Class A board DOA33. PSU Help!

Your DOA33 does run within 25 V - 35 V very well.
To increase the supply voltages significantly, you would have to replace BC413 and BC415.
3 x 150 Ohm-resistors set the current. You could the middle one replace by trimmer (500 Ohm), as example.
I would remove the last two diodes 1N914 (feedback), it will sound much cleaner.
To get more "smack" (sound) connect emitter-base MJE182 and emitter-base MJE172 - per resistor or wire. Better solution than the two 1N914.
You could replace both R33 (emitter-resistors) per other values to modify the sound: the higher the more naturalistic. The lower the duller, more brittle, tighter.
Attention: this one is a push-pull-design, 3 (1/2) steps: this one is not to use to listen music;-)-;
 
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Your DOA33 does run within 25 V - 35 V very well.
To increase the supply voltages significantly, you would have to replace BC413 and BC415.
3 x 150 Ohm-resistors set the current. You could the middle one replace by trimmer (500 Ohm), as example.
I would remove the last two diodes 1N914 (feedback), it will sound much cleaner.
To get more "smack" (sound) connect emitter-base MJE182 and emitter-base MJE172 - per resistor or wire. Better solution than the two 1N914.
You could replace both R33 (emitter-resistors) per other values to modify the sound: the higher the more naturalistic. The lower the duller, more brittle, tighter.
Attention: this one is a push-pull-design, 3 (1/2) steps: this one is not to use to listen music;-)-;
i have this doa33 circuit
doa33_skjema_mg-jpg.1102539
 

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I will use 2sc3421 2sa1358 instead of mje172/78View attachment 1102577View attachment 1102578
May be, 2sc3421 and 2sa1358 are wonderful choice. May be not very liveful, not very large, a bit artificial over clear colors, like dollhouse, very disciplined.
I would replace Q5 and Q6 with the same types as Q7 and Q8. To get less differences of "character" of parts in both halfwaves, in both strands of amps - to get more harmonic and cleanness in sound. (Or Q6 the same as Q1 and Q3, Q5 the same as Q2 and Q4)
MJE172/182 I did not hear yet.

I would remove C7, C8, C11, C12. Without replacement.
 
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A picture is often worth 1,000 words. You will probably find a video like this short example is enough to gain some clear understanding. Note that it's a US video and the primary windings are connected in parallel for 115 VAC. Wiring the primary windings for use in the UK, is in series for 230VAC and the sense or winding direction of the windings on the core really matters - follow the guide covering the wire colour code in the sales or packing info:
 
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May be, 2sc3421 and 2sa1358 are wonderful choice. May be not very liveful, not very large, a bit artificial over clear colors, like dollhouse, very disciplined.
I would replace Q5 and Q6 with the same types as Q7 and Q8. To get less differences of "character" of parts in both halfwaves, in both strands of amps - to get more harmonic and cleanness in sound. (Or Q6 the same as Q1 and Q3, Q5 the same as Q2 and Q4)
MJE172/182 I did not hear yet.

I would remove C7, C8, C11, C12. Without replacement.
What did you replace Q5 and Q6 with Q7 and Q8?
 
What did you replace Q5 and Q6 with Q7 and Q8?
Two half-waves but including two times the same character of two different parts, not 4 characters of 4 different parts: more harmony, cleanness, less noise, differences.
The same "character" of sound. Result of "streaming", "floating" - "current" does not describe the process. We have to understand "current": through materials, forms, modulated by resonances of materials...: same parts - nearly the same characters. different parts - very very different characters.
The ear does detect not "waves" only or amplitudes;-) The ear does detect differences at first. The ear does detect very very complex differences: signals. A measure per looking (oscilloscope) does not represent the audible character of parts and circuits and more. Not a bit. Zero!