Vibrato unit just finished

tubeswell · Post by **tubeswell** » Sat Dec 17, 2011 5:03 am

Haven't fired it up yet - (had to post pics first) need time to take breath - only finished it 10 mins ago.

Developed on a theme started by Steve Luckey over at the Hoffman forum a few months back. This one has a bypass switch that makes the unit function as a tube booster when the vibrato is not on. Also has a CF bypass to get a plain ole 'uneffected' sound. Hopefully I won't have too much troubleshooting ahead (touch wood)

selloutrr · Post by **selloutrr** » Sat Dec 17, 2011 5:09 am

Very cool can't wait to hear it!

Reeltarded · Post by **Reeltarded** » Sat Dec 17, 2011 5:22 am

omg it's more complicated than that ladder in a univibe! My head hurts! It looks great!

So, it's a real vibrato? umm.. hurry I wanna hear.

There is this Magnatone circuit that we all need to build as an insert. What a wonderful sound that thing. Sounds like a waterfall in a Mentos commercial.

leadfootdriver · Post by **leadfootdriver** » Sat Dec 17, 2011 12:25 pm

Wow, you really packed in the components.

Looks great.

martin manning · Post by **martin manning** » Sat Dec 17, 2011 1:18 pm

Looks really good! What does it do? Is there a link to a schematic and or discussion that you can post?

M Fowler · Post by **M Fowler** » Sat Dec 17, 2011 2:57 pm

The wall paper appears to have been incorrectly applied, oh we talking amps here

That vibrato/booster unit looks great Pete! I will look forward to hearing your recording, great job. Rather large unit isn't it.

Mark

tubeswell · Post by **tubeswell** » Sat Dec 17, 2011 4:33 pm

Oops! forgot the schematic sorry.

The unit uses a saturable reactor from a hammond organ, which is a kind of triple transformer array with one side of each of the three transformers wired in series with the other two and fed by an oscillator. The other sides of the transformers are utilised in feedback loops from the 12AU7 triodes. There are 4 sigma (phase shift/pitch/harmonic) controls (one for each 12AU7 triode), a feedback control, an output/bypass mixing control and the LFO controls. The unit is driven by 2 x 12AU7, 2 x 12AX7 and a 12DW7. There is a CF bypass so you can run the unit un-effected by turning down the output level control, which is wired with a dual gang pot that also serves and the 'dry' mix control when turned down.

Yes it was a tight fit, but I didn't want to make it any bigger

. The unit is head sized to sit on a stack easily.

I had it going last night with only one minor trouble shoot (wired the CF bypass plate and cathode the wrong way - those CF get me every time dammit). Otherwise it seems to be working fine.

Only delved into the tip of sounds so far but got several variations ranging from chorus to phase to vibrato to tremolo by tweaking the 4 sigma controls, and many variations in between. There are a few settings that sound quite magnatone-ish. I need to get a few .mp3s done.

Structo · Post by **Structo** » Sat Dec 17, 2011 5:12 pm

Nice!

I do see a bad solder joint on an eyelet on the blue electrolytic cap near the end of the board.

tubeswell · Post by **tubeswell** » Sat Dec 17, 2011 5:17 pm

Structo wrote:Nice!

I do see a bad solder joint on an eyelet on the blue electrolytic cap near the end of the board.

I'll pick that up next time I'm tweaking with it.

martin manning · Post by **martin manning** » Sat Dec 17, 2011 5:38 pm

So this is like the Hammond vibrato?

tubeswell · Post by **tubeswell** » Sat Dec 17, 2011 6:08 pm

Yeah basically

Phil_S · Post by **Phil_S** » Sat Dec 17, 2011 7:36 pm

Very pretty work. You can build for me any time.

Just curious about all the shielded cable at the pots...just too much stuffed into a small place to chance it with plain wire?

tubeswell · Post by **tubeswell** » Sat Dec 17, 2011 10:52 pm

Phil_S wrote:Very pretty work. You can build for me any time.

Just curious about all the shielded cable at the pots...just too much stuffed into a small place to chance it with plain wire?

There is only one bit of actual shielded cable near there. The other stuff is just the mixing resistors (for the 'sigma' pots) covered in plastic insulation and 'overdone' in shrink-wrap, all tied to the same terminal tag. It looks messy I agree: in hindsight I may have been overcautious, but as it is merely a prototype I felt okay with a little crazy

tubeswell · Post by **tubeswell** » Sun Dec 18, 2011 6:38 am

Did some very rough sounds earlier this avo into garbageband not properly mic'd (mac built-in mic) and didn't get time to run through all the sounds, will try and find time later in the week. Guitar is a strat. Other amp is my PR clone. Please excuse the shoddy playing

Links follow:

http://music-electronics-forum.com/atta ... -buggy.mp3

http://music-electronics-forum.com/atta ... or-sky.mp3

http://music-electronics-forum.com/atta ... d-vibe.mp3

http://music-electronics-forum.com/atta ... y-vibe.mp3

martin manning · Post by **martin manning** » Sun Dec 18, 2011 11:50 am

Sounds good! I Googled around on this subject and found the background info, if anyone wants to read more about the circuit: http://home.comcast.net/~seluckey/amps/ ... arbler.htm There are more clips there, and links to other experiments with these units. Interesting stuff.

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