What’s on *YOUR* workbench?

tube socket cleaning on a blackheart little giant head ... getting ready to downsize it on out of here after many years as my test bench amp
 
2025-07-0412.18.061570622996476658849.jpg
Rat opamp shootout
Findings playing a loop through an EL ACHE build max gain, filter wide open
1)Harris HA2-5130-2 best note articulation, good low end, nearing unobtanium, not a CA5130 varriant
2)Linear LT1008 close second, a little less saturated but full tight low end
3)LM308 yep
4)Raytheon RV4077FDE a little less saturation, less fizz/sizzle than a 308 but bottom extension is lacking but what is there is tight
5)OP07 ... There's a weird ice pick 1khz harmonic, boxy low end, less harmonics but more crossover distortion?
6)OP02 meh fizzy, less balls, flubby bottom

1 2 and 4 are all improved OP07 types, per the datasheets
 
nothing beats the chicken dragon

R39LRJY.jpg


rKbgbLN.jpg
 
Found them. Yeah. Definitely a difference in the lows and overtones
Though I'm just noticing the Cyrillic D in these other ones. LOL
And the OP07DP stamped underneath
1000007175.jpg
 
jwin615 said:
View attachment 98334
Rat opamp shootout
Findings playing a loop through an EL ACHE build max gain, filter wide open
1)Harris HA2-5130-2 best note articulation, good low end, nearing unobtanium, not a CA5130 varriant
2)Linear LT1008 close second, a little less saturated but full tight low end
3)LM308 yep
4)Raytheon RV4077FDE a little less saturation, less fizz/sizzle than a 308 but bottom extension is lacking but what is there is tight
5)OP07 ... There's a weird ice pick 1khz harmonic, boxy low end, less harmonics but more crossover distortion?
6)OP02 meh fizzy, less balls, flubby bottom

1 2 and 4 are all improved OP07 types, per the datasheets
Click to expand...
While I've never before heard of the LT1008, HA5130, RV4077 or OP02; I always thought the Rat's unique sound was due to the low slew-rate and what it does to an audio signal with regard to the human ear. With a slew-rate at around 0.4V/µs and lower, the upper-end clarity of an audio signal tends to "sound" broken up because the slew-rate is unable to to keep up with signal zero-crossings & peaks of the signal.

The LM308/µA308 and OP07 has a slew-rate of 0.3V/µs - just below the threshold of detection by the human ear. (Of course, people's ears are different and some can hear an electron groan as it passes thru a PN/NP junction. But most cannot.)

The LT1008 has a slew-rate of 0.2V/µs - even lower than the 308 and should exhibit that distinct Rat distortion.

The HA5130 has a slew-rate of 0.8V/µs - higher than the 308, OP07, LM741 or LM748. (Have you tried an LM741 or LM748? Personally, I think they just sound nasty - and not in a good way.) So it should ring clearer as you indicated in your post.

And the OP02 has a slew-rate of 0.5V/µs (some samples seem exhibit a slew-rate of 0.25V/µs).

Curiously, the LM358 (dual opamp) also has a low slew-rate of 0.3V/µs and to my ears does a fair job of mimicking the 308. In working with a Kokko Distortion circuit trace I've been working on, I found the LM358 to be an excellent replacement for the Kokko Distortion's original use of a TL072. Going a step further, I found the LT1490 (also a dual opamp) to possess a slew-rate of only 0.03V/µs. I fell in love with the LT1490 when I heard it place of either the TL072 or LM358 in that circuit. Lots of upper end break up. (Build report on the modified Kokko Distortion clone (RatStortion) coming soon after the finished enclosures arrive.)

Anyway, just wanted to toss in my 2¢ and say thanks for the informative post. 🙏 (y)
 
This got dang sumbitch I've built 3 times now. It didn't work right so I took it apart to troubleshoot, which was pointless bc the problem was one of the lfo chips. I did some research and found one of them was most likely counterfeit, but I don't have another set to try out. You can see in the pic both are the MN type but have different print. I put it back together trying a different method to keep it more organized, but it didn't fit. So now it's the third time. I took a break for now. Just the power and audio to go.

dIBqfo8.jpeg
 
Cybercow said:
Anyway, just wanted to toss in my 2¢ and say thanks for the informative post. 🙏 (y)
Click to expand...
I have been curious to try the 1008 as it bills itself as an improved 07, is current production and has better noise specs, fwiw in this circuit. The datasheets for the LT1008, the Raytheon and Harris and are all super-beta opamps iirc and all mention being upgrades and/or drop in replacements for either 108/308s or OP07s.
I think all 3 nail the sound pretty well.
The OP02 was just laying around so I figured why not.

I'm not sure if I have any 1490s but I'll be on the lookout.

Once I figure out the Analog Discovery 2 I recently acquired, I look forward to doing some frequency sweeps and noise measurements for stuff like this.

I will note that the build I was using these in isn't a stock rodent. Bigger decoupling caps, no electros in the signal path and slightly modified filters to let more low end through and defeat the nasal quality of the original circuit that I don't care for. But those tweaks probably make the differences more apparent.
 
You must log in or register to reply here.
Back
Top