5E3 inspired build

[WRC34]

Hi everyone,

Just wanted to share the latest creation I've made. The people here helped me a ton with a couple other builds recently, from which I learned much and am grateful. Proud to say this post isn't looking to help solve a problem! Just sharing results of a build

This amp I wanted to be 5E3-esque but it is not a clone in any way. It uses all octal tubes - 6SJ7GT input, 6SL7 gain stage/split load phase inverter, PP 6V6 output section and (in these photos at least) a 5AR4 rectifier. It also has a 6H/65ma/235ohm filter choke, a single input jack, volume & tone controls and 8 & 16 ohm speaker out jacks. The power transformer is an old unknown brand which has a 285-0-285 HV secondary rated at 120ma, 6.3V CT and 5V windings for filaments and rectifier respectively The OT is an Allied/Knight brand with a 6.6K primary and a multi-tapped secondary. It is over-rated at 35 watts which, coupled with the use of the 5AR4 rectifier tube, helps the amp bark strongly without becoming too mushy.

The sound is really big, strong & clear. It sounded best with my '52 RI Tele which is loaded w/Seymour Duncan Antiquity pickups, although with an SG and ES-175 it sounded good as well. I may be wrong but to me the type of phase inverter really affects the sound in this amp in a good way. I can't wait to play this alongside the 18 watt 6GK6 amp I built, cranked up and running simultaneously together!

approximate DC voltage readings, from what I remember, were something like this:
6SJ7 plate - 147
6SJ7 screen - 30 (too big a gap? Maybe, but it sounds great!)
6SL7 plates - 220
6V6 plates/B+ - 385
6V6 screens - 340

Haven't tried it w/5V4 or 5Y3 rectifier tubes yet, but am looking forward to what how they change the sound.

[martin manning]

Cake pan chassis? Looks great. The PT looks to be Northlake from the 1005 EIA code, possibly 1958.

[WRC34]

The PT looks to be Northlake from the 1005 EIA code, possibly 1958.

Wow, good eye! Thanks for helping me identify the PT. And yep, cake pan chassis.

Some more info about the amp - the filter cap values are 22/22/16, cathode resistor & bypass cap on power tubes is 250 ohm/100uf, coupling caps were changed from traditional 5E3 values to .047uf (they're the large white Cornell Dubilier Miniroc caps in the gut shot). I got the 6SJ7 component values from one of the 'Octal Fatness' schematics floating around out there, although they're not all exact (plate resistor is 180K as opposed to the 220K seen on most schematics, screen resistor is 1.3M, cathode bypass cap is 10uf). Additionally, and I may have misunderstood this - if so please speak up, anyone! - I read that the total resistance on the input or grid of the 6SJ7 shouldn't exceed 1M, so instead of the traditional 1M resistor to ground on the input jack I used an 830K resistor which was pulled from an old transformer-less Admiral 'All American Five' style radio, and it's followed by a 33K grid stopper for a total of 863K which fits pretty neatly under the 1M limitation, if such a thing exists.

Martin, I tried to find where you saw a code on the PT and then realized, dur, you read it off of what is actually the OT. Does it make sense that they manufactured transformers to be sold under the Allied name?

(and that's a 'dur' on my part, not yours!!)

[martin manning]

Well, yes I guess that black transformer is on the preamp end of the chassis, and yes I could believe Northlake manufactured transformers for Allied. The PT probably has an EIA code on it somewhere, so you can probably find out who made it.

[WRC34]

The only marking on the PT is "5A 6146"

[WRC34]

Here's a demo I just made of this amp alongside an 18 watt Lite iiB style amp.

https://www.youtube.com/watch?v=7eRJqbU ... e=youtu.be

This one was made 'in the garage' for thematic congruency with the board here and also to try and get less camera speaker/mic breakup I wish it was a little longer. Maybe I will do another, more in depth demo of this amp alone.

[Structo]

Wow, I liked the octal amp for both clean and dirty.
It had a nice grind.

I have noticed that when I play at home, my tone settings are darker than in a gig setting or larger room.

If you have ever heard one of those isolated track recordings where you can hear individual tracks, the guitar almost always doesn't sound that great because it is usually pretty bright to cut through the mix.
But when combined with the bass and drums, sounds awesome.

So an amp that can be dialed in for both practice and live gigs is a bonus!:D

[WRC34]

Wow, I liked the octal amp for both clean and dirty.
It had a nice grind.

I have noticed that when I play at home, my tone settings are darker than in a gig setting or larger room.

If you have ever heard one of those isolated track recordings where you can hear individual tracks, the guitar almost always doesn't sound that great because it is usually pretty bright to cut through the mix.
But when combined with the bass and drums, sounds awesome.

So an amp that can be dialed in for both practice and live gigs is a bonus!:D

Thanks Structo!

What you say is so true. It is easy to forget that a guitar is but one part of an entire band. Having worked for a touring band for many years I have seen firsthand the guys using top-notch, pro level gear that's in great shape with close attention paid to freshness of tubes and bias have their amps sound and behave drastically different from day to day. Every room sounds different, the humidity and barometric pressure make a difference, EVERYTHING affects tone much more than you'd think.

But then again...maybe that's why we find the stuff so darned interesting

[strelok]

That is quite a fat sounding amp. I love the low-mid gnarl that it has, makes me want to build an all octal amp now. Oooh an all octal 4-4-0. Great now I have another project floating around in my head that I don't have money for. Hope you're happy.

[WRC34]

Thanks strelok!

I may be wandering a little too far out of Fender territory here since I'm pretty sure these guys are using Marshalls here, but in regards to Structo's addressing the differences in tone when playing on your own vs. playing live IMHO this video is a great example of what seems like a super mid-rangey, over treble guitar tone that actually sits perfectly in the mix once the entire band starts playing.

https://www.youtube.com/watch?v=O8Ii2jcd30A

[Structo]

Love the look of the Coke bottle valves.

I may have to build an all octal amp.

[WRC34]

Finally got some voltage readings from this amp. These are all "standing voltages" with the amp powered on and no signal applied/guitar plugged in. All voltages are DC

with 5Y3 rectifier
6V6
plates - 322 VDC
screens - 294 VDC
6SL7
plate 1/2 - 156.8/190
6SJ7
plate - 128.8
screen - 23.3

with 5V4G rectifier
6V6
plate - 348
screen - 319
6SL7
plate 1/2 - 170/206
6SJ7
plate - 140
screen - 25.37

with 5AR4 rectifier
6V6
plate - 360
screen - 331
6SL7
plate 1/2 - 176/214
6SJ7
plate - 146.7
screen - 26.7

Hope to get a chance to draw up a layout of this amp soon as well.

*edited for spelling errors