The Amp Garage

I did an experimenting last year to find an answer to the same question: https://ampgarage.com/forum/viewtopic.php?f=10&t=36459 My experience was that the amp was a lot less stiff without feeling loose, i.e., without losing what makes Hiwatts sound and feel like Hiwatts. A lot of preferences will co...

Forgot to post this: https://www.youtube.com/watch?v=M_Uq6yzqBGQ Obviously very different amp than an AC30, and I agree with Roe that you get plenty of bass with smaller coupling cap values. I'm not sure how much of what you can hear in that video would carry over, especially given the differences b...

BTW, what do you all think of this solution? yes series might be better. note that the ac30/4 used 10nf PI coupling caps, which reduces blocking distortion and bass mud. Personally, I am using 15nf (had plenty of these caps) and it sounds great with more than enough bass for guitar. Agree with Roe ...

like for the anode mixer with separate cathodes in the first stage! Thanks! So far I'm really liking it. I'm pleasantly surprised with how there's less noise with the paralleled cathodes by how switching one side's cathode bypass cap makes a noticeable but subtle difference. It makes a big differen...

the relays are only mentioned for avoiding hum picked up by wires in high impedance paths. You are right, they will pop like a switch. Ah, yeah that makes sense. Definitely agree on the noise. I also just re-read the first post and saw you planned on a top-boost channel, i.e., will have the cathode...

I made a similar all-access type of Marshall build. Very fun learning experience, and I got a very versatile amp out of it. Problem I found is that the amp is much more versatile than I am as a player, so I usually set it up the same way, though it's nice to know that if I'm in an unusual recording ...

The build looks nice. Fine tuning is always the hard part. Thanks, maxkracht! I don't know if I would trust the footswitch function of my multipurpose input on anything remotely high gain. I have only used that in champs and other little SE amps. I haven't been using the input jacks in the fullest ...

It doesn't seem like that PT was ever capable of 350-0-350 at 200 mA. There's not a lot of headroom, and while I was playing it after resetting the bias it made a crackling sound after I started testing the filter cap switch. It's now really low on gain (clean and quiet all the way up, whereas it h...

Thanks, Martin. The OT CT sees 449V with no tubes in the amp. I currently have the KT88s biased pretty cold at 50 and 51mA as a precaution following the red plating. That's measured using 1R resistors on the cathodes, and the specific tubes in question are EH KT88s I bought used, so it's possible I ...

Re the red plating incident, at what plate and screen voltages are you running your KT88's, and at what is the OT primary impedance? Plates are currently sitting at 435V and screens at 432V. Primary impedance is 3.4K. What are you thinking? That reminded me about the still-ongoing B+ piece. I had o...

Wanted to post an update after some fine tuning: Life got busy, so I didn't have a chance to do much with it, but I have been playing it a fair bit. I could be fooling myself, or maybe it's not the factor responsible, but it does seem that there is some break-in period for the Sozos. The amp is soun...

I am very curious about the mojotone caps , didn’t know about them , thanks for sharing that suggestion Andy I've had pretty good experiences with Mojotone electrolytics, but my sample size is pretty small; I've used and installed about 5 radial multi-section cans and about another 6 axial electrol...

Do you have pictures of the guts? I suspect something is still going on with the lead dress at the input stage, especially with that JCM800 high gain section. From my perspective, changes in bad behavior depending where the presence pot gets grounded and the fact that things are worse in the higher ...

Thanks, Steve. My particular amp has about 470V on the plates after I put in the sag resistor. I was thinking with an output section that stiff, it might make more sense to approach it more like a Soldano and let the clean output section be itself. I realized today that I could also ditch the DCCF i...

Interesting that happened with the Bassman. Hiwatts are known to be particularly quiet amps, and most schematics for Hiwatt 4-hole preamps show an unbypassed 220k/2.2k input stage on the normal channel. My recent build is also the quietest Marshall-style amp I've played with that bypass cap setup, a...