Turn the normal channel of you old Fender into a Plexi

[Scott_F]

Re: Turn the normal channel of you old Fender into a Plexi

Lew, there is a Utah orange and a fender reissue blue label in there now. I don't care for the low end farts. I picked up a set of Texas Heats from the new Emmience Patriot series.

Kent and Lew and John, thanks for all the tech stuff. My amp is some sort of bastehd. It has a sticker that says AA165 which is the blackface circuit, but upon further review it has the sliverfaced circuit in it. For sure. I have WEber's video on how to convert and I started the process last nght. I also ordered the proper parts for the conversion from Weber along with the eletrolytics. I'm basically going to redo all the caps and a few of the resistors, electrolytics, coupling cabs, plate resistors, etc., The cool thing about Gerald is that even though he's a bit high on his prices, he spells everything out very clearly for dummies like me. In addition, if you subscirbe to his tech support service (50 bucks for 6 mo), you get all your parts at 40% discount, including tranneis, speakers, etc.,.

That and I've met him a few times and geniunely like him. I'm thinking of attending his "Amp Camp" in November. I know he's a salesman and his job is to sell gear, but I respect salesmen. They have a job to do. If he gets me to where I need to be and I get there quickly, it's worth the price.

Same thing with the 5E3 kit from Bruce. Granted I could have bought the parts for less and all that, but I'd not have had the support and know-how I needed. Kudos to Bruce's kits and kudos to Webers mod and upgrade kits.

When I get back from my trip, I'll have everything I need. He's also got a kit for turning that normal channel into a brittish voiced "plexi?" channel. He's throwing in that info as well.

If you've not dealt with Gerald Weber, he's a good guy from my limited experiecne. His videos and amp books are first rate. www.kendrick-amplifiers.com

Oh, and Kent, I ended up hooking that cab back into the reverb jack and it worked, so I'm betting it was a tank or a cable. When I get a chance, I'm going to put that 2 spring stock tank back in to see.

Finally, this amp stuff is the most fun I've had in years in terms of a hobby. I know I'm a newbie, but I'm a pretty bright guy with degrees and street smarts. I ought to be able to learn and digest this stuff in a reasonable time. (i hope)

 

[Jeff Seal]

Re: Turn the normal channel of you old Fender into a Plexi

Hey Scott, I replied to your message...I'll try resending it...

...I'm afraid we're still playing the higher end low class establishments, but still hoping for bigger things...we'll see....

Jeff

 

[Dime59hum]

Re: Turn the normal channel of you old Fender into a Plexi

Cool.

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

The hum balance control is a differant circuit...you know those two 100K resistors up by the pilot light? It's related to those...maybe they're replaced by a 220K pot or something? (That's a guess...I'd have to look at the schematic.)

If memory serves correctly, I believe those provided a referrence to ground for the heater voltage which was originally AC voltage, which without that reference to ground would also hum. Later on though, when the heater voltage was changed to DC it that ground referrence was no longer needed because the DC didn't hum. I think that's correct, and if one side of the AC was out a bit from the other ... hum.

My brother Bruce (Missionamps@aol.com) has installed two trimmer pots in some silverface Fenders so the amp has both a balance and a bias adjustment pot. It works.

......

Thanks for all the details Kent...

Your very welcome ...

Oh...Torres takes alot of heat and I have seen some really sloppy work from his shop, but his book and his simpler kits (not the Super Dooper Texan fancy channel switching nonsense...avoid ruining your amp with that crap.) is good for familiarizing guitar players (not electronic engineers, but GUITAR PLAYERS) with how some of this stuff works.

Torres has a way of explaining this stuff that offends engineers but enlightens guitar players. So Torres has his place, at least when a guitar player is first starting to learn about the workings of his amp and just wants to learn some simple stuff about biasing or whatever and then get right back to playing his or her guitar.

I've never checked out his stuff, but I know the guy knows what he's doing, I can't comment on his work per se' ... There is merit to that way though, and to what he does, I agree.

