I love the enthusiasm around this amp!
I am very pleased to confirm that there will be a ONE TIME run of the Zenductor II BAF edition some time in the not-too-distant future. With holidays and year-end fast approaching, and a lot of other projects on the horizon... it might be a minute. As of now, boards will not be sold individually, and that's unlikely to change. What is planned is a full kit just like at BAF. We're working out further details.
No one need ask when, or for more updates. They'll be released... when we get time. We're planning on providing plenty of advance notice, so that anyone that wants one can get one. 🙂
I am very pleased to confirm that there will be a ONE TIME run of the Zenductor II BAF edition some time in the not-too-distant future. With holidays and year-end fast approaching, and a lot of other projects on the horizon... it might be a minute. As of now, boards will not be sold individually, and that's unlikely to change. What is planned is a full kit just like at BAF. We're working out further details.
No one need ask when, or for more updates. They'll be released... when we get time. We're planning on providing plenty of advance notice, so that anyone that wants one can get one. 🙂
Got to hear the Zenductors @SRMcGee brought home with him. They were running his pair of Elsinores. Very nice sound. Good control over the bass. Sweetly detailed top end. Sounded congested at moments but they aren't his F5 Turbos. There was an oddity in the voicing like the midbass was shelved but couldn't quite figure out what nor why. Otherwise, I was bopping my head the entire time. Next gathering, I want to bring a pair of ACA minis and minmaxes to compare. Good times!
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Zenductor 2 input impedance? I’m looking to put a high *** filter between the BA3 pre-amp and Zenductor 2 mono blocks. The filter capacitor is a function of the amp input impedance. Nelsons article on the first Zenductor gave a range of 8 to 3 Kohm depending on gain (which seems low). Any help on the Zenductor 2 input impedance would be greatly appreciated.
33K in parallel to whatever value 50K trimpot is set during setting procedure
say - 10 to 15K, eyeball
say - 10 to 15K, eyeball
Hmm, I just got around powering them up.... one of the amps only warms (heats!) up on one of the heat sinks... the other heat sink is stone cold. It does settle on it 1.05V bias... I turned the bias down to 0 and the heat sink stays hot.
Q1A is cold, Q1B is hot.
So, I turned it off, let the heatsinks come down to room temp, turned it on and turned the bias down to 0. Heat sinks did not warm up.
I turned the bias up to 0.5V and I felt one heat sink start to warm up. Turned it off then.
Have not plugged in a source or speakers into it.
As I recall, it was "working" at BAF. At least it was putting sound... but I didn't had it on long enough to figure if it had an issue like this. The solder looks OK to me (sure, sure you say!). Being that the transistors are in parallel, could it be that only one was driving even then?
Ideas on troubleshooting it? Maybe poke around R9 and R6? Measure VB1 and VB2? ( as noted in the board layout ).
BTW, could you turn the Build Guide into PDF? A few of the images are not loading.
Thanks
It's late, wife wants drinks, tomorrow is another day. I don't want to be poking after a vodka martini...
Hmmm..
in the schematic, I see R9 and R6 on Q1A, and R10 and R7 on Q1B...
but
on the board layout it looks like R9 and R7 on Q1A and R10 and R6 on Q1B.
Which is it? Looks like R6 and R7 nomenclature is off.
Q1A is cold, Q1B is hot.
So, I turned it off, let the heatsinks come down to room temp, turned it on and turned the bias down to 0. Heat sinks did not warm up.
I turned the bias up to 0.5V and I felt one heat sink start to warm up. Turned it off then.
Have not plugged in a source or speakers into it.
As I recall, it was "working" at BAF. At least it was putting sound... but I didn't had it on long enough to figure if it had an issue like this. The solder looks OK to me (sure, sure you say!). Being that the transistors are in parallel, could it be that only one was driving even then?
Ideas on troubleshooting it? Maybe poke around R9 and R6? Measure VB1 and VB2? ( as noted in the board layout ).
BTW, could you turn the Build Guide into PDF? A few of the images are not loading.
Thanks
It's late, wife wants drinks, tomorrow is another day. I don't want to be poking after a vodka martini...
Hmmm..
in the schematic, I see R9 and R6 on Q1A, and R10 and R7 on Q1B...
but
on the board layout it looks like R9 and R7 on Q1A and R10 and R6 on Q1B.
Which is it? Looks like R6 and R7 nomenclature is off.
