Fault-finding hum(s) on a Liverpool - Distress call

[plook]

I did some re-wiring following the layout by Ron Worley, the Presence area, removed all the screen wires except the one on the input jack to V1, put the amp in the cabinet and there is a noticeable improvement:

1. the MT hum is not noticeable when the chassis is in the cab - great
2. the sizzling bacon issue seems to be gone
3. The main hum problem has reduced but is still not great, but the tube lighting, close proximity to amp (within 3 feet), a computer, all the things Geetarpicker kindly pointed out could be impacting on it, so the real test will be tomorrow in daylight at a big distance.

Some points on the sound on the amp, or the tone. It does not seem to have much bottom end, seems very toppy, but i have so far only connected to a 3-10 cabinet. Tomorrow i'll connect to a 1-15 Weber and when i have a chance i'll put some Celestion V30s in a 2-10 i have a check that out.

There does not actually seem to be much in the way of distortion but this could be because i'm on relatively low volume due to it being late and i have not yet fitted the VVR. Talking of which, is this a cathode biased amp or fixed bias. Which version of the VVR would go in this amp?

Something else i noticed, when i experimented with plugging a Treble Booster in and rolled all pots off except volume - which was full on, there was no output at all until i rolled the bass up a bit. Is that a fault?

[plook]

On some builds the ground plate is 100% essential!


Are you saying that IF you keep the guitar turned down the hum is gone?

You say the hum comes back if you raise the amp volume to around 2pm, but is that with the guitar still OFF or ON?

Yes, with the vol pot on the guitar turn all the way down the hum is gone. if you turn the volume up on the amp when guitar vol is down you just get normal level of hiss, but no hum.

I think we are getting close.

[plook]

On some builds the ground plate is 100% essential!


Are you saying that IF you keep the guitar turned down the hum is gone?

You say the hum comes back if you raise the amp volume to around 2pm, but is that with the guitar still OFF or ON?

Would i have to remove everything to put this ground plate in? Is there a picture of it in the files? I'll go look.

[John_P_WI]

There does not actually seem to be much in the way of distortion but this could be because i'm on relatively low volume due to it being late and i have not yet fitted the VVR. Talking of which, is this a cathode biased amp or fixed bias. Which version of the VVR would go in this amp?

The Liverpool, as designed, is cathode biased. Make sure you resolve your ground / hum issues and your amp is working properly before installing VVR.

The ground plate Glen is referring to is a metal plate that fits over the bottom of your chassis, basically a lid to keep stray electrical noise out. You can also put thin metal on the inside bottom of the cabinet, so when the chassis is slid in, it contacts the metal.

[geetarpicker]

On some builds the ground plate is 100% essential!


Are you saying that IF you keep the guitar turned down the hum is gone?

You say the hum comes back if you raise the amp volume to around 2pm, but is that with the guitar still OFF or ON?

Yes, with the vol pot on the guitar turn all the way down the hum is gone. if you turn the volume up on the amp when guitar vol is down you just get normal level of hiss, but no hum.

I think we are getting close.

Seems the amp is probably not the cause of the hum, it's simply hum the guitars are picking up at such high gain. Turn off any fluorescant lighting, any lights with light dimmers on them even if in the next room, floor, or even neighbors if you are in a town house or apartment (good luck), and have the guitar out in the middle of a larger room away from any of the walls if possible. Then you will still probably notice a little hum pickup if your guitar is pointed the wrong way. As crazy as this all sounds just about any high gain rig will have these issues with single coil guitars and some even with humbuckers.

Think of it this way, most modern amps you only kick on the high gain (pedal or amp channel) when you need it but usually click it off when you don't. With the Express/Liverpool it's like being stuck on high gain ALL the time. One detail though is even with all the gain on tap a good TW will still clean up very well, unlike most other high gain options. In the end it will be well worth it and even the hum and noise should be quite workable. Having a TW is like owning a Ferrari, you can't expect it to be as easy to setup and work with as a tweed Deluxe or something.

Still that means you really have to work with the details to control the hum and noise. Personally I have a Suhr hum cancelling back plate in my Relic Strat, and I wish I could have had that years ago as it works wonders with my standard Fralin single coils.

Speaker wise yes most TWs don't have a ton of bass, and I'd be quite hesitant to think a 10" speaker would do it justice. To me they are 12" speaker amps, 4x12 prefered though a Liverpool on an AC30 2x12 ext. cab w/blues is a beautiful thing. That said the choice of OT can have an effect on that too, and even the choice of hookup wire in the amp can make it brighter or darker...

