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I wonder if the Hertz version of this amp has the upgraded caps and op amps.
I know Zapco has the ST-2xSQ and ST-4xSQ, both with upgraded opamps and caps. The 2ch isn't on Atrend just yet but I'm watching and waiting. If they don't hurry I'll order up a nvx jad900.5 and do the upgrades myself.
 

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Good idea. I'm currently trying to find a place or person to perform these upgrades for me. If anybody locate a place let me know.
 

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Looks like this is just a matter of desauldering and resauldering? Any shop recommendations in Southern California?

Are the mentioned cap replacements needed if using an external DSP and running the amp full range?
 

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I really want to try the ST-4SQ but I don't know about cutting my power in half. I do like it loud from time to time when the windows are down on the high way.
 

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I know Zapco has the ST-2xSQ and ST-4xSQ, both with upgraded opamps and caps. The 2ch isn't on Atrend just yet but I'm watching and waiting. If they don't hurry I'll order up a nvx jad900.5 and do the upgrades myself.
Concerning Zapco's offerings, the Z-LX series amps (Class A/B) which they have spent time improving on input section to offer high SQ will certainly cost you well over a grand, and as I stated before, if you have the ability, you can do a little rework and rival SQ of offerings 10 times the original price of NVX. And while I understand that rework may be beyond the abilities of some here, it's a DIY project well worth the time. Even Zapco recognizes the sonic benefits of using ELNA SilMic II's in their platform. Make sure you don't deviate from TI's strongly recommended replacement for the TL072 with Burr-Brown OPA1642's and you'll love yourself for it.

Just be mindful, only the Z-LX series uses the upper-end caps and op-amps, (in fact, the OPA1642 is actually better performing in many critical areas than the AD OP275 used in the Z-LX) and the SQ models uses the late 70's bi-polar NE5532, (which is actually on the lower level of performance compared to it's contemporaries) and no ELNA SilMic's.
 

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Concerning Zapco's offerings, the Z-LX series amps (Class A/B) which they have spent time improving on input section to offer high SQ will certainly cost you well over a grand, and as I stated before, if you have the ability, you can do a little rework and rival SQ of offerings 10 times the original price of NVX. And while I understand that rework may be beyond the abilities of some here, it's a DIY project well worth the time. Even Zapco recognizes the sonic benefits of using ELNA SilMic II's in their platform. Make sure you don't deviate from TI's strongly recommended replacement for the TL072 with Burr-Brown OPA1642's and you'll love yourself for it.
Thank you to DeltaB. For those who are not sure what to order i have included my order sheet. Now my qty is for 2 amplifiers modifications, so just cut my qty in half for 1 amp. Now i'm searching for a shop to perform these upgrades.
 

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Check with theamplab.net, not sure if they are willing.
Thanks, I just sent them a RFQ. I will await there response.


***Update*** was quoted $75 a amp.
 

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Yep.
 

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"Eric,

I assume you've done your research to confirm this will indeed work.
I believe $75 per amp seems appropriate for this amount of work. If this works for you, let me know and we can move forward.
Thank you,
Ethan Poissonnier
Co-Owner - Head of Sales - Public Relations
On 8/28/2017 2:50 PM, The Amp Lab wrote:
The Amp Lab
The Amp Lab
Phone: (207) 313-6236
Fax:
Name: Eric Perry
Email: [email protected]
Subject: Amplifier
I would like to submit a RFQ for a simple amp modification. I want to have all 30 signal electrolytic caps replaced with ELNA's SILMIC II silks. And all 10 JFET op-amp TL072, replaced with the Burr-Brown OPA-1642. Basically upgrading the front stage. I will supply the components, I just want to know the labor cost.

Amp: NVX JAD 900.5
QTY: 2
Upgraded OP-amp: OPA1642AIDR
QTY: 10 per amplifier
Upgraded 10uF Cap: Aluminum Electrolytic Capacitors - Leaded 10uF 35V 20% Audio SILMIC II
QTY: 20 per amplifier
Upgraded 22uF Cap: Aluminum Electrolytic Capacitors - Leaded 22uF 35V 20% Audio SILMIC II
QTY: 10 per amplifier

---
Thank you for using our services
The Amp Lab"
 

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"Eric,

I assume you've done your research to confirm this will indeed work.
I believe $75 per amp seems appropriate for this amount of work. If this works for you, let me know and we can move forward.
Thank you,
Ethan Poissonnier
Co-Owner - Head of Sales - Public Relations
On 8/28/2017 2:50 PM, The Amp Lab wrote:
The Amp Lab
The Amp Lab
Phone: (207) 313-6236
Fax:
Name: Eric Perry
Email: [email protected]
Subject: Amplifier
I would like to submit a RFQ for a simple amp modification. I want to have all 30 signal electrolytic caps replaced with ELNA's SILMIC II silks. And all 10 JFET op-amp TL072, replaced with the Burr-Brown OPA-1642. Basically upgrading the front stage. I will supply the components, I just want to know the labor cost.

