obbm Posted March 3, 2017 Share Posted March 3, 2017 (edited) A couple of months ago I bought a Spector CTB Fretless. It has a Fishman Piezo bridge and an Aguilar DCB soapbar through an Aguilar OBP-3 pre-amp. I have found a huge volume difference between the Fishman and the Aguilar even with the Fishman pre-amp turned down to minimum. Compared to the Fishman the Aguilar output is very very low because I have to crank the gain on the amp to get a usable volume and then back off the Fishman by more than 50%. Also the volume control on the Aguilar is acting almost as an On/Off switch because I only have to turn the pot down a few degrees and the sound has gone. Definitely something not right. Any thoughts on this? Edited March 3, 2017 by obbm Quote Link to comment Share on other sites More sharing options...
franzbassist Posted March 3, 2017 Share Posted March 3, 2017 Is it worth asking Dood? I think this is the very bass he tried out, so it would be interesting to see if he experienced the same issue. If he didn't it's probably had a knock in transit Maybe an email to Spector might help too? Quote Link to comment Share on other sites More sharing options...
obbm Posted March 3, 2017 Author Share Posted March 3, 2017 I contacted Spector and they just said turn down the Fishman, so not a lot of help. I think I'll take it up with Spector and Bass Direct at the show on Sunday. Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted March 4, 2017 Share Posted March 4, 2017 Sounds like the pot itself might be faulty. Quote Link to comment Share on other sites More sharing options...
obbm Posted March 4, 2017 Author Share Posted March 4, 2017 [quote name='MoonBassAlpha' timestamp='1488636270' post='3250654'] Sounds like the pot itself might be faulty. [/quote] Doh. I don't know why I didn't think of that. I've just had the cavity cover off and got in their with my meter and yes it's a faulty pot. Time to activate the warranty. Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted March 4, 2017 Share Posted March 4, 2017 Back of the net! Quote Link to comment Share on other sites More sharing options...
obbm Posted March 4, 2017 Author Share Posted March 4, 2017 [quote name='MoonBassAlpha' timestamp='1488645977' post='3250764'] Back of the net! [/quote] Sadly not. Explored a bit further with oscilloscope. Soapbar and volume control seem to work fine however I can hear that the control is only working over the last few degrees. Interesting as I wind the Soapbar volume control down the waveform increases in amplitude but the bass output drops off. It must be some kind of interaction between the Soapbar, the Fishman Piezo and the OBP3 pre-amp. How do you start to unravel this one? Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted March 4, 2017 Share Posted March 4, 2017 Denied!! Sorry to hear that. At what point do the signals get mixed? Could it be a phase problem? Sounds like the bass frequencies are cancelling. I wonder if flipping the soapbar polarity would be worthwhile. If your scope is dual channel you could check the phase just before the stage where they are mixed/summed. Quote Link to comment Share on other sites More sharing options...
obbm Posted March 4, 2017 Author Share Posted March 4, 2017 That was my initial thought. There is no mixing stage as such, it's the same as a 2 x vol Jazz where the pick-ups are across the pots and the sliders of the pots are joined and feed the pre-amp. It's very weird. Piezo vol at zero, soapbar at max, turn down the Soapbar vol and the sound goes down and off but the waveform goes up. Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted March 4, 2017 Share Posted March 4, 2017 According to the diagram I've Googled the pickups should be connected to the pot wipers with the feed taken from the top end of the pot (the end that isn't connected to ground) If you think about it, if both wipers are connected together, when one wiper is taken to ground they both are, there's no isolation. Quote Link to comment Share on other sites More sharing options...
franzbassist Posted March 5, 2017 Share Posted March 5, 2017 Doesn't it need a buffer? Something like [url="http://www.east-uk.com/index.php/all-products/mpm-01.html"]this[/url]? Quote Link to comment Share on other sites More sharing options...
