Replacing tubes in LK48

[edster00]

So where has this question been posted? Please post the URL so we will all be able to read the responses

[NOSValves]

Edster,

Its a list server the responses are above that a recieved long ago so I really don't see the point but whatever it can be join at the HH Scott web site. You can't read what I posted above and see that its stated that a 6U8 is in fact the best replacement for the 6BL8 which in fact never ever came in the 222C he keeps talking about the 222C only used a 6GHB/6U8 or a 7199. I have went thru this same type of twisted posting with this person on the list server many times in fact the last time I kept pushing my point that he twists fact to his liking until he blew up and started foul language and they threatened to ban us both !! Watch as I cause him to do the same as he twist his snaky ways !! He can spout his fancy specs all he wants but the Ears tell the truth !!

Craig

[edster00]

I asked where the question was posted because, in the interest of fairness and accuracy, it is relevant to see the actual wording of the question(s) and the actual wording of the response(s). I wouldn't be qualified to evaluate the validity of the response(s) because of my lack of knowledge on the subject, but others here on the BB may be interested in the debate.

[Deang]

Sounds to me this has already been asked at the other forum and resolved. Let's review.

"Okay I need some serious clarity on all the different phase splitter tubes and which is the best to use in these amps? Is there a Sonic difference ? I now have 3 different Amps and they all spec for a different tube. 222C specs 6U8 , 299A specs 6BL8 and now LK-72 specs 6GH8. So are all these tubes interchangeable ?? Which tube is the best for the job ?? I know that everyone likes the Jan 6U8's that are available and really cheap these day's. But is it the best choice or more vintage offering's a better way to go??"

The question is clear enough to me, and so are the answers.

"It is quite simple, Craig. The 6U8 and the 6GH8 tubes are identical in design and purpose to each other. On the other hand the 6BL8 tubes are different, they are a lighter duty (lower voltage ratings) tube and can be replaced by the 6U8/6GH8 tube (which is a far better tube for your set. The 6BL8 tubes and the 6U8/6GH8 tubes all have the same pin out). You can't replace a 6U8 with a 6BL8 tube, but you can replace a 6BL8 tube with a 6U8/6GH8 tube. This is the only way it can work. Personally, I do think that the JAN Philips 6U8A tubes work really nice. For the buck, buy these....really quiet!!!"

The differences are quite notable, but the 6U8 has much higher voltage ratings at the plates and the screen of the triode. This tube can be used as a substitute for the 6BL8. The 6BL8 can NOT be used to be as a plug-in substitute for the 6U8 without mods to your set. Use a 6U8 tube. It is a one-way street here...

Yet you say to Craig, "Not once did anyone mention substituting the 6U8 tube for the 6BL8 tube in a 299."

Gee, you're right...not once, but three or four times.

It is apparent this situation is similiar to the 6DJ8 and 6922/7308. You can use the 6922 or 7308 in place of the 6DJ8, but you can't use the 6DJ8 when the 6922 is specified.

At this point -- the score is Nosvalves 2, "Expert" Zero.

[NOSValves]

Dean,

I love you man !!

But I may even have a better one for you !!!!!! Here is Ryan reply to the exact same question on the list server I had saved it in my tube info folder in Outlook !! This is Hilarious I knew the H H Scott Expert would dig himself a hole I just never knew it would be this easy !!!

Hi Craig,

I saw your posting on the listserv regarding phase splitters. For replacing

6GH8's , I always use the JAN Phillips 6U8A tubes. I recently purchased an

LK-72 that still had the original Scott 6GH8 tubes in it. Basically, the 6U8A

is just a heavy duty version of the regular "consumer grade" 6GH8. I've found

that the 6U8A tube will last longer, and sound better in Scott amps that

require a 6GH8. I'm sure by now that you have noticed the phase splitter

variations used in Scott amps. I've owned 3 LK-72's in the past, and I've

noticed some strange variations. One of them used 7199's, and was fixed bias

(not a bias pot to be found), it also did not have DC Balance pots. The next

LK-72 had bias and balance pots, along with 6GH8 phase splitters. The 3RD

LK-72 had DC balance pots, but no bias pots, and used 6U8 phase splitters.

