Switched gears in my clean off breadboards/learn to solder better current state. For a bench amp (prior to iPhone mic input thingy) I had tried lm386, then S8050/S8550 push pull w/2N2222 and found that after lm386 increased volume and kept from oscillating...so I ordered better BJTs.
Now I used a similar schematic with TIP31/32, a 2n3904 in front, and lm386 in front of that. This is all to drive a classic 25th speaker from the walls of my house built in 1976. I figure I'll put some effect in later (or maybe send/return) but for now just want to accomplish good enough soldering on Vero to have it together. Was thinking to use the old PCB with 4 momentaries and the 100ohm pot (or was it 10 ohm?) but that can be later.
In current state having 1M pot at the front seems to bring it up tons, do get some hum after it warms up, and distortion after half (is better/louder than the 10k was).The old scheme had output feedback from the push pull back to the 2n2222 but this one didn't - should I add that? Looking for things obvious to others but not me to improve it before putting it together.
(https://i.postimg.cc/TLHDcZKm/1-DAEBDD7-1-A42-4178-962-F-8-A0886198-D8-E.jpg) (https://postimg.cc/TLHDcZKm)
(https://i.postimg.cc/xkb36Gjf/C3-DBE1-E9-5-E0-C-4602-8-F8-E-616-DD8-CB7-E72.jpg) (https://postimg.cc/xkb36Gjf)
(https://i.postimg.cc/Ppsz9LNm/0-E458300-62-BE-416-D-9-D4-A-6-B54-BB4040-CC.jpg) (https://postimg.cc/Ppsz9LNm)
(https://i.postimg.cc/8fTdkqRc/9670111-F-0-A6-D-4-B3-D-8377-8-DE654-FA019-F.jpg) (https://postimg.cc/8fTdkqRc)
(https://i.postimg.cc/XXWkgyRW/B8-B222-A6-E394-4074-BF25-87-C7-BFCA6-D49.jpg) (https://postimg.cc/XXWkgyRW)
What does the discrete amp add that the LM386 won't do? Same supply voltage, same load impedance, same power pretty-much.
> distortion after half
"half" is meaningless. Adjust gain as needed, not just "MAX".
And it hums because it is not in a shielded box. (Or maybe crap power too, but an open build always has hum/buzz.)
=================
(https://i.postimg.cc/5trt66Q8/Nu-Tone-Scovill-1976.gif)
I did not know Scovill ever owned NuTone. Scovill is like one of the oldest manufacturers in the USA, first buttons in 1802 (my g-g-g-grandfather may have worked there) and other clothing hardware, but also a bunch of key camera developments in the brass/mahogany era.
I guess you want to use that speaker because you have it on hand, but at 25 ohms your amplifier will only put out 100mW or so. With your schematic a 4 ohm speaker would do about a Watt. I have had good results with similar amps using speakers you can find in old tube radios and tape recorders. They are typically 4 or 5 ohms, and often have alnico magnets :P
Quote from: Clint Eastwood on March 18, 2023, 05:54:05 PM...at 25 ohms your amplifier will only put out 100mW or so. ....
Might be a big third-Watt. (9V/2.8= 3Vrms, 3Vrms^2/25 = 0.36W, minus losses)
But even the tenth-Watt may be fine in a lot of home practice situations.
Also depends on the speaker. That 50-cent job may not reach a mild shout. Tenth-Watt in a Full Stack can annoy neighbors. (But this NuTone wall panel is too too cute, and sooo mid-century.)
Quote from: PRR on March 18, 2023, 05:50:42 PM
What does the discrete amp add that the LM386 won't do? Same supply voltage, same load impedance, same power pretty-much.
> distortion after half
"half" is meaningless. Adjust gain as needed, not just "MAX".
And it hums because it is not in a shielded box. (Or maybe crap power too, but an open build always has hum/buzz.)
=================
(https://i.postimg.cc/5trt66Q8/Nu-Tone-Scovill-1976.gif)
I did not know Scovill ever owned NuTone. Scovill is like one of the oldest manufacturers in the USA, first buttons in 1802 (my g-g-g-grandfather may have worked there) and other clothing hardware, but also a bunch of key camera developments in the brass/mahogany era.
Hum was (mostly) caps on power. I'd joined the breadboards so once I moved it to the other side of the filter caps on the 386 board it went away.
With just the 386, just the 8050/8550, and 386 -> other it wouldn't drive the 25ohm speaker. With it this way it works well, and not really quieter than through my 4ohm 10W TEAC goodwill find. It's not super loud... I do make some MAX1044 chips, maybe I should step up voltage on the discrete amp?
