Bugera V22 Infinium CHOKE mod

[Palantine]

Hi there everybody and thanks in advance for reading my post and helping me.
I looked all around the net for a thread on this topic without any result.....my goal is to fit my BUGERA V22 Infinium with a CHOKE.

Regarding the attached schematic, the resistance to swap for the CHOKE should be R21 (390ohm, 5W).

First problem: how shoul I pick up the right one? Could you please help me with the right specs.....resistance, inductance, DC current rating.

I live in EU and I can get from Germany Hammond products that I consider very well made and also affordables (compared to other US brands).

Second problem: as for my Peavey Classic 50 and 6505 plus, putting a CHOKE in place of the power resistor placed after the stand-by switch, could cause a loud pop when you turn the stand by switch ON (called SPIKE).....how should I have to rewire the stand by switch to prevent/fix that?

Really any help/advice will be very appreciated. I rarely post in a tecnical forum coz I'm an hobbist but inexpert of technical stuff so I can't give any help to the other people. Thanks again.

Palantine

[nickb]

What is it you are trying to solve by using a choke? If it's hum it might be cheaper and easier to use bigger capacitors and assuming you've proven that is where the hum is coming from.

On the Classic 50 and 6505 I see the standby switches the screen & preamp supply. You said you replaced the resistor after the standby but I see a 400 ohms resistor before it. The purpose of the resistor is to limit the surge current to protect the switch and prevent noise. If you replaced that one then than would cause a massive switch and component destroying spike when opening the switch. Personally I put the resistor back and remove the choke It can be tricky find ways to noiselessly have a standby function. You can try opening the output tube cathode's path to ground with the standby. Or, you could wire it as a mute.

[Palantine]

What is it you are trying to solve by using a choke? If it's hum it might be cheaper and easier to use bigger capacitors and assuming you've proven that is where the hum is coming from.

On the Classic 50 and 6505 I see the standby switches the screen & preamp supply. You said you replaced the resistor after the standby but I see a 400 ohms resistor before it. The purpose of the resistor is to limit the surge current to protect the switch and prevent noise. If you replaced that one then than would cause a massive switch and component destroying spike when opening the switch. Personally I put the resistor back and remove the choke It can be tricky find ways to noiselessly have a standby function. You can try opening the output tube cathode's path to ground with the standby. Or, you could wire it as a mute.

Hi Nickb, normally I install CHOKEs for better filtering, reducing noise but mainly to reduce SAG effect (when power tubes needs more current....).
Really I'm not able to expalin in technical language but I know for sure that companies puts a resistor (cheap solution) in place of a CHOKE in order to keep prices as low as possible. Simply I'd like to improve my amp.

[nickb]

Hi Nickb, normally I install CHOKEs for better filtering, reducing noise but mainly to reduce SAG effect (when power tubes needs more current....).
Really I'm not able to expalin in technical language but I know for sure that companies puts a resistor (cheap solution) in place of a CHOKE in order to keep prices as low as possible. Simply I'd like to improve my amp.

You are putting the choke in a place where it doesn't do much good. The big current draw change is from the power tubes anodes and that is supplied from before the choke.

The source of your sag is the resistance of the power transformer and there is not much you can do about that. If you can accept a slightly lower power output you could regulate the supply with MOSFET & zener.

[J M Fahey]

Hi Nickb, normally I install CHOKEs for better filtering, reducing noise but mainly to reduce SAG effect (when power tubes needs more current....).
Really I'm not able to expalin in technical language but I know for sure that companies puts a resistor (cheap solution) in place of a CHOKE in order to keep prices as low as possible. Simply I'd like to improve my amp.

With the utmost respect: you donīt know why you are installing a choke, just read a few Forum posts (not here ,) ) about amp improving "other" amps, not yours, and want to improve yours, although you donīt now what it does exactly.

The whole "they cheap out the design" idea is pure Forum BS.

Fact is that in "the mythical old days" they relied a lot on chokes because capacitors were friggin' expensive, so they used ludicrously small values (think 8uF everywhere with 16uF being the best they could do) so the options were, IF you used only RC (cheaper) filtering, either lots of hum (you made R small) or lots of sag (you made R large)

Enter the mighty choke, which has "low R" for DC (so low sag) and "high R" for AC, (so high hum rejection), best of both worlds ... which comes to a price of course, chokes were more expensive and bulky.
Not using them for economic reasons resulted in a poor amp. (either hummy or saggy).

