Phase Inverter Questions

[Structo]

I think that opinions change over time and also due to what is available.

Some guys stick with a brand for some reason, whether it is tone or availability or reliability, who knows?

But you can bet Leo or Jim never obsessed about them. They just bought what was available and cheap!
Because the bottom line is what motivated those companies.
I think Leo probably cared more about what the musicians thought of his gear as he was known to hang with the country swing guys.

But the reason for the high precision plate resistors such as the RN series, to me is getting it right on the value, then being able to depend on that component not to drift with age.

I was reminded of and maybe I had forgotten, that carbon film resistors can impart some goodness.
I don't know how much they drift with age but I may have to try them in the PI spot next time I order parts to see if there is indeed any m0jo in them.

I think if we took a few of the old Fender tweed or blackface amps that we thought sounded particularly good, disassembled them and measured each cap and resistor, we would probably be surprised how far from spec they had drifted.
So then what do you do to clone one? Do you use the values you measured or what the schematic states?

There seems to be a large mixture of voodoo and alchemy involved in getting an amp that astounds us tonally.

It's funny how much a bunch of tube heads can obsess about that last microfarad of tone we want to wring out of our amps.

Bottom line is, will the drunken fools at the next gig even care if your lead tone sounds like a silky, smooth saxophone or a Marshall in need of a re-tube?

[CHIP]

CHIP wrote:

What brands of metal film resistors are prefered? I once read to stay away from xicons.

Chip,

I asked this question about 18 months ago and at the time some senior members were anti Xicon MF's (e.g. glasman) and yet others had no problem with them (e.g. ayan), so one man's poison.....

There was a consensus that Koa Speer were quite highly regarded for their MF's, as were the NTE packaged MF's.

https://tubeamparchive.com/viewtopic.php?t=6090


Hope this helps.

Cheers,

Paul.

Thanks Paul.

[CHIP]

I think that opinions change over time and also due to what is available.

Some guys stick with a brand for some reason, whether it is tone or availability or reliability, who knows?

But you can bet Leo or Jim never obsessed about them. They just bought what was available and cheap!
Because the bottom line is what motivated those companies.
I think Leo probably cared more about what the musicians thought of his gear as he was known to hang with the country swing guys.

But the reason for the high precision plate resistors such as the RN series, to me is getting it right on the value, then being able to depend on that component not to drift with age.

I was reminded of and maybe I had forgotten, that carbon film resistors can impart some goodness.
I don't know how much they drift with age but I may have to try them in the PI spot next time I order parts to see if there is indeed any m0jo in them.

I think if we took a few of the old Fender tweed or blackface amps that we thought sounded particularly good, disassembled them and measured each cap and resistor, we would probably be surprised how far from spec they had drifted.
So then what do you do to clone one? Do you use the values you measured or what the schematic states?

There seems to be a large mixture of voodoo and alchemy involved in getting an amp that astounds us tonally.

It's funny how much a bunch of tube heads can obsess about that last microfarad of tone we want to wring out of our amps.

Bottom line is, will the drunken fools at the next gig even care if your lead tone sounds like a silky, smooth saxophone or a Marshall in need of a re-tube?

I have noticed with my D'lite that it seems to be smoothing out a little over time. But I also have changed alot of components over the last year, as I've read suggestions on this forum. One example was when I started it, I used mostly 715 orange drops. Then I changed them to the PS series. I still don't seem to have that type of tone I hear in some clips from Scott and Brandon. Right now it is one hell of a great sounding super charged Tweed Deluxe. I'm starting to wonder if going to an HRM 100 watt in my next build will get me closer to what I hear in some clips. I'll put it this way,SO FAR, the amp produces a great Billy Gibbons late 70's tone rather than a Robbin Ford tone

[kd]

I appreciate all the answers to my questions. I know it gets tedious answering questions from a newbie like me. I usually go all the way through an amp with carbon film resistors, but the clones I've built are mostly old Marshall and Fender circuits. This amp is a whole different animal and I want to stay close, component wise, to what the experienced builders are using. I'm attempting to get a good baseline amp before messing with any mods or changes.

Thanks again,
Ken

[Structo]

Hey Chip,

I have found the same thing with my amp.
It really does depend on your technique in how the amp sounds.

I'm an old rock n roller (53) and so my style is more towards the 70's rock, never was into metal much.
Love Ford and Carlton but they are so different from my technique of picking and phrasing that I just figure I will always sound like me whatever I play.

It would be neat to get that type of tone out of my amp but, it might also limit it to what I can cover.
All I know is I like the overdrive on my amp so no need for dirt pedals.
Occasionally I will throw a Sunface or GasPedal Si fuzz into the front end but for the most part I run clean or OD with delay, chorus and reverb in the loop.

