Well if I put in the switch it will include UL.
Sounds like the sag described is for guitar and MI amps not hifi. It does clips softly so I guess you can say it compresses a little. I use SMPS for b+ and it will sag a little if I let the amp clip but I dont so not an issue.
I need to experiment with the feedback. That is not settled.
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You said your AMP clips at 2 watts, I found an article with a 6W6 / 6Y6 SE The Power supply is CRC filtered solid state, with a large 680 ohm resister. The article stated the power supply has a lot of sag. The output voltage varies greatly with load. The amplifier never ‘clips’ when overdriven, it simply compresses!
Wont be much sag, it is a Class A Amplifier.🙂 Once the load is set there will be little change.. CLC still much better for triode output stage.
Wont be much sag, it is a Class A Amplifier.🙂 Once the load is set there will be little change.. CLC still much better for triode output stage.
In overdriven guitar amps class-A will also draw more from the supply because the output is no longer symmetrical sinus. But I would still say the output clips tho it is rather soft and rounded.
Actually if biased too hot the opposite can happen where the voltage cant swing any lower on the plate but it can swing more positive. Then the b+ will increase and you have asymmetric clip with loads of even harmonics without compression. The b+ can increase almost to the rectifier output voltage (0 drop over the series filter resistor).
All too true. But driven too & beyond clipping is hardly Class A. During normal operation in a properly biased Class A stage the plate current does increase to a small degree as the bias point shifts to the left on the plate family of curves. Sometimes called rectification, it is simply the zeroth harmonic of the even order harmonics created by a triode amplifier. Those would be 2nd, 4th, 6th & so on. And the first term of the Fourier Series DC (0th).
The example here shows that a one volt ripple on the PS will result in ~3/4V AC potential developed across the OPT primary. And the resulting AC hum in the loudspeaker.
So whatever your hum voltage is, 3/4 of that will be on the OPT primary.🙂
The example here shows that a one volt ripple on the PS will result in ~3/4V AC potential developed across the OPT primary. And the resulting AC hum in the loudspeaker.
So whatever your hum voltage is, 3/4 of that will be on the OPT primary.🙂
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I agree. So I wonder if Dsary is building a guitar amp...?
Regarding ripple on the output isnt it depending on the impedances of OPT and tube rp? They form a voltage divider where the ripple will be greater over the greater Z. This is one problem with low rp tubes. Most of the ripple falls over the OPT and out to the speakers. On 6AS7 SE amps some sort of ripple cancellation is required. Check out tubecad.com for that.
Regarding ripple on the output isnt it depending on the impedances of OPT and tube rp? They form a voltage divider where the ripple will be greater over the greater Z. This is one problem with low rp tubes. Most of the ripple falls over the OPT and out to the speakers. On 6AS7 SE amps some sort of ripple cancellation is required. Check out tubecad.com for that.
All Triodes Have the Same Damping Factor
The max output for an ideal triode occurs when the load impedance Rl is 2x rp. In practice max output occurs at more like 2.5X rp. Bur D% is high. So in good practice Rl would be better at ~4rp where the D% is much less. That sets the bare DF at ~4 (Rl / rp). But the DF after the OPT will be less.
All triodes will be similarly affected by PS ripple for the same reasons.🙂
The max output for an ideal triode occurs when the load impedance Rl is 2x rp. In practice max output occurs at more like 2.5X rp. Bur D% is high. So in good practice Rl would be better at ~4rp where the D% is much less. That sets the bare DF at ~4 (Rl / rp). But the DF after the OPT will be less.
All triodes will be similarly affected by PS ripple for the same reasons.🙂
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Hi Fi Amp
Sorry for delay in response I am getting ready to move overseas and trying to read up and understand filtering for power supply.
There has been recommendation for a better filtering and look for a improved circuit than the 12L6 mini single ended circuit to base the 6W6 on I am very new at this basically 0 experience.
Sorry for delay in response I am getting ready to move overseas and trying to read up and understand filtering for power supply.
