Thanks, I had a feeling that might be me making **** up. 🙂
Any further insights that I could add? I'd love to have a better understanding of what exactly the first gain stage does.
Any further insights that I could add? I'd love to have a better understanding of what exactly the first gain stage does.
Yo, I've often read "x gain stages" and not even known what that means. I understand what gain means in this context, but define "stage."
And, is there a minimum or max to the number of stages? What is a stage? Is there an advantage to more or less? I suspect answering these means getting out of the Noob world... (but I still want to know)
And, is there a minimum or max to the number of stages? What is a stage? Is there an advantage to more or less? I suspect answering these means getting out of the Noob world... (but I still want to know)
I should've just done an adapter for mine and gone XLR only. Instead, I hacked into my 4U black steel case and made these uneven ugly holes that are larger than the Neutrik plates can cover. I'm a newb dumb@***...
Yes, I need and plan to use both, separately. It's complicated. But here's why I didn't. I currently run an Emotiva XSP-1 preamp and my other amp is an Emotiva XPA-2 g2 (A/B). The XLR is 3dB higher gain, even with an adapter. I feared that that would be the same here.
I use XLR from pre to AJ for my Altec 846u.
I built the AJ to power the tweeters in my refurbished ESS Transar. This is a crazy stupid speaker using the Heil AMT and a mad-scientist, Oskar Heil designed vertical-pod array mid-frequency driver on an open baffle. I'm using a MiniDSP for crossover, and it's single-ended only. The Emo runs lows, and I planned the AJ for highs. Hence needing both SE inputs. Should've just gotten an adapter...
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Reading the blog post. Some very good info, but I don't actually know what this means:
"Before handling transistors, it's a good idea to ground yourself to eliminate any static electricity. Just touch something that is properly grounded."
Emphasis mine. What are things that are "properly grounded?" How does one ground her/himself? <legit questions. I don't actually know.
"Before handling transistors, it's a good idea to ground yourself to eliminate any static electricity. Just touch something that is properly grounded."
Emphasis mine. What are things that are "properly grounded?" How does one ground her/himself? <legit questions. I don't actually know.
Like, the watertap in your house, or the case of a connected amplifier (if it has a 3. wire for ground), or anything that is conductive and connected to earth)
You do that to make sure you aren’t unloading a static spark which would destroy those parts)
You do that to make sure you aren’t unloading a static spark which would destroy those parts)
Thanks for reading and for the feedback. I'll admit to a bit of fudging there, because despite a lot of Googling, I don't actually know myself!
So the industrial "best practice" is to get a wrist ground strap, as well as an antistatic mat. But based on my research on this forum, it seems that very nearly no one does that.
In the DIY personal computer world, people seem to handle this by touching the unpainted parts of the PC chassis. That doesn't help us much.
Since the idea is to dissipate any static charge, my practice has been to touch a bunch of metal things (kitchen faucet, door knobs, laptop, other amps), hoping at least one is properly grounded. The center screw in most wall sockets is also supposed to be connected to earth ground. But I must admit, I'm not sure I've succeeded.
In short, I would have given more concrete guidance, if I were confident I knew what that would be!
Grab the end of an iron rod buried 2 ft in the ground? Since you drain caps by placing a resistor across the terminals can you drain a captive static charge by grabbing both ends of a resistor? How about soldering a ground strap to your toe nail?
OK, next post up in the noobs guide:
Building: Amp Boards on Heat Sinks
I'm still trying to figure out what wire to recommend for the board to input jack connection (something that n00bs can easily and reliably order), so I've left the input wires for a future post, where I will also address the RCA vs. XLR options.
As usual, I'd appreciate it if y'all would check my work and provide any comments or edits!
I've also updated the "Parts: The Rest of the BOM" post to reflect things I've been learning as I go. Mouser is going to make a mint off me on shipping alone. 🙂
Building: Amp Boards on Heat Sinks
I'm still trying to figure out what wire to recommend for the board to input jack connection (something that n00bs can easily and reliably order), so I've left the input wires for a future post, where I will also address the RCA vs. XLR options.
As usual, I'd appreciate it if y'all would check my work and provide any comments or edits!
I've also updated the "Parts: The Rest of the BOM" post to reflect things I've been learning as I go. Mouser is going to make a mint off me on shipping alone. 🙂
Current Aleph J schematic?
