Carolina Overdrive Special amp

[Apexelectric]

Still reconfiguring the Reverb section. Definitely messed up the layout.

Found the short issue as well. Cap can screw was a little too long and was touching the turret on the back side of the board.

Been fighting a nasty cold for the last week and a half so I haven’t been working on the amp. Finally feeling somewhat human again. Might put it all back together this evening after work.

Thanks for checking in.

[tubenit]

Thanks for the update.  I am anticipating you getting this resolved and having a GREAT sounding amp!   Rooting for you!

I've attached an edited layout that should match the schematic regarding reverb section and insertion points.   I do NOT have Visio, so I had to edit with Windows PAINT.  I erased the clean/OD switch and some other items ................. so just pay attention to what I drew as "corrections" regarding the reverb ONLY.

I used the spot where you had passive FX insertions to draw this, but obviously you can still have passive FX loop if you want to.  I'd simply keep it after the 150k mixing resistor for the reverb insertion and prior to the LTPI entrance cap of .01

With respect, Tubenit

[Apexelectric]

Well the amp is coming to life! So far so good. Need to figure out the channel switching issue now. Haven’t made it to testing the reverb section yet.

I’m getting 5V out of the power supply but it seems to drop to less than 1V when sent to the relay coils. I’m using a simple footswitch and an isolated 1/4” stereo jack to switch the negative lead from the power supply to each of the relay coils. The positive lead goes straight to both coils from the power supply. Both the power supply and relay boards are the ones from Hoffman.

Thanks

[tubenit]

Hooray progress!   Keep us posted please.  Watching this with interest.

With respect, Tubenit

[Apexelectric]

Any thoughts on the channel switching problem?

[tubenit]

See reply #40 on this thread on relay switching in ARCHIVES:    http://el34world.com/Forum/index.php?topic=14348.0

Double check your work against that, please. 

I tried looking at the picture of your amp chassis interior around the relays but I'm having trouble discerning what is going on there.

Does this happen on both relays?   

Have you tried removing a relay one at a time to see what happens?   

With both relays removed what do you have across the diode?

Have you tried safely using alligator clipped wires to switch the relays on and off instead of the footswitch?

Not sure how to help you with this?     IF none of that provides an answer, can you post close up pictures of both relays and the relay power supply please?

One other thought,  I used a different base for the relays to be installed.  It had pins and I pushed out the ones that the relay wasn't needing. You used a base that doesn't have pins pushed out but seems to have metal that squeezes around the relay pin?  I am wondering if the bottom of your base has something touching somewhere shorting voltage out?  Just a wild guess and may not be relevant?


with respect, Tubenit

[PRR]

> Any thoughts on the channel switching problem?

I hate switching.

[Apexelectric]

Looks like I got the polarity reversed on the coil. The schematic on the top of the relay shows the bottom view which doesn’t make sense when you’re looking at it from the top side.

[tubenit]

Does this mean the switching issue is now resolved?

And if so,  ............ does this mean that only the reverb issue is left to resolve?

With respect, Tubenit

[Apexelectric]

Still have a couple issues to deal with. The relays are getting the proper coil voltage now but it looks like the relays are wired wrong. The relay boards/basses are not laid out in the configuration like the schematic shows. So the common terminals are on one end of the 16 pin relay base rather than in the middle like toggle switches and NO and NC terminals are toward the middle.

I’m also having an issue with my NFB switch. One position seems to kill the signal.

I’ll keep going with trying to get this resolved and post tomorrow with any progress.

[tubenit]

The relay boards/basses are not laid out in the configuration like the schematic shows. So the common terminals are on one end of the 16 pin relay base rather than in the middle like toggle switches and NO and NC terminals are toward the middle.

Just so that others can reference the information about the relay,  I've attached this. 

PLEASE keep us posted.  I continue to believe you will resolve this and have a good amp!

Please note that "common ground" is NOT the same as the "common" referenced in the relay switch.

I like it that you are isolating concerns and working on them sort of a section at a time.

With respect, Tubenit

[Apexelectric]

Thanks. Yeah, one thing at a time. Especially since some can be related. Fixing one will sometimes fix another.

[Apexelectric]

Got everything reconfigured on the relay boards and fixed my NFB problem. Reverb works great. Seems like all my issues have been resolved but I seem to be having a weak signal coming in to the first sections of the amp. Both channels are affected and the volume overall seems weak unless I have the Guitar volume turned up to 10. Then it’s useable but still not very loud.  Anything till 9.5 on the guitar is weak and useless. I might have a resistor value issue somewhere in V1 or V2 signal path?

Also the presence knob doesn’t seem to do much to affect the sound. I didn’t have a 2.2k so I used a 5K but I wouldn’t think that would render it ineffective.

Here are some voltage readings at idle.

305-0-305 VAC from the PT
375 VDC B+
374 Node B
345 Node C
281 Node D
272 Node E

Output tubes

338 Plate to cathode
366 Plate to ground
363 Screen to ground
28.5 across shares 250 ohm resistor

Preamp Plate Volts

V1A 140
V1B 147
V2A 222
V2B 149
V3   126
V4A 336
V4B 181
V5A 254
V5B 254

[Apexelectric]

Figured out the other two issues and all is good!
 
The presence still seems a bit underwhelming but works now that I moved the resistor to ground instead of jumping terminals on the pot the way I had it.

My input resistor value was way off. Somehow I managed to put a 1K instead of a 1M. That’ll quiet things down for sure.

Amp runs pretty quiet and sounds awesome so far. Need to play with some speaker choices then build a head cabinet!

Thanks Tubenit!

I will post the final Layout here in a few now that it’s proven.

