Diagram for 50/100 watt switch

novosibir · Post by **novosibir** » Fri Dec 09, 2005 7:46 am

And think about, that with only 2 tubes in use your B+ will rise up about 4-8 volts, because the load to your power supply is diminished! So better adjust the bias/plate dissipation only with 2 tubes in use.

Larry G

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 8:49 am

novosibir wrote:And think about, that with only 2 tubes in use your B+ will rise up about 4-8 volts, because the load to your power supply is diminished! So better adjust the bias/plate dissipation only with 2 tubes in use.

Larry G

Hmmm how off would the bias be? Theres lots of amp manufactures that have a half power switch and I don't think they have it wired to change the bias also.

novosibir · Post by **novosibir** » Fri Dec 09, 2005 8:55 am

Brentsp wrote:Hmmm how off would the bias be? Theres lots of amp manufactures that have a half power switch and I don't think they have it wired to change the bias also.

Most of the amp manufacturers are biasing their amps far too cold*, so switching 2 tubes off can't be a problem.

Larry G

(*) An exception has been the 1959HW. This amp was biased at nearly 100% plate dissipation (!)

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 9:04 am

I know Bogner has his amps biased correctly and his XTC has a half pwr switch but I don't know how its wired.

Billy Batz · Post by **Billy Batz** » Fri Dec 09, 2005 9:20 am

Just FYI Ive always pulled tubes form my amps without rebiasing or even without adjusting the impedance.

Bainzy · Post by **Bainzy** » Fri Dec 09, 2005 10:00 am

Yep the Jublilees had Pentode/Triode switches. I've tried both that switch and pulling the tubes, and the pent/tri switch is just so much more effective for curbing volume, not only does it make the amp a lot quieter on 10 it sounds better too in my opinion.

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 10:02 am

Bainzy wrote:Yep the Jublilees had Pentode/Triode switches. I've tried both that switch and pulling the tubes, and the pent/tri switch is just so much more effective for curbing volume, not only does it make the amp a lot quieter on 10 it sounds better too in my opinion.

I'm actually doing both with two seperate switches......... so it will lower it to around 30 watts.

Billy Batz · Post by **Billy Batz** » Fri Dec 09, 2005 10:09 am

If this is solely about cutting the volume lemme curb that myth right now. Brent take 2 tubes out and listen. The difference is not even a click ona hotplate. Its a hair. Its a little less balls mostly. Even a 50w isnt going to be much lower then a 100W. A click on the attenuator. I dotn know if combining it with a Pent/Tri and having them both on at the same time will help more with volume or just having a P/T is enough but just a 50/100 switch is a bit of a waste on its own IMO especially when you can just pull 2 tubes. Ive done it on all my amps. All my 100W amps anyway. Totally a marketing thing. People who know nothing about amps think its a great thing because they always think its half as loud. It doesnt work like taht. Power doesnt=dbs; dbs dont=percieved volume. Now if you were intending to sell your amps...

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 10:11 am

Billy Batz wrote:If this is solely about cutting the volume lemme curb that myth right now. Brent take 2 tubes out and listen. The difference is not even a click ona hotplate. Its a hair. Its a little less balls mostly. Even a 50w isnt going to be much lower then a 100W. A click on the attenuator. I dotn know if combining it with a Pent/Tri and having them both on at the same time will help more with volume or just having a P/T is enough but just a 50/100 switch is a bit of a waste IMO especially when you can just pull 2 tubes. Totally a marketing thing. People who know nothing about amps think its a great thing because they always think its half as loud. It doesnt work like taht. Power doesnt=dbs; dbs dont=percieved volume. Now if you were intending to sell your amps then its useful

I know what you saying but the face plates are already done and labled, no turning back now, I'm doing it.

Billy Batz · Post by **Billy Batz** » Fri Dec 09, 2005 10:16 am

I know. Its the prototype

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 10:24 am

Billy Batz wrote:I know. Its the prototype

The volume is only around 3dbs lower but the feel and head room changes quite a bit in 50 watt mode. Combine that with the tubes in triode mode and you have around 30 watts with a great soft feel, lowered headroom and volume. I did this with my XTC and Mark IV and it works great IMO. Unscrewing the back panel and pulling two tubes is fine but flicking a switch and halfing the impendence is lots easier.........at least I think so.

Billy Batz · Post by **Billy Batz** » Fri Dec 09, 2005 10:29 am

Different strokes. Its unusual for me to ahve the rear panels on my amps ever. I think its probably a little different for high gain amps that you dont crank all the way as well. Ive always cranked the channel switching amps I had too. There isnt an amp Ive owned that I couldnt get a good zeppelin live sound by diming the master and bringing thr gain up a bit.

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 10:33 am

Billy Batz wrote:Different strokes. Its unusual for me to ahve the rear panels on my amps ever. I think its probably a little different for high gain amps that you dont crank all the way as well. Ive always cranked the channel switching amps I had too.

With non master volume I would think the dual switches would be even more desired but maybe not. I always used the half pwr and tri/pen modes if the amp had them so I guess thats why I want it on my amp. Are you going to be around the PC or phone today. I may go home early and finish up my amp so I can have it for the OK Ampfest tomorrow.

Billy Batz · Post by **Billy Batz** » Fri Dec 09, 2005 10:35 am

Yeah. Im off today. Its a snow day. Actually I dont have snow days just days I dont feel like working which have been way too few and far between.

Brentsp · Post by **Brentsp** » Fri Dec 09, 2005 10:38 am

Billy Batz wrote:Yeah. Im off today. Its a snow day. Actually I dont have snow days just days I dont feel like working which have been way too few and far between.

ok super. I may call upon you if I run into a pinch because I have to have this done by tonight. The head cab supposed to come today to <crosses fingers>.