Those look like voltage regulators.

Clean the schmoo off the top where the "L78" number is so we can read it.
That is likely the part number.

Hi... I'm looking at a Bose L1 model II PA amplifier and I'm looking for help in interpreting a series of voltage measurements. There's a pair of what I think are transistors that look suspicious. On the diode mode these are the readings I got. Can someone help me? Thanks.You cannot view this attachment.You cannot view this attachment.

Quote from: JonnyDeth on April 22, 2026, 12:45:21 PMAnyway, I'm neck deep in my own company development and hopefully will launch my guitar and general audio equipment as planned by December this year. I have 3 preamp stages nearly complete that are out of this world. Instead of claiming tube emulation, I outright just configured the transistors to physically do the same thing as tubes and what do you know, unlike every tube emulator, simulator etc. out there that has ever existed, these simple circuits sound indiscernible from tubes.

They fizzle, they zing, they glitter when you hit pinch harmonics instead of grind. It's outright comical to how simple that is, but I'm digress and boasting. My passion for creating in electronics opened up the universe to my control.

Be sure to share here when they come to market - we love hearing about new solid state gear!

This may interest all who install a new tank and get funny squeals.

I have bought a like-new Peavey Special 212, the reverb was dead. When I wound up the control, hum would appear. This would suggest an open connection.
I now did the usual problem exclusion procedure and bang: the output side was open.

I read a little and all reverbs seem to come from the very same company these days.
Some say, despite that, MOD are better. Indeed they do not have the transducers plugged with some connector, but rather soldered directly.

I installed it and it did its job, but even at cautiously low volume and moderate control settings, feedback would works its way up slowly. Exactly like a microphone on the verge of feedback howling.

I had noticed that the transducer coils are loose, not as bad as on the replaced tank (which was an accutronics), but loose.
A dab of fast settling MMA glue (structural, won´t drip...) on all transducers cured that within minutes.

Some people have sent their tank back at this point, just to receive an equally bad unit that worked by chance.

I had written to Rod Elliott over the matter and he reckons that rattling coils may be the cause for accelerated material fatigue of the small wires. He also pointed out to stay away from the magnets and the suspension of the springs with the glue - naturally.

I remember being asked to use small rope or string to tie components and wire looms down with on a certain build I did in the early 1980's, apparently that was an old standard that the customer was still using from long ago.
I have also used a plastic type of string on some jobs, that was the good old days when a wire loom was on full display and wires had to run perfectly in parallel in the wire looms.
I can't remember the specific knot we had to do as well when we tied it all up.

Quote from: aquataur on April 22, 2026, 12:19:19 PMI totally agree with you, although I don´t know what your overall message is and whom you direct this towards.

As far as my little box goes, I made quite clear that this is non scientific, however it gives me a good gauge for how close to clipping I am. Labelling such a scale in Volts is kind of awkward and non portable, but an approximate conversion to amplifier power is familiar.

My midrange drivers are low efficiency, and they need considerably more power.
None of this takes the efficiency and thus the loudness into account, and it is not meant to.

I was also interested in seeing if and how much peak power and average power differs for the different frequency ranges. That comes into the bargain.

The idea for this box goes back to a design by J. Linsley-Hood, who too wanted an indicator for the available headroom too, although the practical realization was entirely different:

QuoteI use the term "watts" in this context very loosely, in that what one is really referring to is a p-p voltage swing, which could only be related to watts if one knew the RMS equivalent value - very difficult to determine for music waveforms - and if one's loudspeakers were truly resistive loads of a known value. Nevertheless, the hi-fi industry has grown up around the use of this terminology, and I must do the same.

- Build a Peak drive indicator, by J. Linsley-Hood, Hi-Fi News & Record Review, p.63ff, Oct. 1980.

So you may call that amateurish, but it serves the purpose.
Anyway, the purpose of my original post was to illustrate the wrong perception of loudness and amplifier power by telling the amusing story, and not to claim re-invention of the wheel.

It was that you were saying things in such a way that you did word them in regards to being scientific even with prefacing it with it not. When you start using the unique dialect to certain formal fields, it's still taking responsibility for those terms under the effective understanding in that field.

When you say the voltage would tell you when you were close to clipping, it was a "metric" you had created based on the gear you smithed together to show you some form of measurement.
In truth, that is the basis for all sophisticated, recorded science. Build something that generates information that is consistent in relationship to what you're also witnessing and then refine it.

In engineering, we tend to create a theory, build something from our imagination based on that theory, and if we successfully generate the effect we were envisioning, we refine it by applying staples of science because of where the world is at in technology.

