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The need for tweed....

C

-CB-

Epic Member
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Musical tastes vary.  Mine are very conservative.  Give me what works.  Don't make it fancy.  Just make it good.

I am, as I have found out, blessed and cursed by the spiritual entity (ghost if you will) of Clarance Leo Fender.  He's a nice guy.  Won't leave me be though. 

A while ago, a decision was made to build up two amps.  Bassman and Super, using very similar circuits
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Here's one all set.  Note the fuse for the B+ down at the end of the chassis, and also the voltage reduction.  This is the "Super" chassis, built more or less like a 56 Bassman - NOT - the oft copied 59.  Why?  The 56 uses a cathodyne inverter, which to me, sounds more 50's and "tweedish".  Dont worry about lack of gain.  The amp will hold up nicely, and puts out in the neighnorhood of its rated 40 watts.

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Two cabinets freshly shellac'd.  You see the 4x10 Bassman and 2x10 Super

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Tough call here.  Lots of implications.  I would never ever try to pass off what I have built as a Fender product.  First off, I do a better job.  But moreso, there is a deep respect for Leo, and all his employees from the Fullerton days, when great things were done.  I personalize the amp.  This one is Vics (the 4x10 tone monster).

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Getting some use.  Straps are for sissies! (or those who can remember to pack one)

 
Interesting. I've thought about trying to build my own amp since I'm handy with a solder iron. That super would be fun. What would an average guy have in $ into a Super or a Bassman building one from parts?
 
There is great variability to the parts.  Experience has shown - USE THE BEST YOU CAN POSSIBLY GET, regardless of the price.

Think in terms of Mercury Magnetics output transformer, either MM or Hammond Power transformer.  Hammond choke.  Ceramic sockets, CTS pots, Switchcraft jacks, Carling Switches.  Chassis... shy away from Weber.. I've had problems with his welds on three different chassis, but.. its a fixable thing (rivets), so if you like his stuff, fine.  Speakers..... very tough choice.  Jensen reissues dont cut it with me.  The Weber... over rated, but good.  To me, the speaker MOST like the old alnico Jensen of the 50's/60's is the Eminence 102 Alnico.  You can get them on "that great auction site" for $35 to $50 (shop, you'll save!).  Cabinet, I've been happy with the Mojo cabinet - very well made, but I dont like their heavy handed use of spray glue inside.  Its a "-CB-" thing, since I like to finish the inside too, and the glue can be shellac'd but if you want a real smooth finish, you need to strip the glue off the exposed wood.  Just extra work.  The cabinets are built REALLY well tho... so I put up with that.  Really well - correct thickness pine, fingerjoints to die for, correct hardware, correct baffle.  They did their homework.  I like Zinsser Amber Bullseye Shellac on them.  Cut it 50/50 with denatured alcohol.

There is great variability with choice of capacitor.  To me, the Vishay/Sprague Orange Drop is good, but too "clean" for a tweed amp (except in a few places).  The Mallory 150 is a bit better.  I like to think of the Orange Drop as the "JBL" toned cap.  Big round bright clear.  Mallory's are darker, a bit gritty if you will too.

Resistors - forget carbon composition.  Just go double the wattage of what you need, and use carbon film or metal film.  They are MUCH quieter and to me, dont make a hill o beans difference IF you use the right values (remember carbon comp resistors have all drifted value with age).

Power filters - Sprague TVA Atom, use none other.  Wire - wax impregnated cloth covered solid core pushback wire does it for me, since its easy to use.

Having said that - think in terms of dumping a thousand dollars into a Super or Bassman, maybe just under that for a Super, two less speakers and very slightly less expensive cabinet.

If you use the best quality parts, if you are thoughtful, and careful, and consider much before assembling.  Then when you are done, you will have an instrument (amps are instruments) that will last as long or longer than the 50's originals.  It will ooze tone.  It will sing and stand up the hairs on yer neck. 
 
Gregg - Don't you have enough projects already? What happened to the tabletop body?

CB - You have a schematic for the 5E6b? I can only find 5E6/5E6a.
 
jackthehack said:
CB - You have a schematic for the 5E6b? I can only find 5E6/5E6a.
Click to expand...

The 5E6b is my own advancement of the 5E6a, its not a Leo design.  The differences are minor.  My "b" has four inputs, hi/low like the more modern Fender designs (the next incarnation of production really).  It retains the two channels, vol vol treb bass presence.  There are some minor changes to the values of things in the circuit itself, in the interstage negative feedback loop, presence control, bias is adjustable.  So its "my take" on the 5E6a, done as a 5E6b.

