Tube Amp Archive

I got the Small Special in operation today. Fired right up with no issues. I havent plugged it into a proper speaker cabinet yet, just a 12" speaker that hangs on the wall in my shop. but it sounded real nice even thru that. I wound up using a 1k5 nfb resistor with a 50k pot so it is variable & I al...

Great to hear youve got an amp you get along with now. Ive only built 1 JTM45 in 25 or so years of building & I cant remember all the details I never did get along with it so I sold it. Rob Robinette has a lot of mods & tweaks for the 5f6a which most would apply to the 45 & at the bottom he does go ...

Seems like a typo. Should be 3.3K to match the schematic. 5w is not necessary there. 1 or 2 watts will be fine. This is what I was thinking but I saw the post above by Dorrisant and in his pictures you can see his was built just like the layout, which, I think, would add a ton of negative feedback....

I have a question that im sure someone can help me to understand. On the layout above what is happening with the negative feedback? It is different than the schematic, there are many differences, but why is a 5 watt resistor required there? I dont recall ever seeing such a value in a negative feedba...

Has anyone built this version of the Small Special? I was going to build a scaled back version, 6aq5 or el84 , but I have Iron on hand for the 6L6 so Im going to build it as shown here. I see some difference in the schematic vs the layout so I guess im looking for some direction, suggestions and or ...

I've that exact thing happen. Because there was no "squeal" as one normally would experience, it took some time to figure it out. Same here, no squeal just loud humm. I dis connected the negative feed back first just to verify, switched the primaries & all was well. Glad you got it going. I Love mi...

I added a 220k resistor on the send pot & it made a big difference in the right direction, Im thinking of changing that pot to 1 Meg. Should I do anything to the return pot? . . All the voltages are right in line with whats on the layout, I did try jumping the 10K dropping resistor to up the voltage...

Using an AT7 helped a little but not much. I want to get a good bit more out of it before I call it done. Does anyone think changing the 100k send & return pots to 250k or beyond will increase the signal to the reverb tank? I changed the 220k grid resistor on v2 to 470k & again it may have been a li...

I have finished my Wonderland build & have built it a very nice Maple head cab which awaits its final tweaking. The amp fired right up with no real issues, after swapping the OT primaries, it didnt squeal but rapid speaker oscillation occurred, swapping the OT primaries corrected it. The amp sounds ...

Wow - Looks like a lot of planning & for thought went into this one, I just got done shoehorning a Wonderland into a 17" chassis & your build makes it seem like I had plenty of room. I can see where those cap cans would free up a lot of room but your still going to have a full house there. Cant wait...

Thanks for the info, Once I got to looking around Ive seen where several people have built this amp with EL34s & loved it! I dont have any old pinball machines laying around but I do have enough spare parts to put one of these together without one. , I think Ill stay away from the ultra linier & jus...

I have some decent doner Iron from a Seymor Duncan Convertiable amp that ran 4 EL34's. I was wanting to get opinions on how best to use it in a JM Wonderland amp with reverb. I have attached both the Wonderland schematic and the SD schematic. Would I be best off using EL34's? I dont see the primary ...

The power trans is a P-T290DX its 325-325 @ 200ma, I used the 5v tap for the relays. . The Output is a Magnetic Components Classic Tone 40-18001. I already had the 4ohm one but I got this because In a head I wanted to have the option of diffrent cabs. Tx - Joe

The 2 Tube 102 Ive been working on fired right up, bias was set all the voltages were well with in range. I pluged it into a 2x12 cab & it was immediately apparent that something was not right. All the controls & the boost & OD worked just fine but it just sounded bad with awful overtones and distor...

The LNFB switch on this layout- seems to just ground the negative feedback circuit on V1. Is this a good way to do it? Would it be better to put a switch that diconnects it? And lastly what affect does it have on the tone, sound, feel of the amp? . . Sorry , I could not finda a schematic that shows ...