Tube Amp Archive

..personally I'd rewire the preamp to something more traditional and add a phase inverter with the second little bottle. 100k anode/1k5 22uf cathode is the standard fender stage. remove the volume control from the input and replace with a 1M resistor, go gain stage->volume (and maybe tone)->gain st...

..personally I'd rewire the preamp to something more traditional and add a phase inverter with the second little bottle. 100k anode/1k5 22uf cathode is the standard fender stage. remove the volume control from the input and replace with a 1M resistor, go gain stage->volume (and maybe tone)->gain st...

Howdy folks, I'm back! I've had my nose buried in tube books and websites since my last post and trying to apply what I've learned to what I've got going on here with this record player to guitar amp conversion. Instead of asking a million and one questions I thought I'd just ask folks what they'd c...

when in doubt i look at the tried-and-true fender 100k plate/1k5 cathode bypassed by a capacitor (22uf? lower if you want less low end). volume control, some sort of tone control(s). look at schematics for amps you like or wanna try and *ahem* borrow what worked for somebody else. fortunately even ...

This transformer is Triad N-68X? It's supposed to be 1:1, but reversing it might work for you. It'll be interesting to see. The shield should work either way as it's between the primary and secondary. The iso-trans is indeed the N-68X. I've reversed the primary and secondary and the voltages were m...

Swap the iso transformer’s primary and secondary. 120 VAC input will produce ~115 VAC out. You know, I thought that there might be a vintage solution but didn't think that the solution would go back as far as "the old switch-a-roo"! I suppose the "secondary" having the shielding wouldn't matter? An...

OK, here are the first measurements on the amp: [zero signal] AC source: BK 1655 AC power supply. [Set to 120 VAC] Iso Trans Primary = 120VAC Iso Trans Secondary = 125VAC Heater string: [AC] V3 (50C5) pin 4: 118 VAC - Pin 3: 65 VAC V2 (50C5) Pin 3: 65 VAC - PIn 4: 14 VAC V1 (12AX7) Pin Pin 4: 14 VAC...

The circuit is the same. I was just looking to avoid adding an extra terminal strip by routing the 33Ω directly to the diode. Regarding what you have there now, I would run the ground side of the iso transformer secondary directly to the main filter ground. Got it. Will do. With only the speaker co...

I think I'd just reroute that 33Ω over to the rectifier and tie in the iso transformer as shown below. Hi Martin, Thanks for the input. Were you recommending moving R1 (33ohm) in series with D1? The way it's shown in the schematic you've posted is exactly how it's currently wired. A stand-off was i...

Look at the original schematic. It shows the heater string and the amplifier circuit wired in parallel. I think you just connect the iso trans in place of the original wall plug, but without the switch. The switch and fuse should be on the hot leg of the iso trans primary. I can't say for sure that...

I just ran across the image below on a site online explaining how rewiring the switch keeps the primary of the transformer from being powered all the time it's plugged in. I get it. But to do this with my amp it looks like I'll have to do a little modification to the way things are set up since R1 (...

Well, back at it! The Triad N-68X Iso-Trans is here and I've uploaded the spec sheet. The trans hook up looks simple enough: Blk/Yel-Blk & Rd-Blk /Grn-Blk are the primary hookup and Red - Red are the secondary but I'm not familiar with the "Shield" lead (white). Is it usable / necessary for what I'm...

Ditto.

Error. Duplicate of above. Apologies.

Yeah, it's the old free smak on the playground trick. I built about 14 amps over about 15 years. The last one is about 90% done and is awaiting the finishing touches...for over 3 years. I even built a nice cherry cab for it. What broke the addiction was that I got a job! Before that, I was a consul...