for your critique
First to 12B4A, I'd do as you suggest; all errors should be tracked down and eliminated, but I haven't the skills.
Here's a shot of my finished Aleph J, shown dominating the very old school Crown DC300A doing service as a sub woofer amp 🙂
It is a very impressive sounding amp. I am amazed. I could not have done this without so much friendly help. Thank you all!
This Aleph J was done on a very tight budget with chassis parts I compiled from the scrapyard. I took chances with the layout trying to make sure the heatsinks I constructed from 18 tiny sinks (probably from broken computers) got enough air around them to keep the amp cool. The fins total about 8x10 inches per side. The black heatsinks you see on the inner body (also from the scrapyard) are there to assist the diode cooling; that saved $25 over the ones that fit on the psu boards. Even the wire was military surplus.
I ran it hard the other night: 4 hours driving 4 Ohm (KEF 104/2) speakers with a feed straight out of the CD player (a recapped Goodwill find - Adcom GCD-575). It still passed the 5 second test for chassis temperature.
So I post for you critique my Aleph J ("J" for junkyard construction in this case) perhaps ugly but definitely beautiful in how it makes music. I am truly thankful for your help (especially the benevolent NP) in this my first SS amp build.
First to 12B4A, I'd do as you suggest; all errors should be tracked down and eliminated, but I haven't the skills.
Here's a shot of my finished Aleph J, shown dominating the very old school Crown DC300A doing service as a sub woofer amp 🙂
It is a very impressive sounding amp. I am amazed. I could not have done this without so much friendly help. Thank you all!
This Aleph J was done on a very tight budget with chassis parts I compiled from the scrapyard. I took chances with the layout trying to make sure the heatsinks I constructed from 18 tiny sinks (probably from broken computers) got enough air around them to keep the amp cool. The fins total about 8x10 inches per side. The black heatsinks you see on the inner body (also from the scrapyard) are there to assist the diode cooling; that saved $25 over the ones that fit on the psu boards. Even the wire was military surplus.
I ran it hard the other night: 4 hours driving 4 Ohm (KEF 104/2) speakers with a feed straight out of the CD player (a recapped Goodwill find - Adcom GCD-575). It still passed the 5 second test for chassis temperature.
So I post for you critique my Aleph J ("J" for junkyard construction in this case) perhaps ugly but definitely beautiful in how it makes music. I am truly thankful for your help (especially the benevolent NP) in this my first SS amp build.
Attachments
transformers
What kind of transformers are you using? Since you are driving 4ohm speakers I was wondering how much current are your transfos available VA?
Been listening the last few days to a recently completed Aleph J. I must say that I am very impressed.
I’m using it to drive Maggies and thought the combo would be power starved. It’s not. Note that I have SMGa’s which are relatively efficient (89-90db). No trouble filling my pretty large listening room with beautiful, expressive music. Paralyzing. I didn’t expect this.
In fact, I only built these because I had a 4U and PS ready to build out a second BA-3/F4. 6L6’s kit made it too easy to try the Aleph “for a while”. (Thanks so much, Jim!). I have been using it balanced.
I had spent the past few weeks listening to the BA-3/F4 and was very happy with the sound. It also has more than enough power for the Maggies. The low end (even on the bass shy SMGa’s) is truly spectacular. Maybe overall a touch sterile. I have been running the BA-3 off the amp’s PS and driving it single ended so there is clearly room for improvement.
I must say that I easily prefer the Aleph. I am making a Salas shunt for the BA-3. Maybe that will level the playing field.
Somehow, though, I doubt that I will change my mind. I really love the Aleph. Thanks to everyone responsible for it. Nelson too!
Build is standard. 300 VA Plitron. Amp is very quiet. No turn-on noise. Very slight thump on turn-off.
I have noticed that the bias drops as the amp warms. I need to set the bias at about 440mV cold to end up at 400 when warmed. Is this normal?
I’m using it to drive Maggies and thought the combo would be power starved. It’s not. Note that I have SMGa’s which are relatively efficient (89-90db). No trouble filling my pretty large listening room with beautiful, expressive music. Paralyzing. I didn’t expect this.
In fact, I only built these because I had a 4U and PS ready to build out a second BA-3/F4. 6L6’s kit made it too easy to try the Aleph “for a while”. (Thanks so much, Jim!). I have been using it balanced.
I had spent the past few weeks listening to the BA-3/F4 and was very happy with the sound. It also has more than enough power for the Maggies. The low end (even on the bass shy SMGa’s) is truly spectacular. Maybe overall a touch sterile. I have been running the BA-3 off the amp’s PS and driving it single ended so there is clearly room for improvement.
I must say that I easily prefer the Aleph. I am making a Salas shunt for the BA-3. Maybe that will level the playing field.
Somehow, though, I doubt that I will change my mind. I really love the Aleph. Thanks to everyone responsible for it. Nelson too!
Build is standard. 300 VA Plitron. Amp is very quiet. No turn-on noise. Very slight thump on turn-off.
I have noticed that the bias drops as the amp warms. I need to set the bias at about 440mV cold to end up at 400 when warmed. Is this normal?
