• Supporting Membership Changes

    The Supporting Memberships are currently being updated moving forward.

    In order to coordinate giveaway drawings to the Supporting Members there will be a new alignment in the naming of the tiers. (Note: Non-Supporting (Basic) and Monthly Supporting Members can get into the drawings by mailing a postcard. Details on that will follow with a giveaway starting soon).

    The pricing for each Supporting Membership level remains the same though the naming of them will change. The privileges remain the same as current but with the new name. If you are a current Supporting Member, you will be upgraded automatically for the existing term of your Supporting Membership. We are introducing a new tier with new perks.

    Table here

    Supporting Membership Guide

    • Monthly Supporting Members will remain Supporting Members
    • Current annual Supporting Members will now be Silver Supporting Members. Perks and permissions remain the same
    • Current Silver Supporting Members will now be Gold Supporting Members
    • Current Gold Supporting Members will now be Platinum Supporting Members
    • A new level will be created - Double Platinum Supporting Members

    All memberships will now have the option to remain as non-recurring memberships or choose reccuring memberships moving forward. *Note: current memberships will NOT be changed to recurring memberships.


Switched from KT88's to EL34's in my Bogner 20th Shiva. Findings/Results.

RockStarNick

Silver Supporting Member
Messages
3,631
Hey guys. So last night, I finally bit the bullet and performed some minor amp-surgery, and swapped the KT88s with EL34s in my Bogner Shiva 20th Anniversary.

Here's my findings, in bullet point style:

TECHNICAL FINDINGS:

• A resistor change IS necessary to go from KT88's to EL34s. In my particular amp, R61 had two piggybacked resistors. There was a 33K resistor closest to the board (Blue 5 band resistor: Orange, Orange, Black, Red, Brown). Piggybacked on top was another 5 band resistor.

• With both resistors in place, it was *IMPOSSIBLE* to get the bias above 4 or 5 with EL34s.

• With the piggybacked resistor snipped, I was able to get the EL34s into the proper bias range, per Charley @ Bogner (28-29mA at idle).

• The bias pot is in correct range for EL34s at about noon or 1 o'clock (with the resistor snipped).

• Per Charley at Bogner, when you start cranking the amp, you can visibly see the bias drift upwards about 4-5 points. Even MORE so if you slam a big chord. I can confirm this.

• Plate voltage seemed to stay just about the same, with KT88s or EL34s, give or take 10 points.


THE MODIFICATION PROCESS:

• Performing this resistor snip was relatively easy, provided you do it slowly, and safely. I made sure to drain the filter caps, use very small and delicate rubber-handled wire-clippers, and kept one hand behind my back at all times. (I also covered the big can capacitor directly adjacent to the resistors, with a rubber jar-opener, to ensure that the metal from the pliers did not come in contact AT ALL with the cap.)

• This whole operation was very easy to do, BUT, is pretty much "USER IRREVERSIBLE" unless you know how to properly (and safely) solder on an amp PCB. (i.e. draining the filter caps so you don't get shocked to death).


MY PERSONAL OPINIONS:

• So many people said that the new 20th Anniversary shiva was a "total circuit overhaul" and "a totally different amp". I don't believe that. Especially now after I made the swap. I believe that the circuit had things ADDED, like the gain modes, the new clean channel EQ boost circuit, and the mid cut button. But I don't think the amp was totally redesigned from the ground up.

• I truly believe that all Shiva models, whether it be 20th Ann, or regular, were designed with standard tubes in mind. EL34s or 6L6s. The reason I say this: My Shiva had piggybacked resistors in the "R61" spot (the resistor which controls the range of the bias pot). If the amp was designed around KT88s, why not either a.) put ONE resistor in there, or b.) have two spots on the board?

• I think the KT88s DO completely change the overall EQ of the amp, and it's overall personality. Depending on your playing style, this can be good or bad.

• The KT88s sound harder, tighter, and much more present. They have a much more aggressive upper-mid cut than the EL34s. Much more cutting and modern sounding. The abundance of upper mids and presence definitely changes the percieved EQ curve of the amp.

• EL34's immediately changed the personality of the amp. It sounds more vintage, softer treble, less modern, less in your face. The softer trebles of the EL34s change the apparent EQ curve of the amp and make it more even across the board. The amp might seem like it has more low-mids now. It doesn't really - it just has MUCH less treble/upper-mids.

• Clean sounds are VERY different as well. The KT88s are bigger, bolder, and have a shimmering glassy top end. The EL34s are chimey, with that distinctive "hazy" top end - No sparkly fender cleans here. If you need presence and sparkle for cleans for modern chorus-delay arpeggios or tons of headroom, stick with the KT88s. If you like to have some breakup and warm grit in your clean, then EL34s will work.

• Neither tube sounds BAD in the amp, in any way! Both sound amazing. But it is nice to know that you can tweak the amp to your personal preference.

