Which set of 6550´ for my classic 400?

prengel_basser · #1 12-02-2010, 04:25 AM

hi there!
I just bought my second Peavey classic 400 head and these guys need an oktett of 6550´/kt88. I really want to retube it, since the stock "coke bottle china tubes" are really crappy!
In my second classic 400 head, I´ve installed 8x Sed =C= Kt88.
I´m pretty happy with these but I would like to try something different and something cheaper on the other head.

I would like a tube that:
- puts out the full power
- is reliable
- has a growly mid charakter (I dont like scooped bass sound´s)

I guess we could talk about following tubes:
- Sovtek 6550we
- Sovtek Kt88
- Electro Harmonix 6550
- Electro harmonix kt88
- Tung-Sol 6550
- Shuguang kt100
and SED =C= 6550 (but this one is still expensive)

so which tube should I pick, and why?

best regards!

stefan

derridiandrift · #2 12-02-2010, 04:59 AM

Those chinese coke bottles are awful in that they're not reliable and they sound like crap. Buy a set of Winged C tubes and be done with it. They sound great and they have consistent quality. You'll get decades of use out of them.

username1 · #3 12-02-2010, 06:56 AM

The sovtek 6550we has the mid growl your looking for with lots of power and good reliability. It is also one of the lowest price 6550's. The EH will sound more scooped.

jastacey · #4 12-02-2010, 07:30 AM

Several people have said that the Shuguang kt100, is a good sounding tube, my experience has been with the Sovtek 6550WE & the Winged "C" 6550's

prengel_basser · #5 12-02-2010, 07:43 AM

@jastacey

how did you like the sovtek 6550we compared to the SED =C= 6550?

jastacey · #6 12-02-2010, 08:04 AM

In my Basman 300, the differance is:
the Sovteks get growly, when pushed some what
the Winged "C" has a strong punch in the high low mid-range, it's kinda of a sound that's somewhat noticeable, but the Winged "C" stays cleaner when pushed to the same level as the Sovtek ... they are both good tubes, or I should say, I've had good luck with these tubes ... my advice is to buy the tubes from a respectable retailer ....

NecroticImbecil · #7 12-02-2010, 10:55 AM

I don't know if he is still active here, but TB member James Hart documented his choice for power tubes when he had one of these. A search for his name and the amp may turn something up.

Thornton Davis · #8 12-02-2010, 11:57 AM

I think that I was one of the very first to tube my Classic 400 with Sovtek 6550WE's about 10 years ago. They were excellent and I never had any problems with them. I can't say about the same about the factory supplied Chinese Coke bottle tubes.

I sold that amp only because of its 93 lb weight.

TD

BbbyBld · #9 12-02-2010, 01:09 PM

OP, Shuguang is who manufactured the stock tubes. I think some of the tubes you listed are basically the same tube under different names and/or rearrangements of the guts and glass (Sovtek/EH/"Tung Sol"). Winged "C" tubes are good, if you get the good ones, but they are anything but consistent in my experience. Some companies sell selected Winged C, so I'd choose them before just buying Winged C on the open market. I believe Ruby is one company who sells tested ones.

The bigger problem that I harp on all the time is the output transformer impedance matching. The C400 transformer was designed to match the stock tubes, which were Chinese approximations of 6550s. If you use the stock tubes, you will get up to 450 watts out. When you swap them out, you WILL get less output power, but how much less depends on what tubes you use. If memory serves, with a "real" 6550, the output transformer expects to see a 12 ohm load on the 8 ohm setting. The thing is, all the tubes out there that are said to be 6550s/KT88s are vastly different, so I don't think anyone knows what a "real" 6550 is any more (or for the past 30 years for that matter). This is one reason why I don't design with them. They are grossly inconsistent no matter who you get them from.

Many members like the Sovteks, but they are the worst match with the output transformer of any other 6550/KT88 I've tried. This means with the Sovteks you only get about 250 watts, and up to 300 if you have a good set (I've tried 2 or 3 sets). The amp also does not seem stable running these judging by the clipped response.

The JJ KT88 is the most consistent tube of this variety out there today, and luckily, it's the best match for the output transformer so you can actually get close to the full 400 watts out of the amp. My office C400 has a set of these and does 380 watts. This is the tube we selected for use in our service department

okcrum · #10 12-02-2010, 01:19 PM

Great info, Bobby! I have also had good luck with Svetlana/SED, before they were sold. I might be finding out soon how they are now. GC has quads of Svetlana 6550s for $106.

Thornton Davis · #11 12-02-2010, 01:35 PM

Quote:

Originally Posted by BbbyBld

Many members like the Sovteks, but they are the worst match with the output transformer of any other 6550/KT88 I've tried. This means with the Sovteks you only get about 250 watts, and up to 300 if you have a good set (I've tried 2 or 3 sets).

FWIW, I found the completely opposite when I installed my Sovtek 6550WE's and biased the amp. My meter showed my Classic 400 was outputing 443 watts RMS and I had the tubes running cool.

TD

twinfallsbass · #12 12-02-2010, 01:47 PM

The JJ KT88 is what used per BbbyBld's recommendation. Had NO issues up to the point where I sold the amp. Listen to the designer, he knows his stuff!!

