Vintage Kent DR45 Tube Amp - Lotsa Cool on the Cheap! | Warehouse Guitar Speakers

Vintage Kent DR45 Tube Amp - Lotsa Cool on the Cheap!

Vintage Kent DR45 Tube Amp - Lotsa Cool on the Cheap!

Vintage Kent DR45 Tube Guitar Amp Amplifier Fiends, I can't say that I've EVER ran across an amp that has me scratching my head more than this Kent DR45.  
Most of us above the age of about 40 or so at least recognize the KENT name, as quite a few Kent branded electric guitars were sold during the 1960's and early 1970's.  However, the amps are quite a bit more rare, and this model is nearly rare enough to be termed a "Ghost Amp".  She's a cool ghost, too!  With a pair of 12ax7 tubes in the pre-amp section and a pair of EL84/6BQ5's for the power section, complete with tube rectification and tube bias-oscillation tremolo ... well ... it's got all the right stuff!  I came across this amp while negotiating a deal on a Silvertone archtop; the seller got a gleam in his eye and led me to a back room and said he had something he knew I'd love.  He was right.  It was this amp and a  matching Kent Polaris II guitar, he made me an offer I couldn't refuse and away I went.  I was told in advance that the amp did not work, and several days later I opened her up to see what ailed her.  I was pleasantly surprised to find a very clean pseudo turret-board layout that looked very repair-man friendly.  The filter caps all checked dead as a dornail, and so I replaced them with slightly over-value Sprague Atoms, checked all the other components and fired her up ... NOTHING!  Hummm, other than a bunch of carbon resistors that had drifted out of spec, everything was  perfect.  Hummm.  And so I did what we all do in these situations, I googled the amp for a schematic, that's when I realized how rare this amp was.    What did I find?  Very near to NOTHING!  I found one that had sold at auction years earlier and one repair shop that had one in and had tried to produce a simplified schematic on the amp (most of which wasn't right).  Those TWO references were it!  There was a little scrap of a postage-stamp sized schematic left attached to the bottom of the cabinet that gave me about the first 25% of the circuit, and with that and the amp in front of me, I finished off the schematic.  I'll post it here for anyone else who runs into this rare gal!  What was wrong?  Well, in a nutshell, it had to do with the fact that VINTAGE EL84/6BQ5 tubes had pins one and two internally jumpered and "NEW" EL84/6BQ5's do NOT.  My next blog will focus on this!  For now, let's talk about this amp!

Vintage Kent DR45 Tube Guitar Amp

Here is that nicely laid-out chassis.  This is after I had replaced all out of spec resistors and the filter caps.  I actually found this easier to work on than a vintage Fender!

Kent DR-45 Chassis

Okay, now would be a good time to talk a little about the BIGGEST mystery concerning this amp: 

who made it?  "Kent" was a name/brand only, just like Silvertone or Airline, they never actually manufactured anything.  There is a fair bit of info available on Kent guitars.  It is widely agreed that the Japanese manufacturer Guyatone (aka Tokyo Sound Co.) made the vast majority of Kent guitars;  Kawai, Fujigen Gakki, Teisco, Matsumoku, and even Hagstrom also made guitars that wore the "Kent" name-plate.  But what about the Kent branded AMPS?  Well, ummm, I just can't really say much!  I sincerely hope there will be some folks who read this blog and can post some info ... seriously!  All I could find is that Guyatone ALSO made Kent amplifiers.  But take a look at this panel-shot  "MADE IN USA"!  Hummm ... made by WHO in the USA?   The chassis kinda-sorta looks like a Valco, or maybe Danelectro build ... but not quite.  Power & output transformers are US made as are the pots and caps, so it's safe to say it probably really was made in the USA.  Again the question: by who?

Kent DR45 vintage tube amp with tremolo

Okay, where the rubber meets the road: how does she SOUND? 

The short answer: pretty cool.  But hey you are TONE-SEEKERS ... you want the loooong answer, right?  Well, when you think a pair of EL84's and a pair of 12ax7's on a tube rectified amp with tremolo it's hard NOT to think of the 18-watt Marshall ... this ain't that.  The trem is VERY Marshall like ... but from there it gets wierd.  You see, even though it was way outta vogue by 1965 (the date on the schematic), this amp features a grid-leak bias on V1, what that means is that the input stage is fairly wimpy and quite ratty when over-driven.  Another key difference is that the Kent runs a very conservative 260-volt B+, whereas the Marshall runs a healthy 340-volts, this means the Marshall has a lot more volume and especially clean headroom.  I will make a side-not here:  I did substitute an actual 18-watt Marshall power tranny while I had her on the bench and, yes ... she DID sound a lot better.  At some point I might consider making that transformer a permanent replacement in this amp and, along with changing V1 to the more modern/conventional cathode bias, well then ... shoot ... it WILL be almost exactly an 18-watt Marshall!  Why didn't I just go ahead and do that?  Well, because this amp actually DOES have it's own distinctly cool retro garage rock sound.  When played through my shop speaker (a WGS ET90) it actually sounds downright addictive!

