TO-3P-3 replacements for 2n3055

[Potato Cakes]

Hello, everyone,

I am looking to use a TO-3P-3 NPN BJT to replace the infamous 2N3055 in a circuit design. The power specs seem very comparable, but the one thing I wasn't sure about is the bandwidth. The 2n3055 is rated at 200kHz and the lowest for the TO-3P-3 is 3MHz with most of them rated for 30MHz. My concern is that using this higher bandwidth for the output transistor will cause instability. Being that this is in the output section of a preamp stage with a transformer that follows it, how concerned should I be about instability in this application?

Thanks!

Paul

 

[JohnRoberts]

The 2n3055 was a generic popular "go to" npn power device. Modern device processes are much better and new ones will as you have observed have improved gain bandwidth metrics compared to original old soldiers (original 3055 was slow as molasses and hard to kill).

Wider gain bandwidth is not automatically a risk for instability, might behave better with less lag, or not.

If possible try one and see how it behaves. You should be able to increase stability compensation  if needed.

JR

 

[Potato Cakes]

Thanks, JR.

I am aware that the 2N3055 is old and slow, but also aware that swapping parts out for higher slew rates/bandwidth might also be an issue, and even more aware that my electronics knowledge is novice at best so I feel the need to double check every "creative" thought I have when changing out parts to suit my desires. Would a zobel network on the output transform suffice as compensation or will that have to be done somewhere else?

Thanks!

Paul

 

[JohnRoberts]

Thanks, JR.

I am aware that the 2N3055 is old and slow, but also aware that swapping parts out for higher slew rates/bandwidth might also be an issue, and even more aware that my electronics knowledge is novice at best so I feel the need to double check every "creative" thought I have when changing out parts to suit my desires. Would a zobel network on the output transform suffice as compensation or will that have to be done somewhere else?

Thanks!

Paul

I can't guess what you will experience.

Note: some aficionados of "old stuff" believe there is something magical about old slow parts. I do not argue with people on the WWW about what they say they hear. 

Instability in a NF circuit can be caused by the combination of more than unity loop gain with more than 180' of phase shift/delay lag in a NF path. When the phase shift/delay causes the negative feedback to appear positive "and" gain is higher than unity, oscillation can happen.

Most active circuits already contain some stability compensation so A) your circuit may not even oscillate, or B) the fix may be as simple as adjusting the value of an existing compensation cap.

BTW authentic old/slow 3055 have not been manufactured for some time now, so I suspect these circuits may already be working out in the wild using modern parts.

JR 

 

[Potato Cakes]

I can't guess what you will experience.

Note: some aficionados of "old stuff" believe there is something magical about old slow parts. I do not argue with people on the WWW about what they say they hear. 

Instability in a NF circuit can be caused by the combination of more than unity loop gain with more than 180' of phase shift/delay lag in a NF path. When the phase shift/delay causes the negative feedback to appear positive "and" gain is higher than unity, oscillation can happen.

Most active circuits already contain some stability compensation so A) your circuit may not even oscillate, or B) the fix may be as simple as adjusting the value of an existing compensation cap.

BTW authentic old/slow 3055 have not been manufactured for some time now, so I suspect these circuits may already be working out in the wild using modern parts.

JR

Ah, yes,  the NOS transistor argument. I did that one time when I was building an ez760 (ADR Compex type compressor/gate) and most of the NOS transistor parts I ordered were either fake or just didn't work, creating a troubleshooting nightmare as the circuit has more than a handful of transistors in a variety of models. After that my eyes were really opened to the silliness of those types of arguments and I started finding modern replacements for those parts. I still have several newer 2n3055's that I bought a couple of years ago, but I know if I am to look at making a board for continued use it's probably not smart to rely on a finite supply of a discontinued part (or soon to be). I've also been using newer parts for the older, coveted circuits I've built and they all sound fantastic. I don't know how they compare to the "real" thing (serial number dependent) but it does cause clients to be severely impressed.

I'll get couple of types and try doing a direct replacement and report back. It will probably be a couple of weeks before I do.

Thanks!

Paul

 

[Whoops]

but I know if I am to look at making a board for continued use it's probably not smart to rely on a finite supply of a discontinued part (or soon to be).

I understand what you say about NOS and not wanting to do develop a project with hard to find parts,
I just don't understand why do want to replace the 2N3055.
Why do you say that the 2N3055 is a soon to be discontinued part?

This transistor is used in so many different devices, it proved to be useful and sturdy  in different applications (ex PSU and Power amplifiers).
I've just checked and farnell alone has 24 thousand units in stock, other suppliers also have high quantities, so I really don't see this transistor being discontinued anytime soon

Farnell aprox 24000 units
Mouser aprox 1700 units
Digikey 4500 units

 

[Potato Cakes]

I understand what you say about NOS and not wanting to do develop a project with hard to find parts,
I just don't understand why do want to replace the 2N3055.
Why do you say that the 2N3055 is a soon to be discontinued part?

This transistor is used in so many different devices, it proved to be useful and sturdy  in different applications (ex PSU and Power amplifiers).
I've just checked and farnell alone has 24 thousand units in stock, other suppliers also have high quantities, so I really don't see this transistor being discontinued anytime soon

Farnell aprox 24000 units
Mouser aprox 1700 units
Digikey 4500 units

Interesting. I was sure not to long ago they were a little harder to find and quite a bit expensive, though if memory serves me correctly they were all TO-3 and the newer ones are TO-204-3, which I don't see a difference unless there is a slight change to the case dimensions.

The other thing to consider is the footprint. The 2n3055 takes up quiet a bit of space and I don't know how crowded the real estate on the PCB I'm working to design will be, but I think anything thing I can do to cut down on the board dimensions will be a bonus.

