Neovibe debug

[SteveB]

On the Smallbear issue, I just wanted to pass along the info for the sake of completeness. I've got nothing but good things to say about Steve and the rest of the Smallbear gang.

Now that my Neovibe is sounding good, I want it to sound great. I seem to be missing some complexity in the vocalization.  The clips provided by John Lyons (thanks John!) have a ye-wow ye-wow ye-wow sound, where mine just goes wow-wow-wow.

John's clips: http://www.diystompboxes.com/smfforum/index.php?topic=54665.0
Mine: http://www.aronnelson.com/gallery/main.php/v/yodude/NeovibeDebug_02.mp3.html

John's recording is of SteveB's Neovibe.  Downthread, SteveB describes some mods.  Is this where the difference lies?

I have a 10k resistor in place of the 4k7 that is connected to the base of the bulb driver. 47k was too subtle, & 4k7 was too choppy for me.

I think he's talking about R49. I tried jumpering it and putting a 47k in parallel with it with no noticeable effect.

Thanks, but I think yours has better phase cancellation than mine, which is a good thing.
You may want to try increasing the bulb bias resistance with the trimpot & see what that sounds like.

I changed R49 back to 4k7 when I changed to reflected light as opposed to direct light. See link below.


http://www.diystompboxes.com/smfforum/index.php?topic=69303.0

Steve

[AppleScrappler]

just for the record, i built two neovibes and they both had the same issue with distortion and i was unable to solve the problem until reading this thread.  i switched out Q1 Q2 and Q3 which were 5088's with 3904's and the problem went away.  the 5088's i had WERE NOT from small bear but fairchild 5088's from mouser.  small bear is a very credible business and i just think that some brands of 5088's may not be right for the job of those positions and he may be selling some of those.  i have the same 5088's in all of the other positions except the bulb driver (Q13), where i also have a 3904, and they work just fine.

also, to say that it's one bad batch is probably not the case either because i built these 2 vibes a year apart and just recycled an old invoice from mouser for most of the parts - including transistors - for the newer one.  so i got the same brand but most likely not from the same batch

so if you're looking to build the neovibe for the first time and are confused at all it's probably SAFEST to just use 3904's for those tranny positions or even for the entire build as is noted in the neovibe text as an option:

"The transistor selections for the 'Vibe clone are not critical. I used all 2N3904's in my first one, and a mixture of 2N5088 and
2N5210 in my second one. The 2N5210 and 2N5088 are good all-round choices. The only transistor which really needs to be
different is the lamp driver transistor (3904) which needs to handle higher currents."

thanks for the thread guys!  it really helped me solve a frustrating problem for what was and is my favorite effect.

[ottomahn]

Just like to confirm another bug/debug due to the same issue.   

i built my neovibe using fairchild 5088's (from mouser), the effect distorted in a bad way.  swapped out Q1, Q2 and Q3 for 3904's and the problem went away

thanks for the info guys!