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Any approach we can make 6h30 warmer and richer?

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Posted on January 30, 2017 at 03:44:02
Eric Chan
Audiophile

Posts: 84
Joined: October 31, 2001
Any thought to make the 6h30 mid band to sound warmer, richer,smoother and more creamy?

I have seen that running at 20mA/100V per section is recommended by BAT Victor, apart from that what other approach or brand of resistor/couple cap you would recommend?

 

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RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 04:04:37
Michael Samra
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I would try some of the 6sn7s or a different 6h30P.There are a few things you could do to make the amp smoother,richer,and more elegant. Put in paper in oil coupling capacitors.The Russian KBGN are wonderful caps and don't let the low price fool you because they are military surplus and if they built this cap today they would easily be 100usd or more each.You could also put in Schotky/Cree diodes in the power supply. Do you know the values of the coupling caps in your unit?

"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

have you tried the 6N30P-DR? (n/t), posted on January 30, 2017 at 06:34:15
FenderLover
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mt

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 07:46:31
Eli Duttman
Audiophile

Posts: 9355
Location: Monroe Township, NJ
Joined: March 31, 2000
High gm types, like the 6n30p, are particularly vulnerable to parasitic oscillation. Parasitic oscillation at VHF or higher frequencies can cause "hard" sound. Use carbon comp. grid stoppers of substantial value and 100 ohm carbon film stoppers on the plates.

Eli D.

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 08:20:07
Chip647
Audiophile

Posts: 1629
Location: The South
Joined: December 24, 2012
Warm and rich can be measured. Looking at system frequency response, distortion, and oscillation will tell you a lot.

You may have a system which is too bright being driven well. Sometimes designers counteract the fact that their circuits are being driven by something whimpy that cannot overcome miller capacitance and cable losses, so they make stages bright to compensate. This is not a bad thing in that in can make the total system flatter. When you put a good drive circuit in the mix it can make things bright. You may have to tame the frequency response to warm things up. In olden times there were knobs with the words "Treble" and "Bass" on them. Those were crazy times.

You are making and listening to a system, not a component.

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 08:38:57
PakProtector
Audiophile

Posts: 11228
Joined: May 14, 2002
and finding spurious 'puffs' of oscillation is difficult at best.

Stoppered adequately, I have not found anything wrong with them.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 13:10:05
Eric Chan
Audiophile

Posts: 84
Joined: October 31, 2001
Thanks everyone for all inputs

The Rp of 6h30 is 820 ohm. Any gain or output impedance impact if I add 100 ohm to its plate as plate stopper then ?

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 14:49:30
Tre'
Industry Professional

Posts: 11942
Location: So. Cal.
Joined: February 9, 2002
"The Rp of 6h30 is 820 ohm"

At what operating point?

Yours?

Va Ia Vg1 Gm Mu Ra (Rp)(ohms)
50 5 -2.8 7.1 15.2 2100
50 10 -2.3 9.8 15.9 1600
50 20 -1.5 12.3 16.3 1300
90 10 -4.7 8.4 15.3 1800
90 20 -3.9 11.7 16.0 1400
90 30 -3.1 13.3 16.2 1200
120 10 -6.5 7.6 14.9 2000
120 20 -5.6 10.9 15.7 1400
120 30 -4.8 12.9 16.1 1300
120 40 -3.9 13.3 16.3 1200
180 10 -10 6.5 14.5 2200
180 20 -8.9 10.0 15.3 1500
180 40 -7.1 13.3 16.0 1200
250 10 -14.4 5.8 14.4 2500
250 20 -13.2 8.7 15.0 1700
250 30 -12.1 11.0 15.4 1400
250 40 -10.5 12.5 15.8 1300

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 15:01:38
Dave Davenport
Manufacturer

Posts: 913
Location: North Carolina
Joined: March 20, 2002
I second Eli's recommendation to use grid stoppers and plate stoppers.

I suggest that you look elsewhere in your circuit to soften the sound. Capacitors and resistors are candidates.

Dave

 

What sized grid stopper should he try?, posted on January 30, 2017 at 18:35:18
FenderLover
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300-ohms?


Thanks!

 

RE: What sized grid stopper should he try?, posted on January 30, 2017 at 19:32:09
Tre'
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Location: So. Cal.
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I would give 300 ohms a try and if that doesn't stop the oscillation (if that's what he's hearing) then make it bigger.



Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Any approach we can make 6h30 warmer and richer?, posted on January 30, 2017 at 21:17:19
sser2
Audiophile

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Location: Pittsburgh USA
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Small RF chokes won't add resistance. Something like 15 turn spiral of 18 ga wire, 1/4" diameter.

