replacing 2n3055 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 23rd January 2004, 02:04 PM   #1
vazzy is offline vazzy  Australia
diyAudio Member
 
Join Date: Nov 2003
Location: NSW
Default replacing 2n3055

Hi,

I have searched the forums and have found that its possible to replace the 2n3055 with the mj15003/mj15004, however im unsure of the specifics.

Is it a direct swap or are other modifications required? Also how much improvement in sound can i expect (or is this dependant on the amp) ?

The amp i will be doing this to is the sonab p4000, the schematic can be found here...
http://www.cse.unsw.edu.au/~vosm145/sonab3.GIF

generally what other areas should i look into to improve sound ?

many thanks,
vas.
  Reply With Quote
Old 26th January 2004, 10:18 PM   #2
diyAudio Member
 
Join Date: Dec 2003
Location: Orange County, CA
Default 2N3055 sub

The only problem doing this sub is that the new transistors have a higher gain bandwidth product and they may oscillate. You should check the amplifier with an oscilloscope after making the replacement to make sure there is no high frequency oscillation on the output. Of course, you will have to reset the bias as well.

As for sound quality, you may not hear any difference as any amplifier that used the 2N3055 probably has so many other compromises built into it, you will likely not get any real benefit from doing this. The fact that it is a quasi-complementary design alone is enough to eliminate it from true Hi-fidelity consideration. If you convert the amp to a true complementary design, you had may as well just get something a bit more modern.
__________________
Dan Fraser
  Reply With Quote
Old 27th January 2004, 09:29 AM   #3
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Arrow Re: 2N3055 sub

Quote:
Originally posted by dmfraser
The fact that it is a quasi-complementary design alone is enough to eliminate it from true Hi-fidelity consideration. If you convert the amp to a true complementary design, you had may as well just get something a bit more modern.
Regarding Quasi-Complementary design :
ACC to my opinion as well as experience
A QUASI-COMPLEMENTARY WILL PERFORM MORE THAN ANY TRUE COMPLEMENTARY DESIGN IN TERMS OF:
1 THERMAL STABILITY
2 EQUAL SUPPLY LOADING
3 EQUAL HEAT DISSIPIATION IN UPPER AND LOWER SIDE RAIL DEVICES
4 SIMILAR SIGNAL TRANSFER FUNCTION COEFFICIENT
5 BETTER SYMMETRICAL [ASYMMETRICAL] VOLTAGE SWING.

SECONDLY,
Mr.VASSY
I have reviewed ur schematic and i can say that u can replace the 2N3055 with mj15003 very well without any Oscillations

Regards
Ampman
  Reply With Quote
Old 27th January 2004, 10:11 AM   #4
diyAudio Member
 
Join Date: Jul 2003
Location: Newcastle, Australia
As already pointed out by dmfraser, there probably won't be any difference in sound quality. The MJ15003 can be directly substituted, and is usually done for increased reliabilty or for driving lower impedance loads (MJ15003 has higher power ratings). Oscillation can be a problem with these devices - I note from the schematic that the output transistors are not mounted on the circuit board, so make sure the three wires to each are tightly twisted together.

To inrease drive capacity into lower impedance loads, a better substitution my be the 2N3773 - these are very robust and cheap.

Sound quality has to do with the overall circuitry of the amp, and major redesign work (other than output transistor type) would have to be implemented to achieve this.

Cheers
  Reply With Quote
Old 27th January 2004, 04:07 PM   #5
diyAudio Member
 
Join Date: Dec 2003
Location: Orange County, CA
Default If its not broken

Actually, if its not broken I suggest doing nothing. Changing the transistors will not improve the sound quality and may introduce their own problems. You won't get any more power as the power output is set by the power supply voltage and since the rest of the circuit won't change, the sound quality will not improve.

As for quasi designs, the transfer characteristics between the positive and negative sides are radically different. This means that while it can measure OK, due to feedback, the transient response of a quasi design will be radically different on the two sides of the waveform, specially with slow devices like the 2N3055 or 2N3773.

As for unequal heat dissapation or power supply loading between the two supplies, who cares. That's the original designer's problem to take care of these.

We went to complementary designs deliberately. They sound more musical. They give better (and more symmetrical) transient response.
__________________
Dan Fraser
  Reply With Quote
Old 27th January 2004, 04:41 PM   #6
Zombie is offline Zombie  Sweden
diyAudio Member
 
Join Date: Feb 2003
Location: At home
Hello!
This article is relating to a class A design:
http://www.tcaas.btinternet.co.uk/jlhtrans.htm

It seems pretty positive to replace 2N3005 with the MJ15003 and increase in osund quality, but that maybe only applies to class A?

I have also been thinking about making my old Quad 303 complementary as described here - the very last part: http://www.net-audio.co.uk/quad303upgrade.html

Can one expect an improvement in sound quality with the 303, too, as dmfraser suggests with other designs?

