Your opinion about BC560B, LM301, BC140 - 160

Hi guys!

currently restoring a studer 89 console,

I swapped some dual line outputs amp cards I have on the master bus of the console to check the good working condition of them and all cards was sounding differently.

The circuit is around BC560B (which are BC179B on some cards), LM301, BC140, BC160, tantal caps

Nearly all of them got different brands-series components depending the cards and to my ears there's quite a difference in the quality of the audio depending the components used on the cards.

I started swapping LM301 and noticed some changes for the better, BC560B seemed clearer-more defined sounding than the BC179B ones so I'm wondering if you have any preferences or if there's some known things about one LM301 sounding better than a other?
A BC560 better than a other?
I have the same question for the BC 140 and 160, and tantal caps, if there's such a thing!

About the correct Hfe of the transistors which should be used as as a replacement of the BC179B:
BC179B is 180 to 460
BC560B is 200 to 450  so I guess it should be the one?

I attach you the schematic of the line amp

Many thanks for your advise!

So you´re swapping opamps obviously without understanding the circuit. This desk is built around 301 opamps and the circuits around these chips are designed to improve the weaknesses of the 301. Many parts are totally unnecessary if you install other ICs, they even lower the performance of the newly installed chip.
Did you actually measure the performance improvement which you did hear? What parameters did you improve with chipswapping?

jensenmann said:

So you´re swapping opamps obviously without understanding the circuit. This desk is built around 301 opamps and the circuits around these chips are designed to improve the weaknesses of the 301. Many parts are totally unnecessary if you install other ICs, they even lower the performance of the newly installed chip.
Did you actually measure the performance improvement which you did hear? What parameters did you improve with chipswapping?

Click to expand...

Hi Jensenmann,
I think you didn't understand what I tried to explain before!

I'm not swapping LM301 for another kind of chip, I swapped it for another LM301 from a different brand/maker and heard sound differences. Same thing about BC560 and BC179B, some cards got the 560 some cards got the BC179 and again noticed sounds differences, so my question was if there's any manufacturer better than others for these parts from actual experience.
Any recommendations? Thanks

The weak link in the chain of this design is the LM301 and the fact that it is being asked to drive a pure class B output stage. As a result it is forced to  slew 2 x Vbe every cycle as fast as it possibly can. The loop gain will help mitigate this a little but the bottom line is the performance is limited by the slew rate of the LM301. No wonder you can hear difference between cards.

Cheers

Ian

ruffrecords said:

The weak link in the chain of this design is the LM301 and the fact that it is being asked to drive a pure class B output stage. As a result it is forced to  slew 2 x Vbe every cycle as fast as it possibly can. The loop gain will help mitigate this a little but the bottom line is the performance is limited by the slew rate of the LM301. No wonder you can hear difference between cards.

Cheers

Ian

Click to expand...

Thanks Ian, would you know about any LM301 which would perform better than others in this regard?
It seems there was a lot of different LM301 made since 40 years.
I bought some new ones at Farnell but was wondering if for example old signetics might be better?
Even LM301 is often described as a weak link, I find the sound very good!

thekid777 said:

Thanks Ian, would you know about any LM301 which would perform better than others in this regard?
It seems there was a lot of different LM301 made since 40 years.
I bought some new ones at Farnell but was wondering if for example old signetics might be better?
Even LM301 is often described as a weak link, I find the sound very good!

Click to expand...

It is surprising how different the same device made by different manufacturers can be. I remember back in the early 80's using some CMOS switches in the Dragon 32 home computer to switch the joystick inputs to the AtoD. We  had lots of semiconductor manufacturers chasing us with offers to supply chips and the prices just got better and better. We were persuaded to buy a certain brand of CMOS switch only to find they oscillated at about 10MHz!!  All I can suggest is you try different brands until you find one you like best.

Cheers

Ian

Ahhh! quite a quest!

That's very interesting circuit (input signal is connected to pins 1 and 5!!) . The output transistors are slightly biased IIRC (Studer says the overall quiescent current for two channels is 24mA). Anyway, from my experience the most critical parts in old Studer consoles are electrolytic  capacitors, so the first step should be recapping. If you like to change output transistors, try to find matched transistors with high hfe  (more than 100). For small transistors you can use BC550/560C (matched) with high hfe also. I will prefer LM 301 in metal  package, military version of course  .

moamps said:

That's very interesting circuit (input signal is connected to pins 1 and 5!!) . The output transistors are slightly biased IIRC (Studer says the overall quiescent current for two channels is 24mA). Anyway, from my experience the most critical parts in old Studer consoles are electrolytic  capacitors, so the first step should be recapping. If you like to change output transistors, try to find matched transistors with high hfe  (more than 100). For small transistors you can use BC550/560C (matched) with high hfe also. I will prefer LM 301 in metal  package, military version of course  .

Click to expand...

Thanks Mo!
I thought only a pair of 560 should be matched looking at the schematic? (Q103 and Q104)
I could go with 560C instead of B ? which indeed have way more Hfe than the original BC179B found on the schematic
I never saw a LM301 in metal package before! isn't it complicated to fit them on the "normal" socket of a regular lm301?
This one: http://fr.farnell.com/texas-instruments/lm301ah-nopb/ampli-op-general-purpose-to58/dp/1216151
His specs would match correctly with the circuit?

Best!

thekid777 said:

I thought only a pair of 560 should be matched looking at the schematic? (Q103 and Q104)

Click to expand...

Yes.

This one: http://fr.farnell.com/texas-instruments/lm301ah-nopb/ampli-op-general-purpose-to58/dp/1216151

Click to expand...

That one looks expensive.
This one is cheaper
http://www.ebay.de/itm/LM301AH-TO-99-METAL-CAN-IC-X-1PC-/261567407745?epid=1030289361&hash=item3ce6a1e681:g:X4YAAOSwv0tVJo73

You can easily bend TO99 pins to fit into DIL8 socket.

moamps said:

Yes.That one looks expensive.
This one is cheaper
http://www.ebay.de/itm/LM301AH-TO-99-METAL-CAN-IC-X-1PC-/261567407745?epid=1030289361&hash=item3ce6a1e681:g:X4YAAOSwv0tVJo73

You can easily bend TO99 pins to fit into DIL8 socket.

Click to expand...

Will try a pair of these to compare with the normal ones
thanks!