biased
-CCS plate loading for the 6n1p
-LED cathode biasing for the 6n1p
-resistor cathode biasing for the el84's
-CCS cathode biasing for the el84's
-I think there are even some LED cathode biasing for the el84's out there - "Red light district" amp...
Iron for this am would be cheap as well as tubes...lots of new and NOS out there for reasonable prices...complete amp for <$350 most likely and a rockin little PP amp to boot...I have one that is simply CCS cathode biased el84 stage...looking to LED bias the front end someday...
Good info here
Many variations exist from:
-purely resistor loaded and biased
-CCS plate loading for the 6n1p
-LED cathode biasing for the 6n1p
-resistor cathode biasing for the el84's
-CCS cathode biasing for the el84's
-I think there are even some LED cathode biasing for the el84's out there - "Red light district" amp...
Iron for this am would be cheap as well as tubes...lots of new and NOS out there for reasonable prices...complete amp for <$350 most likely and a rockin little PP amp to boot...I have one that is simply CCS cathode biased el84 stage...looking to LED bias the front end someday...
Good info here
Todd,
"Wiring three triodes in series or parallel, to see what that sounds like, doesn't make much sense to me. And switching between the two makes even less sense."
Please elaborate. It's perfectly possible I forgot something obvious that makes this idea ludicrous, but I'd like to know what it is. I can give you details as to why I think it would work, but I apparently haven't been doing this for as long as you, so I'd like to hear your explanation first. I'd also love to read other people's opinions on that.
Thanks in advance,
Ezra
"Wiring three triodes in series or parallel, to see what that sounds like, doesn't make much sense to me. And switching between the two makes even less sense."
Please elaborate. It's perfectly possible I forgot something obvious that makes this idea ludicrous, but I'd like to know what it is. I can give you details as to why I think it would work, but I apparently haven't been doing this for as long as you, so I'd like to hear your explanation first. I'd also love to read other people's opinions on that.
Thanks in advance,
Ezra
Do a search with google for :
POWER AMPLIFIERS with valves
by Claus Byrith
Its a easy read.....
The miller effect is the apparant capacatance seen by circuits when there is gain. Example: the grid to plate cap is multiplied by the gain of the tube circuit and "appears" much larger than the specification states that it is. C* gain= miller C apparant,, so higher gain stages have a higher apparant capacatance...
The down side is every RC portion of the circuit creates a filter with amplitute and phase distortion that can have a disasterous effect on the stability of an amplifier especially if there are too many stages. If I remember right the fs -3db point has a 90 deg phase shift associated with it... IF you have -180 phase shift through the amp and neg feed back, it becomes positive, not good....
POWER AMPLIFIERS with valves
by Claus Byrith
Its a easy read.....
The miller effect is the apparant capacatance seen by circuits when there is gain. Example: the grid to plate cap is multiplied by the gain of the tube circuit and "appears" much larger than the specification states that it is. C* gain= miller C apparant,, so higher gain stages have a higher apparant capacatance...
The down side is every RC portion of the circuit creates a filter with amplitute and phase distortion that can have a disasterous effect on the stability of an amplifier especially if there are too many stages. If I remember right the fs -3db point has a 90 deg phase shift associated with it... IF you have -180 phase shift through the amp and neg feed back, it becomes positive, not good....
Miller, John Milton? He's got quite the capacity to annoy.
I'm going to pick tubes and figure out the schematic for that compactron push-pull power amp tomorrow. Once that's done I'll post that here and figure out what kind of preamp would be best to drive it. If time allows I'll still try to design and test a triple parallel triode preamp stage for it, but in the meantime I guess I'll just stick to something in the vein of the Mullar 5-20 ef86 preamp topology.
Again, I'm learning things here. Apologies if I have randomly strange ideas.
Ezra
I'm going to pick tubes and figure out the schematic for that compactron push-pull power amp tomorrow. Once that's done I'll post that here and figure out what kind of preamp would be best to drive it. If time allows I'll still try to design and test a triple parallel triode preamp stage for it, but in the meantime I guess I'll just stick to something in the vein of the Mullar 5-20 ef86 preamp topology.
Again, I'm learning things here. Apologies if I have randomly strange ideas.
Ezra
After some inspiration from the mullard 4-10, it seems like the pcl86 (13V heater equivalent of the ecl86 - cheap, available) could be a pretty good bet for the power amp. Thoughts?
If no opposition/roadblocks appear, I'll be making a schematic for this, picking a precise OPT and moving on to find an appropriate preamp tube.
@Roline: thanks for that refreshing article.
Thanks as usual for everyone's interesting insight
Ezra
If no opposition/roadblocks appear, I'll be making a schematic for this, picking a precise OPT and moving on to find an appropriate preamp tube.
@Roline: thanks for that refreshing article.
