NAD - Fender Prosonic

Discussion in 'Amp Central Station' started by horseman308, Jun 17, 2017.

  1. jondanger

    jondanger Poster Extraordinaire

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    Agree with this.

    Good deal! I just joined the Prosonic club myself a couple months ago. It takes some time to figure these things out, but once everything starts clicking there are so many great sounds in there. I also switched the transformer leads in mine to use the 4 ohm tap and run the speakers in parallel, but didn't use a switch. That's an interesting idea.

    I have seen some debate online about that small 4.7uf cap on the main filter board. Some think that it is the result of a typo and should be another 47uf. I have one waiting to go in mine, but I really hate flipping over PCBs to replace components. I suspect the previous owner of yours did too, it looks like they may have applied a fair amount of heat to the top side of that PCB.

    Welcome to the club. You'll find a lot of love for these amps in this forum, and some folks who are very knowledgeable about them.

    Here is mine in seafoam green.

    View attachment 434860
     
    Last edited: Jun 24, 2017
  2. horseman308

    horseman308 Tele-Holic

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    Thanks. I'm definitely gonna rewire the 210 configuration to try 4 ohm in parallel and try out my 12" V30 at 8 ohm to see how I like the different speaker options.

    I've read a bit about that 4.7uf question and seen where some people put in a 10uf cap there. Since I'm a novice at amp configuration, I doubt I'll try to swap them myself, but could you (or someone) say a little about what would be different if I put in a 10uf or 47uf (or one in the middle) cap in that place.

    I always assumed that whenever you swap electrical components they had to always be the same exact value as what you take out. I see now that is sometimes true but not always. Still, I have no real sense of when it's safe to experiment and when it's not.
     
  3. Wally

    Wally Telefied Ad Free Member

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    That 4.7mfd cap is a puzzle, isn't it? IT is the filter that feeds the screen grids. Why it is not as large as the following caps is odd. When I recap, I may up that one on up to 47mfds. 10mfds is not much of a change. I don't understand why that cap is so small.
    the layout drawing on the fltler board leaves a lot of space for a bigger cap....
     
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  4. horseman308

    horseman308 Tele-Holic

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    So, forgive the ignorance, but you're clearly implying that a 47uf cap won't hurt the amp at all on that spot, and may do something beneficial (maybe) to the tone and/or function?

    If that's the case I might have that one replaced with a 47 when I get it checked out this week.
     
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  5. cntry666

    cntry666 Friend of Leo's

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    Nice
     
  6. jondanger

    jondanger Poster Extraordinaire

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    Yeah I neglected to get the tech that I took mine to recently to make that change and have been regretting not doing it. It won't hurt the amp, but you're right to be cautious messing with component values.

    Someone correct me if I'm wrong, but I think increasing that value will tighten up the bass response - although this is not a loose amp even with that 4.7uf in there.
     
  7. Wally

    Wally Telefied Ad Free Member

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    I am going to think that that cap will not have a lot to do with the low end. That is more of a function of that first stage of filtering, which are those two 100mfds/350VDC cap in series that yield a 50mfd cap at 700volts. If a person wanted tighter low end, one could increase the value of those two caps.
    As for this screen grid filter, I don' know of any reason that that cap is that small. I also don't know of any reason why it can't be larger. For instance, the AB763 calls for a 20mfd for the screen grid filter.
    It would be of great interest to hear/read an explanation as to why that cap is so small.
     
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  8. jondanger

    jondanger Poster Extraordinaire

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    Thanks for the clarification Wally.
     
  9. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    What Wally said - although mine has a newer 8 uf and I haven't changed it. Yet.

    But I did change V1 to a 12AY7 and V2 to a 5751. What a change! It sound the same as it did before - nice, beefy non-"Fender scooped mid" clean tone (closer to Marshall or Vox territory) and the gain sound is wonderful - much smoother, much more controlled, and gain 2 works far better. It clearly works as a mid control and provides a much more suable range of tones - and all the gain sounds are available at much more reasonable volume levels.

    The output stage also gets to work a bit harder, so although the sound is the same, it just sounds like "more" of what it already was.
     
  10. Wally

    Wally Telefied Ad Free Member

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    Silverface, I understand that the prevailing thought is thatbthat midrange thing is more of a "Marshall/Vox thing", but you and I know that Fender is the source for this sound....the 5F6A.
    Fwiw, a member here did a frequency graph for the 5F6A, the early big Marshall's, a BF Fender and the Vox AC-30. There was no surprise that the 5F6A and Marshall graphs were almost identical. The BF Fender had that mid-range scoop. The Vox?????. It looks almost exactly like the AB763 Fender. If the Vox AC-30 were fixed biased, people might better understand the similarities....or if a person were to put cathode bias on an AB763 circuit.....one would hear that earlier distortion which makes people think that the Vox is very different from the BF Fender.
     
  11. Tonemaster

    Tonemaster Tele-Afflicted

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    I paid 6600 for mine, which was origionally a head. Previous owner built this beautiful pine cab, with single 12". I replaced with a Heritage Greenback, and I am diggin this amp. Covers a lot more bases, and is a bit easier to lug than my Super. Nothing will replace that amp Though. Two keepers fersure.
     

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  12. horseman308

    horseman308 Tele-Holic

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    That's a great looking amp! Did you mean $600?

    I tried a V30 in mine for a while and found that I preferred the 2x10 set up. Then, a Greenback is a whole different animal. I bet it sounds awesome.

    Sent from my SM-G930P using Tapatalk
     
  13. Tonemaster

    Tonemaster Tele-Afflicted

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    Yes....LOL...600! Got tonme comps all night last night!
     
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