Sorry newbie question...
What is the difference between this two tubes? Which is the better sounding? I have a Pioneer SA810, i know it is not a transistor amp but a tube one. The one came with the amp is a 7868 and can i substitute a 7591a? I havent tried yet. Care anyone to enlighten me.
What is the difference between this two tubes? Which is the better sounding? I have a Pioneer SA810, i know it is not a transistor amp but a tube one. The one came with the amp is a 7868 and can i substitute a 7591a? I havent tried yet. Care anyone to enlighten me.
http://scottbecker.net/tube/sheets/049/7/7868.pdf
Noval, 9 pin
http://scottbecker.net/tube/sheets/127/7/7591.pdf
Octal, 8 pin
And, difference in circuits.
Bob
Noval, 9 pin
http://scottbecker.net/tube/sheets/127/7/7591.pdf
Octal, 8 pin
And, difference in circuits.
Bob
They have identical characteristics but different bases - so unless you like to change tube sockets... you'll be sticking with 7868s. There are new 7868s available from ElectroHarmonix - but they have oversize pins (.050" vs. .040"), so it's a one-way trip if you use them - the sockets won't hold the old version once you use the new ones.
Which sound better the 7591a or the 7868? I better ask first before making the plunge...There is no turning back then...
As pointed out previously the 7591A and 7868 are not directly interchangeable - to use the 7591A you would have to change out all of the power stage tube sockets.
For a given brand and vintage the innards (plate structure and internal construction) are virtually identical so you should expect no difference provided they were made at the same time in the same plant. Lot to lot and brand to brand variations would be typical of that experienced with other types. Therefore, IMHO I would not expect anyone to be able to give you a concrete answer to this question.
I think it comes down more to cost/availability and your comfort wrt to replacing sockets and doing the required rewiring.
FWIW I would probably just stick with 7868 and save the significant effort involved in a socket change for no concrete gains. The one exception I would make is if the sockets were in poor condition and needed to be replaced - then I would probably choose the octal option.
For a given brand and vintage the innards (plate structure and internal construction) are virtually identical so you should expect no difference provided they were made at the same time in the same plant. Lot to lot and brand to brand variations would be typical of that experienced with other types. Therefore, IMHO I would not expect anyone to be able to give you a concrete answer to this question.
I think it comes down more to cost/availability and your comfort wrt to replacing sockets and doing the required rewiring.
FWIW I would probably just stick with 7868 and save the significant effort involved in a socket change for no concrete gains. The one exception I would make is if the sockets were in poor condition and needed to be replaced - then I would probably choose the octal option.
IF the large bottle of the ElectroHarmonix 7591 will fit in the available space, change to Octal sockets and install EH 7591s. An EH 7591 and an Octal socket costs less than an EH 7868.
Thanks for your helpful comment. As for now it is easier for me to get EH in my place. I do not mind changing the sockets as the sockets is already 30+ years. Will the EH7591 be better sounding than EH7868? Please bear with me as i have not seen nor heard either of the tubes before. If i want the tubes i need to place an order with my local agent and have it imported in from US. This is a costly affair for me. The tubes in my existing amp is the original Toshiba 7868.
I have read somewhere in the net that the 7868 is a newer version of 7591a, is it true?
BTW I know of 7591a thru Sansui AU70 also toshiba tubes.
I have read somewhere in the net that the 7868 is a newer version of 7591a, is it true?
BTW I know of 7591a thru Sansui AU70 also toshiba tubes.
The 7868 really is just a rebased version of the 7591A internal differences are pretty insignificant. The only thing that is slightly newer about the 7868 is the envelope it was stuck into, and that is only by a couple of years at most.
One nice thing about the larger pinned 7868 EH - if the original sockets are tired the larger pins solve that problem for you with no work at all! If the original sockets aren't cracked or damaged but just have loose contact with the 7868 socket - the EH is a no-brainer.
I think old stock 7868 is pretty much gone too. What's left is what's in private hands and not for sale. Not many will be able to "go back".
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My two Eurocents:
Stay with the Novar sockets, get yourself a decent matched quad of EH 7868, clean the sockets, and plug the EH7868 - their base pins diameters are between Magnoval and Novar base diameter, so the fit will be rather tight, but then, you shall have lower contact resistance than with the Novar-based 7868.
