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.

Monday, July 25, 2016

Harman Kardon Citation I with "Real Sound" Concept

Harman Kardon Citation I pre-amplifier was a one of top quality in it's era.

Great phono-stage with "Turnover" and "Roll-off", very usable features.

4 tube's stages passive equalizer per channel in phono-stage

with high quality capacitors in equalizer too.

And the most surprise for me is a filter choke in power supply !!!

Many of famous tube pre-amplifiers in that time like Marantz 7c, McIntosh C22 or Fisher 400CX

did not use any of filter choke, only resistors in rectifier section.

Very usable features in phono-stage.

Backside with different design.

Top view for inside.

This is only 1 channel with 9 of 0.1uF Sprague Bumblebee capacitors

and 3 of green 0.47uF/10V ceramic disc capacitors in signal path.

Many of capacitors in equalizer section.

Bottom view for another channel and power supply.

Filter choke on left side of photo.

"Bass" and "Treble" components in selectors for each channels. 

Rectifier section.

Loading resistors for "Phono 1" & "Phono 2" inputs.

Time to modify with "Real Sound" concept.

18 of 0.1uF Arizona "Blue Cactus" Capacitors and use 0.5uF PIO capacitors from WE

for replace 0.47uF ceramic type.

Top view after finish modified.

Bottom view for channel A.

Replace rectifier components with Ohmite "Brown Devil" resistors, Ultra Fast Recovery diodes

from ON semiconductor and decoupling capacitors for each high volt points 

with Obbligato film capacitors.

Replace "Phono 1" loading resistor with 2W Allen Bradley resistors.

After "Run in" time for 20 hours, more transparent and good sound quality from bottom to top range.

In my opinion, it's a high quality pre-amplifier with a half or quarter price of more famous brands.

Worth a try and you will find a new sound.


Tuesday, July 12, 2016

New Version of WE421A & Another WE Tubes Amplifier

If you have seen my previous WE421A tube amplifier that I've post in November 2015.

Sound from that amplifier impress me and my friends very much.

So I plan to build the new one with all WE tubes again but using higher level P&C transformer.

Schematic seem like the previous one but I use WE352A for driver stage

with Ampex input transformer and use P171A output transformer from P&C Electronics

that almost using in WE91 clone amplifier.

Custom power transformer from J&K work with original WE149E filter choke.

Schematic for this amplifier.

4 watts single ended power amplifier.

Our logo.

5 WE tubes in front row.

WE352A, very good sound WE triode tube.

Back side.


Aerovox 4uF Oil Capacitor.

Original WE149E filter choke with repaint.

Inside amplifier, using cloth wire for all connections.

Parallel electrolytic capacitors with PIO and film capacitors.

Using Ohmite "Brown Devil" resistor if need high power.

Arizona capacitor "Blue Cactus" as a coupling capacitor.

Try to make all short paths if possible.

Please let me know if you need more information.

Cheers !!!