Hi all-
I am once again heavily in a tube mood and searching for a simple, cheap amp to build... and perhaps might have finally found what I needed all along. Well, sort of...
The 6080/6AS7 is closely related to a 2A3... so, why not make a SET amp out of one 6AS7 and one driver tube (probably 6SL7)? I really need the project to be cheap... so using only two tubes for stereo operation really cuts down on the costs. I don't need a lot of power... 2-6W is it, really.
I have searched the forums, and found a thread by Joel regarding a Parafeed amp like this... but the chokes are WAY too large for me... I cannot spend that much. I need this to be as minimalistic as possible, while still sounding good.
Does anyone know of any links to any circuits like this? I found the Lilliput amp... and it looks really nice... but I was wondering if there were any similar to it, but maybe a tad better. It uses solid state rectification... and from what I understand 6AS7's like slow turn on supplies. Would this hurt the tube?
If someone can clarify anything, I would appreciate it. Thanks!!
I am once again heavily in a tube mood and searching for a simple, cheap amp to build... and perhaps might have finally found what I needed all along. Well, sort of...
The 6080/6AS7 is closely related to a 2A3... so, why not make a SET amp out of one 6AS7 and one driver tube (probably 6SL7)? I really need the project to be cheap... so using only two tubes for stereo operation really cuts down on the costs. I don't need a lot of power... 2-6W is it, really.
I have searched the forums, and found a thread by Joel regarding a Parafeed amp like this... but the chokes are WAY too large for me... I cannot spend that much. I need this to be as minimalistic as possible, while still sounding good.
Does anyone know of any links to any circuits like this? I found the Lilliput amp... and it looks really nice... but I was wondering if there were any similar to it, but maybe a tad better. It uses solid state rectification... and from what I understand 6AS7's like slow turn on supplies. Would this hurt the tube?
If someone can clarify anything, I would appreciate it. Thanks!!
if you use a normal SE OPT, you'll need something in the 1k zone.. if i remember correctly. Which is kind of an off value, so it may be hard to find, unless you wind it.
I wouldnt worry about soft turn on - 6080s are tough ****ers, and pretty cheap too.
you could always just run 8 of them, OTL. but then you would have to spend the money you saved on the OPT on the big power transformers, extra tubes and some big caps. 😉
I wouldnt worry about soft turn on - 6080s are tough ****ers, and pretty cheap too.
you could always just run 8 of them, OTL. but then you would have to spend the money you saved on the OPT on the big power transformers, extra tubes and some big caps. 😉
You'll never get enough output from a 6SL7 to drive the 2 mu on that bastage. You need more supply volts or a choke loaded driver to do this one.
Or like Colt sez. 😛
Tim
Or like Colt sez. 😛
Tim
Hi,
Check this Svetlana's page: http://www.svetlana.com/docs/tubeframe.html
http://www.svetlana.com/graphics/TB/No.26fig1.jpg
http://www.svetlana.com/graphics/TB/No.26fig2.jpg
There's a schema for 6AS7G.
If you would like to use only one tube/channel (+rectifier), check this page: http://digilander.libero.it/giunchifabrizio/ECL86amply.htm
I've built two ECL86-SE monoblocks with PCL86 tubes. The PCL86 is cheaper and easier to find. The only difference is the V they work (6,3/12V).
Best regards,
Pete
Check this Svetlana's page: http://www.svetlana.com/docs/tubeframe.html
http://www.svetlana.com/graphics/TB/No.26fig1.jpg
http://www.svetlana.com/graphics/TB/No.26fig2.jpg
There's a schema for 6AS7G.
If you would like to use only one tube/channel (+rectifier), check this page: http://digilander.libero.it/giunchifabrizio/ECL86amply.htm
I've built two ECL86-SE monoblocks with PCL86 tubes. The PCL86 is cheaper and easier to find. The only difference is the V they work (6,3/12V).
Best regards,
Pete
Konnichiwa,
It is? So a 2A3 is an indirectly framed grid valve? That's news to me.
Becuase it will not work too well?
Something taht fits the bill of "cheap and easy" is a variation of the "Maurits" by Menno van der Veen. I commented on this here:
http://www.diyaudio.com/forums/showthread.php?postid=351756#post351756
You should have come across this had you searched diyaudio for 6AS7 AND Amplifier.
Also, there is a Website with someones Experiences building a similar Amplifier to the Maurits, including the use of Mains Torroids as output transformer.
http://www.triodeguy.com/6as7_pp.htm
I would probably re-design the Amp by "bootstrapping" the driver from the opposite Anode (return the Anode resistor to the Anode of the halve of the 6AS7 not driven by this Valve and use a 5687/E182CC or ECC99 as driver and a 6072A or the like as driver. Anyway, plenty of scope optimising the driver circuit.
