[Soymilk]

i'm currently looking at which db to build for my pimeta that i'm planning, and i'm trying to figure out more about my options. through searching, i've found these:

dDB - the millet hybrid db, is it a waste / too expensive to build in a pimeta?

sijosae db - small

monofied sijosae db - better than sijosae db?

qrv05 - has a pcb available for sale, which is a plus i guess, also kinda big


are there others? space isn't really an issue here, since this is going to be a home use pimeta. i'm putting db's in all 3 buffer positions. also, what does CCS stand for? i saw it used multiple times when talking about db's, but nothing ever said what it meant.

 

[heatmizer]

Have seen people use the qrvo5
Tried the sijosae and the monofied stayed with the monofied
ended up using a monofied with bd139 and bd140 on output and bc337 and bc327 on input biased to 20 ma. This is not portable. The sijosae and the monofied are both portable.
Any reason you don't want to use the buf634p?

 

[bhjazz]

For ease of troubleshooting, you should start with the Buf634's, or at least borrow a set from another build. Get your Pimeta working correctly first, then do the upgrade.

The dDB does work. Search this forum for a thread by n_maher. As stated there, though, YMMV. He did say the sound was quite amazing.

 

[n_maher]

The Millett DB's, at about $35 to build (including the pcb), are a definite improvement over the single buf634's. I honestly didn't compare them to stacked buffers but some have and said that they're closer than single buffers if not indistinguishable. Also, there is the careful fact to consider that if you use the millett db boards you'll have to both cut them in half (carefully) and also off-board mount your pot to get it all to fit. Not the easiest bit of casework but doable.

EDIT - CCS stands for constant current source.

EDIT2 - I would not use a DB in the ground channel, that position on the PIMETA pcb if very tight and you'll really be fighting yourself if you do this. If your desire is to have a discrete output stage on each channel just build a PPA V2 and be done with it.

 

[Soymilk]

Quote:

Originally Posted by heatmizer /img/forum/go_quote.gif Have seen people use the qrvo5 Tried the sijosae and the monofied stayed with the monofied ended up using a monofied with bd139 and bd140 on output and bc337 and bc327 on input biased to 20 ma. This is not portable. The sijosae and the monofied are both portable. Any reason you don't want to use the buf634p?

wait, so the monofied is portable, but your monified isn't? i want to build discrete buffers since it's around the same or cheaper than buf634 and should sound better.

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif The Millett DB's, at about $35 to build (including the pcb), are a definite improvement over the single buf634's. I honestly didn't compare them to stacked buffers but some have and said that they're closer than single buffers if not indistinguishable. Also, there is the careful fact to consider that if you use the millett db boards you'll have to both cut them in half (carefully) and also off-board mount your pot to get it all to fit. Not the easiest bit of casework but doable. I would not use a DB in the ground channel, that position on the PIMETA pcb if very tight and you'll really be fighting yourself if you do this.

is it ~$35 to build populate one board, which you then cut in half and use as two buffers? also, would it be bad to have my buffers off board and have wires run between them and the board?



i forgot to ask this in my original post, too: which would be better for wiring stuff with, 24 gauge stranded spc, or 30 gauge solid core spc? edit - both teflon insulated

 

[n_maher]

Quote:

Originally Posted by Soymilk /img/forum/go_quote.gif is it ~$35 to build populate one board, which you then cut in half and use as two buffers?

Depending on where you are in the world (access to parts) and what parts you choose $35 should get it done pretty easily. However, if you don't already have a PCB finding one could be kind of tough. They went out of production about a year ago.

Quote:

also, would it be bad to have my buffers off board and have wires run between them and the board?

Yes, in my opinion this would be a bad idea. It might work, it might cause problems, I tend to be a bit conservative with things that can cook themselves.

Quote:

i forgot to ask this in my original post, too: which would be better for wiring stuff with, 24 gauge stranded spc, or 30 gauge solid core spc? edit - both teflon insulated

Either is find, if you can hear a difference between stranded and solid or different gages your ears are way better than mine.

