Nattawut Uamkruea, blogger and audio gear maker who passionate in vacuum tube, audio & music.
Producing electronics projects since high school. Seriously upgrade and modify vintage audio equipment for “Real Sound” concept.
He is a co-founder of Soundaries and Sentimental Studio, all audio solution provider.
Experienced and lively explore the listening rooms & audio shops in Japan as his most favorite to do.

Wednesday, October 5, 2016

Harman Kardon Citation IV Modification

After finish modified Harman Kardon Citation I.

I've read Jeff Day's blog about Harman Kardon Citation IV that he mention about

phono preamplifier section is very good like in Citation I.

One day, my friend asked me about Citation IV that he kept in his storage room

and want to upgrade it like Citation I that I've modified before.

Same front cover layout like Citation I.

Use 6 of 12AX7 tubes, 1 and half tube for phono stage in each channel.

Bottom side (Channel B) before modified.

Almost coupling capacitor use Good-All paper capacitors.

Some capacitors has changed by repairing shop before.

Using Selenium rectifiers both high voltage and filament voltage like others in their era.

Wirewound and high power carbon resistor in rectifier section.

Top view (channel A) before modified.

0.5W carbon resistors for loading cartridge in front of phono will replace with 2W rating later.

Almost parts for modification.

Channel A after modification.

All coupling capacitors replaced with Arizona capacitor "Blue Cactus" except last capacitor

using Western Electric film 2.097uF.

Channel B after modification.

Diodes still using Ultrafast soft recovery for high voltage and Silicon type for filament.

IRC GS-3 Metal glaze resistor for stable high voltage too.

And finally use Western Electric film capacitors for decoupling all high voltages.

First impression sounding just more relax than Citation I and also transparent.

You will find IV in cheaper price than I, but quality still in same range.



  1. Wow. This must be the first time ever a Citation preamp has been upgraded with Arizona caps.
    I was surprised to see Good-All caps inside though. These were used almost exclusively by Marantz and in their power amps. The Good-Alls are actually Mylar and last a long time. Again superb restoration. Keep up the great work!

  2. Citation I & IV are great preamps in reasonable price. Should be collect before price increase ;)

  3. You write more relax, you mean sweeter, softer? Can you detail your opinion?