@ugly_woofer said:
546-BPD2E Mouser # for plug in 12VAC.
The build pdf says to stay with the 500ma because the larger output will over-voltage the circuit. meh ... I'll just order it from Jameco
I ordered a higher current rated one. Not sure I understand the logic as it should just afford some overhead since it isn't outputting higher voltage. Ordered it before the PDF came out. Sigh, yay more stuff to buy.
@ugly_woofer said:
546-BPD2E Mouser # for plug in 12VAC.
The build pdf says to stay with the 500ma because the larger output will over-voltage the circuit. meh ... I'll just order it from Jameco
I ordered a higher current rated one. Not sure I understand the logic as it should just afford some overhead since it isn't outputting higher voltage. Ordered it before the PDF came out. Sigh, yay more stuff to buy.
This is incorrect. Do NOT use the higher current rated one. This will over-voltage the tubes. With the higher current rated wall wart the tube heaters will be running around 7vdc and the B+ will go over 35vdc on each capacitor. This could burn the capacitors out or cause them to physically explode. Please stick with the Jameco 12vac wall wart rated at 500ma!
12V at .5A would be 6watts. Sounds like this kit pulls about that much? Possibly relying on some voltage sag to regulate by drawing it's max rating? I'm just trying to wrap my head around it.
@ugly_woofer said:
546-BPD2E Mouser # for plug in 12VAC.
The build pdf says to stay with the 500ma because the larger output will over-voltage the circuit. meh ... I'll just order it from Jameco
Correct. Do not used the 546-BPD2E from Mouser. The secondary on this unit outputs 12VAC, but is rated at 1.67amps. This will over-voltage this circuit. The little 6J1 PCB, both heaters and B+, only draws about 300ma @ 12vac at its inputs. You need to use the smaller 500ma wall wart because it uses a much thinner gauge wire on the primary and secondary. This, in turn, causes a voltage drop, which keeps the voltage level lower. In other works, the small 500ma transformer is acting as a dropping resistor to keep the voltage levels in check. Do not substitute.
@DrewsBrews said:
Any idea what the input voltage drops down to? I could take that and calculate a resistor to put on the input.
Say 1v drop over 300ma would be 3.3ohm. I think I've got a 10watt 3.3ohm resistor already.
I actually breadboarded this a few days ago with my 12Vac 450ma Radio Shack transformer and it came out to about 1 or 2 ohms of series resistance to get a 0.6v drop on the heater voltages. You could just experiment with 1, 2, and 3 ohm resistors. When you get the heater voltages down to 6.3 volts on each tube you will be good to go. My suggestion of the 500ma wall wart was designed to make it easier for everyone to simply plug the wall wart in and get the right voltages without making more changes. If you do this, you will have to cut the wall wart secondary cable to insert the resistor. Then find a box to house the resistor.
I'll probably just cut the power trace and solder the resistor in. Among other mods (some less necessary than others) I think I'll do now that I am looking at some close up photos of the board.
Now I remember why I hate ordering form Amazon, their packing totally sux. 4 dc breakers and the tube preamp kit thrown into a med size padded envelope. Nothing to keep the heavy breakers from mashing the pins on the tubes or from tearing the end of the envelope out. Only things holding the contents in were a few rubber bands. Grrr....
Guess it's a good thing more tubes are on the way.
@Kornbread said:
The led isn't being used for anything, right? Like biasing or voltage regulation?
... and I suppose since Mouser doesn't have either the d667 or b647, they are nla?
Correct - LEDs are just bling.
From what I gather, the transistors are Chinese clones of something. You can find them on Amazon & eBay. I'll have to do a little hunting to see what they copied.
Looks to be the same circuit but with different trace paths. At first glance the ground appears to be seperated, but having a bit of difficulty with just the front/back photo since the stenciling is covering portions.
@Kornbread said:
The led isn't being used for anything, right? Like biasing or voltage regulation?
... and I suppose since Mouser doesn't have either the d667 or b647, they are nla?
Correct - LEDs are just bling.
From what I gather, the transistors are Chinese clones of something. You can find them on Amazon & eBay. I'll have to do a little hunting to see what they copied.
I remember that fiasco. I didn't quite understand how that circuit was working back then - I might actually be able to trace things out a little better now.
The transistors in this kit are probably fakes, but they work just fine in this application. They aren't being asked to pass much current and not in the audio path.
KSA1013 & KSC2383 are said to be suitable replacements. Both are very common in audio repair circles and available from Mouser.
@jhollander said:
Anyone order the acrylic case for the board?
I was looking at those acrylic cases. They are cheap, but I decided against it because it provides no electromagnetic or RF shielding. A fully exposed PCB is a hum and RF magnet. I searched around for a metal 6J1 preamp case that was the same size and configuration as the acrylic ones, but came up empty. So for my 2nd build I am using an old 8 x 6 x 2" high steel Radio Shack case. I cut two holes in the top to let the tubes stick out. I connected a short wire from the PCB ground trace to a bolt on the bottom of the case. In this way, the metal case will act as an electromagnetic shield but will not carry current for either the power supply or signal ground.
