Geezer's HoSo amp-Done! (for now)

[John]

Okay, putting holes in the chassis right now, but have a question about the dual gang pot for the PPIMV. First, it is audio taper, correct? And, where do I find them? I tried turretboards, mojotone and AES (although I could have just missed 'em).

 Or, could I use the 1meg that Doug sells and use say, a 1.5meg resistor instead of the 2.2?
Or is that just stupid and makes no sense at all?

One more- The T-5879 that AES sells is good for the first preamp, correct?
http://www.tubesandmore.com/scripts/foxweb.dll/catalog@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?PAGE=SUBCAT&SEARCH_TREE01=ZCATALOG&SEARCH_TREE02=2009010

Thanks in advance!
** I first posted this in the schematics forum, but thought this one gets looked at more often. If the mods want to move it back to the schematics, that's fine too**

[Geezer]

1st.....what schematic are you using?

250kA dual pots here>

http://www.mouser.com/catalog/catalogUSD/643/726.pdf

http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV24BF-10-15R1-A250K/?qs=R1h7DEsyLZi9EhQqk47wow%3d%3d

The T-5879 that AES sells is good for the first preamp, correct?

Yes, that's the one.......

[John]

I'm using the 2/3/11 one, (attached) and intentions  are to follow Doug's layout. (also attached)

Thanks for the mouser link!

[Willabe]

Is the wire connection from E1 to E2 on the turret board correct?      

Would'nt that short out the FX loop jacks?


        Brad      

[Geezer]

Is the wire connection from E1 to E2 on the turret board correct?      

Would'nt that short out the FX loop jacks?


        Brad      

No, not if I understand your question correctly.

I have attached a layout highlighting the actual E1 connections in red.....does that help?

If you wanted, you could use a shielded wire directly fron the relay 1 E1 connection to the send jack E1 connection.....that's actually what I do.

BTW, Tubenit drew this layout, so I'm just now familiarizing myself with it just as you are!

G

[Willabe]

My mistake, I thought E1 was indicating the turret to the right of it as being E1. I can see now that E1 is a turret itself.


          Brad       

[jojokeo]

Everytime I see the input drawn like below it keeps reminding me of a famous cartoon character

[John]

Okay, wiring stuff up. I'm putting in 3 speaker jacks, 1 each 4, 8, 16 ohm. My question is, should I use shorting jacks, or the  normal speaker jacks? Does it matter? Also, I'd like to add a "safety resistor" to each one, *just in case* I'd ever fire it up without a speaker plugged in. Can someone point me to a schematic addressing that?

Thanks in advance!

[Tone Junkie]

John this build has always kind of intrigued me just the way Geezer used the 5879 tube. so keep us posted and give us more amp porn to look at  Ok Im a slut for amp porn I must be getting old. from many of the discussions If I remember right the consensus was just shunting your speaker jack to ground was just as effective as resister but as always I yield to those with much more knowledge than I they just hadnt answered yet.
Thanks Bill

                                             


you gotta love these things

[Geezer]

I'm putting in 3 speaker jacks, 1 each 4, 8, 16 ohm. My question is, should I use shorting jacks, or the  normal speaker jacks? Does it matter?

Yes it matters.....don't use shorting jacks, or you will be shorting your OT 2ndary to ground. Just use non-shorting type speaker jacks, leaving the un-used 2ndary taps floating.

[John]

Geezer, thanks! I almost installed shorting jacks before the lightbulb went on and thought I'd better ask. It made sense to me to not use the shorting jacks, so maybe I'm finally learning.

ToneJunkie, you'll get no amp porn from me. I doubt I'll ever do the nifty work I've seen here!

[John]

Work progresses, and I have another question. It's about the foot switchable relay. After much reading of various threads here and elsewhere, this is what I *think* is right.

Using Doug's 5 volt relays, I simply use the 5V heater wires from the PT (Heyboer). I wire them to the shorting jack. With footswitch "off", there's no current, with it "on" there is and the flips the relays. With those relays, no need for capacitors to eliminate "pop" when switching, no diodes or other stuff.

Can it really be that easy?  Seems too good to be true. 

[sluckey]

Doug's 5 volt relay has a DC coil. You'll still need to build a simple dc power supply.

[John]

Ok, thanks. I was thinking the 5v tap from the PT was DC already.

*edit* don't even know why I would think that, I just did. Anyway, ordered the parts for the power supply. I dream about this stuff at night... is that normal?

[sluckey]

I dream about this stuff at night... is that normal?

You bet!

[Willabe]

I dream about this stuff at night... is that normal?

Yup. I do too, sometimes.


         Brad        

[John]

Question about the footswitch for the relays; I just use the normal 3 tab shorting jack that Doug sells, right?

Also, is the Marshall 1-button footswitch that he sells the one I want?



Sorry to be so clueless, but I have zero experience with that stuff; I've never had such a fancy amp before. :)

[John]

It's Alive!!!

I started swapping screen and cathode resistors to get the voltages somewhere close to what they should be, but the bugs descended on me, and I thought flinching while checking voltages is probably not wise (work bench is out in the old loafing shed). But I'm tickled to death! Nothing shorted, the light bulb didn't burst, and smoke did not pour forth.

Thanks to everyone on this forum; without this message board and Doug's nearly one-stop shopping, I'm sure I never would have attempted this.

