Introduction, and Weber 5H15 ReVibe build

moosie

Joined: May 24, 2014
Posts: 10
CT

Posted on May 29 2014 02:42 PM

It's the nature of activities like these, that we always "need" one more thing. I have no doubt the ESR meter is fantastic. I'm going to hold off, though, and see if I can get through this build without a problem.

If there's a troubleshooting time, when I might give up and take it to a pro, I'll get the meter first.

Normally I'd just go for it now, but it's been that way with a bunch of things the past few months.

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Hammond101

Joined: Feb 22, 2013
Posts: 342
SoCal USA

Posted on May 29 2014 05:30 PM

You will be fine checking the electrolytics for shorts with the DVOM. Enjoy your build.

—

Keep it Drippy Brothers and Sisters!

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FritzCat

Joined: Sep 11, 2007
Posts: 668
Sonoma, CA
9 Security Pins

Posted on Jul 28 2014 10:01 AM

Revibe build complete! I did it according to the 1.4 version to eliminate hum/ground loops. The vibrato sounds great, but the 'verb isn't deep enough, I have to turn the controls way higher than my ancient clone tank to get the same depth. I thought it might be due to the supplied pan (Accutronics), but I tried a new Mod pan and there was no difference. Anyone have any suggestions?

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BJB

Joined: Jul 28, 2008
Posts: 413
United States

Posted on Jul 28 2014 05:41 PM

OK, I usually run a PSpice circuit simulation before I answer these sorts of questions, but from a quick look at the schematic, this circuit appears to have some gain in the tremolo path of the circuit. Is this true? Is the guitar louder playing through the Revibe than playing straight into the amp?

If so, you can reduce R25 (68K) and increase R51 (33K) to reduce the gain of the tremolo signal. This will make the dry signal smaller and the wet signal will stand out more. As a first try, I would just swap the 33K and 68K resistors and see how that works out. You can try any values you like so long as the two resistors add up to 100K or so.

Also, make sure you are using a 6K6 and not a 6V6. I am surprised that the schematic indicates that a 6V6 will work in place of a 6K6.

—

If it ain't broke, fix it until it is.

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FritzCat

Joined: Sep 11, 2007
Posts: 668
Sonoma, CA
9 Security Pins

Posted on Jul 29 2014 09:44 PM

I am using a 6k6, and I don't notice any difference in volume without the tank, but I haven't played with it a ton yet due to time constraints. I've swapped the 6K6 as well as the 12AT7 with the ones from my regular tank and heard no difference, so the problem (if there actually is one) seems to lie elsewhere. Unless the fact that the indicator light doesn't work could affect the sound?

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tubeswell

Joined: Sep 24, 2011
Posts: 1424
Wellington, NZ
Antarctica

Posted on Jul 30 2014 02:27 AM

FritzCat wrote:

Revibe build complete! I did it according to the 1.4 version to eliminate hum/ground loops. The vibrato sounds great, but the 'verb isn't deep enough, I have to turn the controls way higher than my ancient clone tank to get the same depth. I thought it might be due to the supplied pan (Accutronics), but I tried a new Mod pan and there was no difference. Anyone have any suggestions?

I guess its also a bit to do with the 5h15 revibe having a higher output impedance than the 6g15 (due to the former not having a CF stage in parallel with the reverb recovery stage, but instead having two inverting stages, which increases the output impedance. Think of the two plate resistors (R46 and R47 in the weber schematic) in parallel with the voltage divider (R24 in the weber schematic), which is all in parallel with the load on the reverb recovery stage. Remember that the HT and the ground look one and the same to AC because of the action of the filter caps in shunting AC out of the power rail to ground). Higher AC load = more volume attenuation for the reverb recovery stage.

—

He who dies with the most tubes... wins

Surf Daddies

Last edited: Jul 30, 2014 04:41:55

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FritzCat

Joined: Sep 11, 2007
Posts: 668
Sonoma, CA
9 Security Pins

Posted on Jul 30 2014 08:47 AM

I don't know what any of that means, but it seems you're saying it's normal due to the circuit design. Everything works fine, I just have to turn up the knobs more to get the same amount of reverb. I can live with that.

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BJB

Joined: Jul 28, 2008
Posts: 413
United States

Posted on Jul 30 2014 11:49 AM

Oh, you can get the same amount of reverb by adjusting the controls? Then I would say that yes, it's caused by the circuit design.

