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Purveyors of Electronic, Musical and Vintage goods from then, now and in between. 
Since 1982.

STEREO PRE-AMPS, POWER AMPS,
 INTEGRATED AMPLIFIERS
USED, VINTAGE & CLASSICS

 

Stereo amps amplifiers & Pre-amps: Classic / pre-owned, Vintage stereo control / preamps, integrated amps & power amplifiers by Dynaco, Pioneer SA, SAE Mark, Sansui, Hafler, Kenwood KA, KC, KM Marantz PM, Onkyo, Technics, Sony, JVC, Harman Kardon HK.

 

   
 


PRE-AMPS:
 

    

NEW LISTING 4/25/16
(Click on above thumbnails to enlarge photos)

CheckMarkSmall_web.jpg (792 bytes) warranty
VINTAGE DYNACO PRE-AMP
DYNACO PAT-4
STEREO PRE-AMPLIFIER
#...5899
MADE IN THE USA!
Circa 1967-73

 
for sale
 
Our technician has completely gone through and 'Certified' this unit cleaning contacts, controls and pots. Replaced 'loose feeling' tape monitor switch with another original Dynaco pre-amp switch. Pots and switches are all super high quality. All functions tested perfectly. All original knobs intact and no bent control shafts.
 __________________________________
 
 
One of the classic, "old standby's" of the audio world. The Dynaco PAT-4 Pre-Amp. Brushed aluminum face with matching "milled" look knobs. This is also a VERY WELL DESIGNED & BUILT unit:
 
Dynaco Pat-4 features
:

- Separate L & R, Bass and Treble 
- Stereo-Mono switches to provide A or B channels independently or combined (A+B) with 6 dB blend for 3rd channel output
 - L / R Balance
- Tape Monitor input as well as Tape Head input for earlier tape decks (can also be used for Video / CD / DVD / VCR / DAT / MP3 / XM / SIRUS etc. as well as for CDR)
 - Phono input
- Tuner input (can also be used for Video / CD / DVD / VCR / DAT / MP3 / XM / SIRUS etc. as well as for CDR)
- High filter switch @ 15 KHz, 10 KHz, and 7 KHz
 - Low Filter selector
- SPARE (AUX) input for (CD / DVD /DAT / iPod / VCR / MP3 / XM / SIRUS etc. inputs)
- RCA outputs for feeding power amp
- 4 AC convenience outlets on rear panel (2 switched and 2 un-switched)

 
Dynaco Pat-4
Original Specs:
Frequency Response:
High level inputs - ±0.5 dB from 10 Hz to 100 KHz,
Low level inputs - ±1 dB from 20 Hz to 20 KHz
Distortion at rated 2 volt output:
THD less than 0.05% 20 Hz to 20 KHz IM less than 0.05% with any combination of test frequencies
Hum and Noise: Magnetic Phono: 70 dB below a 10 mV reference signal High level: 85 dB below a 0.5 volt signal Gain: Magnetic Phono: 54 dB at 1000 Hz High Level: 20 dB
Tone Control Range: ±16 dB at 50 Hz ±12 dB at 10 KHz
Maximum Output: 10 volts into high impedance; 5 volts into 600 Ω .
Impedances: Magnetic Phono: 47,000 Ω
Tape Head: 100,000 Ω
High level: 100,000 Ω
Audio Output: 600 Ω
To Tape: From low level inputs, 600 Ω . From high level inputs, same as source
Amplifier input: Nominal load 10,000 Ω or higher
Inputs: Low level or high level RIAA magnetic phono or ceramic phono NAB 7-1/2" tape head Special (normally microphone) Tape amplifier, Tuner, Spare high level, or TV, etc.
Front panel high level Outputs: Tape input ahead of controls;
2 Audio outputs (one switched by front panel jack)

 

 This was from Dynaco's first series of solid-state audio components. Again, we have completely gone through the unit. One note about Dynaco Pat-4 pre amps is that, like a few other 'vintage' units, is due to the close proximity of the input jacks, you will need to utilize fairly 'normal' jacketed RCA connectors, as there is not enough room to 'squeeze' some of the 'fatter' RCA jacks (usually seen on 'high end' 'interconnects'). All functions have been tested and pass with flying colors! Minor scratches on top sheet metal cover and the only other issue is that the face panel does not have 'On-Off' silk-screened on it. It may never have had it, or it may have worn off. Pre-amp looks decent and sounds great. Includes an 'e-copy' pdf download of the Dynaco PAT-4 owners / users / instruction manual.
 Unit measures 13.5" wide x 9" deep x 4.5" high and weighs ~4 lbs unpacked. Includes our standard 90 day limited warranty.
 Cond. 8.5
 $259. 
(C) R.R.
 

