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RE: Adding series resistor for ribbon?

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In Reply to: RE: Adding series resistor for ribbon? posted by AkuAnkka on February 16, 2015 at 12:00:30

Yes, it is perfectly possible to add a series resistor just next to the ribbon.
Unfortunately, even if you stump up for the expense of Duelund graphite resistors, it will still degrade the sound slightly - compared to not having a resistor. :-((
Also, adding a res will reduce the output of the ribbon - so adding a 2 ohm res will reduce it more than adding just a 1 ohm res. Which is not generally a problem with an active XO, as you can adjust output level for each frequency band.
I have been running a 1 ohm Duelund in series with my 2 ohm IIIa/T-IVa ribbons for about 6 years, as the ss amp driving my ribbons could not handle a 2 ohm load. However, I am about to upgrade to a new amp which the designer has come out with - which can cope with a 2 ohm load. So I look forward to being able to do away with the Duelund. :-))
You can also use a Spelz autoformer to increase load which the ribbon provides, to 8 ohms. But these also degrade the sound - compared to not having one ... albeit only slightly (so I am told).
Given the minimum desirable 4 ohm load ... do you have to use a SET for your ribbons? I suggest a 50w-into-2-ohms ss amp would be a better solution.

Regards,
Andy

Edits: 02/16/15

Follow Ups:

RE: Adding series resistor for ribbon? - AkuAnkka 01:50:27 02/17/15 (7)
Well surely I don't have to use SET, but I just think that it would be a good choice from sound quality point of view.

I don't know if there are any reasonably priced SET tube amps woth 2ohms output..?
- Why do you think that a SET is a perfect choice for a ribbon? ... - andyr 02:06:30 02/17/15 (6)
  Yes, I know the mystique about SETs. And that's one of the reasons why people choose tube amps to drive Maggies. However, I have read posts here which say that tube amps (not sure whether they're SETs or P-P) don't control ribbons as well as ss amps.
  
  So maybe you need to research ss amps which can drive a 2ohm load? As I said, Hugh Dean's NAKSA 80 (down-rated slightly by having a lower DC rail - so it produces, say, 60w into 8 ohms and not 80w) can drive a 2 ohm load well. I'm sure there must be others.
  
  Regards,
  
  Andy
  - RE: Why do you think that a SET is a perfect choice for a ribbon? ... - AkuAnkka 02:18:41 02/17/15 (5)
    Unfortunately I could not find any distributor for NAKSA here in Europe, I don't know if there are any..? I would not want to order electronics all the way from Australia, due the high delivery funds, taxes, customs, difficult warranty arrangements etc. etc.
    But surely if I don't find any good way to use tube SET for ribbons (and maybe for mids also), I will look for some nice A-class SS amp or such.
    
    Edits: 02/17/15
    - RE: Why do you think that a SET is a perfect choice for a ribbon? ... - andyr 02:46:14 02/17/15 (4)
      There are no 'distributors' for Hugh Dean's amps - he supplies direct. But I suspect this is not your way of doing things. I know he has a customer in Copenhagen ... he may well have one in your country too (so you can hear it).
      
      Regards,
      
      Andy
      - RE: Why do you think that a SET is a perfect choice for a ribbon? ... - Roger Gustavsson 07:13:01 02/17/15 (3)
        
        In Reply to: RE: Why do you think that a SET is a perfect choice for a ribbon? ... posted by andyr on February 17, 2015 at 02:46:14
        
        Andy, have you done any blind testing on this? It is very difficult to run tests like that without having exactly matched levels.
        We are having a discussion on the sound of capacitors in a swedish forum right now, it is very similar. Not many have ran blind tests. In a controlled blind test things often show up differently...
        
        The sound of capacitors, eh! :-)) ... - andyr 11:25:27 02/17/15 (2)
        
        In Reply to: RE: Why do you think that a SET is a perfect choice for a ribbon? ... posted by Roger Gustavsson on February 17, 2015 at 07:13:01
        
        Hope you have your flame-proof undies on. :-)) I have no idea which larger-value caps sound the best (that you use in passive XOs) but for coupling caps (1uF - 2uF) that I use in my 'Muse' phono stage, customer's input has shown:
        * the best (that I have used) are Duelund RS400v Copper. Possibly a more expensive Duelund sounds better?
        * then - in spite of being more expensive - Sonicap Platinum
        * a long way behind ... AmpOhm PF-XAL-AL Paper-in-Oil Aluminium Foil.
        
        Regards,
        
        Andy
        
        RE: The sound of capacitors, eh! :-)) ... - Satie 12:04:16 02/18/15 (1)
        
        In Reply to: RE: The sound of capacitors, eh! :-)) ... posted by andyr on February 17, 2015 at 11:25:27
        
        The new Jupiter Cu wax cas have captured the heart of my modster friend and have displaced the Sonicap Platinums. For value I can't find better than the Dayton tin foil caps from parts express.
        
        RE: The sound of capacitors, eh! :-)) ... - andyr 14:20:03 02/18/15 (0)
        
        In Reply to: RE: The sound of capacitors, eh! :-)) ... posted by Satie on February 18, 2015 at 12:04:16
        
        Haven't tried the Jupiter Cu, Satie, but those Duelund ones I mentioned sound better than Sonicap Platinums, too. And they're cheaper!
        
        Andy

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