TL072 or 4558 in a Blues Jr Reverb

[PRNDL]

I'm fixing a Blues Junior amp with a non-working reverb unit.

My initial guess is a bad IC chip, although I haven't opened it up yet.

I'm wondering if it's worthwhile to substitute a 4558 for the TL072.

I believe the TL072 is a dual 741 opamp, which has better specs than the 4558, which many say sound better with music.

Is this a good idea, or just plain silly?

Thanks!

[tubeswell]

I dunno, for some reason I found the TL072 better to my ear in my PV Classic 30 than the 4558. Seemed to give it slightly more 'verb. Maybe if you're looking for a bunch of TL072s I could fish you out some in return for some 500pF mica caps.

[Enzo]

I wouldn't think it would make much difference. But if you really want to know if it matters or not, mount an 8 pin DIP socket to the board, then you an plug in any dual op amp you care to in the name of science.

[corworld]

I worked on a Blues Jr. with a non-functioning reverb this week. I would suspect the reverb pan before an IC. check resistance at both the input and output.

Similar thread:

http://music-electronics-forum.com/s...ead.php?t=2769

[Enzo]

Hi Cor, welcome to the forum.

[corworld]

Thanks, I appreciate all the sage advice you give out.

[chipaudette]

PRNDL wrote: "I believe the TL072 is a dual 741 opamp, which has better specs than the 4558, which many say sound better with music."

>>>>

To my knowledge, the TL072 is NOT a dual 741. It is a dual 071, with the 071 being superior to the 741.

I believe that the 071 does have an identical pin-out to the 741, but so do most every other basic op-amp built since the 741.

Chip

[Dave Curtis, dB AudioTech]

I worked on a Blues Jr. with a non-functioning reverb this week. I would suspect the reverb pan before an IC. check resistance at both the input and output.

Similar thread:

http://music-electronics-forum.com/s...ead.php?t=2769

Yes, rule out the tank/cabling first, then dive in. occasionally, it's only a broken wire on one of the Molex connectors in the tank.

-DC

[Rick Erickson]

It is a dual 071, with the 071 being superior to the 741.

The TL0xx series has JFET inputs and bi-polar outputs for higher input impedance, lower noise, higher slew rate, lower output impedance and more current drive capability than the run of the mill standard 741. The only way to know if it is "better" in your application though, is to try both of them, as Enzo pointed out. A tech friend in California called me up the other day laughing, and told me he had just read an article about the "tube-like" qualities of the 741. It seems that everything old is just naturally better. (the exception being me) I was around when Analog Delay units first hit the market and heard old-timers complain that they didn't have the same feel as an Echoplex. And when the Gibson Humbucking pickup first hit the market they were considered inferrior to the old Soap Bar single coils...

RE

[PRNDL]

I worked on a Blues Jr. with a non-functioning reverb this week. I would suspect the reverb pan before an IC. check resistance at both the input and output.

You were correct ... the reverb input was open circuit.

Of course, I had already put in an IC socket and a TL082 (the only one that the local RS had), which isn't amplifying (pins 123 have DC instead of AC), but that might be due to the reverb tank.

Is the correct replacement an Accutronics 8EB2D1B?

Is there any benefit to the Torres reverb pan upgrade and bag?

[Enzo]

What upgrade? If you are talking about the three spring instaed of two spring "upgrade" that some people sell, that is a full size pan, and that won't fit in a blues junior. Some of these "upgraders" want like $50 for a reverb pan you can buy elsewhere for half that.

[tubeswell]

Well all I know is I like the little TL072 - it did seem slightly better to my ear than the 4558 in the reverb in my PV. I don't care if other people don't believe me . And it was a straight substitute - no modding needed.

[Robert M. Martinelli]

"best sounding" opamp?

Well all I know is I like the little TL072 - it did seem slightly better to my ear than the 4558 in the reverb in my PV. I don't care if other people don't believe me . And it was a straight substitute - no modding needed.

I do believe you....
The reason for that could be the JFET architecture of the 072s, that could put some emphasis on even harmonics rendering the reverb' s tone less "metallic" and more pleasant to the ear.....

4558s are only updated versions of the old LM358, and they both have BJT inputs....

talking 'bout 4558s, I prefer to substitute them with NE5532s, which are pin to pin compatible and have a much better noise figure, ( the same reason why I usually replace 741s with NE5534s or OP27/37 ); as Enzo wisely said, the best way to find the best sounding opamp for your purpose is to fit a DIP socket in and experiment....

Best regards

Bob