Regarding the 100K slope resistor in blackface/silverface Fenders: I don't think that resistor sounds good any lower than about 91K. Some Marshalls sound good with 33K or the Tweed Bassman value of 56K and those lower values give more mids to the tone circuit, but in a blackface or silverface Fender, I think 91K is about a low as I like it, even with changing the tone caps to a pair of .02 caps.

Don't know why :smack: ...just sounds better to me.



Lew

Like I said, the cathode follower is a lot lower source resistance, the tweed deluxe had a CF I believe, now whether the bassman did, I'd have to look ... but that would shift the whole eq around. You can always raise it though, the *swing range* I gave earlier was just to mimic the amount of swing (percentage wise, roughly) that the jcm 800 had on one channel (the sweep control).

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

I like the Pro Reverb just like it is. It and the Vibrolux Reverb make great Tele and Strat amps because at volume 4 or so they'll start to break up a little when I sting a note instead of staying clean....

Off topic Lew, ... but ...I've heard great things about (ah, some at least) the Tremolux ... have you ever used one? I even saw a copy of the original Fender add that touted (even back then) that they had great distortion/sustain characteristics (per there volume or something like that, to me indicating that they could be overdriven rather easily and at low volumes).
Have you ever used one, and if so what did you think? Did they ever offer them with reverb later on?

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Lew, there is a Utah orange and a fender reissue blue label in there now.

What the heck are those Utah speakers like, I keep hearing people speak of them, but I always liked the JBLs the twins had, or the Emmience (I'll trust your spelling there) that some of the later combos had ... the old blue label alnico (whoever made them for Fender) ... and EV for general replacements.

...... It has a sticker that says AA165 which is the blackface circuit, but upon further review it has the sliverfaced circuit in it.

A lot of times that just refers to the preamp, I believe the BF and SF preamps are the exact same (barring maybe year to year odd ball changes, and sticking in whatever parts they had around to use them up), they are supposed to be the same. The big changes are in the power amp, and the PI was effected to I believe.

.....The cool thing about Gerald is that even though he's a bit high on his prices, he spells everything out very clearly for dummies like me. In addition, if you subscirbe to his tech support service (50 bucks for 6 mo), you get all your parts at 40% discount, including tranneis, speakers, etc.,.

Sounds good, tech support (support of any kind) is well worth it in cases like that, a lot of people try to cut corners monetarily ... not realizing that it could cost them more down the road ...

Same thing with the 5E3 kit from Bruce. Granted I could have bought the parts for less and all that, ............

Again, ... there you go ...

When I get back from my trip, I'll have everything I need. He's also got a kit for turning that normal channel into a brittish voiced "plexi?" channel. He's throwing in that info as well.

Man, are you on a role or what? Just keeps getting better and better ...

Oh, and Kent, I ended up hooking that cab back into the reverb jack and it worked, so I'm betting it was a tank or a cable. When I get a chance, I'm going to put that 2 spring stock tank back in to see.

Cool, I've got two medium sized three spring tanks in my Harvard Reverb II (CMOS S.S. amps, that were made around the time of the Super Champs) that are INCREDIBLY deep and long decayed. The tone of the reverb on those tanks are really warm with just a bit of upper sheen to keep from being muddy, you can get a GOOD amount of reverb before starting to get into that tin can/springy surf tone (you know where the reverb tone seems to change the tone of the guitar itself {it's really just the out of phase frequencies sustain over your ringing notes} making it thin and metallic).
I'll try to get the numbers off those tanks, and if you are interested, then accutronics can fix you up with the same tanks, but with the correct in/out Z and grounding schemes that your amp needs.
These tanks are very *studio* or *professional* sounding, very little boinkiness on sharp attacks like most springs do. They don't have that *sprung* sound that some of those old fenders have, the super reverbs where horrible for that, those long tanks with the two springs. Not nearly as dense, it's something about having more springs that are different diameters that reproduce richer harmonics (a more complex and natural reverberation) ,and the shorter springs being able to handle transients better or something. All I know is that these can give you as much, and as long a reverb tail as you'd want, add brightenss while being warm, and don't sound thin. Think about it.

Finally, this amp stuff is the most fun I've had in years in terms of a hobby. I know I'm a ...........

