6V6 line preamp

[buzzforb]

OK thanks.

 

[Salas]

AC voltage on the heaters for the 6v6 was inho the way to go. I tried various DC set-ups including a SSLVR and all of them sounded dead to me. So I am back to a simple tranny and a resistor to keep the voltage down to 6.1V. It is a matter of opinion though.
No Hum.

Did you also try the 317 chip current source heater like in the original schematic by the way?

 

[SGregory]

Yes, I did try it. If I recall correctly, it was a similar perception. Kind of dull, or missing the life. Hard to describe exactly. In truth none sounded really bad, just prefered the AC set-up better.

 

[Salas]

Is there there a bit different harmonic content in THD measurement when with AC heating?

 

[SGregory]

This is what I have. I don't recall why I stopped testing it as I don't really like the trash that I see with the 60Hz harmonics. I know I had a significant reduction in 60,120,and 180Hz with DC.

Regarding the 1kHz signal and harmonics, virtually identical or at least no difference I could see. +/- 1 or 2dB

I recorded this almost a year ago, 30Dec11, so I am a little sketchy on all the details, but I know I had better traces for the AC filament

 

[Salas]

So red is some time not your best AC heating, blue is DC heating. 1kHz harmonics have a nice fall scale.

 

[buzzforb]

Salas. Did you try lifted AC heater.

 

[SGregory]

Yes red is a not so good AC spectrum. If you recall I was having a bit of an issue back then with ground loops on my test bench. I know I have a clean one somewhere in my files, but that was a computer ago. The 60,120, and 180 Hz peaks were about the same magnitude however.

 

[TonyTecson]

i heard reports by some local diy'ers that using a CMC on the ac filament yielded improvement, the choke is a ferite type sized to handle the current required...

 

[Salas]

Salas. Did you try lifted AC heater.

Not in this one. DC voltage source and DC current source. I preferred the later.

 

[cjkpkg]

OK,

FINALLY have had a chance to finish this pre correctly...sort of...

Running a broskie PS-3 - SS B+ and regulated SS heaters.

B+ is 330
Cathodes see 15V
Kiwame resistors
Silmic cathode cap
Russian 6П6С

All values per schematic

I look forward to giving this some serious listening. I have reverted back hard to the Aikido but this pre now shows promise...I think that it is just as quiet as the aikdio...this is impressive to me.

 

[Salas]

Congratulations. Drop as a note as to what you have learned after some run in.

 

[cjkpkg]

Well as it turns out in switching around my sources that when I am using my satellite TV as the source - music channels - I have a faint buzzz. Not like before but there just the same.

Turntable? - no buzzz
Ipod? - no buzzz
Satellite? buzzzzzzzzzzzz

The turntable and the ipod are absolutely dead silent.

So this leads me to addressing the satellite input. Basically i have a homemade cable which runs about 30 feet from where the satellite receiver is to the other room where the amps are. This long run of cable must be the culprit. Step 1 was initiated today in the form of a pair of Edcor matching transformers. As much as I would have like some Jensen iron here I could not justify spending upwards of $200 when the Edcors are $10 each. Certainly worth a try to see if the buzz is tamed at all or for good.

Depending on the result I may splurge for the Jensens.

 

[stajo]

Well as it turns out in switching around my sources that when I am using my satellite TV as the source - music channels - I have a faint buzzz. Not like before but there just the same.

Turntable? - no buzzz
Ipod? - no buzzz
Satellite? buzzzzzzzzzzzz

The turntable and the ipod are absolutely dead silent.

So this leads me to addressing the satellite input. Basically i have a homemade cable which runs about 30 feet from where the satellite receiver is to the other room where the amps are. This long run of cable must be the culprit. Step 1 was initiated today in the form of a pair of Edcor matching transformers. As much as I would have like some Jensen iron here I could not justify spending upwards of $200 when the Edcors are $10 each. Certainly worth a try to see if the buzz is tamed at all or for good.

Depending on the result I may splurge for the Jensens.

Try a ground isolator on the tv signal cable.

/Staffan

 

[6L6]

Hello again!

My project has been on hold awaiting a SSHV2 group buy... It is done, and I have my shunt regulator. Hooray!

Does anybody have any specific information as how to implement it into this 6V6 circuit?

Thanks in advance!

 

[buzzforb]

It was a breeze. Well, not really. At first I had my tubes singing, but switched snsing wires to correct palce and worked fine. That was using my home etched PCB and not quality made board. You will love it.

 

[6L6]

I'm still confused how to set up the regulator... But I'm sure it will be awesome.

Ok, how much heatsink does it need? Can I use the top plate of the chassis or should it have a real heatsink?

 

[buzzforb]

It needs a real heatsink, although the transistors used are tough. If you haev the boards, just get the type that is shown in as tall a format as possible. You can build it up a section at a time, testing as you go. PM if you need help. I make really nice smoke

 

[6L6]

I have stuff on hand, I'm just trying to plan for layout of the preamp chassis. I'm going to make a stand with this design and do it right.

 

[buzzforb]

I think biggest heatsink you can get that fits the board profile is 2.5" tall. Wakefield or Ohmite