In addition to changing the caps, I would still be sure to check solder joints on your connectors. If you had a loud buzz when you hooked everything up, it could very easily be a bad solder joint. I personally hate soldering RCA's and the like and have had the trouble before. Sometimes just pressing on the wire would stop it. The fact that the second channel was fine, increases my suspicions.
Absolutely, Buzz. Same thoughts here. I haven't soldered some of metal lugs, exactly on the buzzing channel. They might be a problem. Also signal cabling etc etc etc. I will look into all this first.
It's a hassle to dismantle and assemble the chassis, but there's no other way. Having said that, what about removing bypass caps, so I won't have to do it again?
It's a hassle to dismantle and assemble the chassis, but there's no other way. Having said that, what about removing bypass caps, so I won't have to do it again?
Yeah - but with a CFP o/p.
In spice I'm getting 10 - 15m ohm o/p between 10hz and 100Khz @ 1A depending on how it's configured
Also got a global FB design that I'll be building next that gives more like 1m ohm between 10hz and 50Khz in spice
Should being firing the 1st one up in about a week
edit: To clarify, those impedances quoted were without any o/p capacitance - was purely checking the regulator performance.
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Sonny, Could you give a brief description of how the higher voltage impacts on the sound quality - this topic is very interesting to me right now.
Not a day without a trouble. Changed C12 & C13, tightened all connectors. One channel starts too hot. With all the trimmers set to 0, it has a bias at 160 mV, 9V across J7 and J8. At first power up it was shooting over 250 mV and crickey hot after one minute, that is with 18V across J7 & J8. Could some part caught static while changing caps and soldering? Don't know what to think.
Hi Mike.
In the TSSA design we use JFET as cascode for the current source.
Before reading below, THE TSSA DOES SOUND GOOD but the Jfet has a few drawbacks:
Pros:
1) Easy to implement a "high impedance" current source.
2) Few components
Cons:
1) The Fets available is close to be obsoleted IMO 1 - 2 years time, you can get them from other companies specializing in Fets, but they are not as cheap as they should be.
2) Noise voltage on many Fets available is relatively high below 1KHz.
3) There is no complementary types available
4) For the input pair, the jfet will modulate the voltage across the bipolar input pair.
5) Difficult to get fet above 35V, and then you add a series resistor to get to the higher voltage....
5a) a resistor is noisy if not metal foil.
---------------------------------
So my approach is to use a hawksford cascode instead... Of course, it has to be tested how it sounds.
But i do not have noise problems with hawksford cascodes in my other designs...
---------------------------------
I will also try to get rid of the ac couplings capacitors.
---------------------------------
I expect a lot from those mods..
In the TSSA design we use JFET as cascode for the current source.
Before reading below, THE TSSA DOES SOUND GOOD but the Jfet has a few drawbacks:
Pros:
1) Easy to implement a "high impedance" current source.
2) Few components
Cons:
1) The Fets available is close to be obsoleted IMO 1 - 2 years time, you can get them from other companies specializing in Fets, but they are not as cheap as they should be.
2) Noise voltage on many Fets available is relatively high below 1KHz.
3) There is no complementary types available
4) For the input pair, the jfet will modulate the voltage across the bipolar input pair.
5) Difficult to get fet above 35V, and then you add a series resistor to get to the higher voltage....
5a) a resistor is noisy if not metal foil.
---------------------------------
So my approach is to use a hawksford cascode instead... Of course, it has to be tested how it sounds.
But i do not have noise problems with hawksford cascodes in my other designs...
---------------------------------
I will also try to get rid of the ac couplings capacitors.
---------------------------------
I expect a lot from those mods..
Thanks for the very comprehensive explanations sonny - much more than I expected - but very interesting.
I look forward to see the upgraded design.
I stiil have so much to try on my amp - must work faster !
cheers
mike
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