I have 16 (per channel.) Sounds like four would be the way to go. I might be able to parallel two on top and two on bottom of the board. Any comments on the source resistance? I also noticed the input (AC) coupling is different compared to my schematic. Is that a requirement based on a JFET vs MOSFET front end?
What is the limiting factor on the jfets? It looks like the 74s are rated for twice as much power dissipation at 400mW than the 109s. As such, perhaps using two vs four might be ok?
Hi,
the limiting factor is the current they can deliver. With only 10mA total bias this is only half the current the standard 9610´s can deliver.
This will cause bandwith limiting.
There are a few more reasons why two pairs is better. You can find them in the thread I posted somewhere above.
William
the limiting factor is the current they can deliver. With only 10mA total bias this is only half the current the standard 9610´s can deliver.
This will cause bandwith limiting.
There are a few more reasons why two pairs is better. You can find them in the thread I posted somewhere above.
William
If I can get two pairs, would I stick with the 15R source resistors as well or eliminate as Graeme has done?
Hi,
I only used the source resistors (in form of a pot) to get my relative DC offset low enough. I had not enough 2SJ74 to find good enough matches.
William
I only used the source resistors (in form of a pot) to get my relative DC offset low enough. I had not enough 2SJ74 to find good enough matches.
William
Mine are matched with with 0.5mA. I think I will try the MOSFETS from Graeme (thanks again Graeme) since I know that will work fine and then consider upgrading to JFETs later. Besides, that will give me a chance to hear for myself what the difference is.
Plus, tinkering is fun!
Plus, tinkering is fun!
Does anyone have alpeh-X boards for sale ?
I have bought a guys big monoblock DIY Alpeh X amps, but his pcb is a little confusing, it goes not use the component numbers on the original schematic and the track width is somewhat narrow. it's easier for me to do debugging when i can easily correlate the components on the pcb with the schematic.
I have bought a guys big monoblock DIY Alpeh X amps, but his pcb is a little confusing, it goes not use the component numbers on the original schematic and the track width is somewhat narrow. it's easier for me to do debugging when i can easily correlate the components on the pcb with the schematic.
PCB's?
Hi there,
I am also looking for a couple of PCB's for the "low" powered version of Grey!
Anybody able to help me out here?
Cheers!
Hi there,
I am also looking for a couple of PCB's for the "low" powered version of Grey!
Anybody able to help me out here?
Cheers!
Has anyone seen or heard from Ian MacMillian recently?
(I have not been around much in the past 2 years)
Macka
(I have not been around much in the past 2 years)
Macka
I'm still around, but like you it would seem, have not been around much recently. I'm still pursuing this hobby of ours but other projects are currently competing for my attention.
Ian
input caps
Hi guys,
I've read several threads mentioning the input caps when using rca. However, I am a bit lost as to why the short between -in and shd/gnd should be made before the caps. This bypassess the cap on the shd/gnd. Is this because if possible gnd currents injecting back into -in?
Cheers
Hi guys,
I've read several threads mentioning the input caps when using rca. However, I am a bit lost as to why the short between -in and shd/gnd should be made before the caps. This bypassess the cap on the shd/gnd. Is this because if possible gnd currents injecting back into -in?
Cheers
Here you get good boards. I used the same for my Aleph-X:
SE MOSFET Full Balanced 100W Class A Amplifier PCB | eBay