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PostPosted: 22 Sep 2018, 01:16 
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Joined: 26 Dec 2016, 03:46
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Location: Bayarea
ILoveHiFi wrote:
I'm in New Zealand

I see, no wonder you reply in strange hours. Any electronics industry in NZ?


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PostPosted: 22 Sep 2018, 16:06 
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Nah no electornics industry in NZ

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PostPosted: 22 Sep 2018, 17:37 
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Location: Bayarea
ILoveHiFi wrote:
Nah no electornics industry in NZ


I was wonder why you study EE and still spend the time on amplifiers. There's no jobs in hifi amp design even here in the heart of silicon valley. When I was working, I had nothing to do with audio all these years. It's only after I retired, then I just do it as a hobby.

This is such a small field, biggest part of the audio market is taken up by the low and mid fi companies like Pioneer, Onkyo etal. High end stuff is only a tiny little piece of pie. I don't even know how they make money.

Buying parts must be difficult where you are and shipping must be expensive. That's one thing good living in silicon valley, I can order and get things fast here.


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PostPosted: 22 Sep 2018, 18:28 
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My dads planning to start a company, he dosen't want to sell my designs for his first product and hes taking forever to get his own design sorted.

I like hifi, even if I am not selling innovating and researching to entertain my own ears are already worth the time spent

Even if we were not to do anything with amplifiers I have other plans in my life regards, I'd love to make big money if possible with amps but also want fame.
Even if I were to be making big money with amps I still want to do otherthings in life cause amps will get boring one day. I will also run out of ideas one day.

It takes a long time for things to come from China but I have virtually all I need for research and development, we order in advance so generally not a plorbem.
Sometimes we buy locally by online stores in NZ, RS Components I find is fair cost and they sell only geniune high quality components.

I use geniune components for capacitors like erse pulse x capactors and nichicon fine gold for some transitor amps.
We don't like geniune transitors much cause its a massive fortune espically for prototyping.
Sound testing shows cheapo chinese transitors to have better sound.
Never had a plorbem with cheapo small signal transitors from aliexpress and directly from taobao sounds good so I like.

Anything that is not TO-92 package though then I always take care cause many fakes

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PostPosted: 22 Sep 2018, 21:31 
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Location: Bayarea
It's good that you and your father have the same interest. What do you and your father do? How old are you?

I always buy genuine parts, not that it's better, it's the consistency. I don't want to design with one fake part, then get different result when I order again.


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PostPosted: 22 Sep 2018, 21:57 
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As mentioned before 1997, dad is just some electrical engneer retired but previously worked for companies.

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PostPosted: 22 Sep 2018, 23:03 
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I'm actually haven't had any identical op amps built to seriously compare sound of cheapo chinese transistors vs geniune but is something I would do when I have time.

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PostPosted: 22 Sep 2018, 23:21 
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I personally do not believe bipolar transistor make a difference in sound. It's the fT, Vcbo, Vceo, Vbe, beta, Cre, Ccb and Cce spec that I am more worry. I pick the transistors base on this and design counting on this. I don't trust the non genuine parts to be repeatable. If they can guaranty the fake parts are consistent, that I can repeat buy and get the same spec, I have no problem using them. But there goes the rub, they cannot guaranty.

There should be a difference in sound between MOSFET, jFET vs bi-polar transistor.

I don't know about tubes in hifi amps, I intentionally picked the cheapest Chinese tubes for my guitar amps I designed, they sounded beautiful. I don't believe in exotic parts.


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PostPosted: 22 Sep 2018, 23:43 
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Tubes place heavy influence on burn in and both quality, you can't have quality tubes and expect them to sound good while they are fresh.
Allthough internet says 100hours are fully burnt in. My exprience shows most valves takes 500-1000 hours of usage to be fully burnt in and reach best sound.

Not sure about consitency on fake parts, but with same batch from same seller, the consentncy is virtually same on all transistors.
But diffrent seller and diffrent batches is where the questionability of consistency come in play.

As you did mention before output transistors tend to have low frequency response, I think most audio amps are limited by the output stage in terms of frequency response.
I got tons higher frequency response with small signal transistor output stage compared to beffy ones that can Class A.

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PostPosted: 23 Sep 2018, 00:07 
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I think theres little advantage of mosfets since the open loop gain is lower compared to transistors, maybe good for output stage and inputs.
http://cmosedu.com/jbaker/students/thes ... ifiers.pdf

If you rember I told you about this PDF on page 3 where it talkes about indirect comensation which you can use to improve frequency response of your op amp stage your currently using.
If you look at some of its 3 stage mosfet op amp desings the open loop gain is only about 90-100db, this is even lower gain than 2 stage transitor op amps

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