Wednesday, October 14, 2020

My personal 1969 Deluxe Reverb


This is my personal Deluxe Reverb. I just bought it from Division Street Guitars in Peekskill NY. Great shop, give them lots of business!

I added the blue jewel on the light bulb. Blue on silver is just right for me.

This post is just about general routine stuff. Amp had the rectifier tube removed and replace with a couple of 1N4007 diodes. Gross...... Well, at least not for me. 



Fortunately the power transformer is intact, easy fix. Clip thise sad diodes out and put the yellow wires back to pins 2 and 8:


Next was just the filter caps. Sad, old and leaking. I didn't keep the sleeves this time cause, well, who cares? It's a silver panel amp! You can see they are leaking badly. Please don't leave stuff like this intact for the sake of "collectibility." Remove and replace.


I like to put two 80uf@450v caps in series with two 220k 2 watt bleeder resistors in the first filtering stage. Keeps me from getting zapped! And if you have an amp that has 500+ volts sitting there before you hit standby, this is safer. 80+80 in series is 40uf....... Perfect for a tube rectifier where you do not want to go over 50uf.


Next is the 470 ohm grid resistors. One was replaced but I just did both. You can also see those .001 capacitors from pin 5 to ground. Gone. Never needed them! The AB763 circuit is just better.




So I'm not the biggest fan of those "Brick drop" capacitors. A bit harsh. I replaced them with a mix of Sozo blue capacitors (lovely!!!) and some old Ajax caps and Sprague Black Beauty caps. 



In the phase inverter I went with a .002 cap feeding it from the preamp. The silver panel amps use .01 which I don't like much and the black panel amps use .001. I like it somewhere in between. You can freely experiment with values there and see what you like. 

This is my first amp with reverb since 1992! New sounds for me. Absolutely beautiful voice. I used all American and European NOS glass. So hopefully the public will get to hear this some day when Covid has passed. And it shall pass like everything else. Let's keep it real and get through these times together. God I miss live music!


Of course, these old Fender amps have a way of getting away from me. So as long as I don't sell it.....

I should add, the late 60's Fender amps with the removable baffles like this one are some of my favorites. They're consistently great sounding. I'm not a fan of the tweaks they did but those are minor and it's a piece of cake to put them back to the black panel glory. The transformers are pretty much the same, this uses a 5AR4 rectifier rather than the 5U4. That's important. The amps made soon after this are very good still, right up until the 1980's. They're all hand wired. But these late 60's amps, you have more fun options. If I wanted to I'd replace the baffle with Baltic Birch. Mojotone makes those ready to install. I've done this for clients and for a couple amps I owned that had cracked baffles. The later ones the baffle is glued in. Bah! Why???!!! 

So do consider one of these if you have fancy champagne taste on, well, a good wine budget. No they ain't beer sadly, but still priced more reasonably than the vaunted black panel amps..... 

Sunday, October 11, 2020

My 5E3 Deluxe "UN"-clone, simple mod for tight bass, more clarity. (As featured on 'The Truth about Vintage Amps with Skip Simmons"


Recently I was interviewed about an amp I built, one that is my main gig amp. Steve Melkisethian of Angela Instruments played it about a decade ago and it left quite an impression apparently. He commented on the low end and how it held together nicely. Isn't your typical "Neil Young dirt box!"

Truth is it's all in the big knobs folks:



So, obviously that's not true. But there isn't much to it. First, a bit of background. I have no qualms with the stock 5E3. I'm a big fan of Neil Young and his sound and I've always liked the 5E3. I just wanted to build something a tad bit more modern for my own use. I prefer a tighter sound, something that is more clear. Most of my gigs I'm not using a mic. I've had little tube amps literally get swallowed up into the mix. I can't actually use that. I need to hear myself to have a good time. 


The first thing I did was what I usually do: 47uf capacitor on the first stage, followed by a 22uf then an 8uf. That 47uf makes a difference in sag and compression. The original is 16uf. I also like that first stage to clean up any unwanted 60 cycle hum right off the bat. 


The second thing I did was use a larger cathode bypass capacitor across the 250 ohm 10 watt resistor. You can experiment with values there, I used 100uf @100V. The Vox AC30 uses a 250uf cap there. Deep bass.

Photos of power supply and cathode bias arrangement.



Now these things helped me achieve my goal. But that's not all. The next thing I will freely admit I did not come up with on my own. I mean, same with what I discussed above, these are all things I just learned from others.......

I had a really good client when I owned Leighton Audio in Portland Oregon. He was a bit of a perfectionist. My eyes would roll whenever he came by cause I knew I'd work a little harder. But every time I worked with the guy I learned something new, so I always appreciated not only his business but also his "can we make it better?" attitude.

He brought in a 5e3 clone that he bought somewhere. Nothing special. It had a problem, bad tube or something. So when I got to it I noticed this 3.3Meg resistor that "shouldn't be there." I said in my mind "well, that's wrong" and yanked it on outta there.

