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Old 22nd December 2010, 10:38 PM   #11
rmyauck is offline rmyauck  Canada
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Thanks Kevin for info on JJ's as I have a friend in the US getting a Scott 299(A) redone and he was wondering about tubes. They seem to survive fine in my Eico HF-12 amps using a variac for now to run them just above 110V for normal B+ spec'd for EL84.

Check this very interesting mod from Dave Gillespie!

There is a whole thread on it diytube under in stereo 35 under "improved ST-35 performance". It could help tubes last and sonics on many EL-84 to 7591 amps or other low voltage bias (under -37V) amps for low $.

http://www.tronola.com/A_New_Look_At...riend_Rev0.pdf

I've got to get some of those 3 critters ( LM337 neg voltage reg's) to try in the new year!

Thanks very much Dave for that!

Randy

Last edited by rmyauck; 22nd December 2010 at 10:51 PM.
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Old 23rd December 2010, 02:39 AM   #12
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RCA 6BQ5 for bass.
Mullard EL84 for mids.
Telefunken / Amperex for trebles.
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Old 23rd December 2010, 02:51 AM   #13
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I wrote a long post before I realized that you said EL-84 and not EL-34 so I deleted it. I have not used EL-84s that I know of. All I can say generally about brands is that all the NOS tubes are better but may not be worth the price to you depending on exactly what you want to do. If it is not worth it to you then I think I like the high grade Svetlanas or the new production Mullards the best. I don't know if that would apply to EL-84's though
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Old 23rd December 2010, 03:05 AM   #14
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Quote:
Originally Posted by rmyauck View Post
What are the operating voltages it subjects your outputs tubes to? If you don't know , what's the amp? Many amps need 7189 spec tubes as they are pushing voltages way above EL84 specs.

I've had good luck with JJ's so far and they are well priced. You can get them for $40 a quad. They are known to take some out of spec voltages too and sound really nice. From what I read on this form and others there is an agreement on this.

There are Russian EV etc. rated tubes which can take even more abuse according to many on the forms. You'll probably hear from many users on the these as they can be quite well priced.

New Sensor's Gold Lions are supposed to sound great for close to 3 times the price. May be best sounding of new production. Don't know if they can take out of spec voltages.

Shuguang Treasure Series has a Pavane T series in the upper price range about $95/Pr. just out which should be sonically great too as the other tubes in this series are well liked on the forms. Can they take out of spec V. is another unknown.

My question for the many amps that need 7189 or higher spec why not make tube adapters to plug in your amp which take the new production 7868 or 7591 tubes which are octals and apparently have close to the same drive requirements as the EL84/7189. Space could be a problem on some so they may have to be sky wired. EH ones go for about $80 a quad and should last for many more hours too at the lower voltages. Plus you could have fair bit more power with adjustments! HH Scott amps specified 7189 tubes and in the later seies went to 7591 tubes with larger output transformer. Their amps ranged from 30-40 W/CH. You would loose a bit in power because of the 7.6-8K ohms input load found on most EL84/7189 amps, but may gain in sonics. I don't think it would hurt sonics going from Tung-Sol's 6.6K spec. for fixed bias. Actually the spec. for Cathode Bias which many EL84 amps use is 9K for Pentode hookup of 7591's. The Tung-Sol specs 23-45W depending on setup and voltages. It is said they run nice and cool in the under 400V range too.
See attachment for specs.

Hope that helps!

RandyAttachment 202103
Ditto on the JJ's !
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Old 23rd December 2010, 04:09 AM   #15
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JJ's in my Fisher X-100-3 "7189" sockets. No smoke, no lightning storms, only music.

Not all 7591 behave like EL84. Sovtek 7591xyz is more or less 6L6 with 7591 pinout.
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Old 23rd December 2010, 04:16 AM   #16
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Quote:
Originally Posted by quikie22 View Post
RCA 6BQ5 for bass.
Mullard EL84 for mids.
Telefunken / Amperex for trebles.
I have x-ray photos of my RCA 6BQ5. Surprise, beam tetrode inside!
Definately not the same animal as EL84/7189. I do not know if this
applies to all RCA 6BQ5, or I just found something weird and rare?

I have JJ and GT branded EL84's, also Fisher (Made in England) 7189.
All genuine pentodes, X-rays of these look nothing like the RCA.

Search the forum for X-ray, you will find my thread with those pics.

Last edited by kenpeter; 23rd December 2010 at 04:23 AM.
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Old 23rd December 2010, 06:57 AM   #17
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I believe that E84L / 7230 by Siemens are the best, followed by RCA 6BQ5.
The Russian 6P14's sound very open and dynamic too and it's a good deal due to there low price and availability.
But after all I believe that most important is the topology and the OPT that you will use in your project
The type/maker of the tubes is the last thing you have to deal with.

Last edited by satelitis; 23rd December 2010 at 07:01 AM.
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Old 23rd December 2010, 03:08 PM   #18
20to20 is offline 20to20  United States
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Quote:
Originally Posted by quikie22 View Post
RCA 6BQ5 for bass.
Mullard EL84 for mids.
Telefunken / Amperex for trebles.
By your experience you think these tubes are not linear?
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Old 28th December 2010, 12:41 PM   #19
Trebla is offline Trebla  United Kingdom
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Some sellers quote different figures for matching. Are any of them really meaningful or useful?

Example one.
Mutual Conductance is:
Tube 1 86
Tube 2 86
Tube 3 85
Tube 4 85

Example two.

Ia S
mA mA/V
1 - 6P14P-EV test results 51.0 13.0
2 - 6P14P-EV test results 51.0 13.0


Example three.
Ia Ig2 S -Ig1
mA mA mA/V uA
1 - 6P14P-EV test results 43.0 4.0 11.0 >0.2
2 - 6P14P-EV test results 43.0 4.0 11.2 >0.2
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Old 28th December 2010, 01:42 PM   #20
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Trebla View Post
Some sellers quote different figures for matching. Are any of them really meaningful or useful?
<snip>

Example three.
Ia Ig2 S -Ig1
mA mA mA/V uA
1 - 6P14P-EV test results 43.0 4.0 11.0 >0.2
2 - 6P14P-EV test results 43.0 4.0 11.2 >0.2
Of the three IMHO example 3 is definitely the most useful, and while I would have liked to have known the plate voltage it does indicate that this particular pair is matched to better than a couple of % under conditions reasonably typical of use. The others do indicate that the tubes are tested and match to some degree. All are useful in the sense that they indicate that the seller cares enough about his reputation and the quality of his product to properly test them prior to sale.
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Last edited by kevinkr; 28th December 2010 at 01:44 PM.
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