onboard preamp opamp replacement

[sonicnuance]

I recently replaced the LF444 opamp in my bass' preamp with a TL074.

It made a huge difference in tone to my ears especially in the high frequencies. The noise dropped too.

My question: is there a better drop in replacement (14 pin DIP) that is appropriate for a single 9V battery (headroom and battery life). (I don't mind changing the battery every other month or so playing 1 hour a day)


Thanks,
mozart

 

[vin*tone]

I'm not sure which is best.... but... You might like to solder an IC socket in there so you can swap the chips out easier and compare.. These have the same pinouts as the LF444:

LT1058, LF147, LF247, LF347, NTE859, OP482, TL074

FYi The LF444 is a quad JFET input opamp so it's like 2 LF442's stuck together. TL074 = 2 x TL072 etc...

Funny you should post this. People often give the Jag pre a bad rap. I'm thinking of busting it open to find out exactly why.

 

[vin*tone]

...The LF444 is a quad JFET input opamp so it's like 2 LF442's stuck together. TL074 = 2 x TL072 etc....

I say this bc there's more data and opinion out there on dual opamps...

[Invalid or Expired Link Removed]

In the electro geek world its kinda the equivalent of asking "Whots the best bass for doom-metal-grind-core-punk". There are a lot of views and a lot of people telling the OP to do a search.

 

[sonicnuance]

I'm not sure which is best.... but... You might like to solder an IC socket in there so you can swap the chips out easier and compare.. These have the same pinouts as the LF444:

LT1058, LF147, LF247, LF347, NTE859, OP482, TL074

FYi The LF444 is a quad JFET input opamp so it's like 2 LF442's stuck together. TL074 = 2 x TL072 etc...

Funny you should post this. People often give the Jag pre a bad rap. I'm thinking of busting it open to find out exactly why.

Thanks vin... its actually a Stingray preamp

 

[Angus]

You replaced an LF444 with a TL074?!

TL074's are awful for audio applications. They are really, really old and outdated. I'd throw those things out and fast. High noise and noise floor and slow rate.

There are a lot better options high quality options out there. A great option for a quad for an audio application that isn't too expensive is a Burr-Brown OPA2134.

Really though, you should that TL074 out of there and fast.

 

[vin*tone]

Yes good choice. They're actually owned by TI now.

http://focus.ti.com/docs/prod/folders/print/opa2134.html

 

[sonicnuance]

You replaced an LF444 with a TL074?!

TL074's are awful for audio applications. They are really, really old and outdated. I'd throw those things out and fast. High noise and noise floor and slow rate.

There are a lot better options high quality options out there. A great option for a quad for an audio application that isn't too expensive is a Burr-Brown OPA2134.

Really though, you should that TL074 out of there and fast.

Hmmm... have you actually read the datasheets on the LF444 and TL074? The TL074 has both a higher slew rate and a lower noise floor than the LF444.

Also, I've seen TL071/2/4's used in many audio applications (pre Fender SWR for one) While I'm sure there are better out there, I certainly wouldn't call them "awful". As I said, to my ears the TL074 sounds better than the LF444.

Thanks for the recommendation on the OPA2134 though. Its specs look nice, except the current draw is 2x the TL074. I'll see if I can find one.

 

[Angus]

My comment wasn't based on the LF444 vs. the TL074- it was that a TL074 is not a great step up. Ask anyone who works in the audio engineering field- they're very strongly frowned upon for proper applications. They get used because they're cheap, plentiful, reliable, and low draw.

I wouldn't worry about the draw on it, though. I've been using them in a piezo preamp (two quads; 6 piezo inputs) with a single 9V supply and I haven't had to change the battery in well over a year of sustained use. They're better than the specs suggest, and for the money I think it's the best easily-purchasable op amp on the market.

For what it's worth, btw, I'm good friends with a former SWR engineer, and he said that one of the best things to do was to immediately replace the op amps with higher quality ones. He said most of the in house guys did it on their own gear.

All of this said, it's so far unlikely that you are going to really hear much of the difference between good vs great op amp that it will end up getting filed into the "audiophile" category, where the changes are so pointlessly small that people tell themselves it's different to justify the work involved.

But a TL074 is definitely not a great modern choice for audio gear anymore, IME.

 

[sonicnuance]

My comment wasn't based on the LF444 vs. the TL074- it was that a TL074 is not a great step up. Ask anyone who works in the audio engineering field- they're very strongly frowned upon for proper applications. They get used because they're cheap, plentiful, reliable, and low draw.

I wouldn't worry about the draw on it, though. I've been using them in a piezo preamp (two quads; 6 piezo inputs) with a single 9V supply and I haven't had to change the battery in well over a year of sustained use. They're better than the specs suggest, and for the money I think it's the best easily-purchasable op amp on the market.

For what it's worth, btw, I'm good friends with a former SWR engineer, and he said that one of the best things to do was to immediately replace the op amps with higher quality ones. He said most of the in house guys did it on their own gear.

All of this said, it's so far unlikely that you are going to really hear much of the difference between good vs great op amp that it will end up getting filed into the "audiophile" category, where the changes are so pointlessly small that people tell themselves it's different to justify the work involved.

But a TL074 is definitely not a great modern choice for audio gear anymore, IME.

