hershann said:
ha!
someone did the math for me. also, isn't 47k for F4 pretty much arbitrary? ya think 3.3uF is ok for outputs? I found some 3uF polystyrene and foils that cost a king's ransom that look tasty if I can get them to work?
edit:
I'm probably doomed to my 2 diy stand mounts for a while and they won't be going anywhere that low. One is a Skanning 15 cm and the other a Morel MW142 (wannabe dynaudio). The one that uses the Morel has -3 dB at 40 Hz and the Skanning isn't finished, but it has a fs of 48 hz.... so....
Zen Mod said:
ah ok. well, I think I have that one figured out (output cap in the pumpkin). what about the case where I have a source and want to see how low I can go with the coupling cap and assume I'm using papa's lightspeed linked above and the pumpkin? So, I have Zout of the source and the Zin and Zout of attenuator and then Zin of the Pumpkin?
luvdunhill said:
ah ok. well, I think I have that one figured out (output cap in the pumpkin). what about the case where I have a source and want to see how low I can go with the coupling cap and assume I'm using papa's lightspeed linked above and the pumpkin? So, I have Zout of the source and the Zin and Zout of attenuator and then Zin of the Pumpkin?
thing is simple when you are in world of brute force ......... ie. - having small enough output impedance of previous stage ;
in case that you have B1 looking at some amp - you use only input impedance of amp for cap calculus ;
same with
- to calculate his own coupling caps , you use only imput impedance of amp
Zen Mod said:
thing is simple when you are in world of brute force ......... ie. - having small enough output impedance of previous stage ;
in case that you have B1 looking at some amp - you use only input impedance of amp for cap calculus ;
same with
right, but what about when calculating the coupling caps for the source? so source -> papa's attenuator -> pumpkin
luvdunhill said:
with B1 - taking in account that Papa use 25K as pot value
with Papa's Lightspeed buffer version - taking in account that two anti-series connected LDRs never falls bellow some 10K or so ........ ;
in both cases you need output impedance of preceding stage ( source ) not greater than 1K , and you can slip it from equations ;
if source output impedance is greater than that - you're in trouble ..... needing additional buffer stage
Zen Mod said:
Here's the lightspeed schematic:
http://www.diyaudio.com/forums/attachment.php?s=&postid=1521766&stamp=1211904694
so, let's take 2 examples. First is Papa's Pearl which is simply 10u cap followed by 100k shunt. So, we have 100k in parallel with the lightspeed that can vary to 10k that's in parallel with the Pumpkin, which has 10k as R1 (do I have to worry about R2 and R27?). So, do I have 100k (Pearl) || 10k (Lightspeed) || 10k (Pumpkin) = 4762 ohms, and then F = 1/(2 x pi x R x C) so, assume C is 10uF we have F = 3.36 Hz. Since 10k is the highest that the lightspeed can be, then this is the worse-case scenario and for < 10k, we will have a lower corner frequency.
Now, also Papa's Ono which has a 10u cap followed by a 100k + 10n cap to shunt followed by 100R resistor for positive output and 10u cap followed by 100k + 680p to shunt for negative output. I'm not sure what to do with the series resistance, but if I only have to deal with 100k shunt then the example is the same as above (as the 10n and 680p are for ultrasonic filtering).
The rest of my sources are DCcoupled, and they will have output impedance of less than 1k. I just want to know how small of coupling caps I can get away with these 2 phono preamps
mpmarino said:OT
Thinking about an open Baffle -
Alpha 8 or Beta 8 for widerange driver?
or?........
me thinks Alpha .......... but you can check curves by your self ........
just because I didn't compare them directly .
anyway - I have more xperience with alpha 6 , than with any of these 8"
edit:
tried tested recipe :
Alpha 15 - two pieces per side
Alpha 6
APT80
xover :
for Alpha 15 - 150Hz/6db/oct + Boucherot ( cure for peak at 2+KHz)
Alpha 6 - just 6db/oct HP at 350Hz , +phase plug ( EnABLE still not tested ;( )
APT80 - just 6db/oct HP at 12-14KHz + L Pad
that's *******' cheap ........... at my place ~ 300E for spks
I'm thinkin even cheaper -
I have ~20 of these peerless. I know nothing about them (I know they are 4r and 8" across ).... and probably ~88db.
6 per side series parallel for 2.6666666667 ohms.
Toss in an 8" wideband and an APT80(?) or something. Just wondered if alpha or beta 8 has been heard by you guys - the graphs don't always tell the whole story
I have ~20 of these peerless. I know nothing about them (I know they are 4r and 8" across
).... and probably ~88db. 6 per side series parallel for 2.6666666667 ohms
.Toss in an 8" wideband and an APT80(?) or something. Just wondered if alpha or beta 8 has been heard by you guys - the graphs don't always tell the whole story
