MODIFY STEREO SYSTEM TO IMPROVE PERFORMANCE, RELIABILITY AND SOUND QUALITY!

[CASSETTE DECK]

It is possible to greatly improve the performance, reliability and sound quality of stereo systems by making relatively straightforward modifications.
Add useful features to maximize enjoyment from your stereo systems!
http://forums.phxaudiotape.com/showthread.php/3974-Dazen’s-Digest?p=78045#post78045

HOME STEREO SYSTEMS - complete systems and individual components including turntables, tape decks, tuners, amplifiers, speakers and headphones.
http://www.tapeheads.net/showthread.php?t=29306

CAR STEREO SYSTEMS.

BOOMBOX TYPE PORTABLE STEREO SYSTEMS - with or without detachable speakers.
Add Volume Boost and Automatic Battery Charger + other useful features.
http://www.tapeheads.net/showthread.php?t=21751

PERSONAL STEREO SYSTEMS.

Has anyone else got stories to tell of successful modifications to stereo systems or individual components?
I will be adding a few of my own success stories to this thread.

LIST OF MODIFICATIONS:

HITACHI HA-6 Stereo Amplifier
SONY CFS-W404S Boombox
AKAI AJ-208 Boombox
PANASONIC RX-CS720 Boombox
FAIR MATE RD1212 Mini Stereo
GEC EA 3-5636A Boombox
KEF CODA III Speakers

 

[Dazen1]

Looking forward to this thread Chris.

I don't really have any stories of note to add myself but I'm always keen to learn any new tricks. Definitely interested in any boombox/Walkman articles.

 

[CASSETTE DECK]

HITACHI HA-6 STEREO AMPLIFIER modification

I had problems with the output transistors overheating due to inadequate heat transfer from the heatsink bracket to the main finned heatsink. The only heat transfer was through a thin aluminium tube filled with coolant.

The solution I came up with is to drill a hole to drain coolant, then solder heatsink bracket directly to each fin using aluminium solder. I had to remove heatsinks to solder on top of stove element.
This solution worked extremely well! I have not had any problems with power transistors overheating since.

www.johnmears.co.uk/hitachipages/hitachiha6_7.htm

 

[CASSETTE DECK]

SONY CFS-W404S Boombox with graphic equalizer

List of modifications:

1 Drill 16mm holes, glue piezo ceramic electrostatic tweeters into holes to improve high frequency response.

2 Removed decoupling capacitors on power amplifier input to reduce high frequency rolloff.

3 Removed 1000uF coupling capacitors, replaced with 2200uF to improve low bass response.
3.2 ohm speakers.

4 Fitted Automatic Battery Charger with light to indicate rate and state of charge.
Installed 6 9000mAh rechargeable Ni-MH D cells
http://www.tapeheads.net/showthread.php?t=21751

5 Fit 12 volt DC input socket with low dropout voltage regulator.

6 Reinforced handle brackets with plastic laminations and super glue.

7 fitted circuit breaker.

 

[CASSETTE DECK]

AKAI AJ-208 Boombox

List of modifications:

1 Removed 470uF coupling capacitors, repalced with 2200uF to improve low bass response.
3.2 ohm speakers.

2 Removed decoupling capacitors on input to power amplifier to reduce high frequency rolloff.

3 Fitted 12 volt DC input socket.

4 Fitted Automatic Battery Charger circuit with light to indicate rate and state of charge.
Installed 5 5000mAh rechargeable Ni-MH C cells.
http://www.tapeheads.net/showthread.php?t=21751

5 Reinforced handle with plastic laminations and super glue.

6 Soldered copper leads to circuit board tracks around power amplifier to improve heat transfer.

7 Fitted circuit breaker

 

[Miracle Mile]

Has anyone else got stories to tell of successful modifications to stereo systems or individual components?
I will be adding a few of my own success stories to this thread.

I have done several tweaks to headphones to improve their soundquality, will get back in here later on.

 

[CASSETTE DECK]

Panasonic RX-CS720 Boombox with detachable speakers and graphic equalizer

List of modifications:

1 Enlarged heatsink for power amplifier IC.

2 Removed 470uF coupling capacitors, replaced with 3300uF to improve low bass response. That's 7 times the original value! Yikes! 2.7 ohm speakers.

