A first build

[shortfuse]

I am looking for feedback on my 1st build choices.  I 1st thought of building a 5E3 but after adding up the cost with a cab and speaker I would not be too far off from a 30, or 50 watt head.  Which is what I really want to build.  So that said I have been looking at the Hoffman 50w design looks pretty straight forward and all the schematics and parts available are right here to build it.   In the folks of the boards opinion would this 50 be a good 1st project?  I was thinking of going the kit route from like Weber, Metro, Tube Amp Dr but I have heard both good and bad about all Kits.  I guess its one of those things your really not sure of until you order one and form your own opinion.  I'm just not sharp enough yet to say this looks right, and this looks wrong, add a ground here and so on.  And it seems like there much more support here, along with better quality parts for some of the components.
I have a pretty good understanding of the diagrams and very good soldering skills, I have just never built one before. 
Please give me your thoughts.

[67polara]

Just get your stuff from here, don't make the mistake I did.  You will get your stuff faster and quality is much better.  Check out the Tweed OD Special I think you will be impressed!!

Tony

[phsyconoodler]

you cannot go wrong with a metroamps kit.They are great.But they are NOT for beginners.You are asking for trouble if you start there.
  Go to www.webervst.com and take a look at his kits.Economical and fairly good quality.
Or for a nice 5E3 kit at a reasonable price go to www.mojotone.com or www.marshamps.com
  Top quality stuff there.
Of for a very pleasing head version of the Marshall 18 watt,go to turret boards.com.

  Of course you can buy top quality parts from Hoffman,but you will still need a chassis and cabinet.

[Fresh_Start]

I do not want to steer anyone away from buying Hoffman parts.  However, having a kit with a detailed layout and instructions of some sort for your first build is a good idea IMHO.  That said, if Doug's "layout" drawings for the Plexi 50 (or another project) make enough sense to you that you can fill in the mechanical details, then go for it!  Also, someone here may have a detailed mechanical layout for you to follow.

Two other kit makers you might research are CeriaTone and Trinity Amps.  CeriaTone offers all kinds of kits.  The only one from Trinity that might work for you is their "TriWatt".

For a 5E3 kit, Mission Amps probably is the place to go INSHO.

Here's an example of the kind of layout that I (still) need:


I just do the layouts myself now.

Oh, and a detailed "bill of materials" keeps me straight.  You can "roll your own" from Doug's documentation, but it's easier to do that after you've built an amp or two.

Hope this helps,

Chip

[Fresh_Start]

Believe it or not, there is a "Kit Amp" sub-forum over on AMPAGE:
http://music-electronics-forum.com/f25/

You may have to register to see it, but you'll get some good poop on pros & cons of different kit suppliers.

BTW Marsh Amplification came up over there.  I haven't bought a kit from him so don't know what his documentation looks like, but you get a Mojo kit (including their nice cabs) at lower prices and with some kind of instructions.  Don't ask about Mojo's pricing policy - it makes no sense to me either, but I can buy Mojo cabs & chassis cheaper from Marsh than I can directly from Mojo.

Chip

[kagliostro]

Nice Layout 

I'm not very experienced

but I think it will be better if you change the way the filament winding "cross" the tubes

keep the two wires the same side instead one in one side and one in the other side of the tubes

Kagliostro

[Fresh_Start]

Nice Layout 

I'm not very experienced

but I think it will be better if you change the way the filament winding "cross" the tubes

keep the two wires the same side instead one in one side and one in the other side of the tubes

Kagliostro

Not my layout!  I agree in general with your comment about the heater wires though.

Chip

[mresistor]

but I think it will be better if you change the way the filament winding "cross" the tubes

keep the two wires the same side instead one in one side and one in the other side of the tubes

Kagliostro

just curious - what is your reasoning for this?

[bluestone]

If you think that this will be your only build, then by all means get a good quality kit. But remember, you get just enough stuff to complete the one project. So if you mess something up, you have to place another order for more stuff.
But, IMHO, building an amp is like any other project, in that you will never get everything you want or need in one trip to the "store". Once you get into this, you will look at a BOM and order more than what is on there. That, to me, is the beauty of the "Library's" list of materials, tips etc. If you need 4- 100k plate resistors for a build, you will buy 5 or 10 until you build up a nice stock of stuff. Remember, you have to have lots and lots of stuff. So not only will you see what you need, but you will start to put together where it is used also. Then you will start with the, “What if I change this resistor or that capacitor”. Well, you need that stuff on hand! So my vote and the way I did it was to research the library and order your first batch of stuff!!! Welcome and happy building!!!

