Re: revibe works, but needs fine tune! John,
it's pretty simple
Tip = Reverb
Ring= Tremolo
Sleeve=ground
or ....
Tip = Tremolo
Ring= Reverb
Sleeve=ground
whatever you wire the foot switch to be, you need to make sure the jack is wired the same. Don't forget that 220Kohm resistor on the reverb return/footswitch assembly.
johnt1
Junior tube assistant
Posts: 13
(4/17/04 11:18 pm)
revibe unit Barry thanks for the reply. I believe thats what I have. I ran a white wire from V1 pin 2 to the center lug of the reverb return.then I ran the 220 k resister from the same lug to the ground of the 1/4" stereo jack. I ran a jumper from the reverb return center lug to the barrel lug of the reverb rerurn. I ran the vibrato foot switch wire from the 1 meg .01 lug over to the tip lug of the stereo jack. There is still one tab left that is in contact with the inside of the tip . should i have something on this contact.
Thanks John T.
EL34
I got your parts right here.
Posts: 2273
(4/20/04 3:56 pm)
Re: revibe unit Firing them up cold turkey works the best usually.
It's good to have a meter connected and be monitoring current levels in power tubes the first time.
Set the bias to the extreme cold side and bring the bias up slowly on fixed bias amps. Just monitor the power tube current in cathode biased amps.
Double check everything twice beforehand. If you are the sloppy type that skips steps intending on doing them later, this may not be the best method for you.
I used to gloat everytime I fired up a new amp and only heard the low hiss from the speaker. Set the bias, monitor the bias for a while and re-set it after a burn in period.
Have your hand on the power switch in case something seems wrong. Do not hessitate to shut the amp off immediately if even the smallest thing seems weird.
johnt1
Junior tube assistant
Posts: 14
(4/20/04 6:59 pm)
revibe unit Doug thanks for the reply. The unit seems basically OK. I have no idea what kind of voltages I should be looking for in the revibe unit. I believe I had about 315 v on pins 3 & 4 of the power tube. The reverb sounds good. My problem now is the vibrato. I know my pedal is good. but it has no effect on the unit. The vibrato is just on. The vibrato also seems to have a thumping sound when turned up all the way. I also am not sure how quiet the unit should be. I believe I need to make a few minor tweaks. Any advice is welcome Thanks.
John T.
EL34
I got your parts right here.
Posts: 2274
(4/21/04 9:18 am)
Re: revibe unit It's different for every amp, there is no standard.
You can just measure what you have and see if it is all working properly.
You can look at any fender layout diagram and see the voltages for your every day normal tube stages.
A 12ax7 with a 1.5 cathode resistor works the same and has approx the same cathode voltages in many amps. 1 to 2 volts.
johnt1
Junior tube assistant
Posts: 15
(4/21/04 11:34 pm)
help with my revibe ! My reverb on my revibe unit sounds great. I found the problem with the vibrato foot switch. I have one last problem. both the intensity and the speed work, but with the intensity up all the way,when the speed is past 5 the unit seems to motor boat you can hear a thumping sound. I also wonder if the vibrato should sound a little fuller. The vibrato on my revibe is not quite as pronounced as my 66 princeton. I don't know what the 5g13 should sound like.
Need advice.
Thanks john t.
johnt1
Junior tube assistant
Posts: 18
(4/23/04 10:55 am)
revibe I am not getting a consistent reading on v5 pin 6. I think the resister at 4.7 meg may be bad. Would this cause the vibrato to motor boat.
Thanks John T.
EL34
I got your parts right here.
Posts: 2276
(4/23/04 12:07 pm)
Re: revibe You won't get any meaningfull readings on a tremolo/vibrato occillator tube stage.
Forget about trying to figure out what voltages are supposed to be on a trem stage.
bnwitt
Senior tube assistant
Posts: 340
(4/23/04 1:05 pm)
Re: revibe John,
do you have the mp3 file of the Weber sponsored revibe? If not, I could email it to you so you can hear what it sounds like.