- Nick
 

MightyGuru

Member
Messages
6,981
Thanks for posting, Nick. very helpful...and brave of you! Rock.

So, the 20th with EL34s sounds just like a classic Shiva in the normal/vintage modes?
 

Lution

Member
Messages
8,931
Thanks for the report. I was very curious about this.

Love my 2002 EL34 Shiva. It just sounds right. Both Channels are amazing!
 

RockStarNick

Silver Supporting Member
Messages
3,631
Thanks for posting, Nick. very helpful...and brave of you! Rock.

So, the 20th with EL34s sounds just like a classic Shiva in the normal/vintage modes?
Not sure, because I don't have them side by side. But from my memory of owning a 2002 EL34 shiva, and text driving a new EL34 Shiva and a 20th side by side a few months ago, I can say that the 20th w EL34s can get very close to the standard shiva if needed.
 
Messages
1,721
Cool post! It's nice to see what you thought about the comparison of the two sets of tubes. Your findings seem to be very similar to what I came up with when I compared a 20th Anni Shiva head to an EL34 head. It really did seem like there was a bump in the low mids with the EL34 model, but in hindsight, I'm wondering if you're right, and it's just that my ears were used to the sound of the 20th Anni already by that point. Cool post though. Thanks for sharing your findings!
 
Messages
344
good read.
I've been thinking of doing the opposite to my Sound City.
Take the six EL34's and putting in four KT88's. I use the head more for bass and clean only guitar as I use a TS for low gain.
 

MGSchindel

Member
Messages
941
These findings are also generally consistent with what you'd experience when switching 6550's out for EL34s in older, converted marshall amps, like early JCM800 2203's/2204's.
 

Flameout12

Member
Messages
1,178
These findings are also generally consistent with what you'd experience when switching 6550's out for EL34s in older, converted marshall amps, like early JCM800 2203's/2204's.
I've done some of this with my 2204 combo & find the EL34s to have more compression and flex at lower volumes. 6550s sound much bigger and bolder, but also more stiff and less toneful....at least what I can tell.
 

prsnstrat

Member
Messages
1,898
Personally I didn't like the El34 in the shiva. 6L6 was better to me. I'm a BIG fan of kt88 tubes so I'm sure I'd love the 20th Ann Shiva. I just don't know if I can go there a third time! lol
 

se7en

Senior Member
Messages
366
I've done some of this with my 2204 combo & find the EL34s to have more compression and flex at lower volumes. 6550s sound much bigger and bolder, but also more stiff and less toneful....at least what I can tell.
This is my experience with a KT88 to EL34 conversion on my Twin Jet. The 34's made the amp more toneful and more saturated. The KT88's sound hi-fi, more open, glassy and don't have as sweet of a midrange.
 

frankencat

Guitarded
Silver Supporting Member
Messages
12,894
Personally I didn't like the El34 in the shiva. 6L6 was better to me. I'm a BIG fan of kt88 tubes so I'm sure I'd love the 20th Ann Shiva. I just don't know if I can go there a third time! lol
I wouldn't consider it going there a third time. The 20th Shiva is a completely different beast of an amp. I have had two of the older Shivas, a 6L6 and an EL34. This amp eats those for breakfast. OR to paraphrase the late great Phil Hartman as Sinatra on SNL...'this amp has chunks of amps like that in it's stool'. ;)



P.S. Nice to see 3 active 20th Shiva threads going on TGP tonight. :)
 

MightyGuru

Member
Messages
6,981
Gigging the 20th Ann'y Shiva the last 5 days/6 gigs. I actually prefer the strat overdrive tones with this amp over the RedPlate Magic Dust. It gets a cool old school kerrang and can get pretty brown even using a strat/w single coils.

The clean tones are big, bold and have an extended higher mids even with an EV/SRO ceramic. The RedPlate's cleans are more balanced and richer in the mids.

I would still love to try the EL34 mod...gotta find a reliable tech in Central Florida. I loved the cleans on my old Cosma Shiva.
 

stratzrus

Philadelphia Jazz, Funk, and R&B
Silver Supporting Member
Messages
20,874
Great post Nick. :aok

You've got me worried now though.

I'm putting KT90s in my Sig:X but the things you said about the cleans coming from KT88s are one of the things I really like about the Siggie.

Hopefully I'll get more of what I like about 6L6s (solid bottom end) and EL34s (singing lead gain tones with midrange complexity) without losing too much of what I like about the KT88 cleans (pristine with sparkling high end full of detail).
 

rreiser

Supporting Member
Messages
1,874
I'm trying KT-88s for the first time in my amp. I am very impressed so far. I thought they would be too sterile but I am finding they are very balanced and I like the extra punch and girth from the extra power. I don't notice a huge volume increase. I'm just in the honeymoon phase but I'll know more when I gig with the 88's.
 




Top