Amp: NVX JAD 900.5
QTY: 2
Upgraded OP-amp: OPA1642AIDR
QTY: 10 per amplifier
Upgraded 10uF Cap: Aluminum Electrolytic Capacitors - Leaded 10uF 35V 20% Audio SILMIC II
QTY: 20 per amplifier
Upgraded 22uF Cap: Aluminum Electrolytic Capacitors - Leaded 22uF 35V 20% Audio SILMIC II
QTY: 10 per amplifier

---
Thank you for using our services
The Amp Lab"
Just for you and Amp Lab's concern, here is something for your viewing pleasure concerning the proper selection of op amps for this modification.

https://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/upgrading-op-amps-in-audio-equipment
 

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My system starts with a NVX JAD 900.5, which internal design and boards are shared by a number of companies, both big name, as well as private and not-so-big vendors. Upon receipt, I opened the case to examine components and solder quality, and found what is ever present in auto amps, and that is signal components, like op-amps and electrolytic caps of poor quality and inexpensive price, seriously degrading the ability of the amp to produce true high-quality sound. There is a HUGE difference between noise, and being-there type of reproduction. Loud isn't better. It's just noisy.

One of these in this amp, was the use of TI's TL072 op amps for all buffering and signal conditioning. This device, produced since the 70's was one of the first JFET op-amps widely used for high-impedance input circuits, and was quickly overshadowed by the NE5532 for audio usage. This $0.37 part is best used to control a variable speed motor, and not audio, since there are numerous selections of much better audio quality. With 18nV of noise, it produces a constant hiss that is audible in the output section. And while it's slew speed is 13V/us, which is considered tabletop radio quality, the most important factor of the TL072, is the phase shift over the audio spectrum, which changes more than 120 degrees over just a few octaves. In fact, when driven at modest voltages, it can change polarity, causing 180 degree cancellation of frequencies. (phase reversal) This is very bad for your audio, in fact, it's unacceptable. Needless to say, the bean-counters, who opted for least cost, gave it to us with no regard to what is given up in audio quality. This is indicative of all amps on the market today, even in the home audio arena. (My high-end Yamaha AVENTAGE RX-A2030 even suffered from this cost cutting oversight in using low-cost poor-performing op-amps)

So what I've done is to use TI's recommended replacement for input designs that have utilized JFET op-amps, like the TL072, using the Burr-Brown OPA-1642. This op-amp brings with it a number of really impressive performance upgrades. One, comparing it to the TL072, who's THD was 0.003%, with the new, gains me a very impressive 0.00005% total THD, with less than 1/4 of the noise. It's slew rate is almost double of that of the TL072, and gets into the 20V/us slew rate, which can handle complex audio without losing detail. It takes less current to run it, and makes a good drop in replacement without having to redesign the circuit. The real advantage to this change, comes from the most important factor, and that is phase. Your ears are incredibly sensitive to phase, and audio phase is one of the most important things in creating sinusoidal waves that sound "real". The OPA-1642 is phase stable (no shift) throughout the entire audio spectrum all the way up into the MHz range. The soundstage with the new op-amps is nothing short of incredible, and places it in a performance category with some of the finest home audio out there. Channel separation went from around 90dB of separation to almost 130dB, and CMRR went from -86dB to -128dB. Talk about now having an extremely quiet, and low distortion amp. Mono blocks don't perform better than this folks.

All of the signal electrolytic caps were replaced with ELNA's SILMIC II silks, which has become the defacto-standard of audio signal caps these days, and bring with them a very warm and inviting sound.

All of this was done with a little rework time and less than $50. Now, this $250 investment can rival performance of amps 10 times it's cost. The finest investment one can make in their car audio systems, is the attention to detail in the input section of their amplifier, and since all amps suffer this, is the first place to spend attention to really create a soundstage in your vehicle that will rival any out there. It's all about making a correctly phased and uncolored sinusoidal wave for your ear. The manufacturer's bean-counter ripped you off.

I wonder if anyone could go to a manufacturer and make a custom order with the changes that you made. Do you think a manufacturer would make those alterations (that you did) in a special order? This way, maybe someone could get that upgraded amp and keep the manufacturer's warranty...maybe.
 

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No. Those Amps are made overseas and shipped here.
 

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Is there any modification you recommend with the power supply? or do you think its pretty stout as is?
 
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