Lower hiss V1's for Express

[Richie]

sorry i had a typo.. should have been 12BZ7 not 12BA7

[geetarpicker]

I've done country gigs with my Express using a 12AY7 in V1 & V2 and even a pedalboard setup and wireless. The AY7s drastically reduce the gain and noise and can make the amp MUCH tamer.

That said IF you compare the Express with 12AX7s to an amp with similar gain the noise is actually not that bad IMHO. Heck in the studio when I would set my Express to similar gains levels of say a '68 plexi Marshall 100 the TW was actually quieter signal to noise wise. The Express has alot of gain, so noise is just the nature of the beast when you really crank it. Still, you shouldn't have any hum issues just white noise.

[Tubetwang]

I've done country gigs with my Express using a 12AY7 in V1 & V2 and even a pedalboard setup and wireless. The AY7s drastically reduce the gain and noise and can make the amp MUCH tamer.

That said IF you compare the Express with 12AX7s to an amp with similar gain the noise is actually not that bad IMHO. Heck in the studio when I would set my Express to similar gains levels of say a '68 plexi Marshall 100 the TW was actually quieter signal to noise wise. The Express has alot of gain, so noise is just the nature of the beast when you really crank it. Still, you shouldn't have any hum issues just white noise.

That is a good piece of advise right there!

Thanks for sharing!!

[Andy Le Blanc]

tube noise is a bugger
theres "shot effect"...... thats the sound of electrons being emitted from the cathode
"partition noise"...... the sound of electrons being divided around and between control grids
"flicker effect"..... uneven field distribution around a cathode due to it surface structure and temperature variations
"collision ionization" ..... free gas ions generated by collision with the electron stream
get collected by the plate and show up as noise

you got these and the ordinary hum, leakage, charges that build up on insulators
poor contacts, seconary emission, and microphonics

[jjman]

So a week or so after all the recording to find the lowest noise tubes in my arsenal, I went to plug a chord into the input for some testing while on my bench. I heard the ping thru the speaker and realized that the lowest noise tube is also microphonic. The Ruby that I tossed during the testing was faintly squealing. The “winner” for v1 had also been a Ruby and I should have done the tap test. So I moved it to v2 where it does not ping and put an RCA in v1. Just a hair more hiss according to the recording results and no ping when tapped. Now I'm looking into NOS and man have they become expensive.

BTW, Andy I just changed the trem back to injecting onto the outputs. This is the amp where you helped me find some schematics and I had moved it to the grid of stage 3. (The PPIMV was dropping the trem down when dialed down and I wanted to avoid that.) It sounded “weird” on stage 3 and still wasn’t strong enough when cranked. A friend said “it sounds like you have two trems running.” So I just went to the 6g3 Deluxe trem, grounding the bias-voltage side of the intensity pot since I’m using cathode bias on the output. I used a 100u cap on the cathode of the oscillator and a .022 filter on it’s trem-signal output to maximize it’s output. It sounds nice and strong and stays intact from 50%-100% on the MV. No problem. Not sure if EL34’s would be adequately modulated since I’m using 6v6s. Changing the pot to 500k and eliminating the 220k resistor would probably make it’s range more than adequate for el34s based on the plate’s waves I saw on my scope.

Sorry for hijacking my own thread but it is the same amp.

[Andy Le Blanc]

post a schematic of the changes to the trem. circuit if you can... love to see it

...... just because one is too noisey in one application deosnt
mean that it wont work in another...... ive been at it long enough to have a pile of bench spares....
so tubes that wont work here are found to work there...... a healthy pile of spares is a good thing

[Roe]

I put the RTFs in my 6g6b - I don't need more distortion in my express. I've had best results with old german tubes and tungrams in my express when it comes to ecc83s.

[Lonely Raven]

tube noise is a bugger
theres "shot effect"...... thats the sound of electrons being emitted from the cathode
"partition noise"...... the sound of electrons being divided around and between control grids
"flicker effect"..... uneven field distribution around a cathode due to it surface structure and temperature variations
"collision ionization" ..... free gas ions generated by collision with the electron stream
get collected by the plate and show up as noise

you got these and the ordinary hum, leakage, charges that build up on insulators
poor contacts, seconary emission, and microphonics

It's scary how much you pull out off the top of your head...you Rock Andy!

[jckid649]

So a week or so after all the recording to find the lowest noise tubes in my arsenal, I went to plug a chord into the input for some testing while on my bench. I heard the ping thru the speaker and realized that the lowest noise tube is also microphonic. The Ruby that I tossed during the testing was faintly squealing. The “winner” for v1 had also been a Ruby and I should have done the tap test. So I moved it to v2 where it does not ping and put an RCA in v1. Just a hair more hiss according to the recording results and no ping when tapped. Now I'm looking into NOS and man have they become expensive.

I have just noticed the same thing in mine. I have some Preferred Series 7025 12AX7's that are meant to be reproductions closely resembling the vintage Mullard's that I got from The Tube Store and those things ping so loud it sounds like somebody is playing the tambourine inside the amp!

[jckid649]

Does anyone have an answer for lower ping tubes that is consistent? I called the Tubestore and they have the RFT's but they said they aren't gonna be any lower noise than the Preferred series 7025's that I already have and they ping like a tambourine!

[jckid649]

Here's an audio clip of the noise I'm getting