I did this one while waiting on a shipment from RJ for a 4x6BM8/ECL82 Liverpool, now beginning.
This is a rework of an old early '50s Valco/Supro circuit that used a 6V6, upgraded to a 6L6. Modeled after a period Canadian combo knockoff that a friend has. It is unusual in that it has a huge 40uF oil cap can as the reservoir cap, so I duplicated that feature. Probably cheap WW2 surplus at the time.
The first time I have used true point to point wiring as well, just like the originals.
The OT is a Hammond 125DSE, the PT is a 272BX. I tried an old NOS Stancor A-3852 OT but it oversaturated as I put +60mA DC thru the primary which is only rated for 40mA.
Tubes shown are a '40s Ken-Rad 5Y3G, '43 Ken-Rad 6L6G, and a '51 Ken-Rad JAN-CKR 6SL7GT. I subsequently changed the 6SL7 to a '61 Tung-Sol 6SL7WGT as it was just as quiet but a tad cleaner and tighter.
As my friend's Canadian amp used a Rola speaker, I bought two 12" '61 Rola alnico plug speakers on Ebay for $35 each and put one in my Avatar 1x12 cabinet. Overall it sounds close to the Canadian amp but a bit cleaner I guess because of the 6L6 vs 6V6 and 12" speaker vs 8" in the original combo. But it rocks nicely when dimed!
1x6L6G SE 10W maybe.
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David Root
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1x6L6G SE 10W maybe.
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Stevem
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Re: 1x6L6G SE 10W maybe.
Your plate voltage is some 15 too high for true class A, and I would add atleast a 50 uf bypass cap in there.
If you get nasty distortion when driven flat out then you could be drifting into class B.
If the bypass cap the output stage then clips too early for you then I would back down on the drive signal level to suit your taste!
If you get nasty distortion when driven flat out then you could be drifting into class B.
If the bypass cap the output stage then clips too early for you then I would back down on the drive signal level to suit your taste!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: 1x6L6G SE 10W maybe.
Steve,
I fixed the initial distortion problem by changing the Stancor A-3852 OT shown in the pics to a proper SE OT, the Hammond 125DSE, which is about twice the weight of the Stancor. I just haven't taken a new pic of the amp as it is now. The Stancor was a general purpose OT without an air gap, and I was exceeding the rated DC on the primary by more than 50%, so the sound had a harsh high end.
Now I get nicer distortion when cranked.
I want to keep the output characteristics of the original design ie no cathode bypass cap. AB1 instead of A operation is OK for me, if that's where it's operating. I'm not wedded to class A.
I fixed the initial distortion problem by changing the Stancor A-3852 OT shown in the pics to a proper SE OT, the Hammond 125DSE, which is about twice the weight of the Stancor. I just haven't taken a new pic of the amp as it is now. The Stancor was a general purpose OT without an air gap, and I was exceeding the rated DC on the primary by more than 50%, so the sound had a harsh high end.
Now I get nicer distortion when cranked.
I want to keep the output characteristics of the original design ie no cathode bypass cap. AB1 instead of A operation is OK for me, if that's where it's operating. I'm not wedded to class A.
When I was a boy I was told that anyone could become President. I`m beginning to believe it--Clarence Darrow
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Stevem
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G
Class AB1 single ended you say?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: 1x6L6G SE 10W maybe.
Just assuming the transition is A to high AB1 to low AB1 to B. I don't know that.
When I was a boy I was told that anyone could become President. I`m beginning to believe it--Clarence Darrow
Re: 1x6L6G SE 10W maybe.
The steeper 'B' load line in Class 'A/B', is a phenomenon of a Push Pull Amp whereby the reflected load resistance through the OT is halved when the current on one side of the OT primary winding is shut off because there is no tube current on that side (because that tube has been driven into cutoff)
So what are we talking about transition from Class A to AB1 in SE for? Where does the steeper load line come in?
So what are we talking about transition from Class A to AB1 in SE for? Where does the steeper load line come in?
He who dies with the most tubes... wins