Still no break-up. 2x 5F1's.

[Sea Chief]

Hi Chaps-

some may be aware of my quest of getting some amp distortion. 2nd 5F1 and still none.

Ok amp1 one is a 5F1 + a tone + SS rectifier/ I cant remember exactly what it is! but a simple SE 6v6 5w. I turn up.. barely a fart of distortion. PT is rated only 254v-0-254v so for the mo Im going to leave this build/ call it the PT's low rating is cause for no distortion (this may or may not be true but line drawn for now).

I think of putting in a Champ PT into it then, for it has a good hammond 125 ESE ot/ generally sounds good (but clean all the way). So s'one I know offers a fender "600 amp PT rewound to Champ specs with 5v rectifier wires" for a decent price (also has 5F1 board/ tubes good spares & chassis: a full amp I was going to plunder PT & board from). So I test amp2, it works so I turn up.. barely a fart of distortion. Godammit!

Unbelievable. So now no point putting PT into my amp1/ Im back at square 1. Someone up there is not on my side with tube amps, but I plow on/ insist I find the reason why & get one of these amps to OD. Its infuriating when I read "my amp breaks up too soon" as to me any break-up is like finding the holy grail. Years and years Ive spent now trying to find out what it is, what causes it, and how I can obtain it (Once a 5E3, just into OD yes but so ferociously loud I enjoyed all of 2 full minutes: unuseable & shelved).

My suspicion again (rightly or wrongly) falls on amp2's PT. I want help to rule this out if you'd be so helpful. If I find it is indeed a "Champ spec PT" then I can use in amp1 and go from there. Now I was sent (I bought the amp on basis of) a diagram from the guy who rewound it (apparantly) showing 325-0-325v, 6.3v, 5.0v secondaries. As amp1 is only 254-0-254v and similarly breaks up only a gnat's.. my suspicion is the diagram is utter bllx & it not a Champ spec'd PT but just the 600amp PT + rectifier wires added, which I suspect (tho cant find info on) might be lower secondary HV voltages than needed for a Champ.. and hence the reason for amp2's no break-up.

Can someone remind me how to test amp2's HV red wire pair going to the rectifier- its been a few years since I built amp1/ Im a bit rusty. Thanks Sea Chief.

[Chuck H]

Sea Chief,

You've got to get that low PT voltage as a cause out of your head. It's blocking your ability to find the real problem. Consider this, if you had installed a VVR or "power scaling" circuit on either amp they would still sound very similar at any volume setting, yet the voltages would be much, much lower than even what you have now. In fact, VVR and power scaling circuits are designed to allow for tube amp distortion at lower wattages precisely because they lower voltages on the power tubes (or even the whole amp sometimes). Ok... Moving on...

It has been suggested before (in another thread) that you try your rig, guitar, pedals, etc. just as you use it through another Champ style amp as soon as possible. Has this happened yet? Perhaps you could try someone else's guitar and pedals through your amps?

Are you using the guitars volume controls?

The tone control circuits will seriously squash signals. Are you cranking up the tone controls as well?

It's hard for me to imagine that you have the same gain dumping mistake on two amps, but not impossible, power transformer not withstanding. So, assuming the amps are fine, what else could be the problem?

I said before, in another thread, a dimed Champ, even with a tone stack, should grind at least a little. Without a tone stack it should grind a lot, even with single coils. And I want to be perfectly clear about this, slightly low plate voltage won't stop it.

I believe your problem is a similar design flaw in both amps, a failure of something in the chain other than the amps or even operator error. Almost anything other than lowish plate volts. You've been told this before and went right back to it. Now your back here with another new thread beating the same drum again. This isn't your problem. So, if I may offer an analogy, if you lose your wallet in the living room there's no chance of finding it in the kitchen even though the light is better. In other words, Stop fixating on this one minor design variance, Take it from the guys that know, this shouldn't cause your problem. It's a red herring and your looking in the wrong place.

[Jazz P Bass]

5F1

The HV winding is tested under power as any other.
Set your meter to read Volts AC & clip your meter probes on each wire.

