let's contemplate how , for instance , XA25 is overpriced ......
Yes it is overpriced, I see here two pucks for 3 $......
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Yeah muses looks great, I was just curious about lower CMRR (60) values comparing to opa627au.
Actually ordered opas already and wanted to check the muses as well. I will give it a try.
TI SoundPlus Op Amps
I recently compared all five TI SoundPlus Op Amps that are available in a SOIC-8 package using DIP to SMD adapters for the Whammy. I found that their top end chip, the OPA1612AID easily outperformed the others in providing a smooth, detailed, tonally balanced sound that complements each of my diverse types of headphones, both open and closed back dynamics and planar magnetics. It was a bit surprising to me that the OPA1612AID has a bipolar front end, yet outperformed the FET and JFET front end chips. Here is a summary of their specs:
TI SoundPlus Op Amps:
Essential Series:
OPA1652AID FET input
Pkg: SOIC-8
Approx. Cost: $2.00
Noise: 4.5 nV/√Hz at 1 kHz
Slew Rate: 10 V/μs
Distortion: 0.00005% at 1 kHz
OPA1662AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $2.00
Noise: 3.3 nV/√Hz at 1 kHz
Slew Rate: 17 V/μs
Distortion: 0.00006% at 1 kHz
Premier Series:
OPA1602AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $3.00
Noise: 2.5 nV/√Hz at 1 kHz
Slew Rate: 20 V/μs
Distortion: 0.00003% at 1 kHz
OPA1642AID JFET input
Pkg: SOIC-8
Approx. Cost: $2.50
Noise: 5.1 nV/√Hz at 1 kHz
Slew Rate: 20 V/μs
Distortion: 0.00005% at 1 kHz
Ultimate Series:
OPA1612AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $7.00
Noise: 1.1 nV/√Hz at 1 kHz
Slew Rate: 27 V/μs
Distortion: 0.000015% at 1 kHz
I recently compared all five TI SoundPlus Op Amps that are available in a SOIC-8 package using DIP to SMD adapters for the Whammy. I found that their top end chip, the OPA1612AID easily outperformed the others in providing a smooth, detailed, tonally balanced sound that complements each of my diverse types of headphones, both open and closed back dynamics and planar magnetics. It was a bit surprising to me that the OPA1612AID has a bipolar front end, yet outperformed the FET and JFET front end chips. Here is a summary of their specs:
TI SoundPlus Op Amps:
Essential Series:
OPA1652AID FET input
Pkg: SOIC-8
Approx. Cost: $2.00
Noise: 4.5 nV/√Hz at 1 kHz
Slew Rate: 10 V/μs
Distortion: 0.00005% at 1 kHz
OPA1662AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $2.00
Noise: 3.3 nV/√Hz at 1 kHz
Slew Rate: 17 V/μs
Distortion: 0.00006% at 1 kHz
Premier Series:
OPA1602AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $3.00
Noise: 2.5 nV/√Hz at 1 kHz
Slew Rate: 20 V/μs
Distortion: 0.00003% at 1 kHz
OPA1642AID JFET input
Pkg: SOIC-8
Approx. Cost: $2.50
Noise: 5.1 nV/√Hz at 1 kHz
Slew Rate: 20 V/μs
Distortion: 0.00005% at 1 kHz
Ultimate Series:
OPA1612AID Bipolar input
Pkg: SOIC-8
Approx. Cost: $7.00
Noise: 1.1 nV/√Hz at 1 kHz
Slew Rate: 27 V/μs
Distortion: 0.000015% at 1 kHz
I've been auditioning a few different op amps in my Whammy so I thought to share.
I started with the OPA2134 which I enjoyed. My whole system of new 'phones and new Whammy needed a break in period to truly sound good. The OPA2134 did fine. Next up I tried the ebay offering of the "Full discrete dual op amp based on Marantz HDAM". There are lots of different sellers offering this device on ebay at around $17.00 and it is worth every penny of that. It has a JFET input and has a very relaxed and smooth presentation. A euphonic midrange to upper midrange is what I hear but it lacks in detail and bass texture but it is very pleasant to listen to overall and it really amuses me. Next up is the AD825 single op amps mounted on the Brown Dog adaptors. These ones need a long break in period. Longer than any device I've ever tried. These op amps really sound great though. They have a grip on the bass that is unmatched among amps that I have tried. The other amazing thing I love is the detail in the instruments as placed in the stereo spread. I just keep coming back to these as my favorites.