Angus - thanks for the reply and your perspective.
Which opamp are you referring to on the current draw? Hopefully it is the OPA2134 which I've ordered based on your recommendation.

That is interesting about the SWR story. Do you know what they replaced the TL072/4's with?


Thanks again

 

[Angus]

No problem! I was talking about the current draw on the OPA, yes. Where did you order it from?

I don't remember which amps they replaced the TL's with, but I think I have it written down somewhere. I'm sure they were really high quality TI's or Nationals or something. That said, he's also a fan of the Burr-Brown. I'll see if I can find those notes.

 

[sonicnuance]

No problem! I was talking about the current draw on the OPA, yes. Where did you order it from?

I don't remember which amps they replaced the TL's with, but I think I have it written down somewhere. I'm sure they were really high quality TI's or Nationals or something. That said, he's also a fan of the Burr-Brown. I'll see if I can find those notes.

That's great news about he current draw on the OPA... although I do need the four amp version which will draw more. I assume you were referring to that one, which makes me excited about swapping it.

Burr-Brown is owned by TI so going to the TI site gives a LOT of info and choices.

The TL's are still available via TI.

I ordered some stuff through Digikey as well as samples through my work. I'll keep you posted.

I need to put the SOIC into a 14pin DIP. Never done it before - should be fun
Thank you again for your help!

 

[sonicnuance]

You replaced an LF444 with a TL074?!

TL074's are awful for audio applications. They are really, really old and outdated. I'd throw those things out and fast. High noise and noise floor and slow rate.

There are a lot better options high quality options out there. A great option for a quad for an audio application that isn't too expensive is a Burr-Brown OPA2134.

Really though, you should that TL074 out of there and fast.

I got the OPA2132 (higher end than opa2134 - I think it is trimmed thus the higher price). Noise is slightly less but barely noticeable. Don't notice much else of a difference yet to be honest. I may go back to the TL074 after some A/B'ing

 

[Angus]

A 2132 isn't a higher end 2134- 2132's are the duals, 2134s are the quads. Same circuitry.

If you don't notice a difference between the TL074 and the BB, then you probably won't notice the difference between that and almost any other decent op amp. Nothing wrong with that- it just means there are too many other factors in the signal chain that have a much more substantial than the op amp. This is not surprising.

 

[sonicnuance]

A 2132 isn't a higher end 2134- 2132's are the duals, 2134s are the quads. Same circuitry.

If you don't notice a difference between the TL074 and the BB, then you probably won't notice the difference between that and almost any other decent op amp. Nothing wrong with that- it just means there are too many other factors in the signal chain that have a much more substantial than the op amp. This is not surprising.

Sorry, I meant to say I replaced it with an OPA4132 which is a quad. Everything else I said still stands.

You are right though... the other factors are dominating. The good news is by going back to the TL074 (or TLE2074) I'll save some battery life.

I appreciate all your help so far

 

[Angus]

Ah. Actually, I would've tried the straight 2134 rather than the 4134- we did studies on op amps not too long ago, and people much preferred the 2134 to the 4. I did, too, but this was on a headphone amplifier. The 2134 won the comparison out of 10 op amps, and it won nearly 100% of the subjects.

Either way, doesn't make much difference in this application, probably!

 

[sonicnuance]

Ah. Actually, I would've tried the straight 2134 rather than the 4134- we did studies on op amps not too long ago, and people much preferred the 2134 to the 4. I did, too, but this was on a headphone amplifier. The 2134 won the comparison out of 10 op amps, and it won nearly 100% of the subjects.

Either way, doesn't make much difference in this application, probably!

I appreciate that input as I want to use this opamp for a non portable audio application (ie an amp head) and it is much less expensive than the opa***2 series.

 

[Passinwind]

Ah. Actually, I would've tried the straight 2134 rather than the 4134- we did studies on op amps not too long ago, and people much preferred the 2134 to the 4. I did, too, but this was on a headphone amplifier. The 2134 won the comparison out of 10 op amps, and it won nearly 100% of the subjects.

OPA2134 is a dual op amp, not a quad one.

 

[Eight_Stringer]

Perhaps it is just me ( missed a past thread ) or is this thread about unplugging various op amps ( bipolar, bicmos and fet bundled together, pin out commonality being the only common requirement? ) and then doing a range of tests? Or am i missing that each application circuit is configured to reflect optimal performance for each very different op amp in question. Regards John.

 

[sonicnuance]

Perhaps it is just me ( missed a past thread ) or is this thread about unplugging various op amps ( bipolar, bicmos and fet bundled together, pin out commonality being the only common requirement? ) and then doing a range of tests? Or am i missing that each application circuit is configured to reflect optimal performance for each very different op amp in question. Regards John.

To me, the thread is about trying different *appropriate* opamps to find the one that gives the best sound and lowest noise yet still is reasonable for battery applications. By appropriate (without reverse engineering the schematic) I mean using an amp that can be biased properly without tweaking the rest of the circuit... ie a drop in replacement. I didn't bother trying a BJT opamp due to the chances of the input stage not being properly biased. Since the original opamp was a JFET, I stuck with FET input-stage opamps.

Much of this is thread is subjective but I find many knowledgeable folks here have good recommendations which I take seriously. Specs don't tell the whole story when it comes to an amplifier's "sound", but they do help narrow the range of possibilities.

Thanks