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What is the lowest supply voltage that these amps will properly run with? I am not at all concerned about output power, I just want good sound at low volumes. I am hoping that they will run much cooler with low voltage, like maybe 5 volts or lower.
OK, so dinner is taking longer and so is my martini...
There is no voltage across R7 on the board ( that follows Q1A ). Which makes sense....
Compared voltages... with both boards Taking the "negative side" of the transformer as reference... ( this is the one I used as reference when measuring the voltage across the transformer for the bias measurement ).
Q1A drain (*)is 15.7V (bad board) and 15.2V (good board)
Q1A gate is around 4V for both.
Q1A source is 5.5 mV on bad board and 0.25V on good board.
I get continuity between Q1A source and R7... ( 0.05 ohms on bad board... 0.00 on good board ) Using same brand/style meters.
Is the transistor toast?
(*) Excuse my white coat ignorance... by drain I call the middle leg of the physical transistor, by gate I call the leg connected to R9. I got to say I've NEVER paid attention in my whole life to how the little legs of the transistor map to the schematic or the board. I've never had to lay out a board in my life.
There is no voltage across R7 on the board ( that follows Q1A ). Which makes sense....
Compared voltages... with both boards Taking the "negative side" of the transformer as reference... ( this is the one I used as reference when measuring the voltage across the transformer for the bias measurement ).
Q1A drain (*)is 15.7V (bad board) and 15.2V (good board)
Q1A gate is around 4V for both.
Q1A source is 5.5 mV on bad board and 0.25V on good board.
I get continuity between Q1A source and R7... ( 0.05 ohms on bad board... 0.00 on good board ) Using same brand/style meters.
Is the transistor toast?
(*) Excuse my white coat ignorance... by drain I call the middle leg of the physical transistor, by gate I call the leg connected to R9. I got to say I've NEVER paid attention in my whole life to how the little legs of the transistor map to the schematic or the board. I've never had to lay out a board in my life.
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Aw ****!
I think I figured it out.
I mounted the darn transistor BACKWARDs.
Just like initially I mounted the output binding posts upside down...
Yeah, @ra7 I got you... I GOT YOU.... you never figured out someone would do that, huh? That white wall was staring both of us at our faces and we NEVER figured someone could do that...
Well, I did.
OK, tomorrow I'll fix it.
;-D
I think I figured it out.
I mounted the darn transistor BACKWARDs.
Just like initially I mounted the output binding posts upside down...
Yeah, @ra7 I got you... I GOT YOU.... you never figured out someone would do that, huh? That white wall was staring both of us at our faces and we NEVER figured someone could do that...
Well, I did.
OK, tomorrow I'll fix it.
;-D
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It works....
The hardest thing was getting a hold of that nut behind the heatsink... I couldn't remove the heat sink because there's a lot of mass there... dissipating the heat from the iron.... huh?
Anyhow, it runs HOT... at 1.1V bias, the heatsinks are above 65C already.
It sounds fantastic... just driven by my android phone via the headphone jack into a pair of the littlest, cheapest, sacrificial Elac speakers. With a bias of 1.1V.
Well, Nelson, if you're reading this.... well, I'm getting wet alright. It's FUN.
I think screwing it up taught me more than just doing it right to being with. A simple fix, but, it was staring me on the face... I checked out the solder joints, did some resistance measurements, looked at the schematic, looked at the BOM, component layout, poked here and there... and eventually it just hit me on the head... the thing is *** backwards.... Duh....
But, I got to pull out the brand new Weller station I bought last year, in preparation for being retired... I cleaned up the bench I had prepared, also getting ready for my retirement projects.... dang it. It FEELS GOOD. FUN..
THANKS y'all.
Now time to take some measurements ( I can't help it ) and listen some more.
That country music sure sounds purty....
EDIT: with a single layer of heatsinks, in a bias at 1.1 they were running above 65C.. one was in the 70s. When I just stacked ( not glued down nor thermal goo ), the stack temps dropped At a bias of 1.4V, the bottom heatsinks are running in the low 60s and the tops are running in the low 50s. I fully expect the dissipation will be better when I join the heatsinks with goo and glue.
Oh I just received the fan and buck converters from Amazon... the same ones that @AdamThorne is using. I fully expect that I can bring the heat down to the 50s... Because, this is one HOT baby.