@DrewsBrews said:
Trying to figure out if this is a prebuilt board and the "DIY" part is you putting it in the case. Probably shipping direct from china.
I think you actually have to buy all the components yourself and then solder them. Which would be quite deceiving.
Package Contents:
1* 6J1 tube preamp amplifier board
1* Transparent shell parts
1* Instruction manual
1* Screw package
Note: This is Diy Kits. you need . Only the above package content, other are not included.
@ani_101 said:
That's interestign Bill, this item too has free returns, so there is no risk i guess if it doesn't fit. I'll add it back to the cart
Ani, after reading your post that the 500ma 12vac Jameco wall wart was also available on Amazon, I ordered one from Amazon to see if it would work OK. I got the order today and it works! No problem with the 2.1mm plug spec. I also have a 2.5mm plug from Jamico that I was using to connect a transformer and that plug works very good too. Apparently the jack is designed to accept either size.
I also powered up the 6J1 preamp with this new 500ma 12vac wall wart and all the voltages come out exactly where I wanted them (see pic below). With 120vac from my outlet, the B+ comes out to +30, 0, -30vdc and the heater supply comes out to 6.28vdc. Right on target!
I finished up my 2nd 6J1 build and have a few pics. I found a link to a Marantz font for the front label. Gives the preamp a somewhat distinguished "high end" look. Probably makes it sound better too! I used Mogami mic cable to connect the RCA jacks to the back panel. The outer shield is only connected to ground on one end, so the shield does not carry audio signal current. It only acts as an EMI/RFI shield. Same thing for the chassis ground connection. It is only connected to the chassis at one point. Therefore the chassis will not carry signal or power supply ground currents. It only acts as an EMI/RFI shield.
The RCA and power cables can be easily disconnected to make future mods without desoldering:
Still waiting for mine, I was a dumb dumb and ordered the green board kit. I suspect those are actually shipped direct from China.. Since it is listed as being shipped from California (where the ship ports are) and the USPS tracking number is still stagnent. Probably waiting for the package to arrive in the country.
Comments
I thought the caps were filtering the ripple out so why would it matter?
The build pdf says to stay with the 500ma because the larger output will over-voltage the circuit. meh ... I'll just order it from Jameco
I figured the doubler circuit needed the AC before it gets filtered down to DC. But I don't realy know.
I ordered a higher current rated one. Not sure I understand the logic as it should just afford some overhead since it isn't outputting higher voltage. Ordered it before the PDF came out. Sigh, yay more stuff to buy.
Correct on the AC for the voltage doubler!
Amazon has the Jameco with free Prime shipping-
https://www.amazon.com/Reliapro-ACU120050F4031-Adapter-Transformer-Straight/dp/B00B88637C/ref=sr_1_4?crid=1UY43G8Q6JAFT&keywords=jameco+12v+AC&qid=1705764362&sprefix=jameco+12v+ac,aps,147&sr=8-4
This is incorrect. Do NOT use the higher current rated one. This will over-voltage the tubes. With the higher current rated wall wart the tube heaters will be running around 7vdc and the B+ will go over 35vdc on each capacitor. This could burn the capacitors out or cause them to physically explode. Please stick with the Jameco 12vac wall wart rated at 500ma!
12V at .5A would be 6watts. Sounds like this kit pulls about that much? Possibly relying on some voltage sag to regulate by drawing it's max rating? I'm just trying to wrap my head around it.
Correct. Do not used the 546-BPD2E from Mouser. The secondary on this unit outputs 12VAC, but is rated at 1.67amps. This will over-voltage this circuit. The little 6J1 PCB, both heaters and B+, only draws about 300ma @ 12vac at its inputs. You need to use the smaller 500ma wall wart because it uses a much thinner gauge wire on the primary and secondary. This, in turn, causes a voltage drop, which keeps the voltage level lower. In other works, the small 500ma transformer is acting as a dropping resistor to keep the voltage levels in check. Do not substitute.
Any idea what the input voltage drops down to? I could take that and calculate a resistor to put on the input.
Say 1v drop over 300ma would be 3.3ohm. I think I've got a 10watt 3.3ohm resistor already.
I actually breadboarded this a few days ago with my 12Vac 450ma Radio Shack transformer and it came out to about 1 or 2 ohms of series resistance to get a 0.6v drop on the heater voltages. You could just experiment with 1, 2, and 3 ohm resistors. When you get the heater voltages down to 6.3 volts on each tube you will be good to go. My suggestion of the 500ma wall wart was designed to make it easier for everyone to simply plug the wall wart in and get the right voltages without making more changes. If you do this, you will have to cut the wall wart secondary cable to insert the resistor. Then find a box to house the resistor.
I'll probably just cut the power trace and solder the resistor in. Among other mods (some less necessary than others) I think I'll do now that I am looking at some close up photos of the board.
Seems cleaner this way and leave the wall-wart unmolested.
