AudioCircle
The Commercial Zone => Industry Introductions => Topic started by: sparko311 on 3 May 2014, 09:18 pm
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Hello. Andrew Sparks from Sparkos Labs here. We have a new discrete op amp product that launched a few months ago. It features all class A biasing - including the output stage, Two Pole Compensation, very low noise, and DIP 8 compatible packaging. This device has a full data sheet and is available as a single or dual op amp. It can be used to upgrade virtually any audio op amp in your system, and is great for new or DIY designs. For more info, reviews, white papers, and a full datasheet, please visit
http://sparkoslabs.com/discrete-op-amps/
(http://www.audiocircle.com/image.php?id=98837)
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Hello. Andrew Sparks from Sparkos Labs here. We have a new discrete op amp product that launched a few months ago. It features all class A biasing - including the output stage, Two Pole Compensation, very low noise, and DIP 8 compatible packaging. This device has a full data sheet and is available as a single or dual op amp. It can be used to upgrade virtually any audio op amp in your system, and is great for new or DIY designs. For more info, reviews, white papers, and a full datasheet, please visit
http://sparkoslabs.com/discrete-op-amps/
(http://www.audiocircle.com/image.php?id=98837)
Hi Andrew, welcome to Audio Circle. These look very interesting to me, may have to pick up some to play with one of these days.
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Hi Andrew,
Very interesting couple of devices you have here, and you have engineering specifications too! Just try finding any of those in the capacitor discussion threads herein. :)
Anyway I do use high quality single linear op-amps in some of my solid state preamps and phono preamps, typically OPA627s.
I would sure like to acquire six of your singles for a good trial evaluation in my lab. Where does the price break begin for orders more than one ($39)?
Frank Van Alstine
avahifi.com
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Hi Andrew,
Very interesting couple of devices you have here, and you have engineering specifications too! Just try finding any of those in the capacitor discussion threads herein. :)
Anyway I do use high quality single linear op-amps in some of my solid state preamps and phono preamps, typically OPA627s.
I would sure like to acquire six of your singles for a good trial evaluation in my lab. Where does the price break begin for orders more than one ($39)?
Frank Van Alstine
avahifi.com
He has the full data sheet on his web page. Here is the link: http://sparkoslabs.com/wp-content/uploads/2013/12/SS3601_SS3602.pdf (http://sparkoslabs.com/wp-content/uploads/2013/12/SS3601_SS3602.pdf)
Here is the simplified schematic from the data sheet:
(http://www.audiocircle.com/image.php?id=98996)
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Just so everyone knows, I am in no way affiliated with Sparkos labs. And that is a good thing for Sparkos Labs. :D
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Hi Andrew,
Very interesting couple of devices you have here, and you have engineering specifications too! Just try finding any of those in the capacitor discussion threads herein. :)
Anyway I do use high quality single linear op-amps in some of my solid state preamps and phono preamps, typically OPA627s.
I would sure like to acquire six of your singles for a good trial evaluation in my lab. Where does the price break begin for orders more than one ($39)?
Frank Van Alstine
avahifi.com
Frank, do you think that they would work in my Ultra Plus DAC to replace my 0627 OA's? I would be willing to give them a try.
Regards,
Larry S.
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The singles should be a drop in replacement for the OPA627s we use. Whether they are more useful musically remains to be tested by us. I have not had a response to my request above yet.
Frank
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Hi guys. Thanks for the warm welcomes. The SS3601 is what you need to replace a OPA627. Im doing 10% off all this month, but Ill give you guys from the forum here a better deal than that though! I see some of you have sent me emails to my site, Im going to answer them just as soon as I make this post here. If anyone else is interested in trying out some of these devices, just let me know!
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Hi guys. Thanks for the warm welcomes. The SS3601 is what you need to replace a OPA627. Im doing 10% off all this month, but Ill give you guys from the forum here a better deal than that though! I see some of you have sent me emails to my site, Im going to answer them just as soon as I make this post here. If anyone else is interested in trying out some of these devices, just let me know!
I'd be very interested in trying these. I have Burson's (2 duals, and 2 singles) in my DAC. The biggest issue for me is that I can't properly fit my cover on with the Burson's. These would be great in that regard!
What's the best way to contact you?
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Frank, I think that I will order a pair and try them out.
Regards,
Larry
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I'd be very interested in trying these. I have Burson's (2 duals, and 2 singles) in my DAC. The biggest issue for me is that I can't properly fit my cover on with the Burson's. These would be great in that regard!
What's the best way to contact you?
