### New Discrete Op Amps From Sparkos Labs

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#### I.Greyhound Fan

##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #20 on: 9 May 2014, 10:52 pm »
Well I may have wasted \$68.  We will see what happens when I bring the unit over to Frank.

#### sparko311

• Jr. Member
• Posts: 12
##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #21 on: 10 May 2014, 09:19 pm »
Be a bit cautious trying the Sparko discrete opamps in your Ultra DAC Larry until I try them out here first.

I do note there is some input current flow in these devices as they are bipolar inputs and in your DAC we are using a fet input device (OPA627) that does not have this issue.

I am not certain how this will interact with the D to A chip ahead of the op-amp.  The device is used as a current to voltage amplifier in the Philips based chip set design.  You might want to bring the DAC over and let us try it while monitoring the circuit as we bring it up on our AC variac to make sure nothing bad happens.

Regards,

Frank

Input bias current should not cause any problems.  Input bias current will be supplied to the devices from the I output of the DAC.  Be careful using a variac to bring up a system.  The digital ICs might get under-voltaged and latch up.  Slow dV/dT on VCC rails will occasionally give one grief.

I would expect to see slew induced distortion when a sparko opamp is substituted for an OPA 627 or OPA 637 in an I/V application.
Scotty

There is an equation that can be used to calculate the slew rate requirement of a device if we know the maximum frequency and the peak amplitude of the signal that the device must amplify.  This equation is -

Required Slew Rate (in V/µS)  =  2π F Vpk / 1,000,000

We divide by 1 million to get an answer in volts / microsecond.

Most op amps in line level circuits process signal amplitudes of a few volts peak.  Typically, these op amps are supplied from something like ± 15 V, so it’s impossible for them to process signals much beyond 10 or 12 volts peak anyway due to the limitation of the power supply rails.  (Headroom) The upper limit of audio frequencies is widely considered to be around 20KHz, but for the sake of discussion lets call it 160KHz, which is 3 octaves higher than is presumed to be audible by the human ear.  So how much slew rate is required of an op amp to reproduce a 10V peak signal at 160KHz?   Turns out, its  10V/µS.  If we get more reasonable, and calculate a slew rate requirement for 5V peak at 50KHz, we only need a paltry 1.5V/ µS slew rate device to accomplish this.

Perhaps I misunderstand slew rate distortion, but under mathematical inspection it would appear to be a non issue with op amps.  Power amps are somewhat of a different story as they must swing far more peak voltages.

Hope this helps.

Andrew

#### I.Greyhound Fan

##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #22 on: 18 May 2014, 12:43 am »
I received my op amps and took my AVA Ultra II hybrid SS/Tube DAC over to Mr. Van Alstine's place and we installed them and tested them to make sure they were compatible.  They checked out fine and replaced my Burr Brown 0627's.

Here are my initial impressions-

Compared to the 0627's, they have a little more clarity, detail and resolution.  Treble is slightly more forward and sounds a bit better.  There is a bit more air and transparency.  Sound stage is slightly wider.  The attack is crisper.  The midrange has more air and has a lighter sound than the 0627's because of this,  I actually preferred the fuller midrange on the 0627's which is deeper and fuller sounding (I am not implying that the midrange is thin with the Sparko's, its just that I love the full lush midrange of my BAT preamp).  The 0627's may have a slight edge in bass depth.  The Sparko's sound a bit brighter compared to the 0627's.  The overall improved detail, resolution and clarity was impressive though.

I like the Sparko's and I think that they would be an excellent upgrade over the 0627's in the right system. I  prefer a slightly warmer and darker sound with a deep midrange so I will probably stick with the 0627's until I decide to upgrade my DAC.  I will however give the Sparko's about 25 hours of play time to see if the sound changes any.

My system components are a Pass X250 amp, BAT VK-51se preamp, Magnepan 1.6 speakers, Martin Logan sub, Music Hall 25.2 CDP as a transport and the AVA Ultra II dac.  Cardas Parsec XLR cables and Silnote IC's.
« Last Edit: 20 May 2014, 04:08 pm by I.Greyhound Fan »

#### sparko311

• Jr. Member
• Posts: 12
##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #23 on: 8 Jun 2014, 07:26 pm »
TnT Audio Magazine of the UK has reviewed the Sparkos Labs SS3602 Discrete Op Amp in a Maverick Audio D2 DAC.  To see the full review, please visit -

http://sparkoslabs.com/ss3602-discrete-op-amp-reviews-mavrick-audio-dac-tnt-audio/

#### sparko311

• Jr. Member
• Posts: 12
##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #24 on: 11 Sep 2014, 09:23 pm »
Review of Sparkos Labs Discrete Op Amps by Mono & Stereo Magazine.

http://sparkoslabs.com/discrete-op-amp-review-mono-stereo-magazine/

#### Bill O'Connell

• Industry Participant
• Posts: 656
• Retired . Music Lover
##### Re: New Discrete Op Amps From Sparkos Labs
« Reply #25 on: 24 Dec 2014, 06:36 am »
The Sparko Labs discrete op-amps sound fantastic in our Eastern Electric Supreme DAC. Highly recommended