MMGer checking in here. Maggies are resistive (over-damped), low-drama impedance curve speakers and as long as one's listening is 90-95db then one can use a lot of different low DF amps in the 10-20 watt range. There are parts of the "power-hungry maggies" meme that are mythical. It's odd to read reviews about them where the reviewer says they are the easiest loads to drive but a few sentences later recommends a 500watt amp with a df >100. Maggies are a nice, clear window for experiencing the Aleph J character.
What are these called?
12B4A - I like the look of your build, and it is showing some of the same issues I will have with the Aleph J in the 5U chassis. A small question, what are the blade connectors soldered to the board called? I have tried searching for blade and snap on connectors, but cant seem to find one that will solder into the board like you have done here.
Thanks in advance.
NM - searched for "tab terminal" and they popped up.
12B4A - I like the look of your build, and it is showing some of the same issues I will have with the Aleph J in the 5U chassis. A small question, what are the blade connectors soldered to the board called? I have tried searching for blade and snap on connectors, but cant seem to find one that will solder into the board like you have done here.
Thanks in advance.
NM - searched for "tab terminal" and they popped up.
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Thanks Lehmanhill! I tried to make the best of the parts I found.😱 It really does remind me of that building (Shapiro Hall) on Wayne State's campus. Funny how that has stayed with me all these years.😉
As my J is running with 0.54V across the source resistors do I need to increase or lower the value of the 68k1 resistor to drop it to 0.4V.ie can I use a trimmer in series with that resistor to increase the value or do I need to remove the resistor and replace with a link and then solder in a 100k trimmer?
Advises please.
Advises please.
Marra -
Most important question, how hot are your heatsinks? And the transistors? If they are dealing with the heat, there's no pressing need to reduce the bias.
Next question - do you have zero (or very low) DC offset?
And lastly, do you have R27 vertical jumpered or does that have the resistor? And then what is in R27 horizontal?
Most important question, how hot are your heatsinks? And the transistors? If they are dealing with the heat, there's no pressing need to reduce the bias.
Next question - do you have zero (or very low) DC offset?
And lastly, do you have R27 vertical jumpered or does that have the resistor? And then what is in R27 horizontal?
The sinks are running at 45C with the mosfets about 6/7 degrees higher.Offset settles at a couple of mv.
R27 is vertical with a link across the trimmer position hence my query as I can easily instal a trimmer but would have to strip things down to unsolder the resistor.The amp does sound good as is so am I whittling over nothing as Nelson often post "run them hard".
R27 is vertical with a link across the trimmer position hence my query as I can easily instal a trimmer but would have to strip things down to unsolder the resistor.The amp does sound good as is so am I whittling over nothing as Nelson often post "run them hard".
Your temperature is fine. Keep it as-is and get out a stack of your favourite records!
Congratulations!
Congratulations!
Are these appropriate diode bridges or is there a better alternative (within Mouser)?
GBPC3506 Fairchild Semiconductor | Mouser
Also, can someone point me to the solder tabs that screw down to the terminal blocks for attaching the trafo wires? I like the look of those from the build pics.
GBPC3506 Fairchild Semiconductor | Mouser
Also, can someone point me to the solder tabs that screw down to the terminal blocks for attaching the trafo wires? I like the look of those from the build pics.
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I get those from radio shack. I'm sure that Mouser has them, but I have no idea what they are officially called.
R3, C1??
OK, here is an off the wall question for you.
I've always been a little uncomfortable with part of the Aleph J layout. It has always seemed a little weird to have C1 and C5 effectively in series. I know they don't exactly function that way, but it has always seemed unusual not to have some other impedance between two caps.
The way I understand R3 and C1 is that they form a high pass filter for the input that blocks DC from getting into the amp. It shouldn't really matter if the order from the input is R3 then C1 or C1 then R3.
The board is definitely on the tight side for C1. There are lots of good caps that one might like to use that don't fit or don't fit well in the current space for C1. Switching R3 and C1 might let you put a jumper in where C1 currently lays, leave R3 in it's current location, and mount a larger C1 off board and effectively swapped order with R3.
Has anyone tried swapping R3 and C1? Am I missing something in the theory or design that says I shouldn't try the swap?
OK, here is an off the wall question for you.
I've always been a little uncomfortable with part of the Aleph J layout. It has always seemed a little weird to have C1 and C5 effectively in series. I know they don't exactly function that way, but it has always seemed unusual not to have some other impedance between two caps.
The way I understand R3 and C1 is that they form a high pass filter for the input that blocks DC from getting into the amp. It shouldn't really matter if the order from the input is R3 then C1 or C1 then R3.
The board is definitely on the tight side for C1. There are lots of good caps that one might like to use that don't fit or don't fit well in the current space for C1. Switching R3 and C1 might let you put a jumper in where C1 currently lays, leave R3 in it's current location, and mount a larger C1 off board and effectively swapped order with R3.
Has anyone tried swapping R3 and C1? Am I missing something in the theory or design that says I shouldn't try the swap?
C1 and C5 in series ........ irrelevant issue , or non issue at all
swapping places of R3 and C1 - yes , why not ; electrically also irrelevant
swapping places of R3 and C1 - yes , why not ; electrically also irrelevant