6V6 line preamp

[DimZ]

I'll check this later and report back ...

 

[Salas]

Your DC conditions look spot on by the way.

 

[DimZ]

dmm at DCmV with probes touching = zero ..
removed the teflon cap, no difference ... still variable indication at the DCmV position ..

guess I have to recheck the rca's/pot grounding scheme ... which is pretty much as the one at post #1064

 

[Salas]

Some DC settling during first minutes reflecting to the output caps when not connected to lower load as a main amp probably. Mine does the same. No worries I guess. Watch it over a 50 to 100K pseudo output load simulating an amp over 15 mins.

 

[DimZ]

it is strange that it is constantly changing though ...

tomorrow I'll give it a try with a gc and some cheap speakers ...

 

[Salas]

It would take a scope to make sure there is no waveform, but the norm is to go up and then go low over some minutes if it is just reflecting a DC drift as the various circuit blocks and supply warm up and settle.

 

[DimZ]

if testing with amp-speakers wont work I'll take it to someone with proper instruments to work this out ..

 

[Salas]

I am not easily worried there is much chance its about something peculiar, its a non loop feedback very simple circuit to do particular funnies. With electronics and various layouts you never know on the other hand, but no, slim chance.

 

[DimZ]

oops .....

it seems that when I changed the sockets and resoldered the parts yesterday I took the output before the 5k anode reistor and not after ...

will fix that tomorrow ...

 

[DimZ]

false alarm, the output was after the resistor ...

so, I took off the pot and done the wiring again ... and ... bingo !!!


it's dead quite and it sounds wonderful ...

 

[DimZ]

setup is netbook/foobar/m2tech/buffaloII/6v6 ....
with my 2.5 way 92db speakers (horns moved to another room for the holidays) ...

I listened it with zenV4 and f5, with both it sounded excellent, esp with zen cause zen needs the extra dbs (I was listening to it with dcb1) ...

Nick ... thank you for your design and for the unique power supply and all the members who contributed to it ....

now its time to play with some rectifier tubes and output caps ...

 

[Salas]

Looks good. What is the rest of the system?

P.S. Ok we cross posted, you are welcome.

 

[Salas]

Using a 50K pot?

 

[DimZ]

I listen to flac's from a netbook (mostly 192/24), using foobar and hiface m2tech, then is the bufalloII dac ...
I havent listen through my cd player yet, and I dont have a turntable (tho I have about 500 vinyl records ....)
main speakers are 2w , with deltalite 2510ii in mltl and bc de250 in tractrix horns / x-over based on zilch's econowave work , for the holidays I have taken them to another room and I am using my artemis


yes I use a 50k pot, placed in the middle is allready too loud ....

 

[Salas]

Is it easy to push the column speaker for slam with a Zen or an F5? I guess that the line gain came up handy.

 

[DimZ]

yeap !
they are 91-92db, so the gain was much appreciated ..

the horns are 95-96db ... still some extra gain will be nice to have there too ....

 

[Salas]

With such low gain main amps yes, gain aids their dynamics even on sensitive speakers. There was a very easy to understand article by member Pano about gain distribution in the whole chain. A rather underestimated thing in home audio but every one involved in live and recording systems knows its of cornerstone importance.

 

[Salas]

*Here is the link: http://www.diyaudio.com/forums/diyaudio-com-articles/186018-what-gain-structure.html

 

[DimZ]

yes, I have read that article, not long ago ...

btw pot is a cheap one, have tried it in dcb1 and it was fine for the job to start wth, later I replaced it with a khozmo one which was much much better of course ...
I probably put a khozmo in this line stage too - with z-foils this time ....

 

[Salas]

Khozmo has 25K too, hmm, could you try with 20-25K too to know what value you like best in your system and sources so to buy optimally when you will splash out for a posh pot?