Many Scott amplifiers have 6U8 or 6GH8 printed next to the phase splitter

sockets. Basically, all of these tubes are identical, except for very slight

bias variations and the different pinout of the 7199. The 7199 was designed

to be used exclusively in audio, but it actually sounds no better than the

6GH8 or 6U8. If you're looking for the best, try to find NOS Telefunken

6U8's. They are the sweetest phase splitter tubes ever made.(wasn't this tube a waste of money a few seconds ago has anything changed with NOS tubes in the last year)you stated that

your new amps filter (can) capacitors are still good, so are mine. In fact,

every Scott amp I own has the original B+ electrolytic can capacitors. Scott

sure did use high quality filter caps, most of them were manufactured by

Mallory. Why would anyone want to replace good filter can capacitors? You

would have to be crazy to spend $30 a piece on custom made can capacitors

unless they actually tested bad. By the way, those Sylvania 7591's were built

to last, they don't have to be perfectly matched to sound good. Find 2 that

are closely matched, and use the matched ones in each channel. I read on the

Klipsch forum about you installing 64 uF filter caps in your 222-C. I bet

your amp doesn't hum at all now! This would also increase the bass response

slightly. Just don't tell the guys on the Scott forum about this, as they

hate modifications!(he slammed anyone openly about modding amp just a few weeks back on the Scott list server trying to discredit me also said Klipsch Khorn were horrible) According to the RCA tube manual, the maximum input

capacitance for a 5AR4 rectifier tube is 40 uF. I don't really believe this,

so I installed a 80 uF capacitor in the first filtering stage (right after

the 5AR4) in my 222-D.(he argued against this mod openly with me and another member of the list server again trying ot discredit me) If you use an RC network (resistor-capacitor), you

have nothing to worry about, especially if your using a Mullard 5AR4.

However, I wouldn't recommend using the new production Sovtek 5AR4, as its

tiny plate structure would probably melt into a red hot, molten blob! You can

use the same bias modification for this amp as you did for your 222-C. Use

pots rated at 50K Ohm, 1/2 Watt and use 10 Ohm, 2 Watt resistors. You could

even use four pots, and this would allow you to use unmatched tubes (which is

a plus), and set the bias for each tube. (here he tells me how to do the mod that I shared with the Scott forum and the list server designed by no other than are beloved Mark Deneen)

BTW: DON"T use 6BL8's except for in a 299 or 299B. Using them in any other

Scott amplifier will apply excessive B+ voltage to their plates, causing

premature failure.

Stick with 6U8's! (but I believe this says it all )

Regards,

Ryan

[Deang]

Are we SURE this is the same guy?

[NOSValves]

Oh one and the same !! It took me a while to catch his variations but he is the one the same !! How could there be more than one like this ?? He changes his tune like the wind depending on who he is talking to and what he is trying to accomplish in this case he thinks he can horn in on my little thing going on here or he is just jealous. He hates horn speakers so why would he be here ??

Craig

[NOSValves]

Edster,

The point I'm trying to make here is that H. H. Scott Experts advise should not be taken seriously because it changes like the wind. He may very well be technically correct about the spec differences of these tubes. But as we all know specs are not and never will be everything the Ears tell the best story ! This guy can not be trusted and I'm just making my fellow forum members aware before its to late !!

Craig

[Deang]

Oh, I'm sure he's probably dead on with his tube specs, but it's not really a question of what the ears hear so much as it what these specs mean in the end. I'm no Scott "expert", but it seems to me the only thing it means in the end is that if you use an over spec'd tube -- it's just going to last 3 times longer. Besides, if the tubes weren't interchangeable in this particular application -- it would be a well know fact, and not even open to debate.

I wouldn't let this bother you, just blow it off.

[NOSValves]

Dean,

Your absolutley correct 6BL8 burns up awful fast and is one of the reasons I suggest a 6U8 in all these amps. I have used and own many 6BL8's and have tried litterally every NOS brand you could name and I always return to my Telefunken 6U8 in my 299B and in the 299A you bought which you loved. It had a Jan Phillips 6U8 when you listened to it. Your 299B amp now has a Telefunken 6BL8 in it. I had my 299B with a Telefunken 6U8 side by side with yours and scoped both are amps and did extensive listening to them both and never heard or saw on the scope the least bit of difference. Are amps sounded Identical to each other.

Craig

[Deang]

Our "one year newbie" actually started as a young pup learning most of the basics with his Dad doing ham radio, and he's been mentored by our resident heavy hitter. He's hardly the rookie you are trying to make him out to be.

