Author Topic: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage  (Read 197984 times)

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frequencycentral

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I got a bunch of 5672 submini pentodes last summer, and have been busy designing uses for them. You may have seen the 'Pentadriver', 'Pentaboost' and 'Red Star Drive' threads.

I thought it was about time I tried an amp design, so here's "Murder One"



I need you guys help to finish it - to optimise it really. I've never built or designed a tube amp before. Obviously it's not ever going to be LOUD, but is at the moment comfortably loud enough for practice. So, without radically changing the design concept (which I don't want to do) what have I missed and what can I change for the better?

dwan

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #1 on: January 05, 2009, 04:31:28 PM »
Hello Rick

As a beginner, i would only replace all the caps with higher-rated ones, as a 8v margin is dangerously close to a surprise-blow-up-in-ya-face. The closer to their rating they are, the less they last. Unless you want to stick to a 12v main voltage, i would also go with more "elegant" way to get your voltages (transfo), as you're using the 1044 over its limits.

Very interesting tube builds nonetheless, i've ordered some 5672's last week to build and tweak my very own pentadriver  :icon_biggrin:

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #2 on: January 05, 2009, 05:18:14 PM »
Hello Rick

As a beginner, i would only replace all the caps with higher-rated ones, as a 8v margin is dangerously close to a surprise-blow-up-in-ya-face. The closer to their rating they are, the less they last. Unless you want to stick to a 12v main voltage, i would also go with more "elegant" way to get your voltages (transfo), as you're using the 1044 over its limits.

Very interesting tube builds nonetheless, i've ordered some 5672's last week to build and tweak my very own pentadriver  :icon_biggrin:

Yup, I'll have to get some 100 volt rated caps anyway, as I'm thinking maybe to try a few more stages with the MAX1044 to get up to about 80 volts. The volume increase with the incremental increases in the plate voltage is startling.

I really wanted to test this theory that a MAX1044 could power the plates of a tube amp - I was expecting sag, but there is no sag. I've never worked with high voltages, and I kinda want this amp to be accessible to everyone buildwise, so a power transformer is not an option. I just want to see how much mileage can be got out of this design concept without resorting to high voltage/power transformer.

Yeah yeah I know the MAX1044 is operating outside it's spec, I have 20 of them so I can afford to be a bit blase about it. IMHO they survive at 12 volts. To be honest, I wasn't even sure this concept would work out at all, now that it has I'll invest in some LT1054S (more ma, and rated for 12 volts) to replace the MAX1044. Alternatively, there's no reason why not to use a 9 volt supply instead of 12 volts.

Br4d13y

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #3 on: January 05, 2009, 06:27:48 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:
freedom is the freedom to say 2+2=4

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #4 on: January 05, 2009, 06:51:01 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:

I'm sure he'll be along when the Rome wine bars close.......... ;)

I forgot to put a cap in the schematic. It should go to ground from where those two 100R resistor connect by the transformer. I'm using a 33uf at the moment, I have no idea what value it should be, but Valve Wizard says there should be one there. It seems to work the same without though. Heyho, it's a 'work in progress' so i'll update the schematic as I go.

I'm running this into a 12" 8 ohm speaker by the way. I'm really pleased with the tone!

Anyone guess where I got the name "Murder One" from yet?

davent

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #5 on: January 05, 2009, 09:33:52 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:

I'm sure he'll be along when the Rome wine bars close.......... ;)

I forgot to put a cap in the schematic. It should go to ground from where those two 100R resistor connect by the transformer. I'm using a 33uf at the moment, I have no idea what value it should be, but Valve Wizard says there should be one there. It seems to work the same without though. Heyho, it's a 'work in progress' so i'll update the schematic as I go.

I'm running this into a 12" 8 ohm speaker by the way. I'm really pleased with the tone!

