Tweed Deluxe Build

[Fresh_Start]

OK here goes!  I just ordered most of my parts from Doug for a 5E3 build.  My design goal is to get as authentic a 5E3 sound/tone/feel as possible.

There are a few things I will get elsewhere - most importantly a PT providing 355-0-355 330-0-330 for 100ma.  This seems to provide vintage correct voltages as best I can tell from a bunch of research. 

I'll talk about tubes much later.

Speaker looks like either a Weber 12A125-A 12A100T (P12R replacement) or 12A125S (P12Q replacement).  Any comments/recommendations between those two would be great.

I'm working on a slightly modified version of the Hoffman layout.  Thanks to Sluckey for the Visio file!

I'll post a preliminary schematic with proposed initial component values in the next week or so, but here are my initial thoughts about the build.  Please note that I've never played a Tweed Deluxe so may have some pretty dumb ideas. 

I'm particularly interested in your input on what to do with ground switch.  Is it worth experimenting with a switch to solid state rectification?  Voltages would go up a lot => would that produce more headroom and a cleaner amp that's useful?  Another alternative use of the Ground switch might be Geezer's cathode switching scheme for 1/2 power, etc.

Here are my build/modification notes as of today:
 Definite:
470 ohm screen grid resistors
Elevate heater center tap (cathode or voltage divider?)
Separate R-C networks for V1 triodes
4 ohm and 8 ohm speaker jacks
Shielded heater cable for V1
Shielded wire from input jacks to V1
Double pole Power switch – neutral and hot DPST
UF5408 diodes on rectifier socket (Immortal Amp mod)
 
Experiments:
Grid stopper on cathodyne (33K to 470K)
Larger power tube grid stoppers (1K5 initially)
220K plate / 2.2K or 2.7K cathode resistor on channel w/o Tone
Preamp Cathode bypass caps:  start with 10uf maybe???
100u bypass cap on power tubes?
Reduce one or both coupling caps between V1 and V2 gain stage
Master volume? (replace 1 meg grid return for cathodyne with 500K pot + 500K resistor)
Use Ground switch for:
                Solid state rectifier switch
                Geezer cathode power switching
 I'll add a schematic soon.  Layout will come later after I have the chassis and other parts.  My intent is to make this a build blog of sorts.  Hope that's OK.

Chip


P.S. I'm editing this first post as I make some decisions.

[Fresh_Start]

P.S. on first post.  I did not include the "Paul C. mod" (fixed bias for concertina phase inverter) because it was never intended for a cathode biased power amp.  Found a 2002 post from Paul C. himself saying so but can't find again.  Other research backed up the idea that fixed bias for a concertina PI is much more important for a fixed bias amp like Blackface Princeton.

If anyone has done A/B experiments with this mod on a Tweed Deluxe and liked the mod, please let me know.

Chip

[Mike_J]

Please note that I've never played a Tweed Deluxe so may have some pretty dumb ideas.

I will pass on experience from my Tweed Deluxe build.  First I started out thinking it would be better to have a little bit bigger transformers for the build so I put Deluxe Reverb iron in the amp.   Bad idea.  The magic from this amp is helped by the undersized output transformer from what I can tell. Anyway, I am now buildingf a Deluxe Reverb clone and will use the iron from the Tweed build.  I also put a choke in it and increased the filtering. Ended up with an amp with a lot of headroom that sounded somewhat like a small tweed bassman.  Not what I was looking for.


You probably know this but I have heard that a lot of the early ZZ Top music was recorded on a Tweed Deluxe along with a lot of other classic music. The Dumble Overdrive Special is supposed to be an attempt to get the tone of the Tweed Deluxe at more volume (not accomplished in my opinion).


I used a Jensen reissue P12Q and I was happy with the choice of speaker.


Based on my experience I would start out with an amp very close to the original.  The iconic nature of the amp is based on it.