Well, the main thing for sure is that you are enjoying it as you go along ... can't say anything bad about that can ya? ... :laugh2:

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

would this plexi thing work with a SS fender amp?
like this one

http://www.musicgoround.com/store/inventorydetails.asp?id=269623

You need to download a schematic for it, and compare the way the gain is done ... some tone circuit in those opamp based amps are done with an inverting opamp, an opamp has tremendous gain, much more than a tube circuit (you also run the risk of burning something up) ... this really is a tube thing, all Scott did is put back a bunch of midrange (and hence available gain) that the fender tone stack takes out, he didn't alter the gain stages per se'. To do that he'd have to alter the bias of the preamp tubes (cathodes) and the low cut-off frequency of the gain (that cap that's in parallel with the cathode resistor). BTW the ADA MP-1 it's clean tube, and distortion tube mode ... that's exactly what it does, it changes the bias on the preamp tube and the low end cut-off Fc, so in distortion mode the tube gets pushed into clipping on almost anything you play.
What Scott is referring to isn't a plexi mod per se', he just means that the amp now has more overdrive and more mid character, hence compared to a typical fender, well ... I can see the comparison. I think his new lead channel still cleans up nice to. In the case of and S.S. amp though, you'd be better off cahnging the gain controlling resistors around the opamp that regulates it's gain (just like on a pedal), sometimes you can change out the gain pot for a higher value (depending on the circuit) for more gain. The short answer is you'll probably get a gain boost, but as far as the sound ... although I can't say with certainty ... ah ... NOT. If you're really curious though, you'll have to get a schematic from fender for it, or check here to see if they have it for download at www.ampwares.com check under fender field amp guide.

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Another thing to, while I'm rambling on about this stuff ...Scott here's an option that reverseable also ... if you wanted to you could at least have the cathode follower ... you wouldn't have to change that much ...AND the volume would come in between the triodes, so to some degree you could control the drive of the cathode following section (crunchy), while still controlling the overall overdrive from the guitar volume, the now convoluted tone stage would take care of basic low end trim, and subtle tone colouring, and contouring of the guitar itself (I'll e-mail you an emf graph of the tone curves if you'd like ... hey I got curious myself okay ... Let me know on that).
If you interested I'll lay out the changes for you and post to board (like the last thing I did). Bear in mind that a cathode follower will be lower in volume so you won't find that channel as loud, but it will overdrive more. You mind find it worth running that channel (CF) into the other channel (in which case you wouldn't want reverb added any way). That's more complicated though, and I think you're not looking to totally reverse engineer the amp, that CF is viable and fairly simple too though ... :cool3:

 

[Lewguitar]

Re: Turn the normal channel of you old Fender into a Plexi

Scott, Kent, and everyone:

About the Orange Utah speaker...Is it labeled Utah? Or is it labeled Radio Shack? Some of those orange Radio Shack speakers for guitar are pretty darn good! They were made by Pyle I believe...Ted Weber would know.

As for the Tremolux, the tweed version from the 50's is fairly similar to a 5E3 Deluxe. I had one for a while...got it free! Bruce and I were remodeling kitchens for a living about 1980 and we were driving into the dump to drop off the remains of a kitchen we'd just torn out and looked at the truck ahead and there was a tweed Fender amp bouncing around on top of the junk!

We followed the guy in and even tho you're not supposed to scavenge, you can bet I scavenged that old amp right up!

It was a nice tweed Fender Tremolux from about 1958 or 59. Worked too!

I fixed it up and sold it...bought my first Deluxe Reverb with the dough.

Anyways, the Tremolux is like a tweed Deluxe with vibrato. They never had reverb...even when Fender brought out the blackface version in '63 or '64, they didn't add reverb.

Generally, I only love blackface Fenders with reverb and vibrato...the reverb beefs up the tone even if you don't use it and adds some gain and balls to the tone.

That's the other thing that can be done to beef up the tone of 60's or 70's Fender amp with reverb: There's a resistor and cap that is the reverb recovery circuit. Can't remember the value, but it's a big resistor...maybe 3.3 meg. Change it to a smaller resistor and you'll get more balls out of the amp and add some gain...just don't overdo it. You'd need to change the cap too...experiment.