[shortfuse]

Thanks for all the input.  Going to think things over, over the weekend.  I am really leaning towards building something out of the library here.  I have a government surplus supply store with racks and racks of electronic builders type materials 10mi from the house.  So as far as resistors board material and other misc components if i miss order i can always run down there and get what i need.  Problem is every time I go there I come home with more than what I went for.  MORE STUFF LOL
I understand the stuff thing all to well.  I build custom fishing rods, do leather work, and started building guitars so I have lots of stuff for each.  My wife heard me say build amps and went O no more stuff.  He who dies with the most stuff wins correct.  LOL

Really though my main question was do you thing the Hoffman 50w amp in the library is ok for a 1st build?  The color coded schematic's are great but I have no problem reading black & white either.  Someone mentioned it and yes the mechanical layout may be a challenge to make it all fit correctly but i have always found a big part of learning is actually doing.  Anyway I really look forward to this build and the knowledge I am gaining from this site.

Thanks Again

[Tinkerer]

My first piece of advice to you would be to listen to the guys on this forum (besides me ) as they are, each and every one of them, the clueiest people I've come across when it comes to tube amps. Between them, there's somewhere close to a squadzillion years of experience!

My second piece of advice, (should you choose to listen after reading the first piece), is to go with what your heart wants as you won't be happy with anything less, so build your 50W head. My very first build was a Marshall JCM800 (50W) and I don't regret choosing that amp as my first. I made the mistake of sourcing parts from all over the place so it probably would have been cheaper to buy a damn head! Thanks again to the gurus on this forum for helping me sort out the teething problems.

My third piece of advice, and this is coming from somebody living in Australia where the freight is often more expensive than the parts, and I have to import just about everything for tube amps so I've built up quite a stockpile of parts. Buy everything you can from Doug with a few extra (just in case. Somewhere I read that when you buy parts for an amp, always buy enough to build two because it's cheaper than paying postage all over again.) Doug has most of what you will need at the best price for quality, and fast and cheap postage. Whatever you can't get from Doug, source from elsewhere. To add to the list of suppliers that others may not have mentioned there is Nik at www.ceriatone.com for a chassis.

Good luck, keep us posted with your progress, and don't be embarrassed to ask for help.

Tinkerer

[bluestone]

Yes, build your 50 watt head. Buy the pre drilled board and every thing you need here. One step at a time and you will be fine. Read, read and read again the info in the library. My first build was a 5f6a and it turned out fine. Good luck!!! Keep us posted....

[shortfuse]

  I have decided after reading another post on this board last night about kits and followed a few links about kits that I solidified in my head to not go the kit route.  I am going to build the 50w head and try to obtain as much as I can here (design is here so I assume all parts are too).  Seems to me that some of the kit site forums have a few bad apples in them also, and I don't see any of that here so far.  So for the shear fact that the site has great info, quality parts, fast shipping seems to me the decision is easy even if it costs a few more bucks.  I am bad and never get rid of anything I build so like you said build what you want.  I like the post I read last night about the head racks and having to build more before the heads are even done.

Thank You

[mresistor]

for crying out loud - can somebody elaborate on what the heck the previous posters mean about keeping the filament wires on the right or same side....  I look at that layout and it looks fine to me. i'm fully aware of keepin one side of the filament winding going to the same side of each tube socket... is this what they're taling about?  Perhaps they're talking about physical location of filament wires in relation to sockets, chassis.....    what? Or ...did he mean the way the filament leads are crossing over to the tubes?

[Fresh_Start]

for crying out loud - can somebody elaborate on what the heck the previous posters mean about keeping the filament wires on the right or same side....  I look at that layout and it looks fine to me. i'm fully aware of keepin one side of the filament winding going to the same side of each tube socket... is this what they're taling about?  Perhaps they're talking about physical location of filament wires in relation to sockets, chassis.....    what? Or ...did he mean the way the filament leads are crossing over to the tubes?

Just my take, but I like to have the heater wires come straight down to the tube socket staying together as much as possible and flaring out to the solder tabs from the center.  That layout shows heater wires looping around the outside of the socket. 

Does that make any sense?

Chip

[mresistor]

Yes, that makes sense....    thanks for taking time to reply.

