Sebastian,
I've been on some other projects but now back on it, reviewed everything up to this point for errors oversights and found none.
So be patient , have you tested anything like this before?
(Note: The 1k grid resistor also limits forward grid current in addition to kill oscillation if any tendencies )
Regards
Bruce
I've been on some other projects but now back on it, reviewed everything up to this point for errors oversights and found none.
So be patient , have you tested anything like this before?
(Note: The 1k grid resistor also limits forward grid current in addition to kill oscillation if any tendencies )
Regards
Bruce
6DJ8 Unity gain non inverting
Trying to get back into it. I had a 6DJ8 and thought the specs looked interesting so here is a series of tests. This group is unity non inverting.
The readme file has hardware info. The circuit is identical to the one Sebastian drew but a 6DJ8 is used.
Interesting that I attempted this time to use one of those low cost switchers on ebay for 6VDC heater. They are verrrry noisy!
Went back to my low noise dc supply. Its a switcher but has special filters for for use with sensitive radio receivers.
My test board is not yet assembled so these two test runs are on perf board.
The readme file has hardware info.
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Trying to get back into it. I had a 6DJ8 and thought the specs looked interesting so here is a series of tests. This group is unity non inverting.
The readme file has hardware info. The circuit is identical to the one Sebastian drew but a 6DJ8 is used.
Interesting that I attempted this time to use one of those low cost switchers on ebay for 6VDC heater. They are verrrry noisy!
Went back to my low noise dc supply. Its a switcher but has special filters for for use with sensitive radio receivers.
My test board is not yet assembled so these two test runs are on perf board.
The readme file has hardware info.
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Attachments
Here are tests using inverting gain of 4.7
Note the sight increase in thd is mostly 2nd.
Still remaining are test board assembly, CC diode spreadsheet, PCB fab using new CAD (dropped Eagle) and same project but repeated using grounded grid topology.
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Note the sight increase in thd is mostly 2nd.
Still remaining are test board assembly, CC diode spreadsheet, PCB fab using new CAD (dropped Eagle) and same project but repeated using grounded grid topology.
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Attachments
I ordered some for evaluation.
(automotive group)
OPA1612AQDRQ1 soic only
will receive conduction heat due to physical close quarters.
High temperature operation 85c , functional to 125C.
Hi drive similar to ne5532 plus swings closer to rail.
Power / distortion and bandwidth improved.
Expensive $$ about 7.00 but it's worth it.
OPA1612-Q1 Application notes,More literatur, Blogs
(automotive group)
OPA1612AQDRQ1 soic only
will receive conduction heat due to physical close quarters.
High temperature operation 85c , functional to 125C.
Hi drive similar to ne5532 plus swings closer to rail.
Power / distortion and bandwidth improved.
Expensive $$ about 7.00 but it's worth it.
OPA1612-Q1 Application notes,More literatur, Blogs
One more note: My ur22mkii indicates .0015% thd looping back to itself.
So as tested on the two circuits .001% was added with the unity gain and .0015 with inv gain configuration.
As I mentioned earlier not really going for lowest thd but rather good sound.
So as tested on the two circuits .001% was added with the unity gain and .0015 with inv gain configuration.
As I mentioned earlier not really going for lowest thd but rather good sound.
This pic shows general idea, if possible to make pcb dual use.
Stuff with the single opamp package and miniature triode tube footprint for 990 package.
Or stuff with dual opamp package and 9 pin dual triode with dip8 male header.
May have to use 4 layer board but that's better anyway for thermals.
Stuff with the single opamp package and miniature triode tube footprint for 990 package.
Or stuff with dual opamp package and 9 pin dual triode with dip8 male header.
May have to use 4 layer board but that's better anyway for thermals.
Attachments
E452 is a Semitec current regulator, 4.5ma.
Here are the eagle v5 files as of today. I have not checked the board 100% , but after will get some Purple boards fab.
Its 2 layer, 1" X 1".
The odd soic pin 8 is for a lower Z, since there are no bypass caps on board.
The compensation C can be omitted, stuffed with fixed value or variable smd or 5mm through-hole varicap.
The 'board' shown is made from balsa wood and some throw down packages. Its just a reality check for clearance.
zip and some pics here.
Any opinions on the purple boards?
OSH Park ~
Here are the eagle v5 files as of today. I have not checked the board 100% , but after will get some Purple boards fab.
Its 2 layer, 1" X 1".
The odd soic pin 8 is for a lower Z, since there are no bypass caps on board.
The compensation C can be omitted, stuffed with fixed value or variable smd or 5mm through-hole varicap.
The 'board' shown is made from balsa wood and some throw down packages. Its just a reality check for clearance.
zip and some pics here.
Any opinions on the purple boards?
OSH Park ~
Attachments
More on current regulators. These are fast , I was not really expecting.
I have tested resistor loading and parallel jfets which also work excellent.
But would take up a lot of space. The semitec parts also rated for 100v vs 30-40v jfets.
So the CRD seems to be best choice.
They are somewhat expensive.
E-452 Semitec | Mouser
Attachments
Cleaned up some pads, tweeked Compx path and reduced number of drills.
Also removed thermals. (Thermals are bad- only helps production) , yes the board must be heated prior to soldering.
So today I think its going to fab.
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Also removed thermals. (Thermals are bad- only helps production) , yes the board must be heated prior to soldering.
So today I think its going to fab.
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Attachments
Last edited:
Will listen to it for a few days and relish the fun. So far no issues.
Its a clamshell so soldering is more difficult and a specific assy order must be followed.
Got tired of taking my DH100 apart so using this $9 preamp tone board for listening.
The power amp is a SAE 2200.
Here are the Gerbers to look at until I finish all the testing. I hate to take it down for the THD measurements.
First tracks used....
#1
Cecilia Bartoli: (Opera)
Mozart: Così Fan Tutte, K 588
#2
Henry Qualls: (Texas Blues)
Shotgun Blues
#3
Red Bar Jazz Band Live Jazz with Chuck Schwartz
Bye Bye Blackbird
Its a clamshell so soldering is more difficult and a specific assy order must be followed.
Got tired of taking my DH100 apart so using this $9 preamp tone board for listening.
The power amp is a SAE 2200.
Here are the Gerbers to look at until I finish all the testing. I hate to take it down for the THD measurements.
First tracks used....
#1
Cecilia Bartoli: (Opera)
Mozart: Così Fan Tutte, K 588
#2
Henry Qualls: (Texas Blues)
Shotgun Blues
#3
Red Bar Jazz Band Live Jazz with Chuck Schwartz
Bye Bye Blackbird
Attachments
It's now set up as a shared project.
You can order the boards , looks like $5.
OSH Park ~
My user name is jfetter.
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You can order the boards , looks like $5.
OSH Park ~
My user name is jfetter.
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