Neve BA10640 substitute transistors

[andia]

Hi all,

I am trying to substitute transistors for some BA10640 amp I made for use in a 33609 clone. unfortunately it was impossible to find the BC441 and BC461 transistors for good prices and I searched for similar transistors.
right now I have built one with BC141 and BC161 transistors and it works for itself. what do I have to look for to know if it is a working substitute?
right now this is what I have tested: I have connected it to 24V powersupply, currentdraw is 16mA with a 1kHz sinewave @0dBu running from input to output. distortion is 0.0012% with this signal. I put a 300ohm resistor between output and ground. transistors have heatsinks, nothing gets hot.

thank you for your input.

 

[JohnRoberts]

Did it measure that distortion with the 300 ohm load? If yes probably OK.

JR

 

[abbey road d enfer]

Hi all,

I am trying to substitute transistors for some BA10640 amp I made for use in a 33609 clone. unfortunately it was impossible to find the BC441 and BC461 transistors for good prices and I searched for similar transistors.
right now I have built one with BC141 and BC161 transistors and it works for itself. what do I have to look for to know if it is a working substitute?
right now this is what I have tested: I have connected it to 24V powersupply, currentdraw is 16mA with a 1kHz sinewave @0dBu running from input to output. distortion is 0.0012% with this signal. I put a 300ohm resistor between output and ground. transistors have heatsinks, nothing gets hot.

thank you for your input.

In a well-designed audio product, swappping transistors should not result in significant performance difference, as long as the max voltage and current are equal or superior to the type they replace, and as long as Hfe and Ft are not too wildly different.
Input transistors add a noise constraint.

 

[andia]

thank you for your answers! I have found some more specifications for the 10640 amp in the manual of a 33609 and tested it against my amp with the new transistors:

- Quiescent Conditions: with a gain boost resistor of 1k6ohm (equivalent to +20dB gain) and the output terminated in 620 ohm, the static current should be between 20mA and 30MA; the standing output voltage (pin 6) should be +12V +/-1V

the result with my amp is 15mA static current,standing output voltage is +12V

- Gain: with 1kHz sine wave input at -10dBu, the output level should be +10dBu +/-0.5dB.

result with my amp +10,3dBu

- Maximum Output: with an output load of 50 ohm and the 1kHz input level increased until the output signal is just clipping, the output level should be greater than +18dBu.

result with my amp +19dBu before clipping. here the output transistors get warm, not hot but warm

- Distortion: At 1kHz input adjusted to give 17dB output into 50ohm, the distortion should be as follows:
100Hz...less than 0.008%
1kHz...less than 0.004
10kHz...less than 0.026

result with my amp @100Hz...0.0019%; @1000Hz...0.008%; @10kHz...0.03%

- Noise: with the input short-circuited, the output noise level must be less than -96dBu over the bandwidth 20Hz to 20kHz.

result with my amp about -82dBu

the results are close except for the noise measurement, where I am not sure if I am conducting it right, what does short-circuited mean here ( to ground? to non inverted input?)
do I have to adjust bias of the amp for better noise and distortion figures with the substitute transistors? are R5 and R6 the bias resistors?


thanks again!

 

[JohnRoberts]

result with my amp @100Hz...0.0019%; @1000Hz...0.008%; @10kHz...0.03%

0.03% THD at 10kHz is not bad... Most THD measurements are THD+N so a little extra noise could explain the difference

- Noise: with the input short-circuited, the output noise level must be less than -96dBu over the bandwidth 20Hz to 20kHz.

result with my amp about -82dBu

Is your noise measurement limited to 20kHz bandwidth? Wideband measurements including above 20kHz content will easily measure higher but not sound noisier.

the results are close except for the noise measurement, where I am not sure if I am conducting it right, what does short-circuited mean here ( to ground? to non inverted input?)
do I have to adjust bias of the amp for better noise and distortion figures with the substitute transistors? are R5 and R6 the bias resistors?

I would speculate (guess) that + input is shorted to ground and - input is open circuit. Shorting the + input will shunt Johnson (thermal) noise of R2 and input noise current times R2.

thanks again!

I repeat, probably OK, how does it sound?

JR

 

[reinw33]

I bought the MPSA18, for the BC109 and BC184 IIRC. Gain ranges between 480-530. Was very cheap. I don't know substitutes for the BC461/441 yet.
Perhaps there is a substitute from MPSA too? for those.

 

[abbey road d enfer]

I don't know substitutes for the BC461/441 yet.

May I suggest ZTX851/951?

 

[moamps]

.. substitutes for the BC461/441 ...

I would suggest a pair 2N3019/2n4033 which can be bought from tme.eu

 

[andia]

I bought the MPSA18, for the BC109 and BC184 IIRC. Gain ranges between 480-530. Was very cheap. I don't know substitutes for the BC461/441 yet.
Perhaps there is a substitute from MPSA too? for those.

of the BC184, BC214 i have a lot. it is only the BC441/461 that I can not really find.

 

[andia]

I have done one amp now with my last pair of BC441/BC461 that I have found in my drawers and measured it as per the neve specs. It measured very, very closely the same as the BC141/161 version in level, thd and so on. I have also done a noise plot of both, also the same. Blue is BC441/461, red is BC141/161.
I have not had the chance to listen to them, as I have to do the motherboard and switch assembly first, but I suppose there wont be a lot of difference in sound.

noiseplot:

 

[andia]

I would suggest a pair 2N3019/2n4033 which can be bought from tme.eu

thanks, this seems to be nice alternative!

 

[andia]

May I suggest ZTX851/951?

thank you, I will also look into this!

 

[ruffrecords]

BC461 are available from Silicon Ark. £1 each

Cheers

Ian

 

[MidnightArrakis]

Hi all,

I am trying to substitute transistors for some BA10640 amp I made for use in a 33609 clone. unfortunately it was impossible to find the BC441 and BC461 transistors for good prices and I searched for similar transistors.
right now I have built one with BC141 and BC161 transistors and it works for itself. what do I have to look for to know if it is a working substitute?
right now this is what I have tested: I have connected it to 24V powersupply, currentdraw is 16mA with a 1kHz sinewave @0dBu running from input to output. distortion is 0.0012% with this signal. I put a 300ohm resistor between output and ground. transistors have heatsinks, nothing gets hot.

thank you for your input.

>>> See if these "Equivalent Replacement" transistors will work for you. PDF datasheets are attached:

BC141 = NTE2347

BC141 is in-stock at MOUSER:

https://www.mouser.com/ProductDetail/Central-Semiconductor/BC141-16-PBFREE?qs=OlC7AqGiEDm5A9%2BUHL3Xmw==

BC161 = NTE189

BC161 is in-stock at TME:

https://www.tme.com/us/en-us/detail...MIrvThm83jhQMVnF1HAR3kLA0ZEAAYAiAAEgKSCPD_BwE

/

 

[reinw33]

I would suggest a pair 2N3019/2n4033 which can be bought from tme.eu

The 2N4403 are already on one my lists of carts of replacement parts on the website reichelt, it costs 0,04€ each!