My version of the TOS

[stingray_65]

I've finally have all the mechanicals finished for my version of the TOS which I ended up calling the Chicago OverDrive Special.

I've moved the tone circuit on the clean channel from between V1A and B to the master volume so that I wouldn't be coloring the signal going into the OD channel where there is a tone pot anyhow.

I added a relay channel switch so that I can use a foot switch.

I rearranged the controls and renamed some of them so they seemed more fluid and intuitive (IMO)

I added a balanced line out that will be tapped off the unused 16 ohm tap off the OT

And I changed from cathode to fixed bias.

So as I sit tonight, everything that needs a hole or screw has been mounted to the chassis.

The cab is finished and just needs the Celestion Super 65 mounted.

I also did a cool mod to the cab when I was about to make the lower rear panel.

[stingray_65]

Oh yeah!

The back panel

Got any clues as to whats neat with this?

[stingray_65]

Stealth Tilt Back Legs LOL

[DummyLoad]

nice!   :glasses9:

[LooseChange]

Nice work!
You pounded that out fast.
How do you make your face plates?

[tubenit]

Wow!   That is very very cool!  I like it. Nice looking amp.

When you get a chance, please give a tone review and/or a soundclip with it.

Thanks for sharing your great work.

With respect, Tubenit

[stingray_65]

Thanks guys

I had the face plate made at Engraved Images in Temperance MI. They do plaques and awards, that sort of stuff.

I had a small (12" x 24") sheet of black anodized aluminum and the artwork so he charged me very little ($45) to do a front plate (19" x 2 1/2") a rear plate (19" x 2") logo (2" x 4") and a tube layout chart (3" x 5")(not pictured, it's mounted on the inside of the rear cab panel)

Sound clips will be made as soon as it's finished. Last week I did a repair on a Hotrod Deluxe for a small studio in Adrian Mi.

I was mentioning Tubenits design and how I was going to build it. So he offered to record it for me, that is if I could leave it there for a week or so :)

He plans on recording it in stereo with the balanced out on the left track and one of the studio mics in front of the speaker on the right track. The bonus to that is there are guitar players in and out of there all the time from chicken pickers to speed metal shredders. Me, I know 3 chords G A and D so there wouldn't be much of a demo if I played through it LOL

Thanks again guys. I'll heat the iron up this week and have the boards populated, controls wired (shielded wires every where Chip) and pretty much dialed in. That is to say if there isn't too many issues when I fire it up. There's always sumthin

Ray

[67polara]

Looking Good! 

Show me what you did to use fixed bias and is there a way to switch from from fixed to cathode on the fly?  I would sure like to hear the difference with no other changes other than bias.  I also want to use fixed and 2 KT77's.

Tony

[stingray_65]

Hey Tony,

We briefly discussed fixed biasing the TOS here: http://www.el34world.com/Forum/index.php?topic=9638.100

Just scroll down to the bottom of page 3.

Note that there should be a 1W resistor before the diode. That resistor sets the bias range. I am starting off with a 150 R 1W but in all likelihood that will change. It should be valued so that when the bias is set, the trim pot should be close to 12 o’clock. I will post my results with this here.

As far as the switching between fixed and cathode biasing, check out Tubenits most handy schematic here: http://www.el34world.com/Forum/index.php?topic=5621.0

I have this printed out and hanging in like 3 places around here.

I had thought of putting in that circuit and still might. But this chassis is so tight with all the pots and stuff, so the empty lugs that I had for the cathode biased version that Tubenit and Geezer built ended up being used for the regulated 5V supply for the channel-switching relay. I still might add it putting the switch under the chassis and point-to-point wire the cathode cap and resistor in.

I really love the “Fat Bright Full” switch. I put it in nearly every amp I’ve built. I find it’s most useful on Tweed type preamps.  The Tweed preamps are so definitively Fender and sound like heaven, when you use single coil pickups that is. Plug a humbucker or an active pickup and they tend to get farty, flubby or bassy.  That switch lets you get away with a lot without having to change coupling caps to tailor the amp to a specific guitar. I like to think of it more like a Marshall, Fender, and Other switch.

Ray

[67polara]

Thanks Ray just what I needed to know. 

I think I have the same Transformers as you this should be fun.

