Voltages listed aren't real accurate. Used an old analog meter that shows considerable variation from range to range.
http://img514.imageshack.us/img514/195/experimental169aavl5.png
Figured I'd give it a try , it was easy enough.
I've asked about a similar design before, and basically was told it wouldn't work. It does work , and sounds very good, TONS of midrange resolution , but it just doesn't play loud enough . Perhaps if I had some speakers that were 10db more efficient, but alas , I don't.
This is S O simple. There is really very little to this design. Any thoughts how I can increase the output without increasing the amount of tubes ?I run a passive volume control from the DVD player, no preamp. I've thought of increasing output from my DVD player , but haven't looked into it yet.
Any thoughts ? Besides that I'm a nut ?
...........................Blake
http://img514.imageshack.us/img514/195/experimental169aavl5.png
Figured I'd give it a try , it was easy enough.
I've asked about a similar design before, and basically was told it wouldn't work. It does work , and sounds very good, TONS of midrange resolution , but it just doesn't play loud enough . Perhaps if I had some speakers that were 10db more efficient, but alas , I don't.
This is S O simple. There is really very little to this design. Any thoughts how I can increase the output without increasing the amount of tubes ?I run a passive volume control from the DVD player, no preamp. I've thought of increasing output from my DVD player , but haven't looked into it yet.
Any thoughts ? Besides that I'm a nut ?
...........................Blake
You've built one of these: http://www.triodeel.com/compact.html
But you left out the first AF gain stage. You need to add another tube. Maybe using a transformer instead to get the voltage up might work? I dunno. You're not going to get the output you want with only a 1 volt input swing. You'll need more like 20 volts to fully drive those 6V6.
I wonder what would happen if you rewired the sockets for something like a 6SN7 and adjusted the cathode resistance and output transformer load appropriately?
But you left out the first AF gain stage. You need to add another tube. Maybe using a transformer instead to get the voltage up might work? I dunno. You're not going to get the output you want with only a 1 volt input swing. You'll need more like 20 volts to fully drive those 6V6.
I wonder what would happen if you rewired the sockets for something like a 6SN7 and adjusted the cathode resistance and output transformer load appropriately?
I've looked at that schematic a time or two . 
I was just looking on the Triode Electronics website. Seems as though if I were to run these Pentode I would get considerabley more output from them.
From what I've read, it seems that Pentodes typically need about 1/3rd as much drive as compared to the same tube run Triode to achieve the same power output. In other words, much less input = equivalent output , or same input = considerabley more output. I'm gonna go switch them over to Pentode. I'll let ya know what happens. . . .
..........................Blake
I was just looking on the Triode Electronics website. Seems as though if I were to run these Pentode I would get considerabley more output from them.
From what I've read, it seems that Pentodes typically need about 1/3rd as much drive as compared to the same tube run Triode to achieve the same power output. In other words, much less input = equivalent output , or same input = considerabley more output. I'm gonna go switch them over to Pentode. I'll let ya know what happens. . . .
..........................Blake
DigitalJunkie said:
Basically the same as my suggestion. I meant 1 tube / channel
Audiowize, did you mean the 6EM7's instead of the 6V6's ? Meaning in a single gain stage ?
I hooked them up like this now :
http://img101.imageshack.us/img101/2637/experimental169aapentodcn9.png
Plays louder , still not loud enough. I don't seem to like Pentodes as much as Triode tied pentodes. They just don't seem to do it for me. This setup sounds good, but not as good as the first one I tried.
Just so you guys know where I'm coming from, my main setup is currently this :
http://img101.imageshack.us/img101/5166/myampschematic169aarevizj4.png
http://img101.imageshack.us/img101/7069/myrevisedpowersupplyforfn4.png
I think I need to lose the triode tied 6an8. I have some new matched Sovtek 6SL7's and some sockets to go with. Should I go for them, or not a good match for triode tied 6V6's ? I'm actually running 6p6s, or a Russian 6V6 style Tetrode.
Anyway, what are the thoughts on the 6SL7 ?
...................................Blake
I hooked them up like this now :
http://img101.imageshack.us/img101/2637/experimental169aapentodcn9.png
Plays louder , still not loud enough. I don't seem to like Pentodes as much as Triode tied pentodes. They just don't seem to do it for me. This setup sounds good, but not as good as the first one I tried.