Of great importance, is the keeping of the HUGE choke that all the B+ runa through.  That choke is critical, a make/break part of the tone of the amp.  One must have the correct inductance... just enough to deal with the ripple.. BUT NO MORE.  The impedance must be relatively high too. Naturally, its DC current capability must be sufficient as well.  Size... so it fits.  But you get that inductance too high, or impedance too low, and you lose the tone.  Basically, the choke has got to sort of be on the ragged edge of falling apart to be good!  There is actually, DC saturation in the choke itself (shh I didn't say that... forget you heard it).
 
I am pretty handy with a soldering iron as well, And have a background in electronics ( solid state not tubes, But I can learn tubes)

I would love to build my own amp as well- Having visited a few amp forums, I am more comfy with the crowd here.

I would like to see a separate, dedicated topic in the forum for home built amp projects. 
 
Solid state...

If you work with tubes, get comfy working with 450vDC or so.  Safety is an issue, since the voltages are enough to kill you.  However, most first year students would be at home with tubes, as most of the circuits are nothing more than Ohms Law and elementary AC application of filters and resonance (power supply and tone controls).  You can copy a power supply... once you learn how they work.  And the tone controls have been worked out for you already - and there's good tools online with tone control simulation, so really, just Ohms Law.

Some simple home made tools to make the job easy (ya know guitar builders do that too!) and you're in business. 
 
It's not the Voltage that kills, it's the amps.

I've had my hands in 12,500 volt equipment many times,  I've been bitten hard with 277vac,  Voltage hurts, amps kill.
 
Its a combination.  Its ohms law.  And yer body is the resistor.

Think in terms of 450v at 250ma - your toast

 
Couple of questions for CB:

1.) One of the many projects laying around the house is a '79 Fender 75 amp, which I found in a thrift shop with the power cord cut off for $30. One of the reasons (besides my ever ncreasingly bad Wamoth habit) I've never gotten around to this that there aren't any good electronics stores in the area in which I'm stuck in, and sourcing all the parts in one place is really painful. I've tried a couple of places that offer rebuild kits for more popular amps like Bassman/Twin Reverbs, but they don't even respond to emails about the question with parts lists. The amp works, but basically needs a complete set of caps and a coupel of pots and one switch, but might as well redo it all while you're doing it, eh? You know of any place online that offers a complete selections of parts of this type?
2.) I'm negotiating to trade my Blues Deluxe and another couple of amps laying around for a Fender SuperSonic, while I realize it probably has a PCB rather than a breadboard, what's your opinion of it otherwise?
 
You'll not find a kit. Most techs consider them "terrible", but really, they're not bad, just not typical older Fender.  They just didn't make many of those amps, they're obscure, they're not considered the "tone monsters" of the 50s/60s/early70s ams.  Consider - Fender was on its deathbed at the time.  Tubes were now out of production seemingly (Iron curtain hadn't fallen yet), guitars were mostly being made in Japan... dark days for Fender.  But its a good amp, and if its not rusty... YES! Fix 'er up! By all means!

These amps have a sort of "reverse" output (it works, just not typical) and also have whats called "UL" or UltraLinear output, where the screen grids track the plate voltage by a certain percentage with the use of "UL" taps on the output transformer.  The power supply is also a bit unusual for a guitar amp, being a full wave bridge, not just "full wave" with center tap.  It runs 500vDC on the plates of the 6L6s and needs to be UL to do that.  They claimed 75watts from that setup, but its more like 60-65.

Looks like you need a pair of 220uf @300 caps, three or four 70@100 caps, three or four 20@500 caps, three or four 25@25 caps... get 25@50.

What I'd do is print this schematic
http://www.geocities.com/twoseriesfenders/fender75.pdf

Then look for every capacitor marked with a + meaning its an electrolytic.  Use a different color highlighter for each value.  Mark them on the schematic.  Then count the marks... add an extra of each one on your order.  Vishay/Sprague currently does not offer a 220@300 (or 285 as on the schematic).  The only alternative of any quality at all... is the Illinois cap.  They offer a 220uf @300 (or is it 350 still ok).  All the rest, please do get TVA ATOM capacitors.  For the 25@25 just get 25@50, insignificant size and price differences and they're last longer.  For the caps - get all you need from MOUSER electronics (www.mouser.com).

