Introducing "The Kitchen Sink" submini amplifier

[Ripthorn]

Well, i was doing some more tweaking last night and found that with the 470R resistor in series with the gain pot on the boost, the max gain got really mushy and nasty.  So I ended up playing with values and found that a 15k in series with the 100kA pot gave a max gain that was still high, but nice and tight.  I think I am going to play with the cathode resistors in the high gain section to see if I can get even a little more definition out of this.  I should have preamp schematics by tonight.  I am also thinking I might make a couple clips of what it sounds like with my tone stacks that I have (a james and a diezel VH4).  Any comments or suggestions are welcome.

[Renegadrian]

Nice work Ripthorn - go ahead and have fun with that sh.t!!! 

[Ripthorn]

Okay, here is the schem for the clean section and the bax tone stack.  You will note that the output goes to tone select 1a, which is one half of a dpdt switch.  This is so that you can select which tone stack will be used for the clean channel.  A similar switch is implemented for the dirty channel.  The output of the tone goes back to the dpdt switch, so that only the output from the used tonestack goes to the volume control.  Hope you guys can use this or find it interesting.

[Ripthorn]

And for those of you who wanted to see pics, this is what it looks like right now .  I have actually rearranged it so that it all fits on one breadboard, but I'm too lazy to take a picture of that.  I am still trying to decide what holes I want in the chassis I made.  Once that is done, loading it up shouldn't be too bad.

[svstee]

Wow, I'm impressed! can't wait for the master schematic (if you are willing to share, that is).

[kurtlives]

Haha nice! Your breadboards look similar to mine when I have a crazy tube project on the go.

[frequencycentral]

Sweeeeeeeeeeeeeet !!

[Ice-9]

Thats looking very interesting, very neat voltage multiplier on the 1st breadboard and i love to see those croc clips in these breadboard test builds. Keep us informed of how it goes. Looking forward to a sound clip when your ready.

[Ripthorn]

Wow, I'm impressed! can't wait for the master schematic (if you are willing to share, that is).

I'm more than willing, it's just that I am putting it up in pieces for now because the free version of eagle cad only allows one page schems, and the master will take much more than just a single page width.

@Mick, there are some soundclips in post 6 or 7.  I have managed to make the background noise much quieter.  I will put up new soundclips in the next few days, I think.

[Ripthorn]

Well, I put together the power amp on the breadboard earlier today and tried it through the celestion in my 25 or 30 year old marshall combo.  Sounds pretty good, though there is some high frequency fuzziness that comes through that didn't when I used just the preamp.  I may have to play with the power amp design or I might just need more voltage (plates were all at 40V).  I need to buy the parts for my nixie supply so that I can see what some high(ish) voltages will do.

So Rick, any ideas of what can be tweaked in a pp power amp?  I have 33k resistors to grid 3, 1k cathode resistor and 1uF cathode caps.  Maybe I was just driving the power tubes into some undesirable distortion.

[frequencycentral]

Well, I put together the power amp on the breadboard earlier today and tried it through the celestion in my 25 or 30 year old marshall combo.  Sounds pretty good, though there is some high frequency fuzziness that comes through that didn't when I used just the preamp.  I may have to play with the power amp design or I might just need more voltage (plates were all at 40V).  I need to buy the parts for my nixie supply so that I can see what some high(ish) voltages will do.

So Rick, any ideas of what can be tweaked in a pp power amp?  I have 33k resistors to grid 3, 1k cathode resistor and 1uF cathode caps.  Maybe I was just driving the power tubes into some undesirable distortion.

Maybe you can clean up the high frequency fuzziness with a couple of grid stopper resistors between your cathodyne phase invertor and the 5902's. The bigger the value the more HF is cut. I'm curious as to how much oomph you're getting with just 40v to the plates. I'm going to try two 5902's on my Sub Zero breadboard this week, so I'll let you know how that goes. Bear in mind that grid 3 is internally tied to the cathode in 5902's.

[Ripthorn]

Hi Rick, with the 5902's at 40V and fully cranked, the volume is about as loud as a TV that is too loud for normal listening.  I just need to up my 1044 multiplier, though it seems to be giving me less and less additional voltage with each stage.  After two stages I have 34V and after four I have 41V with a 12V input.  Hopefully soon I can crank this up again and see what I get.

