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.

Friday, November 18, 2016

Marantz Model 1 Audio Consolette & Type 4 Modification

Marantz "Audio Consolette" also known as Model 1 is the one in list of collective items.

It is a beautiful mono preamplifier, so need "2" for using in stereo system.

It's adjustable for turnover and roll-off in record equalizer that Marantz 7C removed.

One of my friend has 4 pairs of Marantz Model 1, so he need to try 1 pair in "Real Sound"

like Marantz 7C that I've modified for him before.

3 of 12AX7/ECC83 for 1 preamplifier (mono).

It need external power supply like Marantz Type 4 that I mention in the end of this post.

Top view for both channels of original with many Bumblebee "an easier to leak" capacitors.

Bottom view of originals.

Rectifier section with carbon composition resistors that cause noise into system.

Components for modify both channels.

Arizona "Blue Cactus" capacitors, wet tantalum capacitors and high quality wirewound resistors.

Top view after modified.

All coupling capacitors using Arizona C50309 "Blue cactus".

Bottom view after modified.

Use wet tantalum capacitors for 12AX7 cathode bypass.

High quality resistors in rectifier section and add filter capacitor to final stage.

Change 47k cartridge loading resistor from 0.5W to 2W for more mellow tone.

And this is Marantz Type 4, external power supply unit for Model 1.

1 box supply to 1 channel Model 1. 

Use selenium rectifiers like all equipment in same era.

Selenium produces good tone but shorter life and cause toxic when it has failure. 

Modified by using STTH6112V2, great ultrafast & soft recovery diode for high voltage.

and good quality silicon bridge diode for filament voltage.

Parallel HV output with PIO capacitor, seem like bi-cap with first filter capacitor inside Model 1.

Better, can easily listen both Model 1 and Type 4 after modified.

Everything will be more better after run in for hundred hours.

Cheers !!!

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.


Thursday, September 22, 2016

Renovated EL156 Single Ended Amplifier

Telefunken EL156 seem like a king of pentode tube that many people want to taste.

My friend also bought a pair of mono-block EL156 single ended amplifiers

with all Tango transformers from ebay.

But he need new enclosure, tube rectifier and use Western Electric components.

So these are what we did with those requirements.

Original enclosure of EL156 mono-block with EF80 driver.

Wiring inside / diodes bridge rectifier.

Hirata-Tango FW-50-5S output transformer.

Hirata-Tango NN-6 "Permalloy core" input transformer.

Hirata-Tango MS-360 power transformer.

Schematic of renovated EL156 amplifier.

All main components mounted.

Bottom view, wiring with Western Electric cloth wires.

Top view / Mirror.

WE418A as a driver and WE 288A coupling capacitor with WE KS9929 interstage transformer.

#83 mercury vapor full-wave rectifier tube. 

Will update later with pictures when using in owner system.

Cheers !!!