Tony

[stingray_65]

I'm using Magnetic components
PT model 40-18005 120 V pri  53v bias 355-0-355
OT model 40-18000 4.2k pri 2,4,8 out M-6 laminates
CK model 40-18003 4 Hy 90ma

Funny, as I go thru Mag Comps catalog and their spec sheets and my receipts I'm finding that what I have and what I ordered are indeed two different beasts.

Which would make Doug the only supplier on this build to actually give me what and how many I ordered. Oh yeah! and Doug used his matter transporter to put his parts right in my mail box like the next day.

yeah! I had checked a receipt  from 8-09-2010 and it says "Super Reverb 120v pri  $54.50", Mag Comp catalog states their Super Reverb tranny is 240/120v pri and has a 5v winding and dual 2ndary windings and is model #18029 and lists for $89

Also means I'll have to redo my balanced out. I figured it using an unused 16 ohm tap and now I see I have  an unused 2 ohm tap instead (still going to use the 4 ohm tap for the NFB)

Ray

[sluckey]

I added a balanced line out that will be tapped off the unused 16 ohm tap off the OT

Ray, I'd love to see a schematic that shows that balanced output.

[67polara]

Yep same Iron I got mine out of a Fender super 60 red knob POS, but for $50.00 I think I did good.

I want to do basically the same but with an active effects loop also.

Tony

[Fresh_Start]

There is a potentially more "elegant" way to switch from fixed to cathode bias using a single-pole/double-throw (SP/DT) switch.  I'm not positive where I found this but think it was in one of Kevin O'Connor's books.

Just an alternative to look at.  Unlike today, when I was a computer programmer in the early 1980s less was ALWAYS more due to hardware limitations (memory, etc.).  Note that it does ground the bias supply when in cathode-biased mode, but I don't know why that would be a problem.

Cheers,

Chip

[zendragon63]

Real impressive looking build. And I really dig the 'stealth tilt back legs'.  Regards

dennis

[Tone Junkie]

Man I wish my woodworking skills and tolexing were half that good. and the stealth tilk back AAA+
   Bill   

[mresistor]

That's a really nice looking amp, that grill cloth looks familiar and beautiful. Integral tilt-back legs is a whale of a great idea. I'd love to hear it. 

[stingray_65]

Hey Chip,
I'll look into that closely, you've not steered me wrong yet. But I'm still undecided on if I'll switch the biasing in and out

Jim that grille cloth does look suspiciously like your recent buid now that you mention it :). might be enough wheat left for a head cab.

Denis,Bill Thank you for the kind words. Bill like any other skill the more you do it the better you get. I built the whole thing with a chop saw, table saw and router.

 If I were to suggest a project to a budding cab builder I would say to look up a cajon. It's a Peruvian box drum. simple box 12" square by may15"tall all made of 1/2"plywood except for the face and its 1/16th or maybe 3/32" screw and glue everything except the face which is traditionally put on with nails. no matter how bad it turns out its a fun weekend build especially with a kid. LOTS of fun to beat on. just practice your joinery and keeping things as square as you can.

Ray

[stingray_65]

I added a balanced line out that will be tapped off the unused 16 ohm tap off the OT

Ray, I'd love to see a schematic that shows that balanced output.

Steve I just use Ted Weber's design https://taweber.powweb.com/store/balun.jpg
They sell that little x-former for like $2 and they really do capture the sound very well. the highs are a little diminished, but I've not seen where a simple tweek in the PA or recording gear can't fix. I've never added the cap like it says.

Ray

[navdave]

DOOOD that is a killer cabinet! The whole package is top notch 

[sluckey]

Thanks Ray.

[stingray_65]

Populated the boards this morning.

I'll end up changing out the 150k resistor going to the plate on the 5879 to about 50k as per Geezers shemo

[tubenit]

5879 plate resistor should be 56k not 150k.


With respect, Tubenit

[stingray_65]

Stepping back a few squares on this build.

Gremlins and my own haste has started to run rampant so I'm going to restart the project back to where I started.

First gremlin was the big 40uf600V cap. had a soft dent in the side when I bought it from someone who also makes speakers. Checked way over the range on my cap meter so hey it was still good.

still good till I threw the standby switch after I had my mains, HT, heaters and Bias wired.
heard the sizzle and the light bulb limiter was starting to what its supposed to do!

and wouldn't you know I glued the darn filter caps down good with polyurethane hot glue.

next was my own haste. 8 dang pots  spaced an 1 1/2 apart and my control wiring looked awful.

