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New Reigning Champ in Speed - The THS4631 opamp!

post #1 of 48
4/12/05 at 5:38am
Thread Starter 
New Reigning Champ in Speed - The THS4631 opamp! and by speed, i mean fastest opamp ive gotten to run perfectly - 325mhz - 1000V/uSec transimpedence opamp running completely stable in my amp, soic, mounted on the usual browndog like the ad8065s, ive recommended these to sovkiller a couple days ago, and they seem to be running perfectly in his ppa as well.

As for the sound, smooth, best treble ive heard in an opamp, largest soundstage, amazing vocals, crystal clear, seems to get it all right, for you classical music lovers, this is your opamp, initially they sounded bright, as do most things new, but after leaving the ppa on for a couple days, its all toned down, and wow, is all i can say.

Now ipsilonsound started a thread way back on the ths4061/81, ppl and i, played with those recently and couldnt get them to work too much fuss,their bipolar, so we found a jfet input ths, the ths4631, with better specs even, and wow, so far so good in the amp, ideal for those building ppav2, maybe m3, and these might work for you RS HR-2 people too, and other chip based amps.

Now to get these onto a single to dual browndog adapter and slap them onto my emu1212m.

www.ti.com - ths4631D

datasheet - http://focus.ti.com/lit/ds/symlink/ths4631.pdf




and one more thing, this thread is:
40% evil, 60% good according to http://homokaasu.org/gematriculator/

hooray!
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post #2 of 48
4/12/05 at 8:53am
With such specs, they mostly seem to me the perfect opamps for I/V conversion at the output of a DAC.
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post #3 of 48
4/12/05 at 10:28am
Indeed they do, in the typical applications section they even state Current-DAC buffer.

Dammit xtreme4099 you coudln't have found this 2 days ago? I just ordered the OPA627s for my dac :cry:
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post #4 of 48
4/12/05 at 4:28pm
That thing sounds pretty intense! Has it been tried in any other topologies than the PPA?

Very cool, it isn't too often that another chip gets added to the arsenol of the hard-core chip-roller.
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post #5 of 48
4/12/05 at 5:09pm
I might have to give it a shot in my DAC. I am currently using OPA627s. They are a bit too dark there, but they are still my favorite.
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post #6 of 48
4/12/05 at 5:34pm
There are three versions listed at Digikey, which one were you using in your amp? At $8.33 each these represent a significant savings over the 627/637's so I'm intrigued to say the least.

Nate
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post #7 of 48
4/12/05 at 5:37pm
Thread Starter 
THS4631D - SOIC
you'll need a single to dip browndog adapter from www.brndog.com
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post #8 of 48
4/12/05 at 6:08pm
I will have a few of these to test with the M³ amp in a couple of days. Meanwhile, I suggest the would-be opamp rollers to wait a bit, because this is a very fast, wideband opamp and has the potential of being cranky and unstable. Those without proper test equipment cannot truly determine whether the opamp is behaving well.
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post #9 of 48
4/12/05 at 6:40pm
We evaluated this op-amp for our upcoming amplifier designs. Sonically, it wasn't as synergistic as we had hoped. It also didn't measure as well as a 627 or a 134. Overall amplifier (measured in a test Max) THD+N vs. frequency was averaging .025% whereas the 627 was at about .018% (300 ohm load). The noise floor was a bit higher between DC and 200Hz as well. However, that's in a HeadRoom amp circuit topology.

I can tell you that this op-amp oscillated like crazy upon initial power-up. I had to increase the resistance between the output of the 4631 and the input of the next amplification/buffer stage to get it to calm down. It was stable in a normal non-inverting configuration and in a multiple feedback loop configuration. The lowest gain I ran it at was 3.5.

What intrigued me (apart from the crazy slew rate numbers) about this op-amp was that it also comes in a SOIC-8 PowerPad package, like the 6120 headphone amp chip. The die is actually exposed on the bottom of the IC package and can be soldered (during reflow) directly to a pad on the board. A pretty cost efficient heatsinking method, especially if you're running the op-amp with class-A biasing.

In any accord, it has some awesome numbers and is significantly cheaper than a 627 which should definitely make it a candidate on the op-amp evaluation short-list.

Joe
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post #10 of 48
4/12/05 at 9:37pm
I'm still burning mine, but so far so good, it is a crystal clear Opamp, fast as hell, and the bass is as good as in the AD843 with the clear top of the 8065, but even better, on the PPA topology. Honestly price/performnace ratio it is a winner, and I don't worry too much on how it measures, but how it sounds, at the end is what we use to judge the performance, I'm not sure if at the end I keep those or the 8065, as I like them both, but definitelly the battle in the PPA topology is between those two....more to come...
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post #11 of 48
4/12/05 at 10:12pm
Groovy Sovkiller.
Please post your final impressions about this part in the PPA. I'm still really interested in using it in some manner. I still have some stock floating around so if you're really diggin' on its performance, I'd probably have to break down and kluge them into our PPA.

Thanks!
Joe
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post #12 of 48
4/12/05 at 10:29pm
Quote:
Originally Posted by Joe Woj
Groovy Sovkiller.
Please post your final impressions about this part in the PPA. I'm still really interested in using it in some manner. I still have some stock floating around so if you're really diggin' on its performance, I'd probably have to break down and kluge them into our PPA.

Thanks!
Joe
If you have a PPA around Joe, I definitelly encourage you to burn in a set on it, and give them a try, seriously, they sound very, very good (in this topology of course, maybe in other amps it is piece of crap, as usual, for example I know that the AD744 shine in other amps, and in the PPA is nothing spectacular)

I have tried and still have here a bunch of OPams: among them: 637APs, 637BPs, 627BPs, AD744, AD843, AD8065, AD8610, and tried also some LT and honestly those are the best along with the AD8065, really good...

I was evne thinking in putting to gether an OP rolling kit for the PPA users, just that as you may know they are static sensitive and they will get busted at some point for improper use, and I do not want to loose them...
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post #13 of 48
4/12/05 at 11:01pm


How would the THS4631 compare to the THS4130?

-Ed
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post #14 of 48
4/12/05 at 11:04pm
they are not compatible Ed... The design is different.
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post #15 of 48
4/12/05 at 11:54pm
Thread Starter 
ths4601d .. is a lower bandwith version ... bit smoother, almost as detailed, in case you find these a bit too much.
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