Suggestions for a low watt (<=5w) PP project?

[lord preset]

I've got a PT/OT set from a Laney Cub 10 that I'd like to use for a low watt project for my brother. The Cub 10 is a 10watt fixed bias PP amp with 2-6V6 output tubes.

From what I've been able to glean, the PT is the same one used on the LC15, 225-0-225, with 6.3v heater and 20v bias taps. The OT is 8K primary and 8 ohms out.

I've been hunting about and most low watt designs are single ended, especially <5W. Ideally I'd like a <= 5-7 watt amp with good OD ala MiniWreck, MiniHRM. I'm a rank newbie so I would prefer to stick to existing as-built schematics vs mixing and matching designs if possible.

Any suggestions would be appreciated. Thx

[Firestorm]

You'd be hard-pressed to hear the difference between 7W and 10W. SEs are Class A, P-P can be A or AB. If you want to keep the output down, keep the B+ down.

Some guys here have played with small tubes in the output, so there's that.

Or, if the B+ is high, go cathode biased and you trim the effective plate voltage a little.

[lord preset]

You'd be hard-pressed to hear the difference between 7W and 10W. SEs are Class A, P-P can be A or AB. If you want to keep the output down, keep the B+ down.

Some guys here have played with small tubes in the output, so there's that.

Or, if the B+ is high, go cathode biased and you trim the effective plate voltage a little.

I agree re 7 vs 10 watts. I'd ideally like something around 2 watts. I was looking at the AX84 4-4-0 design but I'm not sure my OT would work as the 4-4-0 seems to be calling for a primary OT impedance of 22K vs 8K. Possibly if I used a 16ohm speaker it might be OK but I'm not sure.

[Phil_S]

The typical 1/2W to 2W is done with a dual triode PP self-split. Tubes to use include 12AU7, 6SN7, and ECC99. I think you'll get the most power and clean headroom from the ECC99. All should put out reasonable volume that you can still have a conversation with. If you drive a 4x12 with it, it can be quite loud, though. I think you are looking to run one of these tubes into a 22K primary. MPS makes one specifically for this sort of amp.

[lord preset]

The typical 1/2W to 2W is done with a dual triode PP self-split. Tubes to use include 12AU7, 6SN7, and ECC99. I think you'll get the most power and clean headroom from the ECC99. All should put out reasonable volume that you can still have a conversation with. If you drive a 4x12 with it, it can be quite loud, though. I think you are looking to run one of these tubes into a 22K primary. MPS makes one specifically for this sort of amp.

This is going to be built as a 1-10" combo. What I am hoping to do is use the OT that I have which is 8K primary/8 ohms out. I mentioned 22k because that was the spec for the AX84 4-4-0 OT. It calls for a Hammond 125c which can be set up for 22k. I am not looking for much clean headroom although some would be good. My brother is bedroom player who likes to wail, but he can't do that now without resorting to pedals or (gasp) modelers.

[Firestorm]

Not to start a feud, but I have always hated the idea of amps that can only do tiny watts. Build one that has a chance of being giggable and scale it. IMHO.

[lord preset]

Not to start a feud, but I have always hated the idea of amps that can only do tiny watts. Build one that has a chance of being giggable and scale it. IMHO.

If it was for me I would agree. I've concluded that I can't really get along with any amp under about 30 watts as I like lots of headroom at gig volumes and I don't have issues with volume at home.

My brother on the other hand is in a different situation. Can't play loud basically ever. In any case this will never be a gigging amp. I'm going to build in a cabinet that looks like a goofy robot with steel legs Not likely to leave the house.

[Milkmansound]

Mini class A tweed Princeton?

[IMG768]http://i896.photobucket.com/albums/ac16 ... b52b93.jpg[/img]

[Firestorm]

Not to start a feud, but I have always hated the idea of amps that can only do tiny watts. Build one that has a chance of being giggable and scale it. IMHO.

If it was for me I would agree. I've concluded that I can't really get along with any amp under about 30 watts as I like lots of headroom at gig volumes and I don't have issues with volume at home.

My brother on the other hand is in a different situation. Can't play loud basically ever. In any case this will never be a gigging amp. I'm going to build in a cabinet that looks like a goofy robot with steel legs Not likely to leave the house.

I hear you. But then get him an original VG-8 - OH! HERESY! DID HE JUST SAY THAT? - if you eq it right, it's surprisingly effective 90% of the time.

[sliberty]

Mini class A tweed Princeton?

[IMG768]http://i896.photobucket.com/albums/ac16 ... b52b93.jpg[/img]

That looks badass. Any info on it? Schem? BOM?

[lord preset]

Mini class A tweed Princeton?

[IMG768]http://i896.photobucket.com/albums/ac16 ... b52b93.jpg[/img]

That looks badass. Any info on it? Schem? BOM?

Indeed. I was going to say. Do tell..

[Milkmansound]

I just tossed it together point to point from spare parts.

I'll see if I can draw it up - about $200 cost of materials and it screams.

Perfect if you have one of those unleash thingies - and you can sub in 6SN7

Uses a reverb output tranny and a $17 25mA power tranny.

edit: here is a shot of the inside. I think a grid stop on the output tube would smooth out the distortion

[IMG768]http://i896.photobucket.com/albums/ac167/milkmansound/IMG_3085_zpsf53b1fa0.jpg[/img]

I used .05 coupling caps, 20uF power caps and 5k dropping resistors. Tubes are 12AU7 driver and a 12AY7 sounded best as the preamp tube. There's a tweed tone circuit 1MA and volume pot 1MA. Not much to it. Diodes used as a rectifier.

[Tone Lover]

Looks cool do draw it up if possible. I have a cousin who can only play at bedroom levels . Thought I would build him a firefly or what ever those small amps like this were called.
Im mainly curious about the PT you used.
I have enough parts laying around including reverb transformers which many are using for the OT at 22K to 8ohm .
But its cool if you don't have time.
I really liked the small package you put it in. What size was the chassis.

Thanks Bill

[Cantplay]

I have one of these. For the low cost it wasn't worth me building it.

http://www.ebay.com/itm/1-4-Watt-Boutiq ... 1301162925

John

[10thTx]

I use a PT that is 275-0-275 with 150ma.

Using a 5Y3GT , I use 6K6's for 7-8 watts cathode biased

Using a 5V4 or GZ34, I use 6V6's 14 watts or 5881's 23 watts.

With respect, 10thtx