MoonBassAlpha Posted March 5, 2017 Share Posted March 5, 2017 The Fishman and Aguilar pickups are both passive according to the Spector website. Incidentally, was any mention made of how well it functioned prior to purchase? Did it look like it had been fiddled with? Quote Link to comment Share on other sites More sharing options...
Thunderbird Posted March 5, 2017 Share Posted March 5, 2017 Sounds like some one has stitched you up with a faulty bass hope it gets sorted Quote Link to comment Share on other sites More sharing options...
obbm Posted March 5, 2017 Author Share Posted March 5, 2017 [quote name='walbassist' timestamp='1488702328' post='3251075'] Doesn't it need a buffer? Something like [url="http://www.east-uk.com/index.php/all-products/mpm-01.html"]this[/url]? [/quote] Funny you bring that up Gareth, I was talking to John about exactly this item at the show today. Quote Link to comment Share on other sites More sharing options...
obbm Posted March 5, 2017 Author Share Posted March 5, 2017 [quote name='Thunderbird' timestamp='1488732187' post='3251365'] Sounds like some one has stitched you up with a faulty bass hope it gets sorted [/quote] I don't look at it as being stitched-up. It was a brand new bass back in December, although it was made a while before then, and is serial number #9. I've no idea how many they've sold of these but it could be that this hasn't been an issue before. Quote Link to comment Share on other sites More sharing options...
obbm Posted March 5, 2017 Author Share Posted March 5, 2017 Having just got back from the Bass Show where I heard an interesting talk by Overwater's Chris May and had a long chat with John East, I decided to do some more digging around in the control cavity and searching on the net. By snipping ou the neat cable ties I've been able to establish that the Piezo is connected to a Fishman Powerchip board which is mounted on the back of the Piezo volume pot. According to info I found on the Fishman site this board supposedly includes a buffer and provides the facility to connect a magnetic pick-up and mix the two signals. The Aguilar magnetic pick-up is connected to its own volume pot and then into the Fishman Powerchip. Unfortunately there is no information about how this set-up is supposed to function. Is the Piezo volume a master volume which allows you to mix in some magnetic or should both controls work independently and the thing faulty? I've just contacted Fishman support and wait in anticipation for their answer. Quote Link to comment Share on other sites More sharing options...
ikay Posted March 6, 2017 Share Posted March 6, 2017 Hi Dave, on the Fishman website, under powerchip features it says 'Fishman-designed piezo volume control'. I'm pretty sure the Fishman vol is for piezo only. The circuit allows both signals to be mixed but the mag vol is before the circuit and functions independently to the piezo vol. Quote Link to comment Share on other sites More sharing options...
obbm Posted March 6, 2017 Author Share Posted March 6, 2017 [quote name='ikay' timestamp='1488790014' post='3251668'] Hi Dave, on the Fishman website, under powerchip features it says 'Fishman-designed piezo volume control'. I'm pretty sure the Fishman vol is for piezo only. The circuit allows both signals to be mixed but the mag vol is before the circuit and functions independently to the piezo vol. [/quote] Thanks Ian. That is what I would have expected. By my reckoning the Powerschip is therefore faulty. I must confess that Fishman's information is somewhat lacking. Quote Link to comment Share on other sites More sharing options...
franzbassist Posted March 6, 2017 Share Posted March 6, 2017 From their FAQ: [i]The function of the Powerchip is to buffer the piezo signal to better match up with the magnetic output. This impedance matching allows the piezo and magnetic signals to be mixed to a mono or stereo output, depending on the cable used. A mono cable will give you a combined piezo/magnetic signal to the tip of the output jack, and a stereo cable will give you the magnetic signal on the tip and the piezo on the ring. The Powerchip is not a blend pot, but a volume pot for the piezo only. To adjust the amount of blended piezo and magnetic signals, the Powerchip and the original magnetic volume controls must both be used.[/i] Quote Link to comment Share on other sites More sharing options...
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