[shortfuse]

Ok in the process of ordering parts and I have a few questions already.
On 1/2 watt resistors.  Everything I have read says carbon comps have better tone than metal film but are noisy.  Can anyone please elaborate more or please give me your personal thoughts and why.

Also any feed back on the Marshall style 50w MOP50 & MPT50 for sale here.  Prices seem reasonable for quality transformers.

[echuta13]

Marshall used carbon-films in most of their amps.  A good compromise between carbon & metal (plus more economical).  The carbon-films I use are 1watt rated which is a bonus.

[Fresh_Start]

Do a search for "carbon comp" here or on AMPAGE, AX84, etc.

Go to Aiken Amps Technical Info for an essay.  May be another on on Geofx IRRC.

I recently asked 5 or 6 of the guys here I respect most and got replies ranging from "I always use carbon comps and don't hear any noise" to "Metal films are just plain quieter and I can get more mojo from tweaking values than from noisy carbon comps."  There wasn't a clear consensus, but most heard more hiss with carbon comps and at least half think carbon comps add something special.

IMHO carbon film resistors are the worst of both worlds - more noise than metal film but without the potential to have dynamic resistance change(s) when there are large voltage swings.  YMMV and everyone has an, er, opinion

Good luck!

Chip

[RicharD]

There's been a lot of arguments on carbon comp vs. carbon film, vs. metal film.  Here's my opinion.

I like carbon comp because (mainly) I can read them with my poor eyesight, they're what I grew up with, all my flavorite amps from back in the day used them, + I like thing to be just a little wonky.  

Carbon film resistors should be more stable, and less susceptible noise induced by high voltage.  Metal film are often called "flame proof" resistors and are ideal for power supplies, particularly in higher current, wattage, and thermal conditions.

I built 2 identical bass preamps, one with carbon comp and one with carbon film.  I couldn't hear a difference.  I'm sure there are some people who can hear a difference but I'm not one of them.  The single most critical part of a guitar amplifier is the speaker & it's enclosure.  Tubes and transformers are pretty important too.  Somewhere along the way capacitors get involved although variations in values have a greater impact on tone than variation in manufacturer (excluding ceramics & the cheap crap).  I'd put resistors at the very end of the "critical to my tone" chain.

[shortfuse]

Thanks again for the replies.  I appreciate the comments and opinions.
I have ordered both Carbon Comps and Metal Film (not much more to order both) I see that Doug does not carry Carbon Film on the web site. 
I will check out some of those links.  But I pretty much have everything ordered from here.

I was going to ask the question on the capacitors but read an old thread that some of you were involved in between Mallory's, Orange, Sozo and Jupiter I think.  That conversation went well above my head but was a very interesting read.  What i got out of that one was sounds like personal preference.  Curious if anyone ever was able to test and come up with some good results, but it sounded like to many variables in the testing methods also.

Thanks Again
Steve

[bluestone]

Here's my take:
I use a lot of Mallory 150's. I like them and have never had any problems in getting the tone that "I" like. The Plexi build that I am doing next will likely be with Xicon's just because I have never used them and I want to use something different. That being said, one day each amp may sound a little different to me. Tone is not only VERY subjective, but also dependant upon the listener's state of mind, fatigue and playing mojo for any given time. My rule of thumb is that if you can buy it from Doug, it will be good........

[bnwitt]

Well I love building amps with carbon compostion resistors like buttery and have been doing so for years.  I think it's because of the nostalgia and because of the easy read stripes like butter says.  However, this weekend I had to service a Sears Silvertone 1484 amp from the 60s and the experience made me wonder what I'm doing to folks who will own my amps years from now.  The 1484 was, of course, built with all carbon composition resistors due to the era of it's construction.  Every single plate resistor had drifted up so high the amp wouldn't work.  There were 27kohm resistors reading 140kohm and one was completely open.  Every CC resistor I checked had drifted up in value.  I could have changed them all but I had to stop running up the owners service bill once the amp was working.

I know this Sears amp was 45 years old and in todays society, should one really expect a piece of electronic gear to last that long without some issue?  Well I guess I do.  I want my amps to last as long as the great old amps from yester year and I'm wrestling with the question of whether or not what I had to deal with this weekend is acceptable after 45 years.  It probably is and I'm probably being retentive.  I built and sold my first amp in 1996 and have built and sold a bunch over the years.  I've only had one amp out of all of them with any problem and it was a defective socket.  So, my CC's are holding up so far.  I've still got plenty of them left.  I do use metal oxide and metal film in power supply and other high current areas and I'm thinking the plate resistors might warrant them as well.

