The Amp Garage

... was hard not having any good low voltage AC sources at home. ... You can make yourself a low voltage AC source with any old mains PT and a high-wattage (e.e. wire-wound) rheostat. PTs from discarded transistor amps are good for this because they have low secondary VAC to start with, and then yo...

I'll keep this short since this is not a dead cow I care to milk any longer. You know those days you should have just stayed in bed? Yup. Here we are. So, rig 120vac up to the transformer in what certainly appears to be standard fashion. Check everything, all is safe, white to white, black to black...

Yeah, I’d remove the tubes and secure them separately in a little padded microphone hard case in my carry-on luggage.

Hi Steve

I’ve enjoyed our chats on various forums over the years, so you’re not allowed to leave.

I measured the plate voltage at 360 6K6 || 6K6 Zout = 360V/(17W/360V) = 7,624R (~8K 10W SE OT is close enough) 12SN7 Zout = 360V/(7.5W/360V) = 17,280R. A little Fender Reverb transformer (17k - 25k) is probably ideal. Or a small 4k:2R SE OT with an 8R speaker, or 8k:4R OT with a 16R speaker. the ch...

For centre-bias class A operation, the nominal reflected load can be ballparked by: Zout = Vp/(Pmax/Vp) Where: Vp = plate idle voltage Pmax = Max plate dissipation For tubes in parallel, sum the Pmax first. Using this formula I get 5k3 for 6K6 || 6K6 @ 300V (each 6K6 is 8.5W Pmax) 12k for 1 x 12SN7 ...

Tube swap?

Any suitably-rated* electrolytic capacitor should suffice. Mouser** usually has plenty of choices

*voltage, capacitance

**www.mouser.com

Thanks everyone for the info. I'm feeling a little better about the socket now that I know there are options. I was thinking about a 6Sxx of some kind and that was going to be my next question but you're way ahead of me. 6SC7 is another suitable preamp octal tube (with gm and mu resembling a 5751) ...

What Phil_S said.

Except don’t just have big amps for playing out and little amps for practice at home, I say ‘why not have a range of little big and middle sized amps to reflect your mood?’

At startup, when the filaments are cold, they will draw more than nominal operating current. So using a 10A fuse on the heater winding is not so daft.

My grounding scheme is as follows: All pots go to the buss bar which is grounded at the preamp star ground All cathodes from the pre amp, reverb driver and recovery at grounded at the pre amp star ground Input jacks use isolation washers and are grounded at the pre amp star ground Rca jacks are gro...

I think there is still a ground loop or cold solder joint somewhere Ground loops are a nuisance in reverb circuits (because the S:N ratio is particularly important in the recovery stage). Where have to got the reverb recovery stage grounded? (I presume you've re-flowed all the joints?) My reverb re...

Bombacaototal wrote: ↑Tue Aug 20, 2019 9:29 pm I think there is still a ground loop or cold solder joint somewhere

Ground loops are a nuisance in reverb circuits (because the S:N ratio is particularly important in the recovery stage). Where have to got the reverb recovery stage grounded?

(I presume you've re-flowed all the joints?)

So did you turn the pan around so that the output transducer was away from the PT end of the chassis?