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Marantz 2325 Stereo Receiver - INCREDIBLE For Sale


Marantz 2325 Stereo Receiver - INCREDIBLE
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Marantz 2325 Stereo Receiver - INCREDIBLE:
$3075.00

Marantz 2325 Stereophonic Receiver

Description:

The most powerful of all Marantz stereophonic receivers from 1974 through 1975, and so popular that it continued to be manufactured through the end of 1977, the Marantz 2325 is truly a classic audio masterpiece in every sense of the word. Not for the financially faint of heart, the 2325 set you back $799.95 at retail in 1974 dollars, fully equivalent to shelling out over $3,800 today! But that\'s what you paid if you wanted the best. The 2325 boasts a very conservative power rating of 125 watts per channel into an 8-Ohm load, with a ridiculously low (even by today\'s standards) 0.15% distortion spec at full rated output. In fact, the unit was bench-tested by a popular hifi magazine at half that distortion rating. And since the way output power is measured and advertised has changed significantly over the years, I\'d say this 125 watt per channel Marantz could easily keep pace with modern units rated at twice the power - without even breaking a sweat.

The 2325 was one of the few Marantz models offered with a cool little perk - a fully equipped, on-board Dolby™ encoding and decoding noise reduction system. Not just a useless IC chip, mind you, this is sophisticated noise reduction circuitry, enabling specific Dolby™ threshold calibration of both recording and playback - it even comes with a 400Hz reference tone generator! With the 2325, you could (and still can) knock out most of the tape hiss on recordings made on decks having no noise reduction capability at all. Take note, reel-to-reel fans!

Finally, the sound quality. You can throw specs all over the place, but some units just sound better than others. Back when I was a kid selling audio in the late \'70\'s (yup, I sold Marantz gear back in the good ol\' days), we had both the Marantz 2325 and the monster 2500 on the display shelf. To me, the 2500 was way cooler looking, with the scope display and gold-toned tuning dial, but when it came to sound, the 2325 just had a smoother, more pleasant, more musical sound. The 2500, impressive at it was, to me had a more mechanical, possibly more \"precise\" sound, but the bottom line was that I could only listen to it for a little while before listener\'s fatigue set in. By contrast, I could listen to the 2325 all day...so I bought one! And many days, I did listen to it all day! If you\'re in the market for one of the best-built, best-sounding receivers ever made, a unit that will be music to your ears for years to come, you can\'t do much better than the legendary Marantz 2325.

Condition:

This receiver is inamazing cosmetic condition - just a few tiny nicks around one of the faceplate hex bolts keep this one from being absolutely perfect. Not much more to say here - I\'ve provided plenty of high-res pictures, so you can check out every inch for yourself. This is a newer-serialed 2325, so the older crack-prone metal and plastic speaker terminals have been upgraded to the much more durable fully molded ones. The original owner took excellent care of this receiver, to the point of keeping all of the original boxes, packing, and paperwork, which is being passed on to the lucky winner of this sale.

Functionally, this unit is a perfect 10. All of the old incandescent bulbs have been replaced with cool-running, non-flickering lifetime LEDs, and all of the old, yellowed diffusion paper has been replaced.. ALL electrolytic and ALL tantalum capacitors on ALL boards have been replaced, including the big filter caps, with components far exceeding the quality and durability of the original parts. The troublesome speaker relay has been replaced with new, all controls and switches have been cleaned and lubricated, and preventative maintenance has been performed in many other areas to ensure that this receiver will perform at its peak for decades to come. Full details of all restoration services are listed below.

As a result of the above attention, this 2325 works like it did the day it left the factory. Due to the LED conversion, all the dial and indicator lights are bright and clear, the controls and switches work smoothly and are noise-free; the connections on the back are tight, shiny, and like new. The amp is wonderfully quiet at idle, but has enough power to dim the lights to the beat if you insist on concert-level volumes. All of the original factory-matched output and driver transistors are present, so that "magical Marantz sound" remains uncompromised. The tuning is wonderfully sensitive with near-full signal strength meter deflection on most of my local FM stations - using a 10" jumper wire wire as an antenna!! Even the Dolby™ circuitry functions perfectly in all modes. All-in-all, a near-museum-quality example of Marantz craftsmanship built when they were at the top of their game - literally the best of the best. Don\'t miss out on this outstanding piece!

