My late father did alot of TV repair and ham radio stuff in the tube days. Fortunately I kept his box tubes and now I have the itch to make a simple SE amp.
He had a bunch of 50-60's era 1625 and I was stoked to use those. But after searching this site it sounds like the 1625 doesn't have as much love as others. So here is some of the NOS output tubes I can chose from. (Not an exclusive list)
6BQ5
6L6
6V6
1625
I am leaning towards the 6BQ5's as they seem to get much love around here.
What do y'all think?
He had a bunch of 50-60's era 1625 and I was stoked to use those. But after searching this site it sounds like the 1625 doesn't have as much love as others. So here is some of the NOS output tubes I can chose from. (Not an exclusive list)
6BQ5
6L6
6V6
1625
I am leaning towards the 6BQ5's as they seem to get much love around here.
What do y'all think?
I am taking an inventory now but I left my sheet at work.
I have about 6 to 8 of the 1625's and 6BQ5's.
A couple of the 6L6 and 6V6's.
A bunch of TV power sweep tubes I haven't jotted down yet.
and a bunch of tubes suitable for drivers.
All new, Arcturus, RCA, TungSol, Sylvania and others.
12AT7 and ECC81 are 2 appellations for the same type. The heater is center tapped; so, either "6" or "12" V. can be used to energize it.
The RH807 employs a short NFB loop technique known, among several names, as "plate to plate". Adding an outer, global, loop may be possible.
If you SS rectify the B+, this low cost item should prove satisfactory as the power transformer.
The RH807 employs a short NFB loop technique known, among several names, as "plate to plate". Adding an outer, global, loop may be possible.
If you SS rectify the B+, this low cost item should prove satisfactory as the power transformer.
Thank you for the pt link.
How are that company's output transformers? Or are Edcor the standard bearer for those?
How are that company's output transformers? Or are Edcor the standard bearer for those?
Dunno about the O/P "iron". FWIW, I'd go Edcor.
If you want to add an outer global NFB loop to the RH807 setup, the power handling capability of the O/P "iron" has to increase, lest core saturation occur. A 25 W. plate dissipation should be safe enough. 40% real world efficiency is a good guesstimate for the full pentode mode SE "final". That makes power O/P roughly 10 W. Edcor's CXSE25-6.5K will work in this build, whether or not GNFB gets used.
Air gapped SE O/P "iron" is more expensive than PP stuff. Edcor's 60 W. CXPP60-6.6K, which you would employ in combination with PP 1625s costs less than the 25 W. SE model. IMO, that's something to carefully mull over.
Does dad's "stash" contain 6CG7/6FQ7s or 6SN7s? Those would go nicely into a knock off of the Harman-Kardon Citation V.
If you want to add an outer global NFB loop to the RH807 setup, the power handling capability of the O/P "iron" has to increase, lest core saturation occur. A 25 W. plate dissipation should be safe enough. 40% real world efficiency is a good guesstimate for the full pentode mode SE "final". That makes power O/P roughly 10 W. Edcor's CXSE25-6.5K will work in this build, whether or not GNFB gets used.
Air gapped SE O/P "iron" is more expensive than PP stuff. Edcor's 60 W. CXPP60-6.6K, which you would employ in combination with PP 1625s costs less than the 25 W. SE model. IMO, that's something to carefully mull over.
Does dad's "stash" contain 6CG7/6FQ7s or 6SN7s? Those would go nicely into a knock off of the Harman-Kardon Citation V.
Attachments
Feedback is from plate to plate. Schade feedback.
RH84 is the variation for the 6BQ5/EL84.
dave
A triode connected sweep amp would be my first choice. When you tell me what tubes you have, I can give you a schematic 🙂
On the SE807RH PS chokes. Are 45H chokes that critical? Those are pretty big. Can I get away with smaller and more economical ones. I also plan on doing SS rectification.
Edcor's iron is fine for a project like this. The 25W 6.5K OTs are $100 each though, which is a bit of a commitment. Everything else I'm seeing for the similar or less money is a severe compromise, with the exception of the 4.8K One-Electron, which would work nicely as well.