Tube Amp Archive

Really glad this build came together! Last little weird thing is that on the Marshall channel, when bringing the tone pot past 3/4 of the way up - the channel seems to lose a little volume. My research suggests that this is a perceived change that is actually the mids and bass being reduced to such ...

Had this old amp that I used to gig with a long time ago and am getting it out of storage. For some reason I thought it was from 1976 but the serial number ends with "F," denoting 1974. I bought it before I knew much about amps, so I was pretty surprised when I opened it up in terms of what was stil...

Almost certainly less compression. The signal swing won’t be as large since there’s less amplification, so less bias shifting effect as the CF’s grid becomes more positive and draws more grid current. In addition to the Blonde/Brown Bassman, Hiwatt SAP’s also use a CF immediately after the input gai...

No issues. Lots of amps use separate cathode resistors (e.g., Vox AC100). If the cathodes are fully bypassed as shown, there shouldn’t be a discernible sound difference aside from possible variation in the output tubes’ operating point because of differences in the actual values of the resistors due...

Not sure about the answer to number 1, but I think if your HT fuse is spec’d appropriately your PT should be safe. To know the time constant, I think we’d minimally need to know what specific capacitor(s) you plan to use (or their ESR) and the HT secondary resistance of your PT. That’d be a simplist...

This is easy to do with a voltmeter by paralleling it across the Rk's or a series 1R. A current meter has to be inserted (or pre-inserted shorted and then un-shorted), not something I see a way to do using a single center-off DPDT. This seems like the easiest and most reliable solution. If you're d...

Really interesting thread. I'm curious how Mikante's cab turned out. I've been flirting with the idea of trying to tune a 2x12 to a frequency matching that of a closed 4x12 with some heavy-magnet Greenbacks (I'm sure I'll be the first to try to blaze that trail...).

If you go to the thread linked on the first post you'll find the schematic at the bottom of the first post.

I’ve read so many conflicting things about Page’s relationship to Orange. My understanding is that the “Orge” head in the 70s was used for the theremin, but I truthfully haven’t really looked too deeply in terms of whether it was sometimes on guitar duty or in terms of what amps he used after LZ. Wa...

Sundragon redid their site once they released the Nymph, and I'm noticing that the new site has manuals posted which are quite informative. Specifically of interest, it alludes to the amp having a bright cap: "Because of its unique circuit, the amp will become brighter as you lower the Volume contr...

Sundragon redid their site once they released the Nymph, and I'm noticing that the new site has manuals posted which are quite informative. Specifically of interest, it alludes to the amp having a bright cap: "Because of its unique circuit, the amp will become brighter as you lower the Volume contro...

Almost there. The cap needs to filter the new node, so it should connect to the other side of the 5K1 resistor. So I'd just reverse the jumpers' positions. Something you could test while building is to have it without the added filtering stage to see if you encounter stability issues with the stock ...

- Should the B+ jumper go to the 100k/100k junction of the V2 plate resistors? - Swap the 47nf cap over to share the turret with the 10nf? - Understood on the preamp filter, I was wondering about that in the original design. Is it as simple as putting it between .022uf and .68uf caps, running the B...

I seem to prefer smallish output coupling caps in my own designs, but have a Bassman with 0.1uF output caps and it isn't too tubby. This has also been my experience with 100nF couplers coming out of the PI. IMO it really depends on where your amp is running into issues. I agree with Martin about th...

New layout looks great! The order of components makes good sense. I did catch the jumper connecting connecting the plate of Marshall side's input gain to B+ appears to be mis-routed to the Hiwatt input gain stage's plate. The 47nF cap off the Marshall's input gain stage also appears to be on the wro...