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12SL7 - 6V6 SE amp ( my ver of lacewood)

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(I thought I already posted this thread late last night... but I can't find it now so if this is a duplicate please correct it.)

I read Matt's text and schematic about his Lacewood amp ver-2 and I thought I'd like to build a SE too.
So this is my version of the SE 6V6 Lacewood Amp Ver#2.
I call it "Peter's SE 6V6 amp":

The major differences are:
1. I used a more compact power supply but retained the low (20mv) ripple.
2. I used an LM317 for a 46ma CCS for cathode bias
3. I used a 12SL7 instead of a 6SN7 because I needed more gain since my input source is Mp3.
4. I used a 12uf 400vAC dropper cap for filaments. It supplies 12v@600ma
5. I used 6 tube sockets instead of 3 because I wanted to be able to use other available alternate tubes:
The pre-amp tube is either an octal 12SL7 or a 9-pin 12AX7 ... both are (150ma)
The output tubes are either octal 6V6 or 12V6 - or 7-pin 6AQ5 or 12AQ5
6. I used an A/B switch to arrange the output tube filaments in series (6v@ 450ma) or Parallel (12v@225ma x 2)

Because I designed a more compact power supply and by using a dropper-cap filament supply, I was able to build this beautiful little amp in a nice small wood box (7"x7"x2.5")
I used a 100VA toroid dual wound transformer (not shown but fits the empty space on the lower half of the box) Any other 120vAC- 100VA transformer of your choice will work as well.

So, not only does this stylish little wooden box amplifier look handsome and cute on my stereo shelf in the LR but it also sounds so perfect too. The audio that this wonderful ultra-linear SE amp delivers is incredibly realistic sounding.

The Mp3 input jack is on the left next to the pilot lamp and the two RCA jacks on the right side are the speaker output jacks.

I recommend building this SE 6V6 amp, as it goes together so easily and it looks good and sounds good!
An externally hosted image should be here but it was not working when we last tested it.
 

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Last edited:
Sorry I am not familiar with what the photo gallery thread is for.
I thought the tube amp threads were together by amp type or tube type so that's why I put it here.
I can't find my earlier post there or anywhere. So I'm confused as to how to find it or the value of that thread vs this thread?
Why would my amp post be viewed more in that thread? I thought ppl searched for new posts or old posts by amp type or tube type.
So what's the difference of this thread vs that thread?
As far as where "I" want it to be... I don't know.
This latest post is a bit more complete than my earlier post.... so I think it is better. But all I care about is ease of locating my thread by amp type or whatever.
Please explain and advise. Thank you.
 
Ex-Moderator
Joined 2011
:cop:
I can't find my earlier post there or anywhere.
See Photo Gallery
Why would my amp post be viewed more in that thread? I thought ppl searched for new posts or old posts by amp type or tube type.
The Photo Gallery has more than 3.3 million views, by far the highest in the Tubes forum. Whereas the typical amp build thread gets less than 500 views if that... People tend to browse more than they search, but you are welcomed to start your own thread if you feel it serves your purpose better.
 
Please advise me as to where you feel this "latest" more updated edit should be located.
If it is best to be in that photo gallery... then please move this latest version there to supersede the earlier, less complete one. OK?



Also please tell me how best to search for it in your search box. When I search by "pbpix" it does not show in the results.
thank you
 
Hi AquaTarkus:
To be honest... I haven't been able to tell much if any difference... esp because I haven't been listening long enough to each to be able to tell. But since they are supposed to be equivalent I didn't try too hard.
But if anything... I think the 12AX7 seems to have a bit of a "stronger sound"... if that makes any sense.
 
100k is more appropriate with such a low value of cathode resistor on the tube, so a worthwhile change, although distortion may be a smidge higher than the low-and-lean trickle of current from a lower plate current, although 220k would work well with a 2200~2700R cathode resistor. 220k plate with 2700R unbypassed cathode is one of my favorite setups on them when used with a ~300 or so volt supply.

Also, I bet the higher gain of the 12AX7 is what contributes to the difference in sound. The 12SL7(6SL7) is a fantastic tube, but doesn't have the high mu of the 12AX7.

Why did you add an additional (unbypassed) resistor under the cathode? unless adding a bit of global negative feedback (in which case a 1500~1800R resistor would be a good start) there doesn't seem to be much reason otherwise.
 
Hi:

I needed to make a change because I was hearing some "noisy-sounding" notes in a favorite piano piece ( "Darn that Dream" by Ariel Pocock)
YouTube

I didn't like the way some of the notes ended (resonating too long or something odd) "distorted."
I could tell there was a problem on peaks once in a while, compared to my other PP 30W Antique Sound Labs amp "AQ1003" where they were sounding absolutely perfect. (I might not have noticed until I made the side-by-side comparison.)

I didn't know what the cause was, so I was testing some global NFB .... (too much flatness) and some local NFB by lifting the cathode resistor a bit. That seemed to help.

Then I thought maybe it is distortion from wrong bias settings.

So changing the plate resistor .... really did the trick... and I just decided to leave the cathode resistors as is since it all sounds so much better now.

Both the 12AX7 and the 12SL7 are sounding GREAT here now. And those occasional noisy-sounding notes from that piano tune are gone... all is absolutely perfect-sounding now! The sound is so beautiful. So clear, extremely realistic; and it has an almost three-dimensional aspect to it now.
I love it.
 
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