Tube Amp Archive

Swapped the 10n cap input to OD section with 2.2n - like how it is less fuzzy / bassy now and if you want that fuzzier sound you can still find it by turning up the back panel OD (input to v2a) and down v2b.

Re:. Output transformer - with so much feedback in the output loop does the quality matter much? Real question - I'm guessing the feedback (if power section is played clean) will make anything half decent sound good. All bets are off once distorting power section though I put a 2.2n cap across the O...

@Reel thanks for the update. I'm curious - does the deleted 10n cap before the OD section cause any popping to appear when you switch from clean to OD? Been playing with the amp (as in with a guitar, not changing stuff) a good bit and have really found a groove where I like what its doing. Totally d...

Nice! I'm looking forward to hearing how it comes out. I put my v1b local negative feedback on a switch today (sacrificed the manual preamp boost switch). There is a real difference in the amp though a non-guitarist probably wouldn't hear it (it is a bit louder but in talking tone). Best way I can o...

I mentioned before I took some direct measurements of frequency response and distortion of the amp - here's what I did and the results. Setup: - Focusrite Scarlett 18i20 interface used for I/O - Output of scarlett into input of amp. Amp into custom load box (has circuit inside which is the electrica...

One thing I'll put here, but really it should probably be its own thread, is that I did some modeling of LED bias and how it would compare to bypassing a resistor with a large capacitor. The reason I modeled it was, at first blush, it seemed like a large bypass cap with resistor and LED (of same bia...

I don't think I've posted this yet - response curves of the grid stopper / cap combo with feedback: resp_curves_v1b_feedback.PNG Ok a bit of explanation - this is my modded version with the tone stack later, made into four identical copies in ltspice and with some tweaks made to each. In every one t...

Another benefit of cutting the feedback - those two huge resistors (40 meg total going by memory) have to be adding some noise - will see if I can pick up the difference if I cut it

Yeah it is hard for me to see ever using the jazz setting. I'm sure I could change around the tone controls to get a usable setting but...why? I'll measure it all and we can look at it, but not seeing jazz used in my future and want that switch real estate to be used for something else useful (like ...

Your experience dropping the local nfb makes sense with what modeling says - the cap / resistor parallel combo on grid of v1b is actually a treble shelf (cut), but then add the feedback and because resistance is higher in bass frequencies across those components you get more feedback in the bass, so...

Aha nice! So basically you felt like removing local nfb on v1b was an improvement? How did it impact the amp? Breaks up a little easier when clean? Did it sweeten the breakup or change the character? My next mod is to put a 100k log pot as variable resistor in series with the feedback resistor on po...

@Reel have you started working on your amps? How did they sound with a tube change? We just had a baby so going to be pretty sparse on the posting for a while - hoping to get more clips up soonish

If you get a minute to post some audio I'm curious to hear what yours sounds like stock. It is interesting that it is almost a dead ringer of that other D schematic (183? On my phone not looking) but neither of ours sounded great stock...

@Reel I'm very interested to hear about your journey with the amps. Few questions: - How many copies do you have? If more than one do they all sound the same? - Have you changed the tubes yet? I was surprised how much of a sound difference that made in my (used) copy. Not sure how it sounded new or ...

One more idea - you could bias V1b hot or cold so it is out of center - will break up easier