15 watt Liverpool Combo Build

[skyboltone]

Kool. Thanks.

[El_Martin]

Hi Dana!

Thanx for the info on your ideas and especially the lil schemo for voltage regulation. TW 15 PP in my livingroom is prone to some sort of attenuation.

Fired up my TW this evening.
I've learned a bit:
1. I am too stupid to build a bridge rectifier
2. solder EVERY cable to its place
3. insulate from chassis what should be insulated
4. RG 58 mil spec should be treated proper. Make sure, shielding does not short the signal
4 a,b,c a few minor issues: wrong polarity of OT sec. etc.
5. the legendary double coupling cap: microphonic capacitor, anybody?

Besides these little problems it is running.
Using a hifi bass chassis as a load and not wanting to bring up the neighbors... feeds back even in lowest volumes.

Gonna be a nice little screamer, I bet. Who needs neighbors

I'll post a fred, when tweaking is finshed (or problems occur )

Ciao
Martin

[UR12]

Hi Dana!

Thanx for the info on your ideas and especially the lil schemo for voltage regulation. TW 15 PP in my livingroom is prone to some sort of attenuation.

Fired up my TW this evening.
I've learned a bit:
1. I am too stupid to build a bridge rectifier
2. solder EVERY cable to its place
3. insulate from chassis what should be insulated
4. RG 58 mil spec should be treated proper. Make sure, shielding does not short the signal
4 a,b,c a few minor issues: wrong polarity of OT sec. etc.
5. the legendary double coupling cap: microphonic capacitor, anybody?

Besides these little problems it is running.
Using a hifi bass chassis as a load and not wanting to bring up the neighbors... feeds back even in lowest volumes.

Gonna be a nice little screamer, I bet. Who needs neighbors

I'll post a fred, when tweaking is finshed (or problems occur )

Ciao
Martin

Martin

I think that everyone who has ever built an amp has had to learn the hard way the 5 things you posted above. The OT on any new build is 50 50 at best. Just flip a coin The important thing is that once you have heard one screamin like a banshee you know what to do to resolve it in a hurry. You now have EXPERIENCE and first hand knowledge with all of the above and you can't get that kind of experience from a book. Congrats on the build!! You should crank it up and see what the neighbors and the police think of it. The police have been to my house so many times they are starting to be critics. "That one sure was louder than the last one we came here to tell you to turn down"

[paulster]

The OT on any new build is 50 50 at best. Just flip a coin The important thing is that once you have heard one screamin like a banshee you know what to do to resolve it in a hurry.

If you have a scope then what I do whenever I get a new OT in is to put the 1KHz reference square wave it will have into the primary and then compare the primary and secondary on channels 1 and 2. From that you can be sure of the relative polarity of the primary and secondary.

It's nice knowing that you can wire it in without having to swap the wires round or to desolder and shorten the wires once you've established the correct way.

[UR12]

Paulster

I agree and have used the scope procedure but I think most of the guys out there probably don't have a scope and if the do, they don't have a dual channel or a sig generator. I can probably hook up the OT backwards, turn the amp on and get screeming , turn it off and reverse the leads faster than I can hook up the scope and generator. If you have the available test equipment and are taking your time and want to get it right the first time then the scope method is the way to go. I guess the point I am trying to make is that it is important to hear what happens when you hook it up wrong, so the next time it happens you will know imediately what the problem is.

[El_Martin]

Hi!

Got a scope. But as Dana pointed out: switching cables is faster.

Since I tend to use old/found/... parts, I always run into problems. So what?
Its a hobby. I'm in no hurry.

I guess it's about time to start my own fred. Thanks for letting me hijack yours, Dana!

Greetings from Germany!
Martin

[paulster]

I agree and have used the scope procedure but I think most of the guys out there probably don't have a scope and if the do, they don't have a dual channel or a sig generator. I can probably hook up the OT backwards, turn the amp on and get screeming , turn it off and reverse the leads faster than I can hook up the scope and generator. If you have the available test equipment and are taking your time and want to get it right the first time then the scope method is the way to go. I guess the point I am trying to make is that it is important to hear what happens when you hook it up wrong, so the next time it happens you will know imediately what the problem is.

Granted. I agree exactly that you need to recognise the symptoms and know how to troubleshoot it.

What people may not have thought of, though, is that just about every scope I've come across supplies a 1KHz reference square wave through a test point on the front so you can calibrate your probes when using the 10x multiplier. It's good enough to use this as a sig gen (in lieu of a real one) for testing and marking the OT polarity.

Of course, you have to understand the circuit and know which side of the PI is which before connecting the OT anyway, so I can understand it being overall quicker to suck it and see!