Sayonara
needtubes said:
It is? So a 2A3 is an indirectly framed grid valve? That's news to me.
needtubes said:
Becuase it will not work too well?
needtubes said:
Something taht fits the bill of "cheap and easy" is a variation of the "Maurits" by Menno van der Veen. I commented on this here:
http://www.diyaudio.com/forums/showthread.php?postid=351756#post351756
You should have come across this had you searched diyaudio for 6AS7 AND Amplifier.
Also, there is a Website with someones Experiences building a similar Amplifier to the Maurits, including the use of Mains Torroids as output transformer.
http://www.triodeguy.com/6as7_pp.htm
I would probably re-design the Amp by "bootstrapping" the driver from the opposite Anode (return the Anode resistor to the Anode of the halve of the 6AS7 not driven by this Valve and use a 5687/E182CC or ECC99 as driver and a 6072A or the like as driver. Anyway, plenty of scope optimising the driver circuit.
Sayonara
Pcl 86's filaments volatage is 13V or 13.2v not 12v. Underfeeding the filaments may not be a good idea.
Cheers.
Cheers.
Konnichiwa,
Underfeeding filaments (within reason) is a most excellent idea, unless you operate Valves at absolute max cathode current (emission). As long as the continous cathode current is no more than around 50% rated maximum operating valves with the heater at the lower tolerance limit (-10% usually for heater/cathode construction valves) the lifespan of the Valve rises to 200 - 400% of that at nominal filament voltages. Plus, underheating sounds better with MOST Valves (but not all and not in all application).
Sayonara
alk said:
Underfeeding filaments (within reason) is a most excellent idea, unless you operate Valves at absolute max cathode current (emission). As long as the continous cathode current is no more than around 50% rated maximum operating valves with the heater at the lower tolerance limit (-10% usually for heater/cathode construction valves) the lifespan of the Valve rises to 200 - 400% of that at nominal filament voltages. Plus, underheating sounds better with MOST Valves (but not all and not in all application).
Sayonara
,
I had read the contrary...guess too many ppl writing without knowing. 😉
I trust your knowledge though... this info will stay. Thanks.
Cheers!
I had read the contrary...guess too many ppl writing without knowing. 😉
I trust your knowledge though... this info will stay. Thanks.
Cheers!
Konnichiwa,
I have studies both from the US and Europe from "the good olde days" which bear out the increase in lifespan. Note thatexcessive underheating can shorten life, overheating will DEFINITLY shorten life.
The 200 - 400% extended lifespan come froma Philips study.
All in all running valves conservative (try staying at or below 50% max rated anode dissipation and near 50% max rated anode current, also underheat at lower rated limited for heaters) can drastically extend valve life. A (power) Valve having 2,000-4,000 Hours expected live under the usual near max rating operation will hold usually four times as long (and longer) operated in ways I call "conservative". With small signal valves >40,000 Hours are easily possible.
With that even expensive NOS Valves are no real concern.
Sayonara
alk said:
I have studies both from the US and Europe from "the good olde days" which bear out the increase in lifespan. Note thatexcessive underheating can shorten life, overheating will DEFINITLY shorten life.
The 200 - 400% extended lifespan come froma Philips study.
All in all running valves conservative (try staying at or below 50% max rated anode dissipation and near 50% max rated anode current, also underheat at lower rated limited for heaters) can drastically extend valve life. A (power) Valve having 2,000-4,000 Hours expected live under the usual near max rating operation will hold usually four times as long (and longer) operated in ways I call "conservative". With small signal valves >40,000 Hours are easily possible.
With that even expensive NOS Valves are no real concern.
Sayonara
I love building my own things... and have always wanted to build a tube amp, but don't want to deal with a really difficult design for my first amp. So, I just wanted something simple and cheap... and I figured I could use 1/2 of a 6AS7 for each channel and 1/2 of a driver.
However, I will be abandoning this project because like many of my other projects, I received less than friendly help from certain individuals. NO I do NOT know everything there is about tubes, which is why I was asking questions. I was basing what I said on things that I have heard or read... so oops if some things were incorrect.
There are a few friendly folks in the tube areas, and I apologize to those who are friendly and offer very nice help. However, everytime I post a topic asking for help I get met with some sort of hostility, and to be quite honest, I'd rather remain tube-less than have to put up with being made fun of for making a mistake that I was told to think was correct. I have never had a thread that ended well where I got the help I needed- otherwise I would have a tube amp right now and would have had one for some time.
So, I am leaving now, and shall NOT return to the tube forums again. I will seek help elsewhere...
However, I will be abandoning this project because like many of my other projects, I received less than friendly help from certain individuals. NO I do NOT know everything there is about tubes, which is why I was asking questions. I was basing what I said on things that I have heard or read... so oops if some things were incorrect.
