New 5E3

[Big Jim]

Just finished this build. I've been pondering a Tweed for a while, so I finally got the urge and put this together. I got the Iron from AES. The PT is 300-0-300. The OT is a Hammond. Everything is running pretty cool (sittin on my bench). B+ is a little high @ 380. The coupling caps I got from John Gaynor @ Sozo.(Nice guy). My line voltage was about 124V when I measured the B+. So...hopefully I can get that down a tad, and then proceed to get this thing broken in. Honestly the amp sounds pretty damn good right now. Way more harmonic feedback than I expected. Now, on to a speaker & cab.
Jim

[Colossal]

Really nice build Jim; very clean. The Sozo blue molded caps do sound good.

[surfsup]

Beautiful!

[ampmike]

Awsome Jim!!!!!!!Really nice,You gave me a shot nice of the 4 input jacks,As usual Im having a problem Thanks Mikey

[Structo]

Looks good.
I like all the blue!

Might want to double check the heater voltage if the other is running high.

On the right jack in the picture the 1M resistor looks like it may be in the way of a plug when plugged in.
I say this because carbon comp resistors can break easily.

Also the use of wire nuts inside amps is kind of a no, no.

[Cliff Schecht]

I love building these old designs with carbon comps. The added noise is worth the auditory benefits for sure. Very clean build you have there.

There are different solutions for tackling high wall voltage. Some people just carry a variac wherever they go and others use 12.6V transformers to buck down the wall voltage. I don't really bother with either of those anymore. I just worry about the heater voltage, if this is too high then I put in enough resistance to drop the heaters into spec. But I usually underrate these resistors a bit to account for the more normal 120V situations, this way the heaters stay in spec no matter what wall voltage you get (heaters are +/-10% anyways). I also like to use two equal valued resistors on both sides of the heater as opposed to one larger resistor. You not only maintain the heater balance (better hum cancellation) but this allows you to use smaller wattage resistors.

I think the 380V is about right for the 300-0-300V power transformer and is about on par with what the original 5E3 was at IIRC. My 5C3 clone runs at about 400V with the 330-0-330V transformer in there so I don't think you are sitting at an unreasonable number. The original 5E3 transformer was spec'ed at 350-0-350V and put the B+ well over the 400V mark. Personally I prefer the lower plate voltage for extended tube life. I also like to adjust the bias so that at the voltages YOU have the tubes sit at the plate dissipation of a real tweed deluxe (which is an integral part of the sound, these were biased at like 80% PD I think..).

[Big Jim]

Thanks guys! first off, I posted the PT as 300-0-300. It is actually 330-0-330. Duh! :oops Tom, I checked that input resistor and it is close, but it clears. I knew I was going to hear about that wire nut. The Weber layout shows it done that way, but I'll do something a little more kosher before I button her up. The amp sounds really good like it is. I made a virtual center tap off of the pilot light, as the trannie had no CT for the heaters. As a result, the amp is overall rather quiet. I do have a little floor noise when you increase the opposite channel volume. Any Ideas on that? The 6V6's I have in here are mismatched a good bit it seems. I will pick up a pair soon. Cliff, after reading your response, I think I'll just sit tight for a while and let this thing settle in a bit. I have a NOS 5751 in V1 and a JJ gold pin in the PI. Any tweaking tips or experiences with this circuit?
Thanks again,
Jim

[Cliff Schecht]

Makes sense, I kept running the math trying to figure out why your B+ was about where mine was with lesser secondary voltage. As long as your heaters are under 7V you'll be best off playing the amp for a while before doing any tweaking.

I'm no expert on the 5E3 circuit really, but the 5C3 I built is essentially dead stock and I love the sound. It's pretty similar in sound to the 5E3 but has the characteristic octal preamp sound. I had to use the "anti-fizz" Zener trick in my amp but I don't know if the 5E3 suffers from this problem. If it does the fix is about $0.10 worth of diodes and maybe takes 5 minutes to do. Maybe others can chime in here. If it is a problem then you will at least know how to tackle it.

[tubeswell]

+1 on zenering down the B+. All you need is 1 (or more) 9V-15V axial 5W zener(s) in series between the High Tension winding's centre tap and the ground (banded ends/cathodes pointing to ground), mounted on a tag terminal strip away from the inside of chassis. This is more than ample for a 5E3 and you get to muck around with various combinations of zener voltages to get the B+ where you want it. I have done this a number of times with great success in reducing B+. Better yet, put a shorting switch in parallel with these zeners for when you want to ramp-up the B+. For a 5E3, it sounds ideal if you can get the Plates to around 350, with a 220-250R shared cathode resistor, bypassed by a 25uF cap. (So in your case I would go for 2 x 12V 5W or 2 x 15V 5W zeners in series)

But if you are going to use a chunky 20Wish bolt-on type zener instead, then you are more limited in what you can get in the way of voltage reduction (and in addition, the zener in that case needs to be rated more highly, ironically, because it has to deal with the heat it picks up from the chassis).

[Big Jim]

Tubewell,
Thanks for the tips. I bought some NOS Raytheon 6V6GT today. Getting around 350 on the plates. the amp is sounding real good. Off to work for the weekend. I'll crank 'er up Mon.
Jim

[Big Jim]

P.S. Tubeswell,
Your commentary on this circuit has made for some good "pre build" reading. You are certainly well aquainted with this type of build. Thanks
JIm

[M Fowler]

BigJim very nice build does it take time to burn those blue molds in?

Mark

[Big Jim]

BigJim very nice build does it take time to burn those blue molds in?

Mark

My first build w/them. Supposed to be really close to the old Astrons. Thanks for the compliment Mark.
Jim

[Colossal]

Mark,

In my experience, after startup they start sounding noticeably better after about 10-20 hours and continue to improve until about 80-100 hours or so. I used them in that jazz amp we talked about and they sounded really good.

Dave

[Big Jim]

Mark,

In my experience, after startup they start sounding noticeably better after about 10-20 hours and continue to improve until about 80-100 hours or so. I used them in that jazz amp we talked about and they sounded really good.

Dave

Good to know there are better things to come!