Best 2N3055 alternatives Best 2N3055 alternatives - diyAudio
Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Best 2N3055 alternatives
Best 2N3055 alternatives
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
Thread Tools Search this Thread
Old 14th April 2013, 05:01 PM   #1
mart.s is offline mart.s  United Kingdom
diyAudio Member
Join Date: Dec 2008
Default Best 2N3055 alternatives

Hi I recently replaced a blown channel TR's on my Audio Innovations ALTO mk1 amp, the originals were ST 2n3055, I replaced the blown pair with CDIL 2n3055 which I don't think sound very nice compared to the ST2n3055. I did re-bias them as per the circuit diagram. Does this mean I have poor quality or fake transistors. I think the amp sounds really nice and would like to keep it, so (No jokes about the old design please)
I have also replaced the the output DC blocking caps and power cap.
I would like to replace all of the output transistors with better devices or at least keep them all the same like the ST brand. (Does anyone know where I could get some from in the in the UK) I have limited electronics knowledge unlike some of you fine chaps.
I would be grateful for any advice.
  Reply With Quote
Old 14th April 2013, 05:29 PM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
Mooly's Avatar
Join Date: Sep 2007
Best 2N3055 alternatives
The problem with the 2N3055 is that it is such an old device (historically) that you find the offerings available today are somewhat different spec wise. The ST device (according to the ST data sheet) has for example an Ft of over 3Mhz (on a par with modern devices) whereas I think of the original 2N3055 as struggling to reach 600khz.

The CDIL spec shows an hfe of 5 (minimum) which strikes me as appaling tbh

I'm thinking something like the OnSemi MJ21194G might be a suitable replacement.

  Reply With Quote
Old 14th April 2013, 05:56 PM   #3
terranigma is offline terranigma
diyAudio Member
terranigma's Avatar
Join Date: Feb 2007
BDY73 seemed to me just like an audio version of 2n3055. Almost all specs same but BDY one features higher gain.
  Reply With Quote
Old 14th April 2013, 06:14 PM   #4
Project16 is offline Project16  France
diyAudio Member
Project16's Avatar
Join Date: Nov 2012
Location: Cognac
Attached Images
File Type: png 2N3055.png (342.1 KB, 806 views)
  Reply With Quote
Old 14th April 2013, 07:43 PM   #5
mart.s is offline mart.s  United Kingdom
diyAudio Member
Join Date: Dec 2008
Thanks Mooly, So it looks like those CDIL trannys are pretty crap then, no wonder the right channel sounds terrible compared with the left (ST) I thought I had wax in my ear until I started mono comparisons with both ears.
So the ft is important like the hfe for good sound?
Do you think I would be better off changing all of them for the MJ21194G or just try and get some more ST's, I don't really want to chance blowing something if the values are to far out.
Before the right ch blew (Thanks to a mate who borrowed it) the sound has been pretty impressive for a cheap amp, the sound staging in amazing, I've never heard another amp like this that almost hypnotizes me with the sound.

Thanks for the other suggestions but I see the BD73 also has low ft and I keep reading this is bad for audio, can someone explain?
Attached Images
File Type: jpg DSC00702ar.jpg (797.8 KB, 738 views)
File Type: jpg DSC00692.jpg (989.4 KB, 712 views)

