Yamaha AX-390

Predator864 · 9th March 2008, 09:56 PM

Well, this amp was built in `96.
Nicely built, with 2 transformers, some Elnas and mostly ceramic caps.

I like how this amp sounds, but i think it can do better.

My first and obvious ideea is to change the 2 large reservoir caps. They`re 6800uF at 56V, a small to fair value I guess. Even my CDP has a larger reservoir cap ( 10.000 uF

). I have 2 Russian 15.000uF/80V caps next to me, doing nothing. But this is this enough ?

In the next part, I will remove those 2 ceramic caps at the CD-P input.
And afterwards, I dont know.

That`s we`re you guys come in. Help me improve this little beast.

Predator864 · 10th March 2008, 04:48 PM

Good news:

Purchased 2x31000uF Sprague capacitors.

http://i26.tinypic.com/otho8y.jpg
http://i30.tinypic.com/10d5xms.jpg

Predator864 · 10th March 2008, 06:22 PM

Damn, cannot edit.
Measured the main transformer voltages.
~35,5V in IDLE
~35V in LOAD

And this gives us a theoretical voltage in VDc
~50,055V in IDLE
~49,35V in LOAD

If we include the diodes dropout (which i didnt calculate) i think (theoretical) we will have ~ 48V in LOAD.
Pretty close to my 2 Sprague capacitors.

What do you think ?

Leolabs · 11th March 2008, 02:28 AM

You need something like 63V but i don't think changing something 6800uF to 31000uF will improve so much on the sound.Get yourself a pair of 10000uF/63V are enough.Better spend some $$$ on replacing the ceramic caps with something better.

Predator864 · 11th March 2008, 05:12 AM

Well the ceramic caps are Toshiba. I`m thinking not to change them. Only where that is necessary.

Gladly, my 2 31000uF we`re a bargain ( 10 Euros ).

Predator864 · 24th March 2008, 06:59 PM

Hi,

A small "choosing" problem.

1. 10000uF/63Vx2 Korea Chemi-Con. 10$ both.
2. 12000uF/63Vx2 Nippon Chemi-Con. 12$ both.
3. 10000uF/63Vx2 ROE. 10$ both .

Leolabs · 25th March 2008, 02:21 AM

Any pic on the ROE???

Predator864 · 25th March 2008, 05:07 AM

http://i32.tinypic.com/2rfpiqe.jpg - number 19
and those 2 chemis:
http://i26.tinypic.com/1sb6gk.jpg
number 14 and 15.

Predator864 · 3rd April 2008, 05:13 PM

I`ve searched for parts that might be changed to gain some improvements.

The first thing, is the bridge rectifier. I might change this to four Schottkys and bypass them with 0,1uF ceramic. Before the bridge I`m thinking about putting some coils and 1Ohm resistors.

Next to the Power Transistors I`ve spotted some resistors that might be changed: 2x47O, 2x560, 2x47K, 2x100K, 2x6,8K, 4x5,6K. There are no pots. The collector-emitter Voltage might be changed by using another fixed resistor.

The Power Transistors are made by Sanken : 2SA1695/2SC4468.

The final Reservoir Caps are 2 Siemens AL-ELKO 17,000uF 75V.

Predator864 · 21st May 2008, 10:34 AM

OK, I received the caps yesterday. They are pretty heavy and bulky.
I focused my attention on the Amplifier CD Player Input.

2 Ceramic caps, 6 resistors, 2 electrolytics and one OPAMP (NJM2068).
The NJM is in SIL Package. Some Browndogs adaptors will fix this.
I am interested in changing this OPAMP.

I have the following at hand: OPA132, OPA2132, THS4032.
The CD Player is equipped with LT1361 which has a pretty high slew rate.

