I come from the guitar amp world...and I can tell you those two Vox guitar amps are MUCH different...it's not just the tubes. Totally different amps/speakers/cabinets. Also, a lot of guitar amp quality is "feel", not just the sound. And the sound in the room can vary greatly from the sound miked.
But I also liked the nutube amp better. And I have a Korg B1. But I would probably rather own the AC4 (the traditional amp). In fact, I own it's bigger brother.
It's interesting, the Nutube version of the Ibanez Tube Screamer pedal, which is a classic SS pedal...maybe the most famous of it's kind, gets very little respect in the guitar community. Guitarist are a pretty closed minded bunch...and we mostly buy gear in order to emulate classic sounds we've heard on records. Things like the nutube have no reference point to emulate.
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You do know that M.J.’s PO89ZB wall wart PCB was redesigned with mounting holes on the edge (see that forum; post #407)?
Cheers, Pete
Cheers, Pete
I've built the kit and it looks like something's not right. I'm a novice so don't really know where to start looking to find the problem.
-When I turn it on, the Korg glows blue on both sides but brighter on the left.
-When I adjust right trim pot it doesn't change anything.
-Measurements are:
T1=24V
T2=23V
T3=22V
T4=9.18V
T5=0.65V
T7=9.5V (after adjustment with trim pot)
T8=19.7V (doesn't change with turning trim pot)
Any help on where to look would be much appreciated.
-When I turn it on, the Korg glows blue on both sides but brighter on the left.
-When I adjust right trim pot it doesn't change anything.
-Measurements are:
T1=24V
T2=23V
T3=22V
T4=9.18V
T5=0.65V
T7=9.5V (after adjustment with trim pot)
T8=19.7V (doesn't change with turning trim pot)
Any help on where to look would be much appreciated.
First, check and make sure you didn’t accidentally switch the 33.2K resistor with any of the 332K resistors on the right side of the board. Are the color bands of the two 33.2K resistors, right below the 100R resistors (at the top of the board) the same (on both left & right side of the board)?
Here's a picture of the board. Now I know why the instructions said to place the resistors with the values upwards. Is there a photo somewhere of the bare board so I can check against that?
An externally hosted image should be here but it was not working when we last tested it.
https://d17kynu4zpq5hy.cloudfront.net/igi/diyaudio/OUjAB1bEIPHZycZD.large
This is in the instruction manual at:
B1 with Korg Nutube - diyAudio Guides
Good luck. I got a kit sitting right next to me....
This is in the instruction manual at:
B1 with Korg Nutube - diyAudio Guides
Good luck. I got a kit sitting right next to me....
Can you measure a resistor when it's mounted on a board? I didn't think you could.
Looking at the schematics... what is the range of values for T7 when you turn the pot?
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Sometimes (one can get lucky) you can but it’s always a good practice to pull up one leg to measure correctly, so yes, you are correct.
If you think all the resistors (on the troubled side of the board) are in the right spot (yup, always easier to diagnose incorrect resistor placement if you can read values printed on them) get some flux paste and re-flow all the solder joints starting with the resistors. Do one side of each resistor first then come back and do the other side..don’t want to overheat anything. I’d re-flow the jfets on the troublesome side as well. Visually some looked a bit off so I’d start with them first (see picture).
Good luck.
Attachments
I didn't know about the measuring on the board but if they are the same on both sides then it should be OK shouldn't it?
I'll check the soldering and see how I go.
If you can be certain all the resistors are in their right positions, yes. Since the left side works that means all is good there.
Good luck hunting
>>>>>>>>>For those who have already addressed this observation, great. For us who said WTF when looking at the Fairchild transistors and noticed that though they were all J113, we might have noticed that some had KH33 or KH44 written on them as well. Been a little bit since I built the last B1 and noticed this. As I recall, there is no trouble about those numbers being different on some of the transistors, right? Everything else is swell.
No problem. All of them were tested for Vp, so that they would be operating
at Idss where the Gate and Source voltages would be the same on each follower.
This allows for easy measurement of the high impedance Plate voltage of the tube.
And of course you are welcome to use the Toshiba parts....
at Idss where the Gate and Source voltages would be the same on each follower.
This allows for easy measurement of the high impedance Plate voltage of the tube.
And of course you are welcome to use the Toshiba parts....