I'm building an Aleph J, sort of along with the development of this new build guide, and in some ways just a bit ahead. I've run into a problem with the trim pot in R7. I pre set it at 1k ohms before installing it, then tested again using the two spots on either side. Unfortunately, I now get a relatively consistent 68 ohms, with only minor changes regardless of the number of turns used on the pot.
I've asked a friend who is a very experienced EE to help diagnose the problem, and he asked to see the schematic. The version I could find (from the original build guide, and as included in the 'Noobs' build guide on the blog) does not match the current board nor the instructions.
Am I just missing the current schematic, or does it not (yet) exist?
Thanks folks.
I'm building an Aleph J, sort of along with the development of this new build guide, and in some ways just a bit ahead. I've run into a problem with the trim pot in R7. I pre set it at 1k ohms before installing it, then tested again using the two spots on either side. Unfortunately, I now get a relatively consistent 68 ohms, with only minor changes regardless of the number of turns used on the pot.
I've asked a friend who is a very experienced EE to help diagnose the problem, and he asked to see the schematic. The version I could find (from the original build guide, and as included in the 'Noobs' build guide on the blog) does not match the current board nor the instructions.
Am I just missing the current schematic, or does it not (yet) exist?
Thanks folks.
If it's the same 2K Bourns pot that I have, then you can do it without measuring, I believe. It's a 25-turn pot, so turn it all the way in one direction. Then, turn it the opposite way for 12 turns, and then one-half turn. You'll be measuring again later.
To the best of my knowledge, there isn't one document with all the substitutions on the schematic. For this case, just show your EE friend the schematic in the original build guide. They'll walk you through how once the pot is installed in the circuit that it will not measure the same. No need to have the exact schematic to understand the principle for that pot.
Also, 13stoploss has it nailed. If you haven't moved it, leave it alone. If you have moved it a lot; then just reset 1/2 way between the clicks, and you're good. This pot it used to adjust offset, so don't worry too terribly much if it's a tad off. You'll set it to its final point later.
Measuring a pot in-circuit doesn’t work. If you set it half way you’re good. 
Schematic at the beginning of this thread matches the PCB.
Aleph J illustrated build guide - diyAudio
Schematic at the beginning of this thread matches the PCB.
Aleph J illustrated build guide - diyAudio
Thank you for the prompt and helpful responses. As I understand the situation now, there was no reason to expect the pot in R7 to work correctly after being installed, but prior to adding current to the circuit. My only remaining concern is that the pot does not seem to have an obvious end point or an apparent click: I've spun it well beyond 25 revolutions and encountered neither, so its not clear how to re-set it half way. But, I'll continue with the building process and test it at the appropriate point later on.
And 6L6, I beg your pardon. Upon closer examination I now see that the schematic posted at the beginning of your excellent build guide does in fact match the current pcb. Mea culpa...your patient reply is much appreciated.
And 6L6, I beg your pardon. Upon closer examination I now see that the schematic posted at the beginning of your excellent build guide does in fact match the current pcb. Mea culpa...your patient reply is much appreciated.
That pot adjusts DC offset. When offset is as near zero as you can set it, the pot is in the proper position.
Good news!!! I got my power supply plugged in, used my light bulb tester. Bulb came on at first then went completely off and stayed off. All the LEDs lit up. No smoke. Measured 27v + and - from each side. Turned off...and man it is taking a LONG time to discharge. Like it’s been off five minutes and I’m still getting 17V and the cap board LEDs are still on...I’ve got 430k uF of caps in here. Do I need bigger bleeders or is this normal? Very excited that it seems to have worked.
Note- I’m using a v3 soft start board.
Note- I’m using a v3 soft start board.
I just wired the amps up and turned on for the first time. Bulb is now staying on but at say half power. I turned it off quickly. Power supply alone was bright light then light off. Now with amp boards in place definitely not full bright bulb but some current clearly going to bulb. Is this normal or a sign of problems?
One channel is warming up nicely, but on the other channel it’s staying cold and I’m getting 23v output bias and zero volts across the output resistors. Adjusting the R7 pot seems to not have any effect...ugh. What is the most likely problem? I hope I didn’t fry anything.