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Old 11-24-2012, 10:12 AM   #1
JimmyCraig
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Hiring someone to do a custom amp...but....

Right so I found out one of my aquaintences knows how to build amps, and I hired him to do mine. I called about the status and he asked me a few standard questions, although one has been troubling me....he asked me "do you want me to put volume and tone knobs on?" and explained how he thought controlling it from the guitar is better. This I find somewhat worrying for a number of reasons...
1. When I turn down my guitar volume on my current amp I get very very weak distortion compared to when it is full volume with the amp on lower volume. will this mean that I will only be able to get good distortion on a very high volume?
2. Will this limit the versatility of my amp?
So has anyone else got a amp with no knobs? I'd like to hear your stories.

I play blues rock mostly, I like dirty sound, but occasionally do want to play a nice clean. I play a strat and the amp will be a separate head and cab 35w full tube. Thanks in advance for help
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Old 11-24-2012, 10:28 AM   #2
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If you want a 35W blues amp tell him to do a clone of the 18W Marshall with double the output tubes. There are several 36W schematics out there, no need to reinvent the wheel. There is a whole community of 18W builders, and for good reason. They are the best blues amp ever made.
The normal 18W'er has just a volume and a tone control. There are also circuits out there that add TMB (treble, mids, bass) controls but they detract from the purity of the 18W'er because you have to add another tube. It's the extreme simplicity of the circuit that makes an 18W'er what it is and quite frankly, they don't need a TMB.
And whatever you do, make sure it uses a tube rectifier, SS rectifiers on 18W'ers just don't work.
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Old 11-24-2012, 10:29 AM   #3
Dave_Mc
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1: not only that, but if you don't have a master volume (i.e. gain and volume controls) or some form of power scaling you can't get distortion at low volumes anyway. so if you want distortion at low volumes you need a master volume and/or powerscaling.

2: yeah it will. i sorta know what he's saying, but i'm not sure it's any use in most real-world scenarios. It'd be a bit like saying "do you want brakes in your car? because it's more fun to drive without brakes!"

plus rolling your guitar's volume down can sometimes have an adverse effect on the sound- you can lose all your top end if you don't have a treble bleed cap on the volume (and some people think having treble bleed caps thin out the sound so much, a treble bleed cap isn't a panacea).
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Old 11-24-2012, 10:39 AM   #4
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Couldn't find a 36W without the TMB but the TMB one is pretty good. Here's the schematic. It also has a master volume so you can still coax some dirt out of it at lower volumes.
http://mhuss.com/18watt/schematics/36wTMB.gif

You don't really need a MV on an 18W'er but it would be worthwhile if building a 36W'er. I'd just use that circuit. ^ It comes from 18watt.com so it's been pretty well picked over by the community for errors.
18watt.com is currently closed to new members but I've been a member for ages. Let me know if you can't see that schematic and I'll make a copy of it somewhere where you can see it.
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Old 11-24-2012, 11:28 AM   #5
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Quote:
Originally Posted by Cathbard
Couldn't find a 36W without the TMB but the TMB one is pretty good. Here's the schematic. It also has a master volume so you can still coax some dirt out of it at lower volumes.
http://mhuss.com/18watt/schematics/36wTMB.gif

You don't really need a MV on an 18W'er but it would be worthwhile if building a 36W'er. I'd just use that circuit. ^ It comes from 18watt.com so it's been pretty well picked over by the community for errors.
18watt.com is currently closed to new members but I've been a member for ages. Let me know if you can't see that schematic and I'll make a copy of it somewhere where you can see it.


All of the above is helpfull, but this guy takes the medal! Way to go nice guy (we need more people who actually help)
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Old 11-24-2012, 11:53 AM   #6
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After having a good look at that schematic I'd build the circuitry before V1 differently. Those four inputs are pointless. Substitute this for the input wiring feeding V1. With this configuration you can use an ABY pedal out front into the two inputs to great effect.
http://cathbard.com/images/amps/cat...arshall-18W.pdf

That's my iteration of the 18w'er. It's pretty much identical to the original 1974 but I have beefed up the power supply filtering and removed the tremelo. The filtering will be different for the 36W'er and that schematic seems to have that pretty much covered. That's about as far as you can go with that rectifier and it isn't enough to damage the sag that you want with this type of amp.
But piss off the four inputs and use my circuit for that particular part. So you'll end up with a single channel volume (gain) and a master volume. You don't need the complexity following V1 in that 36W circuit either, just omit my tone control and run the output of my volume control directly into the grid of V2a on the 36W circuit.

