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Discussion in 'Shock Brother's DIY Amps' started by zorgzorg2, Sep 19, 2020.
Homemade eyelet board!
Made a detuned 1x12 cabinet this week!
So, I have this old squier sidekick amp, with a 6-ish inch speaker in it. The impedance is 4 ohms and I suspect the wattage to be 10w. I had the idea of putting thus in the amp head, but the blackvibe circuit outputs 40w iirc. Would the attenuator circuit from robrobinette.com work here?
To be clear, I'm referring to this mod https://robrobinette.com/Generic_Tube_Amp_Mods.htm#Quarter_Power_Switch
. Using the 4ohm wire from the transformer, and then a 4R in series and a 8R in parallel. Would 25w resistors be enough in this case?
Hmm, I read somewhere that 4ohm will want to output double the wattage of 8ohm, so I guess I need to attenuate even more, right?
Most builders prefer the 10% Power Switch mod. For a 2x6L6 Blackvibe I would suggest using 50w resistors. If you want to use this with a 4 ohm secondary then change the resistors to 6 and 8 ohms.
Alright, I finally got all the parts, and am planning the top layout of the amp. The idea is to have the small speaker in the middle front, hence the space between the choke and the ot.
tubes from left to right are rectifier, two power tubes, pi tube and preamp tube.
I haven't done the headphone test yet, but I'm wondering if the ot is too close to the inputs (bottom right). Any issues you see with this layout?
I was wondering: if I have a master volume, do I really need an attenuator? As long as I don't push the master too high, I should be fine with the lower wattage speaker, right ?
Started soldering stuff... Boy it takes time!
Now I just have to connect the main board I think.
I think I'm finished soldering everything except the internal speaker! Here is the final schematics.
As long as you don't turn the master up too much you will be fine with that little speaker.
It is alive!!!!
I followed Robrob's instructions for starting up the amp with a bulb limiter, and discovered a bad connection at the C filter cap ground. Fixed that and the rest went really smoothly.
The wires hanging are connected to the small internal speaker, and it works! Now I just have to find / build a speaker cable to connect the big external speaker
If I hear one more blackvibe!!!!! Dangit!!!
Ima havta buildit!!!
Watch this space, mate......no guesses as to what is happening on my bench at the moment
You may have to start ordering parts
@D'tar haha, yeah go ahead, it sounds awesome.
I just played it a bit on the big speaker, wow... I'm a clean sound lover, and I'm really happy about cleans here. The overdrive comes a bit too early to my taste, but that might be because I got 6l6wgc power tubes
Alright, done more playing on it. I really love this amp! (was playing on a fender mustang modelling amp before, no comparison possible. Somehow a tube amp I sooo much more sensitive to the playing.)
The sound is amazing, and it is dead silent when not playing after warmup! No hum, no hiss, no nothing.
However, when warming up, it crackles like an old vinyl, unless I have the master volume turned all the way up. Anyone know why?
How long into the warmup are you talking before it subsides?
You have to guess a tube would be the likely culprit here, I don't know what to make of the master volume thing though.
I'm talking maybe 10 to 15 minutes?
I googled a bit, some recommend spraying contact fluid on the tube pins. I'll give that a shot in the morning.
If you get no crackling with the master volume full up then I would definitely re-flow the master volume joints (pot and wires). Another set of power tubes would also help troubleshoot.
What type of master volume did you add?
I could be way off, I'm really just trying to test my own understanding here... Could the crackling have anything to do with the power tube bias voltage being on the MV pot?