tubes for arc

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tubes for arc

Postby jon_p » Thu Mar 05, 2015 1:02 pm

Hello ws members.

thinking of replacing the tubes of my arc vsi60 int amp.

Any recommendations?

Tia! :)
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Re: tubes for arc

Postby JackD201 » Thu Mar 05, 2015 2:00 pm

Hi Jon

Nice amp! Which tubes are you thinking of replacing and what sound are you after?
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Re: tubes for arc

Postby jon_p » Thu Mar 05, 2015 4:34 pm

JackD201 wrote:Hi Jon

Nice amp! Which tubes are you thinking of replacing and what sound are you after?


sir jack

Am thinking of replacing the original tubes. Currently kt120 and sovtek 6h30.

Honestly...i have no idea on the different tubes and their corresponding characteristics.

am hoping that you/ws members/audio gurus here can enlighten me and probably provide some options.

tnx
jon
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Re: tubes for arc

Postby jadis » Thu Mar 05, 2015 8:46 pm

Hi Jon,

I've used SED KT88 on my VS110 in the past, and now have Gold Lion Reissue KT88s on my VS115. It's hard to compare both sets as the 2 amps have different characteristics, but I was fond of the SED kt88/Arc115 for its warmish tone. Extremes are a bit rolled off, which is the opposite of the ARC115/GL Kt88s combo. I personally am looking at the Psvane series of KT88s. I'm not inclined to go 120s and 150s based on what people tell me - more power, but whitish character is not what I'm looking for. As for the 6H30, I'm stuck with the stock brand. :)
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Re: tubes for arc

Postby JackD201 » Thu Mar 05, 2015 9:11 pm

Ahhh it's a KT120 and 6H30 based amp. AFAIK only Reflektor is making KT120s although that may not be the case anymore. As 6H30's go the only other option is the supposedly better DR variant again only as far as I know.
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Re: tubes for arc

Postby jadis » Thu Mar 05, 2015 9:53 pm

JackD201 wrote:Ahhh it's a KT120 and 6H30 based amp. AFAIK only Reflektor is making KT120s although that may not be the case anymore. As 6H30's go the only other option is the supposedly better DR variant again only as far as I know.


That's true, Jack. Only the DR is available. I wish ARC would use the 6922 types again, for more choices of tubes to roll.
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Re: tubes for arc

Postby dafos » Fri Mar 06, 2015 6:58 am

jon_p wrote:Hello ws members.

thinking of replacing the tubes of my arc vsi60 int amp.

Any recommendations?

Tia! :)


The latest direction for ARC is to replace the Kt 120 for the new Kt 150 used in Galileo power amp and now on the ref 75, 150 and 250. From what I've read, there should be no problem doing the replacement for your vsi 60 so long as it fits since the kt 150 is physically larger.
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Re: tubes for arc

Postby jon_p » Fri Mar 06, 2015 12:39 pm

Sir(s)...jack, jadis, dafos...

Many thanks to your replies.
seems like i need to read on "tubes 101" to get a better understanding on tubes and their corresponding charateristics.

pardon my ignorance...

given the stock tubes on my amp, what tube upgrade do i look for?

the big tubes give the power and small tubes define character?

should i look for 6922's?

i also asked caloy and he recommended the same.
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Re: tubes for arc

Postby jadis » Fri Mar 06, 2015 3:26 pm

jon_p wrote:Sir(s)...jack, jadis, dafos...

Many thanks to your replies.
seems like i need to read on "tubes 101" to get a better understanding on tubes and their corresponding charateristics.

pardon my ignorance...

given the stock tubes on my amp, what tube upgrade do i look for?

the big tubes give the power and small tubes define character?

should i look for 6922's?

i also asked caloy and he recommended the same.


Jon,

From what I know, the 6h30 cannot be substituted by any variant except its same number. So 6922 cannot be used in your amp.