I can't stand it though I love those things, couldn't toss them when remodeling the house! I still have the main one in the wall in the kitchen, was almost thinking to do a project that uses it all (3 like pictured and a speaker at the front door) but doing a practice amp for now.
(https://i.postimg.cc/8F9dWNH2/3366-F5-CF-074-E-44-DA-A360-D79705779244.jpg) (https://postimg.cc/8F9dWNH2)
Of these recently acquired choices, is there a louder pair I might plug in?
I haven't checked the details but what you might find is to get more power R3 needs to be reduce. What often happens is the resistor on the base (R3 = 1k) cannot supply enough base current.
Bootstrapping can help a bit - add C5 and split your R3 into two resistors, here R8 and R9.
You still need R8, R9 to be low enough to supply supply the base current.
(https://i.stack.imgur.com/QiPn5.jpg)
A Darlington output stage lets you use higher value of R3 but then you lose 0.7V swing, which can be significant, on a 9V supply. However then you will need to add more diodes to bias the output stage.
Also make sure the DC bias point at the emitters is mid-supply to maximize swing.
The biggest problem with the amp is no emitter resistors on the output transistor emitters. If the output stage heats up it could get thermal run away. Thermally connecting (touching) the diodes onto the power transistors helps.
At the end of the day. It's a small amp but you need to *design* the amp, and that's not a simple task for a newbie.
This perhaps summarized a lot of the points. The feedback bias with the 470k helps DC biasing of the output stage. You design is hard to maintain the DC voltage at the emitters. You might need a resistor in series with the input to tame the gain. Change the value to suite the lower supply voltage.
(https://4.bp.blogspot.com/-wxt_hOkHTxk/WWbW5Xj03tI/AAAAAAAACdU/2BqSdLk2Jdgez6B14wThPJV6lkIUX--UgCLcBGAs/s640/NV_0104_Marston_FIGURE16.jpg)
[FWIW, you don't need such large driver transistors for the Darlingtons.]
Thank you Rob, I've saved those schematics for study. The upper left 3904...well, I'll study it a bit and come back with questions.
For full disclosure, these were the schematics I used. First with the 8050:8550 transistors
(https://i.postimg.cc/TL2W1cpH/36-A9-B2-E2-C8-BE-4612-821-A-890-CDC7554-D1.jpg) (https://postimg.cc/TL2W1cpH)
And this for the TIP31/32
(https://i.postimg.cc/t7MVRWy2/2-E1-BDBE3-FB82-4-A1-A-9-A35-27-B12-AD912-E5.gif) (https://postimg.cc/t7MVRWy2)
QuoteFor full disclosure, these were the schematics I used. First with the 8050:8550 transistors
The first one has the emitter resistors and a low value collector resistor (330R) and the 33k resistor from the output back to the base of the first transistor. While simple it tries to do the right things.
The second one is likely to be problematic.
(The second circuit I gave uses two NPN transistors for both output stage polarities but the driver stage is NPN for top and PNP for the bottom. This is called a quasi-complementary output stage. The upper combination of transistors is a Darlington but the bottom combination of transistor is called a Sziklai pair. The quasi-complementary output stage was popular in the old days and an musical instrument amps.
These days it's more common to see the use of a NPN power transistor and a PNP power transistor:
- the upper transistor combination would be an NPN Darlington and the lower a PNP Darlington.
- or, you can flip the whole idea and use a Sziklai pair (NPN driving PNP) for the top and a Szikair pair
pair (PNP driving NPN) at the bottom.
You can't just chuck any only thing in there you have to design the amp to suit whatever type of output
stage you choose.
I only mention these things so you can read up on output stage options.
Amplifier design can get fairly involved.)
Quote from: Rob Strand on March 18, 2023, 09:15:04 PM
I haven't checked the details but what you might find is to get more power R3 needs to be reduce. What often happens is the resistor on the base (R3 = 1k) cannot supply enough base current.
That's often true. But for these transistors (hFE ~~150 at 0.2A) and 25r load, it won't be too very starved.
Quote from: Rob Strand on March 18, 2023, 09:15:04 PM.....you need to *design* the amp,...
That's always true. That's why I was poking at "
what's wrong with the '386?" It really is a fine design, and is underloaded here. It may be confusion between gain, distortion, and power output (three very different things that melt together in the mind).
