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Hiraga "Le Monstre"
Hiraga "Le Monstre"
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Old 27th September 2018, 09:38 AM   #1611
N101N is offline N101N
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Can you or anyone else recommend their choice of transistors they use?
It has nowadays become a matter of availability.
The common-emitter predriver is an important feature, but it is much more difficult to implement properly than the Darlington pair.
To solve the NPN-PNP mismatch and unavailability problem, I would consider the circlotron option.
I would stick to a big nonmetallic carbon (based) resistor.
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Old 27th September 2018, 01:19 PM   #1612
vishalk is offline vishalk  United Kingdom
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I'm going to have to Google what you wrote N1! All I want is a link to some suitable transistors I can buy and use. Can't find carbon resistors at 10w, ceramic all day.
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Old 27th September 2018, 06:07 PM   #1613
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Sometimes haste makes waste. Would you adopt a circlotron topology with MOSFET output?
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Old 27th September 2018, 06:56 PM   #1614
vishalk is offline vishalk  United Kingdom
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Well I like simple circuits as it's about all my knowledge and experience will take me. I would like to get this working as best as I can so I can learn and experience the sound and the difference transistor, bias settings have an effect on the overall performance and sound produced.

With the diy hiraga crew on here I have quickly learnt stuff I knew nothing about and now have a semi working hiraga style le monstre.



I would have to research and see the pros and cons of what you suggest as I know nothing about it.


But open to ideas, have you built one of these and yourself used a circlotron topology.
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Old 27th September 2018, 07:36 PM   #1615
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Originally Posted by vishalk View Post
Well I like simple circuits as it's about all my knowledge and experience will take me. [...]
I strongly suggest you stay with this circuit and refine it.
Changing to noninductive resistors is certainly a good thing.

The non-perfect match of NPN and PNP is not a huge issue. The Sanken or OnSemis that have been mentioned are ok and not worse than what has been suggested by Hiraga decades ago.

Its however of utmost importance that the amp is stable with bias and not oscillating.
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Old 27th September 2018, 08:06 PM   #1616
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I'm going to have to Google what you wrote N1! All I want is a link to some suitable transistors I can buy and use. Can't find carbon resistors at 10w, ceramic all day.
No need for carbon. Metal film / foil is good (to me way superior to carbon, but that is of course debatable, just not with me).
A short search at the Farnell site gave me these resistors:
OHMITE TNP10SA1R00FE, not cheap but not crazy expensive either.

They are non inductive, as they are not wirewound. Attach a Heatsink, however.

Again, your first steps must be made based on and improving your engineering knowledge. Try out the fancy things later.
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Old 27th September 2018, 09:54 PM   #1617
vishalk is offline vishalk  United Kingdom
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Default Second channel working! refining and getting it right.

DSC_0977.jpg

Finally the new driver arrived today so i was able to solder it in and get the amplifier working again! We now have both channels working

One has the sankens in and the other has the MJL's.

One thing to note, is the dc offset affected by temperature rise?

I just want to clarify how to setup the bias and dc offset.

1. When everything is cold i switch the amplifier on and adjust the bias till i get around 0.6v. Then i adjust the dc offset which also affects my bias, i generally play and fiddle with each potentiometer until everything is level and the offset is at zero, to be stable generally means i have 0.61v and 0.63v (is that due to the transistors not being exactly matched?)

2. Leave for 1 hour come back and check bias and dc offset, check and adjust as necessary.

3. Play some tunes for an hour, recheck and adjust?

Now when i've done all this and everything is stable and the temperature doesn't move its all singing and working well.

Now when the next day when its at room temperature and been off, if i switch it on and check my dc offset its not at zero, but when the amp starts warming up its starts to slowly moves down zero as at heats?

Is that correct, sometimes its the same with the bias, and also is it me or when its warm it really starts to sound so much better.

It's like i have to switch it on, leave it for to warm up then play my music.

Basically im asking people methods of setting up so i can do the same then know i can leave it and its good to go.

Last edited by vishalk; 27th September 2018 at 10:15 PM.
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Old 27th September 2018, 09:58 PM   #1618
vishalk is offline vishalk  United Kingdom
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Originally Posted by sottomano View Post
I strongly suggest you stay with this circuit and refine it.
Changing to noninductive resistors is certainly a good thing.

The non-perfect match of NPN and PNP is not a huge issue. The Sanken or OnSemis that have been mentioned are ok and not worse than what has been suggested by Hiraga decades ago.

Its however of utmost importance that the amp is stable with bias and not oscillating.
Agreed sottomano, my plan is to refine it and no when and how its stable, can i use my scope or DMM to check if it's oscillating?

Thanks for the link on the resistors i found them cheaper on mouser! So i will order them.

https://uk.farnell.com/bi-technologi...ecSingleItem_1

might give these a go aswell.

The thing is i don't just want "ok" transistors, i want proven and tested transistors that perform well with this circuit that others have recognised.

Last edited by vishalk; 27th September 2018 at 10:11 PM.
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Old 27th September 2018, 10:08 PM   #1619
gaborbela is offline gaborbela  Canada
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How much the DC offset?
Of course, you set up the DC offset at industrial warm.
I had the same issue with my LeMonstre, even the bias moved at warm up.
If you have 1V DC at cold that is not a problem as long as your speaker's protection does not kick in.
Is not possible to put together your heatsinks to create some type of tunnel for your fan, that way would be much more effective. You can buy 5W metal film resistors and carbon films also.
I would buy 2R and use 2PC to get 1R 10W. Did you ever tried plate resistors like KOA etc. to me those acceptable also.
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Old 28th September 2018, 11:40 AM   #1620
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I'll measure the dc offset later today when cold and then warmed up.

Heatsinks are fine at 0.6a no issues with heat.

Will try different resistors to see which more stable.
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