Fuzzy sound

[Stevem]

I think at this point your issue is a partially blown speaker.

Do you have known good headphones you can jump in and listen to ?

[sluckey]

Fuzzy sound:

No sound! You must include a sound file between the mp3 tags

I have been wondering about the speaker. What I have is a pair of Wal Mart automotive speakers made to be used in a car sound system. the two of them cost $30 for the pair. Any chance of having speaker trouble?

That's very likely. A car speaker is not designed to handle a guitar amp's signal. Using a proper guitar speaker just may be your solution.

[Titan.300]

I have tried to post a sound but somehow it doesn't work for me.
What I'm running is a number 42 output tube which is the older version of the 6F6 which was widely used in table radios. I'm running the tube at .027 milliamps cathode current at 230 plate volts
.027*230=6.31 watts. and I don't run it at full volume. This should not be too much for a car speaker unless there's something different about car speakers. The mate to this speaker shows the same problem.
At tubes and more.com they have a 6 inch Jenson guitar amp speaker for $30. I might try that one with my nextg order.
The prototype amp sounds great with my screen reader and documentarys sound tracks, what I have is a slight Distortion in the midrange frequencies with music, not much but just enough to be an anoyance.
My daughter asked me to build her an amp also and I want very much to find this problem.
Kenneth Atkins Rockdale, Texas.
Phone calls are welcome
512 446-4242
molly14tx@gmail.com
P.S. Molly was a pet dairy cow in the 90's. She lived to be 14 years old amd I moved her from Indiana to Texas with me in the summer of 97.

[Titan.300]

Folks I tryed my earphones on my prototype amp and the sound is just as clear as my store bought speakers. This dirty sound must be this Wal Mart speaker! I have never encountered anything like this before. How can Wal Mart get away withselling something like this or is this fuzzy sound not noticed in a moving car with all of the road noise? I will have a replacement Jenson guitar speaker on my next order to tubes and more.
Thanks everybody.
Kenneth Atkins Rockdale, Texas.
Phone: 512 446-4242
Email: molly14tx@gmail.com

[didit]

Hello --

Excellent news. Congratulations on the successful build, and discovering Walmart can really suck.

Best .. Ian

[Stevem]

It was just defective from the day they made it and boxed it up at the factory.

There is all too few quality control checks done on 95% of what gets made in and shipped out from China and a few other countries.

[Titan.300]

Transcribed schematic
Since I am blind I can't draw you a schematic. This is the best I can do.