Anyone guess where I got the name "Murder One" from yet?
Hello,

I'll bite, every passive component is a 1 value multiplied or divided by 10 to the power of x.   A murder of crows is a group of crows so in your case you have a group of 1 valued components hence "Murder 1"

dave
« Last Edit: January 05, 2009, 11:02:18 PM by davent »
"If you always do what you always did- you always get what you always got." - Unknown

Br4d13y

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #6 on: January 05, 2009, 10:58:36 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:

I'm sure he'll be along when the Rome wine bars close.......... ;)

I forgot to put a cap in the schematic. It should go to ground from where those two 100R resistor connect by the transformer. I'm using a 33uf at the moment, I have no idea what value it should be, but Valve Wizard says there should be one there. It seems to work the same without though. Heyho, it's a 'work in progress' so i'll update the schematic as I go.

I'm running this into a 12" 8 ohm speaker by the way. I'm really pleased with the tone!

Anyone guess where I got the name "Murder One" from yet?
Hello,
I'l bite, every passive component is a 1 value multiplied or divided by 10 to the power of x.   A murder of crows is a group of crows so in your case you have a group of 1 valued components hence "Murder 1"

dave


Brilliant!!!!!!!!!!!!!
freedom is the freedom to say 2+2=4

anti-idiot

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #7 on: January 05, 2009, 11:44:20 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:

I'm sure he'll be along when the Rome wine bars close.......... ;)

I forgot to put a cap in the schematic. It should go to ground from where those two 100R resistor connect by the transformer. I'm using a 33uf at the moment, I have no idea what value it should be, but Valve Wizard says there should be one there. It seems to work the same without though. Heyho, it's a 'work in progress' so i'll update the schematic as I go.

I'm running this into a 12" 8 ohm speaker by the way. I'm really pleased with the tone!

Anyone guess where I got the name "Murder One" from yet?
Hello,

I'll bite, every passive component is a 1 value multiplied or divided by 10 to the power of x.   A murder of crows is a group of crows so in your case you have a group of 1 valued components hence "Murder 1"

dave

i was about to say "because you're fan of Lemmy Kilmister", but that "value of one" thingy makes more sense.

("Murder One" is the name of Lemmy's modded Marshall bass amp)
If I was God you'd sell your soul to...

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #8 on: January 06, 2009, 01:27:02 AM »
I'll bite, every passive component is a 1 value multiplied or divided by 10 to the power of x.   A murder of crows is a group of crows so in your case you have a group of 1 valued components hence "Murder 1"

Very nice! But.................

i was about to say "because you're fan of Lemmy Kilmister", but that "value of one" thingy makes more sense.

("Murder One" is the name of Lemmy's modded Marshall bass amp)

Winner! I am a longtime fan of popular Brit beat combo Motorhead. My amp is about as loud as a wart on Lemmy's chin.

~arph

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #9 on: January 06, 2009, 03:32:01 AM »
Have you tried the BJT trick at the plates to get more output? or doesn't that work with a charge pump.

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #10 on: January 06, 2009, 01:32:09 PM »
Have you tried the BJT trick at the plates to get more output? or doesn't that work with a charge pump.

I haven't tried that - the BJT would have to be rated suitably for the B+ voltage though. I think it's not a route I will take anyway - applying it to the first stage (preamp) would just overdrive the second stage (power amp), and I would rather keep it clean and add overdrive via a pedal. There is no point in appling it to the second stage anyway, as the transformer is directly connected to B+.

I think I've pretty much decided to add some more voltage increase stages to the MAX1044 and see how much more power I can get. The 5672 maximum rating is 90 volts, at the moment I'm running at half of that.

The sound is that of a cranked up tube amp, but without upsetting the neighbours/causing plaster to fall from the ceiling.

anti-idiot

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #11 on: January 06, 2009, 01:40:24 PM »
I'll bite, every passive component is a 1 value multiplied or divided by 10 to the power of x.   A murder of crows is a group of crows so in your case you have a group of 1 valued components hence "Murder 1"

Very nice! But.................

i was about to say "because you're fan of Lemmy Kilmister", but that "value of one" thingy makes more sense.

("Murder One" is the name of Lemmy's modded Marshall bass amp)

Winner! I am a longtime fan of popular Brit beat combo Motorhead. My amp is about as loud as a wart on Lemmy's chin.

