My Liverpool Experiment
Moderators: pompeiisneaks, Colossal
My Liverpool Experiment
I wanted to share this build and progress so far. I was going to build a straight up Liverpool but decided to experiment some. This build has the Liverpool power section along with another Ken Fischer inspired preamp,the one with the split plate resistors.
So far i'm pretty happy the way it came out but I'm having 1 issue. This thing is running HOT with the 130 ohm bias resistors. If I did my math and measurements correctly its running 25 Watts dissipation!!!
I have a 160, 180, and 200 on the way to try out in hopes it will settle things down.
I'd love to hear your feedback and suggestions!
So far i'm pretty happy the way it came out but I'm having 1 issue. This thing is running HOT with the 130 ohm bias resistors. If I did my math and measurements correctly its running 25 Watts dissipation!!!
I have a 160, 180, and 200 on the way to try out in hopes it will settle things down.
I'd love to hear your feedback and suggestions!
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Re: My Liverpool Experiment
The images didn't come though from my google drive. Here are the links:
Guts:
https://drive.google.com/open?id=1QA2ru ... 6GG_Cci324
https://drive.google.com/open?id=17mfu4 ... hAcx05zIfk
Front:
https://drive.google.com/open?id=1wpq0V ... s6Yk6TLuWX
Rear:
https://drive.google.com/open?id=14DXPd ... iLwpFQDcw5
Layout:
https://drive.google.com/open?id=1zsM7O ... vP44_c7TFJ
Schematic:
https://drive.google.com/file/d/1gfwbKZ ... Z0EGj/view
Voltage Chart:
https://drive.google.com/open?id=1Ut5YO ... 95dfA-sXS6
Bias:
https://drive.google.com/open?id=1QI23R ... hLzGNPBqHv
Guts:
https://drive.google.com/open?id=1QA2ru ... 6GG_Cci324
https://drive.google.com/open?id=17mfu4 ... hAcx05zIfk
Front:
https://drive.google.com/open?id=1wpq0V ... s6Yk6TLuWX
Rear:
https://drive.google.com/open?id=14DXPd ... iLwpFQDcw5
Layout:
https://drive.google.com/open?id=1zsM7O ... vP44_c7TFJ
Schematic:
https://drive.google.com/file/d/1gfwbKZ ... Z0EGj/view
Voltage Chart:
https://drive.google.com/open?id=1Ut5YO ... 95dfA-sXS6
Bias:
https://drive.google.com/open?id=1QI23R ... hLzGNPBqHv
Re: My Liverpool Experiment
I'd imagine with the higher rail voltage that the valves would exceed their 12 watt rating. I don't think the 130 ohm resistors will do much to lower the current. The 1K resistors on the screen grids should help the valves once the signal is applied.
How did you come to the figure of 25 watts dissipation?
How did you come to the figure of 25 watts dissipation?
Yours Sincerely
Mark Abbott
Mark Abbott
Re: My Liverpool Experiment
These are the numbers and math I used. Its very possible I messed this up:
V4
Resistance CT to Plate = 47.5 ohms
Voltage Drop = 3.6
Plate Current V/R = 3.6/47.5 = 0.0757
Plate Voltage 328
Plate Voltage * Plate Current = 328 x 0.0757 = 24.8296
On the links above the "bias" one is my calculations for v4, v5, v6, and v7.
V4
Resistance CT to Plate = 47.5 ohms
Voltage Drop = 3.6
Plate Current V/R = 3.6/47.5 = 0.0757
Plate Voltage 328
Plate Voltage * Plate Current = 328 x 0.0757 = 24.8296
On the links above the "bias" one is my calculations for v4, v5, v6, and v7.
Re: My Liverpool Experiment
The voltage you should use is the voltage between plate and cathode (328-11.1=316.9) And 316.1 x 0.0757 = 24 watts. That's a little lower. But that power is shared by V4 and V5, so if you assume the power splits equally then each tube is idling at 12 watts. That means the tubes are biased at 100% max plate dissipation and that's quite normal for a cathode biased amp. I'd say you are right on target.
I personally like to use 150Ω cathode resistors just to run the tubes a bit cooler. Doesn't really make much difference but it just gives me a better feeling.
