Build Your Own Clone Message Board

It is currently Fri Mar 29, 2024 12:28 am

All times are UTC - 6 hours




Post new topic Reply to topic  [ 25 posts ] 
Author Message
PostPosted: Sat Aug 13, 2022 9:10 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
My nephew recently built a 5E3 amp using a Hoffman Amps turret board and the info found on the Rob Robinette web site and has run into a problem. He chose to build the version where the Normal channel gets replaced with a Lead Channel and added a pre-phase inverter Master Volume. The amp seems to be working but the MV is acting up and I'm not sure exactly what to do. When the MV is turned all the way down it mutes the amp completely. I have no experience with this amp and have no idea if this is normal or not. Another issue is that when playing thru either channel the MV will make a POP when you dime it and it lowers the sound level. Not sure if it mutes or not. I'll have to call him to go over the details again with him. When you have either channel's volume turned up all the way, even if you're not using that channel, the MV will not make the popping sound when you dime it. Any thoughts or suggestions?

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Sat Aug 13, 2022 9:15 am 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
Got a schematic of the modded circuit?

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
PostPosted: Sat Aug 13, 2022 9:51 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Hoffman board, schematic, layout, etc.
https://el34world.com/Hoffman/files/Hoffman_5E3.pdf

Robinette site
https://robrobinette.com/5e3_Modifications.htm

Master Volume mod
https://robrobinette.com/5e3_Modificati ... ter_Volume

Lead Channel mod
https://robrobinette.com/5e3_Modificati ... ad_Channel

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Sun Aug 14, 2022 5:18 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
We were able to correct the amp's muting when the MV is turned all the way down. Turns out lug 1 of the MV pot was connected to the wrong side of the 56k resistor. Still haven't figured out why it pops when turned all the way up. When the MV is dimed it cuts the signal and causes a humming sound of it's own.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Sun Aug 14, 2022 11:31 am 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
Stephen wrote:
We were able to correct the amp's muting when the MV is turned all the way down. Turns out lug 1 of the MV pot was connected to the wrong side of the 56k resistor.

Ah, that makes sense! After looking at the schemo, I could see that the MV would affect both channels but the muting when down all the way didn't seem to jibe with a 56K resistor between the pot's lug 1 and ground. But connected directly to ground? Yeah, that would do it!

Re: the pops, signal loss & humming, I'll leave that one to the amp experts here. One question--have you tried a different pot there, just to eliminate the possibility of a bad one?

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
PostPosted: Mon Aug 15, 2022 3:01 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Swapping out the pot was the first thing Vince tried. No love there. I need to learn to wear my glasses when I do this sort of stuff. I must have looked at the problem half a dozen times before I put on my glasses and it jumped right out at me. Vince also tried reinstalling the 1M resistor to try the Train Wreck post phase inverter MV and it didn't work at all. I have a feeling there is an error in the schematic on the Robinette site.

Here is the schematic used to install the TW MV:
Image

Then I looked at the diagram below and if I'm not mistaken it has different connections. As best as I can tell the pot should be connected to the left side of the 1.5k resistors shown in the schematic above. Or between the 220k and 1.5k resistors shown in the diagram below.

https://robrobinette.com/images/Guitar/ ... me_Mod.png

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Mon Aug 15, 2022 12:03 pm 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
According to the wiring diagram, it should be connecting to the 220k resistors.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Mon Aug 15, 2022 1:46 pm 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Vince removed the pre PI MV and reinstalled the 1M resistor. He then installed the post PI MV with the connections made to the other side of the 1.5k resistors and still no joy. He spun the pot from one extreme to the other and heard no difference in tone or distortion.

Edit: Turning the MV fully CCW mutes the amp.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Mon Aug 15, 2022 4:59 pm 
Offline
Moderator
User avatar

Joined: Wed Apr 26, 2006 5:14 pm
Posts: 8659
Location: Truckee, CA
That type 3 MV relies on signal cancellation to do it's thing. That sort of relies on the phase inverter being balanced. The 5E3 uses a cathodyne phase inverter which is typically not balanced very well - you've got one half of the signal coming out of the plate and the the other inverted half coming out of the cathode at a different impedance and they try to balance those two signals by matching the plate and cathode resistors then playing with local feedback and that 1.5k resistor on the cathode. So, if the PI isn't balanced and you combine the two signals with a 1M pot, you're bound to get plenty of weirdness instead of a smooth volume control.

I've installed the PPIMV in a bunch of amps and it's never not worked well for me. It's more complicated with a dual pot and two more coupling caps, but it works.

https://robrobinette.com/images/Guitar/5E3P_Build/5e3_PPI_Master_Volume_Mod.png

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 2:45 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Thanks for chiming in Morgan. I'll forward this info on to Vince. The pre PI MV works but not very well IMO. The post PI MV? Pass! Personally I don't care much for this amp. Too many quirks. Adjusting the Bright channel, while playing thru the Lead channel, actually turns the volume down when it's dimed. Then there's the Tone control that stops being a tone control once you turn up the volume high enough. I asked Vince why he even chose to build it and he said he liked what he read about it. I've watched a few videos and I wasn't impressed much. I'd much prefer the 5F1 Champ with a few mods.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 10:54 am 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
VVRs work pretty good in cathode biased amps. Might be a better option once you get the amp working properly sans MV.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 11:26 am 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
byoc wrote:
VVRs work pretty good in cathode biased amps. Might be a better option once you get the amp working properly sans MV.