But today , capacitors are large and inexpensive ,your small 15W amplifier has one-hundred-microfarads as main filter and forty-seven-microfarads as the screen supply one, both Leo Fender and Jim Marshal would have spit their morning coffee (or tea) if somebody suggested such high values in their 15W amps, 5 times larger than what they currently used.

Ok, marshall used somewhat larger ones, simply because he came later and capacitors had already improved a lot ... even so they are way better (and cheaper) today.

The point is that your Bugera *already* has a small value resistor (390 ohms) to filter screen supply , so it has little sag (which can be attributed to it) and low hum , atributed to large caps, so you are trying to solve a non-problem.

I might accept the need for a choke IF you had a sag+hum problem and traced it to lack of choke ... but I doubt it, I guess you just read some Forum post and want todo the same.

In advance, and before you spend time and money: you will find practically no difference by adding a choke there, so personally wonīt even suggest one.

Just read the schematic: they have 348V before R21 and 344V after it: .... NOTHING .... in the old days even a real choke had a higher voltage drop
Just read the old Tweed era Fender schematics.
Or the VOX ones.

Almost no voltage drop means almost no sag, definitely nothing you can *hear*.

Want peace of mind and get "choke results?"
Ok, Iīll play: double C6 to 100uF and halve R21 to 220 ohms.
Not that itīs needed, you already have low hum and low sag but itīs the same as if you had replaced R21 by a choke.

EDIT: the whole idea behind it is that "Bugera amplifiers are cheesy cheap amplifiers made in a sweatshop by slaves"
fact is that they are very well made, and yes, they are inexpensive, but for other way more important reasons:
* Chinese Yuan is undervalued *on purpose* to make chinese products cheaper than anything else
* Chinese government is *agressively* helping Chinese Industry, giving it lots of subventions, low/no interest loans, pushing trade agreements all over the World, allowing American capital invest there, etc.
* Chinese salaries are incredibly low.
* they have huge efficient modern Factories.
* Bugera is "vertically integrated" , they make *everything* themselves so costs are incredibly low.
As one example: they started using "Bugera speakers" which actually were Italian SICA made "Jensen MOD" , very good and inexpensive, then started making them in house .... now they even press their own cones (hear that Eminence and Celestion).

Be certain that they would use a choke if it were needed, they would make it themselves for peanuts.

[Palantine]

Dear Juan Manuel,
first of all THANKS for your exhaustive answer.
You'r absolutely right! I have no skills in electronic, so I use to apply what I read all over the forums, blog or webpages of famous amp modders.
To be honest I don't know how to read a schematic.....but many DIYers doesen't know (I guess).
Simply I try to improve my amps because I like it.....l like to spend my time replacing cheap parts (capacitors, resistors, pots), fixing hum problems, replacing speakers, etc etc.
I'm able to do some easy fix......I have soldering skills; I build my pedals, modify my guitars, change pickups and stuff like that.

I installed CHOKES in almost fifteen amps but I always found pages with "easy to follow instructions" for these.

I probably have not got any improvement but it was pleasing and relaxing.

Sometime we believe to improve our amps simply because 'we need to believe it'.......

Anyway, for what I understand, not all amps need a CHOKE, not my BUGERA and YES, I love this amp and I find it sounds as good - even not better - than many other more expensives amps I own or I owned.

And YES, there are so many Myths and BS on the net but I'm an hobbist.....I'm fascinated from amp tweaking, so forgive my naive thread.

Thanks again for your answer, (you almost killed me.....hahah I'm joking); forums are probably the best part of the internet....it is always interesting to deal with people all over the world!!

[Steve A.]

FWIW this is not the schematic for the Bugera V22 Infinium amp but the earlier V22 non-Infinium model which defeats most of the technical reasons for not installing a choke in the amp. It's like planning an attack on Gettysburg while looking at a map of Waterloo.



Steve Ahola

P.S. Here is an interesting discussion of chokes in guitar amps from the Hoffman forum. Adding a choke to a Bugera V22 might possibly improve the sound and response for a blues guitarist (see post #9.) It's not all about volts and ohms, folks...

To choke or not to choke

P.P.S. Yes, I sometimes like to play the Devil's Advocate...

