Home › Forums › Help/Technical Questions › Vintage (1975) Frequency Analyzer: Volume jump?

Viewing 8 posts - 1 through 8 (of 8 total)
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  • June 17, 2009 at 3:53 am #78428
    devnulljp
    Participant

    Anyone else have one of these: Ram’s Head era Frequency Analyzer?
    I just got one and there is a massive volume drop at the far end of the blend pot travel. Fully clockwise (which is, oddly, about 11 o’clock) it’s the clean signal only at normal volume; Fully anticlockwise (about 1 o’clock) it’s 100% ring mod signal but really quiet. Volume drops progressively from 100% dry to 100% wet.
    There is a trimpot inside but I haven’t messed with it. This one’s pretty clean, and almost looks like it’s never been opened — still has the (now crumbling) foam inside.

    Anyone else? Is the pot shot? Something else? Or is this normal? It’s such a weird little box, nothing would surprise me.

    [IMG]”http://i440.photobucket.com/albums/qq123/devnulljp/Vintage Effects/frequencyanalyzer/freq-analyzer-front_0001-1.jpg”[/IMG]

    Edited because I explained the problem badly.

    June 17, 2009 at 11:01 am #97993
    The EH Man
    Moderator

    Could be a bad 4558 IC.

    June 19, 2009 at 4:27 am #98143
    devnulljp
    Participant
    Quote:
    Could be a bad 4558 IC.

    Cool — all the ICs in there have the IDs scratched off though. Which one (or two) is the 4558? There are two of the right size.
    Also, I realised I totally messed up that explanation of the problem. It’s more like with the blend pot fully clockwise (11 oclock) I get full clean un-effected signal, but turning the pot leads to a progressive drop in volume along with an increase in ratio of effected signal until fully anticlockwise (1 o’clock) it’s fully effected but very very low volume. So the op-amp isn’t amplifying the effected signal?
    Will a TL072CP do in place of the NE4558N? (I have a bunch of those on hand).

    June 19, 2009 at 11:01 am #98147
    The EH Man
    Moderator
    Quote:
    Quote:
    Could be a bad 4558 IC.

    Cool — all the ICs in there have the IDs scratched off though. Which one (or two) is the 4558? There are two of the right size.
    Also, I realised I totally messed up that explanation of the problem. It’s more like with the blend pot fully clockwise (11 oclock) I get full clean un-effected signal, but turning the pot leads to a progressive drop in volume along with an increase in ratio of effected signal until fully anticlockwise (1 o’clock) it’s fully effected but very very low volume. So the op-amp isn’t amplifying the effected signal?
    Will a TL072CP do in place of the NE4558N? (I have a bunch of those on hand).

    It’s the one that has pin 1 connected to something. The other 8 pin chip is a 741 and has no connections on pin 1.

    A TL072 should work OK.

    June 19, 2009 at 5:27 pm #98151
    devnulljp
    Participant

    OK, I replaced the op-amp with a TL072 — no change.
    Two things I did notice though:
    1. When you rotate the Blend pot anticlockwise, as well as the volume dropping, there’s a buzz that comes in so that at full travel it sounds like there’s no guitar on the end of the cable. So the signal is being dropped somewhere?
    2. Is it normal for the stomp switch to only have two wires attached? There’s a blob of solder on the third lug but nothing attached and I can’t see any loose wires…
    Could it be something as simple as a bad capacitor? What wouldcause th blend to not actually blend — so the straight signal is blended with the effected signal, but in my case the effected signal isn’t really getting through.

    [IMG]”http://i440.photobucket.com/albums/qq123/devnulljp/Vintage Effects/frequencyanalyzer/op-amp_0005-1.jpg”[/IMG]
    [IMG]”http://i440.photobucket.com/albums/qq123/devnulljp/Vintage Effects/frequencyanalyzer/switch02.jpg”[/IMG]

    June 21, 2009 at 6:07 am #97919
    devnulljp
    Participant

    Anyone have one of these?
    I’m guessing the volume is supposed to stay the same regardless of 100% dry / 100% wet or anywhere in between, so something’s not right with this one.
    Anyone know about that switch? Where could my signal be going? Bad capacitor?

    June 22, 2009 at 6:36 am #98220
    devnulljp
    Participant

    Someone said this is normal behaviour for this pedal. Can that be true? I can’t imagine it being even remotely useful like this.
    No-one else have one?

    June 22, 2009 at 7:50 am #98222
    Stoner Wizard
    Participant
    Quote:
    Someone said this is normal behaviour for this pedal. Can that be true? I can’t imagine it being even remotely useful like this.
    No-one else have one?

    Hello:

    I was thinking on getting one of these via eBay, but finally I decided not to go for it. I’ve read some opinions about this but I didn’t draw any clear conclusion. I preferred not to take any risk and bought the present reissue (the latest round-knob type and cardboard pack).

    Maybe the reissue is not as “magic sounding” as the original, but at least (as I’ve tried until today) I don’t have noticed volume drop issues. I think that certain settings go over unity gain.

    I’ve found interesting when used at 100 % wet, you may tweak with the “Shift” to interact with a delay pedal set at the edge of self oscillation. It’s really piercing or booming (depending the filter is engaged or not).

    For heavy distortion, the Frequency Analyzer with the bass filter engaged is a low-end mayhem. In fact, I use it to boost distorted chords that rely on certain interval notes that make usable harmonies or unison-string chord.

    The advantage of EH big boxes is that they seem easier to work and tweak with them. Good luck!

    Regards

    Nacho

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