Hi everyone.
I joined this community some time ago, but as far as I can recall I haven't posted anything till today.
Here is my problem:
I started to play the guitar a few months ago and got a second hand HT-5R MkII at a good price, but it has a significantly loud hissing problem, especially on the dirty channel when cranking the gain up.
The noise on the clean channel is really low, so I am not worried about that one, but I am wondering if the "hissy" overdrive is something that could be considered as normal or not as my experience with tube amps and guitar gear is limited.
As far as I can tell, the hiss comes from the preamp section.
I replaced the stock preamp valve (Ruby 12AX7) with a Tung-Sol 12AX7...no changes.
Touching up the overdrive EQ changes de colour of the noise slightly.
If I bypass the preamp by connecting my guitar multieffects (Boss GT-1) output to the effects return of the amp, I can play and there is no hiss I can hear.
If nothing is plugged to the amp's guitar input, there is no hiss at all (this is what makes me wonder if there is an actual problem).
I opened the thing to take a look and there isn't any obvious sign of damage or component degradation, at least on the top side of the PCB. I did not look underneath as this requires some additional effort, so I decided not to do it for now.
Any comments would be appreciated.
Thanks!
I joined this community some time ago, but as far as I can recall I haven't posted anything till today.
Here is my problem:
I started to play the guitar a few months ago and got a second hand HT-5R MkII at a good price, but it has a significantly loud hissing problem, especially on the dirty channel when cranking the gain up.
The noise on the clean channel is really low, so I am not worried about that one, but I am wondering if the "hissy" overdrive is something that could be considered as normal or not as my experience with tube amps and guitar gear is limited.
As far as I can tell, the hiss comes from the preamp section.
I replaced the stock preamp valve (Ruby 12AX7) with a Tung-Sol 12AX7...no changes.
Touching up the overdrive EQ changes de colour of the noise slightly.
If I bypass the preamp by connecting my guitar multieffects (Boss GT-1) output to the effects return of the amp, I can play and there is no hiss I can hear.
If nothing is plugged to the amp's guitar input, there is no hiss at all (this is what makes me wonder if there is an actual problem).
I opened the thing to take a look and there isn't any obvious sign of damage or component degradation, at least on the top side of the PCB. I did not look underneath as this requires some additional effort, so I decided not to do it for now.
Any comments would be appreciated.
Thanks!
Attachments
1) basically normal; all active devices hiss, it´s a Law of Nature.
usually very low level but very high gain Guitar preamps increase that noise a lot, by their own gain.
2) real own hiss/noise is what you get with the guitar plugged in and all Guitar pots set to 0 , you would get the same by plugging a shorted plug there.
3) you hear no noise (or very little) with nothing plugged because most modern Guitar amps include an extra Mute circuit connected to one leg of the input jack, typically with nothing plugged a leaf contact shorts preamp out , go figure.
4) then how can people use such noisy amps at all?
Well, there is a reason you can switch between channels or switch gain/boost OFF with a footswitch: wile playing a tasty solo nobody will notice hiss buried under distorted guitar sound, once you stop you turn it OFF
Same happens with the distortion pedal own switch.
FWIW when you listen to live recordings from such Guitar Gods as Jimi Hendrix or Gary Moore you will often hear hiss/hum/buzz and even FM radio during short pauses.
If THEY learnt to live with it ...... 😱
By the way, tube rolling does not affect hiss, there´s at least 2 Op Amp gain stages before it.
usually very low level but very high gain Guitar preamps increase that noise a lot, by their own gain.
2) real own hiss/noise is what you get with the guitar plugged in and all Guitar pots set to 0 , you would get the same by plugging a shorted plug there.
3) you hear no noise (or very little) with nothing plugged because most modern Guitar amps include an extra Mute circuit connected to one leg of the input jack, typically with nothing plugged a leaf contact shorts preamp out , go figure.
4) then how can people use such noisy amps at all?
Well, there is a reason you can switch between channels or switch gain/boost OFF with a footswitch: wile playing a tasty solo nobody will notice hiss buried under distorted guitar sound, once you stop you turn it OFF
Same happens with the distortion pedal own switch.
FWIW when you listen to live recordings from such Guitar Gods as Jimi Hendrix or Gary Moore you will often hear hiss/hum/buzz and even FM radio during short pauses.
If THEY learnt to live with it ...... 😱
By the way, tube rolling does not affect hiss, there´s at least 2 Op Amp gain stages before it.
Hi.
Thanks for the input.
Then I assume that it is what it is, a high gain amplifier with a certain noise floor.
So, in this case, mi conclusion about why the noise disappears so drastically when not plugged in is based on what I see in the Mk1 version schematic, attached for reference (As one can expect, the Mk2 version is not available or I couldn't find it):
The input jack keeps the first opamp (IC1-A) input tied to ground when unplugged, so there is zero signal to amplify, having a quiet output as a result.
If plugged, any EMI reaching the input will translate into significant noise voltages due to the high input impedance determined by R46. That's probably a key factor, more than having a high gain preamp.
However, I still wonder if getting some good quality coupling caps would make a difference...
If it is not appropiate to share the schematic as I did, please let me know.
Regards
Thanks for the input.
Then I assume that it is what it is, a high gain amplifier with a certain noise floor.
So, in this case, mi conclusion about why the noise disappears so drastically when not plugged in is based on what I see in the Mk1 version schematic, attached for reference (As one can expect, the Mk2 version is not available or I couldn't find it):
The input jack keeps the first opamp (IC1-A) input tied to ground when unplugged, so there is zero signal to amplify, having a quiet output as a result.
If plugged, any EMI reaching the input will translate into significant noise voltages due to the high input impedance determined by R46. That's probably a key factor, more than having a high gain preamp.
However, I still wonder if getting some good quality coupling caps would make a difference...
If it is not appropiate to share the schematic as I did, please let me know.
Regards
Your are right. In the schematic you can notice the first triode's input is tied to ground (as the input section's input) when not plugged in
Looking at the schematic provided if the jack is not plugged in then the triode grid after the overdrive section is shorted to ground removing the noise. You do have quite a lot of overdrive gain. I suspect this is normal for the BlackStar but check. If you want less noise I suspect you will need a lower noise op-amp for the first stage or a noise gate. Alternatively use separate overdrive box and just use the clean input.