This is exactly what I added to my BYOC Tweed Royal, as described in detail here: viewtopic.php?p=377749#p377749 Installed almost 10 years ago and still working perfectly, and I use this amp A LOT (AAMOF, I'm plugged into it right now as I type this!) Unfortunately, the Mini-Watt VVR unit I bought from SkipzCircuits.com is no longer available, but I would guess that there are other alternatives out there.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 12:42 pm 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
duhvoodooman wrote:
byoc wrote:
VVRs work pretty good in cathode biased amps. Might be a better option once you get the amp working properly sans MV.

This is exactly what I added to my BYOC Tweed Royal, as described in detail here: viewtopic.php?p=377749#p377749 Installed almost 10 years ago and still working perfectly, and I use this amp A LOT (AAMOF, I'm plugged into it right now as I type this!) Unfortunately, the Mini-Watt VVR unit I bought from SkipzCircuits.com is no longer available, but I would guess that there are other alternatives out there.


It's a pretty simple circuit. I'm sure you could mount a terminal strip and point-to-point it relatively easily.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 12:48 pm 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
https://www.trinityamps.com/docs/VRMBuildersGuide3.pdf

They're calling it a VRM here, but pretty much all the info you need is here.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Tue Aug 16, 2022 1:21 pm 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
And they sell their VRM kit here ($47): https://www.trinityamps.com/product/vol ... odule-vrm/

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
PostPosted: Wed Aug 17, 2022 7:12 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Parts are on order. We'll see next week how things turn out.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 8:59 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Vince installed the post PIMV and it doesn't work either. The amp passes signal just fine but twisting the MV knob does nothing. At least the pre PIMV sort of worked until you dimed it which caused a pop and then muted the amp. I'll take a look at the amp when I get the chance. OTOH, I found a VVR I assembled years ago but never got to try it. We may have to give that a go next.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 10:54 am 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
I'm sure I could be mistaken about this, but when multiple proven mods won't work, that would seem to point to the fault being somewhere in the amp, not the mods.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 11:31 am 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
duhvoodooman wrote:
I'm sure I could be mistaken about this, but when multiple proven mods won't work, that would seem to point to the fault being somewhere in the amp, not the mods.


Yeah. Have you gotten the amp working without any sort of MV mod yet?

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 11:53 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
The amp works fine without a MV installed. With this latest post PIMV installed the amp still works. The MV however has no effect on the sound. The pre PIMV he tried first worked better once he connected it to the correct side of the 56k resistor. It's at the other end of the MV pot's rotation that problems occur. If you're plugged into the Bright channel and have the Lead channel's volume dimed the MV does not pop when maxing it out. If you plug into the Lead channel and have the Bright channel's volume all the way up the MV still does not pop. However when you play without the opposite channel's volume dimed the MV will pop if you turn it all the way up.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 12:07 pm 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
Now that I think about it, I can't say I've ever tried any sort of PPIMV on a cathode biased amp. Maybe they just don't work super great, much in the way VVR just don't work that great with fixed bias amps.

Maybe go with a more simple MV by replacing the 1M resistor that biases the PI with an A1M pot. The ability to reduce PI distortion actually sounds intriguing.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Tue Aug 23, 2022 5:59 pm 
Offline
Moderator
User avatar

Joined: Wed Apr 26, 2006 5:14 pm
Posts: 8659
Location: Truckee, CA
If you look at the schematic for the PPIMV, it's just a volume control that is located between the coupling caps after the phase inverter and the grid resistors. You turn it CCW and it dumps signal to ground (well, ground on cathode biased amps; negative DC on fixed bias amps). It's a dual pot since post phase inverter there are two signal paths to control. Seems like there's not really anything there to not work unless it's not installed correctly. I've installed them on 5E3's and they work great.

Image

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker


Top
 Profile  
 
PostPosted: Wed Aug 24, 2022 11:39 am 
Offline
Site Admin
User avatar

Joined: Sun Jan 22, 2006 1:39 pm
Posts: 5984
Location: Richland, WA
Morgan wrote:
If you look at the schematic for the PPIMV, it's just a volume control that is located between the coupling caps after the phase inverter and the grid resistors. You turn it CCW and it dumps signal to ground (well, ground on cathode biased amps; negative DC on fixed bias amps). It's a dual pot since post phase inverter there are two signal paths to control. Seems like there's not really anything there to not work unless it's not installed correctly. I've installed them on 5E3's and they work great.

Image


Seems simply in theory. I have two ideas why Stephen's mod might not be working quite right. Maybe one of the two dual gang pots are wired backwards? So as you turn the knob, the overall volume would aways stay the same. The other is that maybe the output tubes need to be matched within a certain tolerance. Typically, output tubes for a 5E3 aren't matched at all. Maybe you got a set that are really different.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com


Top
 Profile  
 
PostPosted: Sat Aug 27, 2022 6:23 am 
Offline
Moderator
User avatar

Joined: Sat Mar 04, 2006 9:15 pm
Posts: 7662
Location: Ohio
Well we returned the amp to stock and once again it is working as designed. I'm personally still not a fan of how the channels interact with each other but then again it's not my amp. I installed the VVR and we're both pleased with the results. I just wish I hadn't taken so long to actually try this thing before now. I am at a loss as to why the different MVs we tried didn't work. No matter, the amp works and sounds great.

_________________
"It’s your soldering."


Top
 Profile  
 
PostPosted: Sun Aug 28, 2022 12:10 pm 
Offline
Moderator
User avatar

Joined: Tue Jan 02, 2007 1:24 pm
Posts: 16196
Location: Albany, NY
Glad to hear that the VVR is working well with the circuit. That certainly coincides with my own experience on the BYOC Tweed Royal, basically a modified 5E3 circuit.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 25 posts ] 

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group