By the way, are your power tubes weak already ? Or any manifestation of bad sound due to them?
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Re: tubes for arc

Postby tony » Fri Mar 06, 2015 5:58 pm

depending on the circuit, but 6CG7 can drop in, in place of the russian 6H30
so with the 6922/6dj8 variants, since they all share the same pin-outs
most likely these will work.....small tubes are always operated at a fraction of
their specs and so live a longer life compared to power tubes....

the 6N30 will have more gain than the 6CG7, but the 6CG7 is a 6sn7 in a small bottle....
the 6922, 6dj8 and siblings will have the same gain as a 6N30 but is lower plate dissipation ratings...

re KT120/150, not a big leap from the kt88, for the price...
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Re: tubes for arc

Postby jon_p » Fri Mar 06, 2015 10:41 pm

Jadis,

So far so good for the power tubes. what signs/sound defect am i suppose to hear?
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Re: tubes for arc

Postby jon_p » Fri Mar 06, 2015 10:44 pm

tony wrote:depending on the circuit, but 6CG7 can drop in, in place of the russian 6H30
so with the 6922/6dj8 variants, since they all share the same pin-outs
most likely these will work.....small tubes are always operated at a fraction of
their specs and so live a longer life compared to power tubes....

the 6N30 will have more gain than the 6CG7, but the 6CG7 is a 6sn7 in a small bottle....
the 6922, 6dj8 and siblings will have the same gain as a 6N30 but is lower plate dissipation ratings...

re KT120/150, not a big leap from the kt88, for the price...



Thanks for the reply sir.

Several choices u mentioned above. Wc do u recommend?
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Re: tubes for arc

Postby jadis » Sat Mar 07, 2015 7:07 am

jon_p wrote:Jadis,

So far so good for the power tubes. what signs/sound defect am i suppose to hear?


That's good, jon. I personally have not reached a point (knock on wood) where I thought the power tubes were weak or failing as I usually replace them before they get real weak but I would imagine noise or distorting sound as signs of trouble. I heard too about power tubes getting real red and the silver mica wearing thin as sings of trouble or aging. And also when they couldn't be adjusted to reach the bias point of the amp anymore, that should be another sign. Depends really on how often they are used as power tubes are said to have a good working life of 2000 hours.
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Re: tubes for arc

Postby jon_p » Sat Mar 07, 2015 9:11 am

thanks jadis for the tips.
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Re: tubes for arc

Postby tony » Sat Mar 07, 2015 9:14 am

jon_p wrote:
tony wrote:depending on the circuit, but 6CG7 can drop in, in place of the russian 6H30
so with the 6922/6dj8 variants, since they all share the same pin-outs
most likely these will work.....small tubes are always operated at a fraction of
their specs and so live a longer life compared to power tubes....

the 6N30 will have more gain than the 6CG7, but the 6CG7 is a 6sn7 in a small bottle....
the 6922, 6dj8 and siblings will have the same gain as a 6N30 but is lower plate dissipation ratings...

re KT120/150, not a big leap from the kt88, for the price...



Thanks for the reply sir.

Several choices u mentioned above. Wc do u recommend?


up to you really, i suspect that this ARC amp is helped along by semicons
like op amps get the right gain structure like what i have seen in some of their offerings...
and that the 6H30 could be cathode followers driving grids of the KT120....
if you can ask a friend to lend you a 6CG7 or even a 6GU7, then that is a good place to start...
you will be in for a surprise, or maybe not...nothing wrong in feeding your curiosity... ;)
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Re: tubes for arc

Postby tony » Sat Mar 07, 2015 9:19 am

jon_p wrote:thanks jadis for the tips.


a heavily used tube will have unmistakable signs right on the glass itself,
you will see burn marks opposite plates with holes and other places...
and the flash gettering will fade in time, you may be able to see filaments burning but no sound is coming out....
definite sign that tube replacement is imminent....
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Re: tubes for arc

Postby jon_p » Sat Mar 07, 2015 10:01 am

Thanks tony. Will look around for tubes.

Any recommended sellers?

Just checked the kt120's...
All have burn marks already!
Maybe just in time for my querry here in the forum as i may need replacements asap.
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Re: tubes for arc

Postby tony » Sat Mar 07, 2015 10:13 am

jon_p wrote:Thanks tony. Will look around for tubes.

Any recommended sellers?

Just checked the kt120's...
All have burn marks already!
Maybe just in time for my querry here in the forum as i may need replacements asap.


i get my tubes mostly from online sellers...
6CG7 are still available at pacific electronics for 400 ucks...
burn marks does not necessarily mean the tube is bad, but that the tube is heavily used na....
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Re: tubes for arc

Postby jon_p » Sat Mar 07, 2015 11:04 am

Pls advise recommended online shops...i will start the research... :)

Thanks
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Re: tubes for arc

Postby tony » Sat Mar 07, 2015 11:08 am

jon_p wrote:Pls advise recommended online shops...i will start the research... :)

Thanks


tube depot....https://www.tubedepot.com/t/tubes/pream ... /6cg7-6fq7
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