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 !!!

Monday, August 8, 2016

McIntosh MX110z Tuner & Pre-amplifier Modification

Jeff's Place from Jeff Day is one of most inspirational blog for many people including me.

After he's got many suggestions from Mr Shirokazu Yazaki and he's wrote articles in his blog.

I've got many great ideas from him and Yazaki-san to improve my own works.

One of equipment that he always prefers is McIntosh MX110z ; Tuner & Pre-amplifier.

It is famous tube pre-amplifiers from McIntosh like C22, C20, etc.

I've sent information of MX110z's modification from his blog to my friend who has one.

So he's interested too much and brought this to me for modify with "Real Sound" concept.

McIntosh always care about pilot lamp intensity. ;)

Bottom view before modified. So many types of signal coupling capacitors.

2W carbon composition and 5W cement wirewound resistors in power supply section.

Tube's filament power supply for 12.6V and 6.3V tube types.

Electrolytic capacitors also leak and should be replace too.

Some of components for modify MX110z.

My friend want to try 3 types of Arizona Capacitor, so let's do it. :)

"Red Cactus" seldom seen type from Arizona Capacitor.

Bottom view after modification with better parts and mainly consider for "Real Sound".

2 of STTH6112V2 diodes replaced 4 selenium diodes in bridge rectifier position.

Use Ohmite "Brown Devil" & another good quality wirewound resistors in power supply 

for adjusted until high voltages near values in schematic.

Also tube's filament power supply too.

All of signal capacitors replaced.

Western Electric PIO capacitors for higher value capacitance and limit space.

Many tube's stages and many coupling capacitors too.

After finished modify MX110z and bring it back to owner, he really like it.

Better sound from all sources and too sure tuner!

But should be "run in" for a couple months and will tell later for real character of this.

Cheers !!!