Express done...need help calming the hisss

[amplifiednation]

The hiss is greatly reduced with the jack plugged in (even halfway). Tubes really did help with the levels. I think there is something shotty at the jack like a bad joint or something. The hiss is not bad with the guitar plugged in and volumes at zero

[M Fowler]

Just make sure you used a lock washer on the back side of the jack against the chassis to bite in and ground.

Mark

[ampdoc1]

You may have a few little problems, but your description of playing the amp leads me to believe you've built it correctly. I had the same "dropped jaw" moment as soon as I lit up my first one. Very sensitive to the pick, great harmonics.

Feels like it's playing itself.

a'doc1

[amplifiednation]

Thanks guys. Yeah, the amp's definitely built well, I just either think I've got a bad ground at that shorting jack or my grids are picking up AM radio.

The amp sounds awesome. I will be VVRing soon to try to tame this beast a little more. Running my attenuator has got to be draining the power tubes pretty fast.

[M Fowler]

Taylor did you use a 33k or 68k grid blocker resistor to V1?

[PCollen]

Thanks guys... I will try the 7025. I have a bugle boy in v1 now, its better, but still hissy. Put a "rogers" mullard, I think, in V2 and RCA 12ax7 in v3

I am getting more change with the presence control which is cool.

I put in a pair of Siemens el34s that I bought specificaily for the build and put that amp though the paces. Man is it loud! The controlled feedback is amazing. I cant wait to play with tubes more. Wife should be at work tomorrow...muhahahaha

Amp gets a little squeely at full volume when the presence or treble is cranked, that was a relief, I was getting nervous it was too stable. It is amazing you can tap the chassis and hear it through the speakers

I would shorten the plate wire to V1 , run it over the top of the socket. You can also go with a 1w plate resistor. A dale RN65 is 3/4w and very quiet, good mojo too.

If you really want low noise, Parallel the V1a/b, use 2 100k plates parallel for 50k, and use paralled 1.5k for 750 cathode resistors. move the second stage to the unused V2 1/2 . I guarantee it will be very quiet and sound even better. Might not be a true clone anymore.

Don't forget to adjust the V1 a/b cathode(s) bypass cap to accomodate that reduction in effective cathode resistance.

[PCollen]

I would shorten the plate wire to V1 , run it over the top of the socket. You can also go with a 1w plate resistor. A dale RN65 is 3/4w and very quiet, good mojo too.

If you really want low noise, Parallel the V1a/b, use 2 100k plates parallel for 50k, and use paralled 1.5k for 750 cathode resistors. move the second stage to the unused V2 1/2 . I guarantee it will be very quiet and sound even better. Might not be a true clone anymore.

I understand shortening the plate but how does paralled triodes cut down noise? Is it going to add gain? I don't think I need any more gain!

If you use a 50k plate load (2x100K) and 750 ( 820 is close enough)cathode resistor( I use 2x1.5k ), the gain is the same. The noise is 3db lower. Using 2 100k 1/2w resistors or 1 50k 1w resistor lowers the contact noise of the resistor too.
All I can say is try it, it is very easy to do and you lose nothing but noise. It does slightly fatten the tone due to the lower output impedance. Theoretically you should also raise the bypass cap value to double, but I don't hear any difference in the cap value so I leave it as is if it is 25uf.

The Dr. Z MAZ-18 uses a parallel V1 input, with 68K shared plate resistor, 1.2K shared cathode resistor, and (AIR) 22uF shared cathode bypass cap.

[billyz]

I can think of a few examples of the parallel triode . Mesa , Matchless, even a fender reverb driver. It is not new or original.

I just built two amps for a client. one had the parallel triode the other not. He just reported back to me that , At first he did not hear the difference but at stage volume it was apparent which had the parallel V1, and he much preferred it. He now wants to send me the other amp to convert to the paralled stage. He reported it did seem more articulate as well.

I doubt I would ever add a tube to do it, but if you are left with half a stage why not ?

[Roe]

reducing vol pot to 500k decreases hiss. also find some low-noise 100K resistors to use early in the circuit

[amplifiednation]

i liked the parallel triode but lost all tone controls.

would using a 500K pot increase the "touchiness" of the volume control?

right now the volume control is basically off and on, and then "on" with more saturation as the volume increases. not a problem with an attenuator but unbearably loud without.

I put some 6V6's in the express last night, sounded good!

[azatplayer]

Ive had some repeated issues with the switchcraft jacks contacts.
May be cos ive held them wrong while tightening perha[s, but have had enough problems to change out to using cliffs. Just a better switch.
Ive had that exact issue you are having with the jack, put a meter over it and see what you get.

[Roe]

...
would using a 500K pot increase the "touchiness" of the volume control?...

no, not as long as you use an audio taper. but it will decrease the gain slightly. also you need to double the capitance of the bright caps to 200pf and 1nf

[passfan]

Ive had some repeated issues with the switchcraft jacks contacts.
May be cos ive held them wrong while tightening perha[s, but have had enough problems to change out to using cliffs. Just a better switch.
Ive had that exact issue you are having with the jack, put a meter over it and see what you get.

+1 for me as well. I use cliffs now. Reach in there with your chopstick and close the shorting tang and see what happens to your hiss.

[Roe]

cliffs are way better, also they are better for you grounding scheme.

another trick that may reduce hiss is a 150pf snubber over the first anode 100k resistor