(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)
 

 

-

Pre-amps, Power amp & Integrated Amps Coming Soon
(or at least as time allows):

Hafler 9180
Hafler DH-101
Kenwood KA-5500
Kenwood KA-6000
Kenwood KA-7100
Kenwood KM-206
NHT SA-3
Onkyo A-7040
Onkyo A-8017
Pioneer SA-7800
SAE MKIIIA
SAE TWO A7
Sansui AU-717
Sony TA-F5A
Yamaha DSP-A1000
and more...
 


POWER AMPS:
 

  b&k_av2500_5-multi-channel_av_amplifier_web.jpg      b&k_av2500_5-multi-channel_av_amplifier_collage.jpg

          NEW LISTING 8/24/12
  (Click on above thumbnails to enlarge photos)
CheckMarkSmall_web.jpg (792 bytes) warranty
B&K MULTI-CHANNEL
AV2500
5-CHANNEL
AUDIO / VIDEO POWER AMPLIFIER
#...4826

Circa 19
95

  "WORLD AC POWER"
MADE IN USA

for sale
We have complete gone through this unit and bench checked / tested it. Amp has been cleaned inside and out. All input level pots cleaned for static free performance. Internals inspected, transformer secondary's tested and our technician has completely Certified this amp. All functions have been tested and pass with flying colors!
Amp designed using Huge 'Torroidal' Power Supply Transformer. Super quality all around. From the original OM, "
The high quality parts complement include state-of-the-art solid state devices, 1% metal film resistors, computer grade electrolytic power supply capacitors, and a high capacity toroidal transformer". All 5 inputs and all 5 outputs tested and both side produces clean and even sine waves! No power supply hum of any kind. It's dead silent! Following restoration procedures, we burned it in, in the shop at continuous high volume for 4 hours straight and it functioned flawlessly.
   

   On our test bench, each of this particular unit's (#...4826) FIVE (5) amplifiers produced 21.2 volts at 8 ohms per channel for 56 watts / channel and 17.7 volts at 4 ohms per channel for 78 watts / channel (4 Ohm operation not recommended) via discrete output transistors (5x LM3886T. (Idle AC current draw @ .38A. DC offset / out <2mV each channel.
   

   Great condition, late model, 5-Channel power amp by B&K. Model B&K AV2500. VERY versatile unit. 5-inputs and 5 outputs, Stereo and Mono Line outputs, bridge-able and more. Excellent for feeding multiple rooms / speaker systems or for use in an A/V system. Lots of punch and headroom.
   Features:
   

   - 5- Channel operation
   - 5 Discrete inputs and 5 Discrete outputs
   - 'Bridge-able' into ONE big power amp
   - Built-in Protection circuit
   - LED Status indicators
   - RCA input jacks
   - Oversize torroidal power supply transformer
- Heavy duty binding posts (can use 'single' bananas, but not standard banana pair spacing)
- Gold Plated Connectors - Improve connections for better sound and minimized signal loss and degradation.
- 1% Metal Film Resistors - Low noise resistors for better sound and a greater degree of repeatability.
- High Current - Ability to reproduce demanding recordings.
- Computer Grade Capacitors - Large capacity computer grade electrolytic capacitors for extended low frequency control and improved dynamics.
- Protection from accidental shorting of output
devices and protection from thermal overload.

   - Externally located 'mains' fuse
- 5-24VDC Control input voltage and 12VDC control voltage output (comes with 'shorting' cable to enable amp function without any corresponding control voltage in.)

-
True "
WORLD AC POWER"™ allows unit to be operated on 50 or 60 Hz AC and will select voltages from 110v, 120v, 220v and 240 volts AC input.

