good sound with cheapo chokes

Joel · 22nd January 2003, 04:56 PM

Of course I couldn't leave it alone, so I made these changes to my three-quarter watt amp...
All the 150 Henry chokes are hammond 156C's for $10 each!
It sounds so good, I wonder why all other grid and plate chokes cost so much.

fragman56 · 22nd January 2003, 06:29 PM

Hi Joel,

Do these chokes smooth the power?

How did it improve the sound?

Rick

Joel · 22nd January 2003, 06:37 PM

Hi Rick,

No, they are plate loads for the voltage amplifiers. The 3rd choke is in the place of Rg for the output tube.

So far I have noticed a slight gain increase and clearer highs over the 36k resistors I used to have there.

Makes sense since, for any frequency greater than 38Hz, I would have increased impedence over the stock RC stage.

fragman56 · 22nd January 2003, 06:47 PM

So to replace the load resistors you calculate the inductive reactance (impedance) equivalent to the resistance and replace with a choke?

Must you choose a frequency (or range or range of frequencies) for this calc?

Thanks for bearing with me on elementary questions,
Rick

Joel · 22nd January 2003, 06:55 PM

Rick, the problem is always going to be the bass response. So, you want to have enough inductance to maintain adequate gain at low frequencies.
Using 2*Pi*F*L=impedence, you get 18k ohms for my circuit at 20Hz... which is just fine. The plate resistance of the 01A is 10k ohms, so a load of 10k would be the -3dB point.
You can see why, when using inductors, lower plate resistance tubes have better peformance. Although with a big enough choke, it doesn't matter.

fdegrove · 22nd January 2003, 07:24 PM

Hi,

Just as with OPTs,using chokes as anode load is a matter of balancing Henry in a quest of having sufficient bandwidth at the frequency extremes.

A lot of inductance will hopefully give good frequency response at the bottom and depending on the quality of the choke may compromise high frequency response to some extend.

It ain't simple,

Joel · 22nd January 2003, 07:32 PM

Quote:

Originally posted by fdegrove
It ain't simple,

It isn't that hard either.

fdegrove · 22nd January 2003, 07:58 PM

Hi,

Quote:

It isn't that hard either.

Wouldn't that depend on the goals you set?

Cheers,

Joel · 22nd January 2003, 08:07 PM

It's a coil of wire! what "goals" do I have to set??

fdegrove · 22nd January 2003, 08:32 PM

Hi,

Bandwidth for starters,that's what.

Cheers,

22nd January 2003, 06:29 PM	#2
fragman56 diyAudio Member Join Date: Jun 2002 Location: Denver, CO	Interesting! Hi Joel, Do these chokes smooth the power? How did it improve the sound? Rick

22nd January 2003, 07:24 PM	#6
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	WALKING THE TIGHT ROPE. Hi, Just as with OPTs,using chokes as anode load is a matter of balancing Henry in a quest of having sufficient bandwidth at the frequency extremes. A lot of inductance will hopefully give good frequency response at the bottom and depending on the quality of the choke may compromise high frequency response to some extend. It ain't simple, __________________ Frank

22nd January 2003, 08:32 PM	#10
fdegrove diyAudio Senior Member Join Date: Aug 2002 Location: Belgium	WHAT GOALS? Hi, Bandwidth for starters,that's what. Cheers, __________________ Frank

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What makes the good guitar pickup sound so good?	darkfenriz	Instruments and Amps	15	1st March 2009 11:46 PM
Good source of Chokes/Inductors	pjpoes	Parts	12	18th May 2007 04:51 PM
Plate chokes & Power chokes	JC951t	Tubes / Valves	3	19th October 2006 03:18 PM
Is this "el cheapo" Velleman100wRMS kit good enough for a subwoofer amp?	Spasticteapot	Solid State	5	17th March 2006 09:09 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

22nd January 2003, 06:37 PM	#3
Joel diyAudio Member Join Date: Oct 2002 Location: Brooklyn, NY	Hi Rick, No, they are plate loads for the voltage amplifiers. The 3rd choke is in the place of Rg for the output tube. So far I have noticed a slight gain increase and clearer highs over the 36k resistors I used to have there. Makes sense since, for any frequency greater than 38Hz, I would have increased impedence over the stock RC stage.

22nd January 2003, 06:47 PM	#4
fragman56 diyAudio Member Join Date: Jun 2002 Location: Denver, CO	So to replace the load resistors you calculate the inductive reactance (impedance) equivalent to the resistance and replace with a choke? Must you choose a frequency (or range or range of frequencies) for this calc? Thanks for bearing with me on elementary questions, Rick

22nd January 2003, 06:55 PM	#5
Joel diyAudio Member Join Date: Oct 2002 Location: Brooklyn, NY	Rick, the problem is always going to be the bass response. So, you want to have enough inductance to maintain adequate gain at low frequencies. Using 2PiF*L=impedence, you get 18k ohms for my circuit at 20Hz... which is just fine. The plate resistance of the 01A is 10k ohms, so a load of 10k would be the -3dB point. You can see why, when using inductors, lower plate resistance tubes have better peformance. Although with a big enough choke, it doesn't matter.

22nd January 2003, 08:07 PM	#9
Joel diyAudio Member Join Date: Oct 2002 Location: Brooklyn, NY	It's a coil of wire! what "goals" do I have to set??

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read