[tubenit]

Amp runs pretty quiet and sounds awesome so far

I just love stories with a happy ending!     

THANKS for sharing your success! 

As far as speakers ...................  Warehouse ET65    Emminence Delta Pro 12    Emminence Cannabis Rex   Emminence Texas Heat and Emminene Red, White and Blues have all been favorable speakers for me. 

I currently have a Warehouse ET65 in my COS, but also have used the Delta Pro 12.   Both sound fantastic with the amp, IMO!

Hooray for your success!   With respect, Tubenit

[Apexelectric]

Well here is the layout as it stands now that its working properly. All jammed into the narrow panel Bassman Chassis and running quietly.

Attached is the original schematic from Tubenit for the Carolina ODS Plus with Reverb along with my layout of the Colorado ODS Plus Reverb.
The only change from Tubenit's schematic is the addition of the NFB switch and the Standby mode on the power switch which shorts the signal at the MV pot. Otherwise, it is the same.

I will post some final pics once it gets a proper cabinet.

Big thanks to Tubenit for all the help and encouragement!

[Apexelectric]

I have a Cannibas Rex and a Texas Heat on the shelf. Will give them a try.

Looks like Im dissipating a bit more wattage than your amp. I might leave it the way it is because its still within the tolerances of the transformers and tubes.  What could I expect, tone-wise, if I increase the output resistor and back off on the wattage. I did use a 250R instead of a 270R since that's what I had on hand.

Thanks again!

Mike

[tubenit]

I've experimented with 6V6, 6L6, & 5881 cathode biased amps with different value power tube cathode resistors ranging from 250ohm to 430ohm.

I can hear a slight difference between 250R and 330R or 360R.   The latter having perhaps a little more headroom.  I don't think I could pick out any discernible tone difference between 250R and 270R?

I think my COS clean channel is somewhat Fendery but a little less mid scooped and with slightly more warmth.

The COS OD channel almost is more like a "boost" heading toward overdrive tone.  Very transparent and touch sensitive in my amp.  The COS OD channel is not as compressed and vowel sounding as a Dumblish overdrive & it sounds like the clean channel is boosted or pushed in some manner & you hear significantly more sustain on the OD channel. I think it's a very cool tone and overdrive and there is still excellent note separation playing chords and such.

Having said that, there is a significant difference in tone and especially feel between the clean and OD. And both are very useful tones for what I like.

Since I am using an active FX loop instead of a reverb, I would anticipate some difference in tone between our amps.  I would truly love to hear some sound clips of yours when and if that is possible.

With respect, Tubenit 

[Apexelectric]

I’ll try to get some sound clips together in the next couple weeks. Did you ever post any of your amp?

[tubenit]

Come to think of it, I haven't posted any.  Will try to do that.

[Apexelectric]

Any thoughts on how to get a bit more range out of the Presence control? Would the 2.2k pot make a difference over the 5K that I have installed currently?

[tubenit]

I don't know the answer to the presence control question.   Please remember that when the PPIMV is turned down that the NFB and presence starts being negated (as I understand it).  When turned all the way up, the presence control should work as "normal".

You could safely use two insulated alligator clipped wires to parallel a 4.7k resistor across your 5k pot (to simulate around 2.5k) to see if that changes anything?  IF that helps, then switch to a 2.2k pot .......... OR parallel a resistor accordingly across the pot.

You can parallel another 1uf with the current 1uf to see if that changes anything for 2uf ?   You can try a 6.8k NFB resistor instead of 4.7k to see if that changes anything?   

I honestly don't know much about presence controls so I don't know how to advise you.     With respect, Tubenit

[Joel]

I'd love to hear some sound clips!

[Apexelectric]

Worked all day in the lab yesterday finishing up the cabinet panels and coverings for the COS I built a couple weeks ago and took it out last night to a friends house and had a couple musician friends give it a whirl and it sounded great. They were both thoroughly impressed. I stuck an 80W Jensen Neodymium speaker in it as it was one I wanted to try on an older build and seemed to pair ral well with this amp. When originally testing the amp I tried it with Celestion Golds, Celestion greenbacks, and G12H speakers, none of which got my attention.  Might try a couple other options before settling on this one for sure but I can’t see it getting much better. I have a couple Eminence speakers that I was going to give a try last night but we were pleased with what we had from the get go.

Here’s a couple shots of the finished cabinet.

[tubenit]

WOW!  That's an incredibly beautiful and well done cabinet!  Superb work.   

Thanks so much for sharing the photos!   Glad to hear the COS is getting some good tones for you.

With respect, Tubenit

[mresistor]

Michael, that's a beautiful cab and a great amp..  Well done and thank you for sharing.. 

[Apexelectric]

I’ll get those sound clips eventually.

[Apexelectric]

The midboost on the amp seems to have a very slight effect on the tone. Was wondering if this was typical or if I should be getting a change that is pretty obvious. If it is supposed to be subtle then what would be the best way to adjust it to make it more pronounced?

Thanks as always.

[tubenit]

I view the midboost as giving a very noticeable and significant change, but I have my mid pot dialed down  quite a bit.  With the mid pot dialed up to 5-7 (with 10 being highest), the mid boost is somewhat more subtle but I think still noticeable.

To increase the midboost, try a .003 or .0047 cap if you like.  Make sure the 4.7M to ground is 4.7M and double check the values you have which should be 390p and .0025.

You can simply parallel a .002 cap across the .0025 that you have safely using insulated alligator clipped wires & see if you like that increase in mids.

With respect, Tubenit

[Apexelectric]

All the values check out. I’ll play with it some more and get back to you.