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stereo SE kt88 build ... abdellah diyaudioprojects design

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#381
Yeah my computer's broken so I'm reading all this on my iPhone, and not carefully enough I know.

I mistook the volume pot for trimmer adjustable biasing like you see on some amps, there were some on a jolida pp schematic I considered.



WOOPS :/
 
#382
Edcors are excellent transformers and I'm sure the mid-line Edcors will sound fine. If you want to spend a little more money for wider bandwidth, these are the ones I used, excellent specs for the price. 10Hz - 37KHz (-3dB), 10Hz - 25KHz (-1dB), 20Watt, 150mA.
They sound great and they way they mount looks really nice. Be warned though these are shipped standard surface mail. Mine took about 60 days to arrive, but can take up to 80 days.

5K SE AUDIO OUTPUT TRANSFORMER FOR ,KT-88, EL-34 CHROME - eBay (item 230426787783 end time Jan-30-10 02:23:12 PST)

These have the same frequency response as above, only difference is the input impedance is 4.5K instead of 5K. I was recently quoted on these for a pair including airmail shipping (6-10 days) USD $151.10.

LM-2014U:
Audio Catalog

Hope this helps,

Scott


raypalmer said:
Ah nuts I didn't See that they were pp....

I guess It has to be the edcors! The power tranny is only 50 bucks though so depending on shipping I may still get that ( no 5v tap but the 6.3's are 5a so I can run all four tubes off of one of those and drop the other 6.3 down to 5v for the rectifier)
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#383
Off Topic

Sorry for the off topic and noobie question.....

I would like to know why there is some sort of "clink clink" sounds from the Sovtek 5AR4 tube whenever I power down the amp? Is this normal?

Disclaimer:
The amp is not in a pub and not near any whisky glasses 😀
 
#386
cjctan said:
Sorry for the off topic and noobie question.....

I would like to know why there is some sort of "clink clink" sounds from the Sovtek 5AR4 tube whenever I power down the amp? Is this normal?

Disclaimer:
The amp is not in a pub and not near any whisky glasses 😀
Click to expand...

i have the same with a 5u4 , i think your hear the expanding and shrinking of the tube by the heat
grtz ko
 
#388
seel34 said:
i am thinking to try out some kt88 tubes , with wich brand tubes [now made]
you have good expirience ???
thnx for the tip of the kt77 , i understand its risky to buy them on ebay
cause there are some bad tubes circulating
thnx grtz ko
Click to expand...

I used the Electro-Harmonix KT88 EH and for USD$60.00 per matched pair from tubedepot.com I don't think you can go wrong. They sound fantastic in my build. Lots of clear bass, sweet high end.

Scott
 
#389
scitizen17 said:
I used the Electro-Harmonix KT88 EH and for USD$60.00 per matched pair from tubedepot.com I don't think you can go wrong. They sound fantastic in my build. Lots of clear bass, sweet high end.

Scott
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I have a quad of McIntosh KT88 which are basically EH labeled for Mac. I love them too, you won't be disappointed. I picked them up used for $120 the quad, basically new b/c they were the tubes that came with a new amp and the guy just upgraded and sold these off. You will find these occasionally on eBay like this.

I really love the RCA big bottle 6L6GC tube, it is my favorite of the group....very sweet in triode. The KT88 in pentode is powerful, lots of deep solid bass but I think it needs a little NFB to settle it down some.

Scott, you have a PM.

Jeff
 
#393
cjctan said:
Hi Jeff,
May I know what is your configuration in this amp when using 6L6GC? It sound weird when I used the new Tung Sol 6L6GC on mine
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Well, I have described it in detail a couple of times on this thread a few pages back so I won't repeat everything here. I run the bias with the 560R setting. My coupling caps are Russian PIO K40 type, all of my resistors are PRP and most wiring is silver in the circuit path. BG bypass caps and ASC and Solen filter caps. All Edcor Iron too.

I am using NOS RCA, circa 1960's which might have alot to do with it as well. There still is plenty of power too with the 6L6 but not as much as the KT88 of course. Each build is going to have it's own sonic fingerprint so it is likely that the 6L6 may never sound the way you like on you particular build.

I have also used some EL34 with good results......just about every tube I have tried sounds really great really.

Jeff
 
#394
did any one try a gu50???i was reading about this tube and it seems to be able to replace the kt88 [different tube sockets needed ] and some other changes but not to masure , i gives a lot of power and its really cheap to get on ebay
it is suposed to give 10 watts se in triode
any body any idea what will be the pro and cons of this conversion ?
grtz ko
 
#395
seel34 said:
did any one try a gu50???i was reading about this tube and it seems to be able to replace the kt88 [different tube sockets needed ] and some other changes but not to masure , i gives a lot of power and its really cheap to get on ebay
it is suposed to give 10 watts se in triode
any body any idea what will be the pro and cons of this conversion ?
grtz ko
Click to expand...

The GU50 cannot replace the KT88 because it is a rectifier tube. It may be able to replace the 5U4G but I am not even certain of that. Besides, even if it could, it is probably the ugliest tube I have ever seen!
GU-50 GU50 / NOS / Audiophile Pentode TUBE / LS50 QTY=4 - eBay (item 300390761059 end time Feb-25-10 01:04:14 PST)
Jeff
 
#396
I stand self-corrected

I initially looked this tube up in Duncan Amps TDSL 1.1 and looked at all the links on it. The TDSL GU50 is a rectifier tube. It does not make reference to the Russian tube with the same designation, clearly there are 2 different types of tubes that are un-related>

I was eventually able to find the following on the web:

Name GU50
Type pentode
Cathode type: oxide,indirect heating
Application field: power amplification up to 60W up to 66MHz in special equipment
Envelope: glass
Cooling method: air
Dimensions: 93.5mmx45.3mm
Mass: 100 g
Filament voltage: 12.6 V
Filament current: 0.6 - 0.85 A
Mutual conductance: 3 to 5.5 mA/V
Output power: 40 W
Maximum anode voltage: 1kV
Maximum operating frequency: 66MHz

Not much else I could find on it however. With the above as the only info I could find on this weird tube it is hard to say if it can be used in the KT88SE circuit. If you can come up with some more specific specs that would be helpful.

Jeff
 
#397
hallo jeff
here some info about the gu50
GU50-SE-Amp-Amp von Sven Bolte

KT88 and 6550 Tube Directory - [ Vertaal deze pagina ]
You like "another" tube than KT88, well it's a bit off topic... but try GU50. They're low cost and much better than KT88. GU50 is amazing quality Russian ...
KT88 and 6550 Tube Directory - In cache - Vergelijkbaar