Contact me with PM if you need the correct power cord, I've got a bag of em here <gggg>.

I'd not change the pots and such unless needed.  Get a can of ProGold spray and just clean em out.  Same with jacks.  They're nickel plated and have a switch leaf that goes to ground to ground the input when its not being used.  They get cruddy, dont ground, and result is hum.  Clean them too.

You'll find some of the caps - typically the 25@25 are too short to go from eyelet to eyelet.  They nearly always go "across" a resistor when on the board.  Just lift one end of the resistor, and twiddle the cap around the resistor, solder to the resistor, then put the resistor back in its eyelet.
You might need to lightly scrub/scrape the resistors leads as they're old and tarnished badly by now (mo betta solderin).  Mind the polarity of the capacitors, or they'll go bang, and make a mess - TVA ATOMs will sound like an M80, and toss some aluminum shards if you do that.  Er... yes I have done that ONCE (its enough).

It appears that the circuit has a bleed down capability - to self discharge the caps - when the standby switch is in the play position.  DONT TRUST IT.  Check check and recheck your voltage, and make sure your meter is working - BEFORE you touch ANYTHING.  Once you are confident the circuit works, and is discharged, you can use it, but still check.

Blues Deluxe.  I'd not trade that for a SuperSonic, personally.  Guess it depends on where your tastes are.  Original series Blues Deluxe's were nice amps... if somewhat unreliable, but there's things you can do to make them more roadworthy.  I seem to recall several places online that have all sorts of tips and tricks for that, though I've never done 'em.  I DID do some mods on a Blues Jr once.  Replaced jacks pots etc etc.  I felt it was pretty good to go when I got done, and I never heard a peep from the fellow I eventually sold it to... as far as I know its still goin strong 10 years later.

You get stuck on that 75, let me know bout it, we'll unstick ya.

 
Thanks for the tips; a while back I had a bud that had bought one of these new, while obscure, in proper working order they have one of the best "clean" channel sounds out of a Fender tube amp I've ever heard for more jazz type sounds, and if I'm not mistaken this is the first amp done with a separate "drive" channel tube preamp, although it takes a bit of futzing to get the "right" sound out of the drive channel. What I really like about it is the "step-down" switch to kick it from 75 to 15 watts (claimed watts, whatever), which I wish more amps incorporated as a std. feature, great for practicing in the house. Again, where do you source the caps and other parts?

There's no rust, standby switch is broken in the "On" position, haven't cleaned pots, but lead volume pot feels broken internally and stuck at maybe 60%, original Fender "special" 15" speaker is in fine shape, but may replace and save the original in case I ever decide to sell it. I need to replace all the tubes, would you recommend maintaining the 7025's or switching to ????.

The Blues Deluxe is a reissue, can't say as I have any complaints with it at all after replacing the stock speaker with a Celestion Vintage 30 other than the they could have left the "Drive" channel off the amp as it's worthless as far as I've been able to tell. I went to Guitar Center to check out the electronics on the new Fender Strat VG guitar and played the SuperSonic and was pretty impressed, has a lot more "crunch" than the Blues Deluxe, especially when playing humbuckers through it, and I like the Bassman/Vibrolux voicings on preamp switching. Besides, I haven't bought an amp in more than a year...



 
jackthehack said:
.....they have one of the best "clean" channel sounds out of a Fender tube amp I've ever heard .

.....Again, where do you source the caps and other parts?

.....standby switch is broken .....lead volume pot feels broken internally .

.....I need to replace all the tubes, would you recommend maintaining the 7025's or switching to ????.

.....The Blues Deluxe .....they could have left the "Drive" channel off the amp as it's worthless ....
Click to expand...

In the "watt-wars" period of the late 60's and all of the 70's, Fender strove to offer CLEAN amps, free of distortion, and of course to offer as much power as they thought they could claim from a set of tubes.  I mean... they could have gone to 6550's, gotten real power going.  Or gone to 7881 tubes (super 5881s... like a 6L6 on steroids).  That would have yielded 75 watts.  But tubes were getting scarce... 6L6s were the most popular of the power tubes, so they stuck with that.  A by product of running the supply rail up in voltage, and being able to do so with UL taps on the transformer, is that it makes it really hard to actually "hit" the top of that supply and start to clip.  And when you do... arrgh its not quite as nice as a nonUL amp.  Yes, all UL amps are, by design and the nature of their genes, clean machines.

