New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage

[max30]

Hi,

I build the last PCB version of this amp, but I have a problem with it, it looks that output tube is not working, I'm getting the sound from the amp, but the power tube doesent seem to be glowing or get hot. I changed the tube but the same result.

what could be the problem? between pin 3 and 5 on the output tube I have only 1.5V i think this is too low for HT voltage? On the first tube I have a little over 6V between pin 3 and 6, also the first tube lights up.

Am I getting the sound only from preamp tube?

Thanks for the help I hope to get it working.

Here are some pics, not the best guality:

http://www.shrani.si/f/2u/xD/dCqFkEf/img00015-20101106-1104.jpg
http://www.shrani.si/f/34/Rq/vdm8GUe/1/img00020-20101106-1129.jpg
http://www.shrani.si/f/n/Jk/22ypE7E0/1/img00021-20101106-1130.jpg

[frequencycentral]

The 5672 will not glow or get hot, that's normal. As pin 3 gets ~1.25v and pin 5 is grounded, the voltages you have between pins 3 and 5 are normal. Pins 3 and 5 are the heater connections, this tube has a very low heater voltage and current. You should find more serious voltages at pin 1 and 2.

[max30]

Hi frequency,

I soo stupid  , I didnt work with 5672 tube before and didnt know that they dont glow. Anyway, I havea very good sound out of this amp, but only volume is not as expected, the amp is as loud in 2x12 speaker cabines as let say TV on normal home music listening. Should I expect more?

On the 5672 i have the following voltages:

between pin 1&2 between 5 and 6V its changing constantly if bias switch in first position and 3,2 if in second, when in position when voltage is drifting I get some motroboating sound also.

between pin 1 and 3 i have 65V
between 1 and 4 i have 75V
between 1 and 5 67V
between pin 2 and 3 I have 69V
between 2 and 4 i have 75V
and between 2 and 5 i have 70V

Is this ok?

Thank you for the help.

[alanwf]

Hi Rick,

I'm filling out my Mouser order now! Thanks for this great project. My first charge pump usage. Looking at the data sheet for the 1044, there is a suggestion to parallel them (or even more than two) to lower power supply output resistance and up current—both seem advantageous for only an extra chip and pin 2 to 4 cap. Have you tried this? Or are the current demands so low as to make this overkill?

[patrickbrose]

Has anyone tried a switching power supply yet?
Has the issue of isolating the output jack been (yes or no) been answered?
I found a TC7660S. Is this the same as the ICL7660S, just a different manufacture?
-P

[frequencycentral]

Looking at the data sheet for the 1044, there is a suggestion to parallel them (or even more than two) to lower power supply output resistance and up current—both seem advantageous for only an extra chip and pin 2 to 4 cap. Have you tried this? Or are the current demands so low as to make this overkill?

No need, there's enough current anyway.

Has the issue of isolating the output jack been (yes or no) been answered?
I found a TC7660S. Is this the same as the ICL7660S, just a different manufacture?
-P

I never found an issue with the output socket being grounded, and I've built dozens of these.

According to the data sheet, the TC7660S will be fine.

[patrickbrose]

Thanks Rick,
Does anyone have a suggestion for a power supply for this thing? I need US specs. All I can find is a switching power supply which according to Rick is no good. So what say you? 12VDC, 500ma regulated
-P

[MetalUpYerEye]

How loud is this amp? Could it be compared to a 386 based amp (like the Ruby) volume-wise?

I've been wanting to try a tube amp build but don't want to drop $300 for all the necessary parts for a 5 watt. This seems right up my alley since its all-tube and would cost me less than $100 to build... I don't etch so... Where could I get my hands on a PCB for this bad boy?

[MetalUpYerEye]

No replies to this topic?

Is this a dead project or what?

[Taylor]

Rick has not been posting as much lately.

I do think this would be comparable to a 386 amp in terms of volume. It's a cool unit, though I haven't built one as I play bass. But if you're looking for something more than 1/5 of a watt, the Firefly is around 5 watts I think, and could probably be built for around $100.

[therecordingart]

Rick has not been posting as much lately.

I do think this would be comparable to a 386 amp in terms of volume. It's a cool unit, though I haven't built one as I play bass. But if you're looking for something more than 1/5 of a watt, the Firefly is around 5 watts I think, and could probably be built for around $100.