The B+ is measured with respect to ground, Vdc.

If your amp does not break up I would consider first of all removing the feedback resistor (22K that comes off of the OT secondary).
Secondly, there is only 1/2 of a 12AX7 involved in the preamp.
Not much to be had, gain wise, here.

With that thought in mind I would question what guitar/ pickup you are using.
If you do not have 'hot' pickups, the amp will never be 'overdriven'.
There is a huge output difference between the bridge PU & the tail PU, also.
The bridge typically is bassier which will result in a hotter signal.

This is a low power amp, plain & simple.
If you really want it to 'break up' then you may want to consider a boost pedal out in front.

[Sea Chief]

Sea Chief,
I believe your problem is a similar design flaw in both amps,

2 similar amps, built by 2 different people who have never even met, in 2 different countries?

There is logic to why I still point to the PT, for it is only thing they have in common (assuming I have been sold a 600 PT which afaict has lower seconday HV wires instead of a proper V Champ PT) as being the possible cause.. is the PT's lower voltage ratings on the PT secondary HV pair. Nothing else these 2 amps have in common whatsoever, not even one similar capacitor.

As for gtr vol- of course yes I have it turned up, all the pots/ all the time. I've never had cause, ever, to turn any down: when I get some dimed tone.. then I might be able to start using them as they can be used, ie rolling off for a cleaner sound- this is a pipe-dream/ a madman's dream for me so insufferable this quest to get some dimed tone is. Honestly I wouldn't be so daft as to explain my predicament if I hadn't checked such basics. Operator error? you turn the amp on, plug a gtr in and turn the vol up on amp (and, of course the gtr!)- how can there be any operator error involved?!

Thanks Sea Chief.

[Sea Chief]

The HV winding is tested under power as any other.
Set your meter to read Volts AC & clip your meter probes on each wire.

The B+ is measured with respect to ground, Vdc.

If your amp does not break up I would consider first of all removing the feedback resistor (22K that comes off of the OT secondary).
Secondly, there is only 1/2 of a 12AX7 involved in the preamp.
Not much to be had, gain wise, here.

With that thought in mind I would question what guitar/ pickup you are using.
If you do not have 'hot' pickups, the amp will never be 'overdriven'.
There is a huge output difference between the bridge PU & the tail PU, also.
The bridge typically is bassier which will result in a hotter signal.

This is a low power amp, plain & simple.
If you really want it to 'break up' then you may want to consider a boost pedal out in front.

Its a gibson sg. A gtr that is designed to sing when played into a dimed amp, not neccessarily a clean sound. I'm not going to start removing anything from the circuit or adding pedals! (I may as well whack my OD pedal in front- !NOmeansNO!). It should distort, its a simple low powered amp. If it doesn't there is a reason to which I need help finding. Changing the circuit isn't finding the reason. To find the reason logic must be applied, as any tricky job with no clues; in this case the only logical thing/ the only thing they have on common is the PT's lower voltage rating than what it should be. (80-100v discrepency surely is going to make a difference: my hunch is it makes the difference between a dimed tone cranked, and barely a fart of distortion I get at high volume in both amps). Once I rule this out- as its obviously the place to start if its the only thing they have in common- then I can begin to try and figure out why.

To test the HV pair on amp2 do I: leave all tubes & speaker in, set MM to VAC and one probe on chassis gnd and t'other on the 5Y3 rectifier's pins 4/ read, then pwr down etc > repeat onto pin 6. I think this is right but best to make sure as its been a while.

Thanks, Sea Chief.

[Chuck H]

I was under the impression that YOU built both amps. Probably because of your familiarity with things like the actual transformer models, specific voltages and how the amps circuits vary from a stock 5f1. So I'm going to leave the amps out of the equation for now.

Jazz is right that there isn't a lot of gain in a Champ. But it doesn't take a lot of gain to get crunchy. I could buy that your Champ w/tone stack might only break up a little bit with single coils. With an SG even the losses of a tone stack shouldn't keep the amp clean. A Champ type amp without a tone control or with a simple high cut circuit should growl like crazy with an SG.

