HT-20: More Background Noise in Clean than Overdrive?

[fjonasch]

Hey folks!

It's Sunday, my girlfriend is not around and I was bored... So here is how the signal flows throug the amp

Input > EQ and Channel Vol. > Send > Return > Reverb > Emulated Out > Master Vol. > EL34 > Output Transformer > Speaker

I have checked the effects loop and the emulated output, both are completely quiet in the clean channel with no input. Which means the noise is generated somewhere in the power amp section of the amp. I've opened my brand new amp to see what there is to do. I disconnected and twisted a few of the cables that you can access and could have an influence (wiring to the speakers, power lines), but this had no effect. What I noticed, would be nice if someone else could confirm this, is that the power transformer (the bigger one of the two) creates quite a bit of noise by itself. I guess that's where the noise is coming from and somehow reaches the speakers... Yet no idea how to solve this...
Two other things. I noticed that Blackstar are using Tube Amp Doctor tubes, which are among the finest tubes you can get in Europe. So bad tubes should not be a problem unless you threw the amp around... And if anyone needs the info, the PCB print says that the preamp tube V1 is the one closer to you when you open the back of a HT Studio 20 head, V2 is the one further away...

Have a nice evening!
Felix

PS: One thing at least I need to mention if anyone reads this thinking of buying a HT Studio 20. The clean sound is beautiful, and the noise is something you'll probably only notice in your bedroom, not in rehearsal, not on stage. It's not that loud and does not increase with the master volume...

[chrisp2]

What I noticed, would be nice if someone else could confirm this, is that the power transformer (the bigger one of the two) creates quite a bit of noise by itself. I guess that's where the noise is coming from and somehow reaches the speakers... Yet no idea how to solve this...

I just checked it and I can hear what you mean, a little hum. But it's not so loud. I almost can't hear it in 20cm distance.

BTW, does anybody know if guys from Blackstar are reading this threads here?

[fjonasch]

Hey guys!

I just emailed Blackstar support, with a short summary of what we found so far. Let's see how good their service is...

Cheers, Felix

[Beejer]

Hey guys!

I just emailed Blackstar support, with a short summary of what we found so far. Let's see how good their service is...

Cheers, Felix

Good luck. Keep us posted....

[chrisp2]

Hey guys!

I just emailed Blackstar support, with a short summary of what we found so far. Let's see how good their service is...

Cheers, Felix

great, I'm excited

Today I tried a power socket with mains filter (Type Knürr 3.318.005.1) but the noise is still there.
The new preamp tubes haven't been delivered yet.

cu
Chris

[MG]

[quote="chrisp2"]Hello,

I got me a new Blackstar HT-20 Combo. I'm quite happy with sound and quality but there's one thing that bothers me:
There's a remarkable background noise hearable in the clean channel. The guitar is plugged in and it doesn't matter if the volume on it is turned on or off, the noise is the same.
I already got me a replacement amp and the background noise on the second amp is the same as on the first one.
I have to say that the HT-20 is my first tube amp and I don't know what level of noise is normal for such an amp.
But what's really strange, at least for my understanding, is that the background noise in the overdrive channel is much lower. Normally I would say it should be the opposite way.

What are your experiences concerning this matter? Did you also notice a louder noise in clean than in overdrive?
I just can't believe that I received two amps with the same manufacturing error from two different dealers.
What can I do?

Thanks for your answers.

cu
Chris

Hey I have similiar problem. New HT 40... my first tube amp.
Crackling and popping with a bit of a wirring windy type sound in background .
Clean channel only.
Tried changing leads, guitars. Went from the shed to the House.
Have had bit of an issue where sound drops in and out intermittent when playing.
I don't know enough about them as yet to go pulling tubes out , should not have to with new amp !!

[fjonasch]

Hi fellas!

I received a reply from Blackstar support:

"have spoken with out technical department and With the symptoms you are describing it sounds like its a problem with the output valves.
This will have to be confirmed by a quick check over by a qualified technician and they will be able to replace the valves in the amp and also re-bias the amp."

I ordered a new set of EL34 and will try that...

- Felix

[chrisp2]

Today I tried my new Tube-Town TT12AX7/ECC83 Classic V1 preamp tubes. Didn't change anything with the noise.
Now I'm looking foward to Felix's test with the power tubes. I'll will keep crossing my fingers for that...

[fjonasch]

Hi all,

I had the power tubes replaced with the same type and the amp rebiased, this did not change the behavior with more noise in the clean channel. Reported this to customer support, let's see what we get. By the way, with the amp opened, I realized that the noise I described coming from the power transformer is just one of the caps vibrating, so should not be our noise source...

- Felix

[fjonasch]

Hi there!

I'm still in touch with Blackstar support, who told me to check V1 of the preamp tubes. As expected, no change. To show Blackstar support what we are experiencing, I took a short recording of my amp

https://www.dropbox.com/sh/o67sxn293wrs ... 0Noise.m4a

Have a nice evening!
Felix