Im am intrigued by using the 6SN7 in a fleawatt amp to drive 32 ohm headphones. I have both SE and PP iron that would work great. The PP iron is a pair of Tomiko iron 5k I purchased a few years ago and they are very small and would fit perfectly on a small chassis (there is no way they are 30 watt transformers though as advertised) and have taps for 4/8/16 ohms. I also have a couple pairs of single ended iron I can use; I am thinking if I went that route I could use 2.5K/8 ohm Edcors on 32ohm headphones for 10k reflected to the tube?
I have a new pair of headphones (hifiman HE-4xx) that can handle a watt. My question is PP or PSE? I am leaning toward PP as I have not built many PP amps.
I have a new pair of headphones (hifiman HE-4xx) that can handle a watt. My question is PP or PSE? I am leaning toward PP as I have not built many PP amps.
Unless your new headphones are Very inefficient, I do not believe your ears can stand 1 Watt with the headphones on your ears.
1 Watt into 32 Ohms is 5.657Vrms, or 8V peak (or 16V peak to peak). It is also 176.8 mArms, or 250mA peak (1/4 Amp peak).
1 Watt is plenty of excess power for most headphones. Happy listening, just be sure to start with the volume turned down.
All I saw about those headphones is 35 Ohms, and 93 dB (93 dB what?).
The difference between equal SPL at the transducer of a speaker SPL at 1 meter (~40 inches) and the same SPL at the transducer of a headphone which is at 0.4 inches is about 40 dB.
That is related to distance. But I do not expect speaker ratings and headphone ratings to be done the same way.
93dB + 40 dB = 133 dB, I hope not.
1 Watt into 32 Ohms is 5.657Vrms, or 8V peak (or 16V peak to peak). It is also 176.8 mArms, or 250mA peak (1/4 Amp peak).
1 Watt is plenty of excess power for most headphones. Happy listening, just be sure to start with the volume turned down.
All I saw about those headphones is 35 Ohms, and 93 dB (93 dB what?).
The difference between equal SPL at the transducer of a speaker SPL at 1 meter (~40 inches) and the same SPL at the transducer of a headphone which is at 0.4 inches is about 40 dB.
That is related to distance. But I do not expect speaker ratings and headphone ratings to be done the same way.
93dB + 40 dB = 133 dB, I hope not.
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I think you understod Wavebourn, just adding my 2ct.
SE OPTs generally have limited inductance because of the air gap. So a SE OPT is a balancing act between enough inductance and sufficient airgap to avoid saturation. So I agree with Wavebourn that a SE OPT optimized for 2k5 will lack Inductance at 10k.
PP OPTs do not require an air gap, so, simply said, they generally have way more inductance than needed - therefore I think that you may have more succes with the Tomiko.
A link to an interstage by Lundahl: same iron, same windings, just a different gap. No gap gives 290H, 10mA 130H and 18mA 100H.
http://www.lundahl.se/wp-content/uploads/datasheets/1660.pdf
In case you have not seen it yet, a very interesting thread for you!
6SN7 push pull flea amplifier project
6SN7 push pull flea amplifier project
At #68 of that thread I posted my build of the amplifier: I still use it almost daily. After your post I connected it for the first time to my 32 ohm headphones. I put a 10 ohm resistor between each output terminals, see the picture attached to this post. It works very well, with plenty of volume. I'm wondering why I didn't put a headphone jack on this amplifier on the first place. The schematic on post #68 of the push pull flea amplifier is still my current one, but now I will increase the filter choke to 10H and the filter capacitors for the 6SL7 tubes, to remove the faint residual hum I still hear on the headphones. By the way, rectifier pins 2 and 8 on that schematic are reversed.
Attachments
I really like your build. I plan on going DC for all the heaters. And will probably do a CLCLC or LCLCLCL. I have some small chokes that would be fantastic for this build and a plethora of power transformers from 500vCT to 700VCT. The aluminum chassis should be here today which I will powder coat "Illusion Cherry"
Can I ask how much plate current you are running on each section.?
Can I ask how much plate current you are running on each section.?
10mA each section of 6SN7; this means 20V on the cathode as stated on the schematic.