Last edited by mart.s; 14th April 2013 at 07:47 PM. Reason: Pics added.
  Reply With Quote
Old 14th April 2013, 07:43 PM   #6
jaycee is offline jaycee  United Kingdom
diyAudio Member
Join Date: Apr 2004
Location: Norwich, UK
You might find that MJ15003 work better. Go with OnSemi, as they are what used to be Motorola's semiconductor division so they will be high quality parts
  Reply With Quote
Old 14th April 2013, 09:36 PM   #7
MikeVou is offline MikeVou  United Kingdom
diyAudio Member
Join Date: Oct 2012
Location: United Kingdom
You will find some useful discussions on substituting 2N3055 in the Quad forums. I believe the Quad 303 used what were essentially 2N3055 equivalents, but individually selected for a wider SOA. The contributors to those forums have done a lot of thinking about and testing of substitutes.
They do give a caution though - watch out for stability issues. The original 2N3055s had a pretty limited frequency response (as you mention), which contributed to the 303's "bombproof" reputation. There is a risk that substituting higher fT types will turn a stable amplifier into an unstable one - either ruining sound quality or even causing OP stage to self-destruct. Those Quad forums are well worth looking at.
  Reply With Quote
Old 14th April 2013, 10:16 PM   #8
Telstar is offline Telstar  Italy
diyAudio Member
Join Date: Dec 2007
Location: Italy
Two things:
First, you changed also many caps and not just the blown output transistors, so you cannot be sure that it's them making the sound worse.
Second, careful in replacing old trannies with much faster ones, you can get into oscillo-land.
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 14th April 2013, 10:48 PM   #9
indianajo is offline indianajo  United States
diyAudio Member
indianajo's Avatar
Join Date: Jan 2010
Location: Jeffersonville, Indiana USA
Yeah, you may be hearing oscillations. You can't buy real 2n3055, everything is faster. On dynaco ST120 amps, we put ~22 pf between base and emitter of the driver transistors ahead of the output transistors. Faster output transistors should give better sound according to the simulations done by someone on the Leak Delta 70, but oscillations sound bad and consume the transistor doing the wrong thing. I've never heard my ST120 with the original 2n3772 or RCA 5 digit (high Vceo 2n3055), those were burnt up when I bought it, but with NTE60 (probably MJ15003 equivalents) it always sounded okay at decent volume. Not nearly as vile as the reviews in 1966 said it was. It did have a low volume distortion, that is another issue.
To detect oscillation without a scope, if you have an old fashioned VOM with a 2VAC and 20 VAC scales, put a .47 uf (microfarad in newspeak) capacitor in series with the input on VAC and measure the output with the input shorted. Any significant voltage you can't hear, could be RF oscillation. Then change the cap to 470 pf or something. Still have significant AC voltage on the output, for sure it is RF. This test won't work with DVM's, they just produce random numbers when subjected to RF oscillations.
Personally I like the MJ15015G as a sub for the 2n3055, they are about $3 cheaper than MJ15003 and about $2.50 cheaper than MJ21194G. They also have a higher Vceo which is important in my ST120, and they have a specified safe operating area, which hadn't been defined in 1966 IMHO. They are faster than 2n3055, however. Put the little caps in on the drivers, and if you don't have a zobel network on the output (12 turn inductor in series transistor collector junction to speaker hot, 1 k resistor and a cap in series between speaker hot and speaker ground) add one. See the "TIP mod" for the dynaco ST120 on greg dunn's website. This mod is probably a good idea for any original old PWB designed to drive 2n3055 or earlier that wasn't tested for parts faster than that. You can make the inductor by winding any old thin wire around a china marker or fat grade school pencil. Dynaco had you wind them around the output caps, rather quaint.
Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,1.3K, SP2-XT's, T-300 HF Proj's, Steinway console, Herald RA88a mixer, Wurlitzer 4500, 4300

Last edited by indianajo; 14th April 2013 at 11:05 PM.
  Reply With Quote
Old 14th April 2013, 11:57 PM   #10
mart.s is offline mart.s  United Kingdom
diyAudio Member
Join Date: Dec 2008
I Replaced the 3 main caps which were identical in spec and brand to the originals so I dont think that is the problem Telstar. I hear what everyone is saying about using faster transistors and that's what I'm worried about. How will I know if it's oscillating? will I hear something? or will the output pair just get very hot quickly. If I do try the MJ15003 from On Semi do I need to set bias very low at first just in case. The last thing I want to do is fry the amp. And from what other are saying here I may need to put a small value cap across the base and emitter of the driver if I do get problems. Is there anything else I need to consider when changing them?
  Reply With Quote


Best 2N3055 alternativesHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
2n3055 nbcd Solid State 10 26th August 2004 09:14 AM

New To Site? Need Help?

All times are GMT. The time now is 12:59 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio