Hi everybody
I'm planning to build a pseudo-passive preamp. I would like to have an outbut buffer to avoid getting too fussy about cables and impedances (this IMHO, any different is welcome). I am discovering Mr. Pass' work and I'm wondering which design could suit my needs.Very boring topic for most of you, I fear, since I'm a newbie and I know little about Mr. Pass' designs. For example I found "Balanced line stage" (is that BOSOZ? and what is X-BOSOZ then?) very interesting, but:
I don't think I'll need 10 dB gain, do you? I thought unity gain was enough, but perhaps I'm out of way
I didn't fully understand how tu run it with both inputs and outputs unbalanced (negative input to ground? and negative output?)
Sources will be ordinary Cd players or phono preamps, amps will be a D class (DIY, probably UcD) and possibly a Dynaco ST70.
Anyone can give me advice?
Thanks
I'm planning to build a pseudo-passive preamp. I would like to have an outbut buffer to avoid getting too fussy about cables and impedances (this IMHO, any different is welcome). I am discovering Mr. Pass' work and I'm wondering which design could suit my needs.Very boring topic for most of you, I fear, since I'm a newbie and I know little about Mr. Pass' designs. For example I found "Balanced line stage" (is that BOSOZ? and what is X-BOSOZ then?) very interesting, but:
I don't think I'll need 10 dB gain, do you? I thought unity gain was enough, but perhaps I'm out of way
I didn't fully understand how tu run it with both inputs and outputs unbalanced (negative input to ground? and negative output?)
Sources will be ordinary Cd players or phono preamps, amps will be a D class (DIY, probably UcD) and possibly a Dynaco ST70.
Anyone can give me advice?
Thanks
Take a look at the BUF634. http://www-s.ti.com/sc/ds/buf634.pdf
Run it of a couple of 12V SLA batteries and add a DACT CT2 in front and you've got a hell of a "pseudo-passive" preamp
http://www.dact.com/html/attenuators.html
Run it of a couple of 12V SLA batteries and add a DACT CT2 in front and you've got a hell of a "pseudo-passive" preamp
http://www.dact.com/html/attenuators.html
Attachments
Take a IRF610 and use it as a follower. Like my SEWA design, only with lower idle current. Look here:http://www.diyaudio.com/forums/showthread.php?postid=912796#post912796
here are some more ideas: http://www.muzique.com/lab/buffers.htm
here are some more ideas: http://www.muzique.com/lab/buffers.htm
st2_998 said:
I read the BUF634 spec sheet, seems interesting.
Have you got a schematic idea for this?
Here's what you are thinking about.
http://home.broadpark.no/~viiaudio/projects-filer/PhoenixRA.SCH.pdf
For unity gain, simply delete U1 and run your signal into R3/R9. There will be some offset.
Or, if you want feedback and low offset, delete R1/R7 and use 220pF for C1/C2.
Something like this is interesting:
(JFETs are really popular these days)
http://www.muzique.com/images/buff4.gif
(JFETs are really popular these days)
http://www.muzique.com/images/buff4.gif
Attachments
Banned
Joined 2002
I've attached a photo of what i use for a passive Pre-Amp. I run a few Mini Aleph's Right at the moment i'm using the bozos Pre-amp Built from Twisted Pearl Audio. In some cases i can say that just running my cd player into a volume ( passive Pre-Amp ) and into a set of aleph's It sounds way better more controlled. I have tried DACT switches and didn't like them Over time they fail and sound horrible. BrianGt had a 150$ on in his gain-clone and when i was using it it sounded like HARSH CRAP! a wasted 150$ on a dact EW. Right now in this cheap YES cheap passive is a peter daniel volume pot it's a Alps. Im happy with it till i get more money to buy a way better one.
Do we really need a pre-amp to run these amps ? I was told we do but i just proved to my self that we don't. NOW if you need lots of output and hi volumes you might need a pre-amp. I have found running the alephs in Se mode they are pretty loud running a passive Pre-Amp.
Maybe i can try that simple circuit that Mad_K has attached.! Have you run it yet Mad_K ?
Do we really need a pre-amp to run these amps ? I was told we do but i just proved to my self that we don't. NOW if you need lots of output and hi volumes you might need a pre-amp. I have found running the alephs in Se mode they are pretty loud running a passive Pre-Amp.
Maybe i can try that simple circuit that Mad_K has attached.! Have you run it yet Mad_K ?
An externally hosted image should be here but it was not working when we last tested it.
Lot of ideas Mad_K
As for "Phoenix" when using only BUF634 perhaps an input cap would be needed?
I'd like a "pure passive" pre, but I'd like also to play with different cables and amps, so I think I need a buffer stage
Well I'll build a pre with opamp, mosfet, jfet and tube output buffer, strike repeat on my CD and A-B-C-D'ing all the time 'till my girlfriend kicks me out of home
As for "Phoenix" when using only BUF634 perhaps an input cap would be needed?
I'd like a "pure passive" pre, but I'd like also to play with different cables and amps, so I think I need a buffer stage
Well I'll build a pre with opamp, mosfet, jfet and tube output buffer, strike repeat on my CD and A-B-C-D'ing all the time 'till my girlfriend kicks me out of home
Back and serious...
I read on passdyi about discontinued preamps like Aleph P, L etc.
Browsing the forum I understood there were some problems about technical infomation on these designs.
I know little or nothing about this point but I'm really impressed by Mr. Pass' approach in sharing his work with DIYers, and it is sad to see that somebody took advantage on his generosity.
I would be interested in these designs, I saw there are also PCBs out there...
The matter is that I would like to understand them better prior to build one, even if it is a kit. Are there descriptions, white papers, product sheets about?
Thanks
I read on passdyi about discontinued preamps like Aleph P, L etc.
Browsing the forum I understood there were some problems about technical infomation on these designs.
I know little or nothing about this point but I'm really impressed by Mr. Pass' approach in sharing his work with DIYers, and it is sad to see that somebody took advantage on his generosity.
I would be interested in these designs, I saw there are also PCBs out there...
The matter is that I would like to understand them better prior to build one, even if it is a kit. Are there descriptions, white papers, product sheets about?
Thanks
Banned
Joined 2002
audionut said:I have tried my aleph 3's with and without a BOSOZ...With the BOSOZ sound has more authority...base is stronger and of course, yu can play CD's louder...
I find that too. BUT with out the pre-amp running them single ended it sounds more detailed.
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