Turn the normal channel of you old Fender into a Plexi

[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? ...

[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

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 ([email protected]) 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 ...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).

[Dime59hum]

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

Cool.

[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

[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)

[Scott_F]

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

I had no idea there were so many here with rather extensive understanding's of thermioninc emission.....I guess it's addictive!!
Ultra-cool!!!!!
Jeff Seal

Jeff, I tried to send you an email a week or two ago. You are my fall-back position should I totally screw this Fender up! Check and make sure your spam filter didn't kill me off.

Either that, or your music career is taking off to hte point that us little guys can't contact you as freely as in the past!

[wixomwhat]

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

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

Yeah I'd buy it in a heartbeat just for the transformers alone.

You could buy it and put the output transformer in your Pro Reverb Scott, to give it the same output as a Super Reverb.

The Bassman uses a 4 ohm transformer that's the same size as the 2 ohm transformer in a Super Reverb.

Some guys think a Pro Reverb is a two 12" version of the Super Reverb, which has four 10's. But the Pro is lower in power and more like a Vibrolux Reverb than a Super Reverb.

If you're after a cleaner/louder tone, that's a good mod.

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 and sharp.

What kind of speakers are you using in your Pro Reverb Scott?

I used to use one original Jensen/Fender C12NA and one original Celestion G12M-25 blackback.

I think Pro Reverbs sound killer with Celestions...a pair of G12H30's would probably be awesome. Or a Vintage 30 and a G12H30.

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

You know those things were put there to help balance *relatively* unmatched tubes, and for hum control (although I believe the hum balance was in fact a different circuit (switching to DC for the heaters solved that I believe, or something related to that), I'd have to look. I guess if you wanted to get real anal about it, you could install a bias and keep the bias balance as well. That would allow one to match both *halves* of the power section as close as possible while also adjusting the bias dead on. There's an idea ...

Thanks John and Kent for the more technical explanation of what for me is a more intuitive process.

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.)

My brother Bruce ([email protected]) has installed two trimmer pots in some silverface Fenders so the amp has both a balance and a bias adjustment pot. It works.

One of these lifetimes I'll be born with a brain that can handle math and electronic theory a little better! I wish I could do that stuff, but my brain just won't work that hard.

Thanks for all the details Kent...

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.

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 ...just sounds better to me.



Lew

[Kent S.]

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

That must be a silverface Fender. The caps are to shunt high frequencies to ground and eliminate oscillation that could have been avoided with neater wiring.

I usually clip those caps off and remove them...but if you notice oscillation, you either need to correct the sloppy/excess wiring issues or put the caps back on again.

That's exactly what I was thinking, but I didn't want to come out and say it because I wasn't sure at making an across the board statement like that, I've also heard that Fender used tanks that weren't a perfect match in a couple amps (like same tanks with different in/out Zs, from other models), and also used them to correct the tone of the reverb ... don't know, sound plausible though. Stll I wonder if Scott's cap shorted on him, killing the reverb altogether ... Scott you still got that cap, if so which one was it on the schematic (gearhead site), and would you test that cap with a meter and see if it's shorted, I'm really curious as to what killed the reverb, if the cap in fact did it. If you don't have time, then don't worry about it,Thanks.

Did you do a blackface mod to the bias circuit yet? You should if the bias adjustment is currently a bias balance control rather than actually allowing th bias voltage to be adjusted.

Lew

You know those things were put there to help balance *relatively* unmatched tubes, and for hum control (although I believe the hum balance was in fact a different circuit (switching to DC for the heaters solved that I believe, or something related to that), I'd have to look. I guess if you wanted to get real anal about it, you could install a bias and keep the bias balance as well. That would allow one to match both *halves* of the power section as close as possible while also adjusting the bias dead on. There's an idea ...

[Kent S.]

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

not to mention, I did it to a 20 year old solid state squier bass amp....
it was cool that I morphed the tone like that, but.. it was horrendous, I'll keep that amp a clean amp, thanks.

The circuit is not even the same, and doesn't operate the same in something like that, they were talking all tube, and those circuits ... not a good idea ... don't do that again ...

[Kent S.]