There has been recommendation for a better filtering and look for a improved circuit than the 12L6 mini single ended circuit to base the 6W6 on I am very new at this basically 0 experience.
circlet design
There has been feedback on weakness in the 12L6 Mini single ended circlet design. I thought this would be good circuit to start with for 6W6 circlet design & build. Some feedback on this circlet design, better filtering and negative feedback a I found two more 6W6 circuits (See attached) and SemperFi graciously provide his circlet design.
“6DG6GT Magic Amp” (attached) = 5UGB rectifier tube and has no negative feedback and mentioning of weakness in bass response has resonance.
“Low voltage Madness” (attached) = rectifier uses CRC filtered solid state power supply a lot of what is termed as “sag
There has been feedback on weakness in the 12L6 Mini single ended circlet design. I thought this would be good circuit to start with for 6W6 circlet design & build. Some feedback on this circlet design, better filtering and negative feedback a I found two more 6W6 circuits (See attached) and SemperFi graciously provide his circlet design.
“6DG6GT Magic Amp” (attached) = 5UGB rectifier tube and has no negative feedback and mentioning of weakness in bass response has resonance.
“Low voltage Madness” (attached) = rectifier uses CRC filtered solid state power supply a lot of what is termed as “sag
Mona,
You were the first one to pointing out the R7 was incorrect and should go to ground can you please see attachments and please verify how this should be corected. Then the 12L6 circuit should be pretty good for the 6W6 tube.
I from the schematics now everything should come together except the best option for filtering in the power supply.
I am concerned with time and buying material before I go overseas so I went ahead and purchased Power transformer - AS-1T230 - 100VA 230V TRANSFORMER.
Thanks,
David
To be honest I am one of them not to really look at your schem, there were so many comments on that already. Here are some suggestions from me. The 6W6 will run a tad hot with 180ohms on the cathode. 330ohm a safer try. Also the gridstopper on input tube should go right on the socket pin, and be a bit higher in value in my opinion. (Rstopper=5*1/Gm). Using 25kohm for the plate resistance gets the voltage on plate tcloser to 2/3 of b+, the standard design rule (to take lightly so 20kohm is fine if that's what you got).
In my amp I can swap the 6W6 for a 6V6 or a 6L6 if I so feel, without any mods, so can you. Not optimal I know but they work fine.
In my amp I can swap the 6W6 for a 6V6 or a 6L6 if I so feel, without any mods, so can you. Not optimal I know but they work fine.
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Well isn't that if you have the same factor of plate load for each tube type? For instance use a transformer that gives 4rp for the given triode?
What if you don't have the luxury of buying a new OPT for each tube you want to build with? I just use what I have, and the rp is different per tube type, so the DF and b+ripple varies accordingly.
Ooops. I just realized the value for the cathode resistor (330ohm) is for a triode connected 6W6. Sorry.
For a theoretical speaker with a ruler-flat impedance curve maybe, but for real world speakers it's absolutely a design consideration that should be given serious thought. It's one thing to build amplification for an instrument, but to reproduce music it's a different ballgame. Running pentodes/tetrodes "wide open" gives poor damping and sometimes funky response as the speakers reflected impedance sometimes ends up all over the place. \
Go triode connected and the issue is much lesser and can happily be overlooked.
You guys are right. I'm very lax about these things... Besides for audio I always go triode so don't bother give it much thought.
Speaker dependent yes. A pentode is a current device, gain varies as load Z. Speaker in a box has resonances. So gain will vary as frequency. And D% will be impressively high.😀
OK for your favorite guitar maybe. Won't need an FX box!
Pedal down continuously.
You seem well informed. Could you post a photo of one of your projects along with a description. Always interesting to see what others are doing.🙂
I understand your reluctance do to previous comments – I am sure glad did you look at schem = provided solutions. I learned a couple things from your post. You have partially answered questions that I have not even asked yet. I do really appreciate it.
I have a lot of other things going on now. I have still been making time to reading on the power supply filter, and the NFB (negative feedback) comments from the beginning of the post.
I know nothing building a Tube Hi Fi Amp & very little about electronics. I do tend to jump in over my head. I get held back on Acronyms and trying not to ask too many stupid questions. I try to read and learn first (takes time)then reconfirm with stupid questions. I apologizes for this I do extremely appreciate all the support.