 

Also from the OM;  
"The most obvious function for the AV2500 series II is to take five separate
audio inputs and provide five separate amplified outputs. Your AV2500
series II has arrived set up in this configuration.

- With the inputs buffered, a line output (OUT BUS) may be taken from
either the L BUS, R BUS, or L+R BUS and sent on to another amplifier.
This allows for linking of multiple amplifiers.
- Continuing its versatility, the AV2500 series II may be used mono to
provide one, high current channel in order to drive a speaker requiring
more power.
- As a result of the AV2500 series II’s unique bus system, the input to
channels 4 and 5 may be inverted thereby allowing the possibility of
creating a single high voltage (bridged) channel from one source, through
the left bus."


Many more features, listed in the user manual, way too numerous to mention.

 Original B&K AV2500 Specifications
(2500II specs, but essentially the same amp):
 "60 Watts per channel minimum RMS, @ 8ohms, 1k, with no more than 0.09% THD"
   Design type: 5 Channels, Class-A/B operation
Input Sensitivity: 0.77V
Input impedance: 33.2k Ohms
THD; 0.09% @ 1kHz
   Power Bandwidth: 5Hz-45kHz
Slew Rate; 14V / mSec
Damping Factor; 80 / 8 ohms
Signal / Noise; 95dB A weighted
Dynamic Headroom; 1dB
Max Power Consumption; 450 Watts
 
    
 Again, as stated before, our technician has completely gone thru this B&K AV2500, multi-channel Power-Amp, cleaning and testing all and it gets our full 'Certification'. Overall amp in great cosmetic condition, with only minor wear to the top cover. Unit looks, works and sounds great! Includes a pdf 'e' copy of the owners / users manual. Unit measures 17" wide x 12" deep x 3.75" high and weighs 23 lbs unpacked. Includes our standard 90 day limited warranty.
B&K AV2500 MULTI-CHANNEL POWER AMPLIFIER
Cond. 8.5
$599.

 

(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)

  

 

    

NEW LISTING 4/25/16
(Click on above thumbnails to enlarge photos)

CheckMarkSmall_web.jpg (792 bytes) warranty
HAFLER STEREO POWER AMPLIFIER
HAFLER DH-200
#...1120
MADE IN THE USA!
Circa 1979-82

 for sale
 
Our technician has completely gone through and 'Certified' this unit cleaning contacts, controls and pots.
Amp has been cleaned inside and out. We replaced the power switch with an original we sourced. Bias and DC offset set correctly. All functions have been tested and pass with flying colors! Amp designed using Huge Power Supply Transformer and super quality (expensive) filter caps. Externally located, vertically  finned heat sink for very efficient and silent, passive cooling of output devices. This amplifier is in both great electronic and physical shape. Looks LIKE NEW and sounds fantastic! All inputs tested and both side produces clean and even sine waves! No power supply hum of any kind. It's dead silent! Following restoration procedures, we burned it in, in the shop at continuous high volume for 8 hours straight and it functioned flawlessly.
  
On our test bench, this unit's amplifiers produced 33 volts at 8 ohms per channel for 136 watts / channel and 29 volts at 4 ohms per channel for 210 watts / channel via TO-3, Mosfet, Metal Cased, discrete output transistors (4x 561049 / 7913 & 4x 571134 / 7917). (Idle AC current draw @ .81A.)
  
Great "general purpose" power amp for a variety of consumer and Pro-Audio applications. Super quiet operation and build quality. We run it's little brother in our main demo system and have for years. Love it!!! Great for full range stereo speakers, Studio Monitors, stage monitors, wedge monitors or running drivers in a Bi-Amp / Tri-Amp system.

HAFLER DH-200 FEATURES:
 

- Stable down to 2 Ohms!
- Two Channel Operation
- Vertically mounted, external heat sinks
- Stable to 2 Ohms! (wouldn't recommend constant 2 ohm load personally for very many amps)
- Relay protection against "turn-on / turn-off" transients
- Thermal protection with "Protect" indicator on front panel
- RCA input signal I/O's
- Speaker outputs via 3-Way binding / banana posts
- "REAL" TO-3, Metal cased output transistors

 
Unit looks NEW and works great. We have completely gone through the unit cleaning and testing all.
 
