18W build

[Robbiez]

Hi all,

Currently I have a VOX AC4TV amplifier. It is a great amp, but I want to build one. The amp that I have in mind is an 18Watt. I have included the circuit that I will be using.

Please note that it has two possible pre-amps. The one I am planning using is the “LitellB” option. A friend of mine has built an amp using both. He told me that he never uses the other one. I have heard a recording of the “LitellB” option he has made of this and it sounds great.

I want to have two channels. A “clean” channel without overdrive/distortion and a “dirty” channel, with overdrive/distortion. The “dirty” option is easy, because I will build it according to the drawing.

The clean channel is where I get stuck and is in need of some help. I was thinking to by-pass the phase invertor to get a clean channel. Is this correct? Can it really be that easy? If it is not correct, please advise me on how to do that. If it means that I have to build 2 pre-amp stages, that will be fine. I need to understand this.

The reason I was thinking of by-passing the phase convertor is of a paragraph that I read on the ampmaker web site. It speaks about the phase convertor: “…The guitar signal - still fairly clean at this point - is fed into the amp's phase inverter circuit. This uses two sides of a 12AX7 valve to create two signals for the amp's power valves - one out of phase with the other. The way that this stage reacts to the signal dictates a lot of the tonal characteristics of the amp. If the amp's Volume control is set above about 2, the incoming signal will start to overdrive the phase inverter valve to create some mild preamp distortion…”

It will have a VVR installed, in order to be able to play the amp without making the neighbours angry .

[HotBluePlates]

The amp that I have in mind is an 18Watt. ...

Please note that it has two possible pre-amps. The one I am planning using is the “LitellB” option. A friend of mine has built an amp using both. He told me that he never uses the other one. I have heard a recording of the “LitellB” option he has made of this and it sounds great.

I want to have two channels. A “clean” channel without overdrive/distortion and a “dirty” channel, with overdrive/distortion. The “dirty” option is easy, because I will build it according to the drawing.

The clean channel is where I get stuck and is in need of some help. I was thinking to by-pass the phase invertor to get a clean channel. ...

You can't dispense with the phase inverter because it is necessary to create a push-pull signal to drive the output tubes properly.

Looking at your schematic, I believe you already have a clean channel available. The Lite IIB preamp has two input jacks, labeled Single and Parallel. The Parallel input places both halves of that 12AX7 in parallel, which will increase the gain over using a single half of the 12AX7 by around 30%. When you use the Single input, you use only one triode and have somewhat reduced gain.

Further, you can't get fewer gain stages than the one triode obtained by using the Single input. So that is your clean channel benchmark. The Parallel input will increase gain some. Gain will be increased even more if you plug into the Superlite TMB input, as the pair of triodes are now cascaded, rather than being in parallel. Placing gain stages in parallel adds their individual gains, while placing them in cascade multiplies the individual stage gains.

For what it's worth, the Superlite TMB preamp is more akin to the topology of a tweed Deluxe, albeit with the tone circuit changed (to one with more flexibility but also more signal loss) and moved to a different point in the circuit.

If I were you, I'd build the entire amp as shown in your schematic. That would yield 3 channels of "Clean, More and Even More". All of these channels will play cleanly if you set the volume low enough (and the VVR high enough).

What you'd think you'll like and what you actually end up liking may be different things, and without experience and a certain knowledge of what will give you what you seek, having more option seems like a good idea.

Or, stick with the Lite IIB, as is. I bet the 18watt forum has more detail on layouts, build specifics, etc.

[phsyconoodler]

There is pretty much no way to get just 'clean' from the 18 watt amp.It's best to use your guita volume to get your cleans.
  The lo input on the 18 watt lite circuit is somewhat 'cleaner' but it's still dirty when cranked up.The distortion comes from the output tubes and very little from the preamp section.
  Clean and 18 watt Marshall are terms that don't fit together very well.You can get nice cleans but at lower volumes.
 
The two inputs do make it versatile.

[Robbiez]

I tried to register with the 18Watt forum. I have not recieved any email from them and it has already been 24 hours. Are they still active?

[Robbiez]

I was just informed by a friend of mine that the 18Watt forum site is broken. No new regestrations. Just my luck . I was wondering, is this the best desighn? I have a high diploma in electronic engineering, so I do understand the workings of these amps. Having said that, I am not that well versed in desighning them.
That is why, the question is this the best desighn.
My specks:
18 watt tube amp.
Decent overdrive channel
VVR, because I realy do not want to alienate my wife
A clean channel. This more a want than a need.
I started playing the electric because I fell in love with the overdrive sound. As I learn more, I like the instrument for more reasons, but I still love the sound.
If any one is willing to chat to me off-line and maybe help me building my dream amp, we can chat on my email: brj217@gmail.com
Thank you very much!

