Another Toroidal PT AC30 clone

[lord preset]

I answered my own question re. the 220K resistors by trying them - no difference. I also know that the hum is 120hz as per the scope. The hum does not go away when V1 and V2 are removed but does go away when the PI is pulled. I have the pots and preamp grounded to a lug below the input jack and the power supply and power section grounded at the opposite end of the chassis.

[Roe]

one 220k resistor has minimal function after the cathode follower. but adding another 220k for mixing different channels will reduce the gain w. 50%

[lord preset]

I was able to knock the hum down a fair amount by pulling the unused 4 and 16 ohm OT wires out of the chassis and cutting them as short as possible (still enough length for a splice if needed later). There is still a fair bit of hum but it's tolerable to me. The next issue was that the TB channel was WAY gainier than the Normal channel with very little travel on the volume control before going into overdrive. This behavior is nothing like my previous build off basically the same schematic. I have tried a number of things to little effect: 1) adding a 220k/220k voltage divider before the coupling cap going into the PI; 2) removing the 22uf bypass cap on V2A; 3) changing the V1B cathode resistor to 2.2K; and 4) changing the 220k plate resistor on V1B to 100K. Finally I removed the cathode bypass cap on V1B which, by itself or in conjunction with all the other changes finally toned things down a bit. I am still puzzled why this build is so different than the 1st.

[lord preset]

All done. It turned out that the source of the hum was boneheadedness, as in the failure to ground the output jack. Came in at 32 lbs vs about 50 lbs for my Hayseed 30. I will live with it for a while and might go back and return to some of the stock values I changed to tame the gain. We will see.

No the amp is not upside down in real life, and if you click on the pics it won’t be. What’s up with that?

[pompeiisneaks]

lol dunno some kind of bug with the forum software, when it makes the thumbnails they are upside down or even sideways sometimes.

Sorry about that.

Love the AckAck!

~Phil

[lord preset]

So I discovered why the TB channel was so loud. A 100R slope resistor instead of 100K will do that . This upside of my goof is that it motivated me to install a PPMIV which works really well even though the dual pot only just barely clears the tube sockets in the cramped chassis. On a final note, my plan to make the amp light as possible was foiled when I tried it through the Weber ceramic Blue Dog in my Hayseed 30. It sounded much much better than the Celestion Century Vintage neo speaker I have installed. Grrr. New Blue Dog on order. I've used the neos on other amps with success but sadly not on this one.

[Guy77]

Great looking amp! I like how the grill cloth matches.

I also always end up with Alnico speakers in my personal builds (Golds) .
The Blues are great too, my friend has one in his Tweed Deluxe.

Cheers

Guy

[Colossal]

Great looking amp! I like how the grill cloth matches.

I also always end up with Alnico speakers in my personal builds (Golds) .
The Blues are great too, my friend has one in his Tweed Deluxe.

Cheers

Guy

Guy,

Do you like/use a single Gold or pairs with your ACs? Yes, a Blue in a Tweed Deluxe is fantastic.

[Guy77]

Hi Colossal. Actually the amp was a 30 watt Rocket that I built a while ago from the layouts here on the site. It's now dismantled and waiting to be transformed into something else but not sure what yet lol.

I ran the Rocket through my Traynor Dark Horse 2x12 cab that is loaded with a Celestion Gold and a Celestion G1265 . I know the speaker wattage was overkill for a 30 watt amp but I always like the tighter sound you get from larger wattage speakers.

The Gold is amazing with the cleans and the G1265 is great with the overdriven tones!

I really like that combination they sound so good together and they are not so heavy for my back since the wife is always redecorating and I am always shifting my gear around!

Cheers
Guy

[Roe]

some prefer the 220k mixer resistors yes. and adding screen resistance may help with higher voltages

[Colossal]

Hi Colossal. Actually the amp was a 30 watt Rocket that I built a while ago from the layouts here on the site. It's now dismantled and waiting to be transformed into something else but not sure what yet lol.

I ran the Rocket through my Traynor Dark Horse 2x12 cab that is loaded with a Celestion Gold and a Celestion G1265 . I know the speaker wattage was overkill for a 30 watt amp but I always like the tighter sound you get from larger wattage speakers.

The Gold is amazing with the cleans and the G1265 is great with the overdriven tones!

I really like that combination they sound so good together and they are not so heavy for my back since the wife is always redecorating and I am always shifting my gear around!