Restoration Services:

I have been working on Marantz receivers for well over 30 years, and have given this one a complete service update, including the following:

  • ALL original electrolytic and tantalum capacitors on all boards (including tuner circuitry) replaced with top-quality components:
    • All electrolytic capacitors in the signal path upgraded to Elna "Silmic II" audio-grade capacitors
    • Power supply and most other small electrolytics replaced with Panasonic "FC" series hi-temp (105C) capacitors
    • All electrolytics 1µF or smaller replaced with Panasonic polyester film capacitors
    • Original 15,000 µf 70V filter caps replaced with new Vishay-Spague 18,000 µf 75V
  • ALL original incandescent bulbs replaced with cool-running lifetime LEDs:
    • All dial lamps and meter lamps replaced with triple-element, non-flickering snap-in type LED illumination
    • All bi-pin indicator lamps replaced with dual-element LED devices
    • Illuminated tuning needle bulb replaced with LED
    • All LEDs easily reversible to stock incandescent if desired - no permanent circuit changes made
  • Regulated power supply board completely rebuilt - all new electrolytic caps, transistors and diodes (standard and Zener) installed
  • Yellowed meter and tuning scale diffusion paper replaced with new white rag vellum
  • Output and final stage driver devices removed, cleaned, and remounted with new insulators and fresh thermal compound
  • Main rail power rectifiers removed, cleaned and reinstalled using fresh thermal compound
  • Speaker relay replaced with brand new Omron equivalent
  • Differential pair transistors on both amp boards replaced with exact-matched-hfe equivalents
  • Trouble-probe "VD" diodes on phono, amp, and buffer boards replaced with new
  • All rotary and push-button switches cleaned twice with DeOxit G5 Gold
  • All potentiometers flushed twice with DeOxit FaderLube F5
  • Tuning capacitor bearings cleaned and lubricated
  • Tuning dial cord re-tensioned to ensure slip-free operation
  • Cleaned and re-lubed tuning pointer track and all dial cord pulleys
  • Chassis metal cleaned and protectant applied
  • ALL circuit boards carefully cleaned, inspected and any suspect solder connections reflowed
  • High-quality Kester silver-bearing solder used in all part replacements and re-solder work
  • FM discriminator coil peaked and local oscillator aligned for perfect tuning dial accuracy
  • DC offset zeroed and idle current set to factory specs (after one-hour warm-up/stabilization period)
  • All RCA-style inputs, dubbing jacks and headphone jack internally and externally cleaned and deoxidized
  • 90-day full parts and labor guarantee included *

    Serial number on this unit is 10431 J4. She was "born" on March 4, 1976.

    Paperwork included in the sale. The Handbook of Instructions, fold-out schematic, and warranty sheet are originals that came with this receiver. The service manual and promotional brochure are excellent copies, duplex printed on a professional Xerox solid-ink printer.

    These are all of the old parts that have been replaced in this restoration. The winning buyer is welcome to them at their option - please let me know at sale end.

    A shot with the "hood up". Every cylindrical (electrolytic) capacitor you see is brand new, and better than the part it replaced.

    A detail shot of the inside. This 2325 is as beautiful on the inside as she is on the outside. All electrolytic capacitors you see are brand new. In fact, ALL electrolytic and tantalum capacitors have been replaced with top quality new equivalents, most with higher voltage ratings and/or higher temperature ratings.

    From the right side. The chassis and all assemblies have been carefully cleaned and preserved. All output transistors are the original factory-matched components.

    Restoration Notes:

    The regulated power supply board, before and after. This board is usually the first thing to go in these vintage receivers, due to the high heat it generates. All electrolytic caps have been replaced with Panasonic "FC series" caps, notable for their high quality and high temperature tolerance (105°C). The tired old power transistors have been replaced with modern, higher-current-capable On-Semi devices and remounted with new insulators and fresh thermal compound. All of the smaller transistors have also been replaced with new superior devices, as have all of the standard and voltage-regulating diodes. Finally, the speaker relay has been replaced with a brand new Omron replacement, and all solder joints on the bottom of the board have been inspected and reflowed where necessary.

    Here, we\'re applying fresh thermal transfer compound to the two high-current rectifying devices responsible for supplying the final output transistors. The cooler these guys run, the better. Here are the same devices, cleaned and remounted on their heat sink.

