BDHM and StellarElephant - are you guys going for the GB? We would have critical mass with your participation.
The SMT version is beyond the limits of my compromised manual dexterity alas. But if it means the difference between the GB going ahead or not, then I'll happily sign up
Pocket Class A GB Order List:
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
It looks like we have enough people now. As the layout artist it would be nice if you got to build one too. But I understand. Funny some people can do SMT but not through hole!
I will keep it open for a few more days to see if there might be more interest so we don't leave anyone out for the GB. Also, it is Lunar New Year in China and none of the Fab houses are droning anyway until after Feb 3.
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What is the gain of this amp stage ?.
Has anybody tried using this design as a line level buffer stage ?.
Dan.
Has anybody tried using this design as a line level buffer stage ?.
Dan.
Gain is approx 3x. Yes, it works fantastic as line level preamp. No noise or hiss. Beware though that design has poor PSRR so your PSU needs to be low ripple (cap Mx or shunt) or use batteries.
I started a GB thread over in the GB forum to keep track of just the Pocket Class A amp GB better as this thread has several other amps discussed.
http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb.html#post4966596
You can continue to use the GB list in this thread if preferred and I will merge all requests later.
http://www.diyaudio.com/forums/group-buys/302859-xrk971-pocket-class-headamp-gb.html#post4966596
You can continue to use the GB list in this thread if preferred and I will merge all requests later.
What is the plan for cooling the MOSFET in the through-hole version? If the SPICE model is correct, you have around 600mW going through the ZVN, so you are looking at nearly 80C rise above ambient with the TO-92 part. That sort of heat through a tiny component makes me uncomfortable. There are TO-92 heatsinks, but are there any which are Altoids tin compatible?
I think you can make your own from sheet aluminum heat shrinked to flat face then attach aluminum plate to radiate to lid.
But, why not use the SMT version - it's huge and easy to solder.
I bought some of these to try on TO-92 packages:
http://www.mouser.com/Search/Produc...000Gvirtualkey53210000virtualkey532-575200B00
obviously they add a bit of height, but there are creative ways to deal with that depending on the location on board, etc.
http://www.mouser.com/Search/Produc...000Gvirtualkey53210000virtualkey532-575200B00
obviously they add a bit of height, but there are creative ways to deal with that depending on the location on board, etc.
BOM
Below items are all available from Mouser (circa $20)
Description Part No Qnty
n-channel power MOSFETs ZVN4306GTA 2
n junction JFET BF862 771-BF862-T/R 2
Panasonic OSCON 390uF 20v output caps 20SEPF390M 2
Output cap bypass WIMA 1uF MKS caps MKS2C041001F00KSSD 2
Input bypass Wima 2.2uF MKS caps MKS2B042201F00JSSD 2
Panasonic OSCON 100uF 25v rail caps 20SEP100MX 2
Switchcraft 3.5mm stereo jacks 35RAPC4BV4 2
Alps stereo pot with power switch RK0971221Z05 1
Plus you will need the following 0805 1% metal thin film SMT resistors (qnty):
33R(2), 47R(2), 270R(12), 1k(2), 15k(1), 47k(2), 100k(2), and qnty 4 x 100nF X7R 0812 MLCC bypass caps, and basic 3mm red or green LED.
Below items are all available from Mouser (circa $20)
Description Part No Qnty
n-channel power MOSFETs ZVN4306GTA 2
n junction JFET BF862 771-BF862-T/R 2
Panasonic OSCON 390uF 20v output caps 20SEPF390M 2
Output cap bypass WIMA 1uF MKS caps MKS2C041001F00KSSD 2
Input bypass Wima 2.2uF MKS caps MKS2B042201F00JSSD 2
Panasonic OSCON 100uF 25v rail caps 20SEP100MX 2
Switchcraft 3.5mm stereo jacks 35RAPC4BV4 2
Alps stereo pot with power switch RK0971221Z05 1
Plus you will need the following 0805 1% metal thin film SMT resistors (qnty):
33R(2), 47R(2), 270R(12), 1k(2), 15k(1), 47k(2), 100k(2), and qnty 4 x 100nF X7R 0812 MLCC bypass caps, and basic 3mm red or green LED.
So I'm a little confused by the statement above. I'm probably betraying my ignorance here, but I thought you meant that this one board could be used for BOTH the SMT or through-hole versions, depending on which side was used, lol.
Just to confirm, is this current group buy is for an all SMT board? To be honest, I really don't mind if this is the case, since I have zero experience with either of these soldering methods (I've only done point-to-point before) and you say that this size SMT is easy, so I'm still in either way.
Another bonus with SMT version is that the components will be on top of the board and visible when the tin is opened, right? I like the idea of being able to show off my handiwork, even if my soldering will look amateurish 😛
SMT is on one side and through hole parts (WIMA bypass caps, main coupling caps, power rail caps, pot, 3.5mm jack, LED) are on the other side. When you open the tin, the SMT side is facing up and the through hole side is facing down (not visible). It's done this way to give best clearance for knobs and jacks so to not interfere with lid closing. Also, lets the hot SMT side breathe easier when opening lid. It will look sort of like my hand etched build. It also keeps the through hole parts away from the rather hot running Class A business side (the MOSFETs and the eight 270R resistors are dissipating about 2W total.) Overall, it's the best use of vertical space - sort of like a two story house vs a one story house.
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Got it. Thanks for the clarification! I'll update the Head-Fi thread to let folks know the group buy will be open a few more days.