I have to confess that I heard about the Revibe years ago but I didn't look at the schematic until last week. I was very surprised to see that the reverb and tremolo paths are in parallel and not in series. This is important because a real reverb unit and Showman amplifier would be in series, which means the reverb gets chopped up by the tremolo. Putting them in parallel means the reverb signal is always there even with the tremolo engaged. This weakens the tremolo effect especially when using a lot of reverb.

This doesn't make a lot of sense to me because the design compromises the reverb path (as you have found) and limits the tremolo intensity. So by combining the two circuits in the same box, the designer managed to make both circuits mediocre.

—

If it ain't broke, fix it until it is.

Top

tubeswell

Joined: Sep 24, 2011
Posts: 1424
Wellington, NZ
Antarctica

Posted on Jul 30 2014 01:46 PM

If you had room for another dual triode in the chassis, you could buffer the vibrato output with a cathode follower (this would decrease the AC load on the reverb recovery), and use the other triode to add another gain stage after the reverb recovery stage.

—

He who dies with the most tubes... wins

Surf Daddies

Last edited: Jul 30, 2014 13:47:04

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josheboy

Joined: Mar 13, 2009
Posts: 2351
Twin Cities, MN
United States

Posted on Jul 30 2014 01:51 PM

I wonder if this is the same (or similar) circuit as the little kahuna. Or if they use a completely different design.

I would love to build a tank (or trem/tank) as a project someday. Seems super complicated, but the end result would be awesome.

Welcome Moosie!

Top

BJB

Joined: Jul 28, 2008
Posts: 413
United States

Posted on Jul 30 2014 02:36 PM

The old Diaz Cesar Diaz Vibramaster was a Fender reverb circuit followed by an optoisolator (same as used in blackface amps) that operated on the signal being sent to the amp. So when the trem was off, the reverb operated normally, and the trem chopped the complete signal just as though you were feeding an outboard reverb tank into an amplifier with tremolo. Adding this sort of tremolo is very, very simple compared to the harmonic vibrato circuit used by the Revibe, assuming you are the sort of person who likes the choppy optoisolator tremolo.

The weird thing about the Diaz Vibramaster is that it claimed to be 'vibrato' and not 'tremolo'. I read his patent for his circuit and he claimed that the circuit generated extra frequencies that created 'vibrato'. This is not what makes vibrato but he got a patent anyway.

—

If it ain't broke, fix it until it is.