    This is a shot of the main filter capacitors, old and new. The new devices are the blue ones on the left. Modern design and manufacturing techniques have enabled devices with similar characteristics to be manufactured in much smaller packages. The new smaller filter caps offer 20% more capacitance, have a higher working voltage limit, and can handle 12% more heat than the old black ones on the right! The new filters, installed. Marantz doesn\'t mess around here - some of the highest current in the receiver passes through these terminals, and all connections are designed to handle it. Good quality spade connectors are used - no flimsy wire-wrapped posts here! This the phono preamp board. This board is responsible for amplifying the tiny voltages generated by the magnetic phono cartridge in your turntable to the point that the rest of the receiver can use it. Any noise or signal degradation here becomes immediately unacceptable. That\'s why, in addition to replacing the old electrolytic caps, were refreshing a few more things as well... The recapped phono board. Highly-regarded audiophile-grade audio path in this restoration, so on all boards involved with processing the audio signal (e.g., tone, buffer, phone, Dolby, filter, and power amp boards), you\'ll see SilmicII\'s installed. Any old electrolytic or tantalum capacitors under 1 µµF were replaced with high-quality, non-polarized Panasonic polypropylene film capacitors - those reddish brown cube-shaped devices. The two notoriously failure-prone 2SC458 transistors flanking the large smoothing cap at left have been replaced with low-noise Fairchilds; and the troublesome varistor to the left of the round metal trimmers has been replaced with equivalent serial diodes. Vinyl lovers, you\'re in for a treat! Here\'s the tone amp board - responsible for handling bass, mid, treble, turnover, and balance adjustments. As a result, this board is usually in the signal path, and problems here can seriously affect sound quality. Notice the small round blue devices on this board - these are tantalum capacitors. Tantalums were favored in vintage equipment during the \'70\'s due to their low leakage and their ability to provide high capacitance in a small, sealed package. Over the years, however, audiophiles have come to realize that tantalum caps in the signal path can sometimes impart a harshness to the sound, and conventional wisdom has been to replace them with audio-grade electrolytics - like the Elna Silmic II\'s. And, after receiving some TLC. The old electrolytics and tantalums have all been replaced with Silmic II\'s, all small electrolytics 1 µF and under have been replaced by Panasonic poly films. The tone and balance controls have been repeatedly sluiced with Caig Faderlube; the tone turnover switch has been cleaned and preserved with Caig Deoxit Gold G5. Finally, the underside of the board has been carefully inspected - any suspicious solder joints have been reflowed, and any excess flux (sticky stuff used in the wave-soldering process to help the solder adhere better) has been removed. Oh yes - one more thing to do on the tone amp board. This is the main connection bus. Oxidation of these pins can have as detrimental an effect on sound quality as aging capacitors and poor solder joints. The third pin from the right is particularly yucky... Much better. A pencil eraser, pushed onto each pin and spun back and forth several times works well here. Before reattaching the plug when we reinstall this board, we\'ll spray some Deoxit Gold contact preservative on thee pins to provide the best contact and minimize future oxidation. The FM IF board, before and after "recapping". Most restorers don\'t bother recapping the tuner boards, citing fear that it\'ll throw off the alignment. In fact, NOT replacing the caps on these boards is far more likely to cause tuner problems, as a single failed capacitor can destroy your FM reception. After recapping the tuner boards and a brief touch-up alignment, the FM reception on this 2325 improved dramatically. Ahhh, the Dolby noise reduction board. You may very well never use your Dolby circuitry, but I don\'t care. I\'m recapping the Dolby circuit anyway - and this board is PACKED, so it\'s quite fun. The completed Dolby board, with the old capacitors in the background. As this circuitry handles the signal path when it\'s switched in, only audiophile-grade Silmic II\'s are used here. On to the main amplifier boards. In addition to renewing the old capacitors here, the \'differential pair\' (two wrapped devices below) should be replaced to ensure optimum stability. These two thermally coupled transistors control the DC balance of the amplifier circuitry, and if one or both fail, noise and static can ensue, or worse, excessive DC on the signal line can cause your receiver to go into protect mode and shut down the speaker relay (no sound). As differential pair failures are fairly common, any good restorer will simply replace them. Here\'s the new differential pair, installed. These new Fairchild transistors are carefully matched to each other for the best balance, and then shrink wrapped with a little thermal compound between them. This ensures that the circuit balance is properly maintained, even when these transistors heat up under load. As 38-year-old thermal compound has a tendency to dry out and lose effectiveness, each and every transistor on the amplifier board that is mounted to a heat sink is removed, cleaned, and remounted using fresh thermal compound and a brand new mica insulator. Cool transistors are happy transistors, and happy transistors sound the best and last the longest. These are all original, factory matched transistors, and as they are directly in the audio path, they have a direct impact on the sound. We really want to protect these guys, so this extra work is well worth it. More oxidized pins to clean before we reinstall these amp boards, so out with our trusty pencil eraser...

