And of course ... a pic of progress. Trying to get the chassis laid out a bit better than some previous builds for shorter / cleaner wiring. First time mounting transformers to the front panel. 😀
I think I'm going to mount the PSUs tighter to each other to allow a bit more access to the amp boards (and keep them just that much further away).
Any suggestions greatly appreciated as always.
I think I'm going to mount the PSUs tighter to each other to allow a bit more access to the amp boards (and keep them just that much further away).
Any suggestions greatly appreciated as always.
if you're really Old Dog With All The Fleas (needed) , your operation is big enough to buy Drekload!! of mosfts, then you have a flock big enough to do whatever you wanna do, even matching them by xconductance
though , in time is shown to as that even that sort of ODWATF is not bothering doing that- matching by Ugs at chosen Iq is good enough, even if we are talking about parts put in multizilliondolllllarcosting thingie, sold to Customer
so, your No.2 is what counts
use rest of the day for chill, with or without beer or wine
🙂
though , in time is shown to as that even that sort of ODWATF is not bothering doing that- matching by Ugs at chosen Iq is good enough, even if we are talking about parts put in multizilliondolllllarcosting thingie, sold to Customer
so, your No.2 is what counts
use rest of the day for chill, with or without beer or wine
🙂
Thanks as always for the perspective, ZM. No soldering iron or voltage in hand today, so beverages are a must. 😀
I appreciate knowing both the practical side and understanding the goals. Based on previous experience (not much, but a few tubes of parts) I'd be okay taking a random 12 from the same tube / lot with 1R source resistors. I love to learn what we're really trying to accomplish. Plus, for this build I maaaaaay have up to 12 devices in parallel at some point and at least 6, so I wanted to be sure I sorta understood.
Each day... a bit more... then my brain hurts... then drinks..
I appreciate knowing both the practical side and understanding the goals. Based on previous experience (not much, but a few tubes of parts) I'd be okay taking a random 12 from the same tube / lot with 1R source resistors. I love to learn what we're really trying to accomplish. Plus, for this build I maaaaaay have up to 12 devices in parallel at some point and at least 6, so I wanted to be sure I sorta understood.
Each day... a bit more... then my brain hurts... then drinks..
Is it wrong to pick a cap based on color?
Yes. It. Is. As penance you must build more amps. 😀😀😀
you know, match them (those 12 random ones), just in case
Absolutely - I just got shiny new 100W, 50ohm resistors and heatsinks. My bench supply is feeling neglected, too. Even if I don't know WTF I'm doing... I gotta do SOMETHING to feel useful.
Also, there's a good rumor that if my matches are fairly tight - that I can use 0R47 source resistors which has some benefit or another that I can't quite put my finger on... I can't remember who told me that though.... (cough... 6L6 and ZM).
I've told ya that 0R33 and even 0R27 are possible, under some conditions ...
always look at already proven designs - F4 is having zilch of temp. feedback in biasing, and it's made with 0R47
always look at already proven designs - F4 is having zilch of temp. feedback in biasing, and it's made with 0R47
Apologies - Yes, I definitely remember that. I have 0R22, 0R47, and 1R0 on hand depending on results. I can get a hold of 0R33, but have not ordered.
One with each color of the rainbow... 😀 😀 😀 That'll keep me busy. Back to chassis layout.
I understand the advantages of each channel having its own power supply (i.e., dual mono). However, something that’s been puzzling me is when an amp can also be run in a balanced/bridged mode, when each channel then had two PSUs, one for each phase. One advantage of a balanced PP amp is that the current draw variation from the PSU is much much smaller than a non-balanced amp. (See here: The diyAudio First Watt M2x). But this only happens if the two phases are drawing from the same reservoir - If each phase has its own PSU, then each PSU has to handle the larger current variations. It would seem ideal to minimize current variation to minimize the influence of PSU output impedance at various frequencies.
I’ve been wondering if it would be worthwhile to have the PSUs be switched to parallel when in balanced mode (i.e., the + caps from each toroid are paralleled, the - caps as well) and isolated from each other when in stereo mode (i.e., each board has a completely independent supply). That way, you get the isolation of dual mono PSUs in stereo mode but then you minimize the influence of PSU output impedance in balanced mode.
Thoughts?
I’ve been wondering if it would be worthwhile to have the PSUs be switched to parallel when in balanced mode (i.e., the + caps from each toroid are paralleled, the - caps as well) and isolated from each other when in stereo mode (i.e., each board has a completely independent supply). That way, you get the isolation of dual mono PSUs in stereo mode but then you minimize the influence of PSU output impedance in balanced mode.
Thoughts?
Fascinating question. I know that was directed at the group in general, but if it helps - my two PSUs will be run in parallel in balanced and standard "dual mono" when not. A single 400VA transformer won't handle (potentially) one of the iterations I want to try. I never considered the difference in current draw between phases. Thank you for the clear explanation. I suppose I got lucky that will be a side benefit.