 

RE: What sized grid stopper should he try?, posted on January 31, 2017 at 06:35:01
dave slagle
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Location: NYC
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This brings up an interesting parallel to the HFAC filament discussions. Elsewhere it has been insisted that we cannot hear the effects of HFAC since the frequency is well above what humans can here. If this logic is to hold true then surely we cannot hear an oscillation in the mHz range yet people claim the effects of an oscillating tube as a bright or harsh sound.

what gives?

dave

 

RE: have you tried the 6N30P-DR? (n/t), posted on January 31, 2017 at 07:28:44
Joe Appierto
Audiophile

Posts: 871
Location: Central NJ
Joined: January 3, 2004







EB on left and DR on the right.

I agree. Although they're harder to find and more expensive they do sound smoother, more detailed with a better top to bottom balance.
Joe

 

RE: What sized grid stopper should he try?, posted on January 31, 2017 at 07:55:35
Eli Duttman
Audiophile

Posts: 9355
Location: Monroe Township, NJ
Joined: March 31, 2000
IM distortion products inside the audio band are (IMO) a likely candidate.

Remember, IM distortion, even in small amounts, is highly irritating.

Eli D.

 

RE: What sized grid stopper should he try?, posted on January 31, 2017 at 08:27:21
Tre'
Industry Professional

Posts: 11942
Location: So. Cal.
Joined: February 9, 2002

If high frequency (above our hearing range) is just steady HF that's one thing.

If a circuit is falling in and out (parasitic) of oscillation at a rate that we can hear that's a different thing.

Just a thought.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Fugly! nt , posted on January 31, 2017 at 10:10:11
Eli Duttman
Audiophile

Posts: 9355
Location: Monroe Township, NJ
Joined: March 31, 2000


Eli D.

 

If oscillation is not the problem,..., posted on January 31, 2017 at 10:10:53
Lew
Audiophile

Posts: 8723
Location: Bethesda, Maryland
Joined: December 11, 2000
perhaps you might let the rest of us know what voltage and current you are supplying to the tube and what value plate and cathode resistors. Some of the gurus here may be able to help you more if you divulge that sort of info. And finally, as Mike Samra intimated, coupling capacitors have an outsize effect on the perceived overall coloration. So, what type of coupling capacitor are you using?

 

My experience, too., posted on January 31, 2017 at 11:27:10
FenderLover
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They last forever, in the correct setup. Maybe worth the $$$.


8^)

 

RE: If oscillation is not the problem,..., posted on January 31, 2017 at 13:23:19
Eric Chan
Audiophile

Posts: 84
Joined: October 31, 2001



Here come the schematic, a differential stage with 100V plate voltage and 5K plate resistor running 20mA per section

Coupling cap is RELCAP RT while all resistor are kiwame except grid stopper using holco

 

RE: If oscillation is not the problem,..., posted on January 31, 2017 at 13:45:12
Eli Duttman
Audiophile

Posts: 9355
Location: Monroe Township, NJ
Joined: March 31, 2000
The last thing to use in the grid stopper role is a metal film part.

Use carbon composition (CC) parts as grid stoppers. CC is both non-metallic and non-inductive. CC can be noisy, but the noise is related to the current carried. The current in a grid stopper is vanishingly small and noise is a non-issue.

Eli D.

 

rectification, posted on January 31, 2017 at 14:06:13
Ralph
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Often the problem with RFI in a circuit is when it gets rectified. When that happens any modulations become audible.

Preventing the RFI in the first place is the better move...

 

I don't think so., posted on January 31, 2017 at 14:14:19
Ralph
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We ran into that problem with that tube back in 1992 when it first showed up in the US.

If I were you, I'd rewire the socket for a 6CG7 or 12BH7, which are essentially a 6SN7 in a miniature format- and are much better sounding tubes.

The 6H30 was designed for instrumentation, and while very linear, is not good for audio due to microphonics and issues of ultrasonic oscillation, just like its brethren, the 6DJ8 and 6922 (both also frame grid triodes).

IME/IMO these tubes always have a touch of brightness about them that is not found in made-for-audio tubes. IMO the microphonics of the tube is somehow able to interact with the signal, creating a bit of IMD, but I have not proven that. At any rate they always seem to have a bit of unnatural iridescence. Its no problem getting similar bandwidths out of audio tubes.

If you really need the extra mu this might be a problem, but in most cases where this tube is useful (line stage, driver tube) you can usually get around it.

 

RE: What sized grid stopper should he try?, posted on January 31, 2017 at 16:52:13
Triode_Kingdom
Audiophile

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I've seen that so many times. This is one of the reasons it's so silly when people say engineering is unimportant.


