The Amp Garage

The "bigger cable" was probably Teflon insulated wire, that could take the heat.

The "original" uses cloth and PVC-sleeved wires, cf. the enclosed pic.

According to Suhr, EC didn't like the 4x configuration and ran 2x mostly....and yes, oddball decisions on Diaz's part. Suhr was supposed to clone that amp, not get all creative. John Suhr did a great job at making replicas - 4 have been manufactured in the first batch (well, if you can call garage ...

I'd love to see exactly what Diaz did to it. I think his recollection of the mods is somewhat incomplete. Iron from a '78 Super Twin/Showman, solid state recto, 4 x 6L6GCs, '73 Fender-branded CTS ceramic speakers lifted from a SF Bassman 100. Rewiring job, some voicing. That's all. And what in the ...

I had no idea Clapton used these amps EC uses/has used a number of very different amps, some are posing as Fender models for endorsement purposes, but *none* are standard 5E8x models. Most will be auctioned very soon, including: The '57 5E8A modified by Cesar Diaz (larger PT, 4x power tubes, SS rec...

The 5R4WGY aka "the potato masher" was designed for aerospace applications and can work in extreme conditions. Quite high voltage drop with 67 V @ 250 mA, doesn't like capacitive loads unless suitable resistors are inserted between the PT and the recto, very heavy. Datasheet of the similar -B versio...

But I've never used 5U4's, let alone two of them in parallel. What's the typical voltage drop and multiplication factor for one? How about the same for two in parallel? There are *many* different 5U4s. A 5U4G isn't the same as a 5U4GB, etc. The voltage drop can be calculated from the datasheets, fo...

Tants don't like over-voltages - some even explode. I don't use them in amps, elcos are fine in a bias circuit, they are more reliable and cheaper. BTW, the bias circuit you describe would lead to thermal runaway if the pot fails - no wiper connection, no bias, max current thru the tube. You could c...

One allows you to set bias range, the other one actual bias voltage. But you may use a single pre-VRM dropping R as well.

So if i understand i can change the 56R by a 56K bias pot ? I'd rather build a voltage divider by keeping a series R with a 25K trimmer connected as a variable resistor to ground. Tap bias at the junction of the R and the pot. Values should be calculated according to the raw bias voltage you've got...

Do you think it's a better performance in insert VVR between C1 and L or between L and C2 Not tested in a Twin. I used a broadly similar VRM in a tweed Bandmaster-like amp and inserted the VRM after C1. Works fine. If the voltage is twice filtered ,it's better ? Ripple will be lower, but the pass m...

so I don't understand why a should be add the VVR after the fisrt cap ?? The recto(s) put out pulsating DC - visualize the chopped top of a sine wave. Adding the VVR here isn't a good idea: noise-induced voltages/currents are *very* high and grounding becomes quite problematic. Shifting it to after...

the Bias layout it's ok ?

The bias section is OK. You'll have to fine-tune the 56K dropping R if post-VVR bias voltage isn't acceptable.

The VVR will see pulsating DC as it's connected between the recto and the first filtering cap. Could work but the amp will be *very* noisy. Either add a B+ filter cap between stdby and VVR or insert the VVR after C1. Don't forget to add a suitable heatsink: the mosfet will have to dissipate up to 25...

One of the thoughts behind the effort was to see if we could identify all the critical parts and obtain them for under $100. You may use a SS recto and lower the parts cost: SE amps run in class A with a nearly constant current draw. A valve here offers very little benefits sound-wise - OK, HF nois...

It's a real shame about this element of the design because they're a really nice sounding tube as far as new production goes, but suffer this problem and also are prone to massive heater hum after a period (which I work around by using DC). Same cause: poor cathode to heater isolation. Most Saratov...