I love the idea of a switch. Someone posted a very cool PCB with DIP switches earlier in the thread for the front end, but I have not seen a solution for a switch like you've mentioned for the V+, V-. Any easier way to use the same amp both bridged and stereo would be fantastic. At the moment, once I convert each over to monoblocks, it's all "hard wired".
Here is the wiring diagram I had come up with for one channel. I had considerable help removing some nasty ground loops I had planned in my first few iterations and potentially a fire hazard. If anyone else is considering this type of thing, I hope it helps. Also, feel free to provide any thoughts / ideas.
View attachment Wiring 3.pdf
I love the idea of a switch. Someone posted a very cool PCB with DIP switches earlier in the thread for the front end, but I have not seen a solution for a switch like you've mentioned for the V+, V-. Any easier way to use the same amp both bridged and stereo would be fantastic. At the moment, once I convert each over to monoblocks, it's all "hard wired".
Here is the wiring diagram I had come up with for one channel. I had considerable help removing some nasty ground loops I had planned in my first few iterations and potentially a fire hazard. If anyone else is considering this type of thing, I hope it helps. Also, feel free to provide any thoughts / ideas.
View attachment Wiring 3.pdf
Hmm, after looking at that diagram, it seems like a switch would be unnecessarily complex - all one would have to do is just rearrange connections to a terminal block, like you have. Routing all the necessary lines to a single switch would probably introduce a lot of headaches (since ground would have to be switched, too...)
Out of curiosity, what prompted you to want to run your PSU in parallel when balanced?
Out of curiosity, what prompted you to want to run your PSU in parallel when balanced?
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that's simple, really
if you have intention to use basically stereo amp in bridged or parallel fashion - make common PSU for both channels, from several reasons ...... and main is - no mess with GND ( which you'll have if you have two PSUs,each having separate GND and they're meeting only at chassis after those NTC/Bridge hokuspokuses)
so , in short - if main use is bridged/parallel - use common PSU
if you have intention to use basically stereo amp in bridged or parallel fashion - make common PSU for both channels, from several reasons ...... and main is - no mess with GND ( which you'll have if you have two PSUs,each having separate GND and they're meeting only at chassis after those NTC/Bridge hokuspokuses)
so , in short - if main use is bridged/parallel - use common PSU
We must be brothers from different mothers 😀
I just got the JFETs for the Balanced Iron Pre, BA, and other future builds along with some extra Keratherm in the mail today. That leaves only matching the output devices and getting some re-jiggering of the chassis done. The steel cans from Antek were a bit bigger than I thought. I hope to have everything by next weekend.
My Focusrite should be here soon. I read the REW thread a number of times, but until I get my hands on it and play - I won't know how successful I'll be.
I just scored a second-hand oscilloscope to try and learn a few other basic measurements. The probes should be here in the next day or two. That's a manual I don't look forward to reading. I read the "quick guide", and that was enough to cross my eyes. 😀
Love to compare notes along the way - I learn a ton from everyone in the forums!
Make that triplets.
I just acquired a fully refurbished/tested Tektronix 2465b oscilloscope, probes (400MHZ), an HP3312A function generator, and an HP3478A bench multimeter (5.5 digits) that supports 4 wire measurements (if needed). I already have the Akitika 1khz 2ppm oscillator and the Focusrite Scarlett 2i4 unit is on its way.
Understanding how to use the oscilloscope/function generator and finally a audio analyzer (REW+Focusrite+Akitika) should help us all test each and every one of our analog projects.
Fun stuff. But first, I'm finishing up Christiansen's DG300B...the SMD soldering on the Maida Regulator and 3 filament regulators is fun, fun, fun.
Best,
Anand.
WOW! OK, funky coincidences...
I read in the REW thread early on re: your recommendation for your Aktika. I may get one, but the signal generator in REW seems to be working like a champ. Now, if I can just get REW / Focusrite software to retain my settings and not crash out in Windows. 😀 I think I'll be doing it on my Mac.
The Tektronix I scored from a buddy is an old, but seemingly capable unit - TDS 784D. The last time I touched a scope was over 35 years ago in grade school, so I am trying to digest the manual and watch YouTube videos. My probes haven't made it yet. Amazon is showing Thursday potentially. I got a very basic set.
I'd love to have a (I hope I get the term right) notch filter or a distortion analyzer / function generator combo that could separate the fundamental from the harmonics. Seeing the waveform on the scope for the distortion vs. or in addition to the FFT makes it much easier for me to understand - particularly with relative phase.
I still have all the parts for 2, DG300bs to build minus the most expensive chunks... tubes, OTs, and chassis but I do have these. Literally the reference for all DG300b builds. 😀 😀 I need to get off my rump and try one with the F4.
