‘83 Fender Concert Converted to ODS w/ Reverb

[jamaio]

I bought this amp 9 months ago with the intention of modding it to get a better sound. It’s a 60w 2 channel 1x12 with channel switching. It has the 200 watt EV speaker upgrade. It’s one of the last hand wired amp models, before everything went to printed circuit boards. It was Fenders attempt at making a high gain amp. The clean channel sounds ok but it could be better. The gain channel is very bad.

When I got the amp, channel 1 had very low volume, channel 2 worked as expected but the gain leaves much to be desired. I do not have the foot switch so channel switching can only be done by pulling the volume knob to enable channel 2. I fixed the issue with channel 1 by cleaning the foot switch jack, the circuit to channel 1 is completed when the jack is shorted. Once both channels we’re working I recapped the amp, cleaned all pots, jacks and tube sockets.

The eyelet board layout is spread out more than other Fender models, my guess is they were trying to prevent noise on the high gain channel.

I would like to improve the sound and keep channel switching. Better clean on channel and better gain on channel 2.

https://el34world.com/charts/Schematics/files/Fender/Fender_concert_ii_83.pdf

https://ampwares.com/amplifiers/fender-concert-ii/

[tubenit]

IF it were mine,  I'd change every 12AX7 cathode cap in the signal chain (only) from 22uf to 5uf.  I'd increase the V1 cathode resistor to 1.5k.  I'd remove the two 006620 diodes in the signal chain.  I might try a 5751 in V1.  I'd probably change the post LTPI coupling caps from .01 to .02 - .047 range.

IF that didn't improve the sound, I'd gut it and build a Dumble clone.  You already have a great speaker for a Dumblish tone.

with respect, Tubenit

[jamaio]

IF that didn't improve the sound, I'd gut it and build a Dumble clone.  You already have a great speaker for a Dumblish tone.
with respect, Tubenit

I like the way you think. Thanks for your input!!

My inspiration for getting the amp was this video series where he converted channel 1 to ab763 and channel 2 to Dumblish.

https://youtu.be/Lt1xyuTryQI

He goes through the horrible sound here.

I’m going to email him and see if he will share his design, just saw an email link for info.

This should be a fun project.

[66Strat]

You may find a useful mod in this thread at TGP.
https://www.thegearpage.net/board/index.php?threads/the-new-rivera-fender-concert-mod-thread.885852/

In the video below Mark Mitchell (SMark) is playing straight into his modded Concert ii. He mentions in the above thread that he has the Torres mods and an alnico Weber California speaker in his Concert.

https://www.youtube.com/watch?v=l1nhy-kn3ew

edit to fix link

[jamaio]

You may find a useful mod in this thread at TGP.

I have read through some of that thread and I tried to take notes for some of the mods they talk about, however, a lot of the posts are trial and error, they install a mod then decide later that it doesn’t sound good so there is no clear direction for mods. I’m not opposed to trying mods to see if they work, I like the interaction of this forum better. I can also learn more from first hand knowledge of trying mods on my amp with interaction from this forum.

[jamaio]

I’m going to email him and see if he will share his design, just saw an email link for info.

Well, I sent an email to the address and it came back undeliverable. I can watch the videos and pull out some of his design but he doesn’t give away all his secrets.

[tubenit]

The schematic and layouts don't match. However, they may simply give you some ideas for a starting place as you ponder your build.

You can edit the SCH schematic to match the layout if you want.

with respect, Tubenit

[jamaio]

The schematic and layouts don't match. However, they may simply give you some ideas for a starting place as you ponder your build.

I was in the middle of making a post when you posted. I will look at everything carefully and see where to start.

IF it were mine, I'd gut it and build a Dumble clone.  You already have a great speaker for a Dumblish tone.

I’m all in, hope you’re ready for a wild ride!! 

I played with the amp today trying to see what it lacks, what needs improvement. I figured I can never make the original circuit sound as good as any of my vintage Fenders and I have enough amps with that sound. Time to think outside the box and go in a completely different direction.


Has anyone ever done an ODS with reverb? I’ve got 2 6L6s 5 12ax7s and 2 12at7s, that should be enough for a high, high gain amp.

