tubes for arc

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Re: tubes for arc

Postby jon_p » Sat Mar 07, 2015 2:59 pm

tony wrote:
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


Thanks
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Re: tubes for arc

Postby tony » Sat Mar 07, 2015 7:45 pm

i can lend you a pair of 6CG7 so you can try before you buy...
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Re: tubes for arc

Postby jon_p » Sat Mar 07, 2015 9:54 pm

tony wrote:i can lend you a pair of 6CG7 so you can try before you buy...


Thanks for the offer sir. Will consider and let u know.

While i was doing some reading i came across a concern...

"The new 6H30 tube from Electro-Harmonix.
Please note that this tube can not be used in place of 6DJ8 or 6922 tubes in other pre-amps; it can only be used in equipment that is designed for it.

The 6H30 tube type is generally not compatible with 6922 and ECC88 tube types."

is this correct?
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Re: tubes for arc

Postby tony » Sun Mar 08, 2015 7:51 am

jon_p wrote:
tony wrote:i can lend you a pair of 6CG7 so you can try before you buy...


Thanks for the offer sir. Will consider and let u know.

While i was doing some reading i came across a concern...

"The new 6H30 tube from Electro-Harmonix.
Please note that this tube can not be used in place of 6DJ8 or 6922 tubes in other pre-amps; it can only be used in equipment that is designed for it.

The 6H30 tube type is generally not compatible with 6922 and ECC88 tube types."

is this correct?


that is generally correct...
however, we have to look at how the 6H30 was biased in the circuit to know,
looking at the specs, one section the 6H30 is like two plates of the 6dj8....
while the 6dj8 and siblings are rated at low plate voltages, i have seen lots
of circuit using them at much higher plate voltages....
i have used the 6H30 in place of the 6CG7/6GU7 in my aikido preamp builds...
btw, i have 3 pairs of Sovtek 6H30, date code 03-09.....
but i am not selling them, i hoard tubes and have about thousand of them... 8)

btw, i see that you have a kt120 in place of the original kt88..
using the kt120 does not give you more power,
because you still use the same power supply...
what you bought instead is longer tube life expectancy....
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Re: tubes for arc

Postby hypertriode » Sun Mar 08, 2015 9:14 am

I have a pair of 6H30's for sale jon_p. Text me @ 09163457787 :-)

Rene Rivo
https://www.facebook.com/MusicHavenPH
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Re: tubes for arc

Postby jon_p » Mon Mar 09, 2015 7:52 am

Tony,

The kt120 came as stock tubes on the amp.

As for the 6h30...are there other brands aside from sovtek?

you mentioned that you hoard tubes? All from internet purchase?
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Re: tubes for arc

Postby tony » Mon Mar 09, 2015 8:23 am

jon_p wrote:Tony,

The kt120 came as stock tubes on the amp.

As for the 6h30...are there other brands aside from sovtek?

you mentioned that you hoard tubes? All from internet purchase?



i got my 6H30 here....http://www.rutubes.com/product/6n30p-dr ... 82cc-tube/
"OTK" mark on the tube makes it a military spec tube, that OTK mark is the stamp of the quality
inspector who did the testing and inspection of the tube, he can be identified because
of this marking and can land in jail if he makes grave errors...this is how seriously the Russians
are with respect to quality...and having worked in Russia for 6 years, i know this to be true...
so tubes without these marks are commercial grade ones...

about my over a thousand tube hoard,
80% are U$1 tubes, the rest are from local sources and stores that closed and stopped selling tubes,
there are still quite a number of them around...90% of my tubes are tv tubes, they are real NOS....
Last edited by tony on Mon Mar 09, 2015 9:42 am, edited 1 time in total.
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Re: tubes for arc

Postby jadis » Mon Mar 09, 2015 9:09 am

jon,

i found this in audiogon forums:

http://forum.audiogon.com/cgi-bin/fr.pl ... 1225939119

to me the best way is to ask ARC about the drop in substitute variants for the 6H30 tube. unfortunately, they do not take customer emails, you need to call them.
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Re: tubes for arc

Postby tony » Mon Mar 09, 2015 9:29 am

nice link jadis....

11-06-08: Reb1208
I would try plugging in a 6CG7/6FQ7 tube into the socket. Draws less heater current than a 6H30, has about the same gain and sounds MUCH better.


11-07-08: Alex_yakovlev
"I would try plugging in a 6CG7/6FQ7 tube into the socket."
This is a very strange idea. These tubes are not even close to 6H30 and their only similarity is their pin-out.


yup i have tried this on my aikido line preamp....
just when you think that you have found something new,
someone out there have toyed with the idea before... 8)

if the other models of ARC are to go by, then all the more reason to believe
that semi cons helped in the gain structure of this amp, after all jfets are like triodes without filaments...

i asked in our FB group and no one has free schematics, so your best bet is to contact ARC directly...
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Re: tubes for arc

Postby jadis » Mon Mar 09, 2015 9:53 am

tony wrote:
i asked in our FB group and no one has free schematics, so your best bet is to contact ARC directly...


That's true, Tony.
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Re: tubes for arc

Postby jon_p » Mon Mar 09, 2015 5:36 pm

Thanks sir(s).

