transformer - minit tube ??

[LightSoundGeometry]

For the Rick holt design tube amps are the hammond 125a and the fender 022921 interchangeable ?

from googling and trying to find something I am getting mixed up ..the data sheets show and output Z of 8 ohms and 15 ohms between the two but then read the ratio is somehow the same in the 125a to put out 8 ohms?

i will build this tube amp if its the last thing I ever do .. I have new tubes coming in the mail because I am going to try that ..cannot believe its been 8 weeks and I still cant get this thing working ...although my 5672 knowledge has grown enough I started moddign it to my own design !only thing that scares me is the heat sink on those, I leave them off..its gets hot but not extremely too overheated seeing 12 volts but then again its not august and 100% humidity either ..

I have two 022921's and was going to try another layout as the murder 1 is giving me fits .so maybe get lucky with the others ones FC has drawn up

http://www.mouser.com/ProductDetail/Hammond-Manufacturing/1750A/?qs=hGvGUDq83YFpirj%252bNxa4Sg%3D%3D

they have the trans al in same reference here
http://www.classictone.net/40-18034.html

here where I got confused "8 ohms, equivalent to #125A20B & #022921." is a 125A same as a 125a20b ?
https://www.tubesandmore.com/products/P-TF22921

this one looks more similar
http://www.mouser.com/ProductDetail/Hammond-Manufacturing/1750A/?qs=hGvGUDq83YFpirj%252bNxa4Sg%3D%3D


Links to schematics
https://www.google.com/search?q=murder+one+sub+mini+tube+guitar+amplifier&biw=1280&bih=556&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjyu8HBgbrMAhUITSYKHcCnCSIQ_AUIBygC#imgrc=h1WbU-MOWFqmUM%3A

[thermionix]

I'm not familiar with the circuit you're building, but the Hammond 125A is listed as a push-pull OT and the 1750A and 022921 are single-ended.  The latter two appear to be interchangeable.

You probably know this, but a transformer doesn't "know" ohms, just turns ratios.  The impedence ratio is the square of the turns ratio.

[LightSoundGeometry]

it had a low weird gargle/squelchy sound coming out, then i think it was the tube starting stinking like a smell I have never smelled before..like electrical fire maybe ..so I shut it down but the sound in the speaker had stopped ..no signal ever come through

what are the chances of burning down my home?  from all of rick's pictures, and threads around the net etc, this looks like a pretty straightforward, simple, easier build ..I know its harder than that but i didnt think it was going to be like this?

I was messing around with my vox head just observing it while it was operating, the tubes get hot but dont put off a fire/burning odor

I took it apart, but I remember the voltage on the 5672 pin 1 was the B+ at 50-70 volts  , same on the 6111 but I think it was pin 4 that had 4-5 volts ..

either way something was not right ..maybe I am too stupid to learn how to use the power supply ..I guess there comes a popint where brainpower and creativity limits, stops and discourages one..I feel as though i am done and giving up ..I read and watch videos but its not enough for me, I need a teacher to do this because i lack the reading and comprehension skills to learn from a few googled searched articles or whatever. wish I could go to a college and take a class on how to properly handle this stuff and do a tube amp..

I think I am going to get all the electrical stuff together and sell it off in a grab bag/lot type bundle..i am thinking about it ..I bet I have 200-300 dollars worth of parts and things here ..the two transformers I bought were 20 bucks per with shipping alone ..

the guys on youtube make it look easy and no one ever really goes into a classroom, instructional vocational type step by step way to do things ..its like a dirty little secret and you have to just be smart enough to figure it out ..which I am unable to do and now I am scared of burning down my house ..I wish I had a shed or a garage

[thermionix]

That "burning electronics" smell is one you'll never forget, and one that might save your life some day.  (I could tell you a story about a cheap space heater at my sister's house).

I think you can figure out tube amps if you keep at it.  Generally they are much simpler than most of the pedals folks here build, just more dangerous because of the electrical power involved.