[Tone Junkie]

Cool John congratulations on a fine new build .
Bill

   

[John]

http://www.el34world.com/charts/valve/ValveData.php?e=view&f=11322
5879 tube voltages: pin3=.91 pin7 = 67 pin8=160 pin9=.91

Okay, I need some help! Even with everything dimed, I get very low volume. Bedroom volume, you'd probably call it at most. No distortion at all, no gaininess either, just nice clean low volume. I know I messed up somewhere, but danged if I can find it. I've been messing with it ever since I jumped the gun and pronounced it alive.   

Here's what I've double checked: every value of every resistor and cap, the connection from the input jack to the V1, and the wiring of the pots; both on the schematic and the layout. Also swapped out all tubes with new ones, no difference.

Due to dumbness, I fried the relays by mis-wiring my power supply, so that may be getting signals crossed? If they fail, do they fail closed, or just sort of "float" the contacts? Right now I have them in the sockets, and I'm assuming they're in the NC position.

ANY ideas, suggestions and even criticism will be appreciated. I've run out of ideas! I'm going to order the relay parts again, but meantime I thought I'd throw this out there and see if there's not something dead simple I'm missing.

I know the voltages are too high, but I thought I should figure out the volume problem first.

Thanks!

[tubenit]

My advice would be to back track and get it working withOUT the relays. And then see how that sounds?

I'd just hardwire first using just one gain and one trim. IF that works fine and it's loud, then add the relays.

With respect, Tubenit

[John]

Thanks for the advice, I think that's exactly what I'll do!

[John]

Okay, hard wired the "trim1" and "gain 1" as you suggested, and if anything it sounded worse, so tracing out the schematic yet again, and found what was probably  my original mistake! I had gotten the C D and E nodes mixed up! My C node was not being filtered at all, and the D node was feeding the 5879, plus I had  the (IIRC) 8 pin connected straight to the D node without going through the .001/56k like it was supposed to. And this AFTER I had traced everything... obviously, I hadn't traced it often or thoroughly enough. It's a wonder it made any sound at all!

Anyway, the amp sounds fantastic! It's so cool being able to get that gainy sound without actual distortion, I love it! All I have to do now is tinker with the cap values to get less of the bass coming through; I need just a bit more treble out of my humbuckers for a few songs. If there's something else I should look at first, of course let me know!

Also, I think instead of re-wiring the relays, perhaps I should use the chassis space for putting in the resistor and cap on the PT center tap as was discussed somewhere a while back. I've got 395 volts coming off the PT.... then again, if I just swapped out the SS rectfier and put in a 5Y3 that should help that a lot too, is that correct? Don't worry, I'll hook up the heaters to the socket first. 

ANY comments or suggestions, as always are very welcome to me. In case you can't tell, I'm happier than a tick on hound right now!

[jojokeo]

All I have to do now is tinker with the cap values to get less of the bass coming through; I need just a bit more treble out of my humbuckers for a few songs. If there's something else I should look at first, of course let me know!

ANY comments or suggestions, as always are very welcome to me. In case you can't tell, I'm happier than a tick on hound right now!

Yikes, I discoverd a tick on the front of my shirt a couple of weeks ago - first time ever I've even seen one alive and in person and ON ME! Freaked me the f-out!
Congrats on your amp! You've just been bitten by the tube amp bug, and like a tick it'll dig in deep and start sucking away at you. I think Doug encloses one free of charge w/ every first order made to him!? >:)~

For your quiestion of more highs/clarity: start w/ a couple 500pF caps across the pots next to the ppimv/master volume, 100pF & 250pF's can also be used. Higher value = more treble signal bypassing the 1M pots. Also you can do the same w/ your early gain pots but these are usually turned up more anyway to varying degrees & negates the caps' need here. This will help greatly but you'll notice a little more hiss in background when more vol is used. This is the rub of the green and you'll have to make compromizes for noise vs clarity/treble response when controls are not all of the way up.

[tubenit]

I've got 395 volts coming off the PT.... then again, if I just swapped out the SS rectfier and put in a 5Y3 that should help that a lot too, is that correct?

[John]

Thanks!

[John]

Okay, got it closed up at least for now. The 5Y3GT dropped the voltage far more than I expected it to, so I'm puzzled about that. Attached is the updated schematic, with voltages too. I'm thinking I should try a Sovtek instead of NOS in the rect. tube spot.

For this version I didn't  re-install the relays; I like the sound as is, so I'll save the more complicated stuff for the next build. The ONLY thing I can't figure out is how to get rid of some of the "bassiness". I was able to  improve it by adding some caps across the pots, and messed with a few of the other cap values too, but I've still got the treble pot dimed while playing. The amp sounds fantastic, don't get me wrong! Love being able to dial in the gain and all that, I just know I've missed something along the way.

I'm going to do some more reading on tone stacks,  and mess around with Duncans calculator some more, but in the meantime if anyone wants to point out the obvious to me, that's great too. 

Much thanks,
John

[tubenit]

I can't figure out is how to get rid of some of the "bassiness".

Get rid of the .047 coupling caps between the LTPI and the EL84 tube.  Use .02 or .015 instead. 

That should do it. 

With respect, Tubenit

[John]

Tubenit, thanks!

*edit* Side note, I do have a lower value filter cap already ordered, I know the 47uf is way too big for the tube rect. Also, reading Merlin's article, it seems I could just swap the 22 and the 47 if needed.

I am learning about amps the same way I learn about everything... I just go ahead and do it and learn (make mistakes) along the way. Then, when I'm done I know just how I should do it the next time.