Express and Liverpool Fizz

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

Well, I finally got around to installing the 6PS caps in these amps. While the fizz is not completely eliminated, I seem to think that they helped quite a bit.

I think that when turning up gain that high in any amp, there will be a certain amount of that sizzle. I just tried in my DC30 clone. I think it's just that we normally never dial up that much gain on nonMV amps...
I found the easiest way to find the sizzle is to pluck the low E string and then a high B or E string around the 12th fret. This was when I could often get more sizzle than note.

But again, I still need to do more extensive testing, but I think the 6PS caps really reduced the prominence of this sizzle.... would I swear tis under oath? Probably not. This is the type of thing with too many variables, but doing the Express first, I played them both and found the Liverpool much worse, and now that both have the 6PS caps, they are closer again... I think.

I was given an old Bogen PA amp because I'm the "nut that likes these sorts of weird old things", and I found what I believe to be some smooth-plate Telefunken 12ax7s in it. Most of the writing is rubbed off except for a "made in Germany" on one of them. They have the diamond on the base though, and look vastly different than all my modern 12ax7s. We'll see if these amps like any of them.
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Roe
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Re: Express and Liverpool Fizz

Post by Roe »

for me the BC vishay 450v filter caps helped.
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Turbojunkie
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Re: Express and Liverpool Fizz

Post by Turbojunkie »

Diamond on the bottom, pronounced seams on the top, and printed logos that rub off if you breathe on them.....Nice Score!!! On top of being great sounding tubes, they're so well built that they last forever. Killer tube for the phase inverter in Express/Liverpools, and I like them in any position in a Rocket. Try to gently get the corrosion off the pins, clean 'em up a bit with some DeOxit and very-fine grit sandpaper without bending them at all...
andresound
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Re: Express and Liverpool Fizz

Post by andresound »

Common denominator is the speaker. My 2c worth
If it sounds good, it is good! Trust your ears
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

Turbojunkie wrote:Diamond on the bottom, pronounced seams on the top, and printed logos that rub off if you breathe on them.....Nice Score!!! On top of being great sounding tubes, they're so well built that they last forever. Killer tube for the phase inverter in Express/Liverpools, and I like them in any position in a Rocket. Try to gently get the corrosion off the pins, clean 'em up a bit with some DeOxit and very-fine grit sandpaper without bending them at all...
Thanks! Will do!
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

andresound wrote:Common denominator is the speaker. My 2c worth
No, I've tried these amps through quite a list of speakers. I've gravitated to the few types that minimize the fizz... but I still play them through the different types in my other cabs from time to time. I wish it was just the speakers.
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67plexi
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Re: Express and Liverpool Fizz

Post by 67plexi »

Ken used Stackpole resistors not Xicon Taiwan garbage.
It's that simple.
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Littlewyan
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Re: Express and Liverpool Fizz

Post by Littlewyan »

I'm sure I used Xicon resistors and my amp sounds great. No fizz at all.
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

hmmmm. I guess I'd be willing to upgrade the resisters at some point. If I'm going crazy. I might as well go crazy.

Does that mean that I should be replacing the Bournes pots with something special there too?
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

rooster wrote: Thu Apr 21, 2016 6:34 am One thing in particular that came up for me was the diode strings on the power tubes. I was hearing a fizz and I disconnected them: fizz gone. I know these are a Ken thing and they are in the originals but I don't use them anymore. I suggest you try disconnecting one end on each of them and see what you end up with. If it sounds the same, reconnect the disconnected ends and move on.
I decided to really focus on the fizz again specifically on my Express because I modded my Liverpool a bit and it is not really a factor with that amp.
I tried removing the diode strings and that didn't fix the problem. I was hoping that was it, because the description sounded the same with people finding that as the problem.