--------------------------
Buy Chinese. Bury freedom.

 

RE: What sized grid stopper should he try?, posted on January 31, 2017 at 19:47:32
Eli Duttman
Audiophile

Posts: 9355
Location: Monroe Township, NJ
Joined: March 31, 2000
IMO/IME, in DIY projects, it's best to assume parasitic oscillation will be present and appropriate prophylactic measures taken, before a single connection is soldered into place.

Darned tootin, engineering matters. 1st, get the Physics right! Then, you know the field you're "playing" on. If Newton, Einstein, Maxwell, et al, say you are smoking loco weed, move on.

Eli D.

 

RE: I don't think so., posted on January 31, 2017 at 21:52:08
Eric Chan
Audiophile

Posts: 84
Joined: October 31, 2001
>> If I were you, I'd rewire the socket for a 6CG7 or 12BH7,

Using single stage of 12BH7 or 6SN7 does not give you the output impedance low enough to drive the power amp

Also, but how would CJ , ARC also make use of 6h30 for thier high wnd preamp model if the HF osc is that bad?

 

RE: What sized grid stopper should he try?, posted on February 1, 2017 at 00:26:58
Donald North
Manufacturer

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Good point Dave, I'm curious if HFAC heating has any IM artifacts in the audio band...

 

RE: I don't think so., posted on February 1, 2017 at 01:39:23
91derlust
Audiophile

Posts: 428
Joined: December 25, 2014
Finally, someone has alluded to it. Perhaps, just perhaps, the 6H30 is not capable of the desired sonics. I have read countless posts and opinions about this tube - even technically well-implemented, I doubt I could ever love it.

Like any tube, its sound can be mitigated (obscured?) by judicious component selection. Although acceptable presentation may be achievable in this manner, I don't believe musical greatness is achieved by trying to balance sonic extremes.

Cheers,
91.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

Why would a manufacturer choose this tube?, posted on February 1, 2017 at 06:51:06
FenderLover
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If its audio characteristics had these inherent flaws? I've never heard a unit that used the 6N30P. Only heard a couple Aikido that used 6N30P-DR tubes. They sounded pretty good to me. Maybe, the -DR versus plain 6N30P is a big difference?

I'd convert the unit to used the 6CG7, if the 6N30P has all these ultrasonic and IMD issues.

 

RE: I don't think so., posted on February 1, 2017 at 10:12:41
Ralph
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Using single stage of 12BH7 or 6SN7 does not give you the output impedance low enough to drive the power amp

This statement is outright just plain false. These tubes have been used as driver tubes in amplifiers for decades, and would work easily at the output of a preamp- and would be rather gutsy in that regard.

Also, but how would CJ , ARC also make use of 6h30 for thier high wnd preamp model if the HF osc is that bad?

That's a loaded question, but the short answer is apparently (IMO) 'not that well' (again, just my opinion; I don't think its all that hard to find better sounding preamps). One would hope that their gear lacks any HF oscillation tendencies! My impression personally is that microphonics (not oscillation) is really the big issue. I've seen some of these tubes that were so bad that you could yell at them and hear yourself in the loudspeaker. Its really hard to build an audio circuit that sounds right when the tube won't behave.

 

No component can be all things to all people., posted on February 1, 2017 at 12:19:35
91derlust
Audiophile

Posts: 428
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I'm not saying the 6H30 is flawed, more that I doubt I'd like its sonic signature. Preferences are personal and varied; there are plenty of components I might like to listen through and plenty I don't.

The DR version would probably be more to my liking - if I had to use the 6H30 that is what I'd be paying for. Still, if I were designing a component from scratch for personal use that needed a ~mu 20 tube, I'd be using something different.

Cheers,
91.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

RE: If oscillation is not the problem,..., posted on February 3, 2017 at 12:37:59
Scholl
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Also try snupping the heater voltages to supres high frequencies there too.

 

RE: What sized grid stopper should he try?, posted on February 9, 2017 at 10:53:11
PakProtector
Audiophile

Posts: 11228
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used to smoke loco weed in Newton...or was that eat Newtons after smoaking loco weed?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: What sized grid stopper should he try?, posted on February 9, 2017 at 10:57:27
PakProtector
Audiophile

Posts: 11228
Joined: May 14, 2002
Oscillation usually happens with grid current...and I once saw a 12BY7 LTP go singing away at a few tens of MHz...and the sonics were not very good at all...:) Now if it is a semi-regular oscillation, triggered by some of the program, getting harsh is quite likely, though you're not hearing the oscillation, it is the other side effects that present...:)

Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

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