how choose a transistor to have a better sound - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th April 2010, 06:14 AM   #1
diyAudio Member
 
Join Date: Aug 2007
Default how choose a transistor to have a better sound

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
  Reply With Quote
Old 11th April 2010, 06:38 AM   #2
diyAudio Member
 
Captain archer's Avatar
 
Join Date: Apr 2004
Location: Weert
Send a message via MSN to 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
  Reply With Quote
Old 11th April 2010, 06:41 AM   #3
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
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.
  Reply With Quote
Old 11th April 2010, 06:56 AM   #4
diyAudio Member
 
Captain archer's Avatar
 
Join Date: Apr 2004
Location: Weert
Send a message via MSN to 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
  Reply With Quote
Old 11th April 2010, 09:46 AM   #5
diyAudio Member
 
Join Date: Aug 2007
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 "

Click the image to open in full size.

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
  Reply With Quote
Old 11th April 2010, 11:27 AM   #6
Mooly is online now Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
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.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 11th April 2010, 11:48 AM   #7
diyAudio Member
 
Join Date: Aug 2007
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
  Reply With Quote
Old 11th April 2010, 12:11 PM   #8
Mooly is online now Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
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 ?
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 11th April 2010, 01:14 PM   #9
diyAudio Member
 
Join Date: Aug 2007
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
  Reply With Quote
Old 11th April 2010, 01:17 PM   #10
diyAudio Member
 
Captain archer's Avatar
 
Join Date: Apr 2004
Location: Weert
Send a message via MSN to 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
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Can bias transistor mount on top(body) of output transistor?? Leolabs Solid State 23 16th February 2008 12:35 AM
What to choose?! rinx Multi-Way 12 29th September 2007 10:23 PM
Help me choose please fighi77 Tubes / Valves 12 10th June 2007 01:35 AM
What to choose ? ToG Chip Amps 20 16th November 2004 02:36 PM
Transistor sound PanzerLord Solid State 73 12th December 2003 01:17 PM


New To Site? Need Help?

All times are GMT. The time now is 12:51 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2