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EQUIPMENT FORUMS >> SE34I.5 >> Se341tube replacements
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Message started by Alainjoel on 03/27/13 at 20:20:16

Title: Se341tube replacements
Post by Alainjoel on 03/27/13 at 20:20:16

Will the se341 I just received accept kt77 and kt88 tubes?

Title: Re: Se341tube replacements
Post by Lon on 03/27/13 at 21:52:29

Congrats!

Yes, form the page for the amp:

https://www.decware.com/newsite/SE34I.htm

The output tube section was upgraded with the Hazen Grid Mod pushing the performance and fidelity of the EL34 beyond what any of us thought possible. And the amp is now also compatible with KT77, KT88 and 6550 output tubes.

I don't thnk the Hazen Grid works on these other tubes however, just EL34 and 6CA7 (pentode type) tubes.

Title: Re: Se341tube replacements
Post by hifitubes on 04/17/13 at 08:25:41

Wow, I didn't know we could use KT88/6550. Interesting, those are supposed to sound great in Triode regardless of Hazen mod.

Title: Re: Se341tube replacements
Post by hifitubes on 04/17/13 at 11:44:24

What about KT90? These tubes require .2 to .3 amps more heater current
than KT-88s.

Doubt we could run the new KT120:

Quote:

The #1 issue in subbing KT-120s for KT88s is the heater current draw. The nominal spec is 1.9 amps per KT-120 vs. 1.6 amps per KT-88. For a stereo push-pull amp that's a difference of 1.2 amps, and that is beyond the capability of some power trafos.

UNLESS YOU ARE 100% SURE THE POWER TRAFO CAN PROVIDE THE ADDED HEATER CURRENT SAFELY DO NOT USE KT-120s! You may be able to mod your unit to add the juice you need, but don't just plug them in. Even if the trafo seems okay at first, it may cause trouble down the road.

I do not recommend use of the KT-120 in the Citation II amp because of the heater current draw issue - you must add current capability to do it safely.

Quote:

"With a plate dissipation of 60 watts, the Tung-Sol KT120 is the most powerful tube in the 6550/KT88/KT90 family. A pair of these tubes in push-pull configuration can deliver power levels of 150 Watts or more. When it's run in circuits designed for 6550/KT88/KT90 tubes, the KT120 resists being overdriven and reliably delivers peak power. (View KT120 spec sheet and curves.)

The KT120 has a taller glass bottle, longer internal plate structure, and much larger control grid cooling fins than current production KT88 tubes. Because the KT120 draws 100-300 mA more filament current than a standard 6550/KT88, check with your amp manufacturer to ensure you have the additional filament headroom to power these tubes. This new production Tung-Sol tube is manufactured in Russia for New Sensor. "

Title: Re: Se341tube replacements
Post by Steve Deckert on 04/19/13 at 05:44:07

While the amp is compatible, it is biased for maximum sound quality with EL34/6Ca7. Anything larger than the KT77 is likely going to sound leaner due to the fact that the bias setting will be on the low side for these tubes.

Steve

Title: Re: Se341tube replacements
Post by hifitubes on 06/06/15 at 19:39:40

Steve,

With the new bias mod will kt88 be more sonically feasible?

Title: Re: Se341tube replacements
Post by 4krow on 08/10/15 at 07:02:54

I just gotta ask, the bias on my tubes is now about 38 ma. I'm thinking that the amp doesn't sound quite up to par lately. Could this lower bias reading be the reason? I will try another set of output tubes tomm.

Title: Re: Se341tube replacements
Post by hifitubes on 08/11/15 at 14:38:10

Maybe, I know that if I adjust the voltage Rachel gets, by changin the Ps audio p3, it affects bias. I think I have to set at 118 at Stevens rec

I'm thinking of trying some psvane el34 if someone wants to split a quad. Found a guy who uses an at1000 and tv10 to test. I haven't had great luck with psvane in the past though. Might pick up some SED first to compare to NOS telsa I have.

Title: Re: Se341tube replacements
Post by 4krow on 08/11/15 at 20:40:03

Yes, I certainly agree that changing the AC input voltage would affect the bias, since they would be relative.
As luck would have it I misplaced the original output tubes that came with the amp. This is not unusual for me to do. One answer that I use is to just buy another set until the others pop up.
Noticing a change in the Rachael made me think about other stuff. Specifically, that I noticed a perceived change in another amp that I own which is SS. Yup, you know where I'm going with this, and unfortunately, the answer is not something that I can do much about. It has happened in the past that my ears have good days and not so good days. Other than the fact that I am human, I have little answer to fall back on.

Title: Re: Se341tube replacements
Post by 4krow on 08/18/15 at 22:05:21

AHA! Found those Ruby tubes that I was looking for. As it turns out, the original tubes were in the amp, and the Rubies misplaced. Anyway, the Ruby tubes are biasing at 40-42 ma, and the sound is much like what I remember. I'm now thinking to get a set of backup tubes so I don't have to scurry too much next time.

Title: Re: Se341tube replacements
Post by hifitubes on 08/19/15 at 06:35:20

That makes sense. Bias mod takes that up even higher IIRC.

Never heard back on KT88 viability, so I picked up a pair of SED Winged C to compare to the NOS Teslas, of which I have 3.

Title: Re: Se341tube replacements
Post by 4krow on 08/20/15 at 03:28:44

hifitubes,

I have been thinking about the bias mod being done on the rachael. I am so happy with the sound overall, that the transformer mod doesn't appeal to me at this time. Finding the right tubes was enough for me. The bias mod not only raises the bias, but places the meters closer in the circuit, electrically speaking. I am not sure what this may mean literally, but it does call my attention.

Title: Re: Se341tube replacements
Post by hifitubes on 11/10/15 at 05:57:05

I'm happy so far, it's just as quiet and the tubes bias a little hotter. I feel it's worthwhile as I seem to get more headroom, tons of clarity.

I'm waiting on more EL34s and maybe I should try the Genalex KT77 again

Title: Re: Se341tube replacements
Post by Louis on 05/22/20 at 22:15:27

Greetings. New to the forum, new to the tube world. Question about rectifier tubes (for the Se341): What are the differences between a 5U4G, 5AR4, and 274b. Like physical differences, pros and cons of using either one w/ the Se341, safer to use, sound quality. Thanks in advance, Louis

Title: Re: Se341tube replacements
Post by Tommy Freefall on 05/23/20 at 01:05:06

I have used both 5U4Gs & a 5AR4 in my Rachael, and did not discern a material difference.
But my listening was casual not focused.