3 Removed decoupling capacitors on input to power amplifier to reduce high frequency rolloff.

4 Fitted 2 stage Automatic Battery Charger with lights to indicate power on, boost charge, rate and state of charge. Installed 6 9000mAh rechargeable Ni-MH D cells.
http://www.tapeheads.net/showthread.php?t=21751

5 DC input socket to be fitted later.

6 Fitted circuit breaker.

 

[CASSETTE DECK]

I have done several tweaks to headphones to improve their soundquality, will get back in here later on.

I'm keen to read your tips on maximizing the sound quality of headphones and I will be adding these to my list of tricks.

 

[CASSETTE DECK]

FAIR MATE RD1212 Mini Stereo

List of modifications:

1 Removed 470uF coupling capacitors, replaced with 1000uF to improve low bass response.
8 ohm speakers.

2 Removed decoupling capacitors from input to miniature power amplifier IC to reduce high frequency rolloff.

3 Mounted piezo ceramic electrostatic tweeters.

4 Soldered copper leads to circuit board tracks around amplifier to improve heat dissipation and reduce operating temperature.

5 Fitted Automatic Battery Charger with light to indicate rate and state of charge.
Installed 6 2100mAh rechargeable Ready 2 Use Ni-MH AA cells.
http://www.tapeheads.net/showthread.php?t=21751

6 12 volt DC input socket to be fitted later.

7 Fitted circuit breaker.

 

[CASSETTE DECK]

Looking forward to this thread Chris.

Definitely interested in any boombox / Walkman articles.

More boombox modifications to add soon but I haven't modified any walkman type personal stereos yet.

 

[CASSETTE DECK]

GEC EA 3-5636A Boombox

List of modifications:

1 Removed 470uF coupling capacitors, replaced with 1000uF to improve low bass response.
8 ohm speakers.

2 Removed decoupling capacitors to reduce high frequency rolloff

3 Soldered copper leads to circuit board tracks around power amplifier to improve heat dissipation and lower operating temperature.

4 Changed value of resistors in series with tape head from 22k to 12k to adjust record level.

5 Fitted 12 volt DC input socket.

6 Fitted Automatic Battery Charger circuit with light to indicate rate and state of charge.
Installed 6 5000mAh rechargeable Ni-MH C cells in parallel with a 7.2 volt 2150mAh Ni-MH battery pack. Over 7Ah total capacity - lasts a very long time!
http://www.tapeheads.net/showthread.php?t=21751

7 Fitted power supply and battery switches.

8 Fitted battery discharge limiting circuit.

9 Fitted circuit breaker

 

[Dazen1]

What are you working on at the moment Chris?

 

[CASSETTE DECK]

What are you working on at the moment Chris?

I am currently working on high current 2 stage float chargers for nickel cadmium power tool batteries. These modified chargers can also charge nickel metal hydride and lithium batteries.

These high current 2 stage float chargers may be useful in other applications such as high power portable stereo systems.

More details later.

 

[Dazen1]

Cool.

Thanks for the reply Chris.

 

[CASSETTE DECK]

KEF CODA III SPEAKERS modification

I have greatly improved the low bass response of this pair of sealed speakers by cutting a hole at the back of each speaker, near the top, and fitting a 15cm length of PVC pipe with a hole diameter of 28mm.

Ventilating speakers reduces the operating temperature at high power levels, and of course improves reliability.

 

[Dazen1]

Kent Engineering & Foundry

Yeah - KEF made some great speakers.

http://www.kef.com/html/gb/explore/about_kef/museum/1980s/Coda_III_Cantor_III_Carlt/index.html

 

[Nick Danger]

I have greatly improved the low bass response of this pair of sealed speakers by cutting a hole at the back of each speaker, near the top, and fitting a 15cm length of PVC pipe with a hole diameter of 28mm.

Ventilating speakers reduces the operating temperature at high power levels, and of course improves reliability.

Venting the cabinet will change the sound of the speaker as well.

 

[CASSETTE DECK]

Yeah - KEF made some great speakers.

http://www.kef.com/html/gb/explore/about_kef/museum/1980s/Coda_III_Cantor_III_Carlt/index.html

Great speakers - they are even better now with improved reliability at high power levels and improved low bass response. There's probably no need for sub-woofers now.
The modification is definitely worth the time and effort.

Venting the cabinet will change the sound of the speaker as well.

Ventilating the speakers has made a significant improvement to the low bass response. It's a much more natural-sounding bass reproduction.