Where do I start? Should I keep any of the original circuit? Filter caps in the dog house. Changing any values that need to change, of course. The bias board? Should I remove all the components from the main board and try to build a layout on that board or start with a new board? Which ODS?

[tubenit]

(6) Fender HRDX to ODS Build - The Amp Garage


(6) Blues Deluxe to ODS #183 Thread - The Amp Garage

[jamaio]

Scouring through posts at TAG I found this.

https://ampgarage.com/forum/viewtopic.php?f=4&t=31060&hilit=6l6+ods+with+reverb

I have downloaded several documents on #124 for research and planning. I have a MAC and Linux laptop at home so I am not able to open the .sch files to modify. I could bring my work laptop home and load ExpressSCH on it, I guess I could use the DIY Layout Creator on my MAC.

The saga continues…

[PRR]

....I have a MAC and Linux laptop at home so I am not able to open the .sch files....

They don't open in JSchem?

http://jschem.bplaced.net/

Operating System    Download    OS Specific Installation Instructions
Windows    JSchem.exe    No installation required. ....
Mac OS    JSchem.dmg    Extract the JSchem application and....
Linux/Unix    JSchemUnix.bin    ...'java' in your PATH.
Make the program executable with the command 'chmod +x JSchemUnix.bin'
Any other OS    JSchem.jar    Run it with the command 'java -Xmx256m -jar JSchem.jar'
Sources    Sources are available on Github    The repository contains two NetBeans projects

How to use JSchem
Please read this document. It will hopefully answer most of your questions.

[jamaio]

They don't open in JSchem?

Thanks PRR, I will try and let you know my results. I did a quick search but did not see JSchem.

[jamaio]

They don't open in JSchem?

Thanks PRR, I will try and let you know my results. I did a quick search but did not see JSchem.

Thanks PRR, I installed JSchem and it works great, now I have a new toy to play with for hours and hours!! 

I am embarrassed to say I am an IT Systems Engineer, this should be elementary for me!! The company I work for builds PA (Public Address) and VIS (Signs) Systems for train/subway systems all across the US. I work with schematics (printed) all the time. If you have rode the train/subway in most major cities you have seen and heard my work. ***Disclaimer - if the audio quality is bad or the sign info is wrong, its not my fault.***

[PRR]

There are multiple formats of .SCH files. The one we use is supported by a bit of quasi-commercial software, but also by JSchem. But this is not JSchem's developer's day-job, and it has gone rudderless now and then.

But I remembered it was out there, that it was Java at the core and would nominally run on an ATM (or so the Java corp implied?), as well as the usual suspects. Just a matter of finding it. (His hosting server went belly-up.)

[jamaio]

I came across this post in my search for ideas:

https://el34world.com/Forum/index.php?topic=24076.0

I am trying to cutdown on the learning curve for DIYLC and this post has completed files. I will just need to edit the file to add reverb and the values from #124. Also this design doesn't use a rectifier tube, no need for me to punch another hole or make v7 bigger for an octal socket.

Slow but steady wins the race....

[jamaio]

Tubenit, what amp is the Carolina ODS based off of?

https://el34world.com/Forum/index.php?topic=21804.0

Thanks.

[tubenit]

Not sure if I understand your question of "what it's based off of"?

It borrows ideas from Dumble amps in that it uses a D-style tone stack in sort of an AB763 style "clean" channel.   The OD part is from the D'Mars OD but using a 5879 in OD.  It's cathode biased instead of fixed biased.  It can use 6V6's or 5881's/6L6's by simply changing tubes with no re-biasing.

IF the question is what known amp design is this a clone of that has been also cloned by others successfully.  There isn't one.  I am not aware of an amp that anyone else has done that is similar?  If it's out there, I am simply not aware of it.


With respect, Tubenit

[jamaio]

It borrows ideas from Dumble amps in that it uses a D-style tone stack in sort of an AB763 style "clean" channel.   The OD part is from the D'Mars OD but using a 5879 in OD.  It's cathode biased instead of fixed biased.  It can use 6V6's or 5881's/6L6's by simply changing tubes with no re-biasing.