I know the EH7868 as both reliable and electrically well behaved - the sound should then be ok, too...
Best regards,
Micha
===
PS: Be very weary with 'old stock' 7868 sold on eBay - there is a lot of junk out there waiting for people to be fooled... many are worn out despite the fact that they are sold as "NOS". Real NOS 7868 in pristine state are quite rare, and frequently expensive if offered.
Stay with the Novar sockets, get yourself a decent matched quad of EH 7868, clean the sockets, and plug the EH7868 - their base pins diameters are between Magnoval and Novar base diameter, so the fit will be rather tight, but then, you shall have lower contact resistance than with the Novar-based 7868.
I know the EH7868 as both reliable and electrically well behaved - the sound should then be ok, too...
Best regards,
Micha
===
PS: Be very weary with 'old stock' 7868 sold on eBay - there is a lot of junk out there waiting for people to be fooled... many are worn out despite the fact that they are sold as "NOS". Real NOS 7868 in pristine state are quite rare, and frequently expensive if offered.
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YES , entirely correct . I agree
I have a reasonable experience about that .
I could repair and restore some Pioneers SA810 with the 7868 as autput tubes , and many The Fisher ( some models ) that invariably uses the 7591 as output tubes .
My advice : Do not swap the original Pioneer's SA810 tubes .
IMHO the sound quality of a decent matched pair of 7868 is much BETTER
than the sound of a decent matched pair of 7591 . I have no doubt about it.
The Pioneer SA810 , is great , ( IMO ) may be the best tube amp , made by
Pioneer . Well restored , "recaped" , and adjusted , it sounds great . 😉
Carlos
Carlos, on what basis do you make this assertion? Particularly as the internal construction of both types is generally identical from a specific vendor, and vintage. I have heard an amplifier that was socketed for both types and could hear no difference whatsoever between devices of the same brand and vintage.
Comparing vintage and modern types with different basings is not conclusive, and comparing between two entirely different amplifiers one using 7868 and the other 7591A is also not conclusive.
Modern production 7591A and 7868 (and indeed vintage) are made on the same tooling, the only difference is in the envelope and base used - therefore there can't really be any significant difference between the two unless you maintain that the pins themselves are to blame.
The main reason for the 7868's existence is that RCA determined that the basing arrangement was a significant % of the overall manufacturing cost, eliminating one assembly step, and the associated components reduced costs and the 7868 could therefore be sold for less in production volumes and its use justified in more cost sensitive applications than the 7591A.
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Thanks for the input Guys! I must agree that the Pioneer SA810 is better built compare to the Sansui AU70's. I might be wrong. I have decided to stick with the 7868 untill it comes a time where i am not able to get new 7868 anymore. Now i have schema from Ginger(Big thanks) and now i would like operating manual or brochure to fully appreciate this amplifier. Btw what is manufacturer claim output power?
Refference, how do you compare the sound of the SA810 to the Fisher? Forgive me, in my side of world i have not encounter 110V classic Fisher before....
Can someone tell me the dimension of the EH7591a for my future project. Maybe source some fisher iron also...Will it be cheaper to buy a used Fisher receiver?
Can someone tell me the dimension of the EH7591a for my future project. Maybe source some fisher iron also...Will it be cheaper to buy a used Fisher receiver?
Hi Kevin ,
The basis for my assertion are my ears and almost 40 years working
with audio and tube amps .
As I said “ IMHO “ ( in my humble opinion ) , and it is exactly what it is :
only a opinion .
Every time that I could hear the 7591 and the 7868 , and compare
between the two types , I felt that 7868 was a bit superior , more dynamics
and a more pleasant sound .
Today , after sometime I can not remember exactly the reason why it happened that way .
May be because the 7868’s brands I had listened , was far superior of 7591’s
brands . Perhaps that was the cause .
Any way , thanks for your explanation .
I do not want to start any kind of debate , about subjective impressions .
Hi hoyhoysum ,
Very easy to answer , again in my opinion , the Pioneer SA810 , sounds
better than many Fisher’s models , however the Fisher model 50 and
model 55 , only to mention two of them , are very ,very good .
Regards ,
Carlos
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