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Idiot seeks help with Hiraga
Idiot seeks help with Hiraga
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Old 2nd September 2017, 12:45 PM   #21
JeffYoung is offline JeffYoung  Ireland
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Idiot seeks help with Hiraga
Have the 4 big electrolytics on the top been changed? Depending on amount of use, 30 years of ripple could have them in a pretty sorry state.

That being said, the Wima polyester bypass caps underneath look like current production so I can't imagine them being 30 years old. And it seems like good odds that the 'lytics were changed out at the same time the Wimas were put in....
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Old 2nd September 2017, 01:03 PM   #22
Pano is offline Pano  United States
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Idiot seeks help with Hiraga
Quote:
Originally Posted by eduard View Post
Hello,
Are you talking to me?
No, Farflunger. Maybe we can see what he's got in the PSU section. Since you were talking about adding L and may more C to his power supply.

Yes, I built a Hiraga amp with a toroidal transformer. I took a lot of crap for that one.
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Old 2nd September 2017, 01:34 PM   #23
awolff761 is offline awolff761  United States
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Farflunger,
In general, the fault for poor soundstage, separation, et al is the use of a single power supply for both stereo channels. The fix is either to use two supplies or replace the existing output capacitor(s) with units having much larger values and higher voltage ratings. This can get expensive, bulky and inconvenient, unfortunately. Some example values: 2200/4700uF@60V replace with 10,000uF (or double that!) at the same or higher voltage. The overall philosophy is that caps store energy and a surge (drain) in one channel should not affect the other channel. Higher-voltage caps than the supply mean that the caps are under-stressed. Good Luck!
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Old 2nd September 2017, 02:06 PM   #24
eduard is offline eduard  Netherlands
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Hello,
The caps in the original design were bigger. I mean much bigger than usual in those days.
The caps used in the amp from the original poster are probably 1000000F 40 volts.
Changing this amp into double mono would imply a new chassis. I would go for choke input like the one i described before.
Now having a 100000F right after the rectifier is giving the transformer and the rectifier a hard life. I could well imagine adding a 33000F cap after that a choke and putting the two present caps in parallel would already give a nice improvement.
greetings, Eduard
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Old 2nd September 2017, 02:34 PM   #25
rickmcinnis is offline rickmcinnis  United States
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Quote:
Originally Posted by awolff761 View Post
Farflunger,
In general, the fault for poor soundstage, separation, et al is the use of a single power supply for both stereo channels. The fix is either to use two supplies or replace the existing output capacitor(s) with units having much larger values and higher voltage ratings. This can get expensive, bulky and inconvenient, unfortunately. Some example values: 2200/4700uF@60V replace with 10,000uF (or double that!) at the same or higher voltage. The overall philosophy is that caps store energy and a surge (drain) in one channel should not affect the other channel. Higher-voltage caps than the supply mean that the caps are under-stressed. Good Luck!
This man speaks the truth.

I have found that unless all of the components in the chain from source to loudspeakers are "dual mono" you have no idea how spacious stereo can sound.

It is not a subtle difference.
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Old 2nd September 2017, 03:29 PM   #26
Soundhappy is offline Soundhappy  France
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Ugrade modification can be new 0.47R source power resistors.

Big 12 watts Mills MRA12 easy to do

Mills MRA-12 Resistors

With this your sound stage , voices and acoustic instrument timbral content be nice natural.
Non-inductive version of wire wound have less Johnson noise is very quiet and sound transparent
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Old 2nd September 2017, 05:30 PM   #27
eduard is offline eduard  Netherlands
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Quote:
Originally Posted by Soundhappy View Post
Ugrade modification can be new 0.47R source power resistors.

Big 12 watts Mills MRA12 easy to do

Mills MRA-12 Resistors

With this your sound stage , voices and acoustic instrument timbral content be nice natural.
Non-inductive version of wire wound have less Johnson noise is very quiet and sound transparent
Hello,
At the time i did built Hiraga amps ills were not available. I did however use wirewound resistors that were constructed the same way Mills are.
So the original poster did get some ideas to improve his amp.
BUT there are not many Hiraga amps with choke input power supply!!
Greetings, Eduard
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Old 2nd September 2017, 05:43 PM   #28
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by eduard View Post
BUT there are not many Hiraga amps with choke input power supply!!
Greetings, Eduard
@ Eduard

Sure choke input psu that is excellent upgrade
Just more complicated to make them correctly.
Little trimmer with vertical on the top viper for offset
easy position regulation that simple to do.
Greetings
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Old 2nd September 2017, 06:01 PM   #29
eduard is offline eduard  Netherlands
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Hello
Little trimmer with vertical on the top viper for offset
easy position regulation that simple to do.
???
If You use ll2733 lundahl and you have around 24 volts dc on the first cap you should have 24 divided by 100 mH ( LL2733 inductance with two coils in parallel) = 240mA bleeder current. So you should put a 100 ohm BIG resistor across the first cap that comes after the choke. Sone one in the negative and one in the positive part of the supply.
NOW people will tell you. This a class A amp there will always be a current running no need for the two 100 ohm resistor. But better be safe than sorry i would say.
OF COURSE you will need a transformer with a higher secundairy voltage. So for the same VA rating you will get less current because of the higher voltage.
But the transformer will work better with choke input so no need to worry about that.
Greetings, Eduard
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Old 2nd September 2017, 08:41 PM   #30
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by eduard View Post
Little trimmer with vertical on the top viper for offset easy position regulation that simple to do.
???
What i see is very tricky acrobatic to regulate output offset with horizontal viper position of the trimmer.
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