1) Different tubes really made no difference. (pre and power)
2) Different caps has not resolved anything. Been through 716s, M150s, and 6PS. 6PS minimizes it the most, but I think that is mostly because they darken the tone them most?
3) I've played a bit with NFB and presence and perhaps it got a lot worse (so next I will try completely removing the NFB wire to see if that was causing the noise).
4) Chopsticking has really returned no results. I find this has more to do with the amp being quiet rather than this sizzling ruining the distortion tones. I currently am using cloth covered solid core wire. I could switch to stranded to try more extreme relocation without the high risk of breaking these wires. Then I would likely have to go the glue gun route to secure them.
5) After playing with the NFB, I will try completely removing the VVR2 from the circuit. Even though having the control cranked is supposed to essentially take it out of the circuit, there is a chance the location just introduced some sort of interference, or a component is malfunctioning. I'm trying to remember if this is a similar sound to when my 2204 fried a VVR.
6) If the VVR, NFB, and Extreme chopsticking don't help, I think the next thing would be to order all new resisters and Filter Caps. There are some recommended high quality Metal Films some guys are trying?
strelok
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Re: Express and Liverpool Fizz

Post by strelok »

I know your pain. Back when I had my SE express I had this maddening fizzy oscillation sound sitting on top of the notes. In a recent thread I described my conversion of said amp into a PP with a pair of 6v6's. I thought at first that it had eliminated the fizz but upon making sound clips I found that it was still there. In my case I'm in a pretty small room and the amp is just so damn bright and loud its hard to hear it in person. Also it just sounded so much better as a PP amp that I think I probably was overlooking it. But alas it remains. This is despite the fact that I'm using a completely different pre-amp layout, more akin to a traditional express.

Before you go too crazy though, I'd like to offer some advice because I know how frustrating of a problem it can be. I think this problem is something just inherent to the circuit and I think that the goal is minimizing it down to acceptable levels. I've spent the past several weeks analyzing various sound clips of express's and I think they all do it to one extent or another, even the real ones. It drove me crazy for the longest time with the SE version of this amp because it sounded a bit different from a normal express. But now that I have something a bit closer to the actual circuit, I have a better way of referencing to other sound clips. Take a listen to this clip Glen posted a while back https://www.youtube.com/watch?v=O05EM1JVSxM To me its the best sounding clip of an express I've ever heard, and IMO some of the best tone ever recorded. Assuming we're talking about the same issue, I can hear the same fizz that sits on top of the notes that is present in my amp. Its just A LOT less present than in my amp. Also that amp sounds significantly better than my build does by miles, so its easy for me to get distracted by the rest of it and overlook the issue I'm searching for a solution to.

So I'd like to offer the following advice before you go tearing your hair out trying all new resistors filter caps etc. Because I've definitely been there. First of all, disregard any sound clips that have backing tracks or any other instruments or effects present in the mix for reference purposes. I find that its pretty much impossible to hear the fizz when there is drums, bass and what not is going on in the mix.

Second don't forget the fact that almost everyone on here seems to think that these amps tend to mellow out with age. Glenn is using an amp that's 30 years old. He's also running through a 1968 Marshall cabinet with I believe its original speakers in it. So they've also had nearly 50 years to mellow out. He also has some fantastic recording gear. Royer ribbon mics, Neve preamps. He's also blending in some room tone in that clip with a mic outside the recording booth. Then for any sound clip there is the mystery factor. What's getting done in post? I find that I can EQ out a lot of the fizz by using a low pass shelf filter that starts to roll off around 6-8khz. The clip I posted recently has just that done to it since I just absolutely hate that fizz. I also added some reverb. I think that helps with it as well.

Now with all that out of the way what can you actually do to the circuit to change the results you're getting. First I think the 6ps caps are a step in the right direction. I have 715's in mine currently and the amp is just waaayy bright. I ended up increasing the value of the PI Plate Cap to 500pf. This seemed to help some, so you may give different values there a try. My amp is bright enough that I haven't even bothered with the bright cap yet. I have a set of 6ps on order, after reading your thread I'm going to give them a try if only to tame the treble a bit. The more I think about it though, the one thing I really keep coming back to is grid stoppers. The complete lack of them in this amp seems to be partly responsible for its over the top nature and awesome touch response. But I think it also makes it much more likely to run into these sorts of problems. I plan on experimenting with these after I get the caps installed. The second and third gain stage is where you want to try them. You can put them before or after the grid leaks/volume pot. If you put them before they will reduce the gain levels as well as roll off high frequency response. Low values you probably won't be able to hear that effect, higher values you will. If you put them after it will won't really affect the gain, just HF response. You could start with something high like 100k or 220k, on one or both stages. You could even go as high as 500k if you wanted too. See if that helps any. It will affect the sound so its a matter of compromise. Assuming it helps tweak the values to reach a point that you're happy between the levels of fizz and what you lose from the express's character by adding the resistors in.