Since I am not building a PSU nor an amplifier, I think I will still explore swapping out with a newer TO-3P-3 part as it has it does have higher bandwidth. And hopefully I'll learn something in the process. Which is always the goal.

Thanks!

Paul

 

[Whoops]

Interesting. I was sure not to long ago they were a little harder to find and quite a bit expensive, though if memory serves me correctly they were all TO-3 and the newer ones are TO-204-3, which I don't see a difference unless there is a slight change to the case dimensions.

They were always easy to find, the transistor is used in Neve BA283 amplifiers, so a lot of people use them around here when building Neve type circuits and there was never a shortage as far as I can remember

The other thing to consider is the footprint. The 2n3055 takes up quiet a bit of space and I don't know how crowded the real estate on the PCB I'm working to design will be, but I think anything thing I can do to cut down on the board dimensions will be a bonus.

Definitely they take quite a bit of space.
TO-3P take much less.

wish you all good to your project

 

[Potato Cakes]

Thanks! I'll be a while before I get to test this out, but I will report back when I do.

Thanks!

Paul

 

[CJ]

leakage current, that's where the tone lives. 

we swap out old school 3055 stuff for MJ21194  all day long in Marantz receivers and i tell you what, the new transistors sound a bit harsh.

not to say that after a little break in period they might mellow out but that is another different can of worms right there.  i don't have time to wait around a year and make a conclusion.

but how long will those low voltage NOS 3055's last? there is a dependibillty (sp) tradeoff there.

 

[synthiaks]

This is interesting as I'm having a suspicion that a 3055 from Tesla is failing in an Old GDR active speaker that I have.

So the facts are:

3055 is still manufactured to better specs but the online argument is that the older "slower" ones sound better?

Or is it more to it than that?

Just to kind of fine tune my snake oil Radar on this discussion. Before I spend nights and days to find 3055s from the 70s

S

 

[CJ]

the 3055 topic is by no means new around here, you might find some interesting reading from days gone by,

https://groupdiy.com/index.php?action=search2



hmm, weird, can not seem to link to a page full of 3055 threads, anywho, if you type 2N3055 in the search box at the star above, you will be greeted by a virtual smorgasboard of info.

 

[synthiaks]

the 3055 topic is by no means new around here, you might find some interesting reading from days gone by,

https://groupdiy.com/index.php?action=search2



hmm, weird, can not seem to link to a page full of 3055 threads, anywho, if you type 2N3055 in the search box at the star above, you will be greeted by a virtual smorgasboard of info.

Sorry...

I got to lazy there

As a Swede I'm always looking for a good Smörgåsbord.

S

 

[JohnRoberts]

leakage current, that's where the tone lives. 

we swap out old school 3055 stuff for MJ21194  all day long in Marantz receivers and i tell you what, the new transistors sound a bit harsh.

not to say that after a little break in period they might mellow out but that is another different can of worms right there.  i don't have time to wait around a year and make a conclusion.

but how long will those low voltage NOS 3055's last? there is a dependibillty (sp) tradeoff there.

I remain suspicious of unqualified anecdotal sound quality claims like "sounds harsh".  Further I do not expect them to "break in" with time. 

If only you had a test bench so you could back up your observations with numbers.  In my experience I could pretty much measure anything that I could reliably hear, while I could measure things that I could not hear.  :-[

JR

 

[CJ]

well, i'm from Mississippi, the "show" me state. 

is there a piece of test equipment that will  measure the beauty of tropical fish in Hawaii?



i like the sound of these silver 4558's, don't know why, 

 

[JohnRoberts]

well, i'm from Mississippi, the "show" me state. 

is there a piece of test equipment that will  measure the beauty of tropical fish in Hawaii?



i like the sound of these silver 4558's, don't know why, 

You are thinking of Missouri....

You can make good soup with ugly bones...

JR

 

[shabtek]

Is this gonna veer into a recipe/cooking discussion?
Loves me some real soup stock, tis hard to find ugly bones at the local grocers: only boneless skinless and “stock” comes in a paper carton.
I do have some old hens roosting so good soup will be on the menu soon.

 

[JohnRoberts]

Is this gonna veer into a recipe/cooking discussion?
Loves me some real soup stock, tis hard to find ugly bones at the local grocers: only boneless skinless and “stock” comes in a paper carton.
I do have some old hens roosting so good soup will be on the menu soon.

Have you ever used bay leaves in soup? (but I was making a metaphor)

JR

 

[Whoops]

3055 is still manufactured to better specs but the online argument is that the older "slower" ones sound better?

Or is it more to it than that?

Just to kind of fine tune my snake oil Radar on this discussion. Before I spend nights and days to find 3055s from the 70s

Don't think so, never heard anything about older 3055 sounding better than new ones, never heard anything about a new 3055 not working when replacing and older unit.
I replaced quite a few in the past and always used off the shelf modern replacements, On Semi, Toshiba, ST , all of them work very well.

There might be some discussion on vintage ones because at some point Neve used Motorola branded 2N3055, but thats really just because people see photos of Motorola transistors in Neve BA283 boards, not that they sound any better than others.
Neve actually originally used NewMarket 2N3055, but there's less people looking for those because they appear in less internet pictures.
If someone influential says somewhere online that Newmarket transistors sound better than Motorola's and are crucial to the Neve sound, then some people will trash their Motorola's stock NOS.
Any 2N3055 works well in a Neve type circuit, and also never had any problems in replacing them in power amps.
Never had to replace them in PSUs

This is my experience with 2N3055 from different brands and time periods, if anyone has a different experience please share

 

[CJ]

some people have different hearing than others.