Hi,
It's another candy in there 🙂
Looks like we have somewhat more complex version of BoZ inside a BA-2 front end. And it can be used as an (almost*) stand alone preamp in case that you want more gain, or, perhaps you built a SEWA amp some time ago and need a preamp...
*"Almost" because it will need a buffer on its front end (if you want to place a volume pot on the front).
It's another candy in there 🙂
Looks like we have somewhat more complex version of BoZ inside a BA-2 front end. And it can be used as an (almost*) stand alone preamp in case that you want more gain, or, perhaps you built a SEWA amp some time ago and need a preamp...
*"Almost" because it will need a buffer on its front end (if you want to place a volume pot on the front).
if you look back at several Papa's articles - "Discrete OP for Dumb DIYas from Balkan" (read there - ZM & Vix) ,some of his first amps (A class , A75 - where bootstraping was used ) , then this FE is nothing new .
but - we agree that we are from Balkan ..... so for both of us - main thing is that Papa still use caps in signal path , and that I ( O Tempora , O Mores !) very cleverly recognized some time ago how he manage to use TL431 to bias those thingies ..... without caps in signal path .....
I have just finished reading the article. Thank you Mr. Pass so much for your generous contribution.
Wachara C.
Wachara C.
if you look back at several Papa's articles -
but - we agree that we are from Balkan ..... so for both of us - main thing is that Papa still use caps in signal path , and that I ( O Tempora , O Mores !) very cleverly recognized some time ago how he manage to use TL431 to bias those thingies ..... without caps in signal path .....
Well, we should get over it!!
p.s. I also miss that COOL icon...Now I gotta use this one, resurrected...
Attachments
See i am missing some part here. I have re-read the article several times in fact.
what is the voltage swing at C203?
The voltage swing at C203 is (almost) the same voltage swing you se at the output. Remember the output stage do not have any gain.
I have a complaint.
Nelson's articles are addictive. It was around 4:30 in the morning, I woke up for some reason, and found this article. I read it and I am ready to start soldering!
Now if we put some practical taught to it, Nelson should put together a book:
Class A Amplifiers for insomniacs.
🙂🙂🙂
Nelson's articles are addictive. It was around 4:30 in the morning, I woke up for some reason, and found this article. I read it and I am ready to start soldering!
Now if we put some practical taught to it, Nelson should put together a book:
Class A Amplifiers for insomniacs.
🙂🙂🙂
can we use match sj103 for the diferrential and 2sk246 for ccs?
maybe paraleling 2 of 2sj103?
its very hard to find 2sj74 in my country.
maybe paraleling 2 of 2sj103?
its very hard to find 2sj74 in my country.
There would be no reason why you couldn't invert the polarity
of the front end, using N channel inputs and a P channel VAS.
If you do so, you will want to find some P channel Mosfets
which don't have the "IR P channel distortion" for best results.
🙂
of the front end, using N channel inputs and a P channel VAS.
If you do so, you will want to find some P channel Mosfets
which don't have the "IR P channel distortion" for best results.
🙂
PDF updated
The output stage diagram has been updated. The PDF revision has been updated to Rev 2.0.
The output stage diagram has been updated. The PDF revision has been updated to Rev 2.0.
cviller is working on it again. He has some preliminary designs that he will post very soon, but the concept has changed, which made it more reasonable to wait for hthe BA-2 to be revealed. The idea is to have the gain stage board separate so that it will work for BA-1 and BA-2 with additional different small bias boards for the two types of amps That way, with one board we can make both types of amps and/or have an external gain stage. It will be posted here in a few days. Nelson intended this to be a fundraiser for diyAudio so we want to be the only ones making the boards, but we realize that a responsibility goes with that- moving ahead!
Shortly we will have a design for your comments and input, then a Group Buy listed in the wiki and the GB areas..
Of course the hope is that many more people make these amps than the few that got amp chassis at BAF
Mark
-Variac
Shortly we will have a design for your comments and input, then a Group Buy listed in the wiki and the GB areas..
Of course the hope is that many more people make these amps than the few that got amp chassis at BAF
Mark
-Variac
If a group buy for PCBs will be available, I think it will be a good idea to also make a group buy for matched Mosfets and Jfets as well.
Wachara C.
Wachara C.
Oh good i was hoping the front end would be a separate board!
A group buy for the jfets would be nice!
A group buy for the jfets would be nice!
I just did a quick layout of the frontend for you guys to comment on. The silk screen is still a bit messy and a few components will be aligned more nicely later. But I would like to get some feedback.
I have attached a blue/red version, where blue is bottom and red is component layer.
The green version gives a better impression of how the boards will look like when produced.
Attachments
Any chance the large connection pads could be a little bit further apart?
I will use Keystone turret terminals instead of soldering to the board thru hole directly, since they're going to get taken apart and put back together a lot. The larger ones like #1503 have a collar on the top of that is 0.187" (4.8mm) so they get VERY close on the F5 power supply boards I have now.
Tom
I will use Keystone turret terminals instead of soldering to the board thru hole directly, since they're going to get taken apart and put back together a lot. The larger ones like #1503 have a collar on the top of that is 0.187" (4.8mm) so they get VERY close on the F5 power supply boards I have now.
Tom
Hmm.. I have to think about that. The reason for the distance (~5mm) I have chosen is that it fits with many standard terminals. If you can point me to some reasonably priced easy to get terminals of a different spacing than 5mm, I might change it.
BTW: The board is 2.7x5.4 in inches.