HAFLER DH-200 ORIGINAL SPECIFICATIONS / SPECS:
 

- Stable down to 2 Ohms!
Voltage Gain (dB): 32
Sensitivity (for 100 watts @ 8 ohms): 1.5 VRMS
IM Distortion: SMPTE-IM, Less than 0.005%, 20-20kHz & 1-100 watts / 8
Ω
THD: 0.0015% @ 1kHz, 0.005% @ 10kHz &  0.012% @ 20kHz
Frequency Response: 1Hz to 100Hz, +0/-3dB @ 1 watt @ 8
Ω
10Hz to 40kHz, +0/- .5dB @ 100 watts @ 8
Ω
S/N: >100dB @ 100 watts @ 8Ω un-weighted
Damping Factor: > 150 @ 1k / 8
Ω
Slew Rate: 30v / μsec @ 1k / 8Ω (60 v p-p)
Input Impedance: 22k ohms unbalanced
Indicators: PWR-ON; Red. & PROT; Yellow.
Connectors (each channel): Input: RCA. Output: "Touch proof" 3- way binding posts
Cooling: Convection
Amplifier Protection: Full thermal
 

Rated Output Power (per channel):
Continuous Average Output Power Both Channels Driven:
8 ohms, 20Hz - 20kHz, 0.02% THD: 100 watts (see above results for the wattage we actually tested it to)
 

 On our test bench, both amplifiers produce perfectly clean and symmetrical sine waves at both 8 & 4 ohm loads.
Includes an 'e-copy' pdf download of the Hafler DH-200 owners / users / instruction manual.  Measures 16" wide x 10.5 deep x 5.255" tall and weighs 26 lbs unpacked. Includes our standard 90 day limited warranty.
HAFLER DH-200
Cond. 9
$439.
(C) R.R.


(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)
 

Audio_Centron_RMA_1000_Stereo_Amp_web.jpg       Audio_Centron_RMA_1000_Stereo_Amp_collage.jpg

      NEW LISTING 11/27/07
(click on above thumbnails to enlarge photos)
CheckMarkSmall_web.jpg (792 bytes)  warranty

PRE-OWNED
AUDIO CENTRON / SLM
POWER AMPLIFIER
RMA-1000 RMA1000

PROFESSIONAL / STEREO
STABLE INTO 2 OHMS!
MADE IN THE USA!
Circa 1986-94

for sale

This is a REAL, 'old skooool' built, CLASS A/B power amp. NOT class d, class g, class t or whatever class marketers are calling them this week, to be the lightest and cheapest amp you can buy, that weighs a couple lbs, but a REAL amp. It's got SIXTEEN output transistors in it!

2 rack space, Audio Centron, RMA-1000 power amplifier. Great for small "All-in-One" speakers, stage monitors, wedge monitors or running horns or mids in a Bi-Amp / Tri-Amp system or for running Low end / subs in mono-mode.

Features:

- Stable down to 2 Ohms!
-
- Power rated as follows;
8 ohms = ~100 wpc
4 ohms = 150 wpc
2 ohms = 220 wpc

- 2-Rack spaces high with built-in rack ears and carry handles
- Cooling fan for those demanding "2 & hard 4 ohm conditions"
- Relay protection against "turn-on / turn-off" transients
- Dual, Front mounted, independent input attenuators
- Dual, LED Signal, Limit and Protect indicators
- Thermal protection with "Fault" LED indicators

- XLR and 1/4" phono input signal I/O's
- Speaker outputs via 3-Way binding / banana posts and 1/4", "all metal" phono jacks

- Stereo / Bridge-Mono selector
- "REAL" TO-3, Metal cased output transistors
- Rear mounted main AC fuse

- Grounded AC input cord


While this unit was originally rated at ~100 wpc @ 8Ω, on our test bench, both this unit's amplifiers produced
peak power of 30 volts per channel for 112 watts per channel @ 8 Ω via discrete output & 27.7 volts per channel for 192 watts per channel @ 4 Ω via eight discrete, Motorola, Metal cased, (TO-3) MJI5002 & MJI5001 outputs.