Parts source... didn't the link work up there?  http://www.mouser.com  MOUSER Electronics

Replace what is broken, clean what is not broken.

You dont need to replace all the tubes.  Preamp tubes last next to forever.  Power tubes, last a LONG time at less than full output.  I mean a LONG LONG time.  I've personally seen Twin Reverbs that were used daily for 4-5 hours five days a week, but in a practice room (what overkill, but hey it was tax dollars).  The amps were from the early 70s.  The tubes all original.  The amps basically went to do two concerts in the school auditorium each year, and the rest of the time in practice rooms.  No need to change the tubes, even power tubes.  They were fine.  At the most, you can change the power tubes, but you might not have to, and that would be a "last thing to do" measure if the tubes you have proved to be unsuitable.  My guess is that if they're original, they're probably ok... why?  Even with hight plate voltage, Fender biased the amps "clean" and the UL taps make the tubes able to handle a whole lot.  I am seriously doubting such a clean (loud) amp got cranked real hard.  Using it on 5 or 6 is going to be VERY loud.

You do need to learn how to set the bias voltage.

Put a pedal in front of the BD.  Find a nice old (original, black, huge) Marshall Bluesbreaker pedal.  I've got an easy mod for that, and it'll be all the pedal you need for the BD.

 
Mouser.com link great, thanks!

I have a couple of pedals I run in front of the BD, just like the pedaless "crunch" of the SuperSonic better....

The 7025/12AT7 tubes are original and fine; 6L6s are a different story....  See pic below; looks like one of the original tubes was traded out. Guide pin on black-topped tube broken off, but glass intact. White-topped tube has pieces of white crap floating around in it, like the piece visible in pic stuck to glass lower left of center; so I probably need to swap this pair out, suggestions?

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yah, ok mismatch bad, also..... the one is toasted.

THE tube to get is the new-oldstock 7581, in a matched pair.  Those are good for 35w each in a standard P/P config and will be the cleanest longest lasting tubes you can stick in there with no mods.  They bias the same, and they have the same heater current, so no mods.

Barring that... whew... I'd look seriously at coke bottle EH/Sovtek KT66's.  Those big bottles let go a lot of heat, and they are rugged, decent sounding tubes... but you'll have to take the alligator jaws off the sockets and replace em with spring retainers (not a bad thing actually).
 
I like the 7581 idea, not having to mod/rebias is a big plus. There doesn't appear to be a lot of NOS available, but I've found both Philips and GE NOS matched pairs for $150/pair, my gut is to go the GEs:

NOS in original boxes and white box. This is a really nice USA made version of the British classic, and will work fine wherever a KT66, 6L6GC, 6L6, or 7581 is called for. Very nice Gm match on these. A few pairs made for RCA or Westinghouse, all are GE made with the GE factory codes.

Your call?
 
Here's what I'd do.

First, I'd fix up the amp, then reach into my big box of tubes and grab a set of 5881WXT+ from EH/Sovtek.  Stick those in there to test, tune, play the amp and see how you like it and make sure it all works ok.  If you have a real issue, better to blow one of those than the $150 set.

Then, I'd go get some 7581s... I have the Phillips here for myself, a few "quads" set aside for use in a Showman thats converted to bass.  The GE are probably pretty close, maybe better, maybe not.  You'll not be driving them to their limit, so the breakup on them will be very minimal... the result of the way they're used in the circuit.  All the breakup is preamp driven... not a bad thing... if done right.  The idea is to have just a little bit of breakup over several stages, not all at once, which sounds buzzy. 

So, maybe get some 5881WXT+ or other inexpensive but decent set, get the kinks worked out, then go the NOS set when you do.  Heck, you might LIKE the cheapies, and save $125 (expect to pay about $25 for the set of cheapies).
 
Right on CB!!!!!  I still think that deep in the soul of all blues and classic rock players beats the heart of a tweed amp lover.  They might not know it because they may have never had the chance to play an origional Fender Tweed.  First amp I ever owned was a 59 Tweed Tremolux that  seared it's tone into my head in the early 70's.  But my bad, I wanted a huge wall of amps to look cool.  So in came the Ampeg V4 that shook walls.  Next the Mesa with a Marshall cabinet, still never happy with my sound.  Finally I came home.  I suggest you all A/B a vintage Fender amp against their new stuff and you will hear a huge difference.  With a tweed amp all you need is a guitar, a cord, and the amp like CB in the picture.

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