Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tapsnap on January 09, 2018, 04:29:47 pm

Title: First amp almost finished - thinking about my second
Post by: Tapsnap on January 09, 2018, 04:29:47 pm

Thanks to everyone for their help and guidance. I am almost finished with this, my first amp. Still have to change the grill cloth and make a  few minor changes. It sounds great and I am really quite proud. It's 4W single ended with an 12AT7 and 6BQ5 pentode. It begins to overdrive at around 7 on the volume. I deviated from the schematic a little with a second jack socket that gives me a normal and bright. and I included a cathode bypass capacitor on the input side of the preamp. The schematic was designed by Rick Campbell of Rick-tone amplifiers.

(http://www.danieloates.com/wp-content/uploads/First-amp-1.jpg)

(http://www.danieloates.com/wp-content/uploads/First-amp2.jpg)

(http://www.danieloates.com/wp-content/uploads/First-amp-3.jpg)


I'm now looking at another one of Rick Campbell's designs. This time its a push-pull.

(http://www.danieloates.com/wp-content/uploads/Powersupply.jpg)

Looking at the power supply, I'm a little unsure about what I should buy. I am looking at this one. What do you guys think.
https://www.tubesandmore.com/products/transformer-hammond-power-125-0-125-v-100-ma (https://www.tubesandmore.com/products/transformer-hammond-power-125-0-125-v-100-ma)

Title: Re: First amp almost finished - thinking about my second
Post by: kagliostro on January 09, 2018, 05:13:11 pm

Nice Job   :thumbsup:


Franco

Title: Re: First amp almost finished - thinking about my second
Post by: shooter on January 09, 2018, 05:13:41 pm

Don't use the CT on the tranny, expect a little higher volts loaded (250*1.414=350vdc).  what are the power tubes?  6V6, EL84's should be fine, 100mA might run somewhat hot depending on your #'s

Title: Re: First amp almost finished - thinking about my second
Post by: pullshocks on January 09, 2018, 10:20:12 pm

Great looking amp build.  I like the angle you used on the speaker baffle.  Cosmetically, the name plate gives it a lot of flare.


But I really want to know more about the guitar.  I couldn't help noticing it  has the same logo as the amp.....

Title: Re: First amp almost finished - thinking about my second
Post by: sluckey on January 09, 2018, 11:13:12 pm

Complete schematic...

Title: Re: First amp almost finished - thinking about my second
Post by: Tone Junkie on January 09, 2018, 11:32:43 pm

Looks great, welcome to the addiction. I would go with a transformer at 190-0-190.
Bill

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 10, 2018, 07:14:40 am

Sluckey, you are correct that is the schematic I am using. Tone Junkie, you're thinking that I should use the center tap and one half of the secondary, right? Pullshocks, that is a guitar I designed and built myself. I designed it about 25 years ago but didn't get around to building it until 3 years ago.

Title: Re: First amp almost finished - thinking about my second
Post by: shooter on January 10, 2018, 06:11:54 pm

Quote

I should use the center tap and one half of the secondary, right?

That is a bad Idea, it "works", my breadboard is currently set that way, but the Correct way is get a PT that works end to end.  The CT is used OR not, depending on your rectifier.  The CT is NOT used as 1 leg of your secondary AC

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 11, 2018, 07:53:58 am

In that case, this is the closest transformer I can find that would be suitable. https://www.tubesandmore.com/products/transformer-hammond-power-125-0-125-v-100-ma (https://www.tubesandmore.com/products/transformer-hammond-power-125-0-125-v-100-ma) Unless anyone here can guide me to a bigger selection of transformers.
By the way, why is it that the manufacturers of transformers have to be so mysterious about the value of their products? Put some goddamn specs on your transformers!!!!!

Title: Re: First amp almost finished - thinking about my second
Post by: bnwitt on January 11, 2018, 08:50:50 am

Tapsnap,
Where did you have the amp front Logo made?

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 11, 2018, 09:04:05 am

bnwitt, I had it 3D printed form a 3D model that I made in a program called Lightwave 3D. Originally I drew it out on paper, scanned that, and brought it into Adobe Illustrator, where I made it into vector Art. I imported that into Lightwave3D and extruded it into a 3D object. Then after a lot of manipulation, cutting welding, merging and fixing of the mesh to form one enclosed mesh object, I saved it as an STL file and sent it to Shapeways 3D printing. (All together it took about 6 hours). Ten days later I got back my Logo.

Title: Re: First amp almost finished - thinking about my second
Post by: mresistor on January 11, 2018, 09:09:42 am

What about this company and here is an example that might work.  Probably over rated for your use though..


http://www.edcorusa.com/xpwr146 (http://www.edcorusa.com/xpwr146)

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 11, 2018, 10:57:47 am

That looks good, but might this be better? http://www.edcorusa.com/xpwr012 (http://www.edcorusa.com/xpwr012)

Title: Re: First amp almost finished - thinking about my second
Post by: sluckey on January 11, 2018, 11:17:55 am

Quote from: Tapsnap on January 11, 2018, 10:57:47 am

That looks good, but might this be better? http://www.edcorusa.com/xpwr012 (http://www.edcorusa.com/xpwr012)

That's perfect. But you'll have to remove the bridge rectifier and use a conventional full wave rectifier (two diodes) with the center tap connected to ground.

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 11, 2018, 01:25:03 pm

OK, good. Thanks for your help and thanks to mresistor for showing me that website

Title: Re: First amp almost finished - thinking about my second
Post by: mresistor on January 11, 2018, 03:46:38 pm

I"m miffed  I thought you were looking for 175 to 200 VAC on the secondary which it shows in red on the schematic.

Title: Re: First amp almost finished - thinking about my second
Post by: Tapsnap on January 11, 2018, 05:03:41 pm

Yeh, what's the problem?

Title: Re: First amp almost finished - thinking about my second
Post by: birt on January 11, 2018, 05:10:07 pm

lookin' good! (and that guitar.. wow)

Title: Re: First amp almost finished - thinking about my second
Post by: mresistor on January 11, 2018, 07:14:56 pm

Quote from: Tapsnap on January 11, 2018, 05:03:41 pm

Yeh, what's the problem?

Are you using only half of the secondary on the Edcor xpwr012?

Title: Re: First amp almost finished - thinking about my second
Post by: sluckey on January 11, 2018, 08:01:48 pm

If he follows my suggestion he will be using the entire secondary of that Edcor xpwr012 and he will have exactly the same B+ as the original PT provides.

Title: Re: First amp almost finished - thinking about my second
Post by: mresistor on January 11, 2018, 08:36:45 pm

Neve mind --  brain fart.. 


Tapsnap - that's a beautiful amp you made and the guitar is also really nice..  Congrats..