The best way to get a hold of me is by submitting a contact form on my website. Here is a link
http://sparkoslabs.com/contact/
Thanks!
Andrew
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Andrew:
What's the story on the low gain version? Did you just up the value of the emitter resistors or current source on the input stage? Is it better suited for certain applications?
Tom
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Is there any chance that it might become available with a 40v/us slew rate and symmetrical slewing behavior.
Scotty
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Andrew:
What's the story on the low gain version? Did you just up the value of the emitter resistors or current source on the input stage? Is it better suited for certain applications?
Tom
The low gain version is sort of "on hold" at this point. Simply raising the RE resistors in the input differential worsens the noise performance - so it was not done in this way. Instead, gain was reduced by changing the VAS to a single device (rather than darlington) and then resistively loading it. Ive been too busy lately to bring all of that to fruition.
Is there any chance that it might become available with a 40v/us slew rate and symmetrical slewing behavior.
Scotty
Asymmetric slewing is very common in both discrete and IC op amps. IT's virtually guaranteed anytime one uses a constant current source to load a current limited VAS stage. Looking at the posted schematic, negative slewing is dictated by the current sink Ivas and the the compensation components. Positive slewing is dictated by the VAS current limit, and the compensation components. The VAS current limit must be set above its normal operating current (that is dictated by its current sink Ivas) to ensure it doesnt current limit during normal operation. The extra current available out of the VAS that is not available out of its current sink makes the positive slew rate faster. Most op amps work this way, but its not always specified. Ive seen people advertise the higher speed direction or an average of the two. Not me though. I believe in full disclosure. :)
Symmetrical slewing is achievable if one uses "mirror image" architecture for input stages and the VAS. I spent a fair amount of time investigating this topology when I was developing my devices. The problem with loading a VAS with another VAS (rather than loading with a current source) is that the VAS standing current is impossible to control. Loading the input differential with current mirrors is not possible either with mirror a imaged VAS stage. (it is possible, but not without great pain and a complex servo system) In order to work with reasonable complexity, the current mirror for the input pair must be replaced with common resistors to establish proper VAS biasing conditions. For me, not using a current mirror to load the input diff pair was not acceptable. The drawbacks of not current mirroring outweighed the benefits of symmetrical slewing and mirror image topology.
If you are interested, I wrote a technical paper that talks about the tradeoffs of slew rate, bandwidth, and gain. I humbly put forth the claim that excessively high bandwidths and slew rates are not required for audio op amps, and in fact become problematic when excessively high. The reason people prefer high speeds and bandwidths is actually due to the loop gain associated with such devices, as bandwidth, speed, and gain are all interrelated and interact with one another via the compensation. Anyway, its a good read, if you are interested. The paper can be found here.
http://sparkoslabs.com/audio-op-amps-gain-seek-bandwidth/
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I ordered a half a dozen of the singles to try in both my Vision phono preamp and in the line stages of my solid state preamplifiers. In both cases the existing OPA627s are isolated from real world loads by LME49600 current buffers.
One thing I am interested in is seeing if these discrete op-amps improve bass linearity as they should not suffer from low frequency thermal feedback distortion as all monolithic op-amps do.
The mechanism for this is that the standard op-amp is build on a single silicon die. The voltage amplifier drives the current amplifier which generates heat which feeds back through the common die to the voltage amplifier, changing its temperature and linearity with load and frequency demands. Depending upon the op-amp, this can produce muddy bass. We minimize this effect with the 49600 current buffers so the op-amp output stages do not have to drive real world loads. In theory a discrete op-amp should do even better.
Frank Van Alstine
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I ordered a half a dozen of the singles to try in both my Vision phono preamp and in the line stages of my solid state preamplifiers.
I look forward to your findings.
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I ordered a pair of the singles to try in my AVA Ultra Plus DAC. We will see how it compares the 0627's.
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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
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Thanks Frank, will do!
Regards,
Larry
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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
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Well I may have wasted $68. We will see what happens when I bring the unit over to Frank.
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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
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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.
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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/
(http://www.audiocircle.com/image.php?id=100784)
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Review of Sparkos Labs Discrete Op Amps by Mono & Stereo Magazine.
http://sparkoslabs.com/discrete-op-amp-review-mono-stereo-magazine/
(http://www.audiocircle.com/image.php?id=105182)
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The Sparko Labs discrete op-amps sound fantastic in our Eastern Electric Supreme DAC. Highly recommended
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I just ordered a pair of the 3601's to replace some 5534's in a headphone amp....looking forward to comparing Andrews op amps to Bursons as well..
Alex