I started with the OPA2134 which I enjoyed. My whole system of new 'phones and new Whammy needed a break in period to truly sound good. The OPA2134 did fine. Next up I tried the ebay offering of the "Full discrete dual op amp based on Marantz HDAM". There are lots of different sellers offering this device on ebay at around $17.00 and it is worth every penny of that. It has a JFET input and has a very relaxed and smooth presentation. A euphonic midrange to upper midrange is what I hear but it lacks in detail and bass texture but it is very pleasant to listen to overall and it really amuses me. Next up is the AD825 single op amps mounted on the Brown Dog adaptors. These ones need a long break in period. Longer than any device I've ever tried. These op amps really sound great though. They have a grip on the bass that is unmatched among amps that I have tried. The other amazing thing I love is the detail in the instruments as placed in the stereo spread. I just keep coming back to these as my favorites.
I just picked up a "Brown Dog" to try the OPA1612A and there's definitely a subtle improvement for my setup. It seems to liven the amp up a bit more and provide a bit more impact and detail.
Quick question, I followed the recommended build from the guide on the 1st page, and measured Vcc (Pin1 <-> Pin8 on the DIP-8 adapter) to be at 15.99VDC. I know 6L6 mentioned there should be 17V across the rails in the standard configuration. The OPA1612 datasheet states "Wide Supply Range: ±2.25 V to ±18 V" so I'm sure it's fine (and sounds great).
I just wanted to check in to ensure there wasn't something else (resistor or cap) that I needed to worry about with this particular opamp. And I'm also curious now why I'm seeing 15.99VDC instead of 17VDC.
Ahhh, yes. That would make sense. Thanks for the clarification!
Now, I just need to figure out what I'm going to do for a chassis. Really wish we had an update on an ETA for the official version.
@avdesignguru, have you noticed any additional noise when using the OPA1612?
I'm noticing some interesting behavior where it's picking up a lot of noise, particularly noticeable when I move my hand around the amp, and touch the volume knob (like a grounding issue almost). But, what's interesting is that this is not detected when I use the OPA2134..?
I'm wondering if the circuit just isn't super friendly with the 1612? It also seemed like it wasn't play quite as nice with my 300 Ohm 650's. I'd be interested to hear a circuit designer's opinion on that. I may try the OPA1642 and see how that compares.
I'm noticing some interesting behavior where it's picking up a lot of noise, particularly noticeable when I move my hand around the amp, and touch the volume knob (like a grounding issue almost). But, what's interesting is that this is not detected when I use the OPA2134..?
I'm wondering if the circuit just isn't super friendly with the 1612? It also seemed like it wasn't play quite as nice with my 300 Ohm 650's. I'd be interested to hear a circuit designer's opinion on that. I may try the OPA1642 and see how that compares.
Interesting. It could very well be that it's not yet enclosed in a chassis, and while I do have a capacitor placed between the IEC ground and the input ground, it's a temporary solution and the quality of the soldering could be better.
Maybe it's due to the higher slew rate that just exacerbates the noise?
Aradan, which AD op-amp out of curiosity? I'm going to try the AD825 (dual BrownDog) once I receive it.
Maybe it's due to the higher slew rate that just exacerbates the noise?
Aradan, which AD op-amp out of curiosity? I'm going to try the AD825 (dual BrownDog) once I receive it.
My build is dead quiet with either the OPA2134 or the OPA1612. I'm using the Hammond chassis.
I'm not familiar with the Brown Dog adapter. I used a cheap one from amazon:
https://amazon.com/gp/product/B07R5QR9P3/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I used the big square pins that came with the adapter and soldered them to a socket. That assembly then plugs in snug down to the top of the electrolytic caps with the top edge of the plastic capacitor sleeves providing some insulation from the tiny PCB edges.
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OPA1612 is my current favorite—sparkfun board and added some pins (Also love OPA627—2 singles on browndog adapter, and OPA2107). It's probably some combo of phones and music styles who knows.
Both of my builds are dead quiet. The current one with the pot soldered to the PCB in a 1U has less noise I can hear when messing around inside the the case—signal wires to pot vs none—both are quiet when sealed up. I make sure to rough up the anodizing (Modushop/DIY store aluminum chassis) between all connecting parts, evaluate noise with lid on. I built as speced with cap on inputs. Both builds have wood fronts and both of them I ran a ground wire from the pot to the star ground point (big ring connector that I sandwich with the washer for a tight connection)—If I didn't I'd get some buzz when touching the vol knob. Had the same issue with BA18 Pre.
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