The CDP DC offset is low, 2-3mV, while the amplifier offset is 15mV (peak)

Here is the input PCB : http://www.uploadgeek.com/uploads456/0/P3106818.JPG

9th March 2008, 09:56 PM	#1
Predator864 diyAudio Member Join Date: Mar 2008	Yamaha AX-390 Well, this amp was built in `96. Nicely built, with 2 transformers, some Elnas and mostly ceramic caps. I like how this amp sounds, but i think it can do better. My first and obvious ideea is to change the 2 large reservoir caps. They`re 6800uF at 56V, a small to fair value I guess. Even my CDP has a larger reservoir cap ( 10.000 uF ). I have 2 Russian 15.000uF/80V caps next to me, doing nothing. But this is this enough ? In the next part, I will remove those 2 ceramic caps at the CD-P input. And afterwards, I dont know. That`s we`re you guys come in. Help me improve this little beast.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Yamaha AX-930	jleaman	Analogue Source	6	21st November 2010 11:43 AM
Yamaha cdx 900	stex	Digital Source	4	23rd January 2010 11:44 AM
Yamaha RX-777	quasi	Solid State	4	15th November 2007 12:58 PM
Yamaha A-550	angel	Solid State	4	18th January 2006 01:22 AM
Yamaha CDX-490	newbie123	Digital Source	1	3rd December 2005 03:31 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

10th March 2008, 04:48 PM	#2
Predator864 diyAudio Member Join Date: Mar 2008	Good news: Purchased 2x31000uF Sprague capacitors. http://i26.tinypic.com/otho8y.jpg http://i30.tinypic.com/10d5xms.jpg

10th March 2008, 06:22 PM	#3
Predator864 diyAudio Member Join Date: Mar 2008	Damn, cannot edit. Measured the main transformer voltages. ~35,5V in IDLE ~35V in LOAD And this gives us a theoretical voltage in VDc ~50,055V in IDLE ~49,35V in LOAD If we include the diodes dropout (which i didnt calculate) i think (theoretical) we will have ~ 48V in LOAD. Pretty close to my 2 Sprague capacitors. What do you think ?

11th March 2008, 02:28 AM	#4
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	You need something like 63V but i don't think changing something 6800uF to 31000uF will improve so much on the sound.Get yourself a pair of 10000uF/63V are enough.Better spend some $$$ on replacing the ceramic caps with something better.

11th March 2008, 05:12 AM	#5
Predator864 diyAudio Member Join Date: Mar 2008	Well the ceramic caps are Toshiba. I`m thinking not to change them. Only where that is necessary. Gladly, my 2 31000uF we`re a bargain ( 10 Euros ).

24th March 2008, 06:59 PM	#6
Predator864 diyAudio Member Join Date: Mar 2008	Hi, A small "choosing" problem. 1. 10000uF/63Vx2 Korea Chemi-Con. 10$ both. 2. 12000uF/63Vx2 Nippon Chemi-Con. 12$ both. 3. 10000uF/63Vx2 ROE. 10$ both .

25th March 2008, 02:21 AM	#7
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Any pic on the ROE???

25th March 2008, 05:07 AM	#8
Predator864 diyAudio Member Join Date: Mar 2008	http://i32.tinypic.com/2rfpiqe.jpg - number 19 and those 2 chemis: http://i26.tinypic.com/1sb6gk.jpg number 14 and 15.

3rd April 2008, 05:13 PM	#9
Predator864 diyAudio Member Join Date: Mar 2008	I`ve searched for parts that might be changed to gain some improvements. The first thing, is the bridge rectifier. I might change this to four Schottkys and bypass them with 0,1uF ceramic. Before the bridge I`m thinking about putting some coils and 1Ohm resistors. Next to the Power Transistors I`ve spotted some resistors that might be changed: 2x47O, 2x560, 2x47K, 2x100K, 2x6,8K, 4x5,6K. There are no pots. The collector-emitter Voltage might be changed by using another fixed resistor. The Power Transistors are made by Sanken : 2SA1695/2SC4468. The final Reservoir Caps are 2 Siemens AL-ELKO 17,000uF 75V.

21st May 2008, 10:34 AM	#10
Predator864 diyAudio Member Join Date: Mar 2008	OK, I received the caps yesterday. They are pretty heavy and bulky. I focused my attention on the Amplifier CD Player Input. 2 Ceramic caps, 6 resistors, 2 electrolytics and one OPAMP (NJM2068). The NJM is in SIL Package. Some Browndogs adaptors will fix this. I am interested in changing this OPAMP. I have the following at hand: OPA132, OPA2132, THS4032. The CD Player is equipped with LT1361 which has a pretty high slew rate. The CDP DC offset is low, 2-3mV, while the amplifier offset is 15mV (peak) Here is the input PCB : http://www.uploadgeek.com/uploads456/0/P3106818.JPG

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)