Just so you guys know where I'm coming from, my main setup is currently this :
http://img101.imageshack.us/img101/5166/myampschematic169aarevizj4.png
http://img101.imageshack.us/img101/7069/myrevisedpowersupplyforfn4.png
I think I need to lose the triode tied 6an8. I have some new matched Sovtek 6SL7's and some sockets to go with. Should I go for them, or not a good match for triode tied 6V6's ? I'm actually running 6p6s, or a Russian 6V6 style Tetrode.
Anyway, what are the thoughts on the 6SL7 ?
...................................Blake
OK, so I looked up the 6EM7's. I see they are a dual stage tube , meaning a driver and output triode in one glass tube. That answers that question.
Digital Junkie, I see you've posted a Magnavox schematic. Perhaps you noticed my amp started life as such ?
I'm gonna look into a 1:10 step up transformer. Thanks guys.
..............................Blake
Digital Junkie, I see you've posted a Magnavox schematic. Perhaps you noticed my amp started life as such ?
I'm gonna look into a 1:10 step up transformer. Thanks guys.
..............................Blake
its all been done before...
why use a tranny? Put just one triode in front of the first output tube and you have all the gain you need. Pretty much anything will do it - you only need to get to the max swing voltage of one tube after all. See www.diyparadise.com or http://diyaudioprojects.com/Tubes/EL84-Push-Pull/ for a more complex implimentation. The second link also has links to implimentations with KT77 and KT88 outputs.
why use a tranny? Put just one triode in front of the first output tube and you have all the gain you need. Pretty much anything will do it - you only need to get to the max swing voltage of one tube after all. See www.diyparadise.com or http://diyaudioprojects.com/Tubes/EL84-Push-Pull/ for a more complex implimentation. The second link also has links to implimentations with KT77 and KT88 outputs.
Nihilist,
Got any 6SN7's? You can use those in the octal sockets and follow the schematic I posted. The sound is SWEET, with your PSU and the good size of your OPT's (my Grandma has a similar console and I am just waiting for her to say she doesn't need it anymore) you should REALLY enjoy it.
You can also use the 6SL7's but will need to drop the plate voltage to 250V (max for 6sl7)
Run the V6's in TRIODE, the extra power in Pentode is not worth it, as you seem to have already learned.
Since you have the sov sl7's I would go back to the original plan with the ~400V B+ and add in the sl7's as one gain stage and 1 phase splitter as shown in my schematic.
If you don't mind my ".02 cents" I am bored today so I will draw up a schematic for you. I built a VERY SIMILAR amp and find it to be one of the best sounding amps (on a budget) I have heard. You might want to consider losing the NFB also. Or place a switch in it to hear side by side. I use no feedback and it is very clean.
Got any 6SN7's? You can use those in the octal sockets and follow the schematic I posted. The sound is SWEET, with your PSU and the good size of your OPT's (my Grandma has a similar console and I am just waiting for her to say she doesn't need it anymore) you should REALLY enjoy it.
You can also use the 6SL7's but will need to drop the plate voltage to 250V (max for 6sl7)
Run the V6's in TRIODE, the extra power in Pentode is not worth it, as you seem to have already learned.
Since you have the sov sl7's I would go back to the original plan with the ~400V B+ and add in the sl7's as one gain stage and 1 phase splitter as shown in my schematic.
If you don't mind my ".02 cents" I am bored today so I will draw up a schematic for you. I built a VERY SIMILAR amp and find it to be one of the best sounding amps (on a budget) I have heard. You might want to consider losing the NFB also. Or place a switch in it to hear side by side. I use no feedback and it is very clean.
Here try this
Nihilist,
I looked over what you had in triode mode and you still were really pounding on the tubes.
Also, you might have had issues with the PSU, In order for the 100K resistor to only drop 83 volts your ENTIRE (332V) circuit had to draw only 0.8 Milliamps? Also with the HUGE cap it would take like maybe 1 minute or more to come up to whatever voltage. I think maybe you are using either a different value resistor or your voltage is WAY off?
Either way It still needs to follow Ohms Law. I suspect that maybe there is like only 100 volts there at the plates or less.
Attached is something to try with the 6SL7's. I got rid of the Bias Supply and went self bias using your existing 500R resistor. Move the 180U cap from the (332V) supply and use it as Cathode Bypass.
