Built my first 18W, some observations

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cuffers65240
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Built my first 18W, some observations

Post by cuffers65240 »

Good Sunday Morning to the 18Watt world. After some years of thinking about building an amp, I took the plunge and built the Ted Weber 18Watt TMB kit as a combo. I have held off on posting while I got used to it for a couple of months but now have some questions and observations.

1. First off, I am shocked at the almost total lack of hum or hiss when it is on. I have worked on tube and solid state amps in the past and they all make some noise but this thing is silent. I did not follow any of the grounding scheme shown on the layout that comes with these kits and instead ran a solid 12AWG copper bare wire down the length of the circuit board that floats in the air between the board and the pots. All grounds are soldered to this with little jumpers and one end is bonded to one of the mounting posts on the power transformer. Which brings me to observation #2..

2. The amp really only comes alive with volume pots at noon or higher. The amp works at lower volumes but there is no compression or fullness of the tone below the noon position. I am not terribly shocked at this, just an observation. This may or may not relate to #1 in that maybe the amp is supposed to have a full, rounded tone at lower volumes?

3. I can't wait to get a set of beam blockers, the high pitch harmonics that shoot out like icepicks from the speaker cone are sometimes unbearable. The speaker is a new 25W Celestion G12H greenback.

4. I was not sure I loved the amp until I added a compressor pedal, things really came alive after that addition. My guitar is an Ibanez AS-83 which is a copy of a Gibson ES-335. I was sure I had crap pickups before compression was added, now I am sure I will never have to blow $2500 on the real thing. The pedal is a Keeley Compressor.

5. The vintage-y and blues-y tones are amazing, it is what I expected after playing one of the reissue Marshall 1974X's in a guitar shop a few years back. Really no complaints. Really nails Keith Richards tones from old stones songs. I use an A/B switch to go between channels as well as an Ibanez Turbo Tube Screamer pedal (it has 4 different distortion modes). The one question I have is can you get a modern high gain distortion sound from this amp by using a certain pedal? When I really crank up the Tube Screamer I get distortion but it mostly just gets louder. This is not a complaint, I built an 18watt to get a certain tone but it would be nice if it could transform when needed. I am thinking about something that is essentially another tube gain stage, like the Firefly preamp turned into a pedal (from the AX-84 site).
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crgfrench
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Re: Built my first 18W, some observations

Post by crgfrench »

Are you using the Weber coppercap rectifier?
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cuffers65240
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Re: Built my first 18W, some observations

Post by cuffers65240 »

Yes, using the copper cap rectifier instead of a tube. The only change I made was to buy a fender style green jewel lamp instead of using the tiny LED that came with the kit.
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Re: Built my first 18W, some observations

Post by crgfrench »

Have you tried plugging your guitar into the TMB channel high gain jack (J4 on the Weber schematic) and running a short patch cord from the TMB lo gain jack (J3) to the Normal channel high gain jack (J2)? When I do that on my 36W build with a similar PI topology it sounds full, lush, awesome. Of course, even awesomer with the volume cranked up.
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Re: Built my first 18W, some observations

Post by morcey2 »

Something that you can do to the speaker to get rid of some of the ice-pick highs is to break it in really good. The last new speakers I bought I hooked up to a 20 watt stereo system and ran them fairly loud for most of a weekend. (we were out of town so we didn't have to hear it. :D ) The speakers (a pair of 25-watt greenbacks on one channel, a V30 and a G12H30 on the other) all sounded so much better when we got back. Granted, I wasn't driving them anywhere near their max, but it worked.

I don't have a TMB, but I have a normal 18-watt head and a Lite IIb. I don't think you're going to get modern high gain distortion from a TMB. You could push the input with a boost pedal (I use an Omega boost from ROG), but that will still only get you so far. You'll probably want to get a high gain pedal for that sound. Or build another amp. 8) That's always an option.

Matt
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Re: Built my first 18W, some observations

Post by Bieworm »

This is exactly what's been persued since the dawn of time. It's that nasty compromise to keep away muddiness at higher OD levels. You could add body on lower volumes with larger value caps, but that will cause mud when cranked.
OTOH my experience is that Josh's Tremolo TMB doesn't suffer from that phenomenon. It's a pretty balanced amp over the entire volume line. I have 2 of them, so I can testify with confidence. Ok, it's a single channel amp.. but what an amp! Add reverb and it's pretty much the Swiss Army Knife among the amps . A very pretty preamp overdrive on low volume which only gets blissfully greasier and nastier when really cranked. People on this forum can confirm I'm vastly in love with mine. You just know you're in love when you can't stop thinking or can't stop talking about it ;)

What you experience is normal on simple amp circuits. Fender tends to thicken the low volumes, but at the expense of a nice and tight overdrive. Amps that appear to have the thick sound on tap from low to high volume are more often very complex circuits. Those are full of mosfets and other stuff to compensate for this. Downside on those amps is they lack the character and touch sensitivity these 18 watts ooze..
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cuffers65240
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Re: Built my first 18W, some observations

Post by cuffers65240 »

crgfrench wrote:
Sun 01/17/21 6:41 pm
Have you tried plugging your guitar into the TMB channel high gain jack (J4 on the Weber schematic) and running a short patch cord from the TMB lo gain jack (J3) to the Normal channel high gain jack (J2)? When I do that on my 36W build with a similar PI topology it sounds full, lush, awesome. Of course, even awesomer with the volume cranked up.
Thanks, that is a good suggestion. Something to play with when I get home from work today.
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Re: Built my first 18W, some observations

Post by JMPGuitars »

cuffers65240 wrote:
Sun 01/17/21 4:57 pm
The one question I have is can you get a modern high gain distortion sound from this amp by using a certain pedal? When I really crank up the Tube Screamer I get distortion but it mostly just gets louder. This is not a complaint, I built an 18watt to get a certain tone but it would be nice if it could transform when needed. I am thinking about something that is essentially another tube gain stage, like the Firefly preamp turned into a pedal (from the AX-84 site).
From your description, it sounds to me like you're running a higher B+ than normal, which is why you're getting more headroom before the distortion kicks in. I think the typical 18W gets breakup around 30 to 40% volume, and from there increases distortion as it goes up. You could experiment with using a rectifier tube instead of the copper cap. You could also post your amp voltages and we can see what's going on that way.

Any high gain distortion pedal will likely sound fine in the amp. One that I enjoyed was a tube distortion pedal from Radial. I think it was the Tonebone series. The tube screamer won't get as dirty as you want, it's not typically intended as modern high gain. It's almost a little redundant with an 18W except for helping you avoid making your ears bleed based on volume levels. ;)

Personally, I have a dual distortion pedal I made that is half violet BMP, and half RAT. They get plenty dirty for my taste.

I wouldn't modify your ground scheme right now, as you said it's dead quiet. I'm happy you didn't follow their terrible ground scheme. If you do anything to modify your amp and start to hear some noise, the primary change would be to separate the ground bus so that the pre amp and power amp are separate. Power amp should go to the star ground (preferably with its own connection to the chassis, not a transformer mount), and the preamp would get grounded near the input jack. But again, don't bother right now if you're not getting any noise or hum.

Thanks,
Josh
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