Last edited: Jul 30, 2014 14:37:14

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moosie Joined: May 24, 2014 Posts: 10 CT	Posted on May 29 2014 02:42 PM It's the nature of activities like these, that we always "need" one more thing. I have no doubt the ESR meter is fantastic. I'm going to hold off, though, and see if I can get through this build without a problem. If there's a troubleshooting time, when I might give up and take it to a pro, I'll get the meter first. Normally I'd just go for it now, but it's been that way with a bunch of things the past few months. Top
Hammond101 Joined: Feb 22, 2013 Posts: 342 SoCal USA	Posted on May 29 2014 05:30 PM You will be fine checking the electrolytics for shorts with the DVOM. Enjoy your build. — Keep it Drippy Brothers and Sisters! Top
FritzCat Joined: Sep 11, 2007 Posts: 668 Sonoma, CA	Posted on Jul 28 2014 10:01 AM Revibe build complete! I did it according to the 1.4 version to eliminate hum/ground loops. The vibrato sounds great, but the 'verb isn't deep enough, I have to turn the controls way higher than my ancient clone tank to get the same depth. I thought it might be due to the supplied pan (Accutronics), but I tried a new Mod pan and there was no difference. Anyone have any suggestions? Top
BJB Joined: Jul 28, 2008 Posts: 413	Posted on Jul 28 2014 05:41 PM OK, I usually run a PSpice circuit simulation before I answer these sorts of questions, but from a quick look at the schematic, this circuit appears to have some gain in the tremolo path of the circuit. Is this true? Is the guitar louder playing through the Revibe than playing straight into the amp? If so, you can reduce R25 (68K) and increase R51 (33K) to reduce the gain of the tremolo signal. This will make the dry signal smaller and the wet signal will stand out more. As a first try, I would just swap the 33K and 68K resistors and see how that works out. You can try any values you like so long as the two resistors add up to 100K or so. Also, make sure you are using a 6K6 and not a 6V6. I am surprised that the schematic indicates that a 6V6 will work in place of a 6K6. — If it ain't broke, fix it until it is. Top
FritzCat Joined: Sep 11, 2007 Posts: 668 Sonoma, CA	Posted on Jul 29 2014 09:44 PM I am using a 6k6, and I don't notice any difference in volume without the tank, but I haven't played with it a ton yet due to time constraints. I've swapped the 6K6 as well as the 12AT7 with the ones from my regular tank and heard no difference, so the problem (if there actually is one) seems to lie elsewhere. Unless the fact that the indicator light doesn't work could affect the sound? Top
tubeswell Joined: Sep 24, 2011 Posts: 1424 Wellington, NZ	Posted on Jul 30 2014 02:27 AM FritzCat wrote: Revibe build complete! I did it according to the 1.4 version to eliminate hum/ground loops. The vibrato sounds great, but the 'verb isn't deep enough, I have to turn the controls way higher than my ancient clone tank to get the same depth. I thought it might be due to the supplied pan (Accutronics), but I tried a new Mod pan and there was no difference. Anyone have any suggestions? I guess its also a bit to do with the 5h15 revibe having a higher output impedance than the 6g15 (due to the former not having a CF stage in parallel with the reverb recovery stage, but instead having two inverting stages, which increases the output impedance. Think of the two plate resistors (R46 and R47 in the weber schematic) in parallel with the voltage divider (R24 in the weber schematic), which is all in parallel with the load on the reverb recovery stage. Remember that the HT and the ground look one and the same to AC because of the action of the filter caps in shunting AC out of the power rail to ground). Higher AC load = more volume attenuation for the reverb recovery stage. — He who dies with the most tubes... wins Surf Daddies Last edited: Jul 30, 2014 04:41:55 Top
FritzCat Joined: Sep 11, 2007 Posts: 668 Sonoma, CA	Posted on Jul 30 2014 08:47 AM I don't know what any of that means, but it seems you're saying it's normal due to the circuit design. Everything works fine, I just have to turn up the knobs more to get the same amount of reverb. I can live with that. Top
BJB Joined: Jul 28, 2008 Posts: 413	Posted on Jul 30 2014 11:49 AM Oh, you can get the same amount of reverb by adjusting the controls? Then I would say that yes, it's caused by the circuit design. I have to confess that I heard about the Revibe years ago but I didn't look at the schematic until last week. I was very surprised to see that the reverb and tremolo paths are in parallel and not in series. This is important because a real reverb unit and Showman amplifier would be in series, which means the reverb gets chopped up by the tremolo. Putting them in parallel means the reverb signal is always there even with the tremolo engaged. This weakens the tremolo effect especially when using a lot of reverb. This doesn't make a lot of sense to me because the design compromises the reverb path (as you have found) and limits the tremolo intensity. So by combining the two circuits in the same box, the designer managed to make both circuits mediocre. — If it ain't broke, fix it until it is. Top
tubeswell Joined: Sep 24, 2011 Posts: 1424 Wellington, NZ	Posted on Jul 30 2014 01:46 PM If you had room for another dual triode in the chassis, you could buffer the vibrato output with a cathode follower (this would decrease the AC load on the reverb recovery), and use the other triode to add another gain stage after the reverb recovery stage. — He who dies with the most tubes... wins Surf Daddies Last edited: Jul 30, 2014 13:47:04 Top
josheboy Joined: Mar 13, 2009 Posts: 2351 Twin Cities, MN	Posted on Jul 30 2014 01:51 PM I wonder if this is the same (or similar) circuit as the little kahuna. Or if they use a completely different design. I would love to build a tank (or trem/tank) as a project someday. Seems super complicated, but the end result would be awesome. Welcome Moosie! Top
BJB Joined: Jul 28, 2008 Posts: 413	Posted on Jul 30 2014 02:36 PM The old Diaz Cesar Diaz Vibramaster was a Fender reverb circuit followed by an optoisolator (same as used in blackface amps) that operated on the signal being sent to the amp. So when the trem was off, the reverb operated normally, and the trem chopped the complete signal just as though you were feeding an outboard reverb tank into an amplifier with tremolo. Adding this sort of tremolo is very, very simple compared to the harmonic vibrato circuit used by the Revibe, assuming you are the sort of person who likes the choppy optoisolator tremolo. The weird thing about the Diaz Vibramaster is that it claimed to be 'vibrato' and not 'tremolo'. I read his patent for his circuit and he claimed that the circuit generated extra frequencies that created 'vibrato'. This is not what makes vibrato but he got a patent anyway. — If it ain't broke, fix it until it is. Last edited: Jul 30, 2014 14:37:14 Top

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Introduction, and Weber 5H15 ReVibe build