The Amp Garage

TNX again, Henry!

Ciao
Martin

TNX for the input, Henry! The above mentioned PT has 5V supply, and a 50 V tap on the HV winding. I thought to use the noval close to the board for PI and the noval closest to the octals as the loop tube. Whats your proposal for placing the loop tube, if I dare ask? Ciao Martin PS: I should open up ...

Well, I decided to do a Dumble variation starting from you layout, Henry! (TNX for sharing it btw ;-) I also adopted your idea to use a can cap to save some space. Had the good(?) idea to include an active tube loop. Since the chassis is quite small 35cm x 19cm (approx. 14"x8"), things started to be...

TNX, Glen for the info.

I wouldn't have expected the electrolytics to change the sound THIS much.

Looks like modern caps are to good (low ESR aso...)
Have to check it in my Liverpool /2.

Does the elco change alter the background hiss also?
The fizz cap should reduce it a bit.

Ciao
Martin

Hi!

I remember Glen having a brightness problem with his own clones.
He upped the capacitor across the two PI to solve it IIRC...

Ciao
Martin

Hi Gary! Grounding in TWs can be a real PITA. Redone it several times on my 2 hole Liverpool. Is it changing, when you pull V1? Try grounding the inputs of the gain stages from front towards PI. Even if you turn all the knobs down, there are some gain stages increasing the noise (hum). Good luck! Ma...

Well, does it behave now? I choose to have a isolated buss wire across the pots and NOT ground them via their housing. This way I can decide WHERE I ground the buss. I just solder a cable to the buss wire and check the noises of different grounding points. Btw: Debugging amp problems should be part ...

Hi Mark! TAKE CARE OF HI VOLTAGE! DISCHARGE CAPACITORS! Connect your DVM in OHM mode as follows: 1. one clip to ground. Now check w. the other tip the three tabs of the 25k pot. One should be grounded: zero ohm or very low readings 0,1 Ohm or so. Middle tab should be 0-25k depending on position of p...

Hi! Check value of mid pot. If you use too large (like 1MOhm) pots you get some kind of preampboost and less efficient controls. Basically the same effect as bad grounding. I did have some pots where the slider lost contact to the resistive surface...intermittent madness. Amp looks fine. Youre gonna...

Hi there! There's no documentation in English, but my first built was a 12 W SE (TT66, documented on tubetown.de) amp with a toroidal 2x300V and the Hammond 125 ESE. Auto/cathode bias. If you use the larger tubes (6550) at higher voltages (400+) you might prefer even a bigger output iron. 125 ESE is...

Btw: the 2k2/5 W info was given to me by Larry/novosibir...

He didn't invent screen resistors, but one has to give credit, where credit is due. TNX, Larry!

Ciao
Martin

...just for your interest the schematic of the Allen Class Act:
http://ampgarage.com/forum/viewtopic.php?t=2984&start=0

Brandon/Bludotone recommended this one as a starting point for a Dumble SE

Must be everything in those lil' tiny one cylinders...

Ciao
Martin

Hi! There are some EL84 amps w. hi plate voltage. The reliable ones take care of the fragile screens. 2k2/5W in series will be some kind of insurance for them. Zeners to cut B+ won't hurt either. The russian EL84M military version are known to withstand some punishment. They're also known to be a bi...

Hi there! One stage is not enough - it's the chain of stages making the sound... A series of two/three (not to mention the nu higain amps) triode stages with or without attenuation shapes the sound. Some rely heavily on powerstage distortion and some don't. I like to have two gain stages with differ...

Hi! It depends largely on your sound "vision" :? and a bit on your purse :D I prefer little amps w. large&loud speakers. My Princeton derivative has a 15" Eminence legend :shock: Eminence offers nearly anything. No JBLs, EVs though :evil: Eminence Tonker lite is -yes- lite, dunno if you'd like it. T...