More digging and research needed.

and the hunt goes on... 8)
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Re: tubes for arc

Postby jadis » Mon Mar 09, 2015 5:46 pm

Too bad power tubes are not 'auditionable' or home tested. :lol: I bought SED KT88s and Gold Lion KT88s without ever hearing them. It's a good thing that I like them better than the stock tubes they replaced, thought both sets were 6550s. In my early days of audio, an older hand told me, 'pag nagbili ka ng mas mahal na kable, basta isipin mo lang na mas maganda siyang tumunog kaysa dun sa luma mo pag uwi mo'. :D While I do not exactly practice that, it seems to have some realistic effect. :lol:
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Re: tubes for arc

Postby jon_p » Mon Mar 09, 2015 7:31 pm

jadis wrote:Too bad power tubes are not 'auditionable' or home tested. :lol: I bought SED KT88s and Gold Lion KT88s without ever hearing them. It's a good thing that I like them better than the stock tubes they replaced, thought both sets were 6550s. In my early days of audio, an older hand told me, 'pag nagbili ka ng mas mahal na kable, basta isipin mo lang na mas maganda siyang tumunog kaysa dun sa luma mo pag uwi mo'. :D While I do not exactly practice that, it seems to have some realistic effect. :lol:


I agree! :lol:

Have u had experience comparing kt88 vs kt120? If so, what is the diff? Power and sound?

Also read something about tube bias...according to what i read...57 milliamps for best results. Is this true? I set mine at 60 which is based on manual recommendation.
any experience or thoughts on this?
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Re: tubes for arc

Postby tony » Mon Mar 09, 2015 8:30 pm

jon_p wrote:
jadis wrote:Too bad power tubes are not 'auditionable' or home tested. :lol: I bought SED KT88s and Gold Lion KT88s without ever hearing them. It's a good thing that I like them better than the stock tubes they replaced, thought both sets were 6550s. In my early days of audio, an older hand told me, 'pag nagbili ka ng mas mahal na kable, basta isipin mo lang na mas maganda siyang tumunog kaysa dun sa luma mo pag uwi mo'. :D While I do not exactly practice that, it seems to have some realistic effect. :lol:


I agree! :lol:

Have u had experience comparing kt88 vs kt120? If so, what is the diff? Power and sound?

Also read something about tube bias...according to what i read...57 milliamps for best results. Is this true? I set mine at 60 which is based on manual recommendation.
any experience or thoughts on this?


3mA difference is nothing......
biasing tube amps, you have a choice of class B or AB,most amps for hifi are either AB or A,
class B is used mostly for public address amps, where fidelity is not priority...

manufacturers know the levels of B+ in your amp so they made life easier for you
by giving you values of currents to set instead....80% of plate dissipation is typical
setting, so that if the kt88 can do 40 watts plate, then it is biased in such a way
that it runs with 32 watts idle dissipation....more or less....

tube life depends on how hot you run your tube, run it maximum rated dissipation and it gives you shorter life then,
run it cold and it gives you longer life...depends really on the manufacturer and the distortion figures they quoted...
lower distortion, means hotter bias but shorter life...and vice versa....

there are times when running hot and running cold does not give you any difference in sound....
the lowest setting that gives you a good sound is what i will aim for it that were my amp...

the last power amp i built was a push-pull using 6550 tung-sol tubes....
looking to build a Russian GU50, a quad can do 150 watts power channel... and at U$4 a piece, very cheap.....
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Re: tubes for arc

Postby jon_p » Tue Mar 10, 2015 6:39 am

Thanks tony.

Target the lowest possible setting for best sound and longer tube life. Will surf on this for my amp.
:)
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Re: tubes for arc

Postby tony » Tue Mar 10, 2015 8:08 am

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Re: tubes for arc

Postby jadis » Tue Mar 10, 2015 8:25 am

jon_p wrote:
Have u had experience comparing kt88 vs kt120? If so, what is the diff? Power and sound?


So far none. I toyed with going KT120 before I got the Gold Lion KT88s, but after chatting with some people who had the KT120s and knowing its sonic character, I decided that may not be the tube for me. How I miss the SED Winged C KT88s, which are out of production now.
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Re: tubes for arc

Postby tony » Tue Mar 10, 2015 8:36 am

jadis wrote:
jon_p wrote:
Have u had experience comparing kt88 vs kt120? If so, what is the diff? Power and sound?


So far none. I toyed with going KT120 before I got the Gold Lion KT88s, but after chatting with some people who had the KT120s and knowing its sonic character, I decided that may not be the tube for me. How I miss the SED Winged C KT88s, which are out of production now.


right on.....not getting the kt120 is nothing to lose sleep about....
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Re: tubes for arc

Postby tony » Tue Mar 10, 2015 8:37 am

jon_p wrote:Thanks tony.

Target the lowest possible setting for best sound and longer tube life. Will surf on this for my amp.
:)


if you overdo your biasing, red plating will happen, in this case just back down and your tube is safe once again...
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Re: tubes for arc

Postby jon_p » Tue Mar 10, 2015 8:14 pm

so kt88 sounds better than kt120?

I actually read it also that people prefer kt88.

So when my kt120's burn out should i get kt88 instead?
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