I don't know if it's still in print, but Dan Torres had a book called "Inside Tube Amps" written pretty much for dummies (like me) and was a very good starting point.  I built my first amp (tweed Bassman) with nothing much more than that, and it worked and sounded quite good.  And nobody died.  Though I did end up with a couple stitches (long story).

Sure all the information is on the web, but so much it can be overwhelming, and there's probably as much bad info as good.  Also, sometimes it's nice to just use a real book.  You can highlight, underline, scribble in the margins...

[duck_arse]

ahhh, paper, do they still have that?

keep at it. you'll grind it down through sheer persistence, if nothing else. I nearly had the burning smell here today, trying to stop a tikking valve but adding high volts electros. it was a good thing I had the cro attached each time I turned on the juice, because the volts didn't come up to where I was expecting (twice), so I switched off, kwikish. and both times, an electro was backwards, and both times, they ended in the bin. one was hot, but it wasn't banged yet .....

and why would you want to burn down a perfectly good shed as well as your house?

[Ripthorn]

Go google the Valve Wizard guide.  it is like a text book but on the web.  Merlin does a great job and he frequents here now and again.  Also, asking very specific questions will get you very specific answers that will also elaborate on the "why's" and "hows".  If you want the result that Rick gets, use the parts he uses.  Substitutions are simply and introduction of more variables that lead to problems.  I know you have the transformers on hand, but it you want what Rick built, build it like he built it.  Rick and I used to have lots of submini amp conversations 7-8 years ago and he knows his stuff.  I have been out of the stompbox and amp world for a little bit (too focused on building guitars and making woodworking tools), but I've still got all the stuff. 

Sometimes you just have to put it on the back burner for a while, let the frustration die down, and then take another crack at it.  I had to do that with a submini amp I built that could be described as "overly ambitious". I am certain you are more than capable of learning this, but it will require your effort.

[LightSoundGeometry]

its on the back burner ..they have a 12ua7 on multi sim in the misc parts section..maybe i can get it to conduct and bias ..need a 12ua7 basic amp schematic to get going with ..I have like 10 days left on my free trial

I will have to look up the pdf/online book link you sent and hopefully that helps ..I may have reached my brain power and learning potential..without some type of hands on or real instruction/guidance I may not be able to do it ..my reading and comprehension is on a very low level . I was under the impression one can work the brain like a muscle and grow it, or make it strong, but I seem to be on information overload. I learn one thing, then forget as I learn something else.

im wondering if I should start with a Kit from a tube store ..but if I had 250 bucks I would get a laser printer and try to etch a board ..just to etch a board I am looking at 100-250 dollars including the pnp paper, laser printer, etching solution etc etc ..

nothing but a money pit at this point ..all the cash I have wasted I could have me a JCM 800 head by now and be practicing the guitar ..have to put it down and come back later I guess. I will try to bias out a 12ua7 and see what happens on multi sim hopefully sometime before this sunday..have a lot of work to do and two yards to mow.

[thomasha]

Hi, which layout are you using?
The link you posted shows the superfly schematic, although you referenced the tube as beeing a 5672.

the murder one, that uses the SE fender reverb transformer which gives you 22.5k primary with a 8 ohms speaker connected, uses the 5672.
The 5672 has a direct heated cathode, that works with 1.25v, and the murder one has a special resistor (220 i think) to drop the 12v to 1.25v, please don't change that resistor, because it's not a normal cathode resistor.That could produce some smell.

Are you using the murder one's charge pump with the capacitors? my charge pump, even working perfectly produced a smell of hot electronics, that was really weird.

the 125A is a PP transformer, and is used in the superfly, you can't use it in the murder one, the same way you can't use the fender reverb in the superfly, cause it only has 2 primary connections and is for SE.

You could use a SE transformer in the superfly if you changed it to parallel SE, where both plates are tied together, you would need to change the cathode resistor probably.

now some questions...

which amp do you wan't to build? which tubes are you going to use? with which transformer?

I built several of the FC amps, and made some with different layouts.

