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Welcome to Decware


Zen 25th Anniversary Edition



Model CSP325

25th Anniversary Classic Stereo Preamplifier


By popular request, we have created an anniversary edition of our well loved CSP3 preamplifier to match our 25th Anniversary Zen Triode amplifier (model SE84UFO25). We call this anniversary edition the model CSP325 and designed it to both match visually but also sonically. Like the 25th Anniversary Zen Triode amplifier the CSP325 maintains a purist and minimalist approach which is why it has a pair of input jacks located less than one inch away from the input tube. 


  • 6N1P-EV dual triode per channel driven by a 6N5P-EV dual triode

  • Compatible with 6922 as an alternate for either of the above.

  • Fully adjustable output level for each channel 0 - 20V into 100kOhms.

  • Each channel featuring it's own tube power supply regulation.

  • Dual volume controls.

  • 5u4G vacuum tube rectification.

  • Class - A single-ended triode operation with Direct Coupled gain stages.

  • Zero negative feedback.

  • Inputs for up to three line level sources.

  • Point-to-point hand wired.

  • Film Caps in both the signal path and power supply.

  • Removable magic eye tubes for VU meters to display the input signal.

  • 1/8" powder coated chassis and high mass hardwood base.

  • Lifetime warranty.

To create this anniversary edition many changes were made.  The functional ones are as follows: 


  • The headphone section and input level controls have been deleted.

  • Front input jacks were added with source selection for three sources and a mute.

  • Dual volume controls.

  • Removable VU meters for each channel using magic eye tubes.

This preamp adds body, density, weight and tone without harming the transparency of the SE84UFO25 amplifier.   


These VU meters are designed to help you optimise the input signal with sources that have variable output levels.  The perfect signal will have the most dynamic display on the magic eye tube.  If the signal is too strong the display will be on all the time, too weak it will be nearly off all the time.  


These magic eye tubes use a simple passive circuit and miniature vacuum tubes that have wire leads and are directly soldered into the circuit.  Average life of these tiny triodes is 10,000 hours.  We could have used a solid state transistor to drive the magic eye tubes but what fun would that have been?



This model is so pimped out that there are virtually no options other than deciding what mains voltage you want it wired for and what knobs you want on it.


Ebony, Gold, Black chicken head, Cream chicken head, rosewood.


The CSP325 is designed around the very popular  6922 dual triode.   There are a total of 3 of these audio tubes. We ship the unit with Russian 6N1P-EV and 6N5P when available.  We use the 6N5P for the input tube in the front.  You can also use 7DJ8 in any of these positions. The input tube in the front is what makes the biggest change to the sound. 


Rectification is done with a single 5U4G .  The internal voltage regulation tubes  do not need to be changed.  The internal driver tubes that turn the magic eye tubes into VU meters also do not need to be changed.

The magic eye tubes, 6B2, typically last a long time, in some cases the life of t he preamp.  These can be removed for night time listening if you don't want to see them.


Weight - 17 lbs. ea.

Dimensions - 9.0" H x 7.125" W x 14.0" D

Circuit type - Single-ended Class-A Triode SRPP

Power output - 0 ~ 30 volts 

Gain - adjustable up to 20dB

Input voltage - max 10 volts

Noise / Hum -79 db U / -58 db U@120HZ

Response - 20Hz ~ 20 kHz @ full output

Feedback - ZERO 

Rectification - 5U4G or 5AR4 or TYPE80 with adapter

Output tubes - 6NIP-EV 

Signal tube - 6N5P-EV 

VU tube - 6E2

Internal tubes - 5G5B-V, 6S6B-V

Biasing cathode biased

Resistors Precision WW & MF by DALE, VISHAY, RHODERSTEIN

Signal Caps - Foil 

AC cord - Removable power cord

Consumption - 65 watts 

Input jacks - RCA type Gold / Teflon

Output jacks - RCA type Gold / Teflon

Warranty - Lifetime to original owner


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Manual is in a .pdf format


Since we don't have dealer's and we sell our amplifiers directly to the customer, our customers have a direct line to us.  As a result, Decware support is legendary for over 25 years.

Support is not only a phone call or email away at any time, but when you purchase this amplifier you join a huge family of customers who also own one and enjoy supporting each other on the:



25th Anniversary Edition LINE LEVEL PREAMP 

Made by hand in the USA and sold wholesale to the public with a 
L i f e t i m e   W a r r a n t y  !

These are hand-built to order.  There are presently lots of orders on our real time build sheet.   A 10% deposit secures your place on the list with today's date and time stamp.  Balance is due when it's ready to ship. You will be sent a final invoice with the total price including actual shipping costs by our office during your wait.   


Model CSP325

25th Anniversary Classic Stereo Preamplifier

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