And I wasn't trying to insult anyone. By operator error I meant to include such things as having a tone stack type circuit dialed in at low values (which, with some tone stacks, can reduce gain to almost nothing), not turning up your guitar or perhaps even running through pedals or effects that reduce gain via their operation or settings. All these things are possible before the issue is addressed. Also, I have no idea how savvy you are with understanding gain structures and concepts like headroom. You might be surprised how many players don't have a clue. So, for now, in your case, we'll ignore the possibility of operator error.

As I've said before, as someone who understands well enough the operation of tube circuits, the low HV on the power tubes isn't preventing overdrive or clipping. In fact it's more likely to have the opposite effect. Causing the amps to lack headroom. So we can ignore the slightly low HV as the cause.

That only leaves a peripheral equipment failure. So... Have you tried your guitar through a similar amp that is known to clip well for someone else? Or have you tried another guitar through these amps?

I suppose it's still possible that the design of both amps is so much lower in gain that they don't behave at all like a 5f1. Since that is the similar model referenced we don't have anything else to go by.

I'll say again, the slightly low voltage isn't part of the problem you're having. Regardless of whatever else you think of me you will do yourself a big favor if you trust me on this and move on to looking elsewhere for the solution.

Try the amps with another guitar. If possible, try your guitar with another similar amp.

A schematic would be ideal. How far these amps actually are from the referenced 5f1 could be a significant part of the problem.

I wouldn't simply put a boost pedal in front of the amps because the way I see it there IS a problem and that fixes nothing.

Submitted for your consideration by someone that's only trying to help.

[g1]

As Chuck suggested, trying your guitar (and guitar cable) through another (known good) amp should be the first step. It seems to be the only thing common to both set-ups.

[Sea Chief]

Hi Chuck-

I understand perfectly 'headroom' (I'd like to have relatively small ammount early break-up, in a fantasy world/ for eg the opposite to a twin reverb which has huge headroom). I understand the gain chain well enough, and I understand tube clipping to an extent. I don't need to be have lab tech knowledge of the intricacies as you guys do. Many many folks buy a simple Champ kit and build it with 1/2 the experience I have and it growls, as its expected to (Ive built hifi preamps and power supplies that are superb sounding and lasted 12 years without even a fault of any kind so I am experienced enough). I just want a bit of amp distortion, that's all. The more the merrier- that's why I built a small 5w amp1. (It didnt distort before I added the tone pot- as it was it was dark sounding with the sg, so I thougt at least make it useable albeit with a godam OD pedal Im forced to use- I hate OD pedals).

These are TWO different amps. Built by two different people. In two separate countries. They both work (there's no hum even- they're built well enough). I have gone over each with a toothpick to check/ check/ check again that each component is in its correct position, and value before firing up. I checked amp2 exactly the same before I switched on (as one would with an amp made by s'one else they haven't met). They turn on, they're nice and quiet, there's no hint of anything out of place- this is often immeduately eveident with a buzz or a crackle or sound not right. They sound fine, albeit clean up to 8.5. From 8.5 to 10 I get a tiny bit of distortion. With amp1 this is between 9 and 10. With an sg I expect it as you say, to growl. It may not be the sweetest NOS Mullard 6v6 growl, it may in fact be a crappyish sovtek 6v6 growl..... but this is far from the point of the exercise. If it growls at all I know I have a solid base to proceed from (a base which I expected to be at with maybe an hr here or there tinkering should a newbuild glitch need ironing out, like a wrong resistor or s'thing.. not 3 years of head-scratching and consternation); THEN I can proceed onwards, maybe start thinking about tube changing, researching a nice NOS rectifier perhaps.. all the things you guys take for granted. IE exactly as any new 5F1 builder might expect, whether a lab nerd or a newbie builder. But no growl at all? its like a ford escort rally car that goes fine but wont go over 80mph "well how are you driving it then? are you sure got the tyres inflated? are you sure you haven't got the handbrake on?".

Guitars.

