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Discussion in 'The Workbench' started by SpHj, Oct 30, 2017.
I’m thinking I may try this...what would you guys recommend? ( Brand, Henries)
Go for a 5 to 7Hy, Hammand or ClassicTone.
Hrmmm, I was looking at the Hammond 194G 3H 250mA. What kind of a difference would 2/4 Henries make?
I understand the JCM900 and maybe SLX to be top frequency heavy. The larger coils will lend a hand to he bass side.
Gotcha, good to know!
I think it (a choke) would make absolutely no difference what-so-ever to the low frequencies.
But here's what will:
A bypass cap across R7, 2.2 uF 35v or larger...and the + of the cap faces pin 3 on V2a.
Well, maybe I would use .68...
This is what a choke is for:
to get more hum out of the B+ supply.
This is a choke calculator:
Yes well, I have gone over it and the answer was to bypass R7 with a capacitor.
Because, V2 has no low frequency response without it...therefore....no bass in = no bass out.
This is the basic problem w/ JCM 900, in general...
Here is another great calculator which will help fix bass response problems:
No it will not boost or route more low frequency in the signal chain but it will help hold voltage more stable during high current demand of low frequency passages. He may or may not notice it depending on the playing, speakers or cabinet but it does not hurt to opt for a larger choke if adding one.
Anyone else adding and modifying the resistor or choke between power tube plate and screen care to comment expressing there findings?
I just finished overhauling a 2500 SLX. New electrolytics and filter caps, bridge rectifier and all new iron. I figured since I was getting new transformers, I may as well get a choke too. I can't tell you what the difference is since the amp wasn't working when I got it, but I can tell you the last thing it lacks is bottom end. I doubt the choke had anything to do with it, but I'm sure the new transformers and caps did.
Thanks for your input guys, I ended up ordering the Hammond 194G (3H, 250mA) as my local supplier has them in stock. This amp isn’t lacking in the Bass department, but I may try tweaking the NFB for a little more output while I’m in there. Hopefully the choke will give me a little more clarity at higher volumes/live as that’s my main concern with the amp.
I think a lot of this choke transformer stuff is imaginary.
I think the solution to sound quality in these designs is in the preamp, not the power supply....not the OT either.
The Marshall Transformer: there is nothing wrong w/ it. It's a perfectly good transformer.
Unless it's bad, there is no reason to change it.
Sure...the new transformers have better frequency response...BUT the preamp is intentionally made to remove low frequency.
and so, unless there is bass "in" the audio, it won't come out of the transformer...no matter what transformer.
And you can make the power supply stiffer....but you still don't have any bass to start with.
No bass in = no bass out.
That's the real issue. Throwing money at it does not fix that.
These don’t have a Choke from the factory, hence adding one. I’ve not once stated anywhere looking to add “Bass” to my signal, don’t know where that came from.
I gotta agree with the amp mad man on this one. I don't think a choke or a resistor makes any difference. If the bass ain't there it ain't there. I thought my 6100's 3rd channel had tons of bottom end until i bought a Fender Dual Showman Red Knob and that thing knocked the light out of my ceiling.
Did you not read my posts? We’re getting a little off topic...I do not have a lack of Bass issue whatsoever.
I wasn't replying to you..................
Noted, and I fixed my post as well. No harm meant!
Maybe it is the other JCM900 that are top heavy frequency wise. As HpHj said he was going to add a choke so I mentioned what a larger choke might do for the situation but it all depends as I had mentioned earlier.
Got my Choke in today, will update my findings after I install her this afternoon
Got the Choke installed, after playing her for a solid 1/2 hour I didn’t feel any sag/swells like I did before. Seems a little tighter for palm muting as well, although that may just be a placebo effect. All in all, worth the 1/2 hour of my time.
Wait a minute. Are you palm muting everything or just chugging low chords?