Since building my Whammy, I have bought a bunch of standard IC OP Amps to test to see how it affects the overall sound quality of the amp.
I tested these OP Amps using HiFiMan HE400i headphones and a Topping D50 DAC. For the audio source I used Evanescence Synthesis album in FLAC 96Khz 24 bit format.
Below is a list of all the 8P-DIP Dual OP Amps I have tested in the Whammy along with a brief description of how they sound:
AD823ANZ:
Operating Voltage: 36v MAX
Slew Rate: 22v/µs
DC Offset: L 0.5mV / R -0.2mV
FET: Yes
Notes: Vocals very good but some mids and treble sounds a little raspy.
LM833-N:
Operating Voltage: 36v MAX
Slew Rate: 7v/µs
DC Offset: L -0.1mV / R 3.4mV
FET: No
Notes: Very good all round OP Amp with clear vocals, good soundstage and natural bass.
LM833P:
Operating Voltage: 36v MAX
Slew Rate: 7v/µs
DC Offset: L 22.9mV / R 26.2mV
FET: No
Notes: Very good OP Amp with clear vocals and good soundstage. Improved version of the LM833-N although DC offset is considerably higher.
RC4580 (Texas Instruments):
Operating Voltage: 18v MAX
Slew Rate: 5v/µs
DC Offset: L 14.2mV / R 14.1mV
FET: No
Notes: Good general OP Amp with tiny noticable distortion amounts with certain types of music, sounds best with dance music.
OPA2134PA SoundPlus:
Operating Voltage: 18v MAX
Slew Rate: 20v/µs
DC Offset: L 0.6mV / R 0.4mV
FET: Yes
Notes: Very clear with good soundstage and vocals very pronounced. Very nice OP Amp.
OPA2228PA
Operating Voltage: 18v MAX
Slew Rate: 2.3v/µs
DC Offset: L -0.2mV / R -0.1mV
FET: No
Notes: Very good, clear up front vocals, very good mids and treble, wide soundstage, overall I like this OP Amp.
OPA2107AP
Operating Voltage: 18v MAX
Slew Rate: 18v/µs
DC Offset: L -0.2mV / R -0.3mV
FET: Yes
Notes: Very clear and concise right through all the ranges. Vocals very prominent and wide soundstage. I really like this one.
LME49720NA
Operating Voltage: 17v MAX
Slew Rate: 20v/µs
DC Offset: L 0.8mV R 1.6mV
FET: No
Notes: Nice all round OP Amp with good soundstage. Very clear but mellow sounding.
AD746JNZ
Operating Voltage: 18v MAX
Slew Rate: 75v/µs
DC Offset: L -0.3mV / R -0.2mV
FET: Yes
Notes: Very nice sounding with wide soundstage, clear mids and treble with punchy bass. I really like this one.
LM4562NA:
Operating Voltage: 17v MAX
Slew Rate: 20mv/µs
DC Offset: L -0.4mV / R -1.1mV
FET: No
Notes: Very good all round OP Amp with clear vocals and good soundstage.
NJM4556AD:
Operating Voltage: 18v MAX
Slew Rate: 3v/µs
DC Offset: L 5.8mV / R 5.4mV
FET: No
Notes: Nice OP Amp with clear vocals, wide soundstage and balanced bass. Mids and trebles seem a little softer compared with other OP Amps.
OPA1622, OPA1662, OPA2210, OPA2189 and OPA1692 OP Amp testing:
OPA1622 SoundPlus:
Operating Voltage: 18v MAX
Slew Rate: 10v/µs
DC Offset: L -152.6mV / R -154.2mV
FET: No
Package: VSON-8
Notes: This is an excellent OP Amp, High clarity, wide sound stage, no noticable distortion, this one is truly stunning from the mids and trebles right through to the vocals. DC offset is extremely high in this one. Maybe due to the extra onboard components of the DIP adapter. There are some resistors and capacitors.
OPA1662 SoundPlus:
Operating Voltage: 36v MAX
Slew Rate: 17v/µs
DC Offset: L 76.2mV / R 74.8mV
FET: No
Package: SOIC-8
Notes: Very wide sound stage, clear with good mids and trebles, vocals prominent and up front. Overall nice sounding OP Amp. DC offset is also quite high.
OPA2189:
Operating Voltage: 36v MAX
Slew Rate: 20v/µs
DC Offset: L -0.1mV / R -0.2mV
FET: No
Package: VSSOP-8
Notes: This is quite a nice OP Amp with clear vocals, wide soundstage and balanced mids and trebles. Very low DC offset.
OPA1692 SoundPlus:
Operating Voltage: 36v MAX
Slew Rate: 23v/µs
DC Offset: L -34.8mV / R -34.9mV
FET: No
Package: SOIC-8
Notes: Crystal clear, good sound stage and up front vocals. Sounds really nice this one.
OPA2210:
Operating Voltage: 18v MAX
Slew Rate: 6.4v/µs
DC Offset: L -0.1mV / R -0.2mV
FET: No
Package: SOIC-8
Notes: This OP Amp sounds incredible. Very wide soundstage, clear mids and treble with vocals just at the right distance. This one really brings out the finer details. Very low DC offset. Really like this one.
After having a good listen to the Whammy with each of these OP Amps there are a few that stick out that I would certainly call my favourites or top picks. They are the AD746JNZ, OPA2134PA, OPA2228PA, OPA2107AP. These ones sound excellent and I highly reccommend them to anyone looking to experiment with the sound signature. For the ones on 8P-DIP adapters the OPA2189 and the OPA2210 are also very good in the Whammy.
So there you have it! Hope this helps some people to make up their minds over choosing or swapping OP Amps in the Whammy. Just remember that this article reflects my opinion only as sound is subjective. So have a listen for yourself.
Many thanks for this overview!
Could you please compare sound/performance of Whammy with other commercial or Diy headphone amps you have had.
Hi I have already done this if you take a look through my reviews.
I have read through all reviews in this site. Would give me a hint where to look?
Sorry I may have misunderstood. I compared the Burson and SparkoS OP Amps with my 2 custom headphone amps in their respective reviews but the OP Amps in this article were about how they sound in the Whammy specifically. I did not do any comparison with these particular OP Amps in any other devices because firstly they are all dual OP Amps and the NuHybrid only takes singles and I only have one of each of the OP Amps listed so can’t compare in the Burson DAC as they require 2 singles and 2 duals. Hope this helps.
Thanks! I am contemplating about building Whammy and just wanted to ask how does it (with your favorite opamp) compares in general with other headphone amps (pamps based, class A, tubes, oetc) you have had chance to listen? Another canditate is new Nelson Pass’s new ACP+.
I would go for it! For me, with it’s simple yet dead silent onboard PSU and it’s clarity and wide sound stage, I would consider this my reference amp when making comparisons. I highly recommend building the Whammy. It’s a fun project and very rewarding. I would love to build the ACP+ but can’t get the boards anywhere at the moment.
Thanks for thumbs up!