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Old 23rd July 2012, 09:51 PM   #391
Unomas is offline Unomas  Spain
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Originally Posted by RNMarsh View Post
The output transistors just needs a beta of greater than 100. take the highest Hfe from the mje200 and the lowest from the mje210.... but do get a match on the Vbe --something like .72 should be easy to find. The topology, currents and transistor will take care of the rest. On the 2N 50xx types, they can be matched for Hfe and Vbe. The jFETs are matched only by the .8 v method shown. that should be all you need to do to get great performance. -RNM
Thanks Mr. Marsh. According to your comments I may have a much easier job. On the JFETs and 2N50xx side there is no problem, I have enough pairs. Regarding the MJEs and taking into account your defined requisites, I could also find candidates from what I already have.

Nevertheless, if there would be any advantage in going the fully complements way, I could still consider the BD139/BD140 as I already have them and I have found very good complements. Do you find them as a viable substitute for the MJE200/210? Thanks for your comments.

Javier
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Old 23rd July 2012, 09:59 PM   #392
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Sonindos, the EXTRA room in the CTC Blowtorch was for ADDED modifications that customers could order.
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Old 23rd July 2012, 10:18 PM   #393
Unomas is offline Unomas  Spain
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@Unomas

As I said before, when I started refurbishing my Adcom 535, it was hard to get PNP/NPN matches and Anatech told me to just do the best that I can do because what we're talking about is an improvement in THD.

I plan to do the same on this project - just get as close as I can with what I have. I'm sorry you have spent so much money with very little payoff for your hard work. Best wishes going forward - sonidos (btw, I am also Javier )

jackinnj - those Hitachis have really shot up in price. Yeeowwww. I'm glad I bought several for my Adcom a couple of years ago. I wonder if the Hong Kong specials are any good on ebay.
Hi Javier, nice to share with you this passion. I also think the Hitachi are great but unfortunately those I have are a bit out of margin. Mr. Marsh specify that they should be Vbe complements. All I have are 0.74v for PNP and 0.80v for NPN so...you see they are not very good for this application.

Javier
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Old 24th July 2012, 01:33 PM   #394
sonidos is offline sonidos  United States
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Sonindos, the EXTRA room in the CTC Blowtorch was for ADDED modifications that customers could order.
Hi,

Sorry, I may have recalled at some point that you commented in one of the BT threads that you had wished it were a bit smaller. But I appreciate that you caught my comment and clarified the reasoning behind the extra space within the chassis. I stand corrected.
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Old 24th July 2012, 01:45 PM   #395
sonidos is offline sonidos  United States
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unomas,

I'll keep my existing order of OnSemi transistors if you found that to be the case with the Hitachis. I also have some Sanyo drivers that could work so it will be interesting to see what I yield when I have all the parts in.

Regards,

Javier
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Old 24th July 2012, 01:51 PM   #396
sonidos is offline sonidos  United States
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@ RNMarsh

For PSU regulation, I'll go with the good ol' fashioned 317/337 combo for now. I know you (and other designers like JC) say topology, topology, and topology are important. How much emphasis do you give on PSU performance in this circuit?

There is a section on the forum devoted to psu design, questions, etc. and I even have some boards to build a Salas shunt regulator. Although I often move slow due to work and family needs, I plan to try some different things with this circuit, psu being one of them.

Thanks for all your input.
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Old 24th July 2012, 02:51 PM   #397
sonidos is offline sonidos  United States
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The next step after building?

http://www.amazon.com/Multimedia-Adv...=IVT5SFAEWDKID

This is on my post Xmas wish list. What do you think, Mr. Marsh?
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Old 24th July 2012, 02:52 PM   #398
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Originally Posted by Unomas View Post
Thanks Mr. Marsh. According to your comments I may have a much easier job. On the JFETs and 2N50xx side there is no problem, I have enough pairs. Regarding the MJEs and taking into account your defined requisites, I could also find candidates from what I already have.

Nevertheless, if there would be any advantage in going the fully complements way, I could still consider the BD139/BD140 as I already have them and I have found very good complements. Do you find them as a viable substitute for the MJE200/210? Thanks for your comments.

Javier
Those BDs are fine to use, get the highest hfe ones, these parts will be far superior to the mje200s in this application. They are faster, have much lower parasitic capacitances and as the amp probably runs on higher than 10v their SOA figures are fine.
Another alternatives is MJE172/182, or 2sa1930/2sc5171.
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Old 24th July 2012, 05:55 PM   #399
Unomas is offline Unomas  Spain
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unomas,

I'll keep my existing order of OnSemi transistors if you found that to be the case with the Hitachis. I also have some Sanyo drivers that could work so it will be interesting to see what I yield when I have all the parts in.

Regards,

Javier
Hi again,

This is my personal case but I could not say it would be a general situation. I ordered the Hitachi parts through eBay from an unknown eastern supplier so... I would not say all of them are going to be like this!
Maybe is better to have other inputs before raising a conclusion.
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Old 24th July 2012, 06:02 PM   #400
sonidos is offline sonidos  United States
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Unomas,

Ok, I can agree with that. The Hitachi's that I sourced was through MCM Electronics 2 years ago. I found the receipt. I paid almost $.90 for each. I'll dig them up and test them once I get a jig together to measure Vbe.

I generally source through Mouser, Digi-Key, Avnet Express, and B&D Enterprises here in the US.
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