I wanted to have an amp chassis I could put on the bench and maybe accomplish a few sorely needed achievements
-be able to look at any component and identity it moreover locate it on the schematic
-identify the components of the power supply
-determine the route of the signal path
-do some signal tracing
The amp works I tried it a while back it is missing a speaker
Beautiful ain't it
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Well that didn't take long (I had to be careful not to scratch the Tolex)
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And inside on the bench
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Doesnt look too intimidating but it just occurred to me that TDA 2040 or whatever it is may eliminate quite a few components
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Maybe this is the bridge rectifier
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That white cable is some type of three wire cable I just attached for makeshift speaker wire
Also I see an 8 DIP wondering what that is but all good in the hood because I get to find out :tu:
EDIT: They are two 4558DD
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They must be for the cheese that goes CRUNCH
As far as the signal path well at least I think it begins at the input jack and ends at the speaker xP
There is a switched potentiometer (or whatever you call a dial that turns on and off 8| ) for the overdrive gain
I thought maybe I could check the + and - voltage of each 4558DD with the gain off and on
But I got the same reading with it off or on it appears they are powered up at all times
Then I checked the rectifier diodes and looks like we have a bipolar power supply xP
Whose voltages show up on the TDA
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I think I may look at these diodes I'm curious I always think these clear colored diodes are zeners but sometimes they are (switching?) diodes idk
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But looking at the schematic for the 10xl and 15xl kindly provided by G1 they look like ordinary diodes
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So might be time for a look at the TDA and see why it needs diodes around it xP
Seems like this is gonna be a good project I thank you for your help :dbtu:
These integrated circuits op amps chips etc must be revolutionary because it occurred to me there is not one transistor in this amp :loco
My take on the diodes is that are "clipping diodes".
A poor way of creating distortion.
Yes sir thanks that's cool that you mentioned that
I did a search here about 4558 and read quite a bit including one of your experiences :tu:
Then some members were discussing diode clipping I got pretty excited wanting to experiment with those type circuits xP
The diodes D6 and D7 are for 'protection against output voltage spikes' and are included in the datasheet circuit (attached).
If the output swings more than approx. 0.7V above or below the supply rails, they conduct and clamp the output to the rail voltage.
D8 and D9 on 10XL schematic appear to be clipping diodes that are switchable for whatever "SCG" stands for.
Thanks for the clarification G1.
When G1 said that I was like oh hell yeah of course it does :tu:
Then later on I was "hmm I wonder what that means in English?" :grr xP
So I looked at the data sheet and found this but I think this is something different
Furthermore, the device incorporates an original
(and patented) short-circuit protection system
comprising an arrangement for automatically
limiting the dissipated power so as to keep the
operating point of the output transistors within
their safe operating range.
So I said well just make a diagram and try to figure it out so here goes xP
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Hope I didn't get it backwards my mind gets turned around trying to figure out those diodes
Yes Those are to protect chipamp from speaker flyback voltage when amp is clipping.
SCG means Sequential Cascaded Gain and is a fancy name for plain old distortion.
Marketing guy has to earn his salary :lmao:
Quote from: saturated on August 27, 2026, 07:13:35 PMSo I looked at the data sheet and found this but I think this is something different
Furthermore, the device incorporates an original
(and patented) short-circuit protection system
comprising an arrangement for automatically
limiting the dissipated power so as to keep the
operating point of the output transistors within
their safe operating range.
That is something different and internal to the TDA2030. The 2 diodes are external and are mentioned in table 5 (page 10 of datasheet pdf).
I noticed in one of your photos, on your circuit board there are 2 diodes D9 and D10. They have the zener symbol marked on the board underneath them. As there is no such thing shown on the 10XL schematic, I guess it does not match your unit. Yours probably has zeners for the +/-15V supplies.
Yes sir thanks :tu:
I decided to make life easier by getting a BNC to phono jack cable
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Before I was using jumpers and alligator 🐊 clips etc which is cool I reckon you guys do it in two shakes of a lamb's 🐑 tail but I wanted to try and simplify and expedite some of my ventures yeah so now I can just plug and play
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And I can focus on probing around looking for signal xP
In fact at this very moment I'm listening to the soothing sound of a 2300 hz sin wave xP
Seems like a good idea. I tried something similar with a 12w Orange that was glitchy. I tried repairing some pcb traces and tried to draw a schematic. I learned a lot but ended up just saving the transformer and the speaker.