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

................if you compare the 2 schematics,you'd see that the BF's tone controls come very early in the preamp...The Marshall's tone stack comes up very late in the preamp circuit...Marshalls don't give you as much tonal adjustment because of where the tone stack is compared to the BF Fender circuit...

John

Ah, I don't know about that ... that's a matter of perspective I think ...
The marshall gives you more control over the tone of the distortion itself, as it's later in the circuit and more harmonics (from the distortion) are being fed into it, the fender gives more control over the tone of the guitar itself ... if it's to flabby you can lean the bass up, to thin you can pull back the treble some ... all at the cost of gain however. Once overdriven though it doesn't do much to change the sound of the distortion though ( you can't very well get a scooped metal rhythm tone from a fender (unless you are running a distortion peadl into it, which places the eq after the distortion (or most of it ... ala marshall). the marshall on the other hand doesn't allow you the ability to same fatten out a tele, or thin out and brighten a LP, with the fender you can get the keep the tele from sounding to thin (well it helps), and get rid of any muddiness on the low side with an LP. The fender allows you to influence the *way the amp overdrives*, but again tonal flexiblity of the tone of the overdrive is limited; the marshall has overdrive tonal flexibility as it's strong suit, bit if the guitar is dark, or thin sounding, that reflects in the overdrive, and there's nothing you can do about it.
I guess we have a different manner of viewing the situation, depending which way one looks at it.
The earlier Boogs (Mark I, Mark II) sufferend from the fender thing bad, essentially you had one tonal character once overdriven (unless you had the 5 band eq, which was later in the circuit), although you could fatten up, or thin out out,or brighten up, or darken up the actual *guitar* itself. The best possible configuration shares both, one of the most useful setups I've run across was a little thing that I did one time for a friend, had a marshallized SF (extra 12ax7 added in standard plate to cathode follower config.), we ran off the first triode plate,thru a coupling cap,into a *tilt control*{my thing} , thru a preamp volume, into the grid of the second triode whose plate went into the grid of the third triode, came off the cathode of that into the tone stack, into a master volume (for that channel),out of that into the grid of the fourth triode, off it's plate on to where ever the guy before me routed the stuff too
(I didn't added the gain stages, that was there already), the volume control had been changed to a concentric controls for preamp/channel master, and the treble/bass I changed to concentric, where the bass knob was was now the *tilt* control. What it basically did was either cut upper treble, or cut bass ... So if the guiatr was to thin, roll off the highs, if it was to dark, roll off the lows, the amp had a lot of gain, so you could get the distortion (preamp that is) that you wanted, and you still had the eq farther down the line. Worked out very well, although it still could have been fine tuned a bit more, as the extreme positions were to much. The intent was to correct for the character of the guitar feed into it,without tying up the tone stack doing so. Food for thought ...

[what?]

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

i really didn't understand most of ths stuff, but could you mod this to a Marshall dirty channel to give it more "oomph!"? dont flame me or nothing if i'm being completely stupid. basically all that i got from all of your posts is to give something hotter distortion.

[Kent S.]

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

Cool Scott...My 66 PR has reverb on the normal channel,but it was done by me the "correct" way buy using 220k isolation resistors between the 2 channels...Torres used to show people how to have reverb on both channels,but his original method was just pure stupid... Try changing your .1 and .047 tone stack caps to both .02...The only other mods I did to that channel was changing the cathode cap and resistor values,but the outcome was similar to yours...The channel is crisp,more open sounding,has reverb,and grows some teeth sooner on the volume increase...If you want a drawing from me on how to get your reverb the right way on the normal channel,let me know and I'll scan it to you buddy...Enjoy your amp...One of Fender's best combos.I've had mine for many,many years..Would never part with mine! feel free to bounce some stuff off me anytime..
John

I'm guessin here, but the *dumb* way was to just run the two channels into the same point to the reverb, rather than go thru the voltage divider (the two 220k resistors). The reason I say this is on the tweed deluxes (I believe that the model I'm thinking of) those amps had two channels (normal and bright) that summed thru 220k resistors on their way to. the PI I think ... IIRC, if you didn't use those (the 220k Rs) the two channels would interact with each other, which might not be noticed if the other channel wasn't being used, but would become a real problem if both channels were used at the same time.