Finally completed! Thanks for all you peoples help

[j-stylez]

I have finally completed building this amplifier based on the 5f6a Bassman. I couldnt have done it without all the information and help that people like here in this forum are sharing online, always helpful. Thank you!

So heres what I built:

Basic circuit is 5f6a with solid state rectification. I added reverb, tremolo, tone-cut switch, extra-gain switch, fixed/cathode bias switch, marshall/fender/no NFB switch, and a PPIMV.

All of this inside a little combo that is only 40x40x23cm. I made the front slightly slanted, the back is open. 2x6L6 WGC from TubeAmpDoctor in the poweramp, and a Sovtek 12AX7 in v1.

I removed the second channel, and used the half triode left over from v1 for making the tremolo (plus one high voltage mosfet).

The spring reverb is not driven by tubes, instead also by high voltage mosfets. I have a dwell and mix control, that gives me a very useful range of sounds.

I put a Jensen p10q in there, although that might be a little underrated at 40 Watts. I'm not cranking this amp, just using it as a practice amp at living room levels. I figure I can hook up my external cab when I want to play it loud.

Only one picture for now, but I'll try to get some more up and record some stuff.

[Chuck H]

Thanks for all the appreciation. Just send me that strat and we're square

Seriously though, nice use of SS where it could help. Neat, do all, amp. How does the p10q sound? I remember being impressed with a 12q I had briefly. I might just put a higher wattage speaker in the amp because my practical side says an amp that's built as a package should work, full function, as a package. That never stops me from plugging into other cabs though Just my own OCD on the matter.

[TomCarlos]

Congrats Julius....

The case and hardware look great. And I'm sure it sounds great too!

Tom

[j-stylez]

Thanks for all the appreciation. Just send me that strat and we're square

Seriously though, nice use of SS where it could help. Neat, do all, amp. How does the p10q sound? I remember being impressed with a 12q I had briefly. I might just put a higher wattage speaker in the amp because my practical side says an amp that's built as a package should work, full function, as a package. That never stops me from plugging into other cabs though Just my own OCD on the matter.

I agree - I dont want to think about that speaker all the time, and it would be a shame if it breaks. I'm still wondering if there is a way in which I can use the p10q fully, maybe if I add a power soak of some sort?

When I was building and before it went into the combo, I tested the amp with my 1x12 extension cab (closed back) with an eminence wizard. That was a little more sterile for the cleans in my ears. The Jensen gave it more warmth and sparkle it seems. Further, the wizard is a very efficient speaker (sensitivity is 102.8 db), while the p10q (93.8 db) is rather the opposite. I am thinking that this helps a lot, because I can now play the amp at a higher setting without it getting too loud for practice levels, and it just sounds more lively at the same volume.
It might also be due to the construction of the combo that the amp sounds a bit more lively in this combination, I used an 8mm baffle made of pine plywood, thats only connected by 4 bolts from the front.

[überfuzz]

Gratz! The amp you describe sounds cool with all controls etc, but would you care posting the schematics?

[Chuck H]

Here's an idea...

For the in cabinet speaker you could wire up a resistive divider that cuts the actual wattage to the speaker and still presents an acceptable load to the amp. So the combo, as a combo, would have a lower output. But when you unplug the internal speaker and plug into a different cabinet you'd get the full wattage. This would give you a little more volume reduction for practice so you could push the amp harder too You could use those aluminum housed resistors and mount them to an aluminum plate bolted to the wall of the cabinet on standoffs. Whatcha think?

[j-stylez]

überfuzz, yes I can post the schematic. I havent got it all documented yet but as soon as I do I'll put it up here.

Chuck H, I think I am going to try that, so that I can stick to my speaker but make the amp fully usable

[j-stylez]

However i am still busy with the les Paul I am building ATM so the schematic will have to wait a few days. I gotta say playing the AMP with a les Paul is also cool, but very different. And i will really need that dummy load with the les Paul!!

[j-stylez]

I have built the power soak as you proposed, with a 10 and 4.7 ohm resistor.
That will make my total load with the speaker attached 9.14 ohm. I am guessing that is no problem, as the resistance of the speaker varies across frequencies anyways, so that should be close enouh to 8 ohm for my purpose.

I dont have to worry about the speaker blowing now, but it seems like it changes the color of the tone a bit. Its like it cuts out some of the sparkle. Its hard to describe, and I am not even sure if thats possible, or only a result of the lower output volume when I compare with / without power soak at same amp settings.

I'm going to try it out for a bit - if it doesnt convince me I'll try the Eminence Legend 1058 next, that one should be rated high enough for my purposes.

[Chuck H]

Spot on all accounts. The missing "sparkle" isn't so much a loss of top end, but a flattening of the impedance curve. Where the impedance of the speaker is variable at frequency (as you know, and noted). The resistor isn't variable at all. And the sheer volume issue has a similar effect so it's a double punch to the tone. You could get jiggy with inductors and capacitors but the level of complexity and expense goes up a lot and the different volume level will still present it's gremlins. But then lower volume was part of the point since you'll be using it in combo form for practice and, I dunno, coffee houses?

I really like the 1058. It's a good sounding and well balanced speaker with decent efficiency. I've used several and a 4x10 cab I built for a customer sounds really great compared to anything. I will say though that the 1028k in a slightly deeper cab sounded even better. And it ought to for the extra $$$. There's really not much savings for the Legend alnicos vs. other makes. They must know how good it sounds But the 1058 is my go to "all rounder" 10" guitar speaker.

[j-stylez]

I'm just going to stick with the P10Q for now. With the 1028k I would encounter the same problem - its rated at 35 Watts. I guess its just an alnico thing that they are low Wattage speakers. Well, if i grow tired of the power soak thing (Which by the way doesnt get hot at all. I mounted it on the inside wall of the combo in an aluminium enclosure with some holes and standoffs) I will try the 1058.

[Leo_Gnardo]

I dont have to worry about the speaker blowing now, but it seems like it changes the color of the tone a bit. Its like it cuts out some of the sparkle. Its hard to describe, and I am not even sure if thats possible, or only a result of the lower output volume when I compare with / without power soak at same amp settings.

To put some zip back in your speaker you can add a capacitor in parallel with the attenuator resistor on the "upper branch" of the attenuator, IOW the one between the amp output and speaker terminal. I'd use a film cap say 2 to 5 microfarads.

Works much like the "bright cap" some like to wire onto their guitar volume controls.

[j-stylez]

Thanks for the hint. You mean across the 5ohm resistor in the above schematic?

[g1]

Yes, the 5ohm.
The drawing is "upside down" .