Thank you for all of that, much to learn on. Time to study up on basic transistor circuits too, do a study guide. Might try your second circuit with the 122/127...and adjust accordingly. Maybe try adjusting the bias, the resistors, and adding a feedback resistor (and emitter resistors) on this one.
Quote from: Matthew Sanford on March 18, 2023, 11:55:05 PM
The upper left 3904...well, I'll study it a bit and come back with questions.
Just a humble V
BE multiplier (rubber diode).. :icon_wink:
It serves for voltage reference precise setting contrary to series diodes "stepping" one..
https://en.wikipedia.org/wiki/Rubber_diode (https://en.wikipedia.org/wiki/Rubber_diode)
Thank you all so much again, my learning has been so sporadic and random in 10 minute blocks, the fancy of the day, and you're pointing me to how to fill in the gaps. This will take a minute, but I'll actually work to design it properly with your suggestions and the math.
QuoteThat's often true. But for these transistors (hFE ~~150 at 0.2A) and 25r load, it won't be too very starved.
For nominal devices the 1k is likely to be losing some swing even with a 25 ohm load. If you only want to lose 0.5V swing then the voltage across the collector resistor needs to be < 0.5V at full output current, so maybe 470 ohm. The lower limits on the o/p transistor gain are quite low on these devices - that really screws things up.
QuoteThat's why I was poking at "what's wrong with the '386?" It really is a fine design, and is underloaded here. It may be confusion between gain, distortion, and power output (three very different things that melt together in the mind).
Agreed, it's very hard to beat those integrated amps with a simple amp design. All the hard work is done, and it will work. If you want to do a HiFi geek solution and throw a lot of transistors at a complicated design, that's better than the LM386, then that's possible too. For simple designs integrated generally wins.
Just for fun I compared a number of simple designs. I wouldn't call them working designs. They are barely enough to compare the *output swing* of the different amp structures. I used an 8 ohm load. For a 25 ohm load we would scale-up many of the resistors and get similar results.
So clearly the boot-strapped output stage helps get more swing. For a 9V design at least, the extra voltage drop of the Darlington out weights the gains. The Sziklai does look promising.
[schematic]
(https://i.postimg.cc/jDVJ5yp6/Simple-Amp-Output-Swing-schematic.png) (https://postimg.cc/jDVJ5yp6)
[clipped waveforms]
(https://i.postimg.cc/9rRz91ZR/Simple-Amp-Output-Swing-waveforms.png) (https://postimg.cc/9rRz91ZR)
In order to keep the simplest structure amplifier I didn't investigate adding transistors to the voltage gain sections. That would also be a way to get higher input impedance and no doubt less distortion (which I have not considered).
Notice this 2.5W design from TI uses a very low collector resistor on gain stage:
https://www.petervis.com/Amplifiers/tip29-and-tip30-amplifier-design/2-5-watt-amplifier.html
https://www.petervis.com/Amplifiers/tip29-and-tip30-amplifier-design/amplifier-design.html
I should mention a couple more things:
- the power transistors in my simulation have a gain of about 80
- the designs with low collector resistors on the gain stage will draw
extra supply current with no signal, perhaps +20mA.
I was just thinking I had gotten some lm1875T chips and it could be simpler to use those for now, for this, in bridge or to drive a power transistor push-pull. But all this makes me want to push on, so maybe a ic for now then go for the learning after...I'll let you know
Quote from: Matthew Sanford on March 20, 2023, 02:54:02 PM
I was just thinking I had gotten some lm1875T chips and it could be simpler to use those for now, for this, in bridge or to drive a power transistor push-pull. But all this makes me want to push on, so maybe a ic for now then go for the learning after...I'll let you know
The LM1875's are great but they are only spec'd for 16V single supply (+/-8V dual supply).
The 9V supply is always going to cause limitations because the majority of amps won't swing to the rails. As far as easy to get chips go the LM380 can be used in a bridge (LM386's bigger brother). There's zillions of amp chips which were targeted for 12V to 16V and operated down 8V to 9V and a large proportion could operate in bridge mode. Many have gone obsolete and sourcing them is risky due to fakes.
Thank you as always for the advice and info. I may do it anyway for now with those and multiple 9v batteries...maybe an option for an old laptop or other plug that offers higher voltage... if I were to run it from different voltage levels, would the resistor values need to change?
Quoteif I were to run it from different voltage levels, would the resistor values need to change?
Most IC power amplifiers don't require any changes when changing the supply voltage.
If you change from a single (say +18V) supply to a dual (say +/- 9V) supply then you will need to make some changes to the connections. Best to check the datasheet for tips.
