The Carver C-4000 and 4000t are similar but also very different. However, restoring them and upgrading them are similar enough to include together. These preamps require a complete overhaul after nearly 40 years of use. We replace all the electrolytic capacitors with either high temp, long life type, bi-polar or low ESR where appropriate. We tear the unit down completely and recondition all the wipers on the attenuation knobs and buttons. Some units require factory updates and power supply fixes. All of these units also require the phono amps, time delay, auto correlator and sonic holography circuits to be tuned and calibrated. The unit is also cleaned and polished, fully tested and we listen to it to ensure it sounds better than ever. The results of our work are stunning!

Gundry Filter Circuit for C-4000/4000t

Sonic Holography Frequency Response (stock):

Sonic Holography Frequency Response With Gundry:

Note the two 'dips'. This enhanced equalization expands the holographic imaging of the SH processing to our natural, non-linear perception of sound location.

It's function is to attenuate frequencies which our ears are naturally very sensitive too, such as baby crying and sirens. By adjusting the frequency response of some audio processing, such as Sonic Holography, the result is a better sound image, especially at high volume levels where certain mid-range frequencies dominate our ear/brain system and smear our perception of depth and detail in the music.

Signal Path Upgrade

The line out amp stage and tone circuits are pretty simple and elegant for these preamps. But if you want even tighter response and lower noise, go for this upgrade to make the unit even more blissful to the ears. We will install high grade op-amps in place of the stock RC4136 chips, 1% metal film resistors and Polypropylene Capacitors in critical areas of the Line Out amp and Tone Control in addition to the already impressive components used for the Base Restore.

Wi-Fi DAC integration 

[not available at this time]

High quality parts and expert workmanship.

Gundry Filter board installed on the Sonic Holography PCB.

New LEDs for the faceplate.

C-4000 Surround Sound Delay Option:

The C-4000 utilizes a surround sound option that incorporates a delay circuit. The Left and Right channels are summed, then processed through a SAD1024 or SAD4096 IC chip (the C-4000 used either, depending on availability at the time, and they are NOT interchangeable). From there, the signal is conditioned, filtered and equalized - then sent to the 7W power amp for the Left Back, Right back and Center back speaker outputs, as well as line level out (L and R only). If this feature does not work, it is 90% of the time the fault of this chip. The chip is decades out of production, and so the only way to fix it is to install a delay circuit retrofit. Nevertheless, it would be a good idea to replace your delay circuit IC as part of the restore because it looks like all of these chips eventually fail. This retrofit is ONLY available if we service your unit. The surround sound circuit is very sophisticated and must be calibrated and aligned after the retrofit is installed. There is also the probability that something other than this chip is wrong, and if that is the case, there are vast circuits that need to be checked, including the power amp, since the line level outputs are tapped from the power amp output.

Restore Price: $450

Gundry Filter for Sonic Holography: $75

Signal Path Upgrade: $100

LED color change: $100

Remote control Volume: $250

IEC socket: $75

Delay Circuit SAD1024/4096 retrofit upgrade: $75

Comes with Nelion Audio 3 year parts and labor warranty.