Cheers
Guy

Thanks Guy! I know what you mean about the tightness. I am planning an EF86 or 5879 front end with an AC30/4 power amp (have transformers, but working on a couple of other amps at the moment). I often play an 18W Lite type amp with a detuned 4x12 with a pair of 20W Greenbacks. It is a fantastic, open sound with a piano-like quality which is very touch sensitive. The detuned cab really evens everything out the speaker, lending way more apparent girth and punch, and separating the midrange of the Greenbacks. A single Greenback in a small cab such as an 18W gets a bit cluttered in the mids for my taste (although it's killer when it's singing away). I like a little more separation while staying warm and fuzzy, but not distorted. I like the interaction of the touch sensitivity of the amp and low wattage speakers. Just get the amp cooking and the Volume and Tone knob on the guitar does the rest. I did try a pair of Scumback G12M and G12H paper voice coil equivalents at 65W each and they are very, very good. For what I am doing at the moment, the 20W Greenbacks win out very slightly. At the volumes I play, they are a little sweeter perhaps and wake up a little sooner than the 65W speakers. But sonically, they are very close. For the AC30/4 build, I may swap in a Blue with one of the Greenbacks, or two Blues, if necessary. But considering the Gold as well. A Blue in a Tweed Deluxe is pretty spectacular so there is always a need for a Blue.

[lord preset]

For me speaker choice is always a matter of compromises. In a hypothetical world where I had more money and roadies I would probably use Celestion Blues or Silvers for everything, in 2x12 or 4x12 cabs. But a single 15w Blue is not going to fly for an AC30 and I have never been happy with 2 x el84 circuits - not enough headroom and depth to the sound vs 4 x el84s. Back when I was not playing out I had a Goodsell 33 combo with 2x12s that had a stunning clean tone in my home studio. But after resuming gigging I realized it would never leave the house (too heavy - too pretty)and reluctantly sold it. So the 50W Weber Blue Dog is the best compromise I have found so far for a single 12" combo in the 30-50 watt range. It does not sound like a real Blue but it has many of the same qualities that I like about them.

[Guy77]

For me speaker choice is always a matter of compromises. In a hypothetical world where I had more money and roadies I would probably use Celestion Blues or Silvers for everything, in 2x12 or 4x12 cabs. But a single 15w Blue is not going to fly for an AC30 and I have never been happy with 2 x el84 circuits - not enough headroom and depth to the sound vs 4 x el84s. Back when I was not playing out I had a Goodsell 33 combo with 2x12s that had a stunning clean tone in my home studio. But after resuming gigging I realized it would never leave the house (too heavy - too pretty)and reluctantly sold it. So the 50W Weber Blue Dog is the best compromise I have found so far for a single 12" combo in the 30-50 watt range. It does not sound like a real Blue but it has many of the same qualities that I like about them.

I feel the same way about 2x el84 circuits. There always seems to be something missing in the depth of the sound and then when you go to 4 x el84 it sounds better and even at lower volumes it sounds better ( fuller and more depth) I notice this more with el84 than with other tubes.

Hi Colossal. Sounds like you found exactally what your looking for sound wise with the 20 watt greenbacks. I will have to give them a try one day.

Cheers!

Guy

[pompeiisneaks]

For me speaker choice is always a matter of compromises. In a hypothetical world where I had more money and roadies I would probably use Celestion Blues or Silvers for everything, in 2x12 or 4x12 cabs. But a single 15w Blue is not going to fly for an AC30 and I have never been happy with 2 x el84 circuits - not enough headroom and depth to the sound vs 4 x el84s. Back when I was not playing out I had a Goodsell 33 combo with 2x12s that had a stunning clean tone in my home studio. But after resuming gigging I realized it would never leave the house (too heavy - too pretty)and reluctantly sold it. So the 50W Weber Blue Dog is the best compromise I have found so far for a single 12" combo in the 30-50 watt range. It does not sound like a real Blue but it has many of the same qualities that I like about them.

I feel the same way about 2x el84 circuits. There always seems to be something missing in the depth of the sound and then when you go to 4 x el84 it sounds better and even at lower volumes it sounds better ( fuller and more depth) I notice this more with el84 than with other tubes.

Hi Colossal. Sounds like you found exactally what your looking for sound wise with the 20 watt greenbacks. I will have to give them a try one day.

Cheers!

Guy

I had a discussion one day with jelle and a few others on a FB group and it sorta makes sense. Having the two extra tubes in parallel adds some additional 'je ne sais quois' I've played with my ODS #124 with the 50/100 switch and the volume decrease is nominal at best but it definitely seems 'different' in a way I don't like at 2 tubes.

~Phil