When will part due of the 'how to for dummies' be penned as I'll be waiting for that to place the Mouser order?
Now I remember why I hate ordering form Amazon, their packing totally sux. 4 dc breakers and the tube preamp kit thrown into a med size padded envelope. Nothing to keep the heavy breakers from mashing the pins on the tubes or from tearing the end of the envelope out. Only things holding the contents in were a few rubber bands. Grrr....
Guess it's a good thing more tubes are on the way.
Anyone order the acrylic case for the board?
The led isn't being used for anything, right? Like biasing or voltage regulation?
... and I suppose since Mouser doesn't have either the d667 or b647, they are nla?
Looks like kenrhodes got the acrylic case judging by his blown cap pic.
I found it down to $8 so I threw it on the order. Don't know if I'll end up using it long term.. but if all the mods fit, It should work for now.
https://amazon.com/dp/B08HCV49ZW?psc=1&ref=ppx_yo2ov_dt_b_product_details
Yeesh, guess I'm kinda glad I ordered the green board kit that ships seperately. Hopefully it is in a box.
Correct - LEDs are just bling.
From what I gather, the transistors are Chinese clones of something. You can find them on Amazon & eBay. I'll have to do a little hunting to see what they copied.
Found this:
https://electronoobs.com/eng_circuitos_tut73.php
Looks to be the same circuit but with different trace paths. At first glance the ground appears to be seperated, but having a bit of difficulty with just the front/back photo since the stenciling is covering portions.
https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=0.9&ucb=80&uce=80&ic=1&tj=150&ft=70&hfe=60&caps=TO92&cf=on
Last time I bought transistors on ebay, it cost me about $100 worth of other parts when they all went up in smoke because of the fake parts.
I remember that fiasco. I didn't quite understand how that circuit was working back then - I might actually be able to trace things out a little better now.
The transistors in this kit are probably fakes, but they work just fine in this application. They aren't being asked to pass much current and not in the audio path.
KSA1013 & KSC2383 are said to be suitable replacements. Both are very common in audio repair circles and available from Mouser.
I was looking at those acrylic cases. They are cheap, but I decided against it because it provides no electromagnetic or RF shielding. A fully exposed PCB is a hum and RF magnet. I searched around for a metal 6J1 preamp case that was the same size and configuration as the acrylic ones, but came up empty. So for my 2nd build I am using an old 8 x 6 x 2" high steel Radio Shack case. I cut two holes in the top to let the tubes stick out. I connected a short wire from the PCB ground trace to a bolt on the bottom of the case. In this way, the metal case will act as an electromagnetic shield but will not carry current for either the power supply or signal ground.
Mouser order placed. Dale 1%, Rubycon, and Wima.
Trying to figure out if this is a prebuilt board and the "DIY" part is you putting it in the case. Probably shipping direct from china.
https://amazon.com/Jteyult-Newest-Amplifier-Headphone-Transparent/dp/B0BWXZ67YH/ref=sr_1_98?crid=8Y3Y85U04C2H&keywords=preamp+tube&qid=1706033022&sprefix=preamp+tube%2Caps%2C128&sr=8-98
I think you actually have to buy all the components yourself and then solder them. Which would be quite deceiving.
Package Contents:
1* 6J1 tube preamp amplifier board
1* Transparent shell parts
1* Instruction manual
1* Screw package
Note: This is Diy Kits. you need . Only the above package content, other are not included.
Yeah, that one is a little sketchy. They show two different boards, one with little ceramic caps and the other with films types standing up on end.
Ani, after reading your post that the 500ma 12vac Jameco wall wart was also available on Amazon, I ordered one from Amazon to see if it would work OK. I got the order today and it works! No problem with the 2.1mm plug spec. I also have a 2.5mm plug from Jamico that I was using to connect a transformer and that plug works very good too. Apparently the jack is designed to accept either size.
I also powered up the 6J1 preamp with this new 500ma 12vac wall wart and all the voltages come out exactly where I wanted them (see pic below). With 120vac from my outlet, the B+ comes out to +30, 0, -30vdc and the heater supply comes out to 6.28vdc. Right on target!
I finished up my 2nd 6J1 build and have a few pics. I found a link to a Marantz font for the front label. Gives the preamp a somewhat distinguished "high end" look. Probably makes it sound better too! I used Mogami mic cable to connect the RCA jacks to the back panel. The outer shield is only connected to ground on one end, so the shield does not carry audio signal current. It only acts as an EMI/RFI shield. Same thing for the chassis ground connection. It is only connected to the chassis at one point. Therefore the chassis will not carry signal or power supply ground currents. It only acts as an EMI/RFI shield.
The RCA and power cables can be easily disconnected to make future mods without desoldering:
That looks nice!
So ... did anyone have parts left over?
Still waiting for mine, I was a dumb dumb and ordered the green board kit. I suspect those are actually shipped direct from China.. Since it is listed as being shipped from California (where the ship ports are) and the USPS tracking number is still stagnent. Probably waiting for the package to arrive in the country.