Here is a pic of an original TW bottom. The original plates screwed on, but you can fabricate something to attach to your cab to do the same job.

[plook]

Thank you so much for all your help everyone. It never fails to amaze me just how helpful and kind people are in amp building forums. I used to think i was okay at building valve amps as i have actually made quite a lot, including Dumbles, but this one really has made me feel like a total beginner. I bow to the experts here and i'm extremely grateful for the help.

I'm about to go out to my garage and test it in a 2-12 vintage Celestion alnico blue and silver (1959) cab i have. I'd love to build a 4-12 but i fear my marriage would crumble.

That description of the TW being on 'high gain' really is helpful and puts expectations into perspective.

I have some metal sheet that would be perfect for the back plate. At first i was thinking the plate was something that goes inside of the amp before you fit anything to the base, hence my horror at the thought of having to start again. Are they self-tapping screws on that backplate, or is there a captive nut in the chassis for each screw. What is that one in the middle? The raided bits where the bolts go through from the cabinet makes this look like it was pressed.

Will come back later with results of isolated 2-12 test.

By the way, i made alterations to the amp yesterday using the RW layout and it reminded me that i started out with this last year but switched to the C@riatone one because there are a few places on the layout where coloured wires have strayed, such as the Presence to impedance selector wire, a wire on one of the EL84s and a few other places if i recall. Of course, were i smart i should have cross-referenced with the schematic, but one can get lazy sometimes. A lesson for me there!

[Gibsonman63]

Congrats on your progress.

For the coverplate, you will most likely need to drill and tap some holes. If you carefully position some wide painter's tape inside the chassis under the holes you are drilling, you can catch a lot of the metal shavings.

One lesson learned from my first build: I evenly spaced all of the holes for the cover plate only to find out later that one of the screws made contact with and shorted out a potentiometer lug. On the front side of the chassis, position your holes between the pots even it it looks off center.

I tend to use a darker sounding speaker for my clones. When I was playing Marshalls a lot I found that I needed a bright sounding speaker (vintage 30s) for clarity, but for these circuits they can be very bright. Get it in a bigger room, work the hell out of the volume control on your guitar and have fun.

[John_P_WI]

I'd love to build a 4-12 but i fear my marriage would crumble.

A 4 x 12 is forever.... just saying

[plook]

I'd love to build a 4-12 but i fear my marriage would crumble.

A 4 x 12 is forever.... just saying

I feel a devil on my shoulder. I might have to obey him.

Well, i didn't have time to get my vintage Celestions in the cab, but i have a Greenback and a Goodmans in there and took the cab, the Liverpool and my Tokai 335 to my good friend Chris who could really hammer it while i took a short movie. Here is the result:

http://youtu.be/pRFT_tTlHcE


The recorded sound is not great due to limitations of the compact digital camera, but there was no hum at all and to our ears it sounded really fantastic.

What do you think?

[passfan]

Sure sounded like a trainwreck to me, congrats.

[plook]

What shall i build next?

Are there any Brits here who have used UK sourced transformers with good results? I used Heyboer and Edcore but i picked them up while on holiday there.

[zambo]

Thats a good sounding amp. Nice work!

[hans-jörg]

Hi,
I want (would) build a Concorde or Komet 60 as the next amp.
I mean: I will, thats shure. I have only give my wife a litte time to breath before the next.
I built meanwhile a 1,5 Watt Express with ecc82 PP Poweramp and evan this small animal sounds greate although triode PP.

Best

Hans-Jörg

[plook]

Well, my work isn't over yet. Turns out i'm a bit premature with thinking the hums are gone. I'm just down to the MT hum now. I thought it was okay because the room i was testing in had a lot of background noise, but testing again in the house in the evening the MT is far too loud. The great thing is that i have actually traced it down to the MT itself, which is a Heyboer HTS 5199 120/240 AC. i bought from RJ Guitars summer 2010. With all secondaries disconnected it is exactly the same. Obviously it's out of warrantee with Bob and Heyboer, so is there anything i can do to the transformer to make it quieter. If not i'll have to get the specs and get one made here in UK at Trans-tronic, expensive though.

[zambo]

can you move it or the OT? Are they interacting with each other to cause the hum?