 Again, as stated before, our technician has completely refurb'd this Audio Centron RMA-1000, stereo Power-Amp, cleaning and testing all and it gets our full 'Certification'. Unit works great. Only minor issue is that the "Channel B" input attenuator has a blank spot in the first 40% that does not respond to cleaning. Not an issue once you have amp up to operating level. We have completely gone through the unit cleaning and testing all. Both relays just replaced with new as well.
SPECS:

- Stable down to 2 Ohms!
- Output Power ratings (stereo mode):

8 ohms = ~100 wpc
4 ohms = 150 wpc
2 ohms = 220 wpc

- Bridge / Mono mode operation ( 440 watts @ 4 ohms)


On our test bench, both amplifiers produce perfectly clean and symmetrical sine waves at both 8 & 4 ohm loads. We tested both internal amplifiers to the above specs, and found them accurate.
This is a great performing, fan cooled amp.

On a personal note; I've actually been using this amp in my studio as a rehearsal amp, but can't really have any 'fan cooled' amps in that environment, so am going to have to go a different route.
Measures 19" wide x 16.5 overall depth / 13.5" rack depth x 3.5" tall and weighs 35 lbs unpacked. Includes our standard 90 day limited  warranty.
AUDIO CENTRON RMA-1000
Condition 8
$299.

 

(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)

 

 

  


Did you know?
THD (Total Harmonic Distortion) – THD is a measure of the how much a given audio device may distort a signal through the inevitable introduction of added harmonics or overtones. These figures are usually given as percentages. THD figures below approximately 1% are inaudible to most people (although market promotion efficiencies have 'brain-washed' much of the 'audio-public' into weighting low THD with almost 'holy grail' importance. I remember some manufacturers touting numbers as low as <0.003% in the early Eighties).  Low THD is not always an indication of a high quality amplifier. In fact, it is / was more commonly just the opposite. Some of the 'highest end' (read REALLY expensive) and certainly best sounding units will have distortions somewhere between .1% & 1%.
Low THD is only a simple 'bi-product' of 2 aspects. The first was an inordinate and increasing amount of 'global / negative feedback' built into amplifiers primarily to suppress distortion. This practice started to occur in the late 1970's and certainly was in 'full force' past the early 1980's for most 'main stream' consumer-grade audio amplifiers. Unfortunately this also 'suppressed' tone and 'punch' (musicality) but it made the numbers look good to the 'spoon fed' consumer (kind of like overly high speaker wattage numbers, and sorry if you're in that group and, most folks were so you're not alone). Secondly manufacturers were moving away from 'discrete-transistor' output designs to more 'monolithic' 'power-pack' output designs. While these designs reduced power supply requirements, thus reducing parts costs and weight (also translates to lower prices due to savings on freight from Asia) they generally sounded anywhere from somewhat 'anemic' compared with the designs from a few years previous, to completely 'gutless' and 'un-musical'. But, hey,… they had very low distortion figures….Can anyone say 'threw the baby out with the bath water'?
Excerpts of the above text from one of the best Car Audio sites and stores in the world, 'Car-Fi' www.car-fi.com .
 

 

 


 


INTEGRATED AMPS:
 

   

 


 

 

 


SOLD ITEMS BELOW


 

 


TO SEE OUR ARCHIVE OF SOLD AMPS & PREAMPS CLICK HERE
 

Dynaco_Stereo-120_Power_Amplifier_Web.jpg       Dynaco_Stereo-120_Power_Amplifier_Collage.jpg

       NEW LISTING 3/31/14
(Click on above thumbnails to enlarge photos)
CheckMarkSmall_web.jpg (792 bytes)  warranty
VINTAGE
DYNACO STEREO POWER AMPLIFIER
DYNACO "STEREO 120" POWER AMP
Circa 1969-78
MADE IN U.S.A.

SOLD 10/16/15
SHIPPED TO NEW MEXICO

Our technician has completely gone through and 'Certified' this unit. Output transistor removed and tested independently. Unit bench checked / tested. All functions have been tested and pass with flying colors! Both inputs tested and both side produces clean and even sine waves! No power supply hum of any kind. It's dead silent!
This is one of the most 'famous' power amplifiers ever designed and sold. Originally co-designed by David Hafler (always been a favorite amp engineer of mine), they have been the 'heart' of many audio systems since the late '60's.

