Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hcorneli on November 25, 2016, 01:56:52 pm
-
What PT would you put in a 5g9? What about a 5e9a?
Background: I've built a couple amps (5f2a, BFPR). I'm no electrical engineer; I barely get Ohm's law. I can work safely around high voltage, I can solder, and I can build from a layout and schematic. Understanding the electron, not so much.
My research suggests both originals (and def the 5g9) ran a Triad 8160. Physically these are pretty big, like 3.44 x 2.75 bolt centers, which seems to fit the standard cutout in the similar-chassis tweed Super, Pro, etc.
Electrically the 8160 seems a bit mysterious. Items:
- Fender's scheme for the 5g9 shows 300V AC to each side of its 5U4GB and is fixed bias. Their layout for the cathode-biased 5e9a shows 395V from its 5Y3 to the first filter cap.
- An expensive modern PT said to be a copy of the 8160 comes in both 350-0-350 and 320-0-320 versions. I speculate these might be intended for the 5e9a and the 5g9, respectively. It's rated at 160ma -- I have no idea what the original was.
Many modern PTs even for 5e3 seem to put out more B+ but are physically smaller. For current, many are either closer to 100ma or something like 220.
Ideally I'd find a PT that fit in the standard (big) cutout but gave me the right power and current handling to recreate a tweed tremmie. (FWIW I'm probably most likely build a 5g9). Also ideally I wouldn't have to rig Zeners or other fixes to get the right B+. And in a perfect world I wouldn't have to use a PT with a total medusa of different-colored primaries and secondaries to give me the right voltage. But folks who've built 5g9s especially say the right PT voltage (not too high) is key.
As examples I've looked at, the ClassicTone 40-18029 or Hammond 290DX appear to be at least the right physical size. I'm not dying to buy the expensive modern PT mentioned above. What would you suggest?
-
What PT would you put in ... a 5e9a? ...
I'd use something sized for a tweed Deluxe in the 5E9-A. If you need it to be 100% exact, buy a Mercury Magnetics. Otherwise, anyone's 5E3-type PT is probably close enough.
I used to own an actual '55 5E9, but it didn't occur to me at the time to try to measure or spec any of it. The best choice for OT probably is small & lightweight, as the bass roll-off when pushed works with the speaker and against the large coupling caps to develop its original sound.
-
A 5E9A PT requires a higher HT secondary voltage than a 5G9 because the cathode biasing eats up some current and some A-k voltage.
So, whereas you get about 380-390B+ with a 300-0-300 HT @ 100-120mA in a 5G9, you get 360ish with a 325-0-325 HT @ 100-120mA in a 5E9A.
(Remember that the 5G9 PT also calls for a 50VAC bias tap).
Both types want a 3A 5V winding (for a 5U4), and 2.3A (minimum - including provision for a 500mA lamp) on the 6V winding.
The 5G9 is king of the tweed tremolo amps IMHO.
-
The 5G9 is king of the tweed tremolo amps IMHO.
I never played through a 5E9A but I LOVE my 5G9!!!!! :blob8: Kills my 5E3, IMO. Best dog gone little amp I know of. :icon_biggrin:
And yes great tremolo!
-
What PT would you put in ... a 5e9a? ...
I'd use something sized for a tweed Deluxe in the 5E9-A. If you need it to be 100% exact, buy a Mercury Magnetics. Otherwise, anyone's 5E3-type PT is probably close enough.
The best choice for OT probably is small & lightweight, as the bass roll-off when pushed works with the speaker and against the large coupling caps to develop its original sound.
Thanks, very helpful. In fact, I was basically ready to use a 5e3 PT when I was planning a 5e9a, and just build some sort of adapter plate for the cutout. But now I'm thinking more about a 5g9, and 5e3 PTs seem to come in a little hot.
Also, thanks very much for the OT thoughts. That was gonna be my next research project.
-
A 5E9A PT requires a higher HT secondary voltage than a 5G9 because the cathode biasing eats up some current and some A-k voltage.
So, whereas you get about 380-390B+ with a 300-0-300 HT @ 100-120mA in a 5G9, you get 360ish with a 325-0-325 HT @ 100-120mA in a 5E9A.
(Remember that the 5G9 PT also calls for a 50VAC bias tap).
Both types want a 3A 5V winding (for a 5U4), and 2.3A (minimum - including provision for a 500mA lamp) on the 6V winding.
The 5G9 is king of the tweed tremolo amps IMHO.
Thanks, TW, part of my interest in these amps and especially the 5g9 comes from your input over the years. The note about the bias tap is a good reminder, too.
I love the research phase of amp builds, and it's one of the reasons I thought a less-massively-documented amp than my first 2 would be fun.
`````````````````````````````````````````````````````````````````````
-
The 5G9 is king of the tweed tremolo amps IMHO.
I never played through a 5E9A but I LOVE my 5G9!!!!! :blob8: Kills my 5E3, IMO. Best dog gone little amp I know of. :icon_biggrin:
And yes great tremolo!
Thanks very much. May I ask what PT you have in yours? Maybe its documented elsewhere here, but if you recall?
-
I went with Mercury Mags.
But there's at least 2 (?) members here that used a different iron set.
-
I went with Mercury Mags.
But there's at least 2 (?) members here that used a different iron set.
Yeah, I may just save up longer and go MM if I build a 5G9. It's only money! Part of me hoped not only to save cash but to use something a bit less 'boutique' -- somehow Hammond, MC, etc. just feel more Leo-like to me.
The 'right-size' MC 40-18029 has an option for 305-0-305, and the Hammond 290DSX has 325-0-325. (Both have 50V bias taps.) I'll try to attach the spec sheets below.
But here's where my lack of EE insight kicks in. The MC is said to handle 200mA, the Hammond 230 mA. Will this higher current rating affect B+? Will it affect sag and bloom? Or is it just a nice margin of safety that will let my PT work perfectly with less current draw, like say the 100-120mA Tubeswell mentions?