[phsyconoodler]

Not very good at listening either.
  They don't have a lot of clean headroom.Simple as that.
The EL84's are one of the only tubes that add gain to an amp.The only way you can get a clean channel is to attenuate it internally and then you don't get the volume.
  But as you 'don't want to alienate the wife,cleans would be no problem.These amps are plenty loud as is and simply turning down gets you the clean you need.
  With VVR it's easy to get saturated tones at low volumes.They work best with a master volume and VVR.
Two channels are not needed if you don't play live.You simply reach over to the amp and turn a knob.If you insist on having two channels build the TMB version and add VVR.
Go to www.ceriatone.com for a good TMB layout.Then go to Skipz circuits for a good VVR circuit.Cheap and easy to install.

[Tyrannocaster]

I have built several 18 watt Lite II B amps, so I'm quite familiar with them. They are a one trick pony in some way, although I happen to love the trick they do. You will never get a Blackface Fender sort of clean out of one - it isn't just the output tubes, the preamp is pretty limited tonally. BUT, having said that, if you don't crank the 18 watter you can get very acceptable clean tones out of it - but I bet you will want more tonal flexibility than its preamp offers.

I also built a version that had an extra channel which was from a Blonde Fender (I think I used one of the Blonde Twins, but I don't remember now I just looked it up and it was a 6G8) and that amp is one of my favorites now. Until it gets dirty, the cleans are very nice in this amp. As far as overdrive goes, the 18 watter won't give you heavy distortion and you'll need a gain boost if you want more that is on tap. However, the 18 watt has quite a bit of dirt available, especially with a reasonably hot pickup.

You can hear this amp here: http://www.box.net/shared/ns16vrklf7 The tune is a familiar one that I did as a test bed for recording how different amps sound over a known backing track. There is more explanation here which will tell you which amp is doing what (I also used another amp with an 18 watt power amp but a Tweed Bassman preamp - lots more drive there!): http://www.xprt.net/~benboom/Music/grunions.htm

I think the 18 Watt Lite is a great amp, and it's not too hard to build, which is nice.

[SleepLess]

I tried to register with the 18Watt forum. I have not recieved any email from them and it has already been 24 hours. Are they still active?

Don't worry mate, I've been waiting for my account to get activated for 18 months... 

[Tyrannocaster]

All of them are messed up. The SEWatt (and Wattkins, etc) site is just as bad. Those are all part of the same site and they don't send anything when you try to register, they REQUIRE registration to even read any messages at all, and they give NO contact email so you can't email them to tell them there is a problem with their registration system. They claim I am am already registered (or at least that my email has already been used), which could be because I used to be a member of the 18 watt board, but none of these sites will let me log in, none of them will send me a new password using my email address even though they show my address correctly, and so there's just no way to get in.

It's very poorly done, IMO.

[Robbiez]

I know that the moderators on this site are good. 

Can you perhaps send a mail to the moderators pointing out the issue? I have heard that there is a lot of excellent information on the site and would love to have a look at it.
Thanks.

[tubenit]

I want to have two channels. A “clean” channel without overdrive/distortion and a “dirty” channel, with overdrive/distortion. The “dirty” option is easy, because I will build it according to the drawing.

I want to add my two cents in also.  You've gotten feedback from others that the 18w is primarily an overdriven amp design.  I agree with that.  I think you will find the clean tones pretty elusive on that amp.

You might want to consider something like Geezer's HoSo56 and use 6AQ5 or 6V6 tubes.  The 6V6 or 6AQ5 tubes would allow a much cleaner tone to be possible, IMO.   With his "psuedo dual channel switching", you can relay switch between a clean and overdriven tone.

Geezer designed and refined the HoSo56.  He is an incredible guitarist and every sound clip I've heard him record has been absolutely stellar. There is a layout for this amp also.

As I understand it,  the HoSo56 is his favorite amp.  I don't think you could go wrong building one.

With respect, Tubenit

[Robbiez]

Thanks to all that gave me feedback and a lot to think about. I think I now have the design down except for three things:

1.   What is difference in using a solid-state rectifier and a valve?
2.   Any ideas on adding headphone functionality?
3.   How to I add a Line-out?

Now it is time to go on holiday and then build this amplifier.

I wish you all a blessed and peaceful weekend.

Robbie

[kagliostro]

A SS will give a higher B+ voltage and don't SAG

See attached image

k

[Robbiez]

Thank you!!!!   

