DIY biamp 6-24 crossover

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edwinjones4

Member
Joined 2021
edwinjones4 said:
Surprisingly, I got it to work the first time. 6L6's build guide was super helpful and much appreciated. Also, I used Mr. Pass' recommendation (Post #230) to use Digikey part 116-87-210-41-006101, which made for easy swapping of the WIMA caps.

Does anyone have a .cad drawing of the backplate for the 2U galaxy 230x230mm chassis they be willing to share? I want something similar to the ACN backplate silkscreen, so can order a custom CNC'd backplate from the diyaudio store.

Thanks!
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.dwg*
 
E

euro21

Member
Joined 2004
Paid Member
DualTriode said:
Hello,

Bottom line, I do not want to hear noise or distortion.

To hear noise or distortion when the music is playing either or both will need to be pretty extreme. The program material does significant masking.

Noise is the worst. The program masks distortion and there is no distortion produced in the silence between the tracks.

Hum, buzz or hiss between the tracks is my pet peeve.

For high sensitivity Compression Driver wave-guide tweeters, with an active crossover I pad the tweeter amplifier output to operate at several watts. Picture the typical THD+N vs. power output plot. The THD+N (SINAD) improves drastically as the power output increases to 3, 4 or 5 watts.

My concern is how much noise does the J113 Jfet and bias resistor make?

Perhaps in this buffer / crossover circuit with little or no gain the noise will not be problematic?

I am thinking about purchasing one of the basic kits and installing some sockets to allow swapping out different Jfets and bias resistors to make some measurements.

Thanks DT
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Are you sure, that your PSU not injecting this noise to the circuit via VREF?
 
D

DualTriode

Member
Joined 2009
euro21 said:
Are you sure, that your PSU not injecting this noise to the circuit via VREF?
Click to expand...

Hello,

You could be easily correct; the Power Supply could be guiltily. These JFET dodads do not excel at PSRR.

That is something that needs to be checked.

Noise can be checked on the analyzer.

The One and Only recommends a TRIAD wall wart and filter circuit that I will use.



I received the 6-24 basic PCB and J113’s from the DiyAudio store a couple of days ago. Like other builders I am installing sockets to roll JFETs, resistors and capacitors.

I also bought a couple of soldeable bread boards to assemble different JFET basic buffers to test for THD+N, then short the inputs and test for noise alone.

Thanks DT
 
Nelson Pass

Nelson Pass

The one and only
Joined 2001
Paid Member
Offhand, I think the psrr of the jfets are the not problem - all devices have some flaw in this regard.

If you are rolling jfets for this, you might as well go straight to the usual Toshiba or LS parts and get it over with.

If you are up for surface mount, then the 2sj209's as well.

The j111/113 and their complements are very serviceable for this project and other buffers, and I chose them for cost/availability and because they deliver a good sonic signature, even if the THD figure is higher at <.01% @ 1V.

:cheers:
 
D

DualTriode

Member
Joined 2009
Nelson,

Thank you, I only mean to be respectful. I study this stuff for fun and hobby, people come before technology.

In terms of PSRR JFETs are no more a problem than vacuum tubes. It is more the circuit type than the type of device that is sensitive to power supply noise.

There are bins full of parts on my shelves including vacuum tubes and JFETs waiting for a test drive. Toshiba K170’s and J74’s included.

I am sure that the PF5102, J111 and J113 family will be just fine. I just want to poke and measure some for the fun of it.

I am expecting the TRIAD switching power supplies to generate much less mains frequency 60hZ, 120hZ, 180hZ and on up harmonic series than the full bridge rectified power supplies do.

Thanks DT
 
jamayfie

jamayfie

Member
Joined 2006
Paid Member
edwinjones4 said:
Does anyone have a .cad drawing of the backplate for the 2U galaxy 230x230mm chassis they be willing to share? I want something similar to the ACN backplate silkscreen, so can order a custom CNC'd backplate from the diyaudio store.
Click to expand...
Hifi2000/Modushop had the ACN chassis listed for sale until last week. I'm kicking myself for not buying sooner, but they are no longer listed. However, member Gianluca runs the shop, is helpful, and willing to answer questions. I don't know if he can share the silkscreen designed by the DIYAudio store, but perhaps he can comment on the ACN chassis.
 
D

DualTriode

Member
Joined 2009
Hello,

I am doing a bit of DIY.

I want to test and measure some different Jfets and bias resistor values. I want to use the power supply on the kit PCB.

I have a couple of related questions:

On the kit PCB there are a couple of bypass capacitors on the +24V power supply rail. Are these capacitors intended to be the same as the other capacitors also labeled “C”. Often we see ceramic XR7 type capacitors used to bypass the voltage rails. What is the thinking using the same “C” capacitors to by-pass the rails?

The circuit PDF drawing shows a .1uf non-electrolytic capacitor used in the input buffers. The PCB has a place for a 10uf electrolytic capacitor instead, What is the thinking?

Thanks DT
 
C

cucuclock

Member
Joined 2012
edwinjones4 said:
Surprisingly, I got it to work the first time. 6L6's build guide was super helpful and much appreciated. Also, I used Mr. Pass' recommendation (Post #230) to use Digikey part 116-87-210-41-006101, which made for easy swapping of the WIMA caps.

Does anyone have a .cad drawing of the backplate for the 2U galaxy 230x230mm chassis they be willing to share? I want something similar to the ACN backplate silkscreen, so can order a custom CNC'd backplate from the diyaudio store.

Thanks!
Click to expand...
Hello, please someone can point me on the crossover 6L6's build guide?I'm struggling to find it. Thank you
 
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