Yamaha C-4 Vintage Preamplifier - Vinyl Lovers Dream Preamp, Serviced

Description

SkyFi Audio - Curators of Vintage Audio Gear
SkyFi Audio is a small startup business specializing in the purchase, reconditioning, and reselling of high end audio equipment. We only buy equipment that we admire and are passionate about. No mid-fi, no gimmicks, no junk.
Each piece of equipment is cosmetically restored and fully tested in our well-equipped lab by an engineer with 30+ years of experience in the HiFi world. If it does not meet or exceed the original manufactures specifications, it will not be sold. We are very selective about the equipment we purchase, focusing on mostly analog, high-build quality, American, and European built units.
Through our sister company, which is an authorized dealer for McIntosh, Audio Research, Sonus Faber, ClearAudio, Project, and Sony ES, we have access to OEM parts, service, and support.
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This listing is for a fine example of the vintage Yamaha C-4 Stereo Control Amplifier (Preamplifier).
This specific C-4 underwent a routine service here at SkyFi which included a cleaning all of the controls, re-lamping, replacement of several out of spec parts in the power supply circuitry, and adjustment of the regulated supply voltages to official Yamaha service manual spec.
All functions were tested and are working as intended.
In addition, a long term test of this preamp in our "test rig" as a test preamp for many other amps undergoing testing yielded great results.
Please note this C-4 is sold AS IS.
This C-4 has minor cosmetic blemishes (see images).
It is currently functional but additional service is suggested for daily use due to its age.
Included with your purchase is just the Yamaha C-4 Preamplifier itself as shown in our photos.
Not Included:
No Manual/Box/Audio Video Cables or *any* other accessories.
The SkyFi Testing Process for Preamplifiers:
We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.
When we first power on a preamplifier we connect its RCA output to a Sencore PA81 Power Analyzer which simulates real world loading conditions and gives us an oscilloscope interface. The first order of business is checking that the volume control works smoothly throughout its entire range with acceptable channel balance. This is accomplished by feeding a 1KHz sine wave into one of the preamp’s line level inputs while monitoring the preamp’s output on an oscilloscope. We then switch to a 1KHz square wave to test the tone controls, loudness function, and filters where applicable. During this step we are watching for equal alteration of the test signal by both channels. This also helps us identify dirty controls that will need treatment. Once the basic line stage functions are verified, we test each input individually. This is especially important for devices that use relays to select their sources. If the preamp is equipped with a phono stage we test that as well. We use an inverse RIAA filter which allows us to feed a reference test signal into the phono input with the proper RIAA equalization and level. A square wave or sine sweep is used to verify that the device’s phono stage is faithfully reproducing the RIAA curve. If the preamp under test has balanced inputs and/or outputs these are tested as well.
We finish up our bench testing with a listening test with our bench amplifier and reference speakers. During this test we check for hum or hiss that may not have shown up in earlier testing. We also check that all of the tone controls and filters perform as expected. If the preamplifier has remote control functions these are also tested. Preamps with tube circuits or complicated power supply topologies are connected at our long term test rig for extended stress testing under real world conditions.
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PURCHASING GUIDELINES:
1)
This item will be professionally packaged and insured for safe transit to your home unless you opt for local pickup from our shop. All local pickup items are only wrapped in industrial strength clear stretch wrap if the original manufacturer packaging is unavailable.
Local pickup is available in Glen Rock, NJ, just a half hour drive from Midtown Manhattan, with convenient parking near our building.
If we don’t have the original manufacture’s packaging, we use heavy duty double-ply corrugated boxes with custom made to your item SealedAir Instapak expanding foam custom inserts. In many cases this has proven to be better than the original packaging!
We also use high quality fiber reinforced tape to seal our packages. Lightweight items will be bubble wrapped and shipped in a high-quality box.
2)
We do not review or accept any offers that do not go through the official eBay system. We have too many items for sale and it is nearly impossible to keep track of offers outside of the official system. Please do not message, email, or text any offers.
3)
All listings are eligible for the eBay Global Shipping Program, unless the item exceeds the maximum weight/price requirements to your country. If this is the case simply message us via eBay as we accept bank wire transfers for international payments and frequently ship worldwide via UPS.
4)
Please ensure your shipping address is correct within eBay as we will ONLY ship to the eBay/PayPal Confirmed Shipping Address.
No exceptions.
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) eBay may charge and collect sales tax to your state/jurisdiction. Please understand we have no control over this.
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