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PostPosted: Thu Mar 29, 2007 11:19 am 
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hello everyone, i'm jake from texas and i'm new to the forum. In a build im currently working on, I've probably found more information on this site than any other, so I hope you don't mind me picking your brains for a little more amp specific info.

So it started as a 36 watt tmb as most of you probably know. anyway, i build a new board and changed the tmb channel to a ef-86 channel with vol/gain, tone, cut, and master. i left the 18watt side alone just with the volume and tone. as of now, there's just the 12ax7 for the 1st channel, the ef-86 for the 2nd channel, and a 12ax7 for the phase inverter. i started looking into it more, and i will shortly be changing the entire power and filtering sections to be that of a dc-30.

my question is this:

I had a friend that has a dc-30 combo that would totally hang with my 5150 half stack...why am i lacking the volume that this thing had? i was looking at a dc-30 schematic, and was wondering if it was the lack of another 12ax7 as a second gain stage? I am running it through a 4x12 with celestion g12 series speakers. I play in a band and i'm just not cutting through at all, pretty much buried. I couldn't imagine it being this low. I know volume is a really subjective thing, so bear with me on this one. I just thought that 2nd 12ax7 would be what bumped the signal back up, and since i didn't have it...that's why i'm at a loss for volume.

if anyone has any thoughts on this issue, i would be utterly greatful for your help. thanks in advance.

(i edited this post after finding voltages at the bottom of the schematic i was looking at :) )


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PostPosted: Thu Mar 29, 2007 1:13 pm 
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Quote:
hello everyone, i'm jake from texas and i'm new to the forum.


Welcome!

Quote:
just the 12ax7 for the 1st channel, the ef-86 for the 2nd channel, and a 12ax7 for the phase inverter. ... why am i lacking volume ?


If there is no 'tone stack' you should be OK with just one AX7. Is the 12ax7 paralleled? The DC30 is.

Is the EF86 volume OK? Where did you hook it in & how? That can make a big difference.


B+ with tubes should around 350 + The voltages should be roughly the same as the 15 posted elsewhere in this forum . I can look up the EF86.

Even a 15 does not lack for volume, so the 30 should be more than enough.

Sounds like you need to modify your amp into more of a 30 watt version of the new TC-15. No shortage of level there. 8)

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PostPosted: Thu Mar 29, 2007 3:38 pm 
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now someone is talking my language;)

thanks for starting me on the right track here coco.

this is the layout that i had drawn for what i have right now.
http://i150.photobucket.com/albums/s83/ ... yout-1.jpg

this will show you how i have the ef-86 and the ax7 wired.

just to kind of clear some other things up...(i've changed things since i uploaded this image)

i have:
- changed the bypass cap on the ef-86 to 22uf as opposed to 16uF.

- the master volume and cut control are wired correctly now (per dc-30 schematic and layout) so they work how they should.

also, continuing with a little bit of my background so you know who you're working with here :). this is my second build. i build a 100 watt '68 super lead clone as well. that one i followed the layout pretty much stock, beings that i wanted that amp. this is the first time i start deviating from any one stock layout. it's been really fun, and i've learned a whole lot. that's not to say that i think i'm still at the tip of the iceberg. so with that in mind, if i say some things that might not sound like a seasoned amp builder, that's mainly because i'm not. i'm still learning!! so thanks for your understanding and help. i just want to have an amp that sounds great and you seem like you're one whos willing to help with that.

jake


Last edited by Glass Tornado on Thu Mar 29, 2007 5:56 pm, edited 1 time in total.

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PostPosted: Thu Mar 29, 2007 4:15 pm 
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There are a lot of changes from the stock 15/30.

E.g. Your MV is not a post MV, and the way it's configured, it might be loading down the output;
the PI is not exactly the same either and where the input is injected is slightly different;
V2 is not there obviously;
the pots are 500K, not 1M which may not have much effect.

Take a look at the 15 layout and compare it to yours. I'll post the TC-15 layout soon and it is a perfect place for you to compare if you want to. Then add the extra two power tubes.

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PostPosted: Thu Mar 29, 2007 4:37 pm 
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coco,
thanks for the quick response.
in my earlier post, i was explaining how the "master volume" set up in that picture isn't what i have now. when i had it wired that way, it was actually quieter than it is now. haha! but i now have it wired as a ppimv and it did seem to help with the volume a little. that picture was the beginning of this transitional period for my amp. :)

it would be great if you could put the tc-15 layout up for me.
like you said, i think it would clear up a lot of small overlooked, or misunderstood details that probably will add up to me having a great head.

i'm glad you're helping me with this. like i said, as my first attempt to change a bunch around, i've taken schematics and layouts and pieced together the things that i liked and took out what i thought i disliked. i think it's the transitions of these different circuits that aren't as seamless as i would like them to be.

talk to you soon.

jake

p.s. i just uploaded the updated layout picture in the last post.