Let's start with the power supply. The transformer is a replacement for the Fender
Bronco, Champ, Princeton, Princeton Reverb, Vibro Champ
The transformer is made for 120 volts AC and the primary leads are black.
The black power cord lead goes to the on and off switch on the front panel, from there to the transformer. The other lead from the transformer goes to the fuse holder, The other side of the fuse holder is connected to the white lead from the power cord. This arangement makes sure no power is on the fuse holder when the power switch is off.
The center tap on the high voltage winding is connected to the ground. the two 275 volt taps on the high voltage winding go to the plates of the 5U4 tube.
The 5 volt filament leads from the transformer are connected to the filament pins on the 5U4 tube socket.
There is a silicon diode and a 390 ohm 2 watt resister in series going from the tube plate to the 5U4 tube filament. This arangement lets the tube carry half the current load.
One side of the 5U4 tube filament goes to a Fender Bandmaster 90 milliamp choke. The other choke lead goes to the 40 and 20 MFD filter capacitor alongside the 5U4 tube. There is another 40 MFD capacitor hooked here as well making a total of 100 MFD.
(Note: The power supply has a 4 section filter capacitor 40/20/20/20).
(Note: This amplifier is stereo, both Circuits are alike).
There is a 30K ohms 2 wwatt resister connected to the 100 MFD capacitors and the other end connected to section 3 of the big electrolytic power supply capacitor. This is the decoupleing filter for the 12AX7 pre amp tube and the 6C6 driver tube.
The signal comes through a one forth inch stereo jack at the left rear corner of the chassis. There is a one eighth watt metal film 48K resister soldered across the jack Terminals between the hot and the ground. This is the impedance load the computer's sound card expects to work into. There is a .01 MFD capacitor connected to the hot Terminal of the jack and the other end connected to the center wire of a shealded cable going to the grid of the 12AX7 pre amp tube. The braid of the shealded cable is connected to the ground at the jack. The braid of the shealded cable is not connected to anything at the tube end. This prevents a ground loop from causing humm problems.
There is a 1500 ohms resister connected from the ground or B- to the cathode of the 12AX7 tube. There is a 25 MFD electrolytic bypass capacitor connected between the cathode of the 12AX7 tube and the B- or ground.
The grid of the 12AX7 tube has a 68K resister connected to the B- or ground.
The plate of the 12AX7 tube has a voltage divider on it. The signal voltage level was too strong for the 6C6 tube. The plate has a 150K ohms resister connected to it and spliced to a 100K ohms resister connected to the decoupleing filter. The output capacitor is connected to this splice The other end of the .01 MFD output capacitor is connected to one side of a 1 Meg volume control. The other side of the volume control is connected to the ground or B-. The center Terminal of the volume control is connected to the grid of te 6C6 driver tube.
The 6C6 driver tube has a 12K ohms resister and a 25 MFD electrolytic capacitor connected to the cathode and the B- or ground.
The screen grid and the plate are connected together at the tube socket, i'm running the tube as a triode.
There is a 220K ohms resister connected to the plate and scrreen lead going to the same decoupleing filter that the plate resister of the 12AX7 pre amp tube is connected to.
The plate of the 6C6 has two capacitors connected to it, one of them a .01 MFD capacitor going to the grid of the 42 power output tube and the other .005 MFD capacitor going to the B- or ground.
The cathode of the 42 power output tube has a 390 ohms 2 watt resister and a 100 MFD electrolytic capacitor going from the cathode to the ground or B-. The control grid of the 42 has a 270K ohms resister connected to it and the B- or ground.
The screen grid has a 10K ohms resister on it going to the decoupleing filter where the red lead of the output transformer is connected.
The decoupleing filter for the 42 tube consist of a 22 MFD electrolytic capacitor connected to a 750 ohms 2 watt resister going to the 100 MFD electrolytic capacitor in the power supply.
The blue lead of the output transformer is connected to the plate of the 42 output tube. The 8 ohm secondary of the output transformer is connected to the speaker through a RCA phono pin jack and plugg.
I'm sorry but this is the best I can do as I'm totally blind. I have been using this amplifier on my computer for a few weeks looking for the cause of that fuzzy sound. Everything is working fine and I'm ready to start building.
Kenneth Atkins
512 446-4242
molly14tx@gmail.com

[Titan.300]

Hello Everybody
I got my new Jenson 6 inch speaker today and installed it in the wooden speaker box. My Slim Dusty files never sounded so good. Bright and clear.
Can someone explain to me what the difference is between the 8 ohm signal from a car stereo and the 8 ohm signal from the secondary winding of a output transformer powered by a tube?
Kenneth Atkins
512 446-4242
Molly14tx@gmail.com

[Stevem]

There is no difference between the two in simple terms, they are both generating AC signwaves .

Putting wattage aside the only difference between the two would be the frequency response between the two .
The car stereo would likely have the wider frequency responce

[pdf64]

Can someone explain to me what the difference is between the 8 ohm signal from a car stereo and the 8 ohm signal from the secondary winding of a output transformer powered by a tube?

A standard solid state amp acts as a voltage source, it has practically zero output impedance. eg if it's putting out 5V AC signal, it will be 5V regardless of whether the load it's driving is 8 ohms, 4 ohms, 16 ohms, 100 ohms or even no load.
The constraint is that if the load impedance becomes too low. As the load impedance is reduced, at some point it will draw too much current through the output devices and they'll overheat.

A valve output stage will have an output impedance that's typically around (triode), or higher than (pentode), the intended load impedance.
As the load impedance is reduced or increased from the intended value, the output voltage across the load will change, the maximum possible power output that the amp is capable of will be reduced.

