Bluzdude46
26 posts
Feb 24, 2009
5:55 AM
|
Ok guys I decided to sell my 5w modded amps, keep the Bogens for Practice Amps and get a Fender '59 Bassman instead of Harpgear HG50 or SonnyJr 4x10. I was at my Harp Club meeting and let the guys try out the 5watters to much acclaim for small low cost amps, and was told that the optimum preamp setup for Bassman was 12ax7, 12at7, 12au7.
What I didn't ask was which direction do you start? facing the back of the amp going left to right or from the right side in? Anyone know?
Also if anyone has one of the 59 Bassman LTD reissue and has played with the bias pot let me know. I remember reading an article by Gerald Weber concerning changing the bias to a different wave design on the meter being better for Harp.
|
jbone
25 posts
Feb 24, 2009
5:18 PM
|
i have a replica '59 built by steve clark at sligo amps dot com. it has a good combination of speakers for both low and high breakup, which he did for no extra cost.
it came with all 12ax7's, which i replaced #1 and #3 with 12au7 to cut gain and still have headroom. this is working for me so far. i have not tried any other combos of pre amp tubes except this setup, but i figure why mess with it if it works?
i have not had it biased but this is likely the next step.
steve built this amp as close to original '59 specs as possible and it was very reasonably priced to boot. check him out!
|
Oxharp
70 posts
Feb 25, 2009
10:34 AM
|
Hi Bluzdude46,
I also have a Fender bassman 59 RI but mine is not the Ltd RI. As far as I can tell the Ltd has a Pine Cab and the other has a Ply Cab. The Ply cab is supposed to sound brighter and the pine is supposed to be a warmer sound the curcuits are the same.
Thats for a guitar so I suppose if it were for a harp it will be a small difference in sound.
As for the pre amp valves. I have had my amp modified for Harp and a Bios pot fitted but have not had it long enough to know what to do with it properly as It sounds great to me at the mo.I have also had a lot of other things done as part of this MOD. Its called the Rod Piazza Mod but I am still working on getting a better sound from it. It may just be my Mic or the speakers for me.
The valves are as follows.
Turn the amp around so you are facing the back of the speakers etc. The valves go from your left in this order Rectifier - Power tubes x2 - pre amp tubes V3 - V2 - and V1. V1 being the one near the outer side of the cab. Solid state rectifiers give a brigher sound a GZ34 Rectifer gives better sag and a 5u4G gives the most amount of Compression/sag. Your optimum pre amp setup sound good but I have been told from the amp tech (DO NOT change the 12AX7 in V3 - Phase splitter).
Let me know how it sounds. The acid test is to change the valves and set your volumes at 3 and play. If it drives the amp into disstortion at THAT volume then you have found the sweet spot. If it does not then its either the wrong pre amp valve set up your mic not giving out a hot enough signal or your technique and playing.
BTW what speakers do you have in your amp. The light Blues jensons p10r from Italy are not that Harp freindly but the eminence or webbers are supposed to be better at THAT sound every one is after.
Have a look at my web site on you tube OXHARP and look at West Westons vids. He is playing through a 59 RI Ply cab with a 5u4g GT powers tubes 2 x 12 ax7 and a 12 ay7 in V1.
He also has the eminence speakers in. His mics are very very hot and his technique is excellent so he has the whole package and its good to know IMHO what its supposed to sound like.
Hope this helps
Give me an email if you want any more info
russ.turner@ntlworld.com
Cheers
Russ
Last Edited by on Feb 25, 2009 11:32 AM
|
bluzlvr
126 posts
Feb 25, 2009
1:16 PM
|
I've got an amp mod question to put out there. I used to own a 1961 Fender Concert 4x10 that sounded awesome for harp. One day I tried removing one of the preamp tubes and it sounded even awesomer. However, I was warned not to run the amp this way as it would screw up the transformer.
I was at a jam one day with a guy with an amp supposedly modded for Rod Piazza. I looked in the back and noticed one of the preamp tubes was missing. Is there a mod that involves removing one of the preamp tubes?
|
Oxharp
71 posts
Feb 25, 2009
1:29 PM
|
Hi Bluzlvr,
I cant speak for your concert amp. but you should not run the amp with any valve missing even to expeirment.
