Results 1 to 5 of 5

Thread: Can i replace choke with a resistor?

  1. #1
    daz
    daz is offline
    Old Timer
    Join Date
    Jan 2007
    Posts
    1,984

    Can i replace choke with a resistor?

    I read that to big a choke can cause an amp to sound stiff. My new EL34 build does seem less cushy and sorta stiff. i'm using a 20H choke as in the matchless chieftain. In order to determine if it IS contributing to a stiffness in the tone, can i replace it with a reEL34 plates are at 390v and the dual cap can is 32/32.

  2. #2
    Senior Member
    Join Date
    Mar 2007
    Location
    Philadelphia suburbs
    Posts
    473
    Yes. There is no inherent problem doing that. It won't filter the DC as well though. You are just changing the power supply topology. A choke is not "required" for a capacitive pi filter, just a resistance in that place in the circuit. BTW, since the power tubes get their voltage off of the first power supply node (before the choke), this really won't make much difference in the squishyness of the power section of the amp.

    That being said, you can try some other things that will let you keep the superior filtering of the choke & add some spongieness to the feel of the amp.

    1.) Just add a resistor in series with the choke (100 - 1000 Ohms maybe?). You get to keep the choke for good filtering but still add some "sag". However, this will still not affect the power tubes (as noted above).

    2.) Add some low value, high wattage resistors in series with the rectifier (either on the AC side or directly following the dioides, I don't think it matters much). This is a poor man's tube rectifier simulator. The voltage drop across the resistors will change with current draw & affect the voltage rails of the entire amp, including the power section, similar to a tube rectifier. Start with something small (like 22-47 Ohms) and work your way up from there until you get the feel you like. Keep the choke in the circuit.

  3. #3
    daz
    daz is offline
    Old Timer
    Join Date
    Jan 2007
    Posts
    1,984
    Well, if you're sure a R won't change anything i'll leave it as is, tho i may give the sag R in series with the choke a shot. Before or after the choke, or does it matter? (assuming 5 watt?) By the way, it's a tube rectifier.

  4. #4
    kg
    kg is offline
    Lifetime Member kg's Avatar
    Join Date
    Aug 2006
    Posts
    618
    Quote Originally Posted by cbarrow7625 View Post
    Yes. There is no inherent problem doing that. It won't filter the DC as well though. You are just changing the power supply topology. A choke is not "required" for a capacitive pi filter, just a resistance in that place in the circuit. BTW, since the power tubes get their voltage off of the first power supply node (before the choke), this really won't make much difference in the squishyness of the power section of the amp.
    if the g2 supply is post-choke, as is typical, then the amp certainly WILL get softer with the additional DCR in the supply rail.

    basically any time you talk about multigrid power tubes, forget the plate. the screen is where it is at... it is basically the "plate" of a triode. put a stiff, well filtered screen supply in and you have a low noise, stout amp. put a lot of series R, or multiple big screen stoppers in and the amp gets squishy.

  5. #5
    daz
    daz is offline
    Old Timer
    Join Date
    Jan 2007
    Posts
    1,984
    So then i guess mooreamps was right when he said his 5.6k screen R's make his amps squishier than those with 1k screens like mine. I tried 2k but no big difference I may have to try his 5.6k's.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Resistor in series with choke
    By Paul P in forum Theory & Design
    Replies: 10
    Last Post: 05-18-2008, 07:06 AM
  2. blackface vibrolux. what to replace?
    By imo in forum Vintage Amps
    Replies: 12
    Last Post: 05-08-2008, 10:19 AM
  3. Marshall repair - how to replace speaker??
    By scrapyard_swag in forum Maintenance, Troubleshooting & Repair
    Replies: 1
    Last Post: 05-28-2007, 08:51 AM
  4. replace one or all speakers?
    By flavourful in forum Maintenance, Troubleshooting & Repair
    Replies: 8
    Last Post: 05-19-2007, 08:42 PM
  5. Can I replace 8417 with 6550 tubes?
    By Doug in forum Mods & Tweeks
    Replies: 7
    Last Post: 10-20-2006, 02:42 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •