Author Topic: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage  (Read 252496 times)

bbmonster

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #200 on: August 04, 2009, 07:01:40 AM »
A question on the bias mod. Is it possible to stick a switch to get back to your original design? Could I just stick an SPST to disconnect the bias or would I need a DPDT to bypass the .1 capacitor after the volume pot along with disconnecting the bias connection? I would try this out but currently using the board to mount the standoffs in the enclosure so unable cut the connections and experiment right now till the epoxy hardens.

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #201 on: August 04, 2009, 01:38:36 PM »
A question on the bias mod. Is it possible to stick a switch to get back to your original design? Could I just stick an SPST to disconnect the bias or would I need a DPDT to bypass the .1 capacitor after the volume pot along with disconnecting the bias connection? I would try this out but currently using the board to mount the standoffs in the enclosure so unable cut the connections and experiment right now till the epoxy hardens.

Should be fine to do that. You can just use a SPST to disconnect the negative bias, as the volume pot would then become the bias. I don't think you would need to bypass the 0.1 cap. I did that on the breadboard yesterday and it seemed ok to me.
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bbmonster

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #202 on: August 07, 2009, 06:28:39 PM »
Wondering if you could help with a slight problem I have. I added the SPST switch to cut off the bias mod to get back to your original design for a more distorted sound. The problem I am having is that when I cut the bias, sound is good for a bit then starts to get really flubbery (or gated is probably the better term) after a few seconds when strumming chords. If I rest a bit, then the chords sound good again for a bit before flubbery again.  When I have the bias on, no problems at all, sounds awesome. Any suggestions that I could do?

Thanks.
-Bernard

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #203 on: August 08, 2009, 07:12:56 AM »
Ok, I think whats happening is that the grid is basically unbiased then, because the cap between the volume and the grid is blocking the volume from biasing the grid. So maybe you need to either bypass the cap when ground biasing (as you suggested earlier), or use a DPDT instead of an SPST with the second pole referenced to ground via a 1M resistor. Hey - I'm glad you think it sounds awesome though!
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bbmonster

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #204 on: August 09, 2009, 05:49:43 PM »
Thanks, bypassing the cap did the trick.
-Bernard

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #205 on: August 09, 2009, 06:13:33 PM »
Could I just stick an SPST to disconnect the bias or would I need a DPDT to bypass the .1 capacitor after the volume pot along with disconnecting the bias connection?

Thanks, bypassing the cap did the trick.
-Bernard

You were right then! How are you finding the two different modes now?



EDIT: If anyone want's a frequencycentral prototype, the original Murder One is for sale: http://www.diystompboxes.com/smfforum/index.php?topic=78320.0
« Last Edit: August 09, 2009, 06:49:41 PM by frequencycentral »
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bbmonster

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #206 on: August 09, 2009, 08:28:26 PM »
I'm liking it. It's like how you mentioned before, the bias provides a cleaner sound and the original a more dirty sound. There is enough difference that I'm keeping the switch on.

I was just guessing on bypassing the cap, I have very little understanding of tube amps right now. I'm more of have little understanding of it, build it for even more understanding, if the build doesn't work is even better because you can learn more kind of guy.

Thanks again. I look forward to attempting more of your projects in the future.
-Bernard

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #207 on: August 09, 2009, 08:36:17 PM »
Interesting. I originally saw the grid bias mod as an improvement which superceded the original, but now it seems it should really be a stock switchable option. Maybe I should modify the schematic to that effect.
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Taylor

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #208 on: August 09, 2009, 09:15:39 PM »
Could anyone compare the sound of this amp to something like a Valve Junior? I have a 100w tube amp (I play bass) but I'd like something I can get to distort at lower volumes. Was thinking about getting a VJ, but if I can build something (without having to fool with high voltage) that would be better. Of course, I realize this amp will have less volume than VJ.

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #209 on: August 09, 2009, 09:22:25 PM »
I have a VJ. Wouldn't dare max it at home. I have the volume set at 10 o'clock generally, with pedals providing the dirt. Murder One is comparable at it's maximum volume, a bit more if you push it with pedals. But "Superfly" with a BM pushing it is anti-social.
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Renegadrian

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #210 on: September 25, 2009, 09:00:00 PM »
It seems that our good  pal here Rick is getting quite a lot of attentions!
http://www.jedistar.com/low_watt_amps_2.htm
Hey, I can say I know him!!!  :icon_wink:
Done an' workin'=Too many to mention - Tube addict!

frequencycentral

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Version 5 Schematic
« Reply #211 on: December 27, 2009, 10:56:34 AM »
Quote from: panterafanatic
I have a question with the biasing conversation that you and bbmonster had, which cap do you bypass when wanting a little more grit from the amp?