   

On our test bench, this particular Dynaco Stereo-120's amplifiers produced 21.8 volts at 8 ohms per channel for 59 watts / channel and 18 volts at 4 ohms per channel for 81 watts / channel via discrete, metal cased, TO-3'output transistors. (Idle AC current draw @ 0.46A.
DC less <3mVDC / Ch.
Floor noise measured at L& R = 2.3mVAC

   

Dynaco amps have always been known for understated appearance and performance. While they were never much on looks or 'whistles and bells', they made up for that in performance. Excellent for 2-channel (stereo) audio listening or for use in an A/V system or for driving project studio monitors.
   

- 2-Channel stereo, Class A/B operation
- Standard RCA input jacks
- Oversize power supply transformer and capacitors
- 3-Way, Binding post speaker jacks
- AC / MAINS protection fuse

   

DYNACO STEREO-120 Original Specs:

Design type: 2 Channels, AB operation
 Damping Factor @ 20kHz-20kHz / 8Ω: >40
Signal / Noise: >100dB @ 60 watts
Input Sensitivity: 1.5V for 60 watts output
Input Impedance: 100k Ohms
Channel Separation: >70dB @ 20Hz-20kHz
  Rated RMS Output Stereo: 60 watts per channel, min. RMS, @ 8
Ω
IMD; <0.5% @ rated power /
Freq response: 5Hz-100kHz @ 8Ω
Wall AC current needed:
400 Watts
 
Again, our senior tech has completely gone thru this Dynaco Stereo-120 and it gets our full 'Certification'.  With the exception of a some minor blemishes to the chrome (inevitable on these amps), the unit looks decent (see above photos). Unit looks, works and sounds great! Again, while not much on cosmetics or 'button features / whistles or bells' Dynaco amps are known for incredible punch, headroom, and musicality. Includes an 'e-copy' pdf download of the Dynaco Stereo 120 owners / users / instruction / assembly / service manual (which is actually an 'amazing read' and should probably be read by anyone using / owning ANY amplifier from ANY brand and ANY model! Just FYI).
Unit
measures 10.5" wide x 13" deep x 4" high and weighs 20 lbs unpacked. Includes our standard 90 day limited warranty.
DYNACO STEREO 120, 2-CHANNEL STEREO POWER AMP
Cond. 8

(C) R.R.
SOLD 10/16/15
SHIPPED TO NEW MEXICO


(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)

 

 

 

Onkyo_M-506RS_Stereo_Power_Amplifier-Amp_web.jpg       Onkyo_M-506RS_Stereo_Power_Amplifier-Amp_collage.jpg

Onkyo_M-506RS_Stereo_Power_Amplifier-Amp_Power-supply_collage.jpg  

NEW LISTING 3/26/14
(Click on above thumbnails to enlarge photos)
CheckMarkSmall_web.jpg (792 bytes)  warranty
PRE-OWNED
ONKYO M-506RS POWER AMPLIFIER
ONKYO STEREO POWER AMP

'Military / Euro-Asia' Market Unit 
 
Circa 1980-85
"WORLD AC POWER" ™
MIJ

SOLD
6/2/15
SHIPPED
TO HOUSTON
Our technician has completely gone through and 'Certified' this unit. Unit bench checked, necessary repairs made, cleaning / detailing inside and out, fully tested and Certified. Our technician reset the voltage to correct 120vAC. New bulbs / lamps installed for 'Power', 'Servo', and 'Speaker Selectors'.
Performs and sounds fantastic! All inputs tested and both side produces clean and even sine waves! No power supply hum of any kind. It's dead silent! Following restoration procedures, we burned it in, in the shop for 48 hours and it functioned flawlessly (we actually took it into our 'demo' system and 'rocked-it' HARD on our Altec VOTT's. HUGE sound and thump).
From the original Onkyo M-506RS manual,

"...Large, independent left and right power supplies, with large capacity, chemical capacitors have been provided to enable extremely low power supply impedance. Super Servo on both the hot and ground signal sides reduce variations in the power supply for larger inputs to under 1/100th (-40dB), creating a nearly perfect power supply".
(See photos above of power supply)
And as we all (should) know an amp is only as good as it's power supply!
Also from the manual,
"The output stage uses high fT transistors in a 3-stage Darlington configuration. Distortion usually associated with 'Class-B' amplifiers is virtually eliminated, and Onkyo's unique Linear Switching radically reduces both switching and crossover distortions. In addition, an auto-tracking bias system is used to prevent instabilities in the bias current due to thermal variations".