I believe that hum from AC filament supply is not a issue on this design, and the simple traditional power supply I built is good enough, it only need a few tweaks. If you want the best possible result, I suggest to go for a solid state regulated power supply both for filaments and for B+. It is cheap and easy at this very low power level. When I built the amplifier I was sceptical about the results so I used free irons recovered from tube radios and I selected a retro look for the chassis to match. Component placement is also substandard compared to my regular builds (it was a very quick build), but this circuit is so uncritical that it works and sounds perfectly anyway. I am tempted to build it again with new quality parts and a better chassis.
I believe that hum from AC filament supply is not a issue on this design, and the simple traditional power supply I built is good enough, it only need a few tweaks. If you want the best possible result, I suggest to go for a solid state regulated power supply both for filaments and for B+. It is cheap and easy at this very low power level. When I built the amplifier I was sceptical about the results so I used free irons recovered from tube radios and I selected a retro look for the chassis to match. Component placement is also substandard compared to my regular builds (it was a very quick build), but this circuit is so uncritical that it works and sounds perfectly anyway. I am tempted to build it again with new quality parts and a better chassis.
Gungnir,
A 1 Watt solid state amp that is rated for 8 Ohms puts out 2.828Vrms.
A 2 Watt solid state amp that is rated for 8 Ohms puts out 4Vrms.
1 Watt from a headphone amp into 32 Ohms is 5.657Vrms.
2.828Vrms or 4Vrms from solid state, versus 5.657Vrms for 1 Watt from your tube amp into your headphone.
As I said in my previous post, you will not need 1 Watt into 32 Ohms.
1/4 Watt or 1/2 Watt from your tube headphone amp will be equivalent to the 1 or 2 Watt solid state 8 Ohm rated amp.
That lower power requirement frees you up to more possibilities, with the 1/2 Watt or 1/4 Watt you need, just more selections of tubes that can do it, and topologies like SE, PP, etc.
A 1 Watt solid state amp that is rated for 8 Ohms puts out 2.828Vrms.
A 2 Watt solid state amp that is rated for 8 Ohms puts out 4Vrms.
1 Watt from a headphone amp into 32 Ohms is 5.657Vrms.
2.828Vrms or 4Vrms from solid state, versus 5.657Vrms for 1 Watt from your tube amp into your headphone.
As I said in my previous post, you will not need 1 Watt into 32 Ohms.
1/4 Watt or 1/2 Watt from your tube headphone amp will be equivalent to the 1 or 2 Watt solid state 8 Ohm rated amp.
That lower power requirement frees you up to more possibilities, with the 1/2 Watt or 1/4 Watt you need, just more selections of tubes that can do it, and topologies like SE, PP, etc.
I solved the hum issue when using the flea power amp with my headphones. Increased the filter choke from 1H to 8H (same 300 ohm DCR) and both preamp filter capacitors from 10uF to 47uF. This eliminated the power supply ripple completely. Exchanged the 6sn7 with a new, less noisy set. There is a little bit of magnetic coupling from the power transformer to the nearest output transformer, but I can't hear it anymore when I put a 10:1 attenuator on the output. The speaker output of the amplifier is now connected to a 7.5 ohm resistor in series with a 1 ohm resistor, the low impedance headphone is across the 1 ohm resistor. Without the attenuator, the volume was already deafening when the volume knob (logarithmic action) was at one third. With the attenuator, I keep it at my normal speaker volume position. I basically only need 0.1W
This is still one of my favorite builds on here, I love it
My original flea amplifier still runs in the garage for workshop use, and is still plenty loud for anything other than drowning out powertool noise
I would recommend looking at some of the later comments and posts by JHstewart in my thread for more "optimised" versions of the flea amplifier. I really want to try the differential front-end on one soon.
I agree that AC heating is plenty fine here.
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This is still one of my favorite builds on here, I love it
My original flea amplifier still runs in the garage for workshop use, and is still plenty loud for anything other than drowning out powertool noise
I would recommend looking at some of the later comments and posts by JHstewart in my thread for more "optimised" versions of the flea amplifier. I really want to try the differential front-end on one soon.
I agree that AC heating is plenty fine here.
Ill check out the later posts. I know AC heating is fine for speaker use, but what about headphones?
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