Bogen

 


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Bogen DB230A stereo Amplifier (6DW5 output tubes)

This is at tube type stereo amplifier.  It has speaker impedance options that are indicative (to me) of Bogen's extensive experience in the multi speaker PA system architecture.  They took that experience and applied it to the output section of this stereo amplifier.  Evidence of this experience can be witnessed on the back panel speaker impedance selectors.  

This amp included two phono inputs. One pair for ceramic cartridges and a pair Magnetic cartridges.    There are a variety of mode including Stereo, Mono (Channel 1 input only) and Reverse. 

There is an 10db contour, 100 hz low and 4 kHz high filter switches.  A and B speaker switch, a speaker phasing switch and a Stereo/mono slide switch.  Please see documentation and schematics listed in Resources below for accurate descriptions. 

A selector knob chooses the equalization for phono records.  Those selections include RIAA, 78, and OLD.  You can choose the proper recording EQ to realize the sound intended by the recordings producers, conductors and/or recording engineers.  

I ran tests on this amplifier.  It works and sounds excellent.

I connected a BSR belt drive turntable with a magnetic cartridge and played a Beethoven HiFi (not stereo) LP cut from 35mm recording tape with the preamp set on RIAA.  Let me tell you, it sounded sweet!   Steve Miller's "Fly Like an Eagle" LP album also sounded nice too.   If Skyview does not sell this amp I will pick it up and install it as my Shop/shack stereo.  The smooth sound of this amp brings back memories of my youth!  The Beethoven LPs and Ravel's Bolero 10 inch record that my mom played along with my Rock and Disco albums of my 70's youth.  I can restore and connect a 78 rpm turntable with a ceramic cartridge and play the stack of old Lacquer 78's that I have squirreled away. 

 

This is what I did before I played this amp (not in order):

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Check all electrolytic capacitors for ESR and capacitance. 

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Measure all resistors in circuit.  

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Tested all tubes.   One output tube 6DW5 is bad and needs replaced.  Replaced bad 6DW5 output tube.  All remaining tubes test good on a B&K 700 mutual dynamic tube tester.

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Most components are original and UN-restored.  I replaced several bad electrolytic capacitors including; four 6DW4 grid coupling caps, two 6DW4 DC bias output stage caps.   

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Set output tube bias, 

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Cleaned cabinet and chassis, 

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Cleaned all switches and potentiometers.  

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Checked all voltages. 

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Measured output power on both channels (see below pictures).  

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Checked all inputs for function. 

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"Burned-in" for several hours.

Once fully restored this unit should make a great solid foundation for anybody's Vintage Tube Stereo system or classic home recording studio monitor amp.  Know what your DAW mix sounds like on a vintage tube amp before you publish!  

Take a sonic ride back to the past..............

 
IMG_3717.jpg (668965 bytes)Separate treble and bass controls for left and right stereo channels. IMG_3718.jpg (558564 bytes)

Factory metal covers included.

IMG_3719.jpg (736187 bytes)

Several convenience outlets.  Two are switched. 

IMG_3720.jpg (698300 bytes)

Model and serial number.

IMG_3721.jpg (942179 bytes)
IMG_3722.jpg (1000178 bytes)

Flexible speaker impedance options. 

IMG_3723.jpg (729757 bytes)

Ceramic and magnetic phono inputs.  Tape head input. 

  IMG_3714.jpg (670897 bytes)

Bias set. 

IMG_3707.jpg (881829 bytes)Phono input pre-amp stage tube ECC83/12AX7.
IMG_3709.jpg (838435 bytes)

The often coveted "Telefunkin ECC83" test strong.

IMG_3716.jpg (974194 bytes)

Original.

IMG_5285.jpg (2961796 bytes) 

You can see the replaced capacitors. 

IMG_5286.jpg (129256 bytes)

This is a DC filter cap on the plate of the ECC83 input pre-amp tube.   It is not shown on the Sam's.

IMG_3705.jpg (928717 bytes)

Ahh.  Tube glow.

IMG_3706.jpg (341867 bytes)        

 

Testing the output.

IMG_5340.JPG (295874 bytes)

10volts/div, 10x probe.

IMG_5336.JPG (298659 bytes)

Chan 1  4.8 div

IMG_5337.JPG (306091 bytes)

Distortion

4.8v/div x 10v/div x 1vRMS/2.828v pp = 

16.97v RMS

[(17vRMS)^2]/8ohm = 

36 watts RMS chan 1 Undistorted.

Load - 8 ohm compact ported book-shelf speaker (and good ear plugs). IMG_5338.JPG (292273 bytes)

Chan 2  4.4 div

IMG_5339.JPG (273121 bytes)

Distortion.

(4.4vpp)(10v/div)=44vpp

44vpp/2.828vrms=15.55vrms

(16^2)/8ohms = 

32 watts RMS chan 2 Undistorted.

 

IMG_5341.JPG (429919 bytes)

1000 Hz sine.

 

Resources:

radiomuseum.org

Sam's Photofact here.

Schematic found here.

Vintage Asylum

Bogen DB-230

Bogen Logo

New and some legacy units.

There are several good discussions about this amp on: Audiokarma.org.  

 

A final note.  This amplifier was donated to Skyview Radio Society by the estate of an SK.  When this amp is sold all the proceeds will benefit Skyview Radio Society radio club (a 501c3 corp).  We are thankful for the generous donations from local SK families to the Skyview Radio Society.   

I will not be listing this unit.  Please contact Skyview directly for details.  I only prepared and documented this unit for sale.  

There are no guarantees, warrantees or any other promises of functionality.  This unit is intended for sale, As is, Where is, unless stated otherwise by the owner/seller.  This is used vintage equipment.

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