With an 8 ohm impedance for your device though, you're seeing a lot of current. Without seeing the device, I doubt it was actually 8 ohms and much higher. There's also the fact that because of how you're obtaining your signal into those devices, if that device clips the active semiconductors or their passive diodes inside, it's also going to be witnessed by your speaker.
Whatever one experiences, so does the other.

I would bet your gizmos are far higher in resistances to see a large voltage drop but not current. If you're generating theoretically 100 watts, that's surely 3 to 4 amps of current.
Your VAC output is likely to be approximately 20 to 50 volts depending. Current for a 100 watt amp will typically be somewhere between 1.5 to maybe 3-4 amps and of course, with the voltage within the range I gave so it's calculated to approximately 100 watts.

In terms of isolating your monitor setup, it's much better to sample the signal with an incredibly high resistance and then increase the amplification within your device, design a driver that samples off that amplified signal to control the visual monitor, and so if you were to max blast your amplifier and speakers, if something distorted within your gizmo, that huge input impedance would make it totally inaudible within the speaker.
Just finding it within the speaker's signal with diagnostic equipment would become a pretty difficult task and possibly impossible.

I had fun as a hobbyist, but going to school freed my mind allover again and gave me a far more complex medium to create in than music and I'm a symphonic shredder that can hold my own against the biggest names on Earth. I have a style that no body sounds like, not even slightly, and invented a technique that's never existed I call Dypeggios.
There are much better guitarists, but I can still outplay them if that makes sense.

Anyway, I'm neck deep in my own company development and hopefully will launch my guitar and general audio equipment as planned by December this year. I have 3 preamp stages nearly complete that are out of this world. Instead of claiming tube emulation, I outright just configured the transistors to physically do the same thing as tubes and what do you know, unlike every tube emulator, simulator etc. out there that has ever existed, these simple circuits sound indiscernible from tubes.

They fizzle, they zing, they glitter when you hit pinch harmonics instead of grind. It's outright comical to how simple that is, but I'm digress and boasting. My passion for creating in electronics opened up the universe to my control.

Quote from: DrGonz78 on April 22, 2026, 11:48:32 AMPersonally I use metal or plastic clamps or zip ties to secure components.

That's what I prefer with my own builds too. I remember BTW seeing large cement resistors being held  with a soldered piece of copper wire (connected to nothing of course).

Quote from: DrGonz78 on April 22, 2026, 11:48:32 AMBut that costs more money than the company would ever be willing to spend.

Exactly. They are saving at all cost. How much more effort labor-wise and cost-wise would it be to make it properly?
But such a unit may last longer and be serviceable - beware of that.
Such an approach is reserved to the Military.

I totally agree with you, although I don´t know what your overall message is and whom you direct this towards.

As far as my little box goes, I made quite clear that this is non scientific, however it gives me a good gauge for how close to clipping I am. Labelling such a scale in Volts is kind of awkward and non portable, but an approximate conversion to amplifier power is familiar.

My midrange drivers are low efficiency, and they need considerably more power.
None of this takes the efficiency and thus the loudness into account, and it is not meant to.

I was also interested in seeing if and how much peak power and average power differs for the different frequency ranges. That comes into the bargain.

The idea for this box goes back to a design by J. Linsley-Hood, who too wanted an indicator for the available headroom too, although the practical realization was entirely different:

QuoteI use the term "watts" in this context very loosely, in that what one is really referring to is a p-p voltage swing, which could only be related to watts if one knew the RMS equivalent value - very difficult to determine for music waveforms - and if one's loudspeakers were truly resistive loads of a known value. Nevertheless, the hi-fi industry has grown up around the use of this terminology, and I must do the same.

- Build a Peak drive indicator, by J. Linsley-Hood, Hi-Fi News & Record Review, p.63ff, Oct. 1980.

So you may call that amateurish, but it serves the purpose.
Anyway, the purpose of my original post was to illustrate the wrong perception of loudness and amplifier power by telling the amusing story, and not to claim re-invention of the wheel.

Personally I use metal or plastic clamps or zip ties to secure components. I use a dab of silicone inside capacitor doghouse boxes in fender tube amps. When I open up some huge bass amp and I see glue boogers globbed everywhere I get fight or flight instinct. I really would like to see a zip tie carefully around the circuit board with holes to wrap and secure a huge cement wire wound resistor. Perhaps these zip ties held a heat sink device to also help dissipate heat. But that costs more money than the company would ever be willing to spend. So they at least try by squeezing a bunch boogers everywhere with little regard for any trouble it actually causes.