On our test bench, this particular Onkyo M-506RS power amplifier, #...1883, unit's amplifiers produced 36.6 volts at 8 Ohms per channel for 167 continuous watts, and 32.3 volts @ 4 Ohms for 260 watts / channel via 8 (eight) discrete, output transistors. (4X 2SA1301 & 4X 2SC3281). (Idle AC current draw @ .6A. & DC offset out = <2.75mV on either side. Floor noise measured at 0.03mVAC either side)

This is a Huge and Beautiful looking, performing and sounding power amplifier. High gloss, rosewood side panels frame a 'unit wide' smoked glass face in front of HUGE VU power meters. Very Elegant! Only cosmetic issue is a scuffed area in the clear coat on the front edge of one of the side panels (see photos above). Could probably be 'rubbed out' by someone capable, but that's 'beyond our pay grade'. As this was a unit intended for the Euro-Asia and Military market, it was not available to the 'North American' market, so about the only way one of these units would end up here is if a GI brought it back from tour. We actually get a large proportion of GI gear here at Oak Tree Vintage.

Onkyo M-506RS
Features:

- DUAL power supplies (has a lot to do with how much this amp 'punches'. That, and the EIGHT output transistors.) (See photos above of power supply)

- 'Super Servo' when using compatible 'Super Servo' pre-amp (we didn't use it to audition)
- 'Low Speaker Impedance' protection
- DC protection for 'Turn-On Surge' and 'Output'

-
A and / or B speaker selector
- Front mounted 'Gain / Level' controls
- Huge, Beautiful, Lit VU Power Output meters

-
Meter Range selector for either normal or 'x 0.1'
- 1/4" Stereo headphone jack

- Signal inputs via standard RCA jacks
- Heavy duty binding post speaker outputs
- Power On, 'Super Servo' engaged, and 'Speaker Selected' indicators

- True "WORLD AC POWER"™ allows unit to be operated on 50 or 60 Hz AC and will select voltages from 110v, 120v, 220v and 240 volts AC input.

Onkyo M-506RS Specifications:

- Rated RMS Output: 150 watts per channel, min. RMS, @ 8Ω, both channels driven, from 20Hz to 20kHz.
- Frequency Response:
1Hz to 100kHz
@ 8Ω, both channels driven
- Signal to Noise Ratio: 122dB (20Hz to 20kHz) at full RMS output
- Total Harmonic Distortion (THD): <0.002% @ rated output
IMD; 0.0015% @ rated power /
- Damping Factor: 180 @ 8 Ohms / 1Khz
- Load Impedance: Rated for 16, 8, 4 ohm use
- Input Impedance: 47K Ω nominal
- Input Sensitivity: 1V for rated power into 8Ω
- Output Connector: Heavy duty, 3-way binding posts
- Input Connector: 24k Gold Plated RCA jacks
- Output Monitor: Heavy Duty Banana / Binding posts

Again, as stated before, we have completely gone through this Onkyo M-506rs, Power Amplifier cleaning and testing all and it gets our full 'Certification'. This is an amazing performing and sounding amp. We have 'stood on it' hard, with a number of our speaker loads (the most fun being when connected to our Altec 'Voice of the Theaters'. It's a huge sounding and punchy amp, with lots of 'head room'. Handles 'REAL' high power levels perfectly well. If you are looking for serious, vintage power, it ain't gonna get much better than this.
 Comes with an e-copy, pdf download, of the Onkyo M-506RS Owners Manual and Service Manual.
 Measures standard 18 7/8" wide x 16 5/8" depth x 6 7/8" tall and weighs 43 lbs unpacked. Includes our standard 90 day limited warranty.
ONKYO M-506RS POWER AMPLIFIER
 Cond. 8.5 (only due to scuff on side panel edge)

$689.
(C) M.R.