I hope this helps and sorry for the wall of text. Also keep in mind that Ken was an absolute madman when it came to tweaking these amps. Supposedly he would spend months adjusting things here and there, and finding the perfect set of tubes for that particular amp. I think unless you really enjoy doing that sorta thing and have the time/energy for it at a certain point you have to be happy with what you got. Ken did this as a full time job, I do this on the side with much less time and energy available, so its just something to keep in mind. Additionally when the obsession really start to kick in, I find I have to back away from it for a few weeks or a month. If I get to far into it eventually the fizz is all I hear. It starts to get like Moby Dick or something lol. Then I come back to it later on and its more honest I think. I hear an amp that's like oh hey this a nice sounding amp with a minor problem as opposed to my obsession mode where its like fuck this piece of shit its nothing but terrible fizz I'm never playing it again. :lol: :lol:

Also what are your coupling cap values? Larger values will let more bass through which means the output section has less energy for high frequencies. I had a .022 going to the PI and going to .1 was a big improvement in general brightness levels, might help you tame the fizz as well. Could try .1s in the output coupling as well if you haven't already.
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

Thanks for your reply Strelok. Sorry about my late reply, but Moby Dick is right and I needed a bit of break from it. I had done the stage 3 split plate, with no NFB and a cut control. These types of things worked great on my Liverpool to make it more of a great pedalboard amp, but I do need want a convincingly "real-sounding" Express... especially in light of Glen's SG video that you linked. THAT is the perfect tone! I have brought home my cab with M65 Creambacks just to makes thing a little more fair (modern greenbacks are just accentuating the fizz- which may be helpful for hunting it down-- but also hopeless results-wise).
strelok wrote: Sat May 06, 2017 10:55 pm Now with all that out of the way what can you actually do to the circuit to change the results you're getting. First I think the 6ps caps are a step in the right direction. I have 715's in mine currently and the amp is just waaayy bright. I ended up increasing the value of the PI Plate Cap to 500pf. This seemed to help some, so you may give different values there a try.
I'll try playing with that cap right after I get this Express back to stock. I currently have a 47pF in there.
strelok wrote: Sat May 06, 2017 10:55 pm The more I think about it though, the one thing I really keep coming back to is grid stoppers. The complete lack of them in this amp seems to be partly responsible for its over the top nature and awesome touch response. But I think it also makes it much more likely to run into these sorts of problems. I plan on experimenting with these after I get the caps installed. The second and third gain stage is where you want to try them. You can put them before or after the grid leaks/volume pot. If you put them before they will reduce the gain levels as well as roll off high frequency response. Low values you probably won't be able to hear that effect, higher values you will. If you put them after it will won't really affect the gain, just HF response. You could start with something high like 100k or 220k, on one or both stages. You could even go as high as 500k if you wanted too. See if that helps any. It will affect the sound so its a matter of compromise. Assuming it helps tweak the values to reach a point that you're happy between the levels of fizz and what you lose from the express's character by adding the resistors in.
I have put a 33k in front of the 1st grid and an 820R in front of the second grid. I did not actually notice real difference, but they are still in. I did previously play with a grid leak/ grid stopper resisters on the 3rd gain stage that like Martin Manning's Express that uses a trimpot to maintain 150K to ground from the previous stage's plate-->cap. It just varies the grid stopper/leak on a sliding scale between 0K/150K to 100K/50K. I tried some sort of fixed resisters before, but will re-investigate this.
strelok wrote: Sat May 06, 2017 10:55 pm Also what are your coupling cap values? Larger values will let more bass through which means the output section has less energy for high frequencies. I had a .022 going to the PI and going to .1 was a big improvement in general brightness levels, might help you tame the fizz as well. Could try .1s in the output coupling as well if you haven't already.
I currently have 0.022uF PI coupling caps... I will definitely try increasing those too. Thanks! I don't think I have tried that yet.

