Help me choose a 2n3055 for my 1073 clone

[Jrockpsycho]

I have a bunch of vintage 2n3055 and would like to use one in my two 1073 clones. This is my first post so forgive me if this is the wrong place. Any help is much appreciated. Thank you!

Transistor 1 (in mega ohms)
Positive base/ Negative collector: 0.8
Positive base/ Negative emitter: 1.25
Diode check (Positive base/ Negative emitter): 0.533
hFE: 73
Vf: 543mV

Transistor 2 (in mega ohms)
Positive base/ Negative collector: 2.06
Positive base/ Negative emitter: 3.18
Diode check (Positive base/ Negative emitter): 0.558
hFE: 57
Vf: 568mV

Transistor 3 (in mega ohms)
Positive base/ Negative collector: 2.17
Positive base/ Negative emitter: 3.03
Diode check (Positive base/ Negative emitter): 0.533
hFE: 98
Vf: 549mV

Transistor 4 (in mega ohms)
Positive base/ Negative collector: 1.76
Positive base/ Negative emitter: 2.76
Diode check (Positive base/ Negative emitter): 0.532
hFE: 126
Vf: 551mV

Transistor 5 (in mega ohms)
Positive base/ Negative collector: 2.40
Positive base/ Negative emitter: 2.89
Diode check (Positive base/ Negative emitter): 0.530
hFE: 98
Vf: 538mV

Transistor 6 (in mega ohms)
Positive base/ Negative collector: 2.10
Positive base/ Negative emitter: 3.05
Diode check (Positive base/ Negative emitter): 0.526
hFE: 78
Vf: 552mV

Transistor 7 (in mega ohms)
Positive base/ Negative collector: 1.60
Positive base/ Negative emitter: 0.74
Diode check (Positive base/ Negative emitter): 0.524
hFE: 19
Vf: 554mV

 

[ruffrecords]

Almost all of them should be fine except perhaps the one with an hFE of 19. It is important to rememeber that unless you make measurements under the same conditions as the device is used in the 1073, the results are not terribly useful. The 1073 class A output stage uses a lot of NFB so the characteristics of the 2N3055 have no measureable effect on the sound.

Cheers

Ian

 

[Tubetec]

I posted a link to an IEEE article about the 2n3055 and its various versions , its definatly around here somewhere , worth a look ,
The way the device was made was changed sometime in the early to mid seventies . Some amp guys will insist the old style 2n3055 sounds nicer . The last mixed batch of old stock 2N3055 I got I think I paid around 50 pence each , a mix of Motorola and RCA mainly , dont get fooled into paying over the odds for new old stock ,
If you want the old style production method the 'lightening strike' RCA era ones can often be found for the same price as any surplus 2N3055 .

Ian ,
back in the day at Neve would they have selected the output transistors within a certain range ?

 

[ruffrecords]

Ian ,
back in the day at Neve would they have selected the output transistors within a certain range ?

As far as I know we did not.

Cheers

Ian

 

[Tubetec]

I was sure I had posted this before here somewhere ,
https://groupdiy.com/threads/real-motorola-2n3055-or-fake.69345/

 

[Jrockpsycho]

Thank you

 

[JohnRoberts]

The 2n3055 was extremely popular (many sold), so the device makers kept putting the old part number on newer versions.

If the circuit is using significant NF parameter differences will be even less audible.

JR