    Now that the main amp boards are done, it\'s time to reinstall them to their heat sinks and reinstall the main output transistors. Before we do this though, we again want to ensure the best possible connections, so both pins of all eight original output devices are carefully cleaned. The old thermal compound is cleaned off of the output devices, and fresh thermal compound is applied. Even this requires care - too much thermal compound is messy and can impede good thermal transfer almost as much as too little compound. A nice, even coat, just slightly translucent, is what we\'re after. Of course. we\'re not going to even think about chancing it with the old mica insulators, so new ones are prepped for installation. The amp boards are complete. These are the original factory-matched output transistors, an important thing to look for if you want to be absolutely sure that the \'Marantz magic\' has never been compromised by potentially inferior third-party devices. And the opposite side of the same board, refreshed and ready to go. Now that the electronics are well in hand, let\'s take a look at restoring that wonderful Marantz blue dial.The first step is to convert all of the current, hot-running, yellowish incandescent bulbs to LED lighting. Below are some of the parts we will use to build the function LEDs - two SMD LED devices and one current limiting resistor per indicator. Here are the completed indicators, finished with white shrink wrap. Each of the little LED elements flickers 60 times per second when connected to the AC current Marantz uses to drive their function lamps, but using two of them back-to-back reduces this to an effective 120 flickers per second - beyond the ability of the human eye to perceive.
    Below, we have the plastic light shroud, discolored and slightly distorted by the heat of a half-dozen incandescent fuse lamps endured over several decades. This is a very common occurrence in 2325s, and this shroud is actually in better shape than most. To restore the shroud\'s reflectivity, white gloss enamel spray paint is applied, after roughing up the shroud\'s surface with #0000 steel wool And, the refreshed shroud back in place, with all of the LEDs installed. Two LED elements per function indicator, three elements per fuse lamp, and one in the pointer - that makes 41 total LEDs used in the conversion! The old yellowed tuning scale and meter diffusion paper has been replaced with brand new rag vellum. Along with the nice white illumination from the LEDs, this helps restore the tuning dial from a faded greenish aqua to the beautiful blue Marantz designers intended. The tuning meters go back in first. And yes, those are brand new caps on each of the meters as well! Pictures just don\'t do it justice - you have to see it in person to really appreciate the beautiful royal blue hue afforded by the LED back-lighting and refreshed diffusion paper. In addition to the improved cosmetics, these LEDs give off almost no heat whatsoever, so you\'ll no longer need to worry about that plastic lamp shroud warping. And, probably the best part - these LEDs have a near 100,000 hour life expectancy, and will likely NEVER need to be replaced ever again! (Well, maybe your great-grandkids might have to worry about it.)

    Adjusting the newly-rebuilt power supply to deliver exactly 35VDC, according to the service manual. Adjusting the amplifiers to "zero-out" any DC voltage at the speaker terminals. Generally, anything within 10 millivolts of zero is acceptable - as you can see we can zero our DC down to under one millivolt on this 2325. This indicates unusual stability in such a powerful receiver.

    Here, we\'re setting the amplifier\'s idle current.This is an important adjustment, and should be done once the receiver has had a chance to warm up - after 30-60 minutes or so. Idle, or "bias" current determines how much juice should be flowing through the output transistors to keep them from completely shutting off - which causes "switching" distortion. Too little current introduces switching distortion; too much current can cause the outputs to overheat and become damaged. Marantz says the ideal idle current setting for this receiver is 15 millivolts. As you can see below, the amplifier in this 2325 is in excellent health, and holds its idle current setting within a few tenths of a millivolt. Okay, now that we\'ve lavished all of this well-deserved attention on this fine receiver, it\'s time to see if she can "deliver the goods". Below is the power output bench test set-up, employing audio generator, oscilloscope, and four large 8-Ohm load resistors. The initial test will be into one set of load resistors, simulating a two-speaker, 8-Ohm load. The second test will add two more load resistors, simulating a four-speaker, 4-Ohm load. Let\'s see how she does... Testing the receiver\'s power output just before clipping, with both channels driven into the two 8-Ohm load resistors. You can see the nice clean 1 KHz sine waves on the scope (one for each channel), and 35.17 VAC on the true RMS voltmeter. Power = E2/R = 1236.9 ÷ 8 = 154.6 Watts. Right channel also measures 155.1 Watts. What a BEAST! Now lets see what she can do into a 4-Ohm load.... Now, the 4-Ohm load test. The reason we test into a 4-Ohm load is because this approximates a the conditions when the receiver is driving a second set of speakers (all four at once). Not all receivers can handle a 4-Ohm load, because when you cut an 8-Ohm load in half, the receiver wants to double its output, leading to tremendous current flow that only the best receivers can handle. In fact, most receiver manufacturers build current limiting circuitry into their output stages to prevent this very thing from happening, so their receivers won\'t provide much more power at 4-Ohms than they will at 8-Ohms. The Marantz 2325 is an obvious exception. Below, we\'ve connected a second set of 8-Ohm load resistors to the first to create a 4-Ohm load, and ran the same test. Left channel power = E2/R = (30.35)2 = 921.1 ÷ 4 = 230.2 Watts! Right channel comes out to 231.9 Watts. WOW! Now you know why you can dim the lights when you crank up a Marantz 2325 into two sets of speakers!