The hardest thing was getting a hold of that nut behind the heatsink... I couldn't remove the heat sink because there's a lot of mass there... dissipating the heat from the iron.... huh?
Anyhow, it runs HOT... at 1.1V bias, the heatsinks are above 65C already.
It sounds fantastic... just driven by my android phone via the headphone jack into a pair of the littlest, cheapest, sacrificial Elac speakers. With a bias of 1.1V.
Well, Nelson, if you're reading this.... well, I'm getting wet alright. It's FUN.
I think screwing it up taught me more than just doing it right to being with. A simple fix, but, it was staring me on the face... I checked out the solder joints, did some resistance measurements, looked at the schematic, looked at the BOM, component layout, poked here and there... and eventually it just hit me on the head... the thing is *** backwards.... Duh....
But, I got to pull out the brand new Weller station I bought last year, in preparation for being retired... I cleaned up the bench I had prepared, also getting ready for my retirement projects.... dang it. It FEELS GOOD. FUN..
THANKS y'all.
Now time to take some measurements ( I can't help it ) and listen some more.
That country music sure sounds purty....
EDIT: with a single layer of heatsinks, in a bias at 1.1 they were running above 65C.. one was in the 70s. When I just stacked ( not glued down nor thermal goo ), the stack temps dropped At a bias of 1.4V, the bottom heatsinks are running in the low 60s and the tops are running in the low 50s. I fully expect the dissipation will be better when I join the heatsinks with goo and glue.
Oh I just received the fan and buck converters from Amazon... the same ones that @AdamThorne is using. I fully expect that I can bring the heat down to the 50s... Because, this is one HOT baby.
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The BoM doesn't include the part number, just a "50K potentiometer"... The Bourns brochure makes it look like a 3386. But that has 1 turn.
I can't read the writing on the pot right now....
It looks like the 3299 fits, but I can't clearly see the style of the pins... are they straight in line?
3339P-1-503? It's round but it seems to fit the hole pattern? 4 turns. I think it's a bit shorter but it ought to fit through the board.
Mouser 652-3339P-1-503
I can't read the writing on the pot right now....
It looks like the 3299 fits, but I can't clearly see the style of the pins... are they straight in line?
3339P-1-503? It's round but it seems to fit the hole pattern? 4 turns. I think it's a bit shorter but it ought to fit through the board.
Mouser 652-3339P-1-503
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OK, so right behind me I got the amps warming up the room... pesky little HEATERS they are.
I stacked the heatsinks, "high rise" mode. Still not glued/clamped together. No fan.
Room temp is 22C.
High Rise mode for each amp, bias, top/bottom, top/bottom.
Left amp 1.42V, 49/66, 53/68. Right amp 142V, 56/73, 46/57
Single heatsink ( the Pass Toaster mode )
Left 1.45, 78, 79. Right 1.49V, 86, 70.
GULP.... 86C... yep, I checked it.
BTW, the low value on the Right amp is for the op amp that I had put on backwards. I ought to check the soldering to make sure it's OK.
When I returned to High Rise mode, the bias and temps dropped back. I find it interesting that the bias goes up with temps... could this be a runaway issue? Like, if I turned the bias to 1.5 it might just never come back from a Valhalla Immolation. Is there a Valhalla for Zenductors?
IMHO, I could drop the bias or I could add more cooling. I am fearless.. More cooling on the way.
Hey... maybe I ought to play some music through them? Some Salsa... Ay.. caliente amigos...
I stacked the heatsinks, "high rise" mode. Still not glued/clamped together. No fan.
Room temp is 22C.
High Rise mode for each amp, bias, top/bottom, top/bottom.
Left amp 1.42V, 49/66, 53/68. Right amp 142V, 56/73, 46/57
Single heatsink ( the Pass Toaster mode )
Left 1.45, 78, 79. Right 1.49V, 86, 70.
GULP.... 86C... yep, I checked it.
BTW, the low value on the Right amp is for the op amp that I had put on backwards. I ought to check the soldering to make sure it's OK.
When I returned to High Rise mode, the bias and temps dropped back. I find it interesting that the bias goes up with temps... could this be a runaway issue? Like, if I turned the bias to 1.5 it might just never come back from a Valhalla Immolation. Is there a Valhalla for Zenductors?
IMHO, I could drop the bias or I could add more cooling. I am fearless.. More cooling on the way.
Hey... maybe I ought to play some music through them? Some Salsa... Ay.. caliente amigos...