Thanks
Mike

[Fresh_Start]

I've found a different power transformer that has 330-0-330 and 355-0-355 secondary high voltage windings. Looks like 330-0-330 should put B+ in the 350-375 volts on the power tube plates. AFAICT that's the vintage 5E3 sweet spot. Also this PT is only rated for 100ma which also should be closer to vintage.

My possibly goofy idea is to put a DPTT on-off-on switch in the Ground spot, giving me vintage volts, standby, and higher volts (about 400 on the plates). It would be nice to add more power rail filtering to the higher voltage option but may not be practical.

Chip

[drew]

A guy on ampgarage.com said fairly recently that the "3 way switched feedback" mod described here:
https://robrobinette.com/5e3_Modifications.htm was something all 5E3s should have.  The guy who owns that website also indicates it's his favorite 5E3 mod.

[mresistor]

That guys website has some pretty darn interesting stuff. Thanks for the link. All you ever wanted to know about the Fender Deluxe.

[Fresh_Start]

A guy on ampgarage.com said fairly recently that the "3 way switched feedback" mod described here:
https://robrobinette.com/5e3_Modifications.htm was something all 5E3s should have.  The guy who owns that website also indicates it's his favorite 5E3 mod.

Thanks - I'll go find that Amp Garage thread. I had discounted that idea because one of my amp's has switchable feedback and I haven't touched that switch in several years.  However, Robinette's pre-phase inverter master volume approach makes lots of sense to me.

On second thought, I'm staying away from sites that Google claims contain malware. Not a risk I need.

Chip

[mresistor]

Chip the robinette site is clean. Drews link does not contain malware. You are right though about the Amp Garage, every time I have tried navigating to it my shield throws up a big red flag.

[Fresh_Start]

Sorry I was unclear - it's the AmpGarage site that gets flagged, not Rob's.  I went back to Rob's site right after reading Drew's helpful post.

Respectfully,
Chip

[drew]

Yeah, ampgarage is unfortunately in some kind of extended limbo/standoff/who knows what with Google in terms of getting off that malware warning deal.  It's not clear why it got on the blacklist originally; the site owner claims no one ever got malware from the site; as far as I know, none of the users who have chosen to ignore the warning and continue to use the site have reported getting any kind of malware; R.G. Keen keeps pointing out that when a similar thing happened to his site, he followed Google's instructions and got it squared away very quickly; but the stalemate just keeps dragging on and on.  Very disappointing, as it's such a great forum.

Anyway, the post i referenced above wasn't much longer than what I wrote, so no real need to go looking for it.

[Ed_Chambley]

Chip, I have done about everything to a Tweed Deluxe and anything you do will change the amp.  If you want to see what the amp is all about, build it with the same value caps.  Things I have done is use a Dual pot for tone and made a 6G3 stack.  Completely removes volume interaction and changes the amp a lot.  I have used a Master Volume when reducing the first bypass to 4.7 and first coupling cap to .22.  Major headroom increase, but different amp.

I have grid biased the PI with 2M2 and 3M3 and 4M7.  Each value extended and smoothed the onset of distortion.  Different amp completely.

Ask yourself if you are going to be using the amp live with a drummer.  If so, you may want headroom, if not the stock amp will get a great tone and distort rather quickly.  It is that distortion the stock amp has why so many like the amp.

Even a simple switch to reduce the first Bypass to 4.7 will change the amp and give it more headroom than a bedroom amp.

Your opening comments were that you wanted to build the amp with the same tone and feel as the original.  What I found is any mod or even using a different tube than 12AY7 in V1 changes the amp to a completely different animal.

Before I built my AC15 I was using it as my main amp in a 2 amp setup so I needed headroom.  I modded it with everything except a master volume. 

With the 2 attachments and a Blackface deluxe reverb OT, 6k6 8ohm, it became a clean amp with tons of headroom.  In this configuration I used a Celestion Blue, but in the original I prefer the Weber 12A125, 20 watts and no dope.

Since, I have checked out an original changed the PT to a Hammond 272BX, 600v CT, 115ma, which put my voltages more in-line with the original.  If you have Sluckey's file, the voltages on it are very close to the amp I checked and I did check it with 117VAC from a variac.

