Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Platefire on October 07, 2010, 10:23:25 pm
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I fired this thing up yesterday and everthing seems to be purking OK. This is original 5E3 circuit with the exception of only one input per channel and a standby switch. I haven't applied any lettering/text lables to it yet. I can see now what the big deal is about this circuit--great tone and response and the tone stack function is creapy but fun.
The hard part of this amp is the way this Hammond chassis/Cage/Bottom Plate is set up required me to build and mount the board upside down and backwards from normal perception. This kind of blowed my mind and got me confused serveral times but by taking my time and double/triple checking everything, worked the first time.
The voltages seem to running amazingly close to vintage 5E3 voltages being testing with a RCA and a Sovtek 5Y3 with both tubes providing almost identical voltage as follows:
1-To OT=365
2-6V6 Plates=359
3-6V6 Screens=331
4-12AX7 PI Plate=203
5-12AX7 Pre PI Preamp Plate=170
6-12AY7 Plates=122
I'm a little disapponted that the "5E3" Logo didn't turn out sharper but painting a perferated cover its almost impossible to get a sharp edge. So it stays regardless. Platefire
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Mow pixs
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Cool & clean, man! Nice! I like the cage color and the end handles. I also note, those hooks on the back can be used to hang up a V-neck sweater before jammin', which is always a big plus. Good job!
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Thanks!
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Very nicely done! I'd be proud to own a build that looked like that.
with respect, Tubenit
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That looks sweet inside & out! I love the handles and the sweater, er power cord, hooks.
Do you have the 2 channels permanently jumpered?
Looks like 2 tone controls & one volume, or am I missing something? Doah!
Hammond transformers?
Congratulations!
Chip
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Thanks! Building this kind of head cab gets me out of building wood cab and tolex which is a detailed operation within itself. I prefer the painting. I just didn't realize the board re-arrangment required for this setup until I got into it.
Yep! Those are Hammond Transformers
The power cord hooks--I've got a Bogen CHB-50 and a Dukane conversions PA heads and neither have any kind of accomadation for the power cord which is very inconveniant when transporting. So I was determined to put something on this to take care of that. I do think the handles and hooks would may have been better in black.
The controls are wired exactly like the original 5E3. I just re-arranged the inputs and controls that seemed more logical to me. When I lable it, it will make more sense. It's re-arranged is as follows:
Normal Channel #1=input jack and volume control
Tone control=in middle between both channels
Bright Channel #2=Input jack and volume control
I know that the tone control is not a master tone control and mostly intended to effect the bright channel but it does effect both channels to a certain degree especially when your in channel one and mess with the tone control and volume control of channel two. Kind of freaky and cool all at the same time the way it works.
I haven't tested it with my group yet, but inital home testing is very impressive. Platefire
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Very clean looking build :grin: I bet you'd have to hand paint the 5E3 to get it pin sharp (was it sprayed?)...or perhaps mount a black rectangle behind it inside the cage to help it stand out.
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Very nice job Plate! That looks incredible! :shocked:
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The 5E3 was sprayed through a template not much larger that the 5E3 text. I had to use map pins through the preferations stuck through the template from the inside of cage to pull the template up flush with the cage to cut down on overspray. All the cage around the template inside and out was covered with brown wrapping paper to mask it from the spray. Platefire
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Nice!
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Very cool ! :hello2: :hello2:
How does it sound ?
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Now that is a nice amp! I am very surprised with your statement that you are getting the same voltages with a nos and a Sovtek 5Y3. I find that the Sovtek will generally run as much as 30 volts higher that a nos tube.
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I love it!
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Excellent workmanship!
I just about finished a 5E3 myself (with bigger iron and El34's). The volume and tone control interaction is bizarre, but versatile. The customer wanted front mounted controls and tweed, so I had to go with a slant face universal chassis from Dave Allen.
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Good show Plate, nice work.