[frequencycentral]

I set up two 5902 in PP today, using 47K at grid 2 (I don't have any 33K right now), 1K and 47uf at the cathode, and running at 145v. I used the preamp/inverter stages of my Sub Zero to drive it. Very clean. I found that it is possible to get a little more gain by changing those 1K for 470R or 100R, but this seemed to excessivley load the SMPS, the voltage dropped by about 20v and the bench supply kept tripping out. I ran my Valvecaster through it - shockingly loud actually. What ratio are you calculating for PP into 8 ohm?


EDIT: On refection, I think the bench supply kept tripping due to the sheer amount of stuff hooked up to it. Two 7327 heaters in series, two 5902 heaters in series and the SMPS. The heaters add up to 750ma alone, the bench supply is 1.5A. I guess the combination of the PP loading and the SMPS was trying to pull more that teh bench supply could give. That SMPS is certainly power hungry.

[Ripthorn]

Hi Rick, I am using a Hammond 125C for my OT and am using lugs 1 and 4 into 4 ohms, which I think comes out to about 5.8k primary.  I did lugs 1 and 5 (I think) into 8 ohms which is approximately 5.6k primary.  I tried with plate voltages at 65V and got a significant increase over the 40V arrangement, I can't wait to see what 150V will do to it.  Unfortunately, my clean volume was so much lower than my distorted, but with all the bells and whistles in this thing, I should be able to equalize out the volume pretty easily.  The clean channel at max gain with max boost gives an incredible crunch tone.  I love to switch my PRS into single coil mode and play Fire by Jimi.  I will have to make more clips.  I think I am only running 1 uF on the 5902 cathodes.  I may have to increase that and see what happens.  I added the grid stoppers, but not too much effect, I will keep tweaking, but I think some of it might have to do with the fact that my speaker is not the best.  I really should get my cab out...

[Ripthorn]

Okay, I think this needs an update after 3 months of nothing.  This would have been done much sooner, but a month or so ago my three month old boy took over full time occupation of the room where my soldering station and the like is.  That mean that the 3 hours worth of work that I had left took several weeks. 

As an additional note, I had to trim back some of the options since I found that some didn't want to play nice with others.  For example, the tonestacks can be bypassed, but not switchable (i.e. I can't route the clean channel through the dirty channel tonestack) because that would require even more relays or similar.  The cab sims are external, because it is amazing how much space the vital functions took up.  Anyway, enough babeling, the thing sounds great and the background noise is barely audible on the dirty channel and only a near issue when I have the boost and the dirty channel going, but what do you expect with 5 gain stages?  Here are a couple pictures of it finished.  I used waterslide decals for the labeling and I built the cabinet out of mahogany with cherry and flame maple accents.  I will try to get sound clips up soon, all  my recording equipment is in that back room and I never have a moment alone in this house, what with two little ones and all.  Sorry the pics are so big.

[Br4d13y]

That looks amzing man . Great work! Makes me wanna go build one!

[Taylor]

Wow, that's beautiful. Very, very nice job. What are the overall dimensions, roughly? I love watching these tube builds - would love to do one myself, but I always chicken out when high voltages are involved.

[doitle]

Those little tiny tubes ended up in that gigantic head? Looks great. I can't wait to hear some more clips since the ones on the first page are broken links.

[kurtlives]

Nice work!

I really would love to see a finished/finalized schem.

Also a short explanation of all the knobs and switches would be nice.

[Ripthorn]

I will work on getting the schem up and current, but as for an explanation of everything, here we go:

Boost: switchable triode boost based roughly on the subcaster
Channel: switches from the initial 2 gain stages to 4
Gain I: clean gain
Gain II: dirty channel gain
The four switches between gain and the other knobs were for tonestack switching, but two of them aren't wired right now, the other two are for bypassing the tonestacks

Treble I and Bass I: a passive baxandall with gain recovery
Treble II, Mid II and Bass II: a Diezel tonestack

Eleven: gain pot for the boost stage
Lead/Rhythm switch: switches out the resistor between cathode bypass cap and ground in the boost stage (makes for a flatter boost over frequency, but also less umph)
Volume I and Volume II: volume controls for the respective channels

Fat knob and on/off switch: This switches on a low frequency boost like that in the Thor and DieFET

Presence: Negative feedback loop a la Fender and Trainwreck amps

Master Volume: Self Explanatory
On The Back Panel

Footswitch jack, effects send/preamp out, effects return/power amp in, impedance select

The dimensions of the chassis are 3" tall, 18" wide and 7" deep.  The overall cab is 19" wide, 8 1/2" tall, 8 1/2" deep.  I will try to get the clips recorded and hosted on an easy site as soon as I can.