After trying your suggestions, I will try not to despair by keeping in mind I can pour over these different Express variations to try other circuit alterations:
http://ampgarage.com/forum/files/wreckxpr.pdf
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bcmatt
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Re: Express and Liverpool Fizz

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Well, I think that eliminated the fizz down to reasonable and expected subtle levels. I left the stage 1 and 2 grid stoppers but went back to the stock Express circuit otherwise. I routed the NFB (yellow cloth covered wire) further from the VVR circuit this time as well (so that may have helped).
I also moved to 0.1uF PI coupling caps (from 0.022) before starting it up. I should mention that I have kept the 500K Gibson Historic Pot for the Volume in series with a 470K resister. It keeps the circuit looking the same though.. it's just easier to fine tune the gain in the usable areas.
oh ya, I guess I never changed that 100K resister in the PI back to the stock 82K either...

It seems to not have that unbearable fizz to nearly the same degree. I even plugged it into the greenbacks to see if it was all creambacks fixing it... and it wasn't....they smooth the sound, but the circuit has improved as well.

Unfortunately, I didn't get to play it tonnes at decent volume and I am out of town for a week now, but needless to say, I am quite pleased because I think this was a major step forward. I don't know if I have ever had my Express this smooth at high gain.

I guess I'll have to compare it to that clip of Glen's again now... but that could be a bad idea for this old Captain Ahab...
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strelok
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Re: Express and Liverpool Fizz

Post by strelok »

I'm glad to hear that you're making progress. Its encouraging me to get back to mine and install the polyester caps. Just been busy with other projects at the moment. I'm also waiting to buy another audio interface so I can setup a semi permanent setup at the shop to do recordings and make comparisons with. Full tilt the amp is just too loud in the room for me to really even hear the fizz and my ears get fatigued quite quickly so I have to wear hearing protection which of course makes it even harder to hear.

One thing I will add is this. I've got a metro 100w kit that I built many years ago. Its the 68 spec with the lower filter values. When that amp is dimed it has a decent amount of ghosting to it. Just the nature of the low filtering, but I prefer the looser sound. However when I use it with my hotplate the more I attenuate the signal the more obvious the ghosting becomes for whatever reason. So that is something to also keep in mind if you're using an attenuator. It may make certain flaws with the amp more obvious than they normally would be for whatever reason. I'm not sure why this is but it definitely seems to be the case and I suspect it would probably be true of your situation with the fizz as well.
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bcmatt
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Re: Express and Liverpool Fizz

Post by bcmatt »

strelok wrote: Thu May 18, 2017 6:03 pm I'm glad to hear that you're making progress. Its encouraging me to get back to mine and install the polyester caps. Just been busy with other projects at the moment. I'm also waiting to buy another audio interface so I can setup a semi permanent setup at the shop to do recordings and make comparisons with. Full tilt the amp is just too loud in the room for me to really even hear the fizz and my ears get fatigued quite quickly so I have to wear hearing protection which of course makes it even harder to hear.

One thing I will add is this. I've got a metro 100w kit that I built many years ago. Its the 68 spec with the lower filter values. When that amp is dimed it has a decent amount of ghosting to it. Just the nature of the low filtering, but I prefer the looser sound. However when I use it with my hotplate the more I attenuate the signal the more obvious the ghosting becomes for whatever reason. So that is something to also keep in mind if you're using an attenuator. It may make certain flaws with the amp more obvious than they normally would be for whatever reason. I'm not sure why this is but it definitely seems to be the case and I suspect it would probably be true of your situation with the fizz as well.
I think you are right on that one. I was finding that fizziness was common to using VVR or the Unleash. I seem to recall that the fizziness doesn't increase to the same degree as the tone volume of guitar as you allow these things to open up more. But realistically, I have to use some sort of attenuation. Maybe my next project will be an isolation cab for live use...
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