Coalscuttle, you may have finished the main system, but what about the systems for the other rooms in the house? 😉
Well...
I'm your stereotypical (yuk, yuk) reclusive starving artist, and there are no other rooms in the house.
I'm your stereotypical (yuk, yuk) reclusive starving artist, and there are no other rooms in the house.
AAK
I have a question about the Bourns pot R22 on the schematic it is 1K Ohm but on your BOM it is 100 Ohms. Your Mouser number is also 100 Ohms so you are consistent here.
Could you verify?
Thank you
I have a question about the Bourns pot R22 on the schematic it is 1K Ohm but on your BOM it is 100 Ohms. Your Mouser number is also 100 Ohms so you are consistent here.
Could you verify?
Thank you
Re: Well...
Not even a toilet? 😀
al/would like to be a starving artist as it might make him more interesting to women...
Colescuttle said:
Not even a toilet? 😀
al/would like to be a starving artist as it might make him more interesting to women...
Vr22 is not 100r. the range of adjustment would be far too low.
You may get away with 500r but the restricted range would require some adjustment of the other resistors in the Vbe string.
You may get away with 500r but the restricted range would require some adjustment of the other resistors in the Vbe string.
Colescuttle
Very nice amps you have constructed. Do the fans run all the time? How is the bass output of your amp? I have been reading where this amp SEEMS to produce far more power than it's 60 watts rating. I am still ordering parts for my 2. Can not quite decide on the enclosure or to go mono. Nice work. Tad
Very nice amps you have constructed. Do the fans run all the time? How is the bass output of your amp? I have been reading where this amp SEEMS to produce far more power than it's 60 watts rating. I am still ordering parts for my 2. Can not quite decide on the enclosure or to go mono. Nice work. Tad
AndrewT said:
Checking parts orders: I was originally concerned as I was using MikeB schematic but when I saw the difference re AAK BOM I found AAK circuit schematic. This agrees with his BOM
Please notice that the rest of that resistor network HAS been changed, so until clearly stated otherwise I am going to assume all is correct.
Regards,
Ooops !
I am a little bit confused by all these BOM's and schematics laying around ...
A web site or blog may help, but I've no time for setting this up as for you I believe 😀
To summarize my troubles (restricted to AAK brew with +/-50V rails):
1) Which value for C14 : 10pF or 3.3pF ?
2) Which value for R27,28 : 0.22R or 0.15R ?
Thick metal (eg MPC71) or non inductive wirewound (eg Mills) ?
3) Which value for R22 trimmer : 100R, 500R, you name it ?
BTW, which wiring for this trimmer ?
I guess : pin 1 linked to R24 and pin 2 (wiper) and pin 3 together
or another layout ?
TIA !
PS: any clue about wiring output transistors apart ?
I am a little bit confused by all these BOM's and schematics laying around ...
A web site or blog may help, but I've no time for setting this up as for you I believe 😀
To summarize my troubles (restricted to AAK brew with +/-50V rails):
1) Which value for C14 : 10pF or 3.3pF ?
2) Which value for R27,28 : 0.22R or 0.15R ?
Thick metal (eg MPC71) or non inductive wirewound (eg Mills) ?
3) Which value for R22 trimmer : 100R, 500R, you name it ?
BTW, which wiring for this trimmer ?
I guess : pin 1 linked to R24 and pin 2 (wiper) and pin 3 together
or another layout ?
TIA !
PS: any clue about wiring output transistors apart ?
hd38 said:
the trimmer is only a variable resistor in this circuit not a voltage divider so it matters not. i.e. essentially there are only 2 ends in the circuit for resistor.
What do you mean about wiring transistors apart?
AAK's BOM calls up R23=1k0, R24=316r, VR22=100r.
if these are the Vbe multiplier resistor string, then
max Vbe voltage is 1000/316+=4.16*Vbe.
Min Vbe using 100r pot is 1000/[316+100]+1=3.4*Vbe.
100r is too small with these values.
R23 is a bit small or alternatively R24 is a bit big since 4.16times is a little low for setting up the output bias if the ratio of Vbe voltages works against you.
I would reduce R24 to 240r and make VR22=500r, giving an adjustment range of 2.35*Vbe to 5.2*Vbe.
if these are the Vbe multiplier resistor string, then
max Vbe voltage is 1000/316+=4.16*Vbe.