Thanks, this answers my question, although I am not familiar with the "D'Mars" I assume is a D style Marshall, or maybe HRM?

I think this may be the right amp for me, if there is a "right one."  I have been stuck on the "clean Fender tone on the edge of breakup" sound for way too long. I recently completed my build of the Stout Reverb and it sounds awesome. I have always liked overdrive but, til now, I have never wanted to play with that sound. The Stout Reverb has a very smooth overdrive tone that makes me want to play some ZZ Top or Heartbreaker by Led Zeppelin. Also I like the fact that the Carolina ODS is a proven design that others have built.

I will review the schematic and layout from your "Carolina Overdrive Special 5879 plus" and make changes to the layout from "Joel's Carolina ODS Layout" in DIYLC. Then I will compile a parts list. I will post everything here for review before I start ordering parts.

Thanks for all your help.

[tubenit]

The Carolina Overdrive Special is a complicated build.  So, I am NOT pushing the idea at all that you "should" build it.  However, I will give you some more information that may help you make an informed decision.

With 5881's cathode biased is about 23 watts.  6V6's about 14 watts.   I used a Hammond 272FX PT  300-0-300   172ma   I used Tung-Sol 5881's and 6V6's. You can use 5Y3GT, 5V4, GZ34 or solid state plug in rectifier for various voltages for the tubes which each shape the tone.

After trying a handful of speakers,  I found a Warehouse ET65 to give the smoothest OD tone.  I found an Emminence Delta Pro 12A to give the "best" clean/clear tone and also a decent OD tone.

I think component selection is important for this design.  I used Orange Drop PS caps and some selected resistors. 

I think the OD has quite a few different OD tones in it because of the James Tone Stack which can "simulate" a mid hump or a mid cut. (See Duncan Tone Stack Calcutlator for examples)    I tried numerous tone shaping ideas in the OD section and the James Tone Stack pairs the best in my opinion.  It should be noted that much of the overdrive tone in amps will be with the mid tones accented. 

AND the 5879 tube has a fat punchy tone with a dash of chime in it compared to a 12Ax7. I have built OD sections with just 12AX7's and my opinion is the 5879 in the OD offers something positive and unique in tone.

The Dumblish tone stack in the clean section gives some tone shaping with the mid-boost and PAB (preamp boost) which are both on relays.

It takes a while to learn all the tone shaping options.  I play the COS with the OD on the majority of the time, but it's more like a pushed boost to the clean than a highly overdriven tone (although that is available also)

I think the strength of this design is that the clean is truly a clean/clear tone and the OD is significantly and OD tone.  In other words, there is a very noted difference available between the clean and OD tones.

I've attached the latest schematic and layout for the current COS I play.  Compare the schematic and layout.  Check for Errors!  If there is a discrepency between the layout and schematic, go with the schematic.  There is additional information on the other pages of the SCH schematic for the B+ rail and relay switching.

IF after you have looked all this over ................ and you're still interested ................ PM me and I'll give you some additional information about component selection.


Again, this is a complicated build and there's alot going on with it.  You will need a fairly spacious chassis to work in. My amp is amazingly quiet at idle. 


I strongly suggest that if you undertake this that you have a mindset that after you build it ........... that you will want to play it for a couple of weeks and then "tweak" something to shape it more towards "your" tone.


with respect, Tubenit

[jamaio]

The Carolina Overdrive Special is a complicated build.  So, I am NOT pushing the idea at all that you "should" build it.  However, I will give you some more information that may help you make an informed decision.

Thanks!!

It the past 4 weeks I have built a Princeton Reverb, a Deluxe Reverb and a Stout Reverb. I also repaired and recapped my ‘66 Bassman and I rolled back some mods I had done to my Blues Jr., the Carolina ODS will be a good “next” project for me. In the past 5 years I have built and overhauled 5 other amps.

The chassis of the ‘83 Concert is huge. I am going to use as much from it as I can, the EV 12L, PT, OT, RT and choke. It is solid state rectified, I will get voltages tonight to see how they compare to the CODS. There should be room for a rectifier tube if you feel it would be better. There are 7 preamp tubes, I could punch out V7 and make it an octal socket, then move the power tubes to the right. I will also leave the main filter caps in the doghouse, unless you feel that is not a good option.