Lew

Lew

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Scott, Kent, and everyone:

About the Orange Utah speaker...Is it labeled Utah? Or is it labeled Radio Shack? Some of those orange Radio Shack speakers for guitar are pretty darn good! They were made by Pyle I believe...Ted Weber would know.

I don't know much about the Utah at all, however I had a Gibson G-30, my first amp,(no longer have it unfortunately) it was 30 watss, 1x12 combo, S.S. hi, lo inputs volume, reverb, treble, bass, speed, and intensity, and a foot switch jack for the reverb and tremolo ...it was clean and loud ... remiminded me of a Roland JC 120, but warmer, the Gibby speaker was crap, so I replaced it with a Plye Driver 12, 150watt ... that didn't sound that good, so I changed it to a Plye 90 watt, and that was very JBL like, that thing would chime like a twin but warmer ... straight clean but what an amp for a S.S.. Talk about loud, the thing would drown a drummer at 3. Man I wish I had that thing, for someone that could get their tone from and overdrive/distortion pedal ... that would be a perfect gigging amp. Built like a tank to.

As for the Tremolux, the tweed version from the 50's is fairly similar to a 5E3 Deluxe. I had one for a while...got it free! Bruce and I were remodeling kitchens for a living about 1980 and we were driving into the dump to drop off the remains of a kitchen we'd just torn out and looked at the truck ahead and there was a tweed Fender amp bouncing around on top of the junk!

We followed the guy in and even tho you're not supposed to scavenge, you can bet I scavenged that old amp right up!

It was a nice tweed Fender Tremolux from about 1958 or 59. Worked too!

Man, I never have luck like that ...cool indeed!

That's the other thing that can be done to beef up the tone of 60's or 70's Fender amp with reverb: There's a resistor and cap that is the reverb recovery circuit. Can't remember the value, but it's a big resistor...maybe 3.3 meg.
Lew

Lew

Yeah that's right it's a 3.3Meg in parallel with a 10pF cap, I think it balances/mixes the reverb return with the direct signal off the preamp.
Concerning the deluxes the one with out reverb had a .033uF mid cap, hey changed that on the Deluxe reverbs to a .047uF cap, also the vibrato channel had a 47pF cap across the volume control as a subtle Bright boost.
The bassman's had and interesting layout to their tone stacks, a bit different with that .01uF mid cap arrangement. I was looking over some of the older amps that fender made, and for guitar players looking for a bit more control from the eq some of the older stuff is really different than the standard BF/SF eq. I'm not just talking about the earlier E series eq either, some of the bandmasters had some neat stuff, a bit perplexing with the *tap* connections on some of the pots, and the deep switches where cool on some of the bss channels ... I remeber the schematic but not what model it went to ... :laugh2: To much to keep track of, cool nonetheless. Thanks fro the update on the tremolux Lew ... but you never did tell me, how was it at overdriving at lower volumes? And to the guy that asked about the Vibrolux, yeah I looked at the schematic, it's the same as what Scott has, just follow that little schematic that I posted. You know I can't remember which model it was, but one or two of the fenders had a 4k7 mid resistor insted of the 6k8 ... for some reason that's bugging me that I can't remember. The Tweed bassman had the cathode follower arrangement though, that's the one I was trying to remember for Scott.That's not on the ampwares site, thats at ...
www.muzickicentar.co.yu/scheme/sheme.php under fender amps of course, that site only has a couple, but some aren't on the other site.

 

[Lewguitar]

Re: Turn the normal channel of you old Fender into a Plexi

Kent, you are a real asset here. Thanks again for all the details.

I have an original 5F6-A Bassman from about 1959 or 60. I think it's one Fender used as a factory demo or something. It was recovered once (I think at the Fender factory maybe 40 years ago) with the original tweed so it looks original. There's no white lettering whatsoever on the chassis panel, but it's a stock Fender 5F6-A. It's the best amp I own, but it's so loud I don't play it much. It's remarkable how similar the feel of this amp is to my Marshall...and how crunchy it is when it's cranked up above 4. I only hear that particular style of crunch from a 59 Bassman or Marshall...amps with the Bassman style preamp and cathode follower. My other amps overdrive beautifully, but that Plexi/Bassman crunch isn't quite there. Gotta go...heading for the high country again today. Climbed South Arapahoe Peak yesterday: 13,500 feet! I'm thinking I'll head up to Rocky Mountain National Park today...it's only a one hour drive from where I live.