BbbyBld · #13 12-02-2010, 03:28 PM

I have not tested these yet, but JJ just sent some of their newly designed 6550s. It looks quality, and I suspect it will be as good as their other tubes. This may be one to add to the list.

prengel_basser · #14 12-02-2010, 05:17 PM

@ BbbyBld
just for my understanding: you are an amp engineer and work at peavey?
and you own a classic 400, did i got everything right? :-)

the thing is: I have no technical knowledge about tubes, so i have no idea what the differences of "today" and "past" 6550 are. do you actually like the stock "cokebottle" tubes? there were some classic400 with another chinese powertube, which looked like this: http://media.photobucket.com/image/p...0/IMG_1655.jpg

i´ve herad that they sound o.k.

but I have these:
http://media.photobucket.com/image/p...h_IMG_1657.jpg

about the JJ: Many of the german users say that they have a VERY strong bass response and tend to sound boomy. There has to be a tube that gets the full power out of this beast!

fishman35 · #15 12-03-2010, 06:07 AM

I try to stick to Russian tubes. During the cold war where the US was going transitor, the Soviet Union was still primarily tube, and they are really good at it. I always use Sovtek, or Electro-Harmonix, (which is the same company as Sovtek), in my Ampeg 1981 SVT and my 78 Bassman head. I have used Svetlana as well. Stay away from Chinese tubes, IMHO.

I just got my Fender Bassman 300 and it came with stock Groove Tubes. Those will be gone soon enough.

Tubedepot.com in Memphis is very reputable.

NKBassman · #16 12-03-2010, 06:52 AM

I just ordered a set of Winged C's for my SVT-2 PRO. I've heard good things...

tombowlus · #17 12-03-2010, 07:40 AM

Thanks for chiming in, Bobby! That was really helpful!

Have you had any experience with Valve Art KT88's? That's what I have in my Classic 400, and I really like the tone (but have not measured output).

BbbyBld · #18 12-03-2010, 09:20 AM

Quote:

do you actually like the stock "cokebottle" tubes? there were some classic400 with another chinese powertube, which looked like this:

I like them ok. The main thing I can hear in a power tube that bothers me is a "thin" or weak sound. Those don't sound like that. People talk all the time about how this tube and that tube sounds...tubes vary A LOT. There is a lot of "eye listening" that happens when people swap tubes. The instance of finding a tube that REALLY sounds noticeably different is rare. Because of that, if your tubes work and you like them okay and your amp is not malfunctioning, DON'T swap them!

Both this tube and the coke bottle tube came from the same factory and have a lot of internal similarities. The one in the picture did have a fatal flaw that plagued some of the RCA power tubes of the past--the getter on the side of the glass reflects heat back on the plates which causes inefficient operation/failures. One tip that every tube fan should know...never buy power tubes with getters (the silver crap coating the glass) on the side of the glass!

Quote:

about the JJ: Many of the german users say that they have a VERY strong bass response and tend to sound boomy. There has to be a tube that gets the full power out of this beast!

That's subjective. I've run response curves on the amp with several different types of tubes and there was virtually no difference. With the low EQ, low cut switch, and the resonance control, that should be the easiest thing in the world to adjust out (if it's true). 6550/KT88s are expensive and are even more so if you buy a bad set that burns out in a week. I'm trying to suggest a tube that will last for years and one that I know will work great in the amp.

Quote:

Have you had any experience with Valve Art KT88's? That's what I have in my Classic 400, and I really like the tone (but have not measured output).

I've never tried them. The only Valve Art tubes I've had my hands on were EL34s. If I'm remembering right they appeared to be Chinese tubes that were re-branded (Same as Ruby EL34BSTR). I'm not knocking them. Chinese tubes get a lot of bad press, which is unfair because there are some sweet Chinese tubes out there that get overlooked all the time. I've been under the impression that all the Valve Art tubes were selected re-brands. Can you tell anything about the origin of yours?

tombowlus · #19 12-03-2010, 09:26 AM

Quote:

Originally Posted by BbbyBld

I've never tried them. The only Valve Art tubes I've had my hands on were EL34s. If I'm remembering right they appeared to be Chinese tubes that were re-branded (Same as Ruby EL34BSTR). I'm not knocking them. Chinese tubes get a lot of bad press, which is unfair because there are some sweet Chinese tubes out there that get overlooked all the time. I've been under the impression that all the Valve Art tubes were selected re-brands. Can you tell anything about the origin of yours?

These are definitely of Chinese origin (built by Shuguang). Doug Preston recommended them, and they sound great to me (and have very low noise).

prengel_basser · #20 12-03-2010, 12:12 PM

I really have to listen to the stock tubes when the head arrives.
having two of these is quite nice, because I can compare the tone of the stock tubes with the new SED =C= KT88 in my other Classic 400.
@ BbbyBld: I will keep your advise with the JJ´s in mind! thanks for that.

I have read many different comments how to bias the amp correctly. will it change the output power if I run the tubes colder or hotter??? some members biased the amp differently to the standard -52v.

here is a quote I have copied from a TB member about the bias:

"I have since found out that measuring bias voltage is basically useless.

The Peavey Official bias procedure calls for setting bias voltage between -52.5 and -53.5 v DC.

When I was biasing my amp, I connected 2 multimeters and compared bias voltage and bias current.

The plate voltage of MY amp is 663 V DC. According to the schematic it should be 675v. Anyhow, based on a targeted 70% dissipation for a class AB amp and an anticipated 35 watts per 6550 output tube, you divide the power output by the plate voltage to get MAX dissipation. So we're at 35/663 = 52.8 milliamps. Multiply that by .7 for safe Class AB operation and we get a recommended plate current of 36.9ma.

Biased at that current, the bias voltage is around 46.5, WAAAY lower than the Peavey recommended -53v.

Conversely, at a bias voltage of -53 v., I get a bias current of ~18ma--VERY cold.

So...if you want to get the most out of this amp (and really, why would you be hauling a 100 Lb. amp unless you were going for a "no-compromise" tone) you need to bias to the power tube current."