[Tyrannocaster]

For one way to do your line out, look at the Matchless Lightning schematic. In fact, look at lots of the Lightning schematic, since it's another cathode biased EL84 amp, very simple. I prefer the 18 watter, but there are some nice things about the Lightning, too. 

[HotBluePlates]

Note also in Kagliostro's schematic fragment that the heavy black line between the line out and headphone sections is implied as ground, even though it's not marked in a way Americans will normally notice.

[Shrapnel]

One thing you won't miss about the 18Watt forum is, the total lockdown into everything 18Watt or WEM/Watkins. unless it varies too much from those designs. (ie. not much of a problem mating the 18W PA with a different pre-amp, but add a negative feedback loop into the mix, all of a sudden it is no longer 18Watt material.... thus not allowed.)

AS seen by any reader here, it don't matter the flavor of amp... tube in tube, SS in SS is all that's really cared about (and sometimes the lines do get blurred, which isn't grounds for locking a thread.) Hi-Fi, Guitar, Public Address, harmonica, vocal, doesn't matter. Doug's forum (this one here  ) is great for taking about any amp from any time period.

[Tyrannocaster]

If you go SS for the rectifiers, don't forget the small caps to cut noise out.

Could you explain that?

[Ed_Chambley]

Look up the TMB version of the board.  There is a schematic and layout there.  If you want a clean amp, you are looking the wrong way.  I have a 18 watter running to 6V6 and still not clean.  I also have a 18 watt preamp running 2 EL-34's.  This one will play clean as it is waaaaay more than 18 watts.  I am working on another variation as well.  This one will have 6L6's in it.  It will be the last 18 watter I mess with.  18 watters are cheap to build and faceplates and chassis are readily available, plus the parts can be used again if you don't like what you get.

If you want a smaller wattage amp which will play clean, build a blackface deluxe.  Put a booster pedal and add a master volume and if you are really interested in midrange grind put some ceramic speakers in it.  If that is too loud, which it probably will be, look at a princeton.

I love a marshall clean, but I know of only a few that will do it.  JTM-45, JCM800, Plexi.

[Rev D]

 I've built four varieties of 18 watters, the cleanest for me was the original with the Trem circuit and even that as everyone has mentioned is only clean to a point. One thing I have found that helps is speaker efficiency. I've ran a Eminence Wizard which has specs of like 103DB's at 1m/1watt and it at least allows you to get some volume when its turned down so you have a bit of clean. It also makes it incredibly loud when its turned up so its a trade off. Great sounding speaker for that circuit IMHO.

 Far as the 18watt community I started over there years and years ago, and have the same problem many do, I forgot whatever the password was supposed to be and asked about it and was told yeah you have an account already (when I tried to create a new one) under the same email address. (Well no duh, if I knew the password it wouldn't be a problem would it). I found them most unwilling to help and that along with the limits put on what you can discuss (as mentioned if it varies much at all your off topic and get a rash of stuff about it.) 

 If you want a 18 watt circuit, Doug has one here, Ceriatone and Weber do as well I've used all of them and they work as good as the one they posted over there and it was less drama. If you do a search though, you can find the one with ritchie's tweaks in other places which is they're layout. I don't like badmouthing another forum and I'll stop short of doing that, but I was less than happy over there than on other forums with allow a person to mod something without getting a flag thrown for thinking outside of the 18 watt way of doing things. Its rather amusing since half of the circuits (lite, lite IIb, TMB, superlite, flash lite (being funny there, there's no such thing) were never made by Marshall anyway. Far as I know they only made the Tremelo version and only for a few years because small amps weren't selling back then for Marshall anyway at least in numbers to make them profitable. The 18 watter was also really just as Marshall did in the early days a copy of the WEM Dominator (I think thats the correct brand) which was that amp with a radial speaker layout, its essentially the same or very much the same layout as Marshalls 18 watter (just like a JTM45 and Fender Bassman). Good luck in your travels!

Regards,

Don

[Tyrannocaster]

The point about efficient speakers is a good one. I use an Eminence Legend GB (102 dB IIRC) with mine and it's pretty loud; as mentioned, the louder speaker means you have clean tones on tap at higher levels too. I love the Legend; it's a great speaker, period.

All that 18 watt forum drama is best avoided IMO. Even Richie Hall (no "T" in his name) told me he was tired of the shenanigans over there. He did more than just about anybody to popularize the 18 watter and got dumped on by folks who wanted to make money from the amp.  It's a shame, because it is a very good amp. Here's my TMB (made before that's what it was called, and Richie helped me with the circuit tweaks) channeling 1968 Deep Purple: http://www.box.net/shared/unbk8iz3dn