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.

Sunday, January 17, 2016

Marantz Model 7 After Modify with "Real Sound" Recommendation

I'm excited to get great result after using Arizona capacitor and other high quality components

that Mr Shirokazu Yazaki from SPEC Corp. have produced and recommended for "Real Sound".

After finishing modify McIntosh 275 amplifier with capacitors adventure.

I started continue modifying Marantz Model 7 to use them together.

This is a link for inside Model 7 before do anything.

The result can be predictable for upgrade sound quality of Marantz Model 7 to higher level.

And I want to share what did I do with this world famous tube preamplifier.

Components for do this "upgrade".

Top view.

Bottom view.

Rectifier section, both high voltage and filament supply.

Original electrolytic capacitors are in working condition and still produce great tone.

I use my favorite IRC GS3 metal glaze resistor to replace carbon composite type 

that too high tolerance for this section.

Change old selenium to silicon bridge rectifier for tube's filament supply.

Using STTH6110TV2 ultrafast recovery diode to replace selenium in high voltage rectify too.

Replace cement coated type with better wirewound resistors from Ohmite.

Use 680k carbon composite resistor to replace 500k potentiometer + 180k resistor

in level adjust before last tube stage.

This potentiometer almost had dirty contact, need to replace if somebody still want to use it.

47k resistor RA series from Tepro did it best in cartridge loading position before phonostage.

And all coupling using paper & polyester dielectric in oil-filled capacitors from Arizona capacitor.

Almost use C50309 "Blue Cactus" except 0.1uF that use C50313 "Green Cactus" 

for tuning some kind of timbre. 

Tube's cathode bypass capacitor using axial Mallory capacitors.

Coupling capacitors under the board.

Another coupling capacitors that stay in selector position.

Sing-along with McIntosh 275, produce mellow tone and "Real Sound" like expected.

Cheer !!!

Monday, January 11, 2016

McIntosh 275 Modify with Capacitors Adventure Part 2

From part 1 about old McIntosh 275 had repaired but should be modify and repair again.

Finish collecting components for use in this modification.

Arizona capacitors (custom by SPEC.corp/Japan) for all coupling between stages.

Mallory axial electrolytic capacitors for cathode bypass and negative voltage section.

Mundorf electrolytic capacitors for main power supply section.

Inside 275 after finish modification.

Use Western Electric wire lead from RCA jack to first driver tube of both channels.

Power supply section.

Combine 2 types of ultrafast recovery diodes for making bridge rectifier.

M-Lytic from Mundorf for reduce ripple voltage in rectifier.

Install all coupling capacitors.

Arizona capacitors in their suitable positions.

Ohmite "Brown Devil" in driver's rectifier and Siemens MKV parallel with

first electrolytic capacitor.

Change carbon composition resistor to metal film resistor in power supply section

for accurate and stable voltage.

Old soldier never die.

Thanks Mr Shirokazu Yazaki & Mr Jeff  Day for great suggestion and nice blog.

All new components make McIntosh 275's sound so sweet, vivid, transparent and powerful.

The sound become more "Real Sound" like Mr Yazaki always said.

Enjoy listening experience with one of classic amplifier.

Cheer !!!

Monday, January 4, 2016

McIntosh 275 Modify with Capacitors Adventure Part 1

This is my first modification that almost follow suggestion from Mr Shirokazu Yazaki

in Mr Jeff Day's blog about "Capacitor Adventure" and recommended components

to bring "Real Sound" from Jeff's McIntosh MC30 amplifiers.

After read Jeff's blog, I'm so excited and ask my friend who has McIntosh 275 for modification.

My friend had bought old McIntosh 275 that already repaired from local audio technician.

Almost capacitors had changed and the rest were leaked. :(

So he's not hesitate to modify his McIntosh 275 to "Real Sound" style.

Inside 275 before I do anything. Sprague "Black Beauty" and "Bumblebee" had removed.

Replaced with WIMA MKP and mylar capacitors.

I think many points need to upgrade and repair.

Let's start to bring "Real Sound" from McIntosh 275.