Best 6550's for the money....

[wboyd]

Hey everyone,

I am getting ready to re-tube my 6550 based amp and was wondering what type I should purchase. I have done a little searching in the forums and on the net, but have not been able to come to any concrete conclusions...so, I thought that I would start my own thread and ask for any and all opinions.

Currently I have a set of Winged-C (new Svetlanas?) and before that I had some original Svet's. I will be needing a matched quad.

Thanks for the input,

Wayne

[Jim McShane]

Originally posted by wboyd
Hey everyone,

I am getting ready to re-tube my 6550 based amp and was wondering what type I should purchase. I have done a little searching in the forums and on the net, but have not been able to come to any concrete conclusions...so, I thought that I would start my own thread and ask for any and all opinions.

Currently I have a set of Winged-C (new Svetlanas?) and before that I had some original Svet's. I will be needing a matched quad.

Thanks for the input,

Wayne

Wayne, the problem is there ARE no concrete conclusions! Each tube has it's own character, and it's a matter of fitting them together with the rest of your system and your preferences.

Tell me what you like and/or don't like about the SEDs. Are you looking to change the tone of the system? What's your budget? Would you consider KT-88s instead?

Sorry for the "grilling", but since there is no concensus it's a matter of understanding what YOU want!

I'll watch for your reply and try to help if I can.

[richwalters]

At current time Svet produces excellent 6550C's and no need to look further......althought I am informed the coke bottle Tungsol version can take a higher B+; i.e closer to the golden oldie A version. I don't know if this is true. Other DIY members could input....reliability etc
I'm currently using Svet 88's with a duration clock sofar accumulated 500hrs at 50mA @ 500V and all are emission stable. (a well made KT88 used under such AB conditions should last 10,000hrs min).
If longevity is your goal then a larger anode/ cathode area can do the trick.. BUT...The 88 is 60% dearer than a 6550C. Does your circuit really warrant it although it will probably give the same power out ??
However, my 30W guitar amp has orig KenRad 807's.. these have accumulated over 30,000hrs solid service from 1972. Quo Vadis ??

richj

[wboyd]

Jim,

No....I expected the grilling...my request was rather vague to say the least.

Now onto the meat of the matter - I listen to many types of music but moreso Jazz/blues than anything else. I wish that I had the luxury of rolling several different types of tubes in my system (it takes a quad and that could get expensive with 6550/KT88's).

I am going to try and keep my budget right around $250 or so (if I have to go more, I might...depending on recommendations), and I am open to suggestion as far as KT88's are concerned. But take into account that I do need a quad...

Here is quick system overview;
Phillips SACD 963SA
Audio Alchemy DAC (DDE 1.1)
Passive Preamp using Alps Black Beauty and Grayhill selector (soon to be a Grounded Grid as soon as the project is complete)
Power conditioning in a John Risch design installed in an old UPS housing
Power Amp is a Goldox (using 4 6550's)
System interconnects are primarily silver w/teflon coating terminated with Vampire/Rat Shack rca's
Speaker cables are braided CAT5

Speaker systems used:
Fostex BLH 103E (built based on Fostex plans)
System 2 is a full 3 way horn based system controlled with a Bheringer DCX 24/96 full computer interface modified with 6 way volume control
Subs are Lab 12 (driven by main amp - Goldox)
Mids are Electro Voice 75hz horns (driven by gainclone 1)
Highs are BEC compression drivers (driven by gainclone 2)

There ya go....

Have a good one,

Wayne

[Jim McShane]

Wayne,

All that good information is interesting - but the keys to making a choice (now that you've set doen a budget limit are still:

1. What you like and/or don't like about the SEDs?

2. Are you looking to change the tone of the system?

3. Would you consider KT-88s instead?

Rich Walters' post, for example, gives me a lot of clues about what he likes. The SED (Svetlana) KT-88 is a very "tubey" tube. It has a rolled off top end, and it tends to have rather muddy bass. Now Rich may either be using that tone to balance out other parts of his system - or he may prefer that tone.

The 6550C SED is a much better tube in my opinion, and Rich said he likes it. It has better tighter bass, and a much better top end than the SED KT-88.

But in either case I know he would find the EH KT-88 (as an example) to be too "hot" on the top end for him. If his budget allowed he might like the GE 6550A though.

