Your fat line appears to connect the speaker to the power supply center. You can't do that, the speaker cap would be subjected to negative voltage and short or blow.
If you connect the speaker to the negative rail, the the cap is okay. You don't have to use the center tap of a toroid transformer, you can treat it as a single winding transformer by connecting the upper of one winding to the lower of the other winding. That makes double the voltage at single winding rated current. Modern toroid transformers have two independent windings.
Note two 33 v windings series get 1.4*66 or 92.4 vdc peak. That is too much. You had better parallel the two windings for 1.4*33 or 46.2 v. Great for 4 ohm speakers, a little low for 8 ohm speakers.
BTW if you want the very best of these 50 w quasi-comp amps with a speaker cap, check out this thread: Retro Amp 50W Single Supply
LKA today just posted his measurements of his version which are <.002% HD at 1 w, 5 w, and 50 W. Retro Amp 50W Single Supply
My version of the AX6 runs on 70 v single supply, 6.25 A transformer, with MJ15003 output transistors. I got 70 W out of it for 5 seconds on two 8 ohm speakers. MJ21194 should work too. Don't omit the heat sinks on drivers & VAS for this level of wattage from a single pair. I found 30 mhz ft drivers & vas are required to get good high frequency sound out of it. Like MJE15028/29 . TIP41c/42c (6 mhz) had dull highs compared to 2n5320/22 (50 mhz).
If you connect the speaker to the negative rail, the the cap is okay. You don't have to use the center tap of a toroid transformer, you can treat it as a single winding transformer by connecting the upper of one winding to the lower of the other winding. That makes double the voltage at single winding rated current. Modern toroid transformers have two independent windings.
Note two 33 v windings series get 1.4*66 or 92.4 vdc peak. That is too much. You had better parallel the two windings for 1.4*33 or 46.2 v. Great for 4 ohm speakers, a little low for 8 ohm speakers.
BTW if you want the very best of these 50 w quasi-comp amps with a speaker cap, check out this thread: Retro Amp 50W Single Supply
LKA today just posted his measurements of his version which are <.002% HD at 1 w, 5 w, and 50 W. Retro Amp 50W Single Supply
My version of the AX6 runs on 70 v single supply, 6.25 A transformer, with MJ15003 output transistors. I got 70 W out of it for 5 seconds on two 8 ohm speakers. MJ21194 should work too. Don't omit the heat sinks on drivers & VAS for this level of wattage from a single pair. I found 30 mhz ft drivers & vas are required to get good high frequency sound out of it. Like MJE15028/29 . TIP41c/42c (6 mhz) had dull highs compared to 2n5320/22 (50 mhz).
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Not THAT one, horrible design.
1) you are sending -32V to signal source through wire shield/"ground" , WTF?
2) amp will be horribly mis-biased
As-is, it expects *single* +24V supply so even single +32V is already wrong; +/-32V is nonsense
3) Vas/input transistor load is not bootstrapped so that alone is a sign of poor design
4) input impedance is very low and hard to drive.
5) didn´t google datasheets but using same type transistor K645 both as low current (couple mA) input and high current load drivingn power output sounds WRONG.
In a nutshell, the answer is NO.
1) you are sending -32V to signal source through wire shield/"ground" , WTF?
2) amp will be horribly mis-biased
As-is, it expects *single* +24V supply so even single +32V is already wrong; +/-32V is nonsense
3) Vas/input transistor load is not bootstrapped so that alone is a sign of poor design
4) input impedance is very low and hard to drive.
5) didn´t google datasheets but using same type transistor K645 both as low current (couple mA) input and high current load drivingn power output sounds WRONG.
In a nutshell, the answer is NO.
Mmmmhhhh, it´clearly labelled "-32V"
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I've been researching and found the original circuit.
РадиоКот :: Усилитель на совецком хламе
It is single source +32VDC. I understood what you mentioned, grateful for the feedback. My doubt was the possibility of eliminating the negative supply of a symmetric amplifier, turning it into a single and logical source, installing the output capacitor for the speaker. By coincidence I was already reading about the Apex AX6. Thank you all.
РадиоКот :: Усилитель на совецком хламе
It is single source +32VDC. I understood what you mentioned, grateful for the feedback. My doubt was the possibility of eliminating the negative supply of a symmetric amplifier, turning it into a single and logical source, installing the output capacitor for the speaker. By coincidence I was already reading about the Apex AX6. Thank you all.
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The circuit from РадиоКот :: Усилитель на совецком хламе is a very basic one. Even kits for schoolboys sold in Eastern Europe had a more advanced schematic.
Here you'll find a nice capacitor coupled version and here some additional information including BOM and pcb design (in the OTL30.rar package).
Additional information (Reginald Williamson - The Twin 20 - Power amplifier - Hi-Fi News - August 1967 and: Reginald Williamson - Postscript to the Twin 20 - Power amplifier - Hi-Fi News - February 1968).
Here you'll find a nice capacitor coupled version and here some additional information including BOM and pcb design (in the OTL30.rar package).
Additional information (Reginald Williamson - The Twin 20 - Power amplifier - Hi-Fi News - August 1967 and: Reginald Williamson - Postscript to the Twin 20 - Power amplifier - Hi-Fi News - February 1968).
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Of course it is: these amps were all the rage in the late 60's, early 70's. Your example has one or two drawing mistakes, but it is evidently designed for a single supply, and could actually work
I had collected a number of examples for Daniel:
A collection of vintage, single supply, low to medium power amplifiers for Daniel
I also designed one or two ad-hoc examples, having some advantages over historic circuits:
Old-fashioned amplifiers with a new twist (1)
Old-fashioned amplifiers with a new twist (2)
Easy-MOS is a simplistic, efficient and evolutive all-MOS amplifier for beginners
That scheme from the first post was sabotaged with that black stripe. I used it for the example of using simple font.Not THAT one, horrible design.
1) you are sending -32V to signal source through wire shield/"ground" , WTF?
2) amp will be horribly mis-biased
As-is, it expects *single* +24V supply so even single +32V is already wrong; +/-32V is nonsense
3) Vas/input transistor load is not bootstrapped so that alone is a sign of poor design
4) input impedance is very low and hard to drive.
5) didn´t google datasheets but using same type transistor K645 both as low current (couple mA) input and high current load drivingn power output sounds WRONG.
In a nutshell, the answer is NO.
Mmmmhhhh, it´clearly labelled "-32V"
I am very grateful to the others for the tips / ideas. I'm seeing my possibilities here because the market is contaminated by fake semiconductors. SDS to all
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What market are you struggling with -- Ali Express? Ebay? locals in your area?
I would try talking to reputable distributors -- surely there is ONE that is willing to ship to your neighborhood. All have a full service web site these days, and I think most still maintain toll-free 800 phone numbers.
Digi-Key and Mouser are exceptional, and have quantity-one prices for most things. Arrow, Farnell, Avnet, RS are probably just as good, but I have less personal experience with them. There are surely others that I don't know about.
The frustrations and diagnosis/troubleshooting mis-directions that result when you can't trust the parts to meet spec, are way more than I can tolerate.
Cheers
I would try talking to reputable distributors -- surely there is ONE that is willing to ship to your neighborhood. All have a full service web site these days, and I think most still maintain toll-free 800 phone numbers.
Digi-Key and Mouser are exceptional, and have quantity-one prices for most things. Arrow, Farnell, Avnet, RS are probably just as good, but I have less personal experience with them. There are surely others that I don't know about.
The frustrations and diagnosis/troubleshooting mis-directions that result when you can't trust the parts to meet spec, are way more than I can tolerate.
Cheers