Furthermore, I'd then like to try MJ15003 and the complemetary MJxxxxx in the rebuilt 303...

What do you think?

Cheers,
T
  Reply With Quote
Old 27th January 2004, 04:56 PM   #7
diyAudio Member
 
Join Date: Dec 2003
Location: Orange County, CA
Default Sound Quality

Unless the open loop feedback structure and the open loop frequency response is modified to take advantage of the new devices, the improvement will be very minor if any. Say what you want about the 303 but it is a dinosaur of a design from an era before we discovered why the early transistor amps sounded so bad compared to tube amps. Transistor amp designers dit not learn how to make a really musical amp until the late 70s when the work of Matti Otala and others concerning transient intermodulation distortion worked its way through the design community. There are still amplifiers not aware of this.

The latest work on class D drivers like the Texas TAS5012 with no feedback at all has promise to bring back non-feedback amplifiers that approach the musicallity of tube amplifiers.

Go ahead and modify your 303 if you like. It may even sound better to you but unless the change involves changing the capacitor values in the feedback loop and increasing the values of the emitter resistors of the driver and pre-driver stages, you're not changing much. Generally there is so much to change to truely improve an amplifier, you're doing little but salvaging the case and power transformer. Anything less is like stirring apot of soup and declaring it improved.

By the way, I built a lot of horrid sounding amplifiers in the 70s my self. Until I discovered the work of Otala and Leach. Their . research improved my amplifiers so much. Even the eearliest Leach amplifier designs were such an improvement I suggest them to anyone wanting to build an amplifier.

Some of the nicest sounding high power amplifers in the world re the Renkus-Heinz P2xxx and P3xxx series. However, their rack amplifiers have been discontinued as they have been chased out of the market by cheap Chinese made amplifiers. You can even find some of the schematics at www.rh.com and www.schematicsforfree.com.
__________________
Dan Fraser
  Reply With Quote
Old 27th January 2004, 05:12 PM   #8
sam9 is offline sam9  United States
diyAudio Member
 
sam9's Avatar
 
Join Date: Jun 2002
Location: Left Coast
"any amplifier that used the 2N3055 probably has so many other compromises built into it"

There are a lot of things in addition to choice of output device that cxontribute to overall amp quality. There is some truth in that if you were to make a random selection from all amps still in service using these devices, the likelyhood is that you would select something so-so. However, if you work well with in the limits of the device and use good topology for the rest of the amp, you can construct something no one needs to be embarrased about. Wheter this applied to the unit the original poster has is another story.

"The fact that it is a quasi-complementary design alone is enough to eliminate it from true Hi-fidelity consideration"

Complementary topology has the **Potential** for superior performance but achieving that potential is not automatic. The selves of your local discount chain are filled with complementary output sections that are nothing special. At the same time there exist excellent amps from years past of a quasi designs that are still fall easily into the Hi-fidelity category. It may be true that it is easier to design a good complementary topology amp.


Speculation: Had NPN/PNP output pairs be available from the beginning it is concievable a a couple of decades later someone might be touting the theorecical superiority of using identiclal output devices. Audio is as subject to fashion and a passion for "new" vs. "old fashioned" as the cloth trade.
  Reply With Quote
Old 27th January 2004, 05:19 PM   #9
Zombie is offline Zombie  Sweden
diyAudio Member
 
Join Date: Feb 2003
Location: At home
Hello dmfraser!
Yes, I know about the TIM and DIM and IIM etc. They were hot stuff when I was in secondary school. I even tried to measure for TIM in our primitive physics lab.

I'm also well aware that almost any old or modern MOSFET design sounds much, much better than a 303...

It's just that I like to see what one can do to improve a certain item. And I think that the 303 is an intersting piece of equipment and it stands well when listening "normally" (whatever that is) to my Quad IIs (refurbished).
Of course, I don't have the knowledge that you guys have, that's why I ask for advice...stupid questions to some, but the answers are interesting to me...

Actually the remarks you made about what would be needed to stir up the 303 are interesting. Have you any concrete suggestions one could try, you mention a feedback cap and emitter resistors...?

Cheers,
t
  Reply With Quote
Old 28th January 2013, 01:54 PM   #10
diyAudio Member
 
Join Date: Oct 2009
Location: Hamburg
I guess all concerned know this already but the Quad 303 power amplifier sounds so much better with a capacitor replacement and an adjustment of the bias. I also have to say the Quad 303 sounds to my ears very good. Ok the Quad 306 has better bass than all my other amps but the 303 has a lovely sound particularly in the mid range and looks like a peace of classy 1960's industrial design which I guess it is. The main problem with my 303's is the slightly high hiss it has, even compared to the Leak Stereo 30+, and as I have 3 of them and 2 are upgraded and from the outside I cant tell them apart I do have to fix up that last one.

Regards

Owen
  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
2n3055 Ford_V6 Solid State 33 1st September 2012 07:06 AM


New To Site? Need Help?

All times are GMT. The time now is 03:31 AM.


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