Please tell me Nelson, are four 2SK60s in parallel are comparable to one Pass-SIT, or worthy of trying in any circuit including DEFiSIT?
Put...Put...Put
I just switched from 89dB speakers to 94dB speakers.
Using TeaBag VFET2 boards with Botte suggested changes
With CLC PSU using 25V transformer: .
If I put my ear very close to the speakers I hear a put.. put.. put. Frequency is about a beat per second. Same for both speakers. At listening position can't hear the put put put - just great sound
Repeated using 22V transformers - same thing
Switched to a different CLC PSU using 18V transformer - no put puts
Thoughts anyone???
Much appreciated and thanks
Bob
I just switched from 89dB speakers to 94dB speakers.
Using TeaBag VFET2 boards with Botte suggested changes
With CLC PSU using 25V transformer: .
If I put my ear very close to the speakers I hear a put.. put.. put. Frequency is about a beat per second. Same for both speakers. At listening position can't hear the put put put - just great sound
Repeated using 22V transformers - same thing
Switched to a different CLC PSU using 18V transformer - no put puts
Thoughts anyone???
Much appreciated and thanks
Bob
Is this still the case? (That these brackets will return to store) I notice they are no longer pictured...EEEK!
Russellc
ZM
In the 22V and 25V setups I also changed the cap bank - still the same
putt-putt
I'll check wiring today
Something with regulators ????
18VAC not enough to fire them up ????
It's irritating and hopefully doesn't damage the speakers
Thank you
aha
now you tells more ....
with PSU voltage - to have putput , try (temporary) "shorting" R20 (schm from post #11)
but!! "shorting" means not dead short (offset issue ) but just AC shorting with , say, 470uF cap , neg pole to gnd
idea is isolating FE from OS
if putput is gone , FE is culprit
is putput ( I like that worrrrrrrd!) is still there , OS is culprit
then we can go further
now you tells more ....
with PSU voltage - to have putput , try (temporary) "shorting" R20 (schm from post #11)
but!! "shorting" means not dead short (offset issue ) but just AC shorting with , say, 470uF cap , neg pole to gnd
idea is isolating FE from OS
if putput is gone , FE is culprit
is putput ( I like that worrrrrrrd!) is still there , OS is culprit
then we can go further
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then mark that amp as Tractor , and build another
ok , few things :
-that amp really needs 28V rails , no lower , or it will be starved; you can go withh lower rails , but not without excluding series regs .... and that's another amp ....... but you already know all that
- go methodically; parts are cheap while random work is not , meaning - not overly efficient ....... so - just replace all TL431 in channel , then try again , rebiasing da thing of course ; good thing - it'll already be in ballpark when you power it up
then report here
ok , few things :
-that amp really needs 28V rails , no lower , or it will be starved; you can go withh lower rails , but not without excluding series regs .... and that's another amp ....... but you already know all that
- go methodically; parts are cheap while random work is not , meaning - not overly efficient ....... so - just replace all TL431 in channel , then try again , rebiasing da thing of course ; good thing - it'll already be in ballpark when you power it up
then report here
Papa's choice.... so we can see it's possible without
I suppose he found no oscillation or ringing so he did without. Thanks ZM.
nash
Hi Bob,
Try removing the 470uF and change to 220. Then if it stops, lower c3 and c4 to 47uF. That will bring up the bias faster and keep the tl431 from oscillating.
Hope this helps,
Finally made some headway. Had it on some test speakers and everything is good.
My VFETS were not the best matches so you will see the 0.1 ohm resistors on each drain. In the end a Vgs difference of 0.4 didn't make that much current difference.
Distortion came out about .03% at 1 watt, 8ohm
My VFETS were not the best matches so you will see the 0.1 ohm resistors on each drain. In the end a Vgs difference of 0.4 didn't make that much current difference.
Distortion came out about .03% at 1 watt, 8ohm