Lemmy's the man. But I bet your amp wouldn't survive a nuclear bombing. Lemmy (and Keith) would. He has more chemicals in his body than most of the stuff we use to make pedals.
If I was God you'd sell your soul to...

svstee

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #12 on: January 06, 2009, 02:40:56 PM »
Looking quite nice!

Have you given any thought to the possibility of a tonestack?

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #13 on: January 06, 2009, 02:46:07 PM »
Looking quite nice!

Have you given any thought to the possibility of a tonestack?

Maybe. I'll see how much volume I have once I've added a few more voltage increase stages. Tonestacks always cause volume loss.  :icon_cry:

Renegadrian

"Murder One" - Submini Pentode, Low Voltage
« Reply #14 on: January 06, 2009, 07:08:03 PM »
( silently waiting for adriano to come around witha vero board.....) :icon_mrgreen: :icon_mrgreen:

I'm sure he'll be along when the Rome wine bars close.......... ;)

You men made me laugh!!! eheheh You really figure me like this?! --->
ok maybe I'm like this sometimes...I had new year's eve in tuscany, go figure...

Back IT and being serious (one time) - I'll work at it in the next days!!! THX Rick for another funny tube project!!!



that transformer is about 15$...Are there any cheaper subs?! Radio shak or something?
« Last Edit: January 06, 2009, 07:16:05 PM by Renegadrian »
Done an' workin'=Too many to mention - Tube addict!

frequencycentral

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Re: "Murder One" - Submini Pentode, Low Voltage
« Reply #15 on: January 06, 2009, 07:24:09 PM »
that transformer is about 15$...Are there any cheaper subs?! Radio shak or something?

Mine is a clone with the same spec from an ebayer in Portugal - cheaper than having a fender shipped from USA - just do a search for 'fender reverb transformer'. The genuine Fender part is a little prettier though.

Renegadrian

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #16 on: January 06, 2009, 07:39:13 PM »
Found THIS ONE but it's not that cheaper, I guess I have to search for it better...
Done an' workin'=Too many to mention - Tube addict!

chillhuman

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #17 on: January 06, 2009, 07:58:33 PM »
My amp is about as loud as a wart on Lemmy's chin.
What speaker do you have plugged in? If you wire up something really efficient, you'd be AMAZED at how loud even 1W can be.

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #18 on: January 07, 2009, 11:19:07 AM »
My amp is about as loud as a wart on Lemmy's chin.
What speaker do you have plugged in? If you wire up something really efficient, you'd be AMAZED at how loud even 1W can be.

I'm running it into the 12" speaker of my Roland Bolt 60 tube combo, the speaker is not labelled, but is pretty good.

I got the voltage up to 60 volts last night by adding a couple more stages to the MAX1044, so I got another volume increase - nice! But I've run out of suitable caps to go all the way to 90 volts, I'll pick some up very soon.

I have decided to add two Si diodes between the 12 volt supply and the MAX1044's input to limit the voltage going into the MAX1044 to 10.6 volts, which is just a smidge above it's spec. Better safe than sorry.

I'm also planning to try Ge diodes in the voltage doubling matrix, as they have lower voltage drop that Si - and I have hundreds of them. R.G's Geofex article about the MAX1044 suggests zeners for even less losses - I don't have many, so I'll go with Ge and try to get as close to 90 volts (the 5672's maximum spec) as I can. I think I'll end up with eight stages of voltage increase, so 16 diodes and 16 caps.

Ripthorn

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #19 on: January 07, 2009, 12:40:50 PM »
I almost wonder if you would be better of with a power transformer to supply B+, because the 317 can handle up to 60V in if I remember right.  Seems that if you had a higher input voltage (even without a dedicated power transformer) you could still get your 1.5V with the 317 but reduce the number of components.  I don't know, just seems like if you stack up 16 stages, that would be rather space consuming.  Just a thought.  Maybe you could even make it phantom powered (though I am not sure a phantom supply would provide enough current).  Are you thinking of supplying the 12VDC with a power supply or batteries or what?
Exact science is not an exact science