18Watt.com

I've went through variations and tweaks on my 18 watter and when I added the Heyboer it seems like the amp has lost volume and distortion. Any ideas on what that would be? Did something fail simultaneously with the OT install? Tube voltages read correctly.

Thanks,
Ross

P.S. I did simultaneously add the post-PI MV off this site but that is wired correctly. The amp works well but what the volume was with the Hammond 1608 on 2-3 is what the Heyboer is on 6 or even higher.

Ross,

I would suggest you first bypass the MV to verify that the OT is indeed working correctly. Then if the amp performs correctly, reinstall the MV and see where it goes from there.

I will try that tonight and see what happens. Some of what I would call the "grit" is gone along with the volume. The tone is still nice, just much different than what I believe it should be. But all I am comparing it to is how it sounded before...and the real deal that I played through once. But I am not A/B'ing anything. I'm just playing from memory. However, as all of us regular players know, you start to resonate with the tone you dial in to and know pretty well what the touch/tone/sustain factors are from session to session. I'll report back.

Thanks,
Ross

I bypassed the MV and found it to respond quite different. Much better, in fact. However at 6-7 the amp is too loud for the practice environment. So at least that is a different issue. But it brings me back to other questions. This is an amp that I converted from a Spitfire. Very simple conversion. The only difference is I left the 5AR4 in it, the Matchless-style MV and I stepped the voltage down on the plates to 320V. Otherwise it is the exact circuit of the Lite II. When I put the Heyboer OT in it I changed over to the MV posted here with the dual-gang pot and grounded lug, etc. So know I'm wondering...

Does anyone have first-hand between these 2 different MV's? It seems like the second one resists more. My Lightning smokes (not literally)...and that has the shorted-style MV. Maybe I need to change back to Matchless style and see what happens.

I also added an extra 33uf filter cap and big resistor to step down the voltage from 360V to 320V. Did I hurt myself here to? I understand the headroom loss and all but how about the filtering...too much do you suppose?

And finally...I read some posts about an attenuator you were using...Weber MASS...was it? Is that the REAL way to go?

Thanks for any and all help,
Ross

I would say your loss in volume could be because of this change

Is it possible that someone could explain why this would be? Actually, with this voltage reduction change and the shorted-style MV there wasn't a noticable volume difference but the headroom shrunk some (which was fine at the time). I think I will go back to the higher voltage tonight. But that MV...any takers? Do I just lose a lot of signal regardless of what MV I use?

Ross

Thanks Richie. The OT is hooked up correctly. I do think it is the MV style that is giving me the difference. It just acts like it pinches off more signal and leaves it cleaner than the shorted-style MV. I did bias the tube based on the plate-cathode voltage (but the biasing happened before the hammond so it was an apples to apples thing just short of the MV and the Heyboer). The EL84's are running around 12W. I am going to let the voltage run back at a higher level and just remove the MV for a while and see if I can take it from there.

Fun stuff!

Ross

I removed the power resistor and let the plate voltage rise to 332V. I also removed the MV. There is a noticable difference in quality of volume and tone. It is a great sound when it is cranked up. I am either going to go back to the crossline style MV or might try the Ken Fischer style pre-PI type.

Besides that everything is hunky dory. When I first turn the amp on and it is warming up there is a repeating sound somewhere between a ting, tick, and a pop. Not loud...and it goes away after about 1 minute. Is that a bad solder joint or something? Bad Cap?

Thanks,
Ross