Hi Guys,
I'm making an integrated amplifier out of some lm3876 gainclones and a yet to be decided upon tube preamp. The preamp board will be wired directly to the power amp boards. My question is whether I need coupling caps at both ends? That is to say do I need both the (say) 2.2uf coupling cap at the input of the lm3876, as well as the (say) 1uf coupling cap at the output of a 6SN7.
Does the proximity of the 2 stages and the length of wire runs have a large impact upon the answer? That is to say, would the answer be different if I was point to point wiring the whole system. Lets say the 2 stages could be placed the close enough together, that one could solder the 1uf coupling cap from the 6SN7 socket, directly onto resistor at the input of the lm3876.
Would one still need an separate input cap and output cap or would one simply use a single interstage(?) cap? The gainclone kits are from Jaycar here in NZ and use on the old Silicon chip March 94' circuit. Dual mono, regulated and snubberised power supplies ala Carlos Marchado found on Decibel Dungeon.
The preamp is still an open question. I'm leaning towards 6SN7s because I use them in another preamp but am tempted by some of the hilariously low prices available on other tube types like say the 6n1 or 6n3. Toplogy goes around in circles.
I'm making an integrated amplifier out of some lm3876 gainclones and a yet to be decided upon tube preamp. The preamp board will be wired directly to the power amp boards. My question is whether I need coupling caps at both ends? That is to say do I need both the (say) 2.2uf coupling cap at the input of the lm3876, as well as the (say) 1uf coupling cap at the output of a 6SN7.
Does the proximity of the 2 stages and the length of wire runs have a large impact upon the answer? That is to say, would the answer be different if I was point to point wiring the whole system. Lets say the 2 stages could be placed the close enough together, that one could solder the 1uf coupling cap from the 6SN7 socket, directly onto resistor at the input of the lm3876.
Would one still need an separate input cap and output cap or would one simply use a single interstage(?) cap? The gainclone kits are from Jaycar here in NZ and use on the old Silicon chip March 94' circuit. Dual mono, regulated and snubberised power supplies ala Carlos Marchado found on Decibel Dungeon.
The preamp is still an open question. I'm leaning towards 6SN7s because I use them in another preamp but am tempted by some of the hilariously low prices available on other tube types like say the 6n1 or 6n3. Toplogy goes around in circles.
Hi
if you are going to put preamp and LM chip in the same chassis, you can indeed keep one cap only.
I am just thinking, and let someone else have a look at it as well: if you use non delayed SS power supplies for everything, the B+ for the output tube will be present "at once". This shift from 0V to B+ will get through the cap and into the LM chip, and cause a dangerously high pop at turn on.
if you are going to put preamp and LM chip in the same chassis, you can indeed keep one cap only.
I am just thinking, and let someone else have a look at it as well: if you use non delayed SS power supplies for everything, the B+ for the output tube will be present "at once". This shift from 0V to B+ will get through the cap and into the LM chip, and cause a dangerously high pop at turn on.
Hi Erik,
Thanks for the answer.
Regarding a soft start. Is there any danger to the amp circuits from the instant b+ or is it solely an issue of dc at the speaker?
Could I get around the problem by simply putting my b+ transformer(s) on a separate power switch to everything else and simply not turn on the b* for 20s?
Thanks for the answer.
Regarding a soft start. Is there any danger to the amp circuits from the instant b+ or is it solely an issue of dc at the speaker?
Could I get around the problem by simply putting my b+ transformer(s) on a separate power switch to everything else and simply not turn on the b* for 20s?
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