Add a smaller Cap like something between 33uF and 47uF along with a like 10K resistor for that side.
This should give you more than enough gain so you could put a volume pot (100K???) in place of the 47K input grid load resistor.
Nihilist,
I looked over what you had in triode mode and you still were really pounding on the tubes.
Also, you might have had issues with the PSU, In order for the 100K resistor to only drop 83 volts your ENTIRE (332V) circuit had to draw only 0.8 Milliamps? Also with the HUGE cap it would take like maybe 1 minute or more to come up to whatever voltage. I think maybe you are using either a different value resistor or your voltage is WAY off?
Either way It still needs to follow Ohms Law. I suspect that maybe there is like only 100 volts there at the plates or less.
Attached is something to try with the 6SL7's. I got rid of the Bias Supply and went self bias using your existing 500R resistor. Move the 180U cap from the (332V) supply and use it as Cathode Bypass.
Add a smaller Cap like something between 33uF and 47uF along with a like 10K resistor for that side.
This should give you more than enough gain so you could put a volume pot (100K???) in place of the 47K input grid load resistor.
Attachments
Nihilist said:
I don't see how that could work. That 270R resistor makes for a very short tail, even for a solid state amp, and looks to be way too small for a low gain device like a trioded 6V6. Ideally, that should have a CCS as the tail load.
As for why it isn't louder, you need front end voltage gain. Trioded 6V6s are strictly low gain, and require a bigger input swing to get close to max output.
Solid state front end..
Not sure what you're talking about with the 332V and 100k resistor deal. Image shack is down right now, so I can't see what I posted. Perhaps I goofed on the schematic.
As I've said , I heard that before. It DOES work, it is quiet. My speakers are about 96-97db and it is like a low volume background music for an office waiting area.
Not an F ' in chance.
Thanks for the input. I'll type at you guys later , gotta go.
PS, I'm listening in pentode mode right now. It plays louder than you would think. I'm in another room and hear it clearly. Still not anywhere near as loud as the setup with the 6AN8, but much louder than the Triode strapped 6V6 setup.
............................Blake
Simple Ohm's Law
The schematic shows a 470R resistor then a 100K resistor. Source voltage at the rectifier is about 415-420 so if your getting 332V at that point you can only be drawing
(415-332= 83V /100000 = .0008mA)
On top of that I guesstimate that it would take like 5 or 6 minutes to charge that cap.
I suspect that it is more likely a TEN K resistor and the draw is more like 3.3mA that would get you around 332V.
I really suggest you try the circuit I drew for you on one of the amps. It is very similar to the amp I am listening to now.
I can't drive it to the max with the little soundcard from my PC (I need about 2+V RMS and can only get about 500mV) and with 88/dB speakers I can tic the wife off 2 floors UP!!
You should wind up with an input gain of about 20+ that should be able to drive the 6v6 in triode pretty good.
Here's a look at the original schematic. You tell me.
http://img95.imageshack.us/img95/8755/stock169aaampas5.png
http://img26.imageshack.us/img26/7889/stock169aapsro4.png
I only ran the NFB loop in Pentode mode , as without it , it doesn't sound good. When I run Triode, no NFB, never even tried Triode with NFB.
ColdCathode , In your schematic you show a 6800 ohm (?) resistor tieing the grid to the plate. Am I reading that correctly, 6800 ohm ? Seems awefully high.
Gotta get up at 3:30am. I have some more to ask/talk about , but I gotta go. Talk at you gents tommorry.
.............................Blake
http://img95.imageshack.us/img95/8755/stock169aaampas5.png
http://img26.imageshack.us/img26/7889/stock169aapsro4.png
I only ran the NFB loop in Pentode mode , as without it , it doesn't sound good. When I run Triode, no NFB, never even tried Triode with NFB.
ColdCathode , In your schematic you show a 6800 ohm (?) resistor tieing the grid to the plate. Am I reading that correctly, 6800 ohm ? Seems awefully high.
Gotta get up at 3:30am. I have some more to ask/talk about , but I gotta go. Talk at you gents tommorry.
.............................Blake
Nihilist said:
If you got it to work and like how it sounds, there's no argueing with that.
You're not leaving yourself with very many choices here. It's either put up with the low volume or increase the voltage to the finals somehow. If you don't want a SS front end, and you don't want to make another hole for a hollow state voltage amp (I'd suggest a trioded 6AU6 for this: excellent linearity, and just the right amount of front end gain) then you'll have to either add a step up xfmr, or find another source with higher output voltages.
