Tubelab Simple P-P

[Ian444]

The power transformer wiring looks correct too. The quickest way to find the problem is first check there is 6.3Vac from pin 9 to pin 4 and from pin 9 to pin 5 on the 12AT7's. If those voltages are good, somewhere between 6V and 6.6Vac, then measure the voltages on pins 1, 2, 3, 6, 7 and 8 on each 12AT7, these will be DC voltages and some will be very high so take care. Best if you can measure all these voltages with the tubes in place. If you can't, then we'll have to think of Plan B.

What I meant with have you tried a different source is, do you have another CD player or tuner you can use to feed some sound to the amp?

[nutto]

I had used my Ipod mod and my htpc with grub dac they gave same result.just one quick question to measure those voltages I have to connect black probe to ground and red to the tube socket pin and stand as far away as i could right?

[rknize]

Read this:

Meter Use

[nutto]

Originally Posted by rknize

Read this:

Meter Use

thank you

[nutto]

I got the measurement now
Pin9-4 both tubes 6.6-7
Pin 9-5both 6.6-7
Left tube
1=216
2=103.8
3=106.5
6=103.7
7=0
8=0.90
Right tube
1=217
2=102.8
3=105.6
6=102.7
7=0
8=0.91
There must be somthing wrong on pin 7??

[Ian444]

All those voltages look fine. Its likely there is nothing wrong with your amp, assuming the output tubes are new or known good, and your speakers are good.

A few people have had problems driving this amp with an ipod or a DAC. The reason is that ipods and DACS often don't put out enough voltage or current to drive the amp properly. It is not a fault of the amp design, it works fine with a standard line level input such as that from a tuner or CD player. I also run music from my PC through a DAC into a SPP amp, but use a line level preamp before the amp, no matter what amp I am running at that time. And from my wife's PC, the output of the soundcard is boosted before being fed to any amplifier. My guess is this is your problem. Do you have a DVD player or CD player to play some audio into the SPP to test this?

[nutto]

I'll try use my ps3 to run it now

[nutto]

My ps3 only have digital out so i use line ouy from my pc still the samev maybe alittle louder but distort like hell and no bass

[Ian444]

If you want to check the output section of the amp, you could measure pins 2 and 3 of each EL84 output tube, with all the tubes in place. You would expect to get 0V at pin 2, and around 11V DC at pin3.

Then, with the output tubes still in place, measure the voltages at L-PRI_1-2, L-PRI_1-3, L-PRI_2-2, L-PRI_2-1 and same for the right-hand channel, expect around 310 to 330V DC. You should be able to put the red probe on top of the screw of each terminal block to measure these voltages. Be careful.

[nutto]

I think i found the problem there are 3 bad resistors r2,r4 and r104 but i'll check those output section voltages anyway just to be sure