It is currently Tue Mar 17, 2020 3:31 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 84 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6
Go to page Previous  1, 2, 3, 4, 5, 6
Author Message
Post subject:
Posted: Mon Jul 12, 2010 11:56 pm
Offline
Rock Star
Rock Star

Joined: Tue May 18, 2010 7:34 pm
Posts: 6911
grbullets wrote:
Thats a good thing, then you don't need a speaker upgrade. I have a 96 tweed with a 1956 Jensen P12R Professional series speaker, a 60'th anniversary tweed with the C12N, and a relic tweed with a current production Jensen P12R.



wow i take it you dont like these amps. :lol:

_________________
63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."


Top
Profile
Fender Play Winter Sale 2020
Post subject:
Posted: Mon Jul 12, 2010 11:57 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Mon Apr 21, 2008 1:37 am
Posts: 597
Location: Australia
grbullets wrote:
Personally, I wouldn't buy a kit from anyone. I have my own stash of hand picked US made NOS tubes for my preamp sections. However, I do use the JJ EL84's, average matched pairs. (I have 3 Blues Jr's, so I need a good stash of tubes) If I had to choose for an unmodded bias amp, I'd go for a set of the cooler running power tubes. For a modded amp, I would likely go for a standard matched set of power tubes. Preamp tubes are another subject. They all will act differently, even tubes of the same type, brand and production run. The best thing to do is experiment with different types and brands. If you're looking for a nice bluesy tone with good crunch with a guitar, look at the high quality 12AX7 types that have good balance for V1 and V2, but more importantly, you'll want a tube in V1 thats dead quiet. These amp's are very touchy when it comes to microphonic preamp tubes. I use only US made preamp tubes and always have. I never used JJ preamp tubes so I can't elaborate on those. Even slightly noisy tubes in V1 will cause excessive noise in the amp, therefore it's very important that the first preamp tube be dead quiet. Ultimately you'd want quiet tubes in both V1 and V2, but you can get away with a slightly noisy tube in V2 as long as it's only slightly noisy. If you want very clean tone, try a 12AT7 in V2 or even V3. If you want a crunchy tone, a 5751 in V2 or V3 will help. Best thing to do is experiment if possible to find out what types work best for you. I'm not a fan of kit's as far as tubes go. My biggest personal beef with the BJ's is the speaker. I do not like the stock Fender (Eminence) speaker. Something like the Jensen C12N or Celestion Vintage 30 is a far better choice. I think the speaker is the first mod to be done in a stock BJ amp. Then choose your tubes......................Dave


Thanks grbullets, I have JJ's allround in my tolex BJ... I am awaiting the arrival of my Jensen C12N speaker.

I can't wait.

The JJ's allround are a big improvement in tone over the GT's...


Top
Profile
Post subject:
Posted: Mon Jul 12, 2010 11:58 pm
Offline
Rock Star
Rock Star

Joined: Tue May 18, 2010 7:34 pm
Posts: 6911
i take it you dont like these amps. :wink:

_________________
63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."


Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 12:11 am
Offline
Hobbyist
Hobbyist
User avatar

Joined: Fri Aug 22, 2008 3:54 pm
Posts: 11
Location: upstate New York
I'm sure the JJ's are an upgrade from the stock Sov Tek's. If I didn't have so many US made preamp tubes, I'm sure I would have some JJ's. I've heard very good things about the 12AT7 and the 12AU7 tubes made by JJ. Yeah, you could say I'm a little "biased" toward the Blues Jr's :!:


Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 5:04 am
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
Retroverbial wrote:
grbullets wrote:
The blues jr's are biased high from the factory, all of them. It's a very good idea to have a trim pot installed for the bias, or at the very least, have the 22K bias resistor replaced with a 27K to 33K resistor to knock the bias down a bit. Ever notice how hot those EL84's get?? There's a reason for that. They're biased too high. Knocking the bias down with the above mentioned resistors will put it closer to the normal recommended bias range for EL84's and will not hurt the tone of the amp at all.


Adding a trim pot or upping the value of the bias resistor may provide some sonically-pleasing effect(s) but the fact of the matter is, EL84s are hot-running bottles and no mods are likely to significantly alter that fact. However, chilling the bias a skosh might extend the life of the glass.

HTH

Arjay


Arjay, you took the words right out of my mouth. EL84's DO run hot anyway.
They run hot in my Egnater. The difference is my tubes aren't mounted upside down and the amp is well ventilated. Even with all four power tubes running, the amp barely gets warm. I'm amazed the Blues Jr doesn't have a lot more heat related problems just due to it's less than robust board and components.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 2:48 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sat Mar 20, 2010 2:30 pm
Posts: 792
Location: A Land Downunder
I think the point to understand is that yes, EL84's run hot and always will, but in many BJ's they can also run 100 degrees cooler (still hot, but just not as hot) and in a blind test you won't notice, but long term, as pointed out by Supro, an amp constructed like the BJ is, will probably be better off without that extra 100 degrees.

The smart thing to do is get the bias checked so you know where you stand, if the bias gets cooled with a resister swap by a Fender approved tech, and you don't notice a negative effect on tone, then that's a good thing. You just need to be a bit smart about it, but like most things it can be taken to extremes.


Cheers,

Snowy


Last edited by No457 Snowy on Tue Jul 13, 2010 3:07 pm, edited 1 time in total.

Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 2:58 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
I'm not sure if it's 100 degrees hotter. I've never heard of anyone burning tubes up every couple of months. A fried of mine has been running his stock for over two years with no tube or heat related problems. But that amp has too many construction flaws to even be running EL 84's. It's not even a real Fender tone. The El84's are pretty aggressive sounding IMO. I won't run them full on the EL84 side with my Egnater. I'm usually 50% or less leaning more on the 6V6 side where it's a little smoother and rounder sounding to me.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 3:02 pm
Offline
Rock Star
Rock Star

Joined: Tue May 18, 2010 7:34 pm
Posts: 6911
man this stuff is hard to follow.
theres a few different posts about the BJ and its tubes.
so im gonna ask this one last time and write it down even lol.
for a blues tone on the NOS, w/o rebiasing the amp,
which tubes are a SAFE bet for the jr?
ok after biasing, again with for a blueey tone, which tubes are the better choice?

_________________
63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."


Top
Profile
Post subject:
Posted: Tue Jul 13, 2010 3:10 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sat Mar 20, 2010 2:30 pm
Posts: 792
Location: A Land Downunder
Supro, I'm just being Devil's advocate, as I can appreciate cooler is better if tone isn't detectably affected. I have a 10 year old BJ thats never had a bias change, checked yes, but not changed, so I understand that it's not something that needs to be done, although it might help with an already poor design.


Cheers,

Snowy


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 84 posts ]  Go to page Previous  1, 2, 3, 4, 5, 6
Go to page Previous  1, 2, 3, 4, 5, 6

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: