Will adding a 10H/125mA choke hurt bass performance

[andy2]

I am thinking of adding an inductor choke to limit the current rush at start up to help save tube life.

The choke would be added between the rectifier and the power capacitor.

My question is will it hurt the bass performance?

[ray_moth]

If you mean adding the choke between rectifier and the first smoothing cap, what you will get is a more stable but much lower B+ voltage (about 40% reduction or more). That might not work for your amp but, if it does, then it should improve the bass if anything.

[analog_sa]

Why would it possibly hurt bass performance? By converting your PS to choke input you'll get better regulation and as a result better bass. Keep in mind the output voltage will be much lower.

[arnoldc]

if i may...

fake choke loaded PSU

i use small value film/oil caps before the choke, to get to a reasonable B+

so let's say, we'll add:

2uF - 10H after your rectifier. tune the 2uF to suit B+ requirements, no more than 10uF as it becomes cap input PSU then, i guess.

[kevinkr]

I am not sure that this "fix" addresses in any way the original issue you raised.

Can you be more specific about the nature of the problem you are having and the topology of your amplifier?

If installing a choke raises the source impedance of your power supply significantly this is not going to necessarily result in either a perceived or measured improvement in bass performance, quite possibly just the reverse.

There are other good reasons for adding the choke, like lower ripple on the supply and better voltage regulation under varying loads, although with a class A SE output stage this factor is irrelevant as the load current is invariant. (Choke regulation does NOTHING at all for line regulation and IMHO this is a big issue.) **However** You need to assure that the resulting output voltage is within a stone throw of what you now have otherwise both output power and linearity will be affected, perhaps adversely.

Kevin

[kevinkr]

Hey analog_sa,
Pretty cool signature, but unless it is (sic) there are some pretty egregious spelling typos in there...

edit: oops, spelling error LOL

[amperex]

SE or PP amp?

Power or preamp?

SE power amps likes lots of stored energy where as PP power amps are more constant current & forgiving in Class A.

Where do you want to place the choke?

What is PS now? CRC, CLC, LC,, etc.

Just not enough info from your question to give an answere here.

[analog_sa]

Originally posted by kevinkr
Hey analog_sa,
Pretty cool signature, but unless it is (sic) there are some pretty egregious spelling typos in there...

edit: oops, spelling error LOL

It's as sic as they come.

[andy2]

Originally posted by amperex
SE or PP amp?

Power or preamp?

SE power amps likes lots of stored energy where as PP power amps are more constant current & forgiving in Class A.

Where do you want to place the choke?

What is PS now? CRC, CLC, LC,, etc.

Just not enough info from your question to give an answere here.

It's power amp with PP config using 2 300B per channel that supposedly puts out 22W per/ch.

Could you guess how much RMS current consumed per channel on average?

I am trying to find a suitable thermister so this info could be helpful.

Here is the schematic:
http://www.geocities.com/hai_vu1/schematic.JPG

I am now thinking of NOT using a choke since it will reduce the B+ voltage and change the entire ouput stage altogether.
After doing some research and asking around here, I plan to use a thermister instead which is a lot more simple.

I plan to use a manual bypass switch to take the thermister out of the circuit once the amp is turned on.

Thanks.

[kevinkr]

You should locate the thermistor in the primary side of the power transformer, and although some do switch it out of circuit once the amplifier is on I think this is unnecessary.

Take a look at Ametherm, I think what you want is a device rated at about 4A, with a cold resistance of 15 - 20 ohms and less than 0.5 ohms warm.

Their site is www.ametherm.com and here is a device I think would be suitable for this use: http://www.ametherm.com/Data%20Sheets/SL12%2015004.pdf
You might even be able to get a couple of samples since your need is limited.

Also you could replace the existing 100 resistor with a choke of about equal resistance say 10H/30mA/~100 ohm and get a quieter supply rail to the driver stage.

You can delay the application of B+ to the output tubes with a timed relay if you are concerned about cathode stripping. Note that this may cause a pop when it switches.

edit: added additional info

Kevin