IC's like the LM380 and LM386 are designed for single supply so you need to keep ground pins wired to the 0V. So in a +/-9V circuit with an LM1875 you need to keep your existing LM386 running off +9V and 0V.
Ok, sounds good. I think I may ditch the 386, it (I believe, no extra mark) is the lowest, so 1/4 watt. May just do an non booster first, or the first (better) of the first schemes I shared with S8050/S8550 instead... though I did see a schematic with a TIP31/32 output after the 1875.
Still, might start simple 2n2222 buffer to the 1875 then play from there. Will definitely pour over the data sheets when this goes (and likely come back with questions!)
(https://i.postimg.cc/rKdFPVvw/12-F5747-F-BCDE-47-B4-8-BEF-816-CD6-ACF30-A.jpg) (https://postimg.cc/rKdFPVvw)
So I set up the data sheet LM1875 single supply circuit with an 18v (repurposed laptop supply) source and it works out pretty well on the 25ohm house intercom speaker. There is a bit of...whine I'll call it when not playing, so I'm not sure why, not too many flying wires on it.
(https://i.postimg.cc/xXR7GHtJ/8-B93-F80-C-4128-4-CD5-8-FB5-3-B5-DE232-EF93.jpg) (https://postimg.cc/xXR7GHtJ)
I was thinking it might want smoothing caps directly by the power supply coming in though recommendations seem to say closest to the chip. I had tried a TL072 buffer first with Rf 10k and Rin 1.5k (I'm out of 1k) and the other op amp out to -in and + to ground but no sound to the power amp, so ditched (after trying 10k from 1875 out to 072 -in) it for now. I'm thinking once it's off the breadboard the slight noise should reduce, but are there other things I could do to filter the sound better? One other thing, it is only when the input is connected; with the 072 it was silent, and also until the guitar wire is put to input. Volume all the way down is only slightly louder noise. I'm reviewing my ground situation now so will report back if I find issues there...
I found the best size drill bit so I will cut Vero traces properly! Still, any suggestions are most welcome!
The noise probably comes from the switch mode power supply. I use a laptop brick a lot for my projects, and they are perfect for class A amplifiers wich draw a lot of current. But with class AB amps I have ran into the same noise problem as you, and the cause is the low current draw at idle. The easiest solution is to make the power supply deliver a certain amount of current all the time by, for example, inserting a 100 ohm 10 watt resistor between + and -.
You could also of course make a low pass filter, the most elegant I guess would be an LC filter.
Good luck!
Ok, sounds good. I think all my resistors are 1/4W so I'll need to get some to handle that, or an LPF instead. I'm moving it on my breadboard currently as the 1875 was kind of loose ish, and should be able to mock up an LPF for now...targeting something like 10KHz? And placed on the output before the 2200u BFC?
I reduced it for now by twisting the power and the inputs and adding a 330R on the input to the 1M log volume pot, now it's only there with pot turned all the way up, and pretty quite even then. I don't have much of a heat sink on it, but I'm going to veroboard it and call it functional, then go back to it later.
One question: do you think the ferrite on the power cord could cause any of it? I figure it calms it and smooths issues with a supply like that but just checking.
(https://i.postimg.cc/30XDq2Sm/7409-BE99-B77-A-49-B0-9-BF1-9-D4515176-DFB.jpg) (https://postimg.cc/30XDq2Sm)
Quote from: Matthew Sanford on April 01, 2023, 05:35:34 PM
And placed on the output before the 2200u BFC?
No, I mean a filter at your dc input. I am not an expert on this at all, and SMPS's can be a pain to get quiet, a search on the net will tell you. The best solution seems to be an LC filter. If you don't have a power resistor for the solution I mentioned before, you could try the LC filter option, but then you need a suitable choke.
Ok. I'll look into LC DC power filters, the more you know...but may just box it up for now, and come back to it with better understanding later. The noise isn't too bad, and a little extra resistance (turning the pot down) clears it out completely.
Thank to Clint (et al) for all the advice, it's invaluable, and one day I'll try designing a discrete AB amp, but fast track works for now
Quick update (and cautionary tale/reminder): so excited for my soldering station, I soldered all the outboard stuff for the 1875 data sheet single supply circuit (worked great on the breadboard) and put sockets to plug the speaker in, fired it up and...pop! Bye-bye 1875. I'd gone over my layout a bunch and knew it to be right, was going to post the pics for more eyes, but realized I'd put the other side of the speaker not to ground but the other side of the output BFC. I'm assuming it went to the feedback and that's what killed the IC?