There is a lot of voltage flying around in there and you dont know what its doing to compensate for the missing valve. The missing pre amp valve from the Rod Piazza mod you looked at was at a guess the rectifier missing or a solid state rectifier was replaced. These look nothing like a glass valve and are a black plastic cylinder half the size of a normal valve and may have looked like there is not one in there as they are so small.
Maybe i am wrong but who knows eh. I dont do anything without finding out from a good source (My Amp Tech).
|
bluzlvr
127 posts
Feb 25, 2009
2:08 PM
|
I had a big enough scare against pulling one of the tubes by none other than the late Red Rhodes who used to work for Groove Tubes that I would never do it again.
In the case of the amp I saw, it was definitely one of the pre amp tubes. (Maybe he was playing with fire so to speak.) His amp definitely sounded bitchin'.
By the way Oxharp, I'm enjoying listening to West Weston on your YouTube channel. That swing instumental he does sounds like somebody from right here in Los Angeles, Left Coast U.S.A.
|
bluesnut
59 posts
Feb 25, 2009
3:55 PM
|
Buy the SJ 410. I spent the extra money so I wouldn't need mess around with modifications and it sounds killer right from the first note. You will not be disapointed, I'm not. To change the tone you just need to change around the tubes and nobs or add pedals to your taste. To get the Chicago tone I like the stock settings and tubes, no pedals. Just plug and play. Last night I took of the panel cover to the circuit board and I swear I could see tone dripping off the capaciters and the speakers like honey. Amazing Amp! The Bassman RI that I played thru sounded like it was made for guitar. The warm tone was absent and I used my Turner +2 mic on the RI. I was in the amp test room To compair the SJ with other amps and test effect pedals. The the guy in the music store used this phrase, your amp is much warmer than other amps in here. I just told him it was a harp amp. Stock tube line up from the back view, left to right are, Rectifier 5U4, Power tubes 6L6 6L6, Preamp tubes- #1. Inverter 12AY7 #2. bright volume 12AU7 #3. normal volume 12AT7. Start off tone settings are Presence 5, middle 2-3, trebble 4-5, bass 9-10. After that it's up to your own ears.
Last Edited by on Feb 25, 2009 4:35 PM
|
Bluzdude46
27 posts
Feb 26, 2009
9:17 AM
|
Thanks guys for your help. I picked up the '59 LTD Re-issue last night and if Oxharps description is correct I have V1 = 12au7 V2 = 12at7 and V3 = 12ax7 Sounds pretty sweet and boy does it have power! Of course by the time I got home and switched tubes it was later and I really didn't drive it. Planning on doing that tonight at home before I head out to a Jam.
Wonder if the guitarist will ask me to turn down?....Just kidding
|
Bluzdude46
28 posts
Feb 26, 2009
9:21 AM
|
Ok on the speakers. It contains the Light Blue Jenson P10's I may in the future change 2 of the speakers out for Eminence which I love for harp. I've heard good things out of this combination. For now I'm going to wait until the speakers are broken in to see if I like them as they are.
|
Jim Rumbaugh
5 posts
Feb 26, 2009
10:42 AM
|
The following may be too electronic geeky or even wrong.
A few off the cuff remarks about bias, from my old electronics training days. But's it's been 30+ years since I've fooled with a good ole 6L6 push pull amp. So some of this info may be obsolete
There use to be 3 types of 6l6 tubes. 6L6 ga, 6L6gb, and the 6l6 gc. The GC tube needed a higher bias voltage to reach cutoff, the GA and GB were said to be the same. The GC could produce a few more watts than the GA and GB.
A higher bias allowed for maximum wattage output. A lower bias meant the tubes would not reach cutoff, therefore allways draw some power. In this mode, the amp goes from a class B amplifier to a class AB. Sometimes the classifaication was even broken into AB1 and AB2 depending on how much the tubes were conducting
You may prefer the sound/tone when the amp is running in AB mode. If so, enjoy it. I do not think there is a right or wrong. The trade off MAY be, lowered peak output (which you may want) and a shorter tube life due to the longer duty cycle of the tube.
|
