Btw
The sound is excellent with the oval fullrange spakers. I‘m very happy and many more thanks to the creator of this wonderful amp!!!
The sound is excellent with the oval fullrange spakers. I‘m very happy and many more thanks to the creator of this wonderful amp!!!
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Indeed it does look very nice, and while the temperatures of the FETs might not be excessive in that configuration, I'd guess that the electrolytic caps are going to be living in a much warmer environment than they do in the non-inverted configuration.
I think there is something elegantly efficient in Nelson's design with the 4 heat-producing FETs and their heatsinks at the outside corners. This ensures, IMO, that once upward convection of the surrounding air starts, it carries most of that heat up and out, with the more interior parts of the board will be spared from much of the heat from the FETs.
I think there is something elegantly efficient in Nelson's design with the 4 heat-producing FETs and their heatsinks at the outside corners. This ensures, IMO, that once upward convection of the surrounding air starts, it carries most of that heat up and out, with the more interior parts of the board will be spared from much of the heat from the FETs.
There is the standard power switch only, with power on to the left and the sound remains a short time after switching off.
Sorry, I'm not yet familiar with H2/H3 selector. Do you mean a switch for jumper in/out? Would keep this point for a further modification.
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Thank you for information. Will take care about any base jumpers and will check once if it makes a difference soundwise with jumpers out and using B1K instead.
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Every time I see pictures of stuffed pcb boards I'm admiring how you do it! I'm stuffing my boards, and no matter how often I try, whenever I turn them upside down, all components come off! Do you use some sort of glue? 🤡
Haha. But jokes aside, working jumpers don’t fall out even if upside down. If they did, they would not make sufficient contact to uphold their function anyways. Just look at computer PCB’s from the PCI age. Usually never a problem.
Hi everyone, just starting on this amp after loving the ACA and going full-bore on the Tungsten mods on the premium parts thread.
Just double checking the BOM as my kit is missing two of the 6.8k resistors and two of the 221k resistors, but does include two 22k resistors and two 200k resistors.... have their been any value changes or substitutions at R3 or R4? or am I just missing and/or have incorrect parts in my completion kit?
Thanks!
Just double checking the BOM as my kit is missing two of the 6.8k resistors and two of the 221k resistors, but does include two 22k resistors and two 200k resistors.... have their been any value changes or substitutions at R3 or R4? or am I just missing and/or have incorrect parts in my completion kit?
Thanks!
Looking at the schematic, if you use the 22k as R4 and the 200k as R2, that will give the equivalent voltage at the JFET gates. So the circuit will be equivalent.
It was raining today so decided to crack-on and build my mini. When I powered it up with all (2k but not Bournes) pots turned counterclockwise I could smell heat and then smoke. Switched-off and did some checks but could not find anything obvious, and assuming something expensive had failed, decided to start again with the pots fully clockwise. Surprisingly, no heat or smoke and then proceeded to initially set bias and the mid point with some success. Will try final set-up tomorrow. Any ideas? Thanks.
If bias can be adjusted to a level where it exceeds the power limit of e.g. source resistors then this could be the reason.
You don't know from which components the smoke came from? 🙂
You don't know from which components the smoke came from? 🙂
Low ohm resistor I think - had to act quickly. Heatsink on one 9540 also hot but bias should have been at its lowest with pots counterclockwise, as per instructions (double checked both).
Next Try ...
@Mark Johnson @Nelson Pass (M occurs N ;-) )
many thanks for for these nice toys (Filter / AMP)!
What should it say ...
only with one filter from MJ I had the feeling to hear a change but was not sure.
Now I have test two filters in series, first I heard completely without filter and then with both.
First, with less details and now with both both filters bring in my chain is more clear treble and a little more control to the bass (i think).
Other chain ... any other results. ;-)
P.S.: I don’t know why …..
@Mark Johnson @Nelson Pass (M occurs N ;-) )
many thanks for for these nice toys (Filter / AMP)!
What should it say ...
only with one filter from MJ I had the feeling to hear a change but was not sure.
Now I have test two filters in series, first I heard completely without filter and then with both.
First, with less details and now with both both filters bring in my chain is more clear treble and a little more control to the bass (i think).
Other chain ... any other results. ;-)
P.S.: I don’t know why …..
Is your pot actuallt CW or is it potentially CCW? Lift the pot and check.
Then begin finding out where the smoke came from. I like to fire up amps with the pots in the mid position. Less danger of instentaneous blowup. Of course, a DMM across source resistors to get fair warning of excess current draw is also smart.
Thanks. The only logical cause is the pots are working in reverse to those as listed in the BOM (which will be a new one for me). Will report back tomorrow when I finalise the trimming and hopefully play some music.
Thanks! I found an updated BOM in the site which reflected this change.
I am starting the bias process, between GND and VO I am getting about 11.8 with the trimpots counterclockwise at 0, and I am getting no voltage across VB. Ideas? Are there easier instructions than in the Pass Article?
I am starting the bias process, between GND and VO I am getting about 11.8 with the trimpots counterclockwise at 0, and I am getting no voltage across VB. Ideas? Are there easier instructions than in the Pass Article?