If all the voltages match up, I’m hoping to just remove the main board and replace it with the CODS board, then swap other components as needed, pots, jacks, cap and resistor valves in the doghouse. I want to make the most with what I have without compromising the sound of the CODS.

Thanks again for all your help!!

[tubenit]

If all the voltages match up

They don't.  You have about 475v on your 6L6's per the schematic.  I have 366v on my 5881's. 


However, I neglected to accurately record whether that was with a 5V4 or a GZ34.  Having said that, I think you can use your solid state rectifier and keep your current voltages for the 6L6's and maybe even for the 12AT7 used in the LTPI? You certainly can use your higher voltages for the reverb circuit. 


Then you'd need to change the values of the dropping resistors for the clean and OD channels to get something closer to what I'm using. The voltages there certainly don't have to be exact, but you'd want them closer to what I'm using.


Your node C is 360v     The COS node C is 334
               D is 345                            D is 290
               E is 300                             E is 285


So, if I were attempting this,  I might change the dropping resistor between your Concert node B and C from 2.7k to 8.2k or 10k and then see how well they line up?
I would not worry about node B or node A being different.


Please note that I use a 12AY7 in V1 and that will show less voltage on the plates than a 12AX7 in the same position.


This is guess work on my part and something you'd have to experiment with.


With respect, Tubenit

[jamaio]

This is guess work on my part and something you'd have to experiment with.

Thanks!! This gives me a good starting point, I have no problem with swapping values to get the correct voltage. I will just order a variety of 3w resistors to have on hand.

[jamaio]

Channel switching!!

I was in the NOS parts room at work today and I saw this relay, it’s overkill for a guitar amp. We used them for channel switching to a hot standby amp if the primary amp/amp channel failed. This is for 100% uptime in public address systems. 24v 10a relay that plugs into an octal socket. It is ⅓ horsepower at 120v, it makes a loud click!!

[SILVERGUN]

it makes a loud click!!

That's one reason why you won't want to use it in an amp

[tubenit]

Hoffman sells some very reasonably priced, easy to use relays that are excellent.  Lots of information on using them in ARCHIVES  Relay circuit & layout board & ft switch (el34world.com)


And one of the pages of the SCH schematic has the relay information also.


With respect, Tubenit

[jamaio]

Hoffman sells some very reasonably priced, easy to use relays that are excellent.

Thanks!!

Well, there is no going back now. I removed the chassis for evaluation and removed the main board and filter cap board. I may have to rethink using the filter cap board, the wiring is horrible. There are 7 grounds and 6 power wires. I may just mount the caps on or near the main board. I am also thinking about adding a tube rectifier, there is room to punch a hole between the PT and the front of the chassis near where the rectifier board is now (see pic). The power and standby switches are on the front of the chassis so wiring will be easy. Would it be a bad idea to mount it there?

The chassis is 22” x 9”, the main board is 14” x 4” ⅝ so there is plenty of room for everything.

I printed the Carolina ODS schematics on 11x17 paper, I will use a highlighter and continue to edit the layout in DIYLC to fit my build.

Fun, fun!!

[SILVERGUN]

Have you seen different layouts where everything is on one board?

[jamaio]

Have you seen different layouts where everything is on one board?

On my Deluxe Reverb I mounted them on edge of the main board. I got a little messy with the silicone.

[jamaio]

Have you seen different layouts where everything is on one board?

Here is the layout I started with, I am editing it to fit my build.

[SILVERGUN]

Ok...and I went back up and saw that tubenit had posted a good one for the ODS #124 (reply #6)
I just wanted to make sure you had that mental image as you work through yours.

[jamaio]

Ok...and I went back up and saw that tubenit had posted a good one for the ODS #124 (reply #6)
I just wanted to make sure you had that mental image as you work through yours.

Thanks!

