OTL Asylum

balanced input on that would be easy. nt

208.42.140.159

Ralph

In Reply to: RE: This is hypothetical..., posted by Lew on May 10, 2012 at 15:04:55

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Follow Ups:

RE: balanced input on that would be easy. nt - Lew 16:28:10 05/11/12 (12)
The input stage is very complex, to my eyes. But I am not comfortable with SS schematics. I have attached a copy. I have a better one here but it is not digitized. For sure I see there a complex equalizer network.

Edits: 05/11/12
- can we get just a tad more to the left in that photo? nt - Ralph 12:14:30 05/15/12 (8)
  -
  - Here you go... - Lew 19:24:52 05/15/12 (7)
    Hope this is better, so you can see the input, I presume. I have no idea why it comes out so small; the file should be identical to the other in all respects. Part of it includes, I think, a crossover and amplifier for the woofer, all of which I will throw away.
    
    Edits: 05/15/12
    - much better - Lew 19:37:51 05/15/12 (6)
      see here
      - And more better - Lew 19:38:52 05/15/12 (5)
        
        In Reply to: RE: much better posted by Lew on May 15, 2012 at 19:37:51
        
        Here.
        
        RE: And more better - Ralph 08:31:56 05/16/12 (4)
        
        In Reply to: RE: And more better posted by Lew on May 15, 2012 at 19:38:52
        
        I think you could apply the inverted signal to the base of Q2 using a coupling cap and a series resistor of about 15K. Sure is a lot of EQ in this thing!
        
        RE: And more better - Lew 11:43:56 05/16/12 (3)
        
        In Reply to: RE: And more better posted by Ralph on May 16, 2012 at 08:31:56
        
        Why, I wondered, do they use that series resistor? I had a hunch it is to create a hi-pass filter in combination with a parallel capacitance, but why choose such a hi-value R, when it might be more efficient to use a lo-value R and a correspondingly higher value of C? If you selected a 15K resistor, would you then also halve the value of the R in series with the input of the pos half of the drive signal? (It's 33K, I think. Did not consult the schematic.) Also, wouldn't you have to mess with the ground connections?
        
        RE: And more better - Ralph 12:22:07 05/16/12 (2)
        
        In Reply to: RE: And more better posted by Lew on May 16, 2012 at 11:43:56
        
        Yes, one of those things that the designer is not around to ask about. You shouldn't have to mess with grounding.
        
        Designer = Roger Modjeski - Lew 12:40:33 05/16/12 (1)
        
        In Reply to: RE: And more better posted by Ralph on May 16, 2012 at 12:22:07
        
        Rumors of his death are exaggerated, to paraphrase Mark Twain.
        However, I have heard that he is reluctant to comment on this schematic. He sells upgrades to these amplifiers, or so it is said. In an interview with respect to the history of Beveridge speakers and the writing of a Harold Beveridge bio, Mr. Modjeski was reported to say that this was one of his very first designs and that he and Beveridge parted company very soon thereafter.
        
        Perhaps I can draw up what I think you mean, and you can comment.
        
        RE: Designer = Roger Modjeski - tyu 05:23:09 06/11/12 (0)
        
        In Reply to: RE: Designer = Roger Modjeski posted by Lew on May 16, 2012 at 12:40:33
        
        Lew an others
        Maybe we can move back here....for other so if thay run into the SL mod in tiime... thay can get some info.... or what ever ...
        To Me it looks like Jim got it right with Acoustat "befor c mod" as for geting the best output out of the high frc. tranfourmers
        
        But i gess Dr. west an jim were facet with people needing to driver these ESL at full output...so this led to the C mod an the setup on the soundLabs.... like thay gave up the best sound for the most sound output..
        
        look can any one give just a drawing of the SL setup
        
        Some of the best sound so far with the Acoustats.. with this setup..the M60s do sound good..
        the 60years old pr of Dynaco MK3s...with the Stock 60years old tubes 6550 GEs...an a 6AN8...this is sweet as honey...an it well drive you out of the room...it louad...best highs i have ever got out of any ESL to date...
        
        So were looking at 6 days i had this mod in an i still have to get up in the morning an see if the sound is still there...may be the output tranfourmer on the MK3 match the tranfourmers in the Acoustats interfaces but it work great...Thanks for any input on geting good sound out of OTLs an ESL....goodluck
- RE: balanced input on that would be easy. nt - tyu 07:58:37 05/12/12 (2)
  Lew i think your looking at about 10kv...to get a Amp for the soundLabes.
  It not going to happen...Balanced of not...goodluck
  - RE: balanced input on that would be easy. nt - Lew 10:26:41 05/12/12 (1)
    Tyu, I don't want a direct-drive amp for my Sound Lab. I am happy with what I've got. I've tried to make that clear a few times.
    
    I posted the schematic for the Beveridge amplifier (+/-3200V) for Ralph's benefit. And yours if you are intellectually curious to look at it. The Beveridge amplifier topology is not at all applicable to driving any other commercially available ESL, because they put signal voltage on the diaphragm, not the stators (or maybe both). The Bev speakers have no separate bias supply per se.
    - RE: balanced input on that would be easy. nt - tyu 11:58:08 05/12/12 (0)
      An i thank you for your post an pic....post any thing you have too do with ESLs or OTLs...vary cool

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