Take care, Lew

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Kent, you are a real asset here. Thanks again for all the details.

Well people have called me everything froman asset o an ^%$ minus the *et*, and everything in between ... :laugh2:

I have an original 5F6-A Bassman from about 1959 or 60. I think it's one Fender used as a factory demo or something. It was recovered once (I think at the Fender factory maybe 40 years ago) with the original tweed so it looks original. There's no white lettering whatsoever on the chassis panel, but it's a stock Fender 5F6-A. It's the best amp I own, but it's so loud I don't play it much. It's remarkable how similar the feel of this amp is to my Marshall...and how crunchy it is when it's cranked up above 4. I only hear that particular style of crunch from a 59 Bassman or Marshall...amps with the Bassman style preamp and cathode follower. My other amps overdrive beautifully, but that Plexi/Bassman crunch isn't quite there. Gotta go...heading for the high country again today. Climbed South Arapahoe Peak yesterday: 13,500 feet! I'm thinking I'll head up to Rocky Mountain National Park today...it's only a one hour drive from where I live.

Take care, Lew

I'll have to check up on differences around those models, like I said some of the bassmans and especially the bandmasters were a bit odd to say the least in regard to the tonestack ... A lot of the various models had different preamp tube plate voltages as well ... another interesting twist in the mix.
Be safe in your climb, and enjoy!

 

[mmguz]

Re: Turn the normal channel of you old Fender into a Plexi

Could this modiffications works in a fender hot rod deluxe amp?

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Could this modiffications works in a fender hot rod deluxe amp?

Again, check the schematic ... I've got about five things going on at once ... post a schematic and I'll be able to advise you better ...

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Scott ... I'm currently (read this to mean :when I get time) working up a comparison of the circuit differences between various Fender Bandmasters and Bassmans ... time permitting I'll post them to the board ...

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

Here are a couple comparisons, some old Bandmasters and some Bassmans, I tried to eliminate some clutter by simply saying cathode follower at some points (if that's not specified then you know its a common cathode) ... again one big draw back is that the CF is a lot lower in gain (hence on all the designs additional stages following (not shown here of course). Using one without additional stages might result in a situation where you can't get your lead tone loud enough compared to your clean tone. Anyway, here are some interesting options tonally in regard to your tone stack.

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

And the second ...

 

[Alvin Lee Fan]

Re: Turn the normal channel of you old Fender into a Plexi

Kent, sorry, can't upload the schematic for the Deluxe Reverb II. The file is too large. Let me know if you still want it and I can mail it to you. It's not that big, only about 950K, but the upload limit here is 100K.

 

[MrHeavyMetal]

Re: Turn the normal channel of you old Fender into a Plexi

I own a 100-watt Marshall 1959SLP Reissue with all Mullard tubes and a 4X12 w Vintage 30's. This thing is SO DAMN LOUD that I can start a riot in a 3 block area. Beware the Plexi. MrHM.

 

[Kent S.]

Re: Turn the normal channel of you old Fender into a Plexi

To further tweak the reduced effect of the tone controls in Scott's gain mod ... replace the 250k-A bass pot with a 500k-A pot with the wiper connected to the CCW lug unlike the present condition. Replace the mid cap (.047uF) with a .1uF cap, and the bass cap (.1uF) with 1nF(1,000pf); add the 120pf cap in parallel with the 250pF treble cap (either straight in parallel or as previously explained). The controls will now have a bit more effect the treble control is the main control, while the bass control trims of lower bass from about 120Hz. down (subtle about 6dB or so). The bright switch can be saved for a sensitivity switch or a contour/treble cut option. This will help make the tone controls more useful. The bass control will also function in the correct manner (unlike the reverse manner caused by lifting the ground resistor).