New project

[EKDENTON]

I'm starting a new  pp build. Hoping this will be a nice amp. I have heard that the 6AQ5's sound much like the 6V6. Should be around 8-10 watts. I have the 6SL7 tube in a previous single ended 3 watt amp build, and I do like the sound of that tube.

[kagliostro]

I think you are a bit high with B+, datasheet say max 250v for the 6AQ5 (phisically it is a small bottle respect to the 6V6)

however may be you can use it with that voltage (a bit less life)

The preamp on the schematic is the same you have on your SE amp ?

No cathode resistor on the first triode of V2 ??

Franco

[EKDENTON]

That's probably not the voltages that i will run it at. Every tube in it has a normal operating voltage of 250v.  I just forgot to delete the voltages. It will probably be around 240-245v. I have a torroidal transformer that has 175v taps that i kinda wanted to try but if not i will probably just use a dc power supply that i can adjust the voltage with the turn of a trimmer pot.


No on the single ended amp preamp. This one is much different. The single ended amp had one 6SL7, This one has two and the first two triodes are parallel like the matchless. Also this one has the shape control design from the Orange Dark Terror. Just a little minor turn of the shape makes a large difference in tone. Full clockwise cuts a lot of mids and counter clockwise allows more mids and less highs and lows to pass. At least that is how the amp i tried sounded to me.


This is just an experiment. I'm not even positive it will make a good amp LOL


I did do some changes on that single ended 6K6. I swapped the 6K6 to a 6W6 , changed the screen resistor size  and moved one end of the screen resistor off the B+ and to the plate to lower the screen voltage. It sounds much better now but does its best with a 4ohm speaker load. I just use my bass amp speakers with it now. Sounds great.

[sluckey]

No cathode resistor on the first triode of V2 ??

I bet that's just a drawing error.

[sean_thornton]

6AQ5/12AQ5 will run quite happily at 300 volts (more than this will make them unhappy), so don't worry too much about that. If you are providing around 275 to 300 volts to B1 you will be fine.

[EKDENTON]

No cathode resistor on the first triode of V2 ??

I bet that's just a drawing error.

yup, let me go back and see what i did. LOL

[EKDENTON]

Okay here is the correct photo. LOL, i have too many photos in the folder I loaded the wrong one earlier.

[DummyLoad]

I think you are a bit high with B+, datasheet say max 250v for the 6AQ5 (phisically it is a small bottle respect to the 6V6)

however may be you can use it with that voltage (a bit less life)

The preamp on the schematic is the same you have on your SE amp ?

No cathode resistor on the first triode of V2 ??

Franco

bogen K10 runs with 310-320V to the plates with auto bias. i wouldn't hesitate or worry about using 305V.


--pete

[DummyLoad]

IMO, 6SL7/5691 sound much better with a colder bias. experiment with 150-220K Ra and 2.2-3.9K Rk. if you do use those suggested values, then you'll need to drop Rg1 (100K) by 1/2 to 1/4 or better to keep from shaving off highs.


--pete

[EKDENTON]

IMO, 6SL7/5691 sound much better with a colder bias. experiment with 150-220K Ra and 2.2-3.9K Rk. if you do use those suggested values, then you'll need to drop Rg1 (100K) by 1/2 to 1/4 or better to keep from shaving off highs.


--pete

I have studied just about as many amps with 47K and 82K as i have 100K on Ra, and originally I had a 100K drawn in at Ra V1,but this is why I chose 82K to start out with.

The 12AX7 has an internal plate resistance of around 80K(without the external sheild), the 6SL7 has a little more than half that at 44K.


If you just go by that data a 44K resistor would match impedance on the 6SL7 best. (a 44K may not produce the best sounding guitar amp though)


Also there is another thing to consider on V1.... everything is in Parallel.  One resistor is for both plates, and the R/C on the cathode is for both cathodes.


Soooo someone may correct me on this but with the the triodes in parallel the internal resistance would be .....using Mr. Ohms law....around 22K.


So in effect an 82K on two plates in parallel would be about like 164K on one plate.


Hopefully that explains Ra at 82K. 

[EKDENTON]

I'm actually thinking a 47K on Ra may work better than the 82K but i may try it like this first and see what i get.

[EKDENTON]

It has been pretty busy for me lately but i was able to make some progress on this amp. I did make a couple of changes so i will post the updated preamp drawing, and the parts layout. I think I have it correct but....it is easy to make mistakes on drawings, so if anyone sees anything out of place let me know. Some of the under board wires are hard to tell where they go but i tried to line up the wire in the direction it heads under the board and the colors should let you see where they go if not the schematic will show where they go.

[EKDENTON]

Finished the cnc tool path for the turret board today. Gave it a name.