If you haven't built one yet you should consider building a Dumbleator.
It really does improve things.
As I noted elsewhere, I had an Ironsounds FX loop in my amp before.
It sounded find at low volumes but I noticed as I turned the amp up and was pushing the preamp the Ironsounds just didn't sound very good at all.
It can only handle a 30v swing so it was most likely clipping the signal before the power amp.

But it's a lot of fun tweaking these amps. Sometimes it gets tedious and frustrating when you do one thing and it affects two other things but melting solder and hearing the differences is pretty cool as well.
It has been a great learning experience for me since when I was in school they didn't spend any time on tube theory because everybody knew tube products were obsolete! WRONG!

[CHIP]

Tom,
I agree with alot you said. I'll probably eventually get around to a dumblator.
I'm an old rocker too! I'll be 53 in March.

[Structo]

Heheheh, yeah I turned 53 on the Dec. 27.

[ChrisM]

Recently turned 18 and my hearing is already shot. I'll be damned if I can hear a change in sound as I turn the PI trimmer in my amps.

Personally I like unbalanced PI tubes. I find the tone to be a tiny bit harmonically richer.

[JD0x0]

Recently turned 18 and my hearing is already shot. I'll be damned if I can hear a change in sound as I turn the PI trimmer in my amps.

Personally I like unbalanced PI tubes. I find the tone to be a tiny bit harmonically richer.

im 18 too and my hearing is still decent AFAIK i can hear a bit higher than normal hearing range (23khz) but my ears arent great with the low frequencys luckily with bass, i can "hear" the lower frequencys with my body, ie feeling the vibrations.

ive been thinking about balanced PI tubes but there are too many mixed responses

[Structo]

Chris the change to listen for while adjusting the PI trimmer is kind of hard to explain.
I was told to use a single coil guitar, I used a strat set to the neck pickup, then turn up the amp quite loud and lightly brush the open strings with your thumb.
Slowly turn the trimmer while brushing the strings.

Remember it will lag a bit behind due to the caps, give a couple seconds for each adjustment you make.
When I did this the input side of the PI ( 100K on my amp) was a bout 6v higher than the feedback side.
When you hit the sweet spot, the amp is going to want to feed back with higher order harmonics.
The notes will bloom into the feedback.

You guys are lucky you are so young. You have all the time in the world to learn good tube theory here and in books.

And as an old fart, I can recommend that you protect your hearing the best you can.
I have permanent tinnitus. It's always there.
Plus high frequency loss.
I have worked in the construction field all of my adult life so a lot of damage has been a result of being around loud equipment.
Plus loud amplifiers.

I know when you are young, you tend to ignore passed down wisdom, he I was young once too!
But, if you are already experiencing hearing loss at 18, then what will it be like when you are 40-50 years old?

My grandson showed me something on his cell phone. There is a ring tone that is at a very high frequency that people over 30 or 40 cannot hear, but young people can.
They use this at school so the teacher can't hear their phone ring.
I held the thing right up to my ear and couldn't hear a thing but my grandson and granddaughter could.

[ChrisM]

Tom, that's more or less the method I was using when playing with the PI trimmer. In my last ODS the trimmer was 10K and I felt it did have "some" effect. In my 100W HRM I am building I am using a 25K. Hoping the wider sweep will make for a more noticeable adjustments. I have heard 25K will give "nicer mids" (forget where I read that).

My hearing is ok, not great, not close to as good as it was before I started playing guitar I'm always the guy who says "what, can ya say that again".

That cell phone trick was funny at the beginning. After so being in class so much and having people do it, it just got aggravating.

[kd]

When discussing the difference between voltages on each side of the phase inverter, are we talking the DC voltage or the AC voltage?

Ken

[ChrisM]

Talking DC.

Seems most guys want the to use the trimmer to get both the inverting side and non inverting side to have close to the same plate voltage.

[talbany]

When discussing the difference between voltages on each side of the phase inverter, are we talking the DC voltage or the AC voltage?

Ken

IMO The best way to set it is with your ears if you can.. Focus on the low's..Do it with the amp turned up 2X12's are more noticeable (Clean Channel).. There is a small lag time as you adjust so do small increments at a time..Good Luck!!

Tony

[angelodp]

I thought I would post this somewhat unconventional approach to the PI trimmer. Thanks to all for the suggestions and guidance. As it turned out the harmonic sweet spot, by ear, turned out to be a 6 volts spread w/ the high side on pin 1 .... so that was a nice surprise. Hope this might help any other Dliters that want to try this without re-drilling. I simply put in a slightly longer 4/40 screw at the main board and fashioned a daughter board that is supported there.

cheers Ange

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