Yeah... this is the first time I am doing a layout, not totally starting from scratch, but trying to make everything work with the chassis I am using. I may end up with a design more like #124, need to see how everything else fits on the board. I am also making changes as I go, I thought I wanted to use the power section wiring I already had in place, starting with a working amp. The amp is 29 years old so it would be better to wire everything new. So now is the time to make changes before I start building. Also a tube rectifier will give me more choices if I want to try different output tubes later. Hopefully I make good decisions but I will make sure someone checks me work before I start to order parts.

[tubenit]

I have not studied your drawn layout or looked for errors, but my first impression is that it's quite well done and well thought out. I'm impressed. 

Can you please post the exact schematic you're working off of? 

I see some features like the LNFB for V1 and the FX. As an FYI, when I've used LNFB ..... I put it on a switch. 

Double check some of your work.  For example, you have V-1 as 100k and V-3 as 1.8k. 


With respect, Tubenit

[jamaio]

I have not studied your drawn layout or looked for errors, but my first impression is that it's quite well done and well thought out. I'm impressed. 

Can you please post the exact schematic you're working off of? 

Thanks, but I can’t take credit for that layout, that what’s done by Joel, I found his file posted from his version of the Carolina ODS and I used it as a starting point. I am using your latest schematics to edit Joel’s layout to fit my chassis. I have a long way to go before I will be ready to post proofs of my layout.

I posted Joel’s layout as an example of main filter cap layout. I am still not sure how I will layout the filter caps. I would need to rebuild the main filter cap board in the doghouse if I keep them there.

Thanks again for all your help.

[jamaio]

I am still working on my layout, I chose a Deluxe Reverb Layout done by Rob Robinette on an AB763 board that Doug Hoffman created. The Deluxe Reverb layout fit my chassis better and it was complete, I just have to edit all the values of all the caps and resistors for the Carolina ODS.

I still have a lot of work to do but I am making progress. I will simplify the design by only using 1 relay board for channel switching. I will also leave the effects loop off for now, I can always add it later.

I have the basic layout done, I still need to populate the board with the proper values.

This is an initial layout only, it is not complete and has not been tested!!

[tubenit]

I will offer a thought to consider ........................

There is some advantage in using the paralleled turret board approach I use IF someone is not already working with a proven layout.  The advantage is it is relatively easy to change the design.  For example,  changing a 12AX7 from reverb to FX.   OR changing a 12AX7 to a 5879 wiring. You make make significant changes and still have a decent looking turret board with the changes making sense and not adding floor noise.

It's more difficult to do that using something like the layout for a AB763.  The holes are already laid out specific to cathodes, plates, etc.....

Having said that, IF you are wanting tremolo in your Carolina Overdrive Special and you're wanting to use a 12AX7 in the OD rather than 5879 .......... then using Robinette's approach may be a better choice for you? I am not trying to discourage you from using this approach.  I simply don't know what exact schematic you're working off of?   

Just something to be attuned to as you approach this.  I am not saying you "should" use a paralleled turret approach. In fact, my guess is the AB763 type layout may be quieter at idle. The paralleled turret advantage is simply if you make modifications in the topology/design.

My strong advice to you is post the exact schematic you are wanting to use 1st before going any further with your layout. I think settling in on the schematic you're wanting first is something that you actually "should" do.       The schematic will dictate the layout.

With respect, Tubenit

[sluckey]

My strong advice to you is post the exact schematic you are wanting to use 1st before going any further with your layout. I think settling in on the schematic you're wanting first is something that you actually "should" do.       The schematic will dictate the layout.

+1

[jamaio]

My strong advice to you is post the exact schematic you are wanting to use 1st before going any further with your layout. I think settling in on the schematic you're wanting first is something that you actually "should" do.       The schematic will dictate the layout.

+1

Thanks Tubenit and Sluckey for your help.

I'm using the latest schematic and layout that Tubenit provided.

I've attached the latest schematic and layout for the current COS I play.  Compare the schematic and layout.  Check for Errors!  If there is a discrepency between the layout and schematic, go with the schematic.  There is additional information on the other pages of the SCH schematic for the B+ rail and relay switching.

The layout did not appear complete so I was recreating the layout in DIYLC. I grabbed Robs file because the basic chassis layout fit my chassis layout. I was going to see if the board would work because Doug has that file, it would be easy to have a board made. I don't have to use that "one" but I was trying to use something already made.