The Firefly is about 1.5 watts and was about $200 to build (built one last year).

[Scruffie]

You could do what i'm doing and build the Super Fly (Another of Ricks Amps... but also the Firefly so not) but use normal 12AX7 & AU7.

Be Quietish and Cheapish.

[Taylor]

The Firefly is about 1.5 watts and was about $200 to build (built one last year).

Hmm... 0 for 2 on my part. Sorry!

[MetalUpYerEye]

I'm looking for something like the Ruby. I have a friend who currently has my Ruby and is deeply in love with it. I figured i'd build one for him but I was already going to build the "Murder One" for myself, figured I might as well double my fun and make 2 murders and really blow my friends pants off... In a totally asexual way.

Any word on PCB's for this? Or should I resort to desperate times: perfboard?

[zambo]

if you make on of these with a 12au7 selp split power tube and a 12ax or au7 preamp tube you can pretty much wire the whole thing on the tube sockets themselves. It works quite well. I also use the lt1054 ( i think ) from small bear for these supplies. They are cheap and available. If you run the power supply up at around 100 volts they are fairley loud. louder than a 386 amp i think. If you use a switching supply you can run them around 200 volts or so and they are actualy kinda loud. i like to use the firefly schematic and just run different voltages. i also leave off the cascode boost tube stage so i only need two tubes. hardware store aluminum makes a decent chassis that is pretty easy to bend. Good luck, Greg

[phector2004]

Hey Rick,

Would it be a bad idea to use the 16V 4A adapter I bought for Taylor's Tiny Giant amp to power this thing up?

I'm thinking of using two regulators to get 6V and 12V for filament and circuit use.

Thanks

[Haynesarama]

Hi There Rick.

Very nice looking amp design  
Hats off to you!! I'm wanting to build one to use for practicing at lower volumes at home and for recording with cubase.
I have a couple of questions to ask first if I may  
If I wanted to hook this up directly to my computer will I need to make some kind of DI out for this?
I've noticed in one of the threads for the Murder one amp that you built one for a customer who wanted the ability to use his Murder one as a preamp also.
Would it be something like this I would need to do to hook it up to my computer or something different?
Do you have any advice on how to go about implementing this? It'd be greatly appreciated.

Also Is there a standard size tube that I could substitute easily for the 6111 and 5672 Or is that a silly question?

And finally where do you purchase the covers I've seen In the build pictures for the output transformer?
I've looked all over for some but can't find any......It'd probably help if i knew what they are called though!! Lol  

Cheers
Michael  

[frequencycentral]

If I wanted to hook this up directly to my computer will I need to make some kind of DI out for this?
I've noticed in one of the threads for the Murder one amp that you built one for a customer who wanted the ability to use his Murder one as a preamp also.
Would it be something like this I would need to do to hook it up to my computer or something different?
Do you have any advice on how to go about implementing this? It'd be greatly appreciated.

You can take a pre out from lug 2 of the volume pot, like I did here: http://www.diystompboxes.com/smfforum/index.php?topic=83831.0  The output will be pretty hot though. I've built a few Murder One with a DPDT which switches the output socket from speaker to preamp, as well as cutting power to the pentode.

Also Is there a standard size tube that I could substitute easily for the 6111 and 5672 Or is that a silly question?

That would be a different amp altogether.

And finally where do you purchase the covers I've seen In the build pictures for the output transformer?
I've looked all over for some but can't find any......It'd probably help if i knew what they are called though!! Lol 

The transformers I use are Hammond 1750A, and come like that as stock.

[frequencycentral]

My tame shred master Rich Russell did me some soundclips: http://dl.dropbox.com/u/967492/Murder%20One%20Montage.mp3

[Haynesarama]

Hi Rick.

Right then. I've got most of the Parts in stock to build the modders delight version.
I'm just struggling to get the 2 watt 18r resistors. I can find 3 watt 18r resistors, can I use these?
I can also get 1.6 watt 18r resistors if that's any better?

Also what values should I be experimenting with r13a?
And finally where in the UK (Lincolnshire) are you getting the d bar handles to protect the tubes?
I can't find any anywhere near small enough.

Thanks in advance
Michael