There are a few friendly folks in the tube areas, and I apologize to those who are friendly and offer very nice help. However, everytime I post a topic asking for help I get met with some sort of hostility, and to be quite honest, I'd rather remain tube-less than have to put up with being made fun of for making a mistake that I was told to think was correct. I have never had a thread that ended well where I got the help I needed- otherwise I would have a tube amp right now and would have had one for some time.
So, I am leaving now, and shall NOT return to the tube forums again. I will seek help elsewhere...
Hi,
The Lilliput amp is a very good sounding little amp. In fact, I think I must have mentioned this before, I heard it perform on horn loaded Sowthers a few times and was impressed.
Frankly, I couldn't care less if it used a diode bridge or anything else....The results were there and it obviously worked.
Short of trying every single PS topology out on it it's hard to predict how it's going to sound with this little gem.
Actually it sounded very similar to the AN Baransu 300B amp another friend uses on his Sowthers which is very high praise in anyone's book, I reckon.
If it's any help, I have the complete schematics and text (in Italian) for the Lilliput amp.
Common, the tube forum is about as friendly as it gets.
Hang in there, ask whatever questions you like to ask....We're ALL learning here...
Cheers, 😉
The Lilliput amp is a very good sounding little amp. In fact, I think I must have mentioned this before, I heard it perform on horn loaded Sowthers a few times and was impressed.
Frankly, I couldn't care less if it used a diode bridge or anything else....The results were there and it obviously worked.
Short of trying every single PS topology out on it it's hard to predict how it's going to sound with this little gem.
Actually it sounded very similar to the AN Baransu 300B amp another friend uses on his Sowthers which is very high praise in anyone's book, I reckon.
If it's any help, I have the complete schematics and text (in Italian) for the Lilliput amp.
Common, the tube forum is about as friendly as it gets.
Hang in there, ask whatever questions you like to ask....We're ALL learning here...
Cheers, 😉
Hi,
Note also that this information has been put on the forum by yours truly before.
Yours truly also appreciates it when such critical information is given correctly and completely.
A little explanation or some references as to WHY underheating is a good thing would help to show the people new to valves where the pratical limits are....
Oh, the 6AS7, as so many other triodes is related to the 2A3 historically. Whether the DHT gods like it or not.
Cheers,😉
Note also that this information has been put on the forum by yours truly before.
Yours truly also appreciates it when such critical information is given correctly and completely.
A little explanation or some references as to WHY underheating is a good thing would help to show the people new to valves where the pratical limits are....
Oh, the 6AS7, as so many other triodes is related to the 2A3 historically. Whether the DHT gods like it or not.
Cheers,😉
Needtubes hope you read this, frankly, i see no unfriendly attitude from noone. Some ppl are just not interested, that''s all. There are a lot of simple designs out there and simple isn't synonymous of bad. I also like the Lilliput and, if i were you ,would follow Frank's advice. It is simple and cheap - just what you asked for.
But if you get annoyed easily maybe you shouldn't try...what would happen if it doesn't work?😀
But if you get annoyed easily maybe you shouldn't try...what would happen if it doesn't work?😀
Ok... I apologize for that... heh I have been somewhat lacking sleep lately, that could have onset the slight irritation at comments which may not have been meant rudely... So, forget that, if possible. 
It is too hard to leave this place anyway....
Anyway... Thanks fdegrove for the post about the Lilliput... I had seen the schematic, but was wondering if there was somethign better out there. The one I saw was a little unclear, but I think I got all of the parts values off of it.
I have also seen the Svetlana circuit... but it uses a little too high of voltage for my taste. I would be a lot more comfortable with a lot less voltage... Anyway, I will look again at the Lilliput when I return from dinner... compare some prices... and approximate how much that thing would set me back. The problem is not necessarily having the money.... it is parting with it.
I just wanted my first project to be cheap... so in case I do fry something, the parts wouldn't break me. Thanks all
edit- alk-- I can be annoyed easily sometimes... but I am really calm for the most part. 😉
EDIT again: Couldn't wait until after dinner to check a few things... Is it possible to substitute a different tube in the driver section of the Lilliput? If so, what would be some suitable ones?
It is too hard to leave this place anyway....Anyway... Thanks fdegrove for the post about the Lilliput... I had seen the schematic, but was wondering if there was somethign better out there. The one I saw was a little unclear, but I think I got all of the parts values off of it.
I have also seen the Svetlana circuit... but it uses a little too high of voltage for my taste. I would be a lot more comfortable with a lot less voltage... Anyway, I will look again at the Lilliput when I return from dinner... compare some prices... and approximate how much that thing would set me back. The problem is not necessarily having the money.... it is parting with it.
I just wanted my first project to be cheap... so in case I do fry something, the parts wouldn't break me. Thanks alledit- alk-- I can be annoyed easily sometimes... but I am really calm for the most part. 😉
EDIT again: Couldn't wait until after dinner to check a few things... Is it possible to substitute a different tube in the driver section of the Lilliput? If so, what would be some suitable ones?
