New SLO 100 clone

[M Fowler]

Starting soon on my SLO 100 clone.

Chassis, boards, knobs by C3Amps

Mouser order for some caps and resistor values I didn't have.

Vactrols from Doug Hoffman Amps

IMG_1125.JPG

IMG_1127.JPG

IMG_1128.JPG

IMG_1129.JPG

IMG_1130.JPG

[M Fowler]

Ordered transformer set from Heyboer $340 shipped:

PT 100w Heyboer HTS-9741
OT 100w Heyboer HTS-9740
Choke 10h Heyboer HTS-9743

IMG_1131.JPG

[pompeiisneaks]

damn that chassis looks great, I really need to start getting chassis that are premade instead of my home made horror show ones.

~Phil

[norburybrook]

are the Vactrols for the trem?



M

[roberto]

No, they are for channel switching.

[M Fowler]

I'm think of building a Weber chassis version next, probably not a Weber kit they really suck in the transformer, board and components department.

The Weber 6SX chassis is what guys used to use back when for SLO 100 builds. Besides it has depth pot hole on front.

[roberto]

What I consider really useful addons to a stock SLO power amp are:
- the depth control (standard 4n7//1MOhm isn't bad);
- the "focus" control, to call it à la Rivera (a 250k log pot in series with the 39kOhm feedback;
- change the 25k lin presence pot with a 10k lin one.

That makes the standard slo a real versatile amp.

[M Fowler]

Thanks Roberto.

What I want to do is build my first SLO 100 stock, then use the Weber 6SX chassis to build another SLO 100 with all the bells and whistles.

Mark

[roberto]

Mark, I agree with you.
One stock slo built as close as possible to the original one, and then another to play with.

[Rockwell666]

My biggest complaint was the effects loop on my SLO build. (depth is 100% required for hi gain tones). I would put a switch on the back with a 1uf cap parallel on the loop recovery cathode for a gain boost to use pedals and not line level effects. besides that I still regret selling my clone. The SLO has the tightest, clearest more responsive gain ive ever tried. and that was a clone!

[Phil_S]

are the Vactrols for the trem?

That was my first reaction. I see Roberto answered. I have looked for the Vactrols that work for tremolo. To the best of my knowledge, they are no longer made. You might get lucky and find a stash somewhere. When you do, buy ALL of them. I expect old school amp builders like us will take them off your hands. I can tell you that the incandescent-LDR bug makes for a great tremolo. This is different from the Fender "bug."

To be clear, most modern Vactrols are LED based. From what I have gathered, getting the LED to turn on and off to make the tremolo work is not a suitable solution for older, classic amp designs. What we are really looking for are old Vactrols made with an ordinary incandescent bulb and an LDR in a tidy package. With the traditional tungsten filament bulbs on the way out, manufacturers dropped production of this type of optoisolator at least a decade ago and then the old stock dried up PDQ. Of course, it is easy enough to build one with a bulb, an LDR, and some black heatshrink tubing. The trick is to figure out which bulb and which LDR constitute the right combination. I have never been able to find the spec for the optoisolator in my old Gibson GA20-RVT, which would really have answered the question about a home brew optoisolator. I was extremely lucky to locate a suitable replacement about 10 years ago when I did all the research to find what I needed. I suppose if I hadn't found a viable part, I would have gone to the trouble to make one by trial and error, but I did not warm up to that idea.

I have some notes from 2002-2003 from when I posted my issue in a forum frequented by engineers. One guy was kind enough to bring the discussion along to a good conclusion. In the end, he suggested home brew by trial and error would (see above) be the best way to get the part.

If someone will design a tremolo circuit for a modern LED Vactrol, that would be terrific. I do not have the chops to get this done and I don't know if it is possible to make it work. Alternatively, if someone will take the time to make a home brew incandescent-LDR model that actually work for tremolo and share the findings, that would be just as terrific.

Apologies for side tracking the thread.

[roberto]

Hi, led based ldr are here since early 70s.
You can clearly mimic the lamp behaviour by slowering down the response (by a RC net, for example).

[fishy]

Interested to see what you think of the transformers. I used the Onetics and had no regrets at all despite the cost.
Kinda have to build one to appreciate how good this amp is.......

[M Fowler]

I ordered the Heyboer set and it will be a while before they show up.

[norburybrook]

are the Vactrols for the trem?

That was my first reaction. I see Roberto answered. I have looked for the Vactrols that work for tremolo. To the best of my knowledge, they are no longer made. You might get lucky and find a stash somewhere. When you do, buy ALL of them. I expect old school amp builders like us will take them off your hands. I can tell you that the incandescent-LDR bug makes for a great tremolo. This is different from the Fender "bug."

To be clear, most modern Vactrols are LED based. From what I have gathered, getting the LED to turn on and off to make the tremolo work is not a suitable solution for older, classic amp designs. What we are really looking for are old Vactrols made with an ordinary incandescent bulb and an LDR in a tidy package. With the traditional tungsten filament bulbs on the way out, manufacturers dropped production of this type of optoisolator at least a decade ago and then the old stock dried up PDQ. Of course, it is easy enough to build one with a bulb, an LDR, and some black heatshrink tubing. The trick is to figure out which bulb and which LDR constitute the right combination. I have never been able to find the spec for the optoisolator in my old Gibson GA20-RVT, which would really have answered the question about a home brew optoisolator. I was extremely lucky to locate a suitable replacement about 10 years ago when I did all the research to find what I needed. I suppose if I hadn't found a viable part, I would have gone to the trouble to make one by trial and error, but I did not warm up to that idea.

I have some notes from 2002-2003 from when I posted my issue in a forum frequented by engineers. One guy was kind enough to bring the discussion along to a good conclusion. In the end, he suggested home brew by trial and error would (see above) be the best way to get the part.

If someone will design a tremolo circuit for a modern LED Vactrol, that would be terrific. I do not have the chops to get this done and I don't know if it is possible to make it work. Alternatively, if someone will take the time to make a home brew incandescent-LDR model that actually work for tremolo and share the findings, that would be just as terrific.

Apologies for side tracking the thread.

Phil,

The Demeter Tremulator pedal uses a Vactrol, it was built for Ry Cooder. I made one hence me asking about the use on thsi amp. It's nice trem but it looses a bit of highs and drops the volume a bit so I don't usde it much. It's entirely possible I didn't do a great job on the build as it's on TAG board and I haven't got the technique 100%.

Marcus