Quote from: aquataur on April 21, 2026, 11:15:32 AMI'll tell you a funny anecdote for your delection.

About 30+ years ago I had made an active loudspeaker system consisting of two satellites (mid-treble) and a subwoofer. This was made according to a Siegfried Linkwitz design.
I had bought 60W modules to power all 5 speakers, but at the time I was not very proficient. Some decades later I threw the electronics away and replaced them with DIY class-D modules (kits). That worked great.

Just I did not know what power they were outputting. In fact I was not interested in the power, but rather in the voltage headroom, in order to avoid them clipping.

So I devised a small µC operated analyzer that drove 10 LEDs, to show average and peak hold values, to give me a clue where I was. One for each amp, so 5 of those in total.

The unit was tested thoroughly on the bench. After installing, the LEDs did not register.
They did not show anything. Until I found out, that even after playing in the living room at party loudness levels (which you would not like to be subjected to for long), the power output was still below the threshold of the display: 1Watt. You would not believe how loud 1W is.

I then changed the code and installed a 10:1 "loupe" that automatically reverts to normal once the threshold has been triggered, before it falls back with a delay of a minute.

The measurement was by no means scientific, just a conversion using an 8 Ohm resistance, but it gave you a very good indicator.

The interesting thing was that the dance of the LEDs remained the same (the display being logarithmic), regardless of the power. It also showed that, beyond that 1W point, the wattage was climbing shockingly fast despite a perceived mediocre increase of loudness.

We all know that but it comes as a surprise when you encounter it.

You never caluclated the power for any of this to make sense because it doesn't. I'm an electronics engineer, not a DIY guy which all due respect, is a community with a lot of nonsense and pseudoscience in how things work, what information means, the literally quantum theories of materials, circuits etc. etc. etc.

Without simply clamping the amplifier, getting a voltage and current reading with a 1 Khz sine wave test tone, there's not much to be said other than you made a cool DIY project that worked well enough but you have no effective understanding of.

I've been there. I built many things like this when I was a DIY nomad for about 6 years but eventually, I got sick of now truly understanding and all the nonsense from forums and social media fraudsters and I went to a technical college that teaches the patent science when I was 32.

Every single device and project is just and endless universe in itself. There's endless options, endless details to modify through D.C. and A.C. analysis, probing every circuit node for a variety of test equipments producing data and then modifying things based on that.

1 watt is very loud through a very light weight cone with a modest magnet size and a very hot signal pouring into it within it's bandwidth where the cone's damping factor doesn't result in physical distortion.
1 watt under the right circumstances will give you permanent hearing loss.

Wattage in itself is a misgiving dataset because inductors and therefore speakers do not see wattage, they see VAR; Volt Ampere Reactance. This is calculated based on the phase angles of voltage and power meeting in timing at a very certain point, and that chronological synchronicity point tells you the peak resonant frequency, the VAR which we can relate virtually to wattage, and the effective bandwidth to power efficiency based on the circuits Q.

It's just a very complicated process in terms of what you cannot learn through DIY study in 99.99999% of cases. You have to go through very structured curriculums of some form and commit to them. Fulfill them in 100% of requirements and if possible, take quizzes and then tests on them.
In the end, there's no supplementing a curriculum with DIY wandering and misunderstandings based on personal ideas and association of those ideas with science based information you simply don't understand.

Udemy and the other online non-credit colleges have a lot of great courses that will take you the distance to being an electronics engineering, but take that with a grain of salt because they all teach "conventional current theory" which is a theory in particle physics that's unfortunately a pseudoscience.
You'll be a competent engineer but never truly a scientist. Technical colleges teach the electron model for mass, energy and motion of all phenomenon in the universe, not just technology and electro-chemical events in nature or even manmade industrial processes.

Learning conventional theory really puts a despicable set of shackles on the student's brain. It can certainly be overcome after the fact, but you have to really want it. It doesn't just correct a shitload of electrical theory they teach wrong but all physics from quantum to classic scale and the countless things they have wrong.

Every field of science today is based on the proton model of mass, energy and motion for understanding all phenomenon in the universe and it's an ass backwards pseudoscience equivalent to shoving food in your crack and expecting it to come of your mouth as feces.
I suppose when all of these theoretical physicists in media make all sorts of ridiculous claims based on totally fraudulent theories, that is virtually the crap pouring right out of their mouths.

This is why technology has been at a near dead stand still for decades.