    What You Get:

    • Marantz 2325 receiver, serial number 10431 J4, manufactured March 4, 1976
    • Original Handbook of Instructions
    • Original schematic diagram for the 2325
    • Original warranty card
    • Original inner and outer factory boxes with clam-shell Styrofoam packing
    • Copy of 7-page color sales brochure
    • Copy of 2325 Service Manual
    • Restoration worksheet for the unit - all parts replaced, including suppliers and part numbers
    • Full 90-day parts & labor warranty*

    Features:

    • 125 watt per channel direct-coupled, all-discrete, high-current-capable amplifier circuitry
    • Independent power supplies for each channel
    • Gyro-touch tuning with signal strength/multipath and center-tuned meters
    • 300 and 75 ohm FM antenna inputs, FM muting switch, variable muting threshold (rear panel)
    • On-board Dolby™ noise reduction system
    • Signal strength/Dolby™ level/multipath meter, center-tuning meter
    • 2 tape loops, with dubbing from 2 to 1 and 1 to 2
    • Front panel dubbing jacks for Tape 2 (Tape 2 RCA jacks also in rear)
    • 2 magnetic phono inputs, 1 auxiliary input
    • Loudness switch; high (9 kHz) and low (15 Hz) filter switches
    • Independent Bass, Mid, and Treble controls for each channel
    • Stereo/Reverse/L+R/L/R Mode switch for complete front-panel speaker control
    • Main In and Pre Out jacks for using this unit as either a preamp or a power amp
    • Variable Bass Turnover (250Hz/500Hz) and Treble Turnover (2kHz/4kHz) switches
    • Two sets of speakers may be connected, both sets may be operated together or independently
    • Two rear panel accessory outlets (one switched, one unswitched) / Frequency Response:
      Continuous Average Power: 125 Watts /ch @ less than 0.1% THD into 8 ohms
      Power Band: 20Hz to 20,000 Hz
      Frequency Response (±0.5 dB): 10Hz to 100,000Hz
      Damping Factor (at 20 Hz): 70

      Tuner:
      FM Quieting (at 10 µV RF input): 70 dB
      Stereo Separation: 42 dB at 1000 Hz

      Total Harmonic Distortion (Stereo): 0.3%
      (Mono): 0.15%

      Dimensions (h\" x w\" x d\"): 5-3/4 x 19-5/16 x 15-3/16
      Weight (lbs.): 49.5 lbs.

      Additional 2325 specifications are available on Ben Blish\'s awesome [link removed by ] Web site.

      Terms:

      If you are not 100% satisfied with this unit, you may return it within 14 days of receipt for a full refund of your purchase price and original outbound shipping (yes, return shipping would be your responsibility). Full refund would of course be contingent upon receiving the returned unit in the same condition in which it was sent, without any missing or exchanged parts.

      *As most failure-prone parts in this receiver have already been replaced, I have no problem offering a full 90-day warranty on this unit. Should you have any problems within 90 days of receiving this item, I will repair it free of charge, including parts and labor, provided you handle round-trip shipping.

      Due to guidelines, I accept only PayPal payment. Buyer pays fixed FedEx Ground shipping rate of $70.00, which includes shipping insurance, for any destination in the continental US. The original two-box factory carton will be enclosed in a third box to protect the original packaging. Buyer MUST respond within 3 days of the sale end or transaction will be void. Payment MUST be received within 10 days of the end of the sale or the transaction will be void. I reserve the right to cancel offers from any party with a response rating at or below zero, or any party with excessive negative response. Good luck and happy offerding!


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