Starting my 12xxx build

[BAinFL]

LOL I had a 1k resistor (brown black red) feeding the PI grid resistors instead of the 10k (brown black orange). To my credit the damn red looked kinda close to orange =)

Voltages came in perfect across all of V3. Time to put in the winged Cs ands bias em.

[BAinFL]

Tubes biased up easily enough.

Fired it up...sound but very low volume output. Had to dime both the LarMar knob and front volume to get even a bedroom level tone.

Checked 470 resistor was not a 470k...OK
Checked all other resistor value...OK
Checked output selector wiring...OK
Checked connections, schematic on Lar-Mar...OK
Swapped a 4th 12AX7 into each position...no effect
Confirmed 16 ohms on selector matched my 4x12 cab wiring...OK
Front panel pots (Treb Mid Bass) are responsive to EQ changes

Searched forums for other things to test...running out of ideas.

[wrea398]

LOL I've done that before with the red and orange stripes. Now I always take a meter and check them as I'm installing them.

When you did all of your testing did you have a speaker hooked up to it. You need to have a dummy load or a speaker hooked up while testing. Some say you shouldn't even turn it on without one. Can damage an amp.


If all voltages are good it sounds like it could be the LARMAR. I would remove it and test the amp without it. I would always recommened testing against stock schematics and then ad the extra mods.

Welcome to wonderful world of amp building...lol.

[BAinFL]

This is great yet so frustrating at the same time. I can hear that sweet cranked Marshall tone, just not much or it. I could actually hear the tone improving in the short time I played as the components settled in a bit. Man, this sounds so nice. It's like getting a taster spoonful of your favorite ice cream, but not being able to eat a whole cone!!!

So to answer:

Yes - I had my cab hooked up during all phases of testing...especially front the point which I had power tubes installed and the STBY on.

I'll put the circuitry back to stock and test w/o Lar-Mar and let you know what shakes out. However, I was really careful installing and wiring it and all the points seemed tested OK when I did continuity tests. I inspected the shield wires closely and none appeared to be shorted.

The 2 things I'm most concerned about are:

1. When I had the excessive voltages on V1-V3 I'm wondering if I cooked my pre tubes? I swapped a spare tube into each position with no change, but I dont have 3 spare tubes to try.
2. Given the audible symptoms, I'm wondering if my OT is bad. Not sure how to test an OT. Suppose I could contact Classic Tone tomorrow for guidance if I cant find something here on the forums along those lines.

As always, your advice as someone who's dealt with all this before is unbelievably helpful and very much appreciated!!!

[wrea398]

If you could find someone with a tube tester that would be great! If you voltage are good now I would tend to believe the tranny is good.

[BAinFL]

Well after chasing my tail on this one, I rewired the Lar-Mar only to find that when I was done the valve in V5 was about 1/16" out of it's socket.

Problem found and fixed. The amp sounds great. I need a shower and a beer to celebrate victory!

Wrea...thanks a ton for all your help bro! Can't thank you enough for all your patience and good advice. If you're ever in the Orlando / Melbourne area please get in touch with me...the beers are on me!

So in summary (for anyone else running into similar problems on a 12000 build...3 problems with this puppy

High voltages on V1 V2 V3...bad heater wiriing
Low voltages on V3 pins 2 3 7 8 - used a 100k resistor instead of 10k feeding the V3 phase inverter grid resistors
Low output - power tube not seated 100% in V5.

Couple dumb mistakes and the only build quality thing that cost me was a heater wire which was probably one of the very first things I soldered in my amp building career. I'm happy as hell that I tried this experience and am floored by this absolutely killer sound coming from my 4x12.

OK so what am I going to build next...?

[wrea398]

Congrads Bro! Glad all worked out. Like a said, its usually something stupid. Been there..... Now that your addicted, the next will be twice as fun.

[BAinFL]

I have the biggest shit eating grin on my face. It hasn't gone away in the last hour. This is great!!!

[wrea398]

Definately a big difference in "shit eating" and "eating shit"...lol...

I have the biggest shit eating grin on my face. It hasn't gone away in the last hour. This is great!!!

[BAinFL]

Here's a quick shittly clip of me wanking lol. Shitty playing recorded thru a shitty kodak digital camera mic.

Even thru all the shittyness, you can still hear this amps character. Its sounds magical in person. This is the best I can do for recording atm...no equipment to do this tone justice.

http://tinyurl.com/3edkamj

FWIW, the amp sounds loud in the recording, but I had the LarMar at 1 max. It was most defintely bedroom levels or below. The thing sounds better when I can get the wife and kids out of the house and push some air thru the 240w cab. This is straight guitar - cable - amp - cab. Nothing in the chain at all.

[BAinFL]

I just fell in love with my amp a tiny bit more than previously.

Changed the bright coupling cap from .022 to a .0022 and wow got rid of all the flubbiness in my neck pickup on the normal channel. I can honestly say this is the perfect tone amp for me now. 33/500 with 47/8ohm NFB and it's dialled in 100% to my liking with my SG. Can't wait to get my high order bridge pickup and get even closer.

For strat/tele (and any othe single coil) players...how many of you prefer to keep the .022 value instead of the .0022?

[6burgh]

Awesome stuff Bram,

I've been following progress, I just haven't had much time to get in with help... you've been in good hand though!

I'm with you on the 0.0022u coupler after the first stage... tons of bass still there and nice and "cutting" on the neck pup. When you switch over to a strat, just bridge the two high channels with a Y cable, or even jumper 1-low to 2-hi like normal. It sounds nice and fat just playing with the two volumes, and you don't have to change your CH1 Hi setup... just a thought!

You can also try turning up the 2nd channel volume while plugged into only the Ch1 Hi. This will add "meat" back into a thin tone from the 1st channel.

[BAinFL]

Thanks for the tips Paul =) Right now I'm back to jumpering with the SG. It's still plenty thick, but the flub is gone. At first I thought it may have been the bass response of the ET65s in my cab, but after changing that cap, it fixed everything that was "too much" in the lows. I'm definitely hearing more swirl now as well since the change.

I can't wait to hear back from Jeff when my new pickup will be ready... Also picking up a Lumpy's Liquid Lead / '73 boost combo pedal. I'm not a big pedal guy but should be fun playing new toys thru the amp and seeing what tones are possible =) A cheap strat or tele under the tree this winter wouldnt suck either =) Gotta leave a few hints for the wife on that one...

[vanhalen5150]

Even with the camera mic you can hear the distinct 12000.