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In Reply to: Re: Final SE Amp Tube Decision posted by zarniwoop on April 26, 2007 at 19:25:11:
I designed with what I had on hand.
I am in the poor house right now.
I went overboard and ordered the pair of KT77s.
I had designed this amp for KT90 CF operation.
I just didn't like the sound - not musical.
So I redesigned it using the same chassis -
even the same holes.
13 pieces of iron - heavy mutha!!!
Seperate LCLC filters
MQ Nickel Grid chokes
MQ EXO-01 Plate chokes
Mundorf Silver/Oil coupling caps
Edcor variable autotransformers
RCA 6J5GT input/driver tubes
Sylvania Fat Bottle GZ34
I sold the quad of EI KT90 Type 2s
so that I could buy Silk 5K OPTs.
I had the SED KT88s and GT KT66s.
I had originally designed it for the KT66s.
But as I said they didn't work out.
I didn't like the VA EL34s - borrowed from my Jolida.
I dug out the "Svetlana 6550s" that later turned out
to actually be KT88s that were labelled wrong.
They were my favorite sounding tube which
definitely surprised me.
I heard good things about the JJ KT77s so
I put them on my credit card and was disappointed.What Octal Triode do you suggest with a 5K OPT?
I have no more funds for different OPTs or
power transformers so 6.3V filament necessary.
They need to be driven by a 6J5 too.
This is my first SE tube amp that I have owned.
There are NO tubes around here - Albany NY.
If I want to hear tubes I have to buy/build it.
Follow Ups:
you will be very pleased: at least on the 6N1p. The 6j5 I don't know about, but the 6n1p likes this very much. you probably even have the cells around the house. You can get a 4 cell holder from Radio Shack.Don't try this: (you may have read this story before, sorry if I am repeating this)
I started experimenting with batteries on the cathode & grids with my then KT88 SE triode strapped 5 years ago. NiMh had really just started getting out on the market. I had soldered in my 4 cell Radio Shack AA battery holders, and as I didn't have my NiMh yet, and could find my NiCads, said hell, I'll try my regular 1.5V alkalines. So I put them in and behold: innnnnnncredddddible music, so I left them in to see how long they would last. One day I was so into it I listened _before_ I went to work, and let my lab supply which was running the amp turner on.
While I was at work, the heat from the tubes in the Lab Supply thordensen heated up the batteries in the amp (which was sitting directly above the Lab Supply: THE BATTERIES LEAKED, dripping their nasty stuff down onto the power transformer of the Lab Supply which was directly below them, shorting out the power supply.
Not much music happened that night. Also people are scared of the alkalines in this position, but there is no need. They will run down, and no longer function, but not leak massively like these under heat.
My KT 88 were shuguang and were quite damn good thanks.I ran it from choke loaded 12AT7 which had battery bias on the cathode.
As a whole it was excellent. The best INDHT I have heard.
-3dbMine are running at 400V and 60mA.
Into a 5K OPT - very relaxed sound.
It'll probably last forever too.
hey,
your amps sounds cool, i'm not trying to be critical.the only octal output triodes i know of are the 6b4g and 6a5g. the "new" sovtek 6b4gs are very robust. 5k OPT is great. 6j5 isn't the best driver, but if its choke loaded it may work well.
yeah, these things can get heavy. i did a stereo se 300b last year and i think it weighs in at 45lbs. now i'm trying to decide what to build next.
the only octal output triodes i know of are the 6b4g and 6a5g
yeah, those too, but not really output triodes, specifically. deflector and regulator pass tubes, but yes, they can work. I don't hear too many great things about paralleled 6as7 in SE, though.
I think by "real triode" zarniwoop meant a direct heated triode.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
DanL
particularly in the area of midrange definition. Besides, what have you got to lose by trying the 6BL7/6BX7 family? You could even just wire up one side of the tube - you'll still have a 10W dissipation rating (the second anode only adds 2W due to thermal proximity of the two sections). I have found these tubes to have an open, neutral sound that is much more appealing than triode-strapped screens. I would also suggest that you try running the tets/pents with fixed screens and appropriate NFB, just for comparison. I have always believed these tubes perform best sonically when operated in their native format.
