diagramAk.png
Hi guys, building the tremolo/normal 18 watt and would like to eliminate both low inputs. It looks simple to me but can this be done? ThanksEliminate both low inputs?
Moderators: CurtissRobin, colossal, zaphod_phil, Daviedawg, Graydon
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Eliminate both low inputs?
Hi guys, building the tremolo/normal 18 watt and would like to eliminate both low inputs. It looks simple to me but can this be done? Thanks
You do not have the required permissions to view the files attached to this post.
0 x
- Crabman
- Newbie
- Posts: 39
- Joined: Thu 10/28/10 2:00 am
- Location: Sudbury, Ontario
Re: Eliminate both low inputs?
Absolutely it can be done. In fact it will your life easier since wiring those dual inputs is a pain.
You just need to decide what value of grid stopper you want to use and solder it right to the grid pin on the tube socket. Use shielded wire for the input and be sure to ground the shielding at the appropriate point on the cliff jack (if that is what you are using).
You just need to decide what value of grid stopper you want to use and solder it right to the grid pin on the tube socket. Use shielded wire for the input and be sure to ground the shielding at the appropriate point on the cliff jack (if that is what you are using).
3 x
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Re: Eliminate both low inputs?
Thank you sir. Now I'll scour the posts on grid stoppers. For me this is a great education and I thank all you pro's who take the time passing on the info.Crabman wrote: ↑Sat 10/27/18 2:34 pmAbsolutely it can be done. In fact it will your life easier since wiring those dual inputs is a pain.
You just need to decide what value of grid stopper you want to use and solder it right to the grid pin on the tube socket. Use shielded wire for the input and be sure to ground the shielding at the appropriate point on the cliff jack (if that is what you are using).
1 x
- Crabman
- Newbie
- Posts: 39
- Joined: Thu 10/28/10 2:00 am
- Location: Sudbury, Ontario
Re: Eliminate both low inputs?
When considering the original 18W schematics, it would appear that no grid stopper was used on the original 18W normal channel. My opinion on this would be to use a grid stopper since it will help prevent picking up radio signals. If you consider the original schematic, the Hi input on the tremolo channel will see two 68K resistors in parallel when you plug into that jack (if I remember correctly). This will produce a 33K resistance in series with the grid. So to reproduce this you could just use 33K grid stoppers on both the normal and tremolo inputs.
If you need to know why this value of resistor is commonly used we can certainly get into that discussion.
If you need to know why this value of resistor is commonly used we can certainly get into that discussion.
1 x
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Re: Eliminate both low inputs?
Here is the diagram from TubeDepot(which I now regret using)of the 2-68k. Please continue how you would do this. Thank you kindly for your time.Crabman wrote: ↑Tue 10/30/18 8:28 pmWhen considering the original 18W schematics, it would appear that no grid stopper was used on the original 18W normal channel. My opinion on this would be to use a grid stopper since it will help prevent picking up radio signals. If you consider the original schematic, the Hi input on the tremolo channel will see two 68K resistors in parallel when you plug into that jack (if I remember correctly). This will produce a 33K resistance in series with the grid. So to reproduce this you could just use 33K grid stoppers on both the normal and tremolo inputs.
If you need to know why this value of resistor is commonly used we can certainly get into that discussion.
You do not have the required permissions to view the files attached to this post.
0 x
-
- Verbose poster
- Posts: 1118
- Joined: Mon 01/04/16 3:52 pm
Re: Eliminate both low inputs?
hello Carl,
are you building the tube depot kit? i.e. turret board etc or just showing the layout.
i think you'll need to use a 68K for the tremolo input,dropping to 33K will increase the signal slightly which might cause problems.but you could use 10 to 33K on the normal input and use sheilded cable from both jacks with the resistors on the tube sockets.
are you building the tube depot kit? i.e. turret board etc or just showing the layout.
i think you'll need to use a 68K for the tremolo input,dropping to 33K will increase the signal slightly which might cause problems.but you could use 10 to 33K on the normal input and use sheilded cable from both jacks with the resistors on the tube sockets.
You do not have the required permissions to view the files attached to this post.
0 x
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Re: Eliminate both low inputs?