[purpletele]

It has been pretty busy for me lately but i was able to make some progress on this amp. I did make a couple of changes so i will post the updated preamp drawing, and the parts layout. I think I have it correct but....it is easy to make mistakes on drawings, so if anyone sees anything out of place let me know. Some of the under board wires are hard to tell where they go but i tried to line up the wire in the direction it heads under the board and the colors should let you see where they go if not the schematic will show where they go.

EKDENTON,

Can I ask you what program you are using for your drawings?

Thanks,

BV

[EKDENTON]

Sure, the schematic and layout is a freebie program diylc. You can Google and find it. The one of the turret board is a motion control software that just gives you a preview photo of what the cnc router will cut. It is a $600+ program specific for operating CNC machines.


I may have to go up one size on my PT to a 200v, so the 175v that is shown now may change.... Still a work in progress.

[EKDENTON]

I cleaned up a few mistakes on the drawing above and replaced the photos to the corrected drawing so that the layout agrees with the schematic as far as i can see. I changed the PS first node past the choke. It probably was not necessary but we will see what it sounds like. It did take the 25 volt ripple off the plates of the 6AQ5's. By shifting that tap past the choke on the power rail  i probably will need to increase the size of the choke i use. Originally i had bought a 50mA. The next larger that I have laying around is a 120mA so i guess i will use it.


Below is the PSU i ran. The photo above shows 245v on the plates of the 6AQ5's . That is incorrect, a closer voltage can be seen on  C2,C3,C4 and C5 in the PSU program results below.

[EKDENTON]

I finished the board, all the under board connections, and the ground wires on the board. I used black micarta this time. I don't like it as well as the fiberglass but it works. I hooked the wires onto the turrets so that later when adding parts and the solder flows the wires do not drop out.

[EKDENTON]

Some progress....

[EKDENTON]

I have the filaments, the PT, and all the board connections wired.  I tested the filaments and they are all working at 6.5vac. The secondary winding is reading 179vac. Pilot lamp works.  So far so good. I have the board mounted where it goes now. I realized i forgot to put the 1M resistor at the input jack on the layout drawing that i posted earlier so i added that and I will re-post the correct picture once i get it up and running and have no other issues.

[TIMBO]

Looks great.

[EKDENTON]

The Ace High is finished and operating as it should. It is a very nice sounding amp. I like it probably more than i do the 6v6 plexi and the Orange Tiny Terror. This is my first amp that I designed myself with no help on the design. I do like the shape control from the Orange Dark Terror so I did use that circuit for my tone control. All the way left gives a scooped mids sound all the way  right is bright and shimmery. In the middle is a lot of tone change to play with. I like to keep my amps simple so chose a single input and paralleled the first two gain stages on V1. I wanted to design an amp that does not cost much to build, so i chose the Antek Torroidal Transformer with a 175v secondary $37.50. I really liked the sound of the 6SL7 on the little 3-1/2 watt practice amp. They are the octal version of the 12AX7. The Premium NOS tubes can be bought on ebay for about the same price as the current production 12AX7's. To me the 6SL7's seem to have a thicker sounding distortion. I think they sound better than current made 12AX7's. They also make an excellent Phase Inverter tube. I've been wanting to try the little 6AQ5 tubes which will do approximately 10 watts in a PP amp. These NOS premium amperex or other brands can be bought cheap on ebay. So i designed the power amp around this tube. It just happens that the 6AQ5 and the 6SL7 tubes both call for 250v on the plates on the tube data sheets. So i designed the power rail so that after ss rectification the voltage would not drop much along the power rail. The B+ is 247v. I did find a few mistakes in my first layout drawing and have corrected those in the final drawing. The bass seemed just a bit loose when i first tried the amp so I changed the first bypass cap from a 25uF to a 10uF and replaced V1 with a 6SN7. It sounds much better now. It has a bit of fender type sound with the shape full counter clockwise but also can sound much like a Marshall when full clockwise on the shape. I think it may become one of my favorite amps. I really was not expecting it to sound this nice right off. If anyone decides they want to try one of these amps and needs the chassis dimensions or any other info that i have not listed just let me know. I did not save receipts but i think I built this one for under $200

[sluckey]

That turned out very nice. I especially like the clean board layout. Is that your artwork?

[EKDENTON]

Thanks Sluckey, it is. With  the way everything turned out I have a nice large space on the front left side of the amp to put the amp name and maybe some cards fanned out with an ace high. I think I will just bend a heavy aluminum plate to create a hood over the tubes then just a plate or plexiglass to cover the bottom of the chassis.


It has a very low noise floor. May be due to having the components all close enough together so that the leads are all fairly short.

[EKDENTON]

After playing this one a bit I did another modification. I changed the cap after V1 from a .1 to a .0047. That improved the sound tremendously. It tightened up the bass very nice. The distortion sounds better....smooth....creamy. Still has a nice amount of bass response. Clean sounds much better also. I think it is done!  Posting the final preamp schem.  with the changes and the photo of the layout with changes.