Rosamp SLO 30 build

[Giorfida]

same reason I can never be bothered or motivated to use/add bias test points to a chassis.

is it really that hard to take the chassis out once every 10 years? meh.

also bias test points are kind worthless to me since they don't tell you plate voltage (imagine having a test point for that lmao ) cathode current over 1 ohm resistors isn't enough information on it's own.

(and i don't use that method anyway, i just use the "OT resistance method" - measure volt drop from OT-CT to anode/plate (over the resistance of the same test points to get plate current)

Biggest complaint I have with most “bias probes”- you still need to crack the chassis to adjust anyways… I get that they keep leads from the dangerous bits, but as a builder that don’t bother me. Second complaint I have is that they don’t read plate voltage, which w/o plate voltage, current reading is useless. Tangent: my annoyance with folks on Internet forums throwing around bias current numbers for amps, but none around dissipation (watts) or even plate voltage.

I still use OT shunt (only works with decent meters)- set meter for mA, then measure directly across ct-plate. Pretty much the same thing (still have full potential of power supply going through leads).
Never thought about measuring the OT DcR and using the volts scale- it would essentially limit the current flowing through the leads (less likelihood of cooking a pt, OT or both if you slip a lead to ground), and plus- don’t have to switch between meter scales when alternating between reading plate voltage and dissipation. I may have to try this next build! Nice!!!

 

[Asdrael]

Between you, @jjjimi84 and @KindCanuck + my constant Soldano GAS, I might actually go for a Rosamp build as a first big electronic project... Do you rekon it's doable with limited experience? Luckily I have access to very decent equipment in a workshop so at least that part of the equation should be good enough.

 

[TillMack]

Between you, @jjjimi84 and @KindCanuck + my constant Soldano GAS, I might actually go for a Rosamp build as a first big electronic project... Do you rekon it's doable with limited experience? Luckily I have access to very decent equipment in a workshop so at least that part of the equation should be good enough.

@Asdrael tough question. The documentation is really well and nearly like painting with numbers, but you have to be really serious about the fact that handling with high voltages is really dangerous.
The soldering on its own is not the problem. The tough part is firing up the amp the first time. If you have any issue with that cause you made a fault while building the amp you really have to know what to do. You would not be the first person who had to visit a hospital while touching a capacitor which is still loaded with high voltage.
So it's hard to tell and give you a good answer.
If you are careful and take your time it's definitely a kit which can build by someone even with less experience.
But you really have to know some things about working with tubes and high voltage.
The build is really straight forward. If you take your time while cabling everything together and be careful while biasing the amp it will work.

 

[Asdrael]

I appreciate the answer thanks a lot. And congrats on the build it looks great!

I guess I will build a few pedals and see how it goes first. For the amp itself, I have started reading/watching stuff about tube amps and safety. The only mod I feel like I want to have in is external bias points and adjustment,which should "simply" be rerouting of a few cables. After all, I managed to build a perfectly fine guitar from a few youtube vids so I guess I have it in me somewhere to build my stuff

 

[TillMack]

I appreciate the answer thanks a lot. And congrats on the build it looks great!

I guess I will build a few pedals and see how it goes first. For the amp itself, I have started reading/watching stuff about tube amps and safety. The only mod I feel like I want to have in is external bias points and adjustment,which should "simply" be rerouting of a few cables. After all, I managed to build a perfectly fine guitar from a few youtube vids so I guess I have it in me somewhere to build my stuff

@Asdrael the Mod for Bias points is a bit more tricky than you think. You also have to put some resistors in series to the bias points.
And to be honest, if you not change the power tubes every week you don't need it.

 

[Asdrael]

True. And Gruß aus Tübingen

 

[TillMack]

@Asdrael
Wenn du noch fragen hast, dann schreib einfach eine PM, dann kann ich dir helfen.
Shot me a PM if you need any further help.

 

[Giorfida]

Between you, @jjjimi84 and @KindCanuck + my constant Soldano GAS, I might actually go for a Rosamp build as a first big electronic project... Do you rekon it's doable with limited experience? Luckily I have access to very decent equipment in a workshop so at least that part of the equation should be good enough.

