Choke placement in early Tweed circuits

[Smokebreak]

Built a 5E5A Pro into an old chassis yesterday that had a Classic Tone PT w a low V secondary, and a 1750M OT. It sounds fantastic but I'm curious about the power supply.

I wired it up "normally", so to speak, with the choke(ok not really.....a 330r 5W resistor) in between the plates and screens, and added screen resistors
Of course a lot of these early tweeds had the choke before the plates, with the choke bearing the full current draw of the tubes. The screen supply is also connect to the OT centertap/plate supply.

I went to buy a choke big enough to handle the job, and they're like $50! My curiosity dwindled pretty quickly, but if I were to implement the supply just like the schematic, what can I expect different in feel or tone?
Also of note, I'm using GZ34 for less drop, and my voltages are pretty much spot on w/ Leo's. Also using a 12ax7 in V2, as I could only find one 12ay7 around here.

Also taking speaker recommendations....The box I have for the chassis has a 12" baffle so I'll go with that....already have a 15" combo anyways
I'm feeling like an alnico is warranted here...looking at the Fat Jimmy A1260 and Celestion Cream Alnico. Thanks!

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[martin manning]

Hammond 194G at 3H 250 mA should be good for that, that are under $25 retail. A CLC input will take most of the ripple voltage off the B+. I have no direct experience, but I would think that should reduce intermodulation with the guitar notes and move towards an overall cleaner tone.

[pompeiisneaks]

Hammond 194G at 3H 250 mA should be good for that, that are under $25 retail. A CLC input will take most of the ripple voltage off the B+. I have no direct experience, but I would think that should reduce intermodulation with the guitar notes and move towards an overall cleaner tone.

Agreed, also a simple path to go without a choke is to just increase filtering. Often that's a trick HAD used to make an amp cleaner... more filtering. Back in the old days I think transformers were almost cheaper than the electrolytic capacitors. Thus having the choke in path to filter out that ripple was cheaper than the caps, now electrolytic caps are dirt cheap and copper is through the roof

Edit; To clarify, by cleaner I mean cleaner power, not like, cleaner headroom or something
~Phil

[Roe]

Hammond got some nice big chokes. A CLC or Pi filter sounds and feels different from the standard power supplies with high filtering

[bepone]

I went to buy a choke big enough to handle the job, and they're like $50! My curiosity dwindled pretty quickly, but if I were to implement the supply just like the schematic, what can I expect different in feel or tone?

CLC is standard in HiFi both for S.Ended and Push pull. You will loose all hum and can expect apsolutely no noise from the amp output section, remain only humm from your layout and grounding methods

no noise also in case of imbalanced output section (heavilly dismatched tubes which would create humm in other amps)

about the sound.. i'm not sure that this is the best solution for guitar amp.. loosing modulation od plate voltages from highish ripple..there was some study online about , and people at the end didn't like completely DC filtered anodes..

I'm feeling like an alnico is warranted here...looking at the Fat Jimmy A1260 and Celestion Cream Alnico. Thanks!

cant miss with Alnico Cream, i have it very smooth, for my many friends top speaker, also in 1x12"

[Roe]

about the sound.. i'm not sure that this is the best solution for guitar amp.. loosing modulation od plate voltages from highish ripple..there was some study online about , and people at the end didn't like completely DC filtered anodes..

+ 1 for push-pull amps, although it is great for single ended amps (and some exceptional cases perhaps)

[Colossal]

I build SE amps with a CLC up front. The inductor will need to handle the full rated current of the amp at idle, etc, so they can get large. I use a fairly high inductance with low DCR, so as not to drop too much voltage. As Bepone said, it makes for a dead quiet amp.

Yes, I forget who wrote that article (maybe Kuehnel?) about how some power supply modulation was an essential part of the tone and feel of an old Bassman.

[martin manning]

Yes Keuhnel. It’s in his 5F6-A book.

[pdf64]

… a simple path to go without a choke is to just increase filtering…

That might not be an option if a valve rectifier is being used.

[pompeiisneaks]

… a simple path to go without a choke is to just increase filtering…

That might not be an option if a valve rectifier is being used.

My understanding is this is only for the first filter post rectifier no? I.e. you have a rectifier's max capacitance rating but only for the first cap? Then you can increase the filtering afterwards... correct? Or is that a max per capacitor in every filtering position?

~Phil

[mhuss]

Yeah, it's mainly for the first cap, although an additional 220uF 100 ohms away will also affect things. The spec is about peak current, which is proportional to the amount of electrons needed to fill that cap up to normal from zero.

[pdf64]

… a simple path to go without a choke is to just increase filtering…

That might not be an option if a valve rectifier is being used.

My understanding is this is only for the first filter post rectifier no? I.e. you have a rectifier's max capacitance rating but only for the first cap? Then you can increase the filtering afterwards... correct? Or is that a max per capacitor in every filtering position?

~Phil

Sorry, given the context, I took an increase in the reservoir cap value as being implicit. ie how / where else to increase filtering to get the same result as the 5E5a’s pi filter?

[pompeiisneaks]

Maybe I too missed something, but looking at the 5E5 it uses a 5U4GB that can take a 40uF cap at the first node, the 5E5 uses only 16uF. All of those 16UF caps could be upped to 32 easily for a much stiffer power supply and cleaner power without adding a choke. for 40$ you have 4 30ish uF caps that would filter that noise really well. Of course a single choke sub 40$ gets you a lot, but then you still have less filtering at all subsequent nodes too.

Again, I might be missing the point, please forgive me if so

~Phil

[Roe]

CLC filters are great on ac30s and ac15s

[Smokebreak]

Hammond got some nice big chokes. A CLC or Pi filter sounds and feels different from the standard power supplies with high filtering

This is what I'm after, right here. In what way would you say? better yet, would you say CLC sounds different that a standard supply with "normal" filtering? Something that I guess goes without saying (but hasn't really been brought up) is that increasing the filtering will change the feel of the amp, something I don't want to go too far with, in a Tweed amp.
However I started with 22uf across the board in this amp