Thanks again for all your help.

[jamaio]

There is some advantage in using the paralleled turret board approach I use IF someone is not already working with a proven layout. 

While working in DIYLC I clicked on the wrong button and lost all my edits so I decided to start over from scratch, I have a basic layout with a paralleled turret board. My board is 14.5" by 3.125" and turrets are 5/16" apart center to center. I believe I have enough turrets but I have plenty of room for more turrets or I can space the turrets farther apart. I am attaching my diy file and the schematic.

Thanks again for all your help!!

[jamaio]

Inspired by this post: https://el34world.com/Forum/index.php?topic=23134.0 I have been making good progress on my layout. I am really getting the hang of DIYLC. I should have a first draft finished in a few days, I still have a long way to go. Completing the layout by referencing the schematic from Tubenit and the layout created by Apexelectric is really helping me wrap my head around everything. I still need to verify all the values in my layout with the values in the schematic.

Many, many thanks to Tubenit for all your help and allowing me to build this amp with your design.

This is an initial layout only, it is not complete and has not been tested!!

[Williamblake]

I don't remember why I didn't like jschm but vitualbox and windows run fine on old and not so old Mac's. It's free but you need a copy of windows of course. That way you also have access to Duncan's amp tools.

[jamaio]

After several hours of edits and scouring over the schematic I have completed the first draft of the layout. I have removed several things to simplify my initial build, then I can add features later once I have a working amp. I have removed the dwell and presence pots, I may need to adjust resistor values for my changes. Also, I am only using 1 relay for channel switching. I will need help verifying the connections to the relay and the other changes. I am attaching the original schematic that Tubenit provided and my DIYLC files. With Tubenit's blessing I will call my version "Cajun Overdrive Special", while giving Tubenit full credit for the design.

I still need to workout my main filter board layout. I will mount the board in the doghouse.

With Tubenits help, and others on the forum, I hope to have a great sounding amp.

[jamaio]

Made a bunch of edits, fixed some errors I found, moved some things around and shortened the main board a few inches. I still need to verify the relay wiring, reverb pot, removal of presence pot and correct any other errors I may have missed. I will look over everything again tomorrow with a fresh set of eyes.

[tubenit]

Cap (from 100k plate resistor V4-6)  to reverb pot is .01 instead of .001

V4-2 needs a .001 cap going to the 330k (mixing) resistor (on the north side).  This .001 cap should have a 1M resistor connected to it going to ground.  This juncture of the .001 to the 1M resistor goes to V4-2.  * look at schematic   You could use a terminal strip mounted close to V4-2 to do this IF you don't want to include that on the layout.

The "common" turret of the relay goes to the 330k (mixing) resistor (on the north side).  Other than that, the relay wiring looks correct to me.

The 1M reverb pot right lug goes to the south side of the 330k mixing resistor. You can use a mixing resistor value from 150k to 330k.  However you need a 330k resistor from that right lug on the reverb pot going to the RV junction.  * See attached Tubenit layout

The RCA jack to the V4-7 has a 220k/500p cap going to ground.  The tab of the RCA jack is already ground. Look for examples on Fender Princeton Reverb layout.


I have not checked any other aspects of your layout but the relay and reverb areas.   

You are doing a great job and I think your Cajun Overdrive Special layout will prove to be excellent and quiet at idle. 

With respect, Tubenit

[jamaio]

You are doing a great job and I think your Cajun Overdrive Special layout will prove to be excellent and quiet at idle. 

Thanks for the kind words!!

I have printed the schematic and layout on 11x17 paper, I will go over the whole schematic and layout with a highlighter again and incorporate your edits.

Thanks for all your help.

[jamaio]

The "Overdrive Special 5879" Special Sauce

I am not sure if this has been shared before but I want to make sure everyone knows about the 5879 tube. The 5879 uses a different pinout so it is not a replacement for a 12xx7. I have attached the data sheet for the 5879. I only discovered the difference when I was creating my layout and I saw unfamiliar wiring in the schematic.

I found NOS tubes at https://www.tubesandmore.com/products/vacuum-tube-5879-pentode-sharp-cut, the ones I received are labeled Philips and made in the USA.