 

[Soymilk]

hmm... well, as long as there isn't one that's vastly superior or inferior to the rest, i think i'll just go for the one that's easiest to acquire parts for / build. currently looks like the qrv05 is the easiest since it has a pcb available for purchase; i'll have to look at the parts lists for the sijosae, modified sijosae, and qrv05 to see if any of them have hard to find parts.

also, the sijosae and monofied sijosae db's just have a schematic available, and you use that to build it on a perf board, right?

 

[slowpogo]

Soymilk, check out this thread where I posted a ton of info about using the QRV05 in PIMETA:

http://www.head-fi.org/forums/showth...ighlight=qrv05

Maybe you'd have better luck finding the specified resistors, but I ended up ordering my parts from ELFA, a European company--and paid about $20 shipping. The parts themselves cost around $25. Good luck if you go with these, they sound great, a definite improvement over stacked 634Ps (in my opinion).

 

[Pars]

Quote:

Originally Posted by Soymilk /img/forum/go_quote.gif hmm... well, as long as there isn't one that's vastly superior or inferior to the rest, i think i'll just go for the one that's easiest to acquire parts for / build. currently looks like the qrv05 is the easiest since it has a pcb available for purchase; i'll have to look at the parts lists for the sijosae, modified sijosae, and qrv05 to see if any of them have hard to find parts. also, the sijosae and monofied sijosae db's just have a schematic available, and you use that to build it on a perf board, right?

You could build it on perfboard. Mono has a board pattern available to home etch boards for his. I've used these and prefer them to BUF634s in WB mode, including stacked. I probably have the board pattern around if you can't find it from Mono. These boards are small (around 1/2" or 12mm square) and fit the Pimeta quite nicely. I have a Browndog single opamp 8-pin DIP to dual opamp DIP adapter for a pair of AD744s and this will fit with the mono buffers.

 

[heatmizer]

This one i believe:

 

[Soymilk]

thanks for the responses. wow, that looks really straight forward (monofied image heatmizer provided), should be easy enough to perf board it. making sure though: the ones labeled JFET in that image are the 2N5486, right? also, with discrete buffers, i dont need the resistors for biasing the buffers anymore, but i still want the JFETs for class-A biasing of the opamps, right?

just curious, has anyone compared a triple diamond buffer pimeta with a ppa? either way i'll probably still build the pimeta so that i have a longer upgrade path to follow and keep me busy if i continue with this hobby

edit - the qrv05 db looks like it's a lot bigger / more complicated than the monofied sijosae buffer. why is that? here's the image i'm talking about (slowpogo's pimeta, qrv05 for l/r, buf634 ground)

note: the electrolytic caps aren't called for by the original bom, but slowpogo says it sounds much better with those instead of the smd's called for.

the monofied can fit on a 6x6 square of perf board. compared to that, the qrv05 is huge! does it offer anything extra?

 

[tomb]

Discrete buffers are like little amplifiers all their own. Amb/Steinchen's Jisbos buffer is one such case, literally. Most are made to work as an output stage in conjunction with a signal gain stage. Since they are tasked with directly driving the load, they sometimes need to handle prodigious amounts of current or slew wide swings in voltage. Often, their size and complexity is directly related to how much of either of those quantities they can manage.

 

[Zigis]

I can't find 2N5486 on elfa.se and distrelrc.com, are there replacement JFETs ?

 

[balou]

Zigis: yes, just use a JFET which has Idss current of about 2.7mA. A bit higher Idss should not be a problem (except if you want to battery power it, then the battery just won't hold as long)

 

[Soymilk]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Discrete buffers are like little amplifiers all their own. Amb/Steinchen's Jisbos buffer is one such case, literally. Most are made to work as an output stage in conjunction with a signal gain stage. Since they are tasked with directly driving the load, they sometimes need to handle prodigious amounts of current or slew wide swings in voltage. Often, their size and complexity is directly related to how much of either of those quantities they can manage.

i still don't quite understand the difference. would that make the more complex ones better overall, or would they just be able to handle a worst case scenario better?