Fosgate FAP-T1 mods

[clm811]

Anyone on the forum modify the Fosgate FAP-T1(or T1+)Preamp/Processor yet? Warranties should've expired by now...

It has great circuitry(DAC's and ADC's*), features, and good sound quality; however, the Fosgate's maker seems to have skimped on parts quality in the Power Supply and Analog Audio sections to cut costs.

I have undertaken a three-phase parts upgrade(POOGE), using top-quality parts and will report on the results.

First up is a photo of the stock power supply which uses inexpensive Wincap electrolytics and ceramic bypasses for the audio rails, as well as a generic bridge rectifier.

Any comments or questions are welcome.

-Chas

*see list of digital components at:
http://members.cox.net/alexhardware/IC_database1.htm

[clm811]

Did the following parts upgrades on the main PS board:

1. Removed the ceramic capacitors right before the Bridge rectifiers and replaced with Polypropylene radial caps(orange).

2. Replaced the #1 bridge rectifier with an IXYS FRED bridge.

3. Replaced the ceramic bypass caps with B.G. NX types.

4. Replaced large cheap electrolytics with Nichicon Muse series.

After a couple days running -in, while playing familiar tracks I noticed what I perceive as an improvement in dynamics and it sounds as if the noise floor is lower (silences between notes seem cleaner); Overall a subtle but noticeable improvement.

Next up is Phase 2, the capacitors around the voltage regulators on the audio board...

-chas

[clm811]

Phase 2
Here is a photo of the main audio board, which uses inexpensive electrolytic capacitors and ceramic bypasses both before and after the voltage regulators, which are decently decoupled otherwise.

There is definitely an opportunity here for improvements in both quality and quantity of capacitance used here, in my opinion.

I will be selecting the parts on the basis of cost-to-benefit as perceived from prior experience with disc player and power amp mods.

-chas

[clm811]

Did the following parts upgrades around the voltage regulators on the main audio board:

1. Removed and replaced the large electrolytics with Nichicon Muse series.
2. Replaced ceramic bypass caps with B.G. NX series caps.

Continuing this upgrade will be replacement of the local decoupling and bypass capacitors in the audio section.

-chas

[clm811]

Phase 3
Here is a photo of the audio section, which uses inexpensive electrolytic capacitors and ceramic bypasses for local decoupling and bypasses, along with generic non-polar electrolytics for input and output coupling in the line stage.

Again, another opportunity for better quality parts, as the circuit design is quite nice, using a digitally-controlled analog (resistors) volume control and OPA2134AU op amps.

-chas

[clm811]

Completed these parts upgrades on the main audio board around the audio section:

1. Replaced inexpensive electrolytic caps, used in decoupling network around audio stage, with B.G. FK series and Nichicon Muse series for the other circuits.

2. Replaced ceramic bypass caps with B.G. NX series (all stages).

3. Replaced generic non-polar caps, used for signal input/output coupling, with B.G. N series (front channels).

4. The line stage op amps are biased into class-A, using 4.7k resistors between the output and V-, at about 2.7ma.

BTW, values for many of the power supply decoupling caps were increased from 20-50%, for improved filtering.

Completed unit has been running-in for some time, although I understand that capacitors-especially Black Gates- require some time to sound their best.
I can already tell that the sound has been improved noticeably, especially in clarity, dynamics and image specificity within the broader, deeper soundstage; Furthermore, the sound is now more "open" and, as best as I can describe it, "flows" with an effortlessness reminiscent of good tubed gear, yet retains the bass control and treble clarity of good solid-state.

Once fully broken in I hope to do more critical listening with familiar tracks to see how much better it gets.

Anyone else out there have one of these, and if unmodded, how do you like the sound of the stock unit?

-chas

[chasmo]

Just wanted to update-

My (modded) FAP-T1+ is still running fine after almost two years.

Anyone else attempt/perform mods to their Fosgate FAP-T1+??

[ssnsltd]

hello,
understand this is an old thread, but do you still have the parts list for this mod?
the link is dead.

thanks
david

[Gordon McGregor]

Originally Posted by ssnsltd

hello,
understand this is an old thread, but do you still have the parts list for this mod?
the link is dead.

thanks
david

Here is the list of parts, used in Fosgate AV processors:

Fosgate FAP-T1+
DAC=CS4398; DSP=CS494003; ( http://www.cirrus.com/en/pubs/proBul...400PB_0503.pdf ) OP AMPS=OPA2134; ADC=CS5381 (Fosgate Audionics — Reviews and News from Audioholics)
My recommendation is to replace OPA2134 with OPA627 (need to use special dual sided panels - like for example here ( http://cimarrontechnology.com/single...rpn020302.aspx and here is how it looks on the board http://www.facebook.com/photo.php?fb...type=3&theater ) or OPA827 (good results as well). Replace caps like recommended above.

Fosgate FAP-T1
DAC=CS4396; DSP=CS49326x (http://www.cirrus.com/jp/pubs/appNote/AN163Rev7.pdf ); OP AMPS=AD712; ADC=CS5360 http://www.fosgateaudionics.com/prod..._datasheet.pdf
My recommendation is to replace AD712 with OPA627 (you need to use special dual adapters - like for example here ( http://cimarrontechnology.com/single...rpn020302.aspx and here is how it looks on the board: http://www.facebook.com/photo.php?fb...type=3&theater ) or OPA827 (good results as well). Replace caps like recommended above.


You can also try to use panels and find the best OP AMPS according to your own preference. I am not sure about biasing into class A (need to check this option for the particular used OP AMP; for OPA627 / OPA827 it might not be required), but you can try to do it as well.

The link is dead such as Cox decided to shut down their website service for members, it is a recession time ...