[shortfuse]

Ok I have a parts list almost complete but I am struggling between the 2 Hoffman 50 layouts.  I think for the most part I understand them but they are different. I have connected points on the 2034 01/08/96 layout (see attachment) please let me know if it looks correct.  It seems that the designations like "V17" would be valve #1 pin 7 and the numerals 1-12 interconnect.  The Hoffman Plexi50 - layout diagram #1 appears different http://www.el34world.com/Hoffman/images/Plexi50Old.gif.  What are the major differences in the layouts as far as how the amp will sound? Is one a dual volume and one a master volume or are they both master volume amps.  The older layout has a bright switch.  I have purchased the older style Hoffman chassis http://www.el34world.com/projects/oldchassis0.htm and have already purchased a bare board so I can lay it out and populate it either way.  Also on the old style chassis i should not need a ground switch and the .047 cap if I use a 3 prong cord as I plan to use the 3 prong receptacle type. Comments or suggestion please.

[bnwitt]

Shortfuse,
You are looking at two different amplifiers there.  One is the standard Marshall circuit "1987" Plexi amplifier in a Hoffman layout and the other is Doug Hoffman's 50 watt amplifier he made under his own brand.  The Hoffman 50 has a master volume.  The Hoffman Plexi does not.  I would ask Doug in this thread for his description of the variation in tone between the two.

[shortfuse]

Bnwitt that said I wanted to go with the Doug Hoffman 50 (already purchased an original chassis).  I thought that the other (1987) was a newer version of the original as it says Hoffman 50 also (maybe that was just for the board).  Tricky part now is the parts take off, as I think the parts list is for the 1987.  I believe the transformers, choke and tubes are the same looking at both here in the library but the resistors and caps are of different values.  Like I said in the previous post I have already purchased the board Doug suggested so I know it will all fit and then some.  The board I purchased is a Garolite Sheet, 1/8 X 12 X 12 epoxy (a lot more HD than what I have seen in amps probably because it holds the tube sockets also) so it will have to be cut down anyway.  He also has just recently added the old style board template after I inquired about the build http://www.el34world.com/Hoffman/images/2034Template.gif which will help me out immensely.  I may have to do a bit more studying before ordering the parts.  Not quite sure on the all the resistor wattage's.  This is truly going to be a learning experience all the way around but I am really looking forward to it. 

[Fresh_Start]

Most resistors can be 1/2 watt.  Look at Schematic Heaven for original Marshall specs:
http://www.schematicheaven.com/marshallamps/jmp_lead_50w_1987.pdf

The Ceriatone 50watt layout shows some resistor specs too, and adds screen grid resistors and power tube grid stoppers (both good ideas IMHO and in Hoffman's drawing too).

General rule is that any resistor in the power rail (B+ line) must be AT LEAST 1 watt.  Dissipation = (Voltage ^2) / Resistance.  Sometimes plate resistors for the triodes in a long-tailed PI are spec'd at 1 watt.  Power tube grid stoppers and screen grid resistors are always bigger than 1/2 watt.  The bias "range resistor" should be at least 1 watt and maybe 3 watts depending on the particular amp.  The closer you get to the PT, the more likely you need a higher rated resistor.  When in doubt, go higher.  Best of all, copy a known design.

Whaddayaknow - Doug's "Common Hookup Info" tells us that blue resistors are higher values (IOW more than 1/2 watt):
http://www.el34world.com/charts/CommonHookups.htm

Hope this helps,

Chip

[shortfuse]

Thanks for the info Chip
I do try to read the library and archives before I post and I did read Doug's info pages I think I have been to and read most information pages on this site over the last 6 months or so.  Sometimes I know I read it but can remember where LOL.  Anyway the color coded one works fine for layout http://www.el34world.com/Hoffman/images/Plexi50Old.gif and board http://www.el34world.com/Hoffman/images/Plexi50New.gif but I am dealing with http://www.el34world.com/Hoffman/images/2034skem.gif , http://www.el34world.com/Hoffman/images/2034Template.gif  and http://www.el34world.com/Hoffman/images/2034wire.gif.  But I will take your info and what I have read and try to throw up another color coded sketch with the resistor ratings of what i have interpreted in my reading and see if you guys can tell me if it will work.  I don't mind doing the  homework and getting graded on it even if it is an "F" but would like reassurance before I proceed.  You guys on this forum are great.



Steve