The Amp Garage

It turns out the diode string was weak. I used 3 UF1007's per side with .01 caps in parallel. I tore them out and used a temporary pair of 1n4007's with all the same filter caps and dropping resistors and got 459 VDC. Go figure. Unfortunately I had to destroy the rectifier caps to get them out so re...

Well SWT, looks it's just you and me. Maybe I can help you with your question. Those series filter caps and the resistors that run parallel to them help smooth the ripple while converting AC to DC. They are also handy in the first stage to deal with spikes and on-rush current during start-up. Withou...

Hi Guys; I am wrapping my first amp in this style and have run across an issue I haven't seen in other amps. I am using a Heyboer Marshall JTM PT that has 700 VCT. The schematic is along the lines of the Skyliner redux (HRM S3988009.2) but with a boost. No jazz or deep switches. Under load it can on...

Without adding too much confusion, here is a link to the circuit I mentioned above. This is some very cool information on Marshall tweaking so it has a lot of merit beyond the pedal idea. If you look at the footswitch, you see that the relay is grounded through an LED across a small resistor. The re...

I have done or seen this done a couple of ways. There was a Marshall channel switching link that is still around that shows the LED going to ground in parallel with a small resistor -- I think it was 47 ohms. That way the LED only pulls as much juice as it needs. Use Ohm's law to get the right resis...

I looked into cloning a Magnatone 280 back when. The hitch was that a repairman who specializes in those amps had cornered the market on the diodes they used. I would be interested in knowing if someone has come up with an alternative or if the supply has freed-up. That is a true vibrato or pitch sh...

Can't help with the Magnatone trem but many moons ago I built a stand-alone trem using the brown Fender (G-A) trem. This was the last one before Fender started using the roach. The tremolo uses five triodes so the sixth was used to create the line signal. It is a complicated circuit but is really co...

I'm not sure you will see 420 on the plates. That is the theoretical voltage. When all the tubes are in you are probably looking at more like 400VDC. That is a good voltage for those tubes but they will sound a little browner than in a DR so adjust your components accordingly (i.e. slightly higher v...

There is a little trick you can use to make drilling aluminum and plexi-glass/lexans easier. Those materials would rather be scraped than cut. Mill a slight back bevel on the edge of the drill bit. Imagine that the edge normally has about a 55 degree (to vertical) bevel on the back and 0 degrees on ...

I've got a spare set. Different sources give different z-outs on these tubes but they should be close enough to use with 6L6 iron. Thoughts are welcome.

Thanks, Skip

Power: Matchless Export model from Angela. 680 or 733 at 300ma. Don't know if it is current or NOS from the 90's. Incredible build quality but too heavy for a 50 watt amp Output: ADA (also defunct) 4k primary. Got some cheap a few years back. This is my last one. Choke: Hammond rescued from the famo...

An old guitarmaking trick is to align the two parts and then fold a piece of low-tack masking tape (the blue or purple stuff) along one long edge. Open it like a book, spray the adhesive and fold it shut. This can come in handy for doing tolex too.

Skip

This goes in the good to know file. I just got a power transformer for my next project from Angela. It is an NOS Matchless unit. It weighs in at 12 lbs and puts out either 680 or 733 VCT at 300 ma along with 5v and 6.3v taps. Laydown style. What is so noteworthy is the build quality. Very tight mach...

Hi All; Does anyone have a schematic for switching between the hot rubber monkey mode and the Hybrid A amp? I've sketched one out but it involves a 4pdt switch and tearing apart a couple of dual-gang pots. A related question is, "Why doesn't the Skyliner use (or need) the local NFB loops?" Any help ...