He picked up his amp, got home and said "problem is fixed, but this amp had such a great low end and now it's flabby. I knew exactly what was going on, it was that mysterious resistor. So he brought it back in, I replaced it and we were both happy. Him to have his amp the way he liked it and me cause I learned what I wanted to do to my own amps.

So, what exactly is this mod? I can't say I know why it works, I can just say what the result is.

Take a 3.3Meg resistor from the last stage of the power supply and connect it to the grid of the phase inverter, the pin attached to the 1 Meg resistor. That's it. Voltage goes up on that grid and the cathode, amp sounds more clear, has tighter bass and if you like that hooray. If you don't simply remove it.

Photo:


I was asked if I would put it on a switch..... Switches aren't for me personally. I have enough on my mind when I'm on a gig. Volume, tone, guitar. That's as much bandwidth I need on my equipment so I can focus on the music. But if you prefer a switch, go for it and tell me your results.

Other bits about the amp... I used Mogami wire throughout the signal path. I learned this from working with an ace studio technician named Tim Hatfield back in 1992. It's nice to work with and sounds warm and clear. It's finally widely available again. I could find their shielded stuff from many sources but had to go through some channels to get this copper gold back in the day! I've used it for mic pre's, pedals....




I also used nice Black Cat capacitors in the preamp along with Sozo caps as well. Good old mica cap for the treble....




Transformers are Heyboer / Mojotone Deluxe Reverb power transformer (lower voltage, more current, runs cooler!) and just a Mercury ToneClone for the output. I didn't want to go with bigger iron. For me it's a balance between high quality components and average. Black Cat caps aren't the best in other words, but they're then best for this kind of thing in my opinion.


And hey, this mod works on Princeton amps too! I like a Princeton, I've never loved them. They sound harsh and unbalanced to my ears when you push them. Not useful to me. I prefer my Deluxe Reverb for a 'modern' Fender amp.

Recently I had 2 Princeton Reverb amps come across the bench in one day. One was a museum quality 1965 that I was probably the first to turn a screw on. Original tubes, everything. Not a stain or scratch. I left that one alone. 

The second was a butchered 1973 model. Someone had done plenty of "wha????" stuff to it. I needed to restore the thing so I figured I'd see if I am crazy thinking this mod is as good as I think it is. 




Once I got the bugs sorted I blasted it and got that awful sound I usually get with the Princeton Reverb. Lovely at low volume, just awful to my ears at high volume. For me the 5e3 with it's simple volume and tone arrangement, that works for me. Not to mention the softer warmer cathode bias. With the Princeton's grid bias, scooped mids and more complex tone stack, it just never suited me. 

Spot the 3.3Meg resistor:


It's right on the .022 cap feeding the phase inverter. The Princeton and 5e3 Deluxe have a very similar phase inverter. 

Disclaimer: what you see above is not my work! It's sloppy but functional. This job was for a client who needed to keep the cost low. I would typically gut something like this and do it over!!!!

I've seen all kinds of complicated mods done to Princeton Reverbs. I've seen the tremolo scrapped so someone can re-do the whole phase inverter to be like a Deluxe Reverb. Ugh! The tremolo is the thing I like the most in a Princeton!! Try this one simple mod first if you want more headroom. 

That's it today. Hope you got something out of this article. Please feel free to leave questions and comments below!

And here's me yammering on about this stuff on Skips podcast. I think he's doing a great service to those who like to play with capacitors! Thanks Skip!



-J













 

Wednesday, September 16, 2020

1940's Kalamazoo KEA

 Curious little bargain tube amp that I got to bring back from the dead..... a 1940's Kalamazoo KEA.





This is one circuit that I'll admit I have little idea of how it works. It has a single 6SJ7 driving a pair of 6V6 tubes. How this is achieved I do not know. It's not parallel single ended. Look at the schematic!


The other challenge was finding a 10" speaker that is shallow enough to fit in such a tight space. This project sat around and almost made the 'sold for parts as-is' pile. Nothing fit! But fortunately I was able to find an old CTS speaker in the bowels of Southside Guitars deep in the basement under discarded case parts...... It was dead so we had it re-coned. Speaker had the perfect holes to mount the output trasformer.



In the end it's a fantastic little amp. Not a fuzz box, very clear and defined. These are financially not worth the effort, you'll likely lose money doing what I did. But we were all so blown away by it's charming tone that an employee bought it and will be tracking with it! I have an affinity for the 6SJ7 tube. My favorite preamp of all time so it's not surprising how much I like this amp. 


Did the usual, changed the caps etc. Fortunately both transformers were good. I do not think this amp would work well without that odd asymmetrical output transformer. So make sure that part is happy before you commit to one of these. 


J






1947 Fender Model 26 "Woody" amp

 I thought I'd share about this one.... very rare bird indeed. A Fender Model 26 "Woody" circa 1947.




