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littlejackhorner

Scott 299-C - EL84 for the power tubes vs 7591

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Hi all,

 

I have a Scott 299-c for a number of years now, and have it happily paired with La Scala's.

 

I recently considered rolling tubes - I noticed its 4 power tubes which normally call for 7591's

actually have Ei Yugoslavia EL84's.

 

Does anyone have experience with using the EL84's in this config, and what are the pluses and minuses

for not using the called-for 7591's ?

 

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Those tubes are totally different.  I don't recall seeing the “C” version with EL84s in the output stage.  Are you sure you don’t have an earlier model?

 

 

Maynard

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Those tubes are totally different.  I don't recall seeing the “C” version with EL84s in the output stage.  Are you sure you don’t have an earlier model?
 
 
Maynard


Oh - you are right! It’s a 299-B and I never knew. That being said the power tubes in the B should be 7189.

It sounds good to me and other than one blinking light it performs flawlessly.

I did google search for this type of substitution and found nothing.


Sent from my iPhone using Tapatalk

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42 minutes ago, littlejackhorner said:

 


Oh - you are right! It’s a 299-B and I never knew. That being said the power tubes in the B should be 7189.

It sounds good to me and other than one blinking light it performs flawlessly.

I did google search for this type of substitution and found nothing.


Sent from my iPhone using Tapatalk

 

What substitution did you google?  7189 is the correct output tube for a Scott 299B.  You might want to read about Russian surplus 6P14P-EV .  (6П14П-ЕВ)    EL84 might be OK.  Google these tubes - you'll find lots to read.

 

7591 is NOT the correct tube for a 299B.   (7591 is a completely different tube.  It is used in the 299C.)

 

Here's a good reference site:   http://hhscott.com/integrated_amps_stereo.htm

 

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9 hours ago, robert_kc said:

What substitution did you google?  7189 is the correct output tube for a Scott 299B.  You might want to read about Russian surplus 6P14P-EV .  (6П14П-ЕВ)    EL84 might be OK.  Google these tubes - you'll find lots to read.

 

7591 is NOT the correct tube for a 299B.   (7591 is a completely different tube.  It is used in the 299C.)

 

Here's a good reference site:  http://hhscott.com/integrated_amps_stereo.htm

 

Thanks again, Robert! - again, you are right - I had been googling 7591 and EL84 all along and that's why I hadn't found any useful results.

 

 I just googled the correct pair and they are indeed possibly interchangeable, the big difference being the operating voltage of the circuit. The Scott 299-B appears (anecdotally?) to operate at 355 volts which is higher than the EL84 rating, but not quite at the 400V rating of the 7189. That was probably a measured voltage and not necessarily nominal. Now, given that the amp has performed fine for the last 8 years, perhaps because I have never had a need to push it too much with the La Scala's efficiency, is it safe to assume this configuration is safe electronically? Then the final question remains of would the sound characteristic of the power tubes be much different between these two tubes types?

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I am not a technician.  There are a number of people, including “tube fanatic”, who know 1000 times what I know about electronics.  I am a classical music lover, hi-fi enthusiast, and tube amp collector.


IME, output tubes affect the sound of an amp less than the input tubes, assuming they’re functioning properly – e.g., not worn out.  If you’re wanting to try different output tubes, I suggest that you investigate the 6P14P-EV that I mentioned.

   
You can google how to set bias on the 299B.  Again, I’m not a tech.  The only time I adjust bias is for amps that have test points installed on top of the chassis.   (Craig / NOS Valves installed test points for some of my amps.)


Several years ago, I did extensive listening tests of the sound quality of various 12AX7s.   FWIW, two new production 12AX7s that I like are the Tung-Sol (for a warm, rich sound), and the new production Genalex Gold Lion 12AX7 / ECC83 / B759 gold-pin tubes (Russia).   (The non-gold-pin Gold Lion 12AX7 is a completely different tube - made in China, short plate – and doesn’t sound as good, IMO.)


One thing I’ve learned, is that tube sockets can become worn, and loose.  This can cause problems.  Be careful regarding how many times you’re swapping tubes in a vintage amp.   There is a product called a “socket saver”, but I’ve never tried them.


Good luck.
 

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Thanks Robert for this info - I have read about the Tung-Sol and are on my list to try - but I had been reading about their power tubes. If I can get those little tubes out of their aluminum cylinders, I can find out what I currently have.

 

Now that I found out I have the B, I also discovered that I actually own all the original service and operating manuals for the B in my drawer along with some notes from the tech I bought the unit from (He had been a tech for HP). These have some information on how to set the bias - and even mention an adjustment for hi fi collectors to push their units a little less.

 

Cheers!

 

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Be careful about using blanket recommendations to influence your selection of brands.  Many vendors will describe a particular brand as having all kinds of characteristics.  While that may apply in some equipment, it certainly is not universal. 

 

The same applies when someone says that brand "A" sounds fantastic (to them- you may not agree at all) in their Lafayette amp and recommends it for use in any piece of equipment.  Tubes act synergistically in a given piece of equipment.  It may be the total effect which you are hearing, and not the influence of just the one tube.

 

 If you get into NOS tubes, be skeptical of those who tell you that the shape of a getter,  color of the heat dissipation coating on the plate (typically gray or black), or color of the glass makes a huge difference in the sound.

 

And with any tube, normal production tolerances which affect the spacing of the elements within the tube can affect the sound in some circuits.  Usually the difference is slight, but may be discernible if one listens hard enough.

 

These are general rules to consider.  In the end, you need to experiment and trust your ears.  That's the only way to know what makes you happy.

 

 

Maynard

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Here is an old thread about this very issue.

 

 

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