SOLD
6/2/15
SHIPPED
TO HOUSTON

(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)


 

 

Kenwood_KM-208_Power-amplifier_web.jpg       Kenwood_KM-208_Power-amplifier_collage.jpg

       NEW LISTING 3/31/14
(Click on above thumbnails to enlarge photos)
CheckMarkSmall_web.jpg (792 bytes)  warranty
PRE-OWNED
KENWOOD POWER AMPLIFIER
KENWOOD KM-208 KM208 AMP
#...1236
Circa 1985-86
MIJ

SOLD 3/6/15
SHIPPED TO TEXAS

Our technician has completely gone through and 'Certified' this unit.
Unit bench checked / tested. Amp has been cleaned inside and out. Face removed, meter illumination lens removed, cleaned and reattached. All new panel illumination lamps replaced with new. All functions have been tested and pass with flying colors!
Amp designed using Huge Power Supply Transformer and oversized, vertical finned heat sink for very efficient and silent, passive cooling of output devices. All inputs tested and both side produces clean and even sine waves! No power supply hum of any kind. It's dead silent! Following restoration procedures, we burned it in, in the shop at continuous volume for 72 hours straight and it functioned flawlessly.
   

While this amp is originally rated at 150 watts with both channels driven, on our test bench, this particular unit's (#...1236) amplifiers produced 38.5 volts at 8 ohms per channel for 185 watts / channel and 30 volts at 4 ohms per channel for 225 watts / channel via discrete output transistors (2x 2SA1216 & 2x 2SC2922. (Idle AC current draw @ .3A.
DC offset out L= 5.5mV & R= 6.4mV.
Floor noise measured at L= 00.0mVAC and R=00.1mVAC

   

Great, later model power amp by Kenwood. Model KM-208. HUGE power output! Excellent for 2-channel (stereo) audio listening or for use in an A/V system. Lots of punch and headroom.
Kenwood KM-208 Features:
   

   - 2- Channel stereo operation
   - A or B speaker selector via high current relay
   - Dual, Vertical, 7-Segment LED Power Output Meters with Dual Position Level Selector
   - Built-in Protection circuit
   - LED Status indicators
   - Front-mounted 1/4" stereo headphone jack
   - RCA input jacks
   - Dual, vertical finned internal heat sink
   - Oversize power supply transformer
   - 3 Rear-mounted AC convenience outlets (2 switched and 1 un-switched for a total capacity of 200 watts)

   
Kenwood KM-208 Original Specs:
 "150 Watts per channel minimum RMS, both channels driven @ 8ohms, 20-20k, with no more than 0.015% THD"
   Design type: 2 Channels, AB operation
 Damping Factor @ 1kHz / 8Ω: 35
  Rated RMS Output: 150 watts per channel, min. RMS, @ 8
Ω, both channels driven, from 20Hz to 20kHz.
Music Power 314 watts per channel
THD; 0.015% @ half rated power / 8Ω w/ 20-20kHz
0.001% @ half rated power / 8Ω w/ 1kHz
IMD; 0.002% @ rated power /
   Power Bandwidth: 10Hz-50kHz @ 0.03% THD @ 8Ω
   Potential Frequency Response: 5Hz-200kHz
Damping Factor; >35 @50Hz / 8 ohms
Signal / Noise; 120dB A weighted
 
    
 Again, as stated before, our technician has completely refurb'd this Kenwood KM-208, stereo Power-Amp, cleaning and testing all and it gets our full 'Certification'. Great 'all around' power amp for about any audio system. We have sold MANY of this series of Kenwood power amps, with never a complaint. Includes an 'e-copy' pdf download of the Kenwood KM-208 owners / users / instruction manual. Unit looks, works and sounds great! Unit measures 16.5" wide x 10.5" deep x 4.75" high and weighs 20 lbs unpacked. Includes our standard 90 day limited warranty.
KENWOOD KM-208
Cond.
8.5

(C) K.K.

SOLD 3/6/15
SHIPPED TO TEXAS

(Above text, in it's entirety, property of www.oaktreevintage.com / Oak Tree Enterprises, LLC. See 'Copyright Information' page for details)

 

 

 

 

 

 

 


**
"(actual as measured)" refers to original test results done by Hirsch-Houck Laboratories upon test release of product when new. Current "aged" specifications / performance may of course vary from that.

 


 


 

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