This came through Southside Guitars with the matching lapsteel. Unfortunately both transformers were destroyed. The good thing is I managed to buy some period correct NOS iron that worked perfectly. I don't think one needs to be too precious in what iron one uses as I believe Fender used what was available in these early days. I could be wrong about that but either way the amp turned out to be fantastic sounding.


I needed to replace every capacitor in the house and some resistors. Curiously rather than using a 250 ohm 5 or 10 watt resistor for the cathode bias circuit, Leo used 2 500 2 watt ohm resistors going from pin 8 to ground with a wire connecting the two with a single 25@25 volt cap on the board. I replaced those with some pretty NOS 500 ohm 5 watt wire wound resistors. 


The speaker was shot but original so I had it re-coned. Always the best choice I feel, especially with these. There is no place to mount the output transformer except on the speaker. Worked out nicely!


One peculiarity with this amp is the tone control. It's the worst I've ever seen. It's a 2 meg pot and a .05 capacitor going across the anodes of the 6V6 tubes. Oh, it worked, very dark, turn the pot then like a switch it's full on. That goofy taper doesn't actually bug me but what does is when you blast the amp you can see sparks inside the pot! I asked the owner if I can wire it somewhere else in the circuit, like a normal tone control. Better to not have an amp flame up. It's fine at moderate volume but who wants that with a little scream box like this????

I can say this amp sounds incredible. Very colorful, very rich and quite loud. More "primitive" than a later Deluxe and has a focused sound with that 10" Jensen speaker. 


One that is worth building if you are into that sort of thing. Experiment with that tone control I say!



Schematic:




Old school construction!!!! :






Original Jensen dated 1946.....




Wednesday, April 3, 2019

1956 Voice of Music8 watt amplifier

This was a fun one. 1956 (or so) Voice of Music 8 watt amplifier. I like that it's just called "8 Watt Amplifier". No fancy school names, nothing clever to shift more units of these babies!



Complaint was it's dead! Lights on but nobody home. That's a good thing. Always easier to fix a dead amp than one with annoying intermittent problems. In this case all those beautiful Mica Mold capacitors were just plain dead. I also replaced the filter caps and added a cap to the 300 ohm cathode resistor on the 6v6 output tubes. This helps low end response while also helping tame some hum away. So it ain't on the schematic. Who cares? Let's improve it!

Super cool slide out chassis:




10" Jensen Alnico 5 speaker! Worth the price of admission.




Some shots of the not 'mil spec' bowl o' spaghetti design:



Mica Mold Capacitors! I'd love to hear a fresh set, never have. They're almost always leaky. One read a whopping 114 vdc on the potentiometer side!



But either way, they sure are pretty. I replaced them with a set of Mojo Dijon for the preamp, and Sprague 225P polyester Orange Drop caps for the phase inverter. An amp like this can benefit from that setup, very clear and warm, but not mushy.



Shot of the filter cap. I upgraded the 470ohm 3 watt resistor with a 500 ohm 5 watt. Also used 2 watters for the 10k power resistors. I like to never see an amp again once it leaves so why not?



Cap dated 47th week of 1956!




Schematic included! I love that. No guesswork if something is burnt.





I love the speaker connectors.




How does it sound? Perfect for what I like. It's not your Neil Young rage box, it's subtle and sweet. Very open and clear sounding. This was never intended for guitar, it's a PA amp. It's the kind of thing I'd use in my living room while someone is playing a big Gibson J45 or  Martin D-18. It gets only slightly louder than one of those at full strum. Perfect accompaniment amp.

Single 5Y3, pair of 6V6 tubes driven by a 12AX7 and a 12AY7. Same tube compliment as a Tweed Deluxe but completely different sound due to a completely different circuit. So if you like something fresh and unusual, seek one out! This is a lovely amp to look at as well as play. And I like nice looking things in my living room. 

-J






1963 Fender Vibroverb. One of the rarest of all.






I had the honor to work on this old Vibroverb last month. At first glance I thought is was a reissue model cause it's so clean. I looked at it again and said "No way!" thinking it must be a kit. Then I realized I know the owner and he has pretty fine stuff.

I've never seen one in person. This goes on my bucket list of rare Fender amps like the 3x10" tweed Bandmaster here.

Amp was blowing fuses. The filter caps were bubbling so I replaced them but unfortunately the problem was the reverb driver transformer was shorted. BUMMER! Nobody makes quite the same part so I just used a new Heyboer with a large washer to hold one end on. No holes needed to be drilled this way and no one is ever going to see it anyway. Easy fix.

The original part goes into a plastic sandwich bag so the owner can decide what to do with it. Paperweight or get it re-wound? He doesn't care since he doesn't use reverb anyway.

Amp sounds amazing. First model to sport those 'brick drop' caps like you see in late 60's models.

Did I mention this amp sounds amazing? I'd go so far as to say aggressive. If cost were no object....



The culprit:





Brick drops!








Original speakers. At some point they were wired backwards! I've seen this many times....




Original milk chocolate footswitch. Mmmmmmm.....