K-502... upgrading the OPT's with Hammonds

[jmillerdoc]

Hello,
I have seen quite a few mods of the S5 electronics K-502 tube amp kit and recently built one myself with some of the Voltsecond mods done. It has turned out quite terrific but I was thinking of upgrading the OPT's to Hammond iron. I am not sure of the impedance values of the stock OPTs on this kit and was wondering if anybody had some suggestions on which of the Hammond PP OPTs could be used in this little amp.
Thanks alot!
Jeff

 

[HollowState]

I'm not real familiar with this little amp, so I searched around to see what tubes it uses. Assuming yours has the 11MS8s in push-pull, you will want a fairly high plate to plate load impedance. I'd put that around 10K ohms or more. Hammond may not be the only or best choice. They do make a 10K/4-8-16 ohm (P-T 1609) that would serve. You don't have to use the screen taps if the K-502 doesn't use them.

Edcor makes a 25 watt unit that's 12K/6 ohm. The extra wattage won't hurt, but you will need to check the physical size to make certain it will fit the chassis. I tend to think Edcor makes a nicer transformer. They also have some smaller models on the second link.

http://www.edcorusa.com/Products/ShowProduct.aspx?ID=478

http://www.edcorusa.com/Products/BrowseSeries.aspx?SeriesID=33

You might also check out Trancendar and Electra-Print transformers to see what they offer.

BTW, if your amp used global negative feedback, you may have to tinker with that.

Victor

 

[Poindexter]

I shall be blunt.  Hammond output transformers are not 'upgrades' for anything.  I have tried several.  Creamy, bland, lo-rez.  You want an upgrade, get a good transformer; O-netics from Bud Purvine, MagneQuest from Mikey LaFevre, Silk from SACThailand, ElectraPrint, there are others I have neglected.  Good sound comes from good iron.  You don't want to spend the dosh right now, stand pat.  There's no gain from lateral movement.

Best Aloha,

Poinz
AudioTropic

 

[Soonerorlater]

Hi Poinz,

I replaced my stock output transformers in my K502 with Hammond 1609's and it was certainly IMHO not a lateral step. I'd love to hear how my K502 would sound with any one of the transformers you have suggested, I just think there is a limit to how much I should spend on this amp. My 1609's are now coming out along with the Auricap signal caps and are going towards Gingertubes Babey Huey. The K502 has served it's purpose as a first tube kit.

Keep it Country

Bill

 

[Jeb-D.]

Hi Poinz,

I replaced my stock output transformers in my K502 with Hammond 1609's and it was certainly IMHO not a lateral step. I'd love to hear how my K502 would sound with any one of the transformers you have suggested, I just think there is a limit to how much I should spend on this amp. My 1609's are now coming out along with the Auricap signal caps and are going towards Gingertubes Babey Huey. The K502 has served it's purpose as a first tube kit.

Keep it Country

Bill

I agree. It doesn't make a lot of sense to buy a budget kit amp and dump a bunch of money into it and replace everything.

Use the Auricaps in the Baby Huey.

For the K502, I'd recommend Wima MKP4 .22uF 400V coupling caps. I believe they are only like $1-$2 each and are available in a spacing that matches that of the PCB. They seem to be a decent upgrade over stock, though the sound with the stock caps wasn't bad either.