Min Vbe using 100r pot is 1000/[316+100]+1=3.4*Vbe.
100r is too small with these values.
R23 is a bit small or alternatively R24 is a bit big since 4.16times is a little low for setting up the output bias if the ratio of Vbe voltages works against you.
I would reduce R24 to 240r and make VR22=500r, giving an adjustment range of 2.35*Vbe to 5.2*Vbe.
Re: Colescuttle
Thanks. I'm ecstatic with the way they sound, and the pictures don't really do them justice. They turned more attractive (on the outside) than they should have, given all the things I did not anticipate when I was designing them and putting them together. Serendipity, I guess.
The fans are connected to their own 12V wall warts, which are in turn plugged into a switched power strip hidden behind the curtain that hides all the wiring and the two power conditioners. All I need do is hit the power strip switch whenever I want the fans on or off.
The amps have a much wider bandwidth than others I have owned, and enable the little Fostex drivers to generate such strong and well-controlled bass that there's no need for a sub. In fact, some recordings seem to incorporate subsonic signals that the amps reproduce faithfully, causing the drivers to far exceed their excursion parameters. Before playing those recordings again I'm going to re-record them and filter out the stuff under 20Hz with my GoldWave editor. I don't want to have to dodge projectile cones.
The one thing I didn't anticipate, given all the NFB, is how well the speakers image with these amps. I guess it's true that it's not NFB that's bad, just how it's commonly used. Way to go, Mike. I have absolutely no desire to go back to tubes.
George
tryonziess said:
Thanks. I'm ecstatic with the way they sound, and the pictures don't really do them justice. They turned more attractive (on the outside) than they should have, given all the things I did not anticipate when I was designing them and putting them together. Serendipity, I guess.
The fans are connected to their own 12V wall warts, which are in turn plugged into a switched power strip hidden behind the curtain that hides all the wiring and the two power conditioners. All I need do is hit the power strip switch whenever I want the fans on or off.
The amps have a much wider bandwidth than others I have owned, and enable the little Fostex drivers to generate such strong and well-controlled bass that there's no need for a sub. In fact, some recordings seem to incorporate subsonic signals that the amps reproduce faithfully, causing the drivers to far exceed their excursion parameters. Before playing those recordings again I'm going to re-record them and filter out the stuff under 20Hz with my GoldWave editor. I don't want to have to dodge projectile cones.
The one thing I didn't anticipate, given all the NFB, is how well the speakers image with these amps. I guess it's true that it's not NFB that's bad, just how it's commonly used. Way to go, Mike. I have absolutely no desire to go back to tubes.
George
hd38 said:
I compromised with 5 pF at C14, and my amps appear to be dead stable, no matter what I throw at them.
George
AndrewT said:
Good Point.
MikeB had R23=2k R22=1k R24=500 giving ratios
2000/500 +1=5 => 2000/(1000=500) +1 =2.33
I went thru th maths but I ignored the +1 factor, so for AAK to MikeB and got similar results.
Thanks,
Hi Sheldon,
For the vbe multiplier you could use MikeB's part selection for R23,R22,R24 and it would work fine with my board, and will allow a wider range of bias control than the values i selected.
The values for the Vbe multiplier that I selected allows for an adjustable range using R22 of between 0mv to about 50mv accross R27 and R28 with +/50V rails. That translates about 0ma to about 62.5ma across each resistor. If you use +/-36V rails you'll need drop R24 to about 240.
If you use MikeB's part values for R23,R22,R24 just make sure that R22 is set to it's lowest bias setting to prevent excessive current on the output devices when you first power up.
Al
For the vbe multiplier you could use MikeB's part selection for R23,R22,R24 and it would work fine with my board, and will allow a wider range of bias control than the values i selected.
The values for the Vbe multiplier that I selected allows for an adjustable range using R22 of between 0mv to about 50mv accross R27 and R28 with +/50V rails. That translates about 0ma to about 62.5ma across each resistor. If you use +/-36V rails you'll need drop R24 to about 240.
If you use MikeB's part values for R23,R22,R24 just make sure that R22 is set to it's lowest bias setting to prevent excessive current on the output devices when you first power up.
Al