I personally like to use 150Ω cathode resistors just to run the tubes a bit cooler. Doesn't really make much difference but it just gives me a better feeling.
Re: My Liverpool Experiment
Ah thanks...I knew i was forgetting something. I''m still going to bump the cathode resistor up some to cool them off a bit.
Here is a quick demo, dont mind the crappy playing.
https://youtu.be/4aKgYKpJ50I
[youtube]https://youtu.be/4aKgYKpJ50I[/youtube]
Here is a quick demo, dont mind the crappy playing.
https://youtu.be/4aKgYKpJ50I
[youtube]https://youtu.be/4aKgYKpJ50I[/youtube]
- pompeiisneaks
- Site Admin
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- Location: Washington State, USA
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Re: My Liverpool Experiment
Sounds great! To use the youtube button here, you need to just use the part after the / or the = depending on the url type, yours is:
4aKgYKpJ50I
So I'd wrap that with those tags to get:
Removing some spaces to make it 'not' work gets teh same idea:
[ youtube ]4aKgYKpJ50I [/ youtube ]
You'd want to remove those spaces and have none, just aded them so it's more obvious what I did.
~Phil
4aKgYKpJ50I
So I'd wrap that with those tags to get:
Removing some spaces to make it 'not' work gets teh same idea:
[ youtube ]4aKgYKpJ50I [/ youtube ]
You'd want to remove those spaces and have none, just aded them so it's more obvious what I did.
~Phil
tUber Nerd!
Re: My Liverpool Experiment
Thanks Phil. As you can see I was struggling with the youtube tag...lol
Re: My Liverpool Experiment
With your voltages try 180R - 220R cathode resistor. You can it biased at about 85% at idle. EDITED: 180R - 220R cathode resistor PER PAIR.
And you will like what you hear
And you will like what you hear
Last edited by Vince on Mon Nov 13, 2017 6:00 am, edited 1 time in total.
Re: My Liverpool Experiment
This is pretty much the same thing I found with my Rocket. A single 100 ohm resistor would put it in class A/B, there are AC-30's out there that use 80 ohm resistors. So I wouldn't get too hung up on resistor values.
Yours Sincerely
Mark Abbott
Mark Abbott
Re: My Liverpool Experiment
No more class A EL84 with B+ voltages over 280-300V.
AC30, TW, all DR Z, Matchless, BadCat amps all are class AB amps with silly overbiased EL84.
"Class A" marketing hype on these tube eaters
AC30, TW, all DR Z, Matchless, BadCat amps all are class AB amps with silly overbiased EL84.
"Class A" marketing hype on these tube eaters
Re: My Liverpool Experiment
Thanks guys. At higher gain settings it can be fizzy sounding. Someone on a different described the sound i'm hearing perfect, it sounds like the fizz is sitting "on top" of the notes. Do you guys think bringing it down to 70-80% idle will help? It could be the speakers too, I'm currently running it through a 2x12 closed back Mesa Boogie Rectifier cab loaded with vintage 30's. I'm looking to get an avatar single 12 so i can play around with some different speaker too.
Re: My Liverpool Experiment
Yes, higher cathode resistor get out some "shattered glass" from tone.
Sound will be warmer and rounder - simply try it.
I edit my previous post:
EDITED: 180R - 220R cathode resistor PER PAIR
Sound will be warmer and rounder - simply try it.
I edit my previous post:
EDITED: 180R - 220R cathode resistor PER PAIR
Re: My Liverpool Experiment
I already have some different values on the way to play around with...lol I'm hoping they will be here early this week.
- norburybrook
- Posts: 3290
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Re: My Liverpool Experiment
try it through a pair of Alnico speakers.
For me it's the perfect choice for a rocket, it sort of smooth's out the high end and also gives some speaker break up too. think of the original AC30...2x12 blue alnico speakers.
the Z wreck matching cab is a 2x12 gold and blue celestion alnico.
for me they soften the sound very nicely.
MC
For me it's the perfect choice for a rocket, it sort of smooth's out the high end and also gives some speaker break up too. think of the original AC30...2x12 blue alnico speakers.
the Z wreck matching cab is a 2x12 gold and blue celestion alnico.
for me they soften the sound very nicely.
MC