TKMy midrange definition is quite awesome now.
The KT77s had too much definition for me.
Your recommendation of running pentode
with feedback disqualifies you in my opinion.
We are trying to get different sounds.
I have NEVER heard a pentode I didn't hate!
Sounds artificial and exaggerated to me.
As far as global feedback, heresy 8^D
Sorry nothing personal but not my cup of tea.
My KT88s sound very open and neutral to me.
I am listening to them right now and WOW.
Even just the Carver FM tuner sounds great !!!
Can't wait for my turntable to show up.
Staging and clarity with a flow that's awesome.
There are many different designs out there and
some appeal to one group and some to others.
I have VERY fast and articulate drivers so
definition can be too much real easily.
I wish to one day hear a DHT just to see.
No one has them in this area.
I went to a show just for that and
they didn't have any hooked up.
BUMMER !!!
> My midrange definition is quite awesome now. The KT77s had too much definition for me.Something is wrong with your system. The source defines limits on definition. Perhaps you've misidentified the effect, or you don't really like the music you've selected.
> Even just the Carver FM tuner sounds great !!!
Even processed through Carver's genius, FM broadcasting blows. Something is wrong with your system.
> I wish to one day hear a DHT just to see.
everyone have they own oppion .
I'm in love with my new 2A3 SE drivimg my Altec A5 system.
Cheers
LT
my response was based on what was posted. Taken together, I think the whole of the description points to significant issues with the system or listening environment. For one thing, I haven't heard an FM MPX broadcast that sounded good from an audiophile perspective for at least twenty years. The technology being used simply isn't compatible with this level of audio reproduction capability. I also suspect the description of excess definition to be something else, perhaps an unusual sensitivity to IM. In any case, something isn't right.
Hey Dan,Been away for a while and missed about a month of posts.
I say enjoy the Svet KT88s, when triode strapped they are one of the best non triodes around IMHO. Just look forward to the day you convert to DHTs for another dimension in that beautiful midrange you crave.
The tubes you suggested seem to be 2A3 variations.
6a5g is the only viable one because it's IDH
but they only handle 250V max and give only 3W.
I don't have the seperate filament windings
so the DHT won't work in my amp.
Here's the schematic for my amp.
My amp weighs about 60 lbs. OUCH
Dan, two things. That 2uf across the output tube's cathode resistor is not big enough.Get a couple of 5 volt filament transformers and try 300bs. They will sound much better because the 300b is much more linear.
My 2 cents.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre'> > That 2uf across the output tube's
> > cathode resistor is not big enough.My speakers have an F3 of ~200Hz.
I have a powered woofer below that.
The 2uFd gives an F3 of ~120Hz.> > Get a couple of 5 volt filament transformers
> > and try 300bs.No room in the inn.
The top of the chassis is filled with:
1 pwr trannie, 4 PS chokes, 2 plate chokes,
2 grid chokes, 2 OPTs and 4 octal tubes.
The underside has 6 motor run caps and
2 edcor variable autotransformer volume controls.> > They will sound much better because
> > the 300b is much more linear.I don't doubt it.
I am thinking of a PP 300B one day.
"My speakers have an F3 of ~200Hz.
I have a powered woofer below that.
The 2uFd gives an F3 of ~120Hz."Sorry, I guess I'm not paying attention. :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
the sovtek 6b4g will work at your 400V/60mA. You'll still need two 6VDC filament supplies. You could use the 6n1p to make up the gain. Just, FYI. Stay with the kt88 if you like it.
Why do you campare the tubes with the same cathode resistor? The KT88 / 6550 gets the highest current in this way. You should use a pot for getting the same bias current! If not, you compare the behavior of the output tranny at different dc currents!
Frank
FrankThe difference in current is minimal.
The KT66 gets about 55mA while
the KT77 gets about 58mA and
the KT88 gets about 62mA.
The OPT is rated at 120m so
none are close to pushing it.
I know of someone who can build like nobodies buisness & has went full circle on DHT amps & settled on strapped 6550, albiet a DHT pre, but still. If your amp has your dream tone then just use it. & I run a 300B PP amp & it is good, but so are many of my other non DHT amps.no clear winner & all very differant.
nt
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