@RNMarsh
What do you think of locating the xformer and filter caps in a separate box away from the circuit? This is the approach that JC took in his Blowtorch pre-amp. where you see he had the psu separated from the pre-amp.
However, I would definitely put my regs on same board as head amp or close as possible for this head amp.
What do you think of locating the xformer and filter caps in a separate box away from the circuit? This is the approach that JC took in his Blowtorch pre-amp. where you see he had the psu separated from the pre-amp.
However, I would definitely put my regs on same board as head amp or close as possible for this head amp.
I didnt know JC did that -- havent seen a Blowtourch. But, I use the same method. two xfmrs and rect and filt cap in a seperate box. Run the two raw dc to the amp/pwr supply with PSright beside the amp circuit. Better would be to make both reg ps on same pcb as amp. -RNM
Behold, from the original thread, the CTC Blowtorch.
http://www.diyaudio.com/forums/solid-state/71189-john-curls-blowtorch-preamplifier-2.html#post810164
I did notice one thing when I read the Blowtorch thread a couple of years ago. The amount of the room in the chassis. My guess is we should aim for a chassis that just fits. The Goldilocks Principle - just right.
Not too big, not too small.
http://www.diyaudio.com/forums/solid-state/71189-john-curls-blowtorch-preamplifier-2.html#post810164
I did notice one thing when I read the Blowtorch thread a couple of years ago. The amount of the room in the chassis. My guess is we should aim for a chassis that just fits. The Goldilocks Principle - just right.
Not too big, not too small.thank you...
although still theres question left in my mind I find your design are worth keeping...thank you again for the contribution and will follow this thread...
regards,
joel
although still theres question left in my mind I find your design are worth keeping...thank you again for the contribution and will follow this thread...
regards,
joel
junk!
The 2n5457 from Tayda Electronics are junk. Looking at face of TO-92, it's GSD. It should be the reverse per the Fairchild and OnSemi datasheets. Using the set up recommended by Richard Marsh, I got 11.2 mA, or about 11.2 V across the 1k resistor.
As per the datasheet, I tied gate and source to ground. I set +15V to the drain...darn things overheated!
The 8 pcs. of the 2n5460 measured right in the middle of the datasheet for Idss. 3.5mA so I feel better about those. I've got about 40 pcs. of each jfet on order from Futurelec. I'll keep you posted on those.
The 2n5457 from Tayda Electronics are junk. Looking at face of TO-92, it's GSD. It should be the reverse per the Fairchild and OnSemi datasheets. Using the set up recommended by Richard Marsh, I got 11.2 mA, or about 11.2 V across the 1k resistor.
As per the datasheet, I tied gate and source to ground. I set +15V to the drain...darn things overheated!
The 8 pcs. of the 2n5460 measured right in the middle of the datasheet for Idss. 3.5mA so I feel better about those. I've got about 40 pcs. of each jfet on order from Futurelec. I'll keep you posted on those.
Well, I have receive the new MJE200/210 from On Semi. The result...quite disgusting again. Total I have 400 pieces and 0 pairs. If I mix from both Fairchild and On Semi I could get 4 pairs... out of 400. Not very good!!
I look around to find other possibilities from what I have at home. I find this:
- BD139/BD140: Seems quite adequate - same body and pin-out, similar characteristic
and, what is even more important, MUCH easier to find complements. Out of 80
pieces, I found 13 perfect pairs.
- 2SB649/2SD669: same body and pin-out, not so similar characteristic. The sad part
is that for the parts I have the Vbe is not equal for PNP and NPN groups. One is
0,70v and the other 0,72v.
- 2SA1306/2SC3298: not very good, different body, different pin-out and dissimilar
electrical characteristic. But, maybe?
Could you please Mr. Marsh tell me your opinion about this candidates? Thanks in advance.
Javier
I look around to find other possibilities from what I have at home. I find this:
- BD139/BD140: Seems quite adequate - same body and pin-out, similar characteristic
and, what is even more important, MUCH easier to find complements. Out of 80
pieces, I found 13 perfect pairs.
- 2SB649/2SD669: same body and pin-out, not so similar characteristic. The sad part
is that for the parts I have the Vbe is not equal for PNP and NPN groups. One is
0,70v and the other 0,72v.
- 2SA1306/2SC3298: not very good, different body, different pin-out and dissimilar
electrical characteristic. But, maybe?
Could you please Mr. Marsh tell me your opinion about this candidates? Thanks in advance.
Javier
I have used the 2SB649AC/2SD669AC with success -- the late Randy Stone's favorite driver transistor for lateral mosfets.
@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.
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.
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
@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
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.
@ 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.
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.
The next step after building?
http://www.amazon.com/Multimedia-Ad...=UTF8&colid=G5XF9NP2L47T&coliid=IVT5SFAEWDKID
This is on my post Xmas wish list. What do you think, Mr. Marsh?
http://www.amazon.com/Multimedia-Ad...=UTF8&colid=G5XF9NP2L47T&coliid=IVT5SFAEWDKID
This is on my post Xmas wish list. What do you think, Mr. Marsh?
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.
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.
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.
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.