New trainwreck clone HOWLING

[audiosalvage]

I have a ceriatone express clone that sounds good and quiet but I currently have a 12au7 in the PI position. The minute I put in a 12ax7, it begins to produce low frequency oscillation no matter what the volume. I've tried different tubes with same result. SOS

[joeboo88]

Hi. Is this a new build? If so maybe think of swapping the the OT to power tube plate ( pin 3) connections, you might have positive feedback, going on.

If not maybe post some voltages and photos of the amp.
Good luck, Joe

[audiosalvage]

Hi I've posted before previously with issues with a bad pot to get says new-build noise issues. There are pics of this unit. I can try what you've suggested but why would this not be an issue with the 12au7?

[joeboo88]

Maybe because the 12au7 has hardly any gain compared to a 12ax7. if you give it more signal, the howling is amplified, I believe.
Alot of us have had this issue when building from scratch. and its a simple thing to do to eliminate the problem, and if it doesn't solve it you can swap the leads back, and go on from there.

[audiosalvage]

I'll give it a shot and report back. Thanks

[audiosalvage]

Looks like a quick test seems that worked. I will try it in a more real situation. Thank You

[joeboo88]

Hope it works out.....with your Express your gonna have sore ears...what a beast.

I actually have a 12au7 in the PI position and a 5751 in v1 and an attenuator so I can crank it a bit and it still is a beast

Good stuff....

[audiosalvage]

Yes, I've tried a 12au7 in v1 and PI and it sounds very plexy like. I think I'll ask santa for an attenuator.

[aceofbones]

I think I'll ask santa for an attenuator.

You should build one of these. It doesn't cost much in parts, and is easy to build. More importantly, it works really well. I'm using one with my Express, I just finished building, and it does a surprisingly good job.

The thread is super long (103 pages and counting), but the main updated info ion the build s always in the first couple posts. Check it out...

https://www.marshallforum.com/threads/s ... ing.98285/

[Colossal]

Hope it works out.....with your Express your gonna have sore ears...what a beast.

I actually have a 12au7 in the PI position and a 5751 in v1 and an attenuator so I can crank it a bit and it still is a beast

Good stuff....

Hey Joe,

Do you find a change in the range of your clean-to-mean after going to the 12AU7 and 5751? Did you adjust your PI values to compensate or just plug and play?

Thanks,
Dave

[joeboo88]

Hope it works out.....with your Express your gonna have sore ears...what a beast.

I actually have a 12au7 in the PI position and a 5751 in v1 and an attenuator so I can crank it a bit and it still is a beast

Good stuff....

Hey Joe,

Do you find a change in the range of your clean-to-mean after going to the 12AU7 and 5751? Did you adjust your PI values to compensate or just plug and play?

Thanks,
Dave

Hi Dave. I didn’t want to mess around with the components, I just plugged and played. Actually I erred. I should have said I had a 12au7 in V1 and. 5751 in V2. When I just want the Express tones I run it like I just stated and I can dial the amp up almost half way and it still gets mean, without the cops coming.
if the wife goes out I usually run the amp with all 12ax7s and use my attenuator...lol. These things are so loud so fast that with the stock layout I can only use 2 on the dial. Thus lower gain tubes and attenuators.
It’s too bad these amps sound glorious when cranked, but most of us can’t really do that, and my Express usually sits unused a lot of the time.

Oh well my kid will get it, he just bought a house.... let the cops come to his place.

[Colossal]

Hi Dave. I didn’t want to mess around with the components, I just plugged and played. Actually I erred. I should have said I had a 12au7 in V1 and. 5751 in V2. When I just want the Express tones I run it like I just stated and I can dial the amp up almost half way and it still gets mean, without the cops coming.
if the wife goes out I usually run the amp with all 12ax7s and use my attenuator...lol. These things are so loud so fast that with the stock layout I can only use 2 on the dial. Thus lower gain tubes and attenuators.
It’s too bad these amps sound glorious when cranked, but most of us can’t really do that, and my Express usually sits unused a lot of the time.

Oh well my kid will get it, he just bought a house.... let the cops come to his place.

Ah, ok. Interesting. Yeah, they are loud amps, for sure, and the only way they really sound and perform their best. I really love what they do, although I would lean a little more towards the Liverpool sound.

[joeboo88]

Actually I built a Liverpool a few months ago with a ppmiv master volume and it actually sound good with the MV.
I never posted that build but it was built on one of RJs reverse chassis, but it still looks good.
Peace...