Something in my gut tells me that using these two different tubes as phase splitters isn't the same as swapping 12AU7's and 12AX7's around, which are typically used for completely different applications.

http://www.qsl.net/wd4nka/TOOLS/Manual/6bl8.html

You also failed to address your lengthy email to Craig, where you clearly give advise contrary which you are stating here. An "expert" doesn't make these contraditions.

Though I'm impressed with your credentials and experience, it doesn't hold up much against Craig's integrity and values in how he has conducted business with people here. I've received two 299's from him, a 299A, and my current 299B. Both are killer, and dead quiet. If there was anything off the wall going on with these units -- you can bet a horn would find it.

[T2K]

I recently rescued a pair of speakers from the trash heap. I went to a site asking questions so that I might refurbish the old speakers. I did mention Klipsch speakers at one point and, rather than help with my original question, a few of the members there decided they needed to bash Klipsch speakers.

The fact that they bad-mouthed Klipsch speakers did not bother me so much as did the fact that they offered absolutely no help with my question regarding a speaker that those people hold in such high regard. I was banned from the site because of their stirring of $hit. Only after I was banned did I begin to get some information, and requests for the speakers.

What I am getting at is that it certainly is nice receiving good information from anyone when you really need it. I have enjoyed the useful information found in this thread, with the exception of the head butting. Can't we be civil here?

I personally welcome Ryan to this forum and hope that knowledgeable others join in too. We all appreciate Craig's past and future help with our Scott equipment. I would not want anyone to come here feeling like they are not part of some 'click', as I was made to feel elsewhere.

BTW, after all was said and done with the 'other' speaker issue, the person that offered more help to me than I found elsewhere can be found at this site, none other than our own DeanG. Thanks Dean.

Keith

[NOSValves]

Ryan,

I knew you would resort to cussing and swearing and blatant lies its your nature thanks for the confirmation of said nature.

Unlike you who is truly just a Electrician claiming to be a engineer. I am a tinkerer and learn by doing !! I don't try to pass myself off as anything else. If I was a true Electrical Engineer I sure as heck wouldn't be wiring houses or whatever it is you do.

Mark,

I have run these tests on the scope and his advise just doesn't hold water . I have pushed my amp and many others to near max output with a 6U8 without any obvious distortion on the scope or to the ears. If it is indeed the case its not measurable with my scope which is a pretty sensitive scope as you know.

Craig

[T2K]

OK, I have a question. I have (2) Scott 222-C integrated amps. On the bottom plate of one the sticker shows 6U8 phase inverter and the other shows 6U8/6GH8. Any difference? Is one preferable over the other? I have several NOS Sylvania 6U8A tubes. OK to use? Other brand/tube offer improvement over the Sylvania 6U8A?

I would also appreciate hearing from those that have actually listened to both Mullard and Telefunken 12AX7's. Can you describe the difference in their sound?

I also read somewhere that there was no difference in the plate voltage capabilities of old NOS 6BQ5's and 7189's. I'm using 1969 vintage RCA 6BQ5/EL84 outputs. Any problems? Any comments?

Thanks!

Keith

[NOSValves]

Kieth,

Your more than welcome to greet Ryan with open arms but I call them like I see them and feel it is my duty to my friends here to bring out the true nature of the beast which is easy to prove. He is here for one reason and one reason only to try to horn in on the business I worked hard at developing and have spent many hours helping others here for. Ryan and myself got along absolutely fine until I put up my web site and ever since he has contradicted and twisted his statements and advise to me and other trying to undermine me mostly on the Scott forum. I find his forum name offensive and more than enough proof of his intentions. This is a Klipsch speaker forum and he hates klipsch speakers so why is he here ?? Trolling !!

Craig

[NOSValves]

Here's another instance of bad advise coming from the "HH Scott Expert" go ahead and run your 6BQ5 tubes on the premise that RCA and the entire vintage tube manufacturers of the late 50's were plotting to ripp the public off and remarked 6BQ5's to 7189's to get more money for them !! I guess HH Scott, Fisher was in on this also since they quit using 6BQ5's and started upping the voltage on the output tubes for the fake 7189s that came out in the late 50's.

Some more Hog wash based on Opinion rather than fact !

Its okay to run a 6BQ5 out of spec but not a 6U8 ???

[Deang]

Your welcome keith!

Ryan, I can see reading the email that your are primarily dealing with the 6U8A and 6GH8, and that the 6BL8 is not mentioned until the last comment in the message ("BTW: DON"T use 6BL8's except for in a 299 or 299B. Using them in any other Scott amplifier will apply excessive B+ voltage to their plates, causing premature failure. Stick with 6U8's!"). It is true that you probably meant just not to use the 6BL8's in the later Scotts and always "stick" with the 6U8's with these -- but it's really not 100% clear.