[mozz]

"The whole "they cheap out the design" idea is pure Forum BS."
I guess you never worked for a major manufacturer of audio equipment. They all do it, it's a penny saved and they will do it to save that 1 cent.

Put a choke in if you wish. Make sure you have screen resistors.

[Palantine]

FWIW this is not the schematic for the Bugera V22 Infinium amp but the earlier V22 non-Infinium model which defeats most of the technical reasons for not installing a choke in the amp. It's like planning an attack on Gettysburg while looking at a map of Waterloo.



Steve Ahola

P.S. Here is an interesting discussion of chokes in guitar amps from the Hoffman forum. Adding a choke to a Bugera V22 might possibly improve the sound and response for a blues guitarist (see post #9.) It's not all about volts and ohms, folks...

To choke or not to choke

P.P.S. Yes, I sometimes like to play the Devil's Advocate...

Hi Steve,
most of mods I performed to my Peavey Classic 50 comes from your blog/webpage so, first of all, thank for your contribution.
"Adding a choke to a Bugera V22 might possibly improve the sound and response for a blues guitarist"....the fact is that I don't know WHERE to istall a CHOKE and WHICH specs it should have to work on this circuit (I know the schematic shows the non-Infinium model, but I assumed the power section was almost the same.....).

[J M Fahey]

"The whole "they cheap out the design" idea is pure Forum BS."
I guess you never worked for a major manufacturer of audio equipment. They all do it, it's a penny saved and they will do it to save that 1 cent.

Put a choke in if you wish. Make sure you have screen resistors.

I AM a Manufacturer, and as cheap as can be , so nobody can lecture me on that.

And I strongly stand behind my

"The whole "they cheap out the design" idea is pure Forum BS."

although I should extend it (I supposed it was clear enough but, hell, I should have counted on actual readers) to:
"The whole "they cheap out the design" idea is pure Forum BS." , Musicians think that amps sound bad because they have "bad parts" (read: "cheap") and foolishly think they can improve sound by using "good" (read: "expensive") parts , same value of course.

Practical example: Musician pulls a Red/Blue/Green/Mustard/White/Yellow/Black .022uF 400V coupling cap from his amplifier and replaces it with a Red/Blue/Green/Mustard/White/Yellow/Black .022uF 400V , only difference is that (usually) colour is different and (always) price is much higher and "now amp is smoother/warmer/cleaner/sharper/bluesier/sustainier" .

Well, lots of (sly) vendors make a living out of those unbased perceptions.

FWIW neither Leo, Jim, Everett, Hartley or Tom specified a brand in their schematics , not even implicitly (by buying same brand and model year after year), but as can easily be seen by opening stuff from different years, they clearly bought from the supplier which offered them the best deal at a given time.

Now Internet Gurus place great Faith in such meaningless things ... why am I not impressed?

Iīm quite certain that for Leo, Jim, Everett, Hartley or Tom , when actually manufacturing amplifiers "volts and ohms" became the most important thing.

As in: I very much doubt each and every amp they put out was played by a Musician with a soldering gun and an assortment of parts available so he could tweak each one by ear/feeling/whatever.

I bet they were checked so they all had the basic sound expected, and the very few with problems would be sent to a bench where, say, *volts* would be checked to see what was wrong, usually an assembly or wiring problem, because parts are in principle assumed good, thatīs what buying in bulk from known good trusted suppliers is about.

[Enzo]

Yes, QC consisted of plugging the amp in, check if all the controls do their thing, and do all teh jacks work. And does it seem to have anything wrong. No? Then into the box.


yes, manufacturers want to save money. If they make 10,000 amps and they can save a dollar on each one, that is $10,000 they save. Not bad. I have talked to engineers here at General Motors (Lansing is a big GM town) and there are guys who will jump up and down with excitement if they can save a penny on the price of a ignition switch key entry. Because there are millions of them made. A million pennies is that same $10,000.

But that is not the same thing as seeing how much cheap junk they can throw into something.

They no longer use chokes because as was said above, the same filtration can be had from much cheaper caps instead.

When I hear that the choke will "improve sag" or some such, I always have to ask, "OK, how much sag do you have NOW?" And as was also mentioned above, how much of it comes from that resistor, ie how much came from the power tubes themselves ahead of the choke/resistor position.

I have a cross on my apartment door to keep away vampires. MAybe if I put one on the elevator door too, it would improve my vampire protection?