Hey guys. I've been thinking about trying to make a low cost tube based or hybrid headphone amp for some time. I want to keep the cost down so I can make a few for friends and family. I've been looking into just using a boost converter for B+ and a buck converter for filaments and running it off of an isolated-regulated 12vdc wall wort. Where I'm hanging is exactly how to implement it. I would prefer it to be all tube based but the cheapest output transformers I can find are $20 each. They're Edcor GXSE series transdormers. I'm open to a output transformerless design but haven't found a lot of data on them and the "aikido" designs still require 300ohm headphones do they not? It's highly preferable that it work with standard impedance headphones. If that's not feasible then I would like to use a solid state output section with very low THD so It just passes the sound without adding any of its own flavor. I realize this isn't going to be the best whiz bang unit out there. I'd just like to make "the working man's" amp that anybody could afford. Any suggestions on how I should go about this?
Great sounding and easy and inexpensive to make. SE Class A amp.
These are SS with 2 actives
Pocket version (2x 9v batteries) :
xrk971 Pocket Class A Headamp GB
Desktop version (more power with 12v wallwart to DC-DC converter and cap Mx):
xrk971 Desktop Class A (DCA) Headphone Amp
This is a hybrid with a tube and two actives:
"Estudiante" Hybrid (7370 + MOSFET)
These are SS with 2 actives
Pocket version (2x 9v batteries) :
xrk971 Pocket Class A Headamp GB
Desktop version (more power with 12v wallwart to DC-DC converter and cap Mx):
xrk971 Desktop Class A (DCA) Headphone Amp
This is a hybrid with a tube and two actives:
"Estudiante" Hybrid (7370 + MOSFET)
you said low cost.. then a tube gain stage+fet follower is the way.
already a few examples here
maybe a wire subminis will be better due to price and space 10x 6N16B-VI Double Triode Miniature Tube MELZ Russian SAME DATE 09/1979 NEW | eBay
already a few examples here
maybe a wire subminis will be better due to price and space 10x 6N16B-VI Double Triode Miniature Tube MELZ Russian SAME DATE 09/1979 NEW | eBay
Haha funny how minds think alike.
I suggest 16N6B-V or -VR (I believe the "I" suffix denotes impulse spec, I'm sure I read that somewhere.)
I also have 6P30B and the -R variant, the difference in size alone is not easily missed. I've yet to see how the performance differs.
If you're driving moderate impedance headphones - which I take to be 32 - 64ohms, then you'll probably not need any gain, a unity gain buffer will likely do the job best.
My lingDAC project has a unity gain output buffer based on a high transconductance MOSFET, loaded by a current source. There's a schematic here : lingDAC - cost effective RBCD multibit DAC design and the PCB gerber files are here : lingDAC - cost effective RBCD multibit DAC design. The buffer board is 5*5cm so super-cheap to get PCBs fabbed.
The BOM cost is exceedingly low (single digit dollars).
My lingDAC project has a unity gain output buffer based on a high transconductance MOSFET, loaded by a current source. There's a schematic here : lingDAC - cost effective RBCD multibit DAC design and the PCB gerber files are here : lingDAC - cost effective RBCD multibit DAC design. The buffer board is 5*5cm so super-cheap to get PCBs fabbed.
The BOM cost is exceedingly low (single digit dollars).
Thanks X! Actually they aren't SOT223 rather still SOT23 but they're thermally enhanced somehow so they can dissipate 1W when equipped with a large enough surface area of copper. On the PCB we have dissipation from both sides to aid cool running.
SSM3J327R is the part number - Mouser has them out of stock currently but they say new deliveries will arrive towards the end of October. I'll see if I can come up with suggestions for the ZVN4306.
SSM3J327R is the part number - Mouser has them out of stock currently but they say new deliveries will arrive towards the end of October. I'll see if I can come up with suggestions for the ZVN4306.
Digikey still has stock.
BF862 is eol which is making me mad .
Asus used them in some of their xonar sound cards
Infineon BSP295 looks a jolly close match - lower threshold voltage but slightly more reverse transfer capacitance. Probably higher gm too (I don't believe the gm plot for the ZVN). And Mouser currently has >10k in stock.
BSP295H6327XTSA1 Infineon Technologies | Mouser 香港
Yes the 6P30B-R variant is about 15mm diameter.
Electrode structures are scaled larger too.
Twin anode, rather than a single anode.
Data is very sparse (I've not found curves for this variant specifically, but i have a datasheet in Russian!)
From a glance at characteristic values, it does however look equivalent to the 6P30B. I can't help but think that it would take far more power though
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If I may jump in here, I found that Pete Millet's design using the Nutube by Korg has been a surprise for me. I have tried a switching power supply, linear type, and battery. Each seemed to have their benefit.
I would like to add one more thing. I built the Aikido amp and have used it with a variety of headphones. It drove them all with ease, including my ZMF planers. The sound is way beyond my expectations. I did have a chassis to use that cost me nothing, and a power transformer that was over sized for the job, but again, it was just laying around the shop. Think that I put about $200 into it all.
I would like to add one more thing. I built the Aikido amp and have used it with a variety of headphones. It drove them all with ease, including my ZMF planers. The sound is way beyond my expectations. I did have a chassis to use that cost me nothing, and a power transformer that was over sized for the job, but again, it was just laying around the shop. Think that I put about $200 into it all.
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