[jamaio]

I have not checked any other aspects of your layout but the relay and reverb areas.   

I believe I am done with my layout, I fixed the errors you found. I made several changes, hopefully for the better. I was trying to place most of the resistors on the main board but that just cluttered things up so I moved everything to the pots or tubes. I have attached the schematic with areas I am not sure about. I removed the Midboost relay, PAB relay, Dwell pot, and Presence Pot. I also circled another area I am not sure about, it appears to be a 95k trim pot coming from V2-2 with a note "set at 66k" not sure what it is for but I did not include it in my layout.

I also still need to layout my main filter board. I have added the dropping resistors to the main board. I also added some jumpers that I may place under the main board.

I am getting close to finishing the design stage, hopefully I can start ordering parts soon.

Thanks again for all your help!!

[tubenit]

I edited the SCH schematic to reflect your changes.  A couple of thoughts:

-  I would advise leaving the mid-boost and simply put it on a mini-toggle.  Very easy mod to do. The mid-boost on is useful with single coils, then leave it off withhumbuckers.  Just leave the relay switching off and switch in manually.  I find it a very useful feature.

-  I used a trim pot on board to set that 66k to ground. Your choice of a 68k should be fine, but be prepared to experiment from 47k-100k range to see what you like?

-  You can still have NFB by using a 100 ohm resistor and a 4.7k resistor.  When the PPIMV is turned down, it begins to negate the NFB. When it's fully turned up the NFB works.

-  Glancing over your layout corrections from yesterday, they look fine to me.  I still have not checked the rest of the layout board.

-  Since you're not using a dwell pot,  if you have too much boing in your reverb .......... try changing the 1M to 820k or 680k.

- I don't know if you will want to include the passive FX loop or not?  I have used a Carbon Copy Delay,  Boss digital delay, Wampler Faux Echo,  Moen Pretty Dolly (my favorite delay pedal) and a Digitech Reverb in the passive FX loop and they have all worked fine and to my satisfaction.  It's just two jacks to make this work. :-)

- A 12DW7 works well as a "one tube reverb" IMO.  I've also used 12AT7, 5751 and a 12AX7.   The 12DW7 is half 12AU7 (send) and 12AX7 (return).

With respect, Tubenit

[jamaio]

I edited the SCH schematic to reflect your changes.  A couple of thoughts:

-  I would advise leaving the mid-boost and simply put it on a mini-toggle.  Very easy mod to do. The mid-boost on is useful with single coils, then leave it off withhumbuckers.  Just leave the relay switching off and switch in manually.  I find it a very useful feature.

-  I used a trim pot on board to set that 66k to ground. Your choice of a 68k should be fine, but be prepared to experiment from 47k-100k range to see what you like?

Thanks!!

I will add the mid boost with a mini toggle switch, I have plenty of room. I will also add the trim pot, what does it adjust?

The amp originally had an effects loop with a send and return pot, I rarely use any pedals, I usually plug straight into the amp.

One attraction to this design for me was onboard reverb and gain, that’s all I need unless I learn a new tune to play!!

I will print everything out and go over it again with a highlighter to check for errors, I will add the trim pot and mid boost relay with a toggle switch, I can use the ground switch. Also there is a hum balance pot on the back for the heater circuit, I can use that spot for the 100k trim and make it accessible for fine tuning in the cabinet.

The rest I will save for future mods or add add the dwell if the reverb needs to be tamed.

Thanks again for all your help!!

[tubenit]

You don't "need" the trim pot.  A simple resistor will work fine when you find the value you like.  The trim pot controls volume like a volume pot would.


I think you will find the mid-boost to be useful.



With respect, Tubenit

[jamaio]

You don't "need" the trim pot.  A simple resistor will work fine when you find the value you like.  The trim pot controls volume like a volume pot would.

I think you will find the mid-boost to be useful.

I have added the trim pot to the board, still need to workout the mounting. I have also added the mid boost relay with a mini toggle switch.

I made all the edits based on the latest schematic you provided, thanks.

As always, I will print everything out and go over it with a highlighter to check my edits.

Thanks again for your help!!