Hi,
Glad you changed your mind...
I suppose there's always going to be something "better" out there but if you're looking for a small power amp then the Lilliput is hard to beat and comes with excellent specs to boot.
The scans on the Audiokit site (there are several ones*) aren't doing the kit much justice but the sound really makes up for it.
Regarding your concern about the use of silicon diodes in the PS, most of the noise will be snubbed by the choke and if you really want to you can use Schottky diodes or put snubbers across the 1N4007s.
I heard the kit in its standard form and was already blown away by the sound. It doesn't sound like an overly romantic tubeamp at all but rather crystal clear and precise.
This is how I like an amp to be regardless of topology or genetic persuasion but it may not be to everyone's liking.
All this doesn't really matter to me as with careful choice of passive components it can be made to sound to fit anyone's taste/system, I'm sure. Me, I stick with the neutral/accurate presentation.
Either way, if you need help with the project, I'm sure there's plenty of people around here to lend a hand. Myself included.
* When you're going to the site and are looking at http://www.audiokit.it/ITAENG/KitElettr/MEGA/Lilliput/Lillman4.gif
replace Lillman4.gif by Lillman3, *2 etc, to see the rest of the scans.
Cheers and chin up, 😉
Glad you changed your mind...
I suppose there's always going to be something "better" out there but if you're looking for a small power amp then the Lilliput is hard to beat and comes with excellent specs to boot.
The scans on the Audiokit site (there are several ones*) aren't doing the kit much justice but the sound really makes up for it.
Regarding your concern about the use of silicon diodes in the PS, most of the noise will be snubbed by the choke and if you really want to you can use Schottky diodes or put snubbers across the 1N4007s.
I heard the kit in its standard form and was already blown away by the sound. It doesn't sound like an overly romantic tubeamp at all but rather crystal clear and precise.
This is how I like an amp to be regardless of topology or genetic persuasion but it may not be to everyone's liking.
All this doesn't really matter to me as with careful choice of passive components it can be made to sound to fit anyone's taste/system, I'm sure. Me, I stick with the neutral/accurate presentation.
Either way, if you need help with the project, I'm sure there's plenty of people around here to lend a hand. Myself included.
* When you're going to the site and are looking at http://www.audiokit.it/ITAENG/KitElettr/MEGA/Lilliput/Lillman4.gif
replace Lillman4.gif by Lillman3, *2 etc, to see the rest of the scans.
Cheers and chin up, 😉
There was a nice little amp posted elsewhere in this forum which uses half a 12AT7 to drive half a 5998 for a two tube stereo amp. The 5998 is a cousin of the 6AS7G but with higher mu. If you want to use the 6AS7G/6080, I don't see why you couldn't adapt that circuit to use one half of the 6AS7G to drive the other half via a 1:2 interstage transformer with a 1K - 1.5K OPT. Don't let the forum Nazis get you down.
John
John
5998
Hi,
This the one you had in mind, John?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=30209&highlight=
It's from the same hand as the Lilliput, BTW.
Cheers,😉
Hi,
This the one you had in mind, John?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=30209&highlight=
It's from the same hand as the Lilliput, BTW.
Cheers,😉
Yes, that's it. Mine is in the works, but I am substituting 7236 for 5998 (it's what I had on hand) and 6BY5GA for expensive 5AR4.
John
John
Glad you decided to stay!
You might be able to save on the output transformer by using a MOSFET current source to load your output stage and then using a capacitor to couple to your smaller) output transformer which will no longer have to handle the DC bias current. Of course you will need to have access to a transformer with adequate high voltage windings.
Check out Steve Bench's description of output circuits here. He also has an amplifier that uses power toriods as output transformers. That amp has no power transformer either so it has to be carefully constructed but it might be worth looking at. Steve's Cheap Output Tranformer Amp
You might be able to save on the output transformer by using a MOSFET current source to load your output stage and then using a capacitor to couple to your smaller) output transformer which will no longer have to handle the DC bias current. Of course you will need to have access to a transformer with adequate high voltage windings.
Check out Steve Bench's description of output circuits here. He also has an amplifier that uses power toriods as output transformers. That amp has no power transformer either so it has to be carefully constructed but it might be worth looking at. Steve's Cheap Output Tranformer Amp
Re: Glad you decided to stay!
commonly called parafeed... a choke is often used instead of a current source.
I cannot emphasize enuff how dangerous this is... and if your insurance company ever finds out after your house burns down, you are likely out of luck.
dave
mashaffer said:
commonly called parafeed... a choke is often used instead of a current source.
I cannot emphasize enuff how dangerous this is... and if your insurance company ever finds out after your house burns down, you are likely out of luck.
dave
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