Paul

[El_Martin]

Hi Dana!

Can't identify the cable running from the vol pot. Is it shielded?
How much filtering do you use? Currently my first cap is 30 uF.

Ciao
Martin

[UR12]

Martin

Usually only the input jack to the first tube is shielded wire. Since you are not using a standard TW layout you will probably have to experiment and use more shielded wire if needed. If you go back and look at my 15watt combo pic you'll see that I used shielded cable from the input jack AND from the vol control to the tube. My first cap is actually 2 40uf caps hooked in parallel for a total of 80uf. Hope this helps!

[El_Martin]

Hi Dana!

Thanks again for your input.

I'd expect the hum to be (considerably?) lowered with a bit more filtering and a shielded cable from the vol pot.
I'll test some of these ideas and post my findings. After all I have to play it some time and swap some Rs and Cs. I'm not used to TWs so far.

Ciao
Martin

[StaticRick]

I think this is my first post here, but I lurk here often.

I'm resurrecting this thread to say that a couple hundred people at the Ohio Guitar Show today heard Dana's amp that was the original subject of this thread. There were lots of positive comments and inquiries. It sounds amazing and the power scaling is something to behold if you've never had the pleasure.

Best of all, Dana and Richie are wonderful guys in person. I hope they venture back to Columbus next year. I know I'm lucky to have met them. Thanks to hairyandy for the heads up and the reference!

[Richie]

Thanks for the kind words. I guess that answers the question of ,if you can build a wreck type amp into a combo.
We had a blast, and enjoyed meeting You,Andy, Mike and Frank,and many others.
It really helps when you have such great guitar players playing a amp.
We did get in a little trouble for firing up the Liverpool..
Its very hard to try out louder amp at the guitar show. It was like someones dad,telling us to turn it down,they yelled.. were trying to talk to a customer..
i thought, we paid the same as he did for a table...but we try to comply with the rules. been attending that show for about 20 years off and on.
Too bad we didn't fire up the Express..!!
Hopefully next time we will be more prepaired,and have quite a few other amps to bring with us.

Richie

[UR12]

Rick

Yes, thanks for the kind words. It was great meeting you, Andy, Frank and all of the others at the show. I must have missed Mike from Komboking some how. I am also very happy everyone liked the amp.

It was really funny when the guy next to us wanted to fire up the Liverpool. He barely cracked the thing past one and it was so loud I think everyone in the place glanced our way and like Richie said, the dude behind us went off like a dad scolding a 2 year old We'll be talking about that one for years to come.

I also picked up a Quad of NOS GE EL84s and 3 NOS matched pairs of National (Made in Germany) 6CA7/EL34s for about 1/2 the going rate.

[hairyandy]

I had a great time yesterday. It really made the show fun for the first time in a few years, it sucks how the Columbus Guitar Show has gone so down hill lately! It was great to finally meet Dana and Richie and hear their amps in person. I'm looking forward to hearing more of that 15w Liverpool combo, damn was that thing cool! Good score on those tubes Dana! I saw that guy over on the side but I wasn't sure if those Siemens were matched or not. I scored a matched quad of those last year in Milwaukee for $150 so I can't complain. I'm glad you got 'em, they're perfect for an Express!

Hopefully I'll be home to catch you guys in March when Trower is in Columbus at the Newport. Frank Harrison is opening, and hopefully Mike Nugen will be here to play with him at that show as well. The two of them on stage together is a sight to behold! Trower better bring his A-game if that's the case...

Rock on,

Andy

[krash]

You know I'm building a similar amp right now, but with an extra "clean" channel (using the unused 1/2 tube), cut control instead of presence control, and in a 1x12 Revelation cabinet/chassis style. My own layout.

Anyway, my TW-inspired Princeton Reverb mod, in a 1x12 open-back cabinet was extremely bright. I ended up changing the slope resistor to about 47K and putting in a Weber ceramic Silver Bell and if I run the bass on 10 and treble on 0 then it's pretty tolerable. I also built a Liverpool inspired amp in my Classic 30 chassis/cabinet and it was insanely bright through an Eminence Private Jack in the open-back cab. Maybe it's these vintage-spec pickups. You know a strat with 5.6K pickups is pretty bright.

I think my new project amp will employ some extra grid resistances to knock the treble down to suit an open-back cabinet. I may end up with a real dark speaker like a Cannabis Rex. The cut control in place of the presence control is all about making it work in an open-back format.

OTOH my other amp designs that I voiced originally to run with open-back 1x12 combo cabs are an incredible wall of sound when running in a 4x12.

I think amp voicing needs to be related very closely to the cabinet choice.