how choose a transistor to have a better sound

[Ground Zero]

Hello

i have a technical induiries please

I would know what caracteristics i must see in a bipolar and mos-fet transistor to have the better sound ?

Can you explain me that please? because in the datasheet there is a lot of think that i don't understand except the main vceo, vcbo etc...

And why old amplifier have a better sound like tube amp (i see a post who talk about that but i need more information )

i have an old etage amp for a guitar with one "T03" MJ4502 and one "T03" Mj802 and the sound is great do you think T03 transistor are better ?

Thanks for your help

[Captain archer]

how choose a transistor to have a better sound

Well a transistor doesnt have a particular sound it is determined by the circuit around it.
although a higher Tf (transistion frequency) and lower internal capacitances (see datasheets) alow the device to preform better in high speed circuits
I renectly build a headphone amp with 50 year old sluggish germanium transistors but it still sounds fine.
And the case of an transistor doenst determine the sound either it only makes a difference in size and heat dissipation.
T03 stile transistors can dissipate alot of heat but the are large and difficult to mount and isolate from each other.

The fact that old amps sound good or different is entirely determined by the circuit topology used in that time period

circuits are different now and have become more complex and better so al kinds of distortions have been minimized and thus the sound changes.

Greets captain archer

[Perry Babin]

In most solid state amplifiers, significant negative feedback is used and will compensate for differences in transistors, making the transistors generally irrelevant as long as they can withstand the operating conditions (current, voltage, power dissipation...). In effect, you get out of the amp, precisely what you feed into it (as far as sound quality is concerned).

For most solid state amps, you could insert a low value resistor (~2 ohms) between the output transistors and the speaker terminals/load and if the feedback for the amp was taken at the speaker terminals (beyond the resistor) the amp would sound precisely the same. Only the power output at clipping would vary (slightly lower with the resistor in the circuit). If you had that same circuit but took the feedback from the transistor side of the resistor (instead of the speaker terminal side of the resistor), the amp would sound significantly different. The negative feedback cancels most of the differences that most of the devices in the circuit can introduce. You could try 100 different output transistors and if none caused any serious problems like oscillation or crossover distortion (due to improper biasing), they would all sound the same.

Tube amps use little or no feedback and many things (transformers, tubes, biasing...) will effect the sound. You'll even find that some tube amps sound great with certain speakers and not so good with other speakers. Tube amps are very different from solid state amps.

[Captain archer]

Perry Babin is right tube amps are different
and remenber in a tube amp the transformer is the thing that colors the sound the most, especially if there is almost no feedback apllied.
and in a datasheet you could also look for noise factor in DB (how much noise an transistor generates) so if u use them i a low noise situation like a phono correction amplifier, the noise of the transistor wont interfere with the already so small and teeny signal that the phono element gives.
and one other thing is that tubes age and there characteristics change with age and thus the sound changes with it.
Transistor in genaraly dont age at least there specs dont change with age so after 30 years of use a transistor will still sound the same as it did when it leaved the factory.

greets archer

[Ground Zero]

hello

Thanks for your explaination

This is a photo of amp for guitar with a great sound that works well with any type of music from elvis presley to rap or techno music "with elvis is great "



I think to use it on my smps for a car audio amp
but i need to change some components because there are old

we can see 4 little transistors 2x BD529 and 2 who have 3 code color (purple, red, white)

i don't know if i can find substitution

Have you got an idea please ?

Thanks

on the pcb amp i can see this code: 410CST1241 ELKA
i don't know who manufacture this amp for guitar

[Mooly]

The three colours are the underside of the transistor The type number is on the top.

Substituting the semiconductors will not alter the sound at all and the circuit may actually rely on the (relatively) poor HF performance of the outputs for example to help maintain stability.

[Ground Zero]

Thanks Mooly

Yes i unmount the transistor and his number is MPS U57 i don't know this transistor

for Substituting the semiconductors i prefer not for changing the sound of the amp just because they are old and i prefer new components

have you got an idea to change MPS U57 and BD529 please

[Mooly]

These are old devices... the MPSU57 is a complement to the BD529. Both are 100 volt 2 amp devices, with a power dissipation of 1 watt in free air.

And by modern standard they are "slow" with a 50mhz ft.
The BD238 is a replacement for the MPSU57.

There will be lots of possible OK substitutions, even TIP41C and TIP42C although check the pinouts.
Is it worth it ?

[Ground Zero]

Thanks Mooly

For the ft parameter in a transistor if i understand, more important is the value Ft better is the transistor ?

"sorry for my english i hope you understand "

Thanks a lot

[Captain archer]

I would leave those transistors on the pcb if they work, it it not worth it at all to change them better change the electrolythic capacitors on the pcb these will have dried out after all these years and maybe the old carbon composition resistors they might have some moisture damage.
better change them for metal film resistors and those big white wire wound resistors have quite some induction better change them for some power film resistor.

Greets Nice amp by the way