Punky
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Hay Thanks. Just finished the lettering. It's pretty much completed now. Plate
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Great build. It's much nicer working in head chassis than the original "wedge" chassis the 5e3 usually come with. Love the layout and cosmetics.
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Very nice and clean job. How did you do the lettering?
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Hay cups
That original 5E3 chassis arrangment always looks pretty tight room wise to me. This amp certainly gets away from traditional layout but I was mostly wanting to provide that original circuit and sound with my own logic in layout. This chassis more or less dictated layout requirments. With the exception of the inputs and stanby switch, you can trace every circuit connection and will find it's all original 5E3.
Shortfuse---the lettering is just your common ol Wal Mart DYMO LetraTag electronic lable maker with clear tape. I considered a lot of options available for text/labeling but finally decided on this. Kind of like the old saying "Poor Boys have Poor Boy ways".
I played the amp at Church today with our Church Praise Group and the tone was good but it has more clean headroom than I expected and no breakup at about 8:00 Oclock on the volume. During the night service I turned it up to about 9:00 Oclock and then started getting some of the famous 5E3 heavy compression on the edge of breakup. Don't think I got quite to the sweet spot but was getting close! Platefire
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Man, this build is VERY nice and clean. I'll bet it's as quiet as a church mouse :wink: ?
Did you try another set of 6V6? I know for sure that the JJs are very strong tubes and give you more apparent power than other 6V6. I won't change them in my BF Deluxe replica!
I use EH or Tung Sol RI on some builds (they are similar, maybe from the same factory); they give more crunch at a lower volume. I love TS in my 5E3 and tweed Princeton.
Best regards,
Danskman
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Danksman
Pretty quite. It does have a little bit operation noise as you turn the volume up but not above what I would say normal. I was playing a tele which tends to be more noisey than my other guitars. With a humbucker I'm sure it would be totally quiet.
Yeah I'm sure the JJ's is giving it a extra clean headroom boost that I wouldn't get with more vintage tubes. I haven't tried any other 6V6's in it yet.
I've got a Revere reel to reel conversion what I call the 5DC3 Deluxe which has both those circuits combined to a certain degree. I've got RCA 6V6's in that. It's sound and response reminds me a lot of this 5E3. Platefire
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That is so sexy! Especially with it's top off.
I say this because my main amp you guys helped me build has the same handles, and look; tubes hanging out, and big trannies on top. Just love it. I'd like to get a top cage made but don't even know where to start looking. But that's a real fine job, man.
Mega
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Thanks---but I do like the cage. I've always been nuts about those old PA heads with a cage. I finally took pixs with the cage on after I did the lettering. Regardless if I make a thousand or this is the only one, it does have a serial number. Plate
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I've got a potential customer interested in this amp with changes. He's wanting a power cut switch.
I've never done that before and was looking in the Hoffman Info but couldn't find anything particurally regarding that. Can someone point me in the right direction. Plate
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Here's one of da geezer's ideas. Cheap and easy and works pretty good too. And there's always VVR.
(http://home.comcast.net/~seluckey/da_geezer.gif)
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Hey sluckey - thanks for that pretty drawing! I remember the discussion when daGeezer came up with this idea but don't remember that really nice drawing.
Platefire - Bruce Collins from Mission Amps also has a post phase inverter master volume which seems fairly well accepted for the 5E3 circuit IF you must have a master volume at all. Personally, I'd try daGeezer's cathode switch first, but here's the PPIMV just in case (attached). With a cathode bias amp, you don't need the second pair of coupling caps between the MV pots and the 220K grid return resistors IIRC.
That is so sexy! Especially with it's top off.
I say this because my main amp you guys helped me build has the same handles, and look; tubes hanging out, and big trannies on top. Just love it. I'd like to get a top cage made but don't even know where to start looking. But that's a real fine job, man.
Mega
Hammond sells steel cages specifically made for its amp chassis. You can find them on Mouser among other places.