For removing multiple pin ICs, is it best to use a blade tip and try to heat them all at once?
Also my Aunt told me when working electronics (60s or 70s) and organizing diodes and resistors hanging them on a piece of paper, then shaking them to make them dance, they were Diana Diode and the Resistor Sisters...sounds like a good electro band!
Pics for posterity
(https://i.postimg.cc/McqTxphx/53-E95-BCA-9-C02-4354-848-F-A3-CA478-ED4-A8.jpg) (https://postimg.cc/McqTxphx)
(https://i.postimg.cc/VrNkrHfV/ECCE99-FD-1-F08-4549-859-A-E24032-D43-C7-B.jpg) (https://postimg.cc/VrNkrHfV)
(https://i.postimg.cc/67cQQNXZ/F09-E266-D-348-E-48-ED-BB7-C-BD26-C43-C40-C3.jpg) (https://postimg.cc/67cQQNXZ)
Quote from: Matthew Sanford on April 17, 2023, 12:05:34 AMI'd put the other side of the speaker not to ground but the other side of the output BFC. I'm assuming it went to the feedback and that's what killed the IC?
Other side of this life... so, like this?
(https://i.postimg.cc/PLWHTpDs/othersideoftheoutput-BFC.gif) (https://postimg.cc/PLWHTpDs)
That won't hurt anything. Won't play, but won't hurt.
What makes you think it is dead? If you did kill it, you musta done something cleverer than this.
Yes, just like that. I only know as I opened it expecting a cap popped, I've become familiar with the sound a couple times, but it was the lm1875 that was deformed. I should note the power supply I used was different than on the breadboard, though both 18v laptop style power cords...this one's connector fit nicely in a boss power Jack, with ground on sleeve, so I used it. I did wire two 9v In series with ground to the battery pin and power to power, both to the jack, but no batteries in. That'd be correct wiring though right?
I'll go over the layout and see, must be something there...possibly in the 22k coming off the power in pins trace.
Quote from: Matthew Sanford on April 17, 2023, 12:05:34 AM
For removing multiple pin ICs, is it best to use a blade tip and try to heat them all at once?
The best way I've found without having specific tools for the job is to cut the body of the chip out by cutting all the legs close to the body with wirecutters. Then you have a lot of individual legs sticking out of the board, which is lots of little problems instead of one big problem! You can then turn the board upside down, heat each one, and with a bit of knocking and poking, they should fall out.
HTH
K, makes sense, or tweezers to pull each individually. I'd had issues trying to pull a good 7805, but this is a bad chip now, so chop the legs it is.
Poor lil legless LM1875...
(https://i.postimg.cc/JHmnC26x/IMG-2255.jpg) (https://postimg.cc/JHmnC26x)
So reading all over I'd seen if you remove the reinstall the speaker the BFC will discharge and fry the chip...no ground on the - side but maybe the ac signal feedback through the 25ohm speaker made it discharge....
Current conundrum, no sound....except when using the DMM to check pin 4 Dc, get some crackle, though it may have tapped the pin 5 v+. I've checked continuity and did reflow solder (mix of no lead and 60/40 Xtronic gave).
Pin voltages:
1 (+in) 9.68
2 (-in) climbs to 17.2
3 (g)
4 (out) 19.56
5 (v+) 19.62
I'm guessing pin 2 should match the pin 1 voltage, but here it's almost the full supply. I've looked over my part placement (too cramped!)a bunch so I'm sure it's not going to pop out to me, here's side pics if it helps. Any ideas what I should focus on here?
(https://i.postimg.cc/vDf1cW5f/IMG-2256.jpg) (https://postimg.cc/vDf1cW5f)
(https://i.postimg.cc/MvwnRvY4/IMG-2257.jpg) (https://postimg.cc/MvwnRvY4)
(https://i.postimg.cc/7fNfNwsL/IMG-2258.jpg) (https://postimg.cc/7fNfNwsL)
(https://i.postimg.cc/G4h97VVx/IMG-2259.jpg) (https://postimg.cc/G4h97VVx)
Tomorrow I'll go at it with the audio probe, got a kid's senior choir concert tonight
So audio probe shows it gets to pin 1, not on 2 or 4. I am guessing it is a bad layout issue, I crammed it all in and so better to have separate ground traces that jump to join at pin 3? Currently it goes chip -> power caps -> bias divider resistor/cap -> power ground -> output zones cap ->input resistor -> speaker ground. Reading the data sheet again (more fully) I feel like this layout is causing power issues, nearly doubling pin 2 voltage compared to pin 1, etc.
