Blues Jr Hiss

[brightblack]

Hello all- My set-up goes like this:

My custom "Strelecaster" (Strat body,Tele neck,Alnico II single coil at the neck Alnico II humbucker at the bridge)> Hardwire tuner> Keeley 4-knob Compressor>Crybaby Wah> Seymour Duncan Twin Tube OD>Electro-Harmonix Little Big Muff> Line 6 MM> Line 6 Echo Park Delay> Blus Jr.


I've developed a nasty hiss that seems to get louder itermittently...I usually have my amps gain down to 2 or 3 & set the master between 5 & 10.

Is this normal? It seems to be getting worse...I don't believe it's the tubes because I've swapped them out...& it happens with or without running through my effects chain...it increases with volume...I realize that the Blues Jr. is only a 15 watt amp, I'm not trying to emulate a rectifier but it should be able to handle some overdrive....

[SatelliteAmps]

Does it happen with a different guitar or guitar cord?

[brightblack]

Does it happen with a different guitar or guitar cord?
That's good question, I'll try that route tomorrow & get back to you....

[MstrBones]

>I've developed a nasty hiss that seems to get louder itermittently

There are some BJ's out there with some bad filter caps apparently. Yours might be one - fairly easy to check. See link below.

http://billmaudio.com/wp/?page_id=267

[phsyconoodler]

Most hiss sounds in Blues Jr's are from preamp tubes.They also have terrible tube sockets that need to be re-tentioned so the tubes make good contact.

[brightblack]

Just checked the caps- everything looks good, In fact the whole board looks clean as can be...It just likes to hiss when there is a lot of gain...even when the guitar is not plugged into the amp there is hiss when I turn up the gain on both pedals or the amps gain...although there is less without pedals....frustrating I've had the amp for well over a year & this has never been an issue....Do you think it could could be the plug in my house?

[phsyconoodler]

I guess you already tried new preamp tubes and retentioned the sockets?
Also,you don't check caps by looking at them.

[brightblack]

I guess you already tried new preamp tubes and retentioned the sockets?
Also,you don't check caps by looking at them.
Yes I checked all the tubes & tensioned the sockets...I also realize that there's more to checking caps than merely "looking at them".... I was referring to a leaky batch that apparently went out on a handful of Blues Jr.'s....I'm kinda stumped at the moment...I'm no tech by any means but I learn quickly...so what is the best method to checking caps?

[phsyconoodler]

The caps can be checked to see if any DC voltage leaks past to ground.They aren't likely to actually "leak" visibly.
Again you said you checked the preamp tubes.How exactly?
I'm just trying to help,but you are being vague in your descriptions.

[Tonic Amps]

Since the hiss tracks with volume, the source is most likely near the input. Noisy tube. Noisy plate resistor in V1a. Noisy 1M load resistor on the input. Or it could possibly be a noisy resistor in the power supply.

Simple test would be to try a known low noise tube in V1. More than likely it is the tube, but you never know.

[brightblack]

The caps can be checked to see if any DC voltage leaks past to ground.They aren't likely to actually "leak" visibly.
Again you said you checked the preamp tubes.How exactly?
I'm just trying to help,but you are being vague in your descriptions.
Sorry about my lack of details..I checked the tubes by swapping them out with some extra ones I had (stock fender groove tubes) & the hiss was actually slightly worse.... I currently have Tung-sols & JJ's in their now...the tube in V3 which was matched went microphonic so I replaced it with an extra JJ that is not matched....so the tubes are as follows:

V1:Tung-sol 12AX7
V2:JJ 12AX7
V3:JJ 12AX7(unbalanced)
Power tubes:JJ EL 84's (matched set)

[andrekp]

Test it w/o pedals. Use a short, known good cable and just run the guitar into the amp straight. Same thing? I'd suspect a preamp tube in the amp, but your pedals could certainly be the cause as well. Since they are easy to rule in or out, do so.

[brightblack]

Test it w/o pedals. Use a short, known good cable and just run the guitar into the amp straight. Same thing? I'd suspect a preamp tube in the amp, but your pedals could certainly be the cause as well. Since they are easy to rule in or out, do so.
It is considerably quieter without pedals (I also realize how much better the amp's natural OD is as well!) but the hiss is still there...I think I'll try a 12AY7 in V1 I'll see if the lower gain tube will quiet things down a bit...I'm still open for more suggestions though...

[WaltC]

as an experiment, if you have another JJ, swap it in for the Tung Sol in V1 (balanced or unbalenced really doesn't much matter). See what happens...

[brightblack]

Hello all- My set-up goes like this:

My custom "Strelecaster" (Strat body,Tele neck,Alnico II single coil at the neck Alnico II humbucker at the bridge)> Hardwire tuner> Keeley 4-knob Compressor>Crybaby Wah> Seymour Duncan Twin Tube OD>Electro-Harmonix Little Big Muff> Line 6 MM> Line 6 Echo Park Delay> Blus Jr.


I've developed a nasty hiss that seems to get louder itermittently...I usually have my amps gain down to 2 or 3 & set the master between 5 & 10.

Is this normal? It seems to be getting worse...I don't believe it's the tubes because I've swapped them out...& it happens with or without running through my effects chain...it increases with volume...I realize that the Blues Jr. is only a 15 watt amp, I'm not trying to emulate a rectifier but it should be able to handle some overdrive....
What's up everybody?!- I just replaced a 12AX7 in V1 with 12AY7 & what a difference!! The hiss is almost gone...with or without pedals!!

I don't know if it's because of the lower gain 12AY7 or the 12AX7 was simply bad, but who cares..!!

I actually really love the extra headroom the 12AY7 offers!!

I'm still tryin' to get aquainted with this Blues Jr.!!

Thanks everyone for the feedback!!!

[MstrBones]

I guess you already tried new preamp tubes and retentioned the sockets?
Also,you don't check caps by looking at them.

True enough, though the Billm link is related to a possible bad batch of leaky BJ caps that got into cream board BJ's.