[LightSoundGeometry]

Hi, which layout are you using?
The link you posted shows the superfly schematic, although you referenced the tube as beeing a 5672.

the murder one, that uses the SE fender reverb transformer which gives you 22.5k primary with a 8 ohms speaker connected, uses the 5672.
The 5672 has a direct heated cathode, that works with 1.25v, and the murder one has a special resistor (220 i think) to drop the 12v to 1.25v, please don't change that resistor, because it's not a normal cathode resistor.That could produce some smell.

Are you using the murder one's charge pump with the capacitors? my charge pump, even working perfectly produced a smell of hot electronics, that was really weird.

the 125A is a PP transformer, and is used in the superfly, you can't use it in the murder one, the same way you can't use the fender reverb in the superfly, cause it only has 2 primary connections and is for SE.

You could use a SE transformer in the superfly if you changed it to parallel SE, where both plates are tied together, you would need to change the cathode resistor probably.

now some questions...

which amp do you wan't to build? which tubes are you going to use? with which transformer?

I built several of the FC amps, and made some with different layouts.

I am trying the subcaster and the murder one

http://www.diystompboxes.com/smfforum/index.php?topic=113876.msg1055724#msg1055724

I was hoping to build a small watter 5-15-30 watts maybe;  similar to any on the market ..one with an input transformer taking the wall 120volts ..then through a pre amp and a power tube section and back out through a transformer to the speaker ..I guess i will have to build a rectifier and filter section as well ..not sure if the rectifier is part of the input transformer but I am not that far yet ..still need to learn the minis I think first.

[thomasha]

Well, for the subcaster, if I got it right, you want to build the murder one output stage>


check also the murder one thread!

in the other thread I saw it wasn't working, check if you have all the connections, I could not see where the 60V goes to the output transformer, it should be the red wire.

as for voltages it looked ok, could you check what is different in your build and the schematic?

As for a higher wattage amp, I would start with the P1 from ax84, is like a valve junior, gives about 5W, and is a good start, you will learn all the small tricks for heater wiring, power supply, and bias. There is a lot of material available, voltage readings and so on. And start with a low gain amp, otherwise there is a big chance that you would end with a squealing machine, unless you follow a well known build layout, as a kit.

[LightSoundGeometry]

Well, for the subcaster, if I got it right, you want to build the murder one output stage>


check also the murder one thread!

in the other thread I saw it wasn't working, check if you have all the connections, I could not see where the 60V goes to the output transformer, it should be the red wire.

as for voltages it looked ok, could you check what is different in your build and the schematic?

As for a higher wattage amp, I would start with the P1 from ax84, is like a valve junior, gives about 5W, and is a good start, you will learn all the small tricks for heater wiring, power supply, and bias. There is a lot of material available, voltage readings and so on. And start with a low gain amp, otherwise there is a big chance that you would end with a squealing machine, unless you follow a well known build layout, as a kit.

since I have your help right now, i will get this back up on the BB with some pictures and measurements ..see if you can spot any errors i have going on ..I wont have it all done and posted until at least midnight my time CDT

for the transformer, I was using Ricks diagram
http://s210.photobucket.com/user/frequencycentral/media/22921.jpg.html?sort=3&o=479

got this from a google search

red=B+
blue=plate anode
black=common
green=8 ohms

[thomasha]

yes, the transformer connections are ok,

maybe we could start checking from the output stage, could you inject some signal at the 5672 imput grid? like mp3 or something to see if there is something coming out. and check the cathode/heater voltage (should be 1.25V).

You could disconnect the b+ and 12V going to to preamp tube to see if the problem is at the 5672.

If it works, and there is some sound coming out of the speaker, then the problem is at the preamp.

It's almost midnight at my time zone, so we can discuss any other check tomorrow.

[LightSoundGeometry]

tied one on last night for the hockey game, we lost, so I will work on it tonight ..but first :

office max had a liquidation sale and I got a hp p1102w laser jet for 50 bucks, gloss paper 7 bucks,  a side of clad for 4 bucks and a bottle of 13 dollar etchent from radio shack today and borrowed my moms iron  ..going to give pcb etching a go tonight before I do anything!

I posted in the wrong thread..I didnt mean to spam the other guys thread ..i misread the titles

my apologies