Doug,
could you do a sound file of the Hoffman Reverb/Tremolo unit?
johnt1
Junior tube assistant
Posts: 19
(4/24/04 12:50 am)
Re: firing up my revibe. What do I need to know? Barry thanks much,No I don't have that file. That might be a big help. I cant tell if my revibe is correct or not. The reverb is great. The vibrato section however, has a helicopter sound in the background when the intensity and speed are pushed past 6 or so at the same time. Dose that sound right to you. If not I would think is is something minor I have missed. I can give you my Email let me know.
Thanks John T.
bnwitt
Senior tube assistant
Posts: 343
(4/24/04 2:15 am)
Re: firing up my revibe. What do I need to know? John,
email me at bnwitt@hotmail.com and I will send you the file.
johnt1
Junior tube assistant
Posts: 20
(4/26/04 3:40 pm)
revibe unit Barry. thanks for the info. A few other observations I have made on my revibe. Lifting the ground makes no difference in the hum. Actually the unit seems a bit quieter using the ground. I also noticed the hum is there even when I turn the volume down all the way on my guitar. I tried a fender reverb with my 5e3 clone. Still had some hum but not as loud as my revibe. I did notice when using the 63 reverb that when I turned the volume on the guitar down. There was no sound at all at the amp. I also think my revibe reverb had better reverb. You have made a few revibe how much hum should I have? Should lifting the ground make a noticeable difference?
John T.
bnwitt
Senior tube assistant
Posts: 345
(4/26/04 6:38 pm)
Re: revibe unit John,
My Verbolos (what I call them) have had pretty low level hum, but definitely more than one of my amps. All of the hoffman style amps are very quiet, but the revibe is a little noisier. Lifting the ground should reduce the hum only if the hum is being caused by a ground loop between the two devices(amp and revibe). If this does not impact your noise level then it may be coming from some other problem. Here is some info from Randall Aiken's website regarding hum:
Q: How can I find out if the hum in my amp is caused by the filament wiring?
A: Disconnect the 6.3V AC wires from the power transformer, and temporarily connect in a 6V lantern battery. If the hum is caused by filament wiring, or by induction from the filament inside the tube, it will go away with the battery connected. If the hum is caused by something else, such as a ground loop, it will not go away when the filaments are run on DC.
Q: How can I get rid of the hum if it is caused by the filaments?
A: The best way to get rid of the hum is to generate a DC filament supply, but this isn't always practical, because of the high dissipation caused by the large current draw of the filaments. First, make sure the filament wires are run as twisted pairs, then make sure they aren't routed too close to sensitive grid wires or next to coupling capacitors. If that doesn't do it, try "elevating" the center tap of the filament winding (or junction of the two filament reference resistors) to a potential above the cathode voltage of the tubes, typically between 10V - 50V or so. You can generate this voltage with a couple of resistors arranged as a voltage divider from the plate supply. Be sure to bypass the junction of the resistors to ground with a suitable filter capacitor, or you may inject some buzz or noise into the amplifier from the power supply.
Q: What if the hum is not caused by the filaments?
A: If the amp still hums when a battery is substituted for the filament supply, the cause is most likely one of four things: either the AC wiring (plate supply, filament supply, or mains input) is running too close to a sensitive stage, the transformers themselves are inducing hum into sensitive stages, there is too much residual ripple on the main power or bias supplies, or there is ground loop hum caused by a poor grounding scheme in the amplifier. The true cause has to be determined by a process of elimination. Sometimes it is advantageous to pull preamp tubes, one by one, starting at the input, to determine if the hum is getting in to a particular stage."
I have built all of my units with a cap board and cap can for the filter caps and not placed them inside the chassis. I do that because the chassis is so darn tight and I don't know really if that reduces the overall noise or not. I am also using three separate chassis grounds in the unit. One for the green power cord wire, one for the preamp ground (buss wire on back of pots)like Doug shows and one for the filter caps. I think the only way to compare is for me to record my recent revibe in different settings to an MP3 file for your listening pleasure. I can also use a sound pressure meter to compare a hoffman 5E3's hum by itself to the amp with a Revibe unit in line. Give me a couple of days to do that and I'll post it on my website this weekend.
Barry
Edited by: bnwitt at: 4/26/04 6:40 pm
Topic: firing up my revibe. What do I need to k &n (Read 30665 times)