[Titan.300]

That's what I thought, then there should be no reason a car stereo speaker wouldn't give satisfactory performance on a tube amplifier. Since both of these Wal Mart speakers had the same problem I can only conclude this is a design fault.
I lost my 20/200 eyesight in 87 and couldn't read schematics anymore so I don't know how much things in the electronics field has changed but I remember when transistor Devices had a output transformer just like a tube.
Someone who punches holes in a speaker cone with a pencil to get a fuzzzy sound should be quite happy with speakers like this. Anybody intrested?
Kenneth Atkins
512 446-4242
molly14tx@gmail.com

[pdf64]

... The transformer is made for 120 volts AC and the primary leads are black.
The black power cord lead goes to the on and off switch on the front panel, from there to the transformer. The other lead from the transformer goes to the fuse holder, The other side of the fuse holder is connected to the white lead from the power cord. ...

That arrangement was acceptable in North America in the era when mains power connectors were unpolarised, ie it was random which wire of the incoming power cable was live / hot and which was neutral.
In the modern era of polarised connectors though, fitting the fuse in the incoming neutral feed doesn't protect the equipment / user / building from a fault between live and earth.
So the fuse needs to be moved to the live side.
The fuseholder end and side lugs should be wired such that the side lug is the one that's deenergised if the fuse blows.

[martin manning]

The fuseholder end and side lugs should be wired such that the side lug is the one that's deenergised if the fuse blows.

In plain language that means connect the hot lead to the end lug of the fuse holder. This is done so the fuse cannot contact the hot lead until it is almost fully inserted.

[Titan.300]

Gentlemen:
Here in Texas the right hand side of the wall socket is the black or hot wire, the left side or white wire is the ground return. The green third wire is the ground safety wire. That one is soldered to the chassis to prevent a shock hazzard.
This first amp is going to my daughter who has small grandchildren in the house. The reason the fuze holder is downstream from the power switch is when the power is turned off there will be no voltage on that fuze holder for safety.
The only reason i'm using a fuze in the circuit is to protect the power transformer if something else in the power supply shorts. Did you ever see a power transformer go up in smoke? I have once and seen the remains of several others.
My son who works on a dairy farm had a transformer go up in smoke and he replaced the transformer with a new one only to have that one go up in smoke also. He traced the trouble to a shorted diode bridge which had to be replaced. Things can and sometimes do go wrong.
With those small children in the house I need to put a clear bottom cover on this chassis. Something that can be seen through but not touched.
I have a problem with a big multi section capacitor made by J.J. Electronics. The mounting holes in the foot of the clamp where it bolts onto the chassis is too close to the body of the capacitor and doesn't leave enough room to get the nut on the screw. Any ideas? I finally gave up and put the clamp on the top of the capacitor upsidedown and bolted the capacitor mount to the underside of the chassis hanging down. The chassis is three inches deep so I still have room to wire it but this looks like crap and I don't know what else to do.
Kenneth Atkins
512 446-4242
E-mail: molly14tx@gmail.com

[Titan.300]

Hello Everybody:
That new Jenson speaker really done the trick. All of that dirty sound is gone. I have been using my prototype tube amplifier on my computer sound card for some time now. To me it sounds better then the big sub woofer speakers I bought from Amazon 5 years ago. I didn't know how much I missed the sound of tubes. I'm working to get it built into a metal chassis now and it is proving to be quite challenging, a little more then I expected.
I have been wondering what it would cost to get someone else to finish this job.
Anyway what I wanted to write about is I noticed a reduction in bass frequencies with this new Jenson speaker and I am a little unhappy over that. I think I know what the problem is, the speaker cone is too light weight, the other speaker had a heavyer thicker cone which made it more responceave to the lower bass frequencies. Does anyone know where to buy a 6 inch speaker like this but made to work on a guitar amp? I have a audio editor called Gold Wave so I can boost the bass frequencies by 5 DB. which brings my bass back but I have Thousands of songs and I would have to go through the whole collection and that could take months. moreover if I share my music with someone else it might not sound good on their system. Is there any way I can boost bass by changeing capacitor values in my amp? I'm using .01 MFD values throughout. I have a .005 MFD capacitort from the plate of the 6C6 driver tube to the ground for tone control. It seems to me if I could raze this value a bit I could reduce the volume of the high and mid range frequencies a little and raze the overall volume to offset. I'm not sure what value to try. Any ideas?
Kenneth Atkins
512 446-4242
molly14tx@gmail.com