As mentioned before, safety is #1.
Can it be done as a first amp project? Absolutely!
Would I recommend it? Personally, I always recommend a few lower gain builds first (tweed champ and deluxe, maybe a tweed bassman or plexi Marshall etc) to learn good lead dress habits/troubleshooting ground issues/oscillations etc. high gain amps add some complexity as the gain makes oscillations possible if not careful, and of course every gain stage etc you add, is another chance for ground hum to show up. And obviously the more complex the circuit the more involved troubleshooting will be.

That said, if you are fully aware of the risks and possible complications you may encounter and are still set on it, I’m confident you can be successful. And I also know there are a number of us here who are only a post/email away if you get stuck!

 

[Asdrael]

As mentioned before, safety is #1.
Can it be done as a first amp project? Absolutely!
Would I recommend it? Personally, I always recommend a few lower gain builds first (tweed champ and deluxe, maybe a tweed bassman or plexi Marshall etc) to learn good lead dress habits/troubleshooting ground issues/oscillations etc. high gain amps add some complexity as the gain makes oscillations possible if not careful, and of course every gain stage etc you add, is another chance for ground hum to show up. And obviously the more complex the circuit the more involved troubleshooting will be.

That said, if you are fully aware of the risks and possible complications you may encounter and are still set on it, I’m confident you can be successful. And I also know there are a number of us here who are only a post/email away if you get stuck!

Hey thanks for chiming in (and sorry @TillMack for the hijack ). The issue is that I play mostly high gain stuff and I am not that keen on building something I won't use and probably never manage selling. Tough enough to justify to the wife why I am closing on on 10 guitars and a few amps in this 8m2 computer/music room... at least the heating system is off here.

I'm binge watching some videos on tube amp construction and safety now. There is also a guy that made a video building this particular kit ( HERE) and another one that did a series on a kit derived from a RobRobinette schematic ( HERE) so I have some content to go through before I take you up on that gracious offer of being one click away

 

[TillMack]

@Asdrael
As already mentioned, the Kit is totally possible if you have some soldering experience.
Everyone who started a high voltage project gets some experience from everywhere. I build one U87 clone mic and then made my first M49 tube microphone clone. So if you feel comfortable with it, then do it!
Have no fear but be respectful. And I totally understand you. I also just play high gain stuff and the bands I record also just play really heavy rock and metal. So also for me it made no sense to build another tube amp then a SLO clone.

 

[bechbox]

Welcome Till

Besides pedals I've also built a couple of the Gyraf projects (the genius Jakob Erland behind Gyraf is a local guy here in Aarhus, Denmark), so maybe it's time for me to finally build an amp as well

Did you order directly from Rosamp? And is it compatible with EU voltage or did you have to mod the original build?

 

[TillMack]

Welcome Till

Besides pedals I've also built a couple of the Gyraf projects (the genius Jakob Erland behind Gyraf is a local guy here in Aarhus, Denmark), so maybe it's time for me to finally build an amp as well

Did you order directly from Rosamp? And is it compatible with EU voltage or did you have to mod the original build?

Hey !
Jakob is an awesome guy and really helpful ! It's crazy that he shares his knowledge for everyone !

Yes I ordered directly from Rosamp. They are in Italy and the power transformer is compatible with nearly every voltage in the World.
Just check the Rosamp page and take a closer look. I think you have the same voltage in Denmark like here in Germany (230vac) so it will definitely work.

 

[bechbox]

Ha - I was thrown off because it says "USA" all over the page. I didn't realize it's the product category and not the location https://www.rosamp.com/product/slo30-kit-nt/

Yeah yeah, same voltage here in DK as in Germany, so all good. Must start to save some money for this

 

[TillMack]

@bechbox
I paid roughly about 1200-1300€ for everything. Tubes are super expensive ! My Soldano-style front grill was also really expensive. So I think you can also get everything together for something like 1100€ if you not so picky like me.