That brings us to this:  What mods WILL I do to the amp?
Y'all know me!  I GOTTA make some changes :-)  And here they are.  First, you will notice that there are THREE(!!) inputs, ant they are all exactly the same.  They are voiced exactly alike.  What?  Now, with the grid-leak bias on V1, there is a cap that couples the input to that first tube stage ... and it's VERY important ... shoot, it voices the entire amp!  (Note: see schematic below)  The factory value of .05uf was fine with single-coils and with the volume kept low and it probably worked just perfect with the low output pickups of the Kent Polaris guitar, and during a time when folks tended to not push an amp into distortion, but ... with modern humbuckers and the volume dimed, it was pure elephant farts!  I found that the MUCH lower value of .005 was excellent when fully cranked, and the mid-way value of .01 was optimum for slightly over-driven settings.  So, my first thought was "I'll wire each input jack with each of the three values".  But, plugging in and unplugging to change tone wouldn't be very convenient on-stage.  So, I plan to use one of the three input holes to mount a three-way switch and I'll lable the three positions "FAT", "TIGHT", and "Bright".  How cool will that be?  and ... it'll still leave me two freeking input jacks!

Vintage Kent DR54 Tube Amp schematic

And one last thing:
You guessed it ... THE SPEAKER!  Gang, this one is going to blow your minds!!!  Now this cabinet looks like it probably houses a 12", or maybe 15" speaker, but NO ... it has a single 8" speaker!  Not Kidding!!  I've always lamented the fact that manufacturers skimp on what matters the MOST (Speakers in amps and Pickups in guitars) ... but never have I seen the situation taken to this extreme.  This poor little 8" was good for about 10-watts absolute max, and even with the low B+ voltage, this Kent was capable of an easy 14-watts (more when driven), plus, it just sounds tiny!  What on earth were they thinking?  So an upgrade is obvious, but what?  Ya all help me out here!  I'm thinking I might go with a G10C and a G8C ... or maybe THREE G8C's (yep, they'll fit) ... or maybe a single 12 like the G12Q ... or maybe even a G15A.  Tough decision!

Kent DR54 Speaker

Next Week:
I'll explain in detail that little pin 1/2 issue with EL84 amps.  Folks, if you run an amp with a pair of EL84/6BQ5's ... you will want to know this!
See ya then!

Kent DR45
01/20/2019 6:48pm

Wow, this trip is getting interesting. My brother had one of these amps a few years ago. I liked the tremolo and it sounded warm, but didn’t sound great dirty. He promised to sell me the amp but turned around and gave it to a guy he had just met at work, along with the Strat copy he had with it. Pissed me off! Just a few months ago I found a Knox Amp just like this one for sale locally, but didn’t have the money. I told my buddy about it and he bought it p, with the intent on modding it and selling it to me once he had learned all he could from it. Today I saw a Kent amp for sale, and it looks exactly like the Knox amp. Identical in every way, except the Knox has a12” speaker. The schematic is the same, and after reading your article, particularly the bit about using an ET 90 in your shop tells us right where we want to go with it. I may go with an ET 65, but have an ET90 in one of my other amps and love that speaker! Thanks for posting this and good luck with yours!

05/11/2019 1:53pm

I purchased a Gregory Apollo Model 800 from I have not received the amp yet, but it appears to be a stable mate of the Kent. Thanks for the tips on tone tweaking.

I am drawing blanks about who made these things, but knowing that Kent and Knox are related should help. I hope that when I get the amp I can recognize something that will lead to a manufacturer. The handle looks the same as my New Jersey-made Sano. But, the super-clean wire dressing on my Sano is nothing like what I see on Gregorys.

A link to the Gregory is here:

Note the panel layout and knobs. The tube complement is the same, but the schematic is not the same as the Kent amp presented here.

05/28/2020 6:19am

I have the Decca DMI 61 that has the controls on top but in the rear like a Tweed Bassman that looks identical
to yours even the schematic looks the same and is has a stock 1x12.Sounds pretty good with the 12.The output transformer was replaced at some point with a TRIAD output transformer and it has additional taps for 4,8,16OHMS(BONUS!),so I will add a impedance switch and jack just because its there and eventually a better Alnico speaker.
I also own a Kent DR 46 2x12 Bass amp.Very similar construction.Sounds pretty good cranked with a guitar.

Thomas Hoglund
06/29/2020 5:13pm

Had one of these that I used when I first started a band in 1968. You're correct about the speaker being completely under powered for the amp. It didn't take me long at all to blow the speaker on it. Probably playing something like The Year 2525 by Zager and Evans.

Being only 13 years old, I didn't know how to replace a speaker or where to even get one in a town of 3,000 people in northern Wisconsin. So I bought a new solid state amp. Didn't like the sound of it, so I cut down the Kent amp to be just a head, wired a 1/4 plug to the speaker wire and used it as a preamp to the solid state. Gain stages were completely mismatched, but it gave me a great distortion sound.

Just found one of these on eBay, hopefully will be in working shape when I get it. Otherwise will need to tinker. Will definitely want to replace the speaker so I don't blow it again. What did you end up putting in this and how does it sound?

I also bought a vintage 1968 Teisco guitar just like what I was playing in 1968 and have re-fretted it and fixed the electronics. I can sure play it a lot better than I could at 12. Probably had the setup all wrong back then.

06/30/2020 2:14pm

Hey, I ended up making a baffle for 2 8's and went with a G8C pair ... and it's AWESOME! Highly recommended!

Thomas Hoglund
07/18/2020 11:36pm

Do you remember if you had to do the pin 1/2 thing on the EZ81 too? Bought one and get no sound using it.


07/19/2020 2:49pm

The EZ81 definitely must stay wired as-is !