That's the sort of information that can help us here help you. Give it one more try if you would.

[richwalters]

Should have digressed a bit further... I’m using Svet winged C KT88‘s....(black markings)...I find these tubes are to blame for the softness in the top end...bit too smooth but to blame it all on the tubes ? Things begin to get complicated and contradictorary. The 10Khz square wave and response check on my UL parallel-p-p hi-end amp doesn’t give many clues that anything is amiss....with roughly 15dB nfb at 40Khz, thd is well down. The amp frequency power response –3dB @ 45Khz. (The b/w of the front end 7199# ECL82 driver stage is alone above 200KHz). Wideband thd is around 0.1% at 150W rising abit in the low end.
In some ways running the output tubes harder towards class A does make a slight quality change but so does the AC power requirements.
As a engineer, the top end difference made me relook at the C/R HF phase comps value in the 1st stage anode and also global nfb compensation... but since square wave looked good I left them alone. If anything my Peerless top ends and midranges are also softish....even though my top ends are bit more sensitive than mids....shrill sounding music gets tiring with long term listening. Such is the sound variation quality between satellite and even CD’s and the relationship of loudspeaker load with the plate leaves one puzzled what to do next. What do we consider the best reference music to judge system quality ??
My reference favourite music is the best Austrian brass band. (Of course I live in the Alps) This will make larger LS systems really hit the low end bass drum ...even though big band or Jazz is not everyones taste....so be said alot of modern day rubbish.
I still use 6dB/oct LS crossovers ..12/18dB Crossovers leave alot to be desired and many tube amps object to complex loads.....in the 6dB case any phase errors created by speaker overlap can be corrected by careful placement.

My suspicions lay in the Peerless top-ends.....I might change these.
As to the low-end discussion....this can come another day.

My next amp in build is a modest 30+30W...on the same quality lines of my massive 150+150W...since I have alot of 6550B’s these should nicely fit the bill.


richj

[cerrem]

I will say hands down that the JJ KT88 tubes are the best new production of the 6550/KT88 class of tubes....
This is for Hi-End Audio applications......
This are the most linear, clear sounding without the colorization I have found...

Best Regards
Chris

[SY]

My reference favourite music is the best Austrian brass band.

Who is that? I loved the brass bands I heard in Vienna.



Chris, thanks, I was just looking at them last night and wondering... I've been very, very pleased with their EL84, but Jim raised some alarm bells about other products of theirs.

[richwalters]

Originally posted by cerrem
I will say hands down that the JJ KT88 tubes are the best new production of the 6550/KT88 class of tubes....
This is for Hi-End Audio applications......
This are the most linear, clear sounding without the colorization I have found...

Best Regards
Chris

Troubles ?? My JJ's despite being matched give higher THD and require 20% lower grid bias settings than for other 88's. I agree they are "harder tubes" and can take considerable abuse and overdrive.
On my bench I would hesitate swapping them in a chassis specifically with "standard non clone 88's". I rate JJ's between a KT90 and and NOS GEC 88. The KT90 despite having a wacker sized anode isn't really optimised in UL circuits and produces far higher harmonics, as expected for a scooped up sweep tube. For <MI who cares ??
richj

[wboyd]

Jim,

Ok, to answer your questions....here are my "best" answers (coming from a layman that has only been into tubes for about a year and half or so).

1. What you like and/or don't like about the SEDs?

Seem a little "muddy" and sometimes shy on the bass side, otherwise everything else is pretty good.

2. Are you looking to change the tone of the system?

Maybe this is a little too much to ask, but I am looking for very liquid midrange, dymanic treble and sharp bass (very "deep" bass is not required). So yes...I am looking to change the tone a little. I really like to "hear" the music. Love to hear nice brass, acoustic guitar, brushes on cymbals, etc.

3. Would you consider KT-88s instead?

I would...I would love to get a good description of the sounds produced by the KT-88s. What would you compare them to? will I need to change the bias on my amp?

My only other tube experience is with set of EL84 Monoblocks that I have been rebuilding. These little 8 watt, single-ended wonders seem like they will be wonderful when finished.

That's all I have time for now....very busy today....but I will be checking in from time to time.

Everyone have a good one,

Wayne