Another note of interest here is how you use the 6U8 and 6U8A interchangeably. In most of the discussion, you have referred to the 6U8, yet in the mail comments you said, "For replacing 6GH8's , I always use the JAN Phillips 6U8A tubes. I recently purchased an LK-72 that still had the original Scott 6GH8 tubes in it. Basically, the 6U8A is just a heavy duty version of the regular "consumer grade" 6GH8."

A note in the tube catalog regarding the 6U8 says, "Miniature tube type used as combined oscillator and mixer tube in color and black-and-white television receivers utilizing an intermediate frequency in the order of 40 MHz. There were some slight parametric differences between this and the 6U8A, therefore this tube has been listed separately, however similar."

The same note can be found at the end section of the 6U8A relating to the 6U8 -- and neither tube is listed as a replacement for the other in the catalog. However, this is not the case with the 6BL8, as the 6U8 IS listed as a replacement for the 6BL8 -- but not the 6U8A. Under the section for the 6U8A, the 6GH8 is listed as a replacement for the 6U8A, but the 6U8 and 6BL8 is not. Yet in spite of this, the Scott site shows the 6GH8 as a replacement for the 6U8, when in truth, the 6GH8 should only be replaced with the 6U8A.

I think there is some real phase, I mean, hair splitting going on.

[JCturboT]

Craig,

Not quite sure what is going on between HH Scott Expert and yourself but I have nothing but respect for both of you.

You have helped me out in the resto of my former LK-48 and even offered your help in getting it fixed after the UPS shipping incident as well as sending me that repair estimate which was key in getting UPS to cover the damage-all at no cost to you,for this I am thankful.

Ryan has also helped me in the lookout for that exclusive LK-150 and I have exchanced several e-mail with him as well as discussed several other options.He knows I have Klipsch and has never said anything negative about them.

I am grateful to both of you for your knowledge and time spent answering my annoying questions.

It is great in not only having one but two knowlegable HH Scott gurus to turn to should questions arise.

Thanks Guys,

Jeff

[Deang]

You missed the import of my post.

According to published tube data:

1) A 6BL8 can be replaced with a 6U8

2) A 6U8 cannot be replaced with a 6BL8

3) A 6U8 cannot be replaced with a 6U8A

4) A 6U8A cannot be replaced with a 6U8

5) A 6GH8 can be replaced with a 6U8A

6) A 6U8A can be replaced with a 6GH8

7) A 6U8 cannot be replaced with a 6GH8

8) A 6GH8 cannot be replaced with a 6U8

The Scott site lists the 6GH8/6U8A as replacements for the 6U8, a 'no-no' according the published data. They are not "identical", if they were -- the published data would support it by listing all of these tubes as interchangeable.

You said, "...I have a GE box here that lists 6U8A as the main number, under it, are the following numbers: 6GH8, 6KD8, and 6LM8. GE thought that the 6U8 was a good substitute for all three of these tubes, but notice what number isn't included, 6BL8."

Also notice what other number isn't included on your GE box, yep, you guessed it -- the 6U8. How can you say GE thought the 6U8 was a good substitute for the 6U8A/6GH8 when it's not even listed on the box? Also, why should we expect to see the 6BL8 on the box anyways -- we already established a 6BL8 cannot be used in place of the 6U8, 6U8A, or 6GH8 -- no one is disputing this.

On to the 7189/EL-84.

EL-84's were not just relabeled as 7189's. 7189's were the cream of the EL-84 crop. Individual EL-84's were tested, and those that tested out and could handle the 400v, were labeled as 7189's. None of these were "re-labeled". The EL-84 is rated to 300v max.

So yeah, go ahead and run EL-84's in place of the 7189's -- keeping in mind that the majority of superior EL-84's were already yanked and set aside as 7189's. So then, a pretty good chance of landing vintage EL-84's that will be less than pleased running at the higher voltage, and possessing insufficient plate dissipation.

[NOSValves]

Ryan,

conspricy theory your no expert either . Ryan where were you in the 60's ??? Its doesn't matter how long I have been at this you are wrong and that is the point. Show me some real documentation not based on Opinion any where that say's a 6U8 will distort in place of a 6BL8 in fact VTV recommends the 7687 in these amps is it the wrong tube and distorts the sound also ??

Craig