LM301 substitution

[Moby]

Hi all

I have consoles that use the 301 which is now obsolete in dip8 package (soic seem to stay alive?)
The LM301 is used in a specific way I don't remember to see elsewhere, where the input stage is bypassed and a discrete differential pair is used in place and sent to the output stage via comp/bal pin.

I'm not expert at all in opamp topology/design and like to know what other of opamp is able to be used like that.

Here the idea of discussion is not to replace for "better" opamp, I have no complain about the sound of my 169 and 289, but anticipate a possible substitution when my spare spent out or when NOS stock get completely overpriced...

Best
Zam

LM301 DIP8, how many pieces you need? I think I still can buy it locally.

 

[robovox]

BGMicro shows stock on these at a reasonable price.

https://www.bgmicro.com/ICSLM301.aspx

 

[zamproject]

Hello

LM301 DIP8, how many pieces you need? I think I still can buy it locally.

BGMicro shows stock on these at a reasonable price.

https://www.bgmicro.com/ICSLM301.aspx

Thanks to both of you for the help.
I should have enough spare for the moment.

Best
Zam

 

[diggy fresh]

I'm not good enough to contribute too much but i think the Ward beck m460 and m470 preamps uses the lm301 in a similar way, bypassing some of the limitations of the internal stuff with discrete parts around it. I have dug a little bit around to find a way to upgrade the lm301 because of the bad reputation but haven't come to any conclusive info yet.  I'm very interested to know if anybody has an idea or tried something.

 

[chrisenglish]

BGMicro shows stock on these at a reasonable price.

https://www.bgmicro.com/ICSLM301.aspx

Has anyone tried these in a Studer 169 - 269 ?

 

[gridcurrent]

Has anyone tried these in a Studer 169 - 269 ?

yes.
circuit critique welcome.

thanks !
drawing revised.

 

[JohnRoberts]

yes.
circuit critique welcome.

well that schematic looks wrong... The input LTP (long tail pair) needs to use PNP devices for that PS orientation.

JR
[edit- well now that schematic input pair looks like it was fixed (changed to pnp)... /edit]

 

[jokeramik]

The NE5534 is not the right substitute. Input offset current and Input bias current are higher (around factor of ten) then the LM 301. The best way ist to use an SOIC to DIP-Adapter.
Alternatively you check the use of the LT1122 with higher slew-rate or the OP42 with higher slew-rate and symmetrical slew-rate.
Best regards!
jokeramik

 

[jacomart]

yes.
circuit critique welcome.

thanks !
drawing revised.

Honestly the class AB output buffer for me isn't very appealing.
Cheers
J.

 

[JohnRoberts]

Honestly the class AB output buffer for me isn't very appealing.
Cheers
J.

Class AB output stages are extremely common especially inside ICs to reduce power dissipation.

JR

 

[jacomart]

Class AB output stages are extremely common especially inside ICs to reduce power dissipation.

JR

I agree, but for a discrete-elements realization I would prefer to use class A, but that's just my opinion.
Cheers
J.

 

[abbey road d enfer]

The NE5534 is not the right substitute. Input offset current and Input bias current are higher (around factor of ten) then the LM 301.

I don't get it. In this application, the input devices are bypassed and replaced with discrete transistors, so input offset and bias currents are not anymore chip-dependant.
I'm too lazy to ascertain it would work, though.
For most of the circuits in these Studer mixers, the LM301 could be subsituted with 5534 without problems. Even with an order of magnitude higher, input offset and bias currents are not a concern, except in the limiter side-chain, where a FET opamp would be better..

 

[Matt Syson]

I 'fettled' a Studer mini mixer (169?) a few year back and tangled with the issue of 'booster' input transistors although I forget what I did now. I had seen the 'embelishment' of essentially substandard chips many years ago with a former employer. I even saw the SSM2015 preamp chip with 'extra'op amp to improve that chip's performance (before the SSM2016 was released).
Crown used a unusual chip in their DC300 power amps and has a single ended (class A but without pull up/down output) so you can't sensibly stick any other normal op amp in.
There are other slightly 'oddball' units around such as using TL062 (?) principally for their low supply current needs so having extra output transistors to boost current capability for output driving stages.
Matt S

 

[JohnRoberts]

I 'fettled' a Studer mini mixer (169?) a few year back and tangled with the issue of 'booster' input transistors although I forget what I did now.

Adding discrete input devices was generally done not for boost, but lower noise. National Semi published a classic app note doing this with the LM394 as an improved LTP input stage.

I had seen the 'embelishment' of essentially substandard chips many years ago with a former employer. I even saw the SSM2015 preamp chip with 'extra'op amp to improve that chip's performance (before the SSM2016 was released).

Those substandard chips (like LM301) were standard back in the day. I used 301s back in the 70s. One nice trick with the LM301 was bypassing the input pair with a capacitor at high frequency. This only worked for inverting topology but delivered superior slew rate for back then. This was before cheap bifets gave is fast slew rates without other compromises.

Crown used a unusual chip in their DC300 power amps and has a single ended (class A but without pull up/down output) so you can't sensibly stick any other normal op amp in.

I don't remember that, but can't imagine hot rodding the DC300 (DC coupled speaker killer). It used a slow quasi-complementary output stage that was hard to kill, but not very high fidelity. Crown later repackaged the DC300 design into a SMD version (CE1000), I'd avoid that one too.

There are other slightly 'oddball' units around such as using TL062 (?) principally for their low supply current needs so having extra output transistors to boost current capability for output driving stages.
Matt S

I used the lower current TL064 bifet in my first generation drum tuner to be less of a drain on the battery. I tried to use a newer generation low current op amp but they were not very well behaved on my test bench at low voltage. I used a discrete output stage buffer with the 064 but I was driving speakers inside my tuner. The low quiescent current in the TL 64 compromised input noise, but not a problem for my design.

JR

 

[Matt Syson]

Sorry, my use of the word 'booster' was used a bit carelessly like so many who claim something is 'better', the real question being 'better at what'.
I meant boosting is a boost in the noise performance (suggesting lower noise) better figures.