Cheers,
Chip
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Platefire - Bruce Collins from Mission Amps also has a post phase inverter master volume which seems fairly well accepted for the 5E3 circuit IF you must have a master volume at all.
You don't need a PPIMV in a cathodyne/cathode biased-amp. You may either use a crossline (1 MA w/switch between the two phases) or a bootstrapped PI MV (250 KA or so replacing the 1M resistor in the cathodyne).
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That turned out real nice Platefire. Got to love all those low wattage amps
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Ok! Thanks Very Much. So on Da geezer circuit---if I'm understanding it right, the 5E3 power tube cathode resistor=250 Ohm 2X=two 500 Ohm resistors? Then all the other resistor values on the switch would be as is. So on a new amp, you would just make provisions for these additional cathode resistors & caps on your board and could stick the switch right on your front panel.
Regarding Mission Amps MV, never thought of a MV being a power switch but I guess it has the same effect.
Thanks, Platefire
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if I'm understanding it right
You got it. I never built this circuit. Send Geezer a pm and he can fill in any details plus give you opinions about that circuit.
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Ok Thanks! I'll check with Da geezer on the switch. I did notice on Mission's PPIMV that is a different kind of PI shown than on the 5E3---so that might be a problem getting the same results?? Plate
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That MV shown above is for a fixed bias amp, not a cathode biased amp like your 5E3. A version of that MV for your amp would be much simpler.
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Sorry for over-complicating a possible PPIMV for this circuit. Here's a much better example of a PPIMV for a cathode biased amp (from more of daGeezer's work together with tubenit):
http://www.el34world.com/Forum/index.php?action=dlattach;topic=9636.0;attach=15949
Ok Thanks! I'll check with Da geezer on the switch. I did notice on Mission's PPIMV that is a different kind of PI shown than on the 5E3---so that might be a problem getting the same results?? Plate
I don't see why the type of PI is important in terms of how this general form of PPIMV functions but FYL may be right about a crossline functioning as well. I put a crossline PPIMV in a Princeton Reverb (same PI as 5E3) and didn't like it at all - by the time I could hear a meaningful difference in volume there seemed to be a real loss of tone. However, bnwitt & others used it in the PR circuit and seemed to like it.
The key point about the 5E3 AFAIK is that power tube distortion is a big part of its distinctive sound. A search over on AMPAGE turned up a bunch of posts which basically said "don't go with a PPIMV in this circuit".
Go with daGeezer instead!
Cheers,
Chip
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Thanks! I ran both option by the customer and he liked the switch with three levels of power. So thanks for helping me let him know. I will get with geezer on the details before I proceed on anything. Plate
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Hey Platefire - please make sure to let us know how that switch turns out with the 5E3 circuit.
Thanks,
Chip
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Chip
On the 5E3 switch, when I talked price with the guy, he went away!! :cry: Thats Bad!!!
But----My Son Greg, a lot greater guitar player than I, tried out the 5E3 and loves it. He's been using one of Gabrials Sound Garage Voxiers for several years now. He said he thinks this one sounds better. He also loves the metal cage cab but don't like my cheap dymo text. He now wanting to re-create the text/fonts amd painted finish to be a lot more cosmeticly pleasing. So I'm glad to have him exited about it and wanting to work with me on it. So it looks like more new improved TE-Deluxes to come!!! :laugh: That's Good!!!!
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:smiley:
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Hey Guys, On Da Geezer`s Bypass Cap attenuater(above), is there any reason the DPDT switch and four resisters can`t be replaced with a 1/2 watt dual gang 100k linear pot for variable control? Thanks Punky
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It wants to be a zero to about 1K pot. NOT 100K... that would be useless over 99% of its range.
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Thanks PRR, that makes sence. I dont really need the 1/8-1/4 power setting. Between full and half is plenty. The amp I want to try this on has two 7591 power tubes with one 10 watt cathode resister and cap. Can I get away with using a single gang pot? Will I need to increase the wattage of the pot? Thanks, Punky