Removed the Deluxe Reverb OT and tried 2 different ones.  Both were good.  One was an 8k at 8 ohms and the other was 10K at 8 ohms.  I kept the 10K as the amp felt a little more greasy with this OT.  The OT came from a Hammond Tone Cabinet.

Good luck with your build and I hope my experience may have answered some of your questions.

[Fresh_Start]

Ed - Wow that was a lot of great insight! 

My plan is to build the amp stock except for little things like grid stoppers and screen resistors on the 6V6s, solid state protection diodes before rectifier tube, etc. IOW nothing that should impact tone or feel. However, I want the layout to leave room for certain specific things.

I'd looked at Hammond power transformers and completely missed the generic section. The 272BX specs look just about perfect. The ClassicTone PT I'm looking at has a 330-0-330 high voltage secondary. B+ might still be too high for vintage.

Speaker probably will be Weber 12A125-A based on research and input from Weber tech.

Thanks again!

Chip

[SILVERGUN]

My plan is to build the amp stock except for little things like grid stoppers and screen resistors on the 6V6s, solid state protection diodes before rectifier tube, etc. IOW nothing that should impact tone or feel. However, I want the layout to leave room for certain specific things.

Here's something worth considering as a possible tweak....it's a PI trimmer circuit section that was exposed over at TAG last year as part of a Dumble Tweed gut/rebuild.
Take a look at the combined value of the series resistance to ground after the cathode R and notice how it is closely equivalent to the plate load.
If you wanted to incorporate this on your 5E3 and keep stock values (56K) I'm assuming you could use a 47K R in series with a 10K pot and just move the signal tap point to it's new location on the wiper of that pot.(as pictured)
 
I like the idea of having the ability to dial in what would normally be a fixed variable from amp to amp (output tube to output tube), and I was able to use this to balance/unbalance the output to taste.
 

[Fresh_Start]

SG - cool idea!  Could easily put that on a trim pot.

Thanks,
Chip

[Fresh_Start]

OK - I have drawn up my schematic.  Many thanks to SLuckey for his Visio file!

The cathode switching arrangement is based on Geezer's idea discussed in this thread:
http://el34world.com/Forum/index.php?topic=19820.msg206813#msg206813

The concept is to use a 3-pole, triple throw switch.  "H" for high power should be stock 5E3 with a shared RC network.  "L" for low power is separate and un-bypassed cathode resistors.  "M" for medium power is separated RC networks for the power tubes with a trim pot adjustment between the bypass caps.

This extra switch will be in the "Power" hole and the power switch will be in the "Ground" hole.

I added an elevated DC voltage reference for the heater's center tap.  Since the cathodyne PI cathode is at about 40 volts, I'm shooting for around 60 volts on the reference point.  The "humdinger" may be a complete waste but what the heck.

The diodes prior to the rectifier tube are based on R.G. Keen's "Immortal Amplifier" articles.

The 330K grid stopper on the cathodyne is supposed to reduce PI distortion when the power tube grids start conducting current.  Highly recommended on the Valve Wizard (Merlin) site, and it will be easy enough to test whether it helps or hurts.

I separated the cathodes of V1 to allow for experimentation with the bypass cap value for the Bright channel.  On the Normal channel, I'm going to build it stock first.  Then I'll try a 220K plate resistor with 2.2K and 2.7K cathode resistors.  I really liked that sound in another amp so will have to give it a listen.

Please feel free to fly-speck the schematic.  Any corrections or comments will be greatly appreciated.

Chip

P.S.  I've abandoned the idea of switching between solid state (higher B+) and tube rectification discussed in this thread:  http://el34world.com/Forum/index.php?topic=19821.msg206816#msg206816

[bnwitt]

Chip,
Wow!  I cannot believe you haven't every built a 5E3.  My favorite amp of all time.  I like the Hoffman version with choke more than anything.  I tried a lot of mods but keep coming back the Doug's version.  Have fun building.