Thanks as usual for everyone's interesting insight
Ezra
If I were to use the pcl86, I would definitely be using it PP. With that I should be getting "almost 10W / channel" - I'll check to see if the person to which this is going to is fine with that. Otherwise, I'll just go with a simpler SE El34 power amp.
I feel like I've been fairly unorganized in the starting of this project, so I'll be doing lots of reading today.
I feel like I've been fairly unorganized in the starting of this project, so I'll be doing lots of reading today.
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Joined 2009
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The construction will take more time than you think if you want to end up with a professional looking job. There's learning to be gained just from the build, positioning of transformers to avoid hum (use of belly straps), safety at high voltage, tuning the operating point for good sound, looking for ringing on the output from transformers etc. It will all be fun - but I'm with DF96 in terms of keeping it simple.
I think you'd learn more of future use if you went with the tone controls than unusual tubes.
I think you'd learn more of future use if you went with the tone controls than unusual tubes.
People have already recommended a few things for simpler, but please feel free to chime in with your own specific tube suggestion, Bigun!
Also, how would I implement tone control? between preamp and power stage, like the ax84 p1? or before the preamp stage, like the mullard 4-10?
Also, how would I implement tone control? between preamp and power stage, like the ax84 p1? or before the preamp stage, like the mullard 4-10?
Hello everyone,
After a lot of reading, here's V0.2 of the schematic. Some things such as an input selector/pilot lamp are missing, but most of it is there. Comments, suggestions and questions welcome!
Thanks in advance,
SI
After a lot of reading, here's V0.2 of the schematic. Some things such as an input selector/pilot lamp are missing, but most of it is there. Comments, suggestions and questions welcome!
Thanks in advance,
An externally hosted image should be here but it was not working when we last tested it.
SI
hi,
you may want to look at this:http://www.diyaudio.com/forums/tubes-valves/183193-tonys-6lu8-push-pull-power-amp-build.html
you may want to look at this:http://www.diyaudio.com/forums/tubes-valves/183193-tonys-6lu8-push-pull-power-amp-build.html
It may be something in my computer/browser setup, but the schematic is far too small & faint to read, for me...
Uploaded it to my own website:
https://lh6.googleusercontent.com/-...AAAAAASs/I6i5k_mN20g/s1600/Schematic+V0.2.png
Please let me know if that works.
https://lh6.googleusercontent.com/-...AAAAAASs/I6i5k_mN20g/s1600/Schematic+V0.2.png
Please let me know if that works.
Much better, especially when using the zoom key.
A couple of comments....it appears that you went a little fuse happy in the PS......one on the mains should do the trick, no?
Consider a choke in place of R21 if budget permits ($15)...and possibly bumping up the value of C14....these will reduce ripple...have you modeled the PS in PSUDII?
Also consider bypassing D2 and D3 with 10nf/2K ceramic caps to reduce switching spike noise.
Since you have a handy 50V bias tap, have you considered fixed bias?
If you are concerned about RF filtering, consider one of Eli's "hash filter" stages in the PS, ie an LC stage with a 1.5mh choke ($2) and a 1000pf cap.
I have no idea what D3 does, but then again I'm also a semi-newbie.....
Did go a little fuse-crazy here. I was following Blencowe's recommendations in "Power supplies for tube amps" and ended up with that.
That, just like a choke in place of R21, will depend on whether or not I get a grant for this project from my school or not.
I didn't do any PSUDII stuff because I don't have windows, but I can have access to it - thanks for suggesting that.
Fixed bias wasn't really considered for the sake of simplicity and costs. Do you have any strong arguments for this specific design? Please do share if that's the case!
Eli's Hash filter sounds like a great idea. I'll add it if I have RF problems.
D3 is half of the two phase rectifier, which I believe is fairly classic (please correct me if I'm wrong). Did you mean D4 or D5? D4 is a "UF4007" fast switching diode to fix the switching noise of the two phase rectifier diodes (D2-3, which I guess is why I don't have ceramic caps bypassing those), and D5 is a way to make the preamp's B+ cleaner (both D4 and 5 are recommendations from Blencowe's "Power Supplies" book).
That, just like a choke in place of R21, will depend on whether or not I get a grant for this project from my school or not.
I didn't do any PSUDII stuff because I don't have windows, but I can have access to it - thanks for suggesting that.
Fixed bias wasn't really considered for the sake of simplicity and costs. Do you have any strong arguments for this specific design? Please do share if that's the case!
Eli's Hash filter sounds like a great idea. I'll add it if I have RF problems.
D3 is half of the two phase rectifier, which I believe is fairly classic (please correct me if I'm wrong). Did you mean D4 or D5? D4 is a "UF4007" fast switching diode to fix the switching noise of the two phase rectifier diodes (D2-3, which I guess is why I don't have ceramic caps bypassing those), and D5 is a way to make the preamp's B+ cleaner (both D4 and 5 are recommendations from Blencowe's "Power Supplies" book).
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