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A couple reasons - some potentially founded in solid logic... others maybe not so much 😀
1) When I did the back of the napkin math for figuring out what transformer I needed, I didn't have enough VA. For a crazy build of up to 12 devices per side / 24 per channel 025A or 6 per side at 0A50 - one wouldn't get it done.
I recalled a post ages ago that I cut and pasted into my notes re: using two donuts as one. I also remembered ZM posting that this must (or should ...) be done after rectification. So, when I inquired - he and 6L6 were kind enough to help me not start a fire and eliminate some nasty ground loops in my original plan.
2) I knew I was going to go from BA-3 to BA-3b monoblocks, and I'm "efficient" (lazy). I did not want to yank out a PSU and buy a new, higher VA donut. It took me long enough to mount those silly things.
3) I like to keep things fairly common. As you've witnessed, I can be a dodo. Sticking with known-working-good modules minimizes my risk.
4) I'm frugal, and I already had 4 PSUs set up identically for First Watt Amps. Easy-peasy.
5) I don't need the highest voltage swing, and I want to try more current - so I could get away with the 18V secondaries on my existing donuts. I also had 35V caps on my PSUs, so w/o bumping up the caps or building new PSUs - I only had so much room to move up for the rails.
tl;dr - I had 'em and knew I was going to build a "Hot" BA-3 and convert it to a BA-3b. One of my existing donuts wouldn't have worked, I like dual mono, and I'm cheap. 😀
Itsallinmyhead, see post #711 above regarding the conversation we had about regulating the front end of BA3 or BBA3. This isn't the example I was thinking of, and this is SE version, but Sala's shunt regs are used.
I may like to use those, but will follow my usual advice to build it as per instructions, then add regulation.
Watching to see what you do. I am not deconstructing my BA3 into mono blocks. It has 31 volt rails and I think 18 + 18 giving 24 volt rails will give plenty of juice for BBA3, unless someone tells me otherwise. Plus I have come to like this amp so much I want it as is.
You may find the same. I see 3 Deluxe 5U chassis in your future, along with aforementioned Balance Iron Turtle!
Russellc
I may like to use those, but will follow my usual advice to build it as per instructions, then add regulation.
Watching to see what you do. I am not deconstructing my BA3 into mono blocks. It has 31 volt rails and I think 18 + 18 giving 24 volt rails will give plenty of juice for BBA3, unless someone tells me otherwise. Plus I have come to like this amp so much I want it as is.
You may find the same. I see 3 Deluxe 5U chassis in your future, along with aforementioned Balance Iron Turtle!
Russellc
Russellc - Thanks for the reference! I knew I'd seen it around somewhere.
Similarly, I am not going to regulate the front end. This build has enough complexity in the little things that are tripping me up. No need to add to my potential to create a mess of things. Note - I did try to leave plenty of room... just in case... I want to try it in the future.
I definitely see something like the Pumpkins / Turtles in my future.
PA
Similarly, I am not going to regulate the front end. This build has enough complexity in the little things that are tripping me up. No need to add to my potential to create a mess of things. Note - I did try to leave plenty of room... just in case... I want to try it in the future.
I definitely see something like the Pumpkins / Turtles in my future.
PA
Alrighty then - I finally set aside the time to measure all my MOSFETs using 0A5 with a heatsink.
I have to say, now that I've done it myself vs. doing them in "free air" - it makes more sense. The Vgs stabilizes much faster and evenly with the part on a heatsink.
Now to sort them and set them aside for projects. 😀
ZM -
For the BA-2 complimentary output stage - I have a range from 4V10 to 4V17 for the Ns. I have 4V29 to 4V34 for the Ps. I can break things down into smaller groups as needed
If I pick the "cream of the crop" for closest values in groups of 6 Ns and Ps (I may have up to 6 in parallel in the future) any concern with using OR22 source resistors?
For the BA-1 SE output stage - If I use between 4V28 and 4V33 for one channel and 4V33 to 4V42 for the other is there any concern with using OR22 source resistors? I got a bit of a wider spread in that batch. That's across 25 units.
I have to say, now that I've done it myself vs. doing them in "free air" - it makes more sense. The Vgs stabilizes much faster and evenly with the part on a heatsink.
Now to sort them and set them aside for projects. 😀
ZM -
For the BA-2 complimentary output stage - I have a range from 4V10 to 4V17 for the Ns. I have 4V29 to 4V34 for the Ps. I can break things down into smaller groups as needed
If I pick the "cream of the crop" for closest values in groups of 6 Ns and Ps (I may have up to 6 in parallel in the future) any concern with using OR22 source resistors?
For the BA-1 SE output stage - If I use between 4V28 and 4V33 for one channel and 4V33 to 4V42 for the other is there any concern with using OR22 source resistors? I got a bit of a wider spread in that batch. That's across 25 units.
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doesn't matter which style of OS, rules are the same
cream of the crop would probably be ok with 0R22, with decent heatsinking
cream of the crop would probably be ok with 0R22, with decent heatsinking