PS: I've made quite a few 18W'ers. As greg (I think) once said, "Building 18W'ers are what old techs do instead of playing shuffleboard."
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Last edited by Cathbard : 11-24-2012 at 12:01 PM.
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Old 11-24-2012, 12:27 PM   #7
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well, i would say that it depends. its very possible to run a single channel and with a volume knob on a good amp get great crunch and good cleans. look at Dr. Z...thats pretty much all his amps do.

basically your getting into a design where there is absolutely no uneeded stuff, everything based around a pure signal path. less knobs, less stuff in the way.

the most transparent amp i have played are Dr. Zs....and they are almost too sensitive and transparent. i actually sounded bad first go around. every nuance good or bad comes out. it really is on the player.

however, most single channels amps of any significant watts that are made well can be VERY loud. ....like Dr. Z amps.

non master volume amps to get really rocking are not going to be bedroom amps clear and simple.

but yeah with a well made amp, using combinations of ODs, boosts, and a volume knob you really can get a whole pletora of tones. its gonna be more involved, like you are mixing tones yourself rather than have a 3-4 channel modern beast where you set everything, click a channel 1 time, and thats your tone.

i recently have been running my tweaker clean channel HOT (switch gives it a 9 DB gain boost) and then boosting it with the Xotic, rolling volume down. gives it a nice deep tone on the verge of breakup, and i can turn volume up to get good breakup and a good lead tone for clean / blues stuff.

personally, would i own an amp with no volume or gain? no. not without my own house.
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Last edited by ikey_ : 11-24-2012 at 12:42 PM.
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Old 11-24-2012, 12:37 PM   #8
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I run my 18W'ers pretty much with the volume dimed at all times and control distortion with my guitar volume and pick attack. Of course I do own my own house.

I think what I am suggesting would be the best plan of attack though. Best of all worlds really if you want the extra power/headroom of a 36W'er. Personally I love my 18W'ers but they do have a bit of trouble keeping up with a drummer while remaining clean. Best sounding amp ever though. No studio should be without an 18W'er.
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Old 11-24-2012, 12:42 PM   #9
ikey_
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of course, your forgetting the design of the map which affects how it breaks up, as does setup and guitar.

some 18 watters are going to be cleaner than others, especially a 2 channel where the clean channel is meant to STAY CLEAN
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Old 11-24-2012, 12:47 PM   #10
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I was of course talking about real 18W'ers. ie the Marshall 1974.
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Old 11-24-2012, 12:52 PM   #11
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it's worth bearing in mind that cath is a crazy bastard when it comes to volume I'm glad my 18 watt clone has VVR (a form of powerscaling). I generally run the volume on mine around the 6-7 mark and then bring the volume down with the vvr/power control. it cleans up better like that and i can hit it with pedals to get more dirt (plus mine's a wee bit dodgy and the bass goes woofy and weird if i crank it to 10... that's probably the main reason. i used to crank it to 10 and still hit it with pedals ).
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Old 11-24-2012, 12:56 PM   #12
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Pretty sure I saw the VVR schematic on 18W.com but if you use the tmb circuit you get a mv so vvr is moot.
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Old 11-24-2012, 01:02 PM   #13
Dave_Mc
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doesn't vvr let you get power tube distortion? i know i always say i like preamp tube distortion, but for a more vintage circuit like that, getting something that sounds closer to how it does when it's cranked up is probably a good idea. Then again, maybe it's a good-sounding MV, in which case, it'd be fine.
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Old 11-24-2012, 01:21 PM   #14
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It's a pretty good MV. Running the tubes cold with power scaling never produces the same power tube distortion as it does on full voltage. The guy doing the build sounds a little inexperienced so the 36W'er with my front end would be the way to go I think.
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Old 11-24-2012, 01:24 PM   #15
Dave_Mc
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yeah probably

and yeah the vvr doesn't really sound the same as the thing cranked way up. it is pretty good, though.
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Old 11-24-2012, 01:31 PM   #16
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It's just something else to go wrong. The beauty of the 18W'er is its simplicity, I don't even like master volumes and TMB's on them. One volume, one tone and crank it. Bewdiful.
A MV on a 36W'er is worth having though otherwise you are dealing with JTM45 volumes to get any breakup. Not everybody can crank their JTM45's like I do.
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Old 11-25-2012, 09:06 AM   #17
Dave_Mc
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Quote:
Originally Posted by Cathbard
(a) It's just something else to go wrong. The beauty of the 18W'er is its simplicity, I don't even like master volumes and TMB's on them. One volume, one tone and crank it. Bewdiful.
(b) A MV on a 36W'er is worth having though otherwise you are dealing with JTM45 volumes to get any breakup. Not everybody can crank their JTM45's like I do.


(a) i hear that. it's entirely possible that's what's gone wrong with mine. That being said, there's no way i could use it the way I do without it, so (for me, anyway) it's worth it. As long as mine is fixable for not too much money, lol.

(b) oh yeah definitely, 36W is silly volumes.
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