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PostPosted: Thu Mar 29, 2007 9:59 pm 
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so i had more time to do some poking around on this forum. man, lots of good information. i realized that you have the tc-15 layout and schem up on the spitfire and lightning forum. sorry to keep hounding for something that was already there.

here's a couple of questions that are specific to me, so i hope they haven't been covered on here and i just didn't see them. :) here we go...

1. with the pt i have, after rectification i have either 298 vac with the lower leads, or 409 vac with the higher leads. i know that on the dc-30 schem it's looking for 350vac off the rectifier, and your layout is showing 340-360. can i just use a resistor to knock the 409 down about 50v?

2. if i'm running my b+ at about 298 right now, would a higher b+ end in more output? i'm still trying to wrap my head around the voltages and what effect they have aside from tonal differences.

3. I ended up putting 8.2k swamper resistors on my build. i noticed that your layout, and the dc-30 use 1.5k. maybe you can solidify my knowledge of this as well...from what i understand, as the value of these resistors go up, the high end slightly gets rolled off more and more. with dropping these to the 1.5k value, is it going to pass more high end? give a little more sparkle? am i way off base?

i'll leave it at that for now. I hope i'm not bugging you to pieces with these questions.

thanks a lot,

jake


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PostPosted: Thu Mar 29, 2007 11:08 pm 
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I am no expert in tube design, but here goes...

Quote:
can i just use a resistor to knock the 409 down about 50v


Yes, but it will be very large and dissipate a lot of heat. There are other means like using zener diodes described eslewhere. You might be able to reduce it safely by 10 volts with a large power resistor. Depending on what rectifier you're using, a better bet would be to use a less efficient rectifier, like a 5Y3. That will affect the sound tho.

For voltage ideas, check out: viewtopic.php?t=568&highlight=

Quote:
if i'm running my b+ at about 298 right now, would a higher b+ end in more output?


Not necessarily. Power output is dependent on a lot of factors. OT impedance, tube charatereistics, bias, etc. Within reason, Higher voltage will give the amp more bright sparkle but possibly brittle sound. Lower will be smoother, creamier and possbily cold or mushy sound.

Here is a technical discussion on calculating power of a tube.
http://members.aol.com/sbench102/po-dis.html

Quote:
i noticed that your layout, and the dc-30 use 1.5k. ...from what i understand, as the value of these resistors go up, the high end slightly gets rolled off more and more. with dropping these to the 1.5k value, is it going to pass more high end? give a little more sparkle?


What you are calling swamper resistors are called Grid Stopper Resistors. This can also control gain between stages and also interacts with the tube to roll off highs. Values can be 1.5K->100K. Larger values roll off more highs and reduce gain between stages. The Grid Stopper Resistor works best when mounted directly or as close as possible to the grid pin.

So the answer is yes, it will pass more high end & give back some sparkle.

Hope this helps. TC-15 layout and schematic is under development, but you can combine the 15 & DC-30 to get a decent idea.

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PostPosted: Fri Mar 30, 2007 9:19 am 
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i was just curious, what is the effect on the b+ with two 5v4's installed as opposed to 1 gz34? much difference? none at all?


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PostPosted: Fri Mar 30, 2007 9:36 am 
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The rectifier circuit gives you the flexibility of using one 5AR4 for a quick attack or you can use two 5V4's for a smooth round response.

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PostPosted: Fri Mar 30, 2007 9:52 am 
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man, looks like you're on the same schedule as me. late to bed early to rise!! stephen, thanks for all the info. i think this has been plenty to chew on for the next little bit. hopefully i can find something i'm happy with.

jake


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PostPosted: Fri Mar 30, 2007 10:57 am 
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man, looks like you're on the same schedule as me. late to bed early to rise!! jake


something like that :roll:

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PostPosted: Fri Mar 30, 2007 12:02 pm 
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okay, one more quicky and then i've got some work to do on this amp.

on the 15 lyout and and the dc-30, there are 6 filter caps. one of them being a 22uF that goes to the v2 position. since i don't have this v2 position that 6th cap can be eliminated right? if i understand correctly, that cap is there to supply power to that tube, and if the tube isn't there, the cap doesn't have to be. hope i have something right here:)

jake


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PostPosted: Fri Mar 30, 2007 1:09 pm 
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there are 6 filter caps. one of them being a 22uF that goes to the v2 position. since i don't have this v2 position that 6th cap can be eliminated right? jake


Correct. One 22 cap per tube. Good luck!

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PostPosted: Sat Mar 31, 2007 11:56 am 
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well, i converted the filtering in my amp to that of the 15. dropped the the grid stoppers to 1.5k. i must say...i don't know if i'm just imaginging things, but it seemed to open it up a little more. i'm just curious just what the filtering would have changed, technicalls speaking, because when before i couldn't even match my other guitar players volume, since our last practice i haven't touched his amps settings. plugged my amp in and turned them both on and was just pulling the cable out of mine and putting it into his and i was definately louder. all that being said...before there was a 3x40 can cap filtering the amp. one for the ot, one for the power tubes and one for the preamp tubes. would the fact that everything got it's own filter cap resolve resolve the volume issue i was having? either way i'm happier than i was before haha :)

jake


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