...is that small thingie the JFET? where does everybody get those from? Did I mis a groupbuy when I was on holiday?
Yep, they are as small as that
There is a groupbuy going on right now, so you missed only the start of it, I think. Dhole is handling EU orders, check out in the Marketplace/GB department.
(I had mine smuggled in from the states with the help of a secret agent )
Steen
Oh, I forgot the Quotebox and pasted instead
Yep, they are as small as that
There is a groupbuy going on right now, so you missed only the start of it, I think. Dhole is handling EU orders, check out in the Marketplace/GB department.(I had mine smuggled in from the states with the help of a secret agent
)Steen
Oh, I forgot the Quotebox and pasted instead
The amp is playing, but there is problems. When turning up the volume to medium level, distortion hits in. A kind of "schratchy"
crackling, distortion. Up to that point, it sounds pretty good
Its the same in both channels, except one channel distorts a bit earlier than the other. Here is the schematic as built. R4 is increased to 4,75K. I can adjust to 1,1V from sourcepin of Q1 to ground while reading 26V at the output (before the outputcap).
That is almost like the adjustment in the ZenV8 paper, so I would have thought it worked ok. I excpect the distortion has something to do with either the CCS or the railvoltage? Any help or suggestions would be greatly appreiciated
Steen
crackling, distortion. Up to that point, it sounds pretty good
Its the same in both channels, except one channel distorts a bit earlier than the other. Here is the schematic as built. R4 is increased to 4,75K. I can adjust to 1,1V from sourcepin of Q1 to ground while reading 26V at the output (before the outputcap).
That is almost like the adjustment in the ZenV8 paper, so I would have thought it worked ok. I excpect the distortion has something to do with either the CCS or the railvoltage? Any help or suggestions would be greatly appreiciated
Steen
Attachments
steenoe said:The amp is playing, but there is problems. When turning up the volume to medium level, distortion hits in. A kind of "schratchy"
crackling, distortion. Up to that point, it sounds pretty good
Its the same in both channels, except one channel distorts a bit earlier than the other. Here is the schematic as built. R4 is increased to 4,75K. I can adjust to 1,1V from sourcepin of Q1 to ground while reading 26V at the output (before the outputcap).
That is almost like the adjustment in the ZenV8 paper, so I would have thought it worked ok. I excpect the distortion has something to do with either the CCS or the railvoltage? Any help or suggestions would be greatly appreiciated
Steen
insert 47K trim in series with R2 and fiddle,but before that you can decrease R2 to 22K
also try without C4,just for comparison
have you CRO?
you can always try Aleph CCSIf you can post the DC voltages in your circuit, then I'm sure we'll find the problem in no time..
I think I might be a operating point problem...
Also the gain does seem a bit high for such a single gain stage.. so indeed lowering the feedback resistor sounds like a good idea, but this shouldn't be the heart of the problem..
goodluck,
Thijs
I think I might be a operating point problem...
Also the gain does seem a bit high for such a single gain stage.. so indeed lowering the feedback resistor sounds like a good idea, but this shouldn't be the heart of the problem..
goodluck,
Thijs
Thanks for the replies I will try and do some measurements shortly. No scope, unfortunately. As for the gain, I used the resistor values as in the ZV8.
I guess with a CCS on top of the circuit instead of the lightbulbs, the gain could be too high. The problem I had with the one channel before was the CCS not turning on properly. I had 1,5K on R4 and increased it to 4,75K. That also helped the other channel as the ditortion then hit in later and is less. So it could well be an operating point related problem. Well I think NP will post the ZV9 on PassDIY later today or tomorrow. With his comment in the beginning of this thread, maybe the answer will be in that article. Cant wait to read it
Steen
I will try and do some measurements shortly. No scope, unfortunately. As for the gain, I used the resistor values as in the ZV8. I guess with a CCS on top of the circuit instead of the lightbulbs, the gain could be too high. The problem I had with the one channel before was the CCS not turning on properly. I had 1,5K on R4 and increased it to 4,75K. That also helped the other channel as the ditortion then hit in later and is less. So it could well be an operating point related problem. Well I think NP will post the ZV9 on PassDIY later today or tomorrow. With his comment in the beginning of this thread, maybe the answer will be in that article. Cant wait to read it
Steen
Dooh, how stupid of me! Well, I guess I was just too focused on the 1,1V figure across the Jfet as described in the ZV8 paper!! I will try to adjust for half the supply voltage on the output!!! Just as I thought. I better start listening to my guts. I think the amp will play music, when its adjusted for symmetric outputswing.
As I adjusted the amp for 26V at the output it will have an outputswing of about +6/-26V
Isnt that just to plain ...... fill in the dots as you please The Zv9 paper just hints that fact, indeed
I will keep you posted, indeed.
Steen
As I adjusted the amp for 26V at the output it will have an outputswing of about +6/-26V
Isnt that just to plain ...... fill in the dots as you please The Zv9 paper just hints that fact, indeed I will keep you posted, indeed.Steen
The adjustment was in fact the problem. (Can't believe I did that)
The amp is now correctly adjusted (I had to change the value of R9 to 22k ,to obtaine 16V (half supply voltage) at the output (before the cap!) The amp behaves just as it is supposed to do,
and believe me or not; it sounds just wonderfull
I am off to have a good listen to my first J-fet poweramp
Steen
The amp is now correctly adjusted (I had to change the value of R9 to 22k ,to obtaine 16V (half supply voltage) at the output (before the cap!) The amp behaves just as it is supposed to do,
and believe me or not; it sounds just wonderfull
I am off to have a good listen to my first J-fet poweramp
Steen
steenoe said:The adjustment was in fact the problem. (Can't believe I did that)
The amp is now correctly adjusted (I had to change the value of R9 to 22k ,to obtaine 16V (half supply voltage) at the output (before the cap!) The amp behaves just as it is supposed to do,
and believe me or not; it sounds just wonderfull
I am off to have a good listen to my first J-fet poweramp
Steen
hehe-this time I was faster than ya -if Babbelfish counts ...
Congratulations
The Babbelfish counts allright Mighty fine job you did with that It is a pretty good feeling that my amp works and sound great too. I am sure these Jfet amps are headed for a magnificent future. The sound of it is really nice.
Next up is a fullbreed ZenV9
The Aleph CCS would be a wellcome addition.Steen
steenoe said:Congratulations
It is a pretty good feeling that my amp works and sound great too. I am sure these Jfet amps are headed for a magnificent future. The sound of it is really nice.
Next up is a fullbreed ZenV9
Steen
next one will be full breed Babbelfish J squared......
P Jfet LTP on input ,and cascode Jfet in output,with Aleph CCS
I am pretty amazed with the sound of this J-fet amp. Its quite addictive to say the least. I have connected it to my main system and the synergy with the Twisted BosoZ is just fantastic
The sound is very pleasant with much detail. It sounds better than the other Zen-amps I have build for sure. This might be the way to go Thanks, Mr Pass for sharing the ZenV8 and V9 with us Diy'ers.
Steen
The sound is very pleasant with much detail. It sounds better than the other Zen-amps I have build for sure. This might be the way to go
Thanks, Mr Pass for sharing the ZenV8 and V9 with us Diy'ers.Steen
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