Am I on the right track?
I had issues with the LM1875 vero layout not working right and it sat to the side of my workstation. I decided to get back to it and make the original idea work by thinking through what Rob was telling me, and came up with something to make it work! Volume goes 0-50%-100% switch off gain then 50%-0, nothing much fancy but open and low up to 15th on high E.
On the breadboard it was more clean through the volume increase, breaking up towards the top end, with the gain switching to 200 on the LM386 by placing the cap in. Once on vero it was doing a put-put motorboat till I moved the TIP ground to the ground near the decoupling part instead of through the LM386...so I need to work on better grounding ways. That gave me oscillations till I put a 2200u to ground from the TIP power and a 100u from the LM386 power. Now all boxed up I get this, which makes me happy!
So this is the scheme I went with, which needs revisions but I have a couple more waiting for circuits so this works for now... plus these are findable on eBay (like this cheapest one (https://www.ebay.com/itm/266444876497?hash=item3e095a2ad1:g:L00AAOSwTENlIZ6d&amdata=enc%3AAQAIAAAA8FEqS99dMrJNHAr0roUfYy2sFOyccsMGwt2yx3fNxdD7c0Rbxyc0rUpLKeLsaVxUGH68TGJ%2Ffdx6aCm2%2Fvkc8bf1PPxIlJM6fQHVBRjtZuQmKGN9SIHe%2BQEmJ7kByVHBXjQiyPyJ383WYas3vyVRuBycW3vzXrk15vQ6WXYRoowluMGZGTcMqF1ctp0HJWLaRyXNy%2FQ0DqcThyIpPqgHmeUClo4TJWvgTeHJ8xPIWsnnJ%2BMUUiANjHB95o%2BdOYxRBj9Evkbyni%2B17sFWfbae6k%2Fsb9b6EfYudJ6opRRSbloR7r5%2FhxORoptJb5ax%2BeVf7g%3D%3D%7Ctkp%3ABk9SR7S5qIP4Yg)) I'm thinking I should have a 2.2M to ground on the input, might bring more treble?...for simplest.
(https://i.postimg.cc/Y4PgPG5p/IMG-2804.jpg) (https://postimg.cc/Y4PgPG5p)
More to fix would be to limit the input signal on the LM386 and put something inbetween it and the push-pull, maybe a phase splitting 2n2222 or a darlington or something. I'm sure my value choices here could be better even as is too. Plus add a 78L09 for the LM386 (I do like how it distorts!) and use 18v for the rest.
Odd thing with this is for the gain on the LM386 I soldered the 10u from pin 1 through the spst to pin 8, but for the video I have it switched on in the beginning then put it off at the end and it kicks up the distortion...I just realized it's pin 8 I have on the center, so it goes to cap->pin 1 or hangs with pin 1 -> cap blocked in the switch.
I went with this for my layout, put the push/pull portion a row low but did the original cuts before noticing so new layout drawing (this) with new cuts and jumpers.
(https://i.postimg.cc/zH7G94yn/IMG-2805.jpg) (https://postimg.cc/zH7G94yn)
Kind of drew in red lines for the new ground routing from the push/pull and the lm386 on my phone and the cut so I wouldn't forget when doing it. I made a foolish decision initially to just run the 9v through the push/pull to the LM386 and ground through the LM386 to the push/pull. I have been a slow learner on ground and power routing, very likely the reason my LM1875 didn't work out so well. So for this one, I tied the ground after the power decoupling stage to another row, then speaker ground, then push/pull ground, then all the grounds from the LM386 stuff and input. I figure that is as close as I am getting this to a star ground - but for it, that all should return on the other side of the power decoupling caps, or is it better to run them directly to the jack side of it?
Last thing I'm thinking on are the "Talk" and "Listen" 12 pin momentary switches. They run to different wire connector screws, for different portions of the house intercom system I'm sure, but I'm thinking they should go to flip flops to turn on/off different effects, if even only a DRM or something, or PT verb, other distortion choices, bassballs, hmmm...
Anyway here is the vero, before wires and mini heatsinks, with everything including the caps stuck in to pin sockets, and the backside.
(https://i.postimg.cc/R6BBTGgK/IMG-2809.jpg) (https://postimg.cc/R6BBTGgK)
(https://i.postimg.cc/G80NC2YC/IMG-2815.jpg) (https://postimg.cc/G80NC2YC)
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