Looking at the original the 100K makes a little more sense. 1mA to the input section.
You seem to want to run the 6V6's @ the impossibly high plate voltage of like 370 volts. The max grid2 V is about 250 and dissipation is (triode) need to drop that voltage somewhere.
If you want the plates to glow that's your choice but I am not sure the grids can handle that voltage since you had them tied directly to the plate.
I am not the best @ calculating the grid resistors but @ 7mA grid current that resistor only drops the voltage from 400 to 350 I am guessing that at idle you should see something like 375 volts which is still significantly higher than the absolute max of 315.
This hobby allows for lots of variability but there are some ABSOLUTE TRUTHS.
1) We must OBEY the laws of physics
(ie we can't get something for nothing)
2) Ohm's Law
What I am getting at is we all acknowledge that what you have built WILL make sound. It is just that it won't make A LOT of sound and will NOT make it very musical.
I ran your design on PP Calc and I get LOTS of RED BOXES and unless the gain of the pentode input is better than 20 I don't see how you could be getting more than say 1/2 watt. Since you have pretty efficient speakers it might sound "OK" just quiet.
Can I ask why you want such a high B+ voltage?
I understand that you wind up with a pretty high voltage when you go with the SS rectification but a couple $2 resistors can fix that and with the nice size caps you already have you can make it a LOT quieter than it is and was as far as ripple.
What EXACTLY are your goals?
As I have drawn the circuit for you, you should see about 9 watts/channel RMS w/ your speakers peak dB of about 100.
Assuming about a 2 volt input swing. 1V RMS output of DVD/CD player since the input section has a gain of about 20.
2Watts/Ch if the swing is 1 or 500mV RMS
The Corner frequency of the input to the splitter is about 13hz or 3db down @ 13 and Flat @ 26hz. Should be below the response of your speakers anyway.
The Corner frequency of the input to the power stage is a little high and you might want to adjust that if the speakers can play well below 40hz. The 0.1uf F3=~24 or flat @ 48 a 0.22 will bring that down to flat at ~20hz
Shout back with any questions as I am FAR from and expert, but have built a couple 6V6 PP's
You seem to want to run the 6V6's @ the impossibly high plate voltage of like 370 volts. The max grid2 V is about 250 and dissipation is (triode) need to drop that voltage somewhere.
If you want the plates to glow that's your choice but I am not sure the grids can handle that voltage since you had them tied directly to the plate.
I am not the best @ calculating the grid resistors but @ 7mA grid current that resistor only drops the voltage from 400 to 350 I am guessing that at idle you should see something like 375 volts which is still significantly higher than the absolute max of 315.
This hobby allows for lots of variability but there are some ABSOLUTE TRUTHS.
1) We must OBEY the laws of physics
(ie we can't get something for nothing)
2) Ohm's Law
What I am getting at is we all acknowledge that what you have built WILL make sound. It is just that it won't make A LOT of sound and will NOT make it very musical.
I ran your design on PP Calc and I get LOTS of RED BOXES and unless the gain of the pentode input is better than 20 I don't see how you could be getting more than say 1/2 watt. Since you have pretty efficient speakers it might sound "OK" just quiet.
Can I ask why you want such a high B+ voltage?
I understand that you wind up with a pretty high voltage when you go with the SS rectification but a couple $2 resistors can fix that and with the nice size caps you already have you can make it a LOT quieter than it is and was as far as ripple.
What EXACTLY are your goals?
As I have drawn the circuit for you, you should see about 9 watts/channel RMS w/ your speakers peak dB of about 100.
Assuming about a 2 volt input swing. 1V RMS output of DVD/CD player since the input section has a gain of about 20.
2Watts/Ch if the swing is 1 or 500mV RMS
The Corner frequency of the input to the splitter is about 13hz or 3db down @ 13 and Flat @ 26hz. Should be below the response of your speakers anyway.
The Corner frequency of the input to the power stage is a little high and you might want to adjust that if the speakers can play well below 40hz. The 0.1uf F3=~24 or flat @ 48 a 0.22 will bring that down to flat at ~20hz
Shout back with any questions as I am FAR from and expert, but have built a couple 6V6 PP's
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