Thank you for the diagram. I started using the TubeDepot instructions, layout, diagrams etc. for reference because it was free and seemed the most complete thing out there. The 68k's are on the board but I presume I can remove them, bypass the board and attach directly to the tube with one 68k(shielded cable)?geoff 1965 wrote: ↑Fri 11/02/18 8:43 pmhello Carl,
are you building the tube depot kit? i.e. turret board etc or just showing the layout.
i think you'll need to use a 68K for the tremolo input,dropping to 33K will increase the signal slightly which might cause problems.but you could use 10 to 33K on the normal input and use sheilded cable from both jacks with the resistors on the tube sockets.
HI INPUT.jpg
0 x
-
- Verbose poster
- Posts: 1118
- Joined: Mon 01/04/16 3:52 pm
Re: Eliminate both low inputs?
okay so if they are already on the board you could go from the input jack to T22 and jump the wire across to T20,or you could remove T20 resistor and replace T22 with a 33K this will equal the 2 68K's in parallel like crabman said.you could use normal wire for this way but if you wire from the jack to the tube like the diagram you'll need sheilded cable with a 33K resistor.
just a couple of notes regarding the tubedepot amp!
1st if you fit the PPIMV don't follow the wiring diagram shown,it's wrong.
2nd is Josh pointed out there is no B+ bleed resistor so you might want to fit one,use a 2W metal film 220K soldered between the first + and - terminals on the can capacitor.
just a couple of notes regarding the tubedepot amp!
1st if you fit the PPIMV don't follow the wiring diagram shown,it's wrong.
2nd is Josh pointed out there is no B+ bleed resistor so you might want to fit one,use a 2W metal film 220K soldered between the first + and - terminals on the can capacitor.
1 x
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Re: Eliminate both low inputs?
Wow...if there is that much wrong with TubeDepot, I'm thinking maybe I should start over. I've only half the board assembled but if it's faulty I'd rather trash it because this won't be my only build. Thanks for the info.geoff 1965 wrote: ↑Sat 11/03/18 8:20 amokay so if they are already on the board you could go from the input jack to T22 and jump the wire across to T20,or you could remove T20 resistor and replace T22 with a 33K this will equal the 2 68K's in parallel like crabman said.you could use normal wire for this way but if you wire from the jack to the tube like the diagram you'll need sheilded cable with a 33K resistor.
just a couple of notes regarding the tubedepot amp!
1st if you fit the PPIMV don't follow the wiring diagram shown,it's wrong.
2nd is Josh pointed out there is no B+ bleed resistor so you might want to fit one,use a 2W metal film 220K soldered between the first + and - terminals on the can capacitor.
0 x
-
- Verbose poster
- Posts: 1118
- Joined: Mon 01/04/16 3:52 pm
Re: Eliminate both low inputs?
hello Carl,
there's been a few posts with tubedepot builds with good results! i was just pointing out a couple of issues to take into account.have a browse through the forums downloads,there is a good selection of schematics & layouts to consider if your not happy with the tubedepot.
there's been a few posts with tubedepot builds with good results! i was just pointing out a couple of issues to take into account.have a browse through the forums downloads,there is a good selection of schematics & layouts to consider if your not happy with the tubedepot.
1 x
- JMPGuitars
- Super Duper Admin
- Posts: 3955
- Joined: Tue 09/18/12 8:00 pm
- Location: South Central, MA
- Contact:
Re: Eliminate both low inputs?
The layouts and schematics on this site are the best / most vetted you can work with. Whether you trash the current build is up to you, but for the next build I would switch to something from 18watt.com.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale
Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info
Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
Items for Sale
-
- Unrated
- Posts: 11
- Joined: Tue 02/27/18 7:30 pm
- Location: Midwest
- Contact:
Re: Eliminate both low inputs?
Tell you what the JMP drawing is the best I've seen. I'm going to take a parts inventory and compare to the Trem amps here and decide.Thanks again guys.
The layouts and schematics on this site are the best / most vetted you can work with. Whether you trash the current build is up to you, but for the next build I would switch to something from 18watt.com.
2 x
- crgfrench
- Frequent poster
- Posts: 827
- Joined: Fri 04/27/18 3:02 am
-
- Verbose poster
- Posts: 1118
- Joined: Mon 01/04/16 3:52 pm
Re: Eliminate both low inputs?
yep i agree, can't wait to see JMP's "beautiful" layout & schematic of the superlite el34!!
1 x