I use a 2008 Gibson SG, and a cheapo squier strat I rewired with decent pickups. They sound as they should. I have a wem dominator too, and they sound as they should through this.

Every single facet/ every single component checked/ every single thing in the chain is as it should be/ there are no pedals involved (godalmighty- NO- this is the whole point of building amps to me in a way). The gtrs have not been modified with ridiculously low output pickups. The gtr vol is up, its 2nd vol is up, the tones are up. As is the strat/ all knobs full. The gibson sounds 1/3rd louder than the strat, as one would expect.

All is well. Apart from no distortion. If a 5F1 cant get into distortion with an sg something is amiss, whether or not Ive played through someone else's amp/ a shop's fender champ or not (I live in the country- nearest is london so its impossible to go play a real Champ- besides which shop lets anyone turn a 5w amp up to max anyway?). I know perfectly well what to expect with a 5F1 and an SG. Growl (of whatever quality dependent on the components). I get nothing- they're both like 5w Twins.

Thanks,Sea Chief.

[Jazz P Bass]

The only way to resolve this is with a proper bench test setup.

Signal generator, o scope & a dummy load.

[Sea Chief]

The only way to resolve this is with a proper bench test setup.

Signal generator, o scope & a dummy load.

Yes well most folks don't have access to one- most kit builds are aimed at non lab-rats.

Can you see though if 2 5F1's have all the stock 5F1 components, the right tube here/ the right resisitor there/ the right wiring/ the right heater V/ the OT wired in right/ the speaker right to match the OT secondaries/ the right pots, input jacks/ no shorts and checked.. but.. one difference only: the PT secondary voltage & by quite a margin in both cases to the stock value in the whole amp: can you see why I would go straight here 1st port of call?

If only I was sold amp2's PT (this is what I bought it for basically: I was told it was a 325-0-325v as Ive said but I have doubts about these figures) that I can verify IS 325-0-325v and not as I have a hunch maybe 270v, then I can rule out my theory as to these HV pair being the cause.

Can anyone pls remind me of testing the HV secondaries: as per spiel btm of #5 ?

Thanks for your input chaps. Sea Chief.

[Silvertone Jockey]

Just a thought, maybe it's the tubes you're using? Have you tested them?

[Jazz P Bass]

You don't need a distortion pedal for this.
What you want is a 'boost' pedal.
Something that will boost the signal enough to drive the amp into clipping.

This amp to me is not a holy grail anything.
It's a low powered practice amp.

If you want it to do more you have to give it more.

[Chuck H]

First video that pops up when you plug - sg 5f1 - into youtube

Gibson SG with 5F1 Tweed Champ - YouTube

You can see that this guy is plugged straight in. This is why I'm sayin' we could do a lot better with some schematics. If I had a 5f1 and it didn't get dirty with an SG I'd fix BEFORE plugging a boost pedal into it.

[Sea Chief]

Just a thought, maybe it's the tubes you're using? Have you tested them?

They're all new (the amp2's are only months old) & because of this persistant issue tbh I rarely play now, so amp1's tubes are as new as they were 5 years ago almost. I do occasionally try a switch tho- nothing changes, well a barely perceived sonic change if I swap in a 12aT7 for eg I forget in all of 3 minutes (or a 12ax7 back in for more gain? doesnt mean a thing- I dont get any gain at any level anyway).

Thanks SC.

[Sea Chief]

Exactly Chuck. Im not considering a boost pedal. I will consider this waaaaay later, if I do. IE once I get an amp I can use and sounds as it should. This YT clip is exactly how Id expect a Champ to sound with an SG, I dont think this one is even at vol 10 sounds more like vol 8 so many times Ive heard 5F1's on YT (in utter consternation, time after time after time- Im quite sick hearing anymore tbh. A world away from my clean "mini-twin" pair).

Im clutching at straws now.. but is there any way the house mains voltage could be not providing enough 230v for being a reason? nothing suggests anything wrong at all, lights dont dim/ fluctuate or anything. You see how defeated I am with this-?

Thanks, Chief