Here's the schematic for the version I'm building nowadays, with the biasing switch implemented:



The perf and PCB layouts earlier in this thread are based one the version 3 schematic, I haven't updated the layout artwork yet - I build these onto perf nowadays (as people seem to value my perf builds), so I kind have the version 5 layout on my head. Do people want updated layouts?
« Last Edit: December 27, 2009, 11:01:01 AM by frequencycentral »
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panterafanatic

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #212 on: December 27, 2009, 05:16:36 PM »
it's because your perf work is amazing. would the switching make noise when changing the bias point or should i shut it off before switching how it is biased?
-Jared

N.S.B.A. ~ Coming soon

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #213 on: December 27, 2009, 08:07:30 PM »
it's because your perf work is amazing.

Thanks!

would the switching make noise when changing the bias point or should i shut it off before switching how it is biased?

The switching makes a little click, it's not a problem to flick the switch with the amp turned on.
http://www.frequencycentral.co.uk/

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Custard

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #214 on: January 01, 2010, 06:56:27 PM »
Hi, this project looks pretty good and I'm going to give it a go, but still waiting (bad time of the year to order stuff) on a few parts.
An updated layout would be greatly appreciated.

Cheers,
Rob

yesitsdrew5310

Re: Power amp pentodes in parallel.
« Reply #215 on: January 04, 2010, 09:56:03 PM »
One experiment I did was to use two 5672's in parallel (but each having it's own voltage drop resistor for the heater) for the power amp - louder and ballsier

Rick, I love the design you have here.  I want to use some of the ideas in my amp that I am currently working on.  I was using an LM380 (2.5W output amp IC) with a tube preamp section.  But I am intrigued with using a 5672 in the output side of things.
My question is when you were putting the two 5672's in parallel, did the values on the resistors with the bias switch change at all?
Last question, when you put the two tubes in parallel I know it cuts the resistance in half, in this case is the Fender Reverb Transformer 22921 still applicable?

Thanks for your time and insight!


Cheers,
Drew Brashler

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #216 on: January 05, 2010, 08:02:03 PM »
An updated layout would be greatly appreciated.

On it's way soon......... ;)

My question is when you were putting the two 5672's in parallel, did the values on the resistors with the bias switch change at all?
Last question, when you put the two tubes in parallel I know it cuts the resistance in half, in this case is the Fender Reverb Transformer 22921 still applicable?

As I remember I just plugged a second 5672 into the breadboard, just isolated pin 3 for seperate heater supply. I didn't experiment with it much, but the biasing switch resistors wouldn't need to change I don't think. You're right, I think it does half the resistance, it still sounded good through Fender Reverb Transformer. I my experience you can get away with some quite extreme impedance mismatch.
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dimi3

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #217 on: February 09, 2010, 05:18:01 PM »
I been reading the whole thread regarding this amp, together with superfly :), Rick I know you are buisy testing new stuff and everyday work, but is there any chance to get version 5 layout posted? please?.

I hope that I can join the murder family soon :).

Keep up the good work.

gigyas

Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #218 on: February 18, 2010, 02:45:25 PM »
Hi all, this is my first post here, so please bear with me.
I built a Murder One using revision 5 of the schematic, minus the bias switch, just used the 100K resistor over to pin 5 on the 1044. It sounds fantastic except for one problem: it produces a soft hum at about 17KHz.  So I was wondering if anyone else had run into this, or if you guys had any ideas as to how to fix it.

Thanks in advance for the help.

frequencycentral

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Re: New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage
« Reply #219 on: February 18, 2010, 03:06:44 PM »
17KHz

........is towards the upper limit of human hearing. So it's a high pitched whine rather than a hum? If that's the case it could be that you haven't implemented the boost feature of the MAX1044, ie you need to connect pin 1 to +ve.

......and welcome to the forum, and congrats on your build - we want to see it!
« Last Edit: February 18, 2010, 03:08:20 PM by frequencycentral »
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