I've used the old mount them reversed trick before so that you use the front panel as a jig.

being it is a non symmetrical layout and the fact that the holes were hand drilled I was worrying that the pots might not line up when I flipped them back into the chassis. Happened to me before.

I had a flash of "DUH! why didn't I think of that when I started: when I recalled that I have a face plate and I can use that as an assembly jig.

I'll order $30 worth of pots and caps from Doug this payday and start anew and MAYBE just wire up my sockets in the mean time.

I'll end up re-using the old pots again at some point, but I want this chassis to look as nice on the inside  as well as the cab does on the outside.

Most of all I want to hear this thing sing like drunken angels and I dont want to have to chase down sloppy wiring to get it to.

Ray


 

[stingray_65]

OMG WOW!

Ok.. So I got the filter cap to replace the cobbled in cap soldered in place... no more 120Hz buzz.

Disconnected the NFB and I din't have to worry about  flipping my brown and blue wires  on my OT.

I also pulled the unused taps from the OT that were coiled under the board and put them on the tops side of the chassis. No more weird oscillations!

Replaced the stack of bias range resistors and installed the correct 1.5K 1W resistor.

Biased the 6L6WXT's to 40mA

SO....

I hurry down to the closest guitar hero I can find and make him break the cherry on this amp

Holy Jumped Up Jesus in a Sidecar this thing is LOUD!

It is EVERYTHING Jeff and Geezer said! Sustain for days that just bloom into feedback slow soft and gracefully.

The clean channel is crystal! The first guitar he played into it was an Ibenez Artcore Archtop Hollowbody.
At lower gain like about 3 level at about 8 and PPIMV at around 6 it literally sounded like the guitar was mic'd (played into a Celestion Super 65 12" 8ohm)

OD/Clean channel switches so quiet, but the OD channels output is so much stronger than the clean channel you have to dial back its volume LOTS

I dialed in mild over drives to metal crunches with just a twist of the OD drive knob

next we swapped in a Eminence Wizzard 12" 75 W 8 ohm. Holy smokes it sounded like Sin covered in chocolate!

He switched guitars to an Epiphone Les Paul jr and I switched the V1 cathode cap to .68uF.

The cats had gathered up on the patio so I decided to go full tilt. 10 on the clean gain 8 on the OD drive and 10 on the PPIMV. He hit a power chord and they scattered like buck shot!

Thats when the trouble starts LOL

He starts in on some heavy Sabbath leads and I glance at my meter that was still hooked up to the bias check point.

I was drawing about 120mA !!!!. It was too bright out so I couldn't see if the tubes were red plated, but they sure smelled HOT!

I turned the PPIMV down in a heartbeat. At about 6 the current draw is about 45mA but above that with a hot signal it goes WAY TOO HIGH.

We noticed too a sort of ringing when the OD Drive is set above 4. not unpleasant but it's there.

So I figure I'm still having parasitic oscillation some where. Funny though I still get the excessive current draw when the PPIMV is dimed and I drive it hard on the clean channel only.

In my haste I never checked the voltages, I knew they were high when I checked the amp out on it's initial start up without the 5879 pentode in place, but a quick riff through my calculator said the voltages would drop to acceptable levels with the draw of the 5879.

I was wrong

So tomorrow, I'll get my voltages in order and hopefully that will cure a few of these ailments (like the ringing over drive)

I'll tackle the rest of the issues one at a time.

Gezzer and Tubenit!

hats off to you guys. this has to be the most versatile amp I have ever heard!

Jeff, Thanks so much for your continued support. I'll be leanin on ya to get me home with this I'm sure!

Ray

[John]

I have really been enjoying this thread! 

[stingray_65]

Thanks John!

I've enjoyed this build more than any other with maybe the exception of my first.

If I had stayed closer to Tubenit's and Geezers design I would likely be finished a while now.

This is a high gain amp and needs a bit of coaxing to get everything just right. I bit off a big chunk when I took this on, but after hearing the clips I had to build it.

My best advice is if you aren't a skilled builder, build it EXACTLY like they did. PRR will tell you the virtues of that line of thinking!

But me I can't leave well enough alone 

Glad you enjoyed my journey so far, I hope to record clips this week to post.

Ray

[67polara]

Hey Ray I think I read somewhere that there are two ways to do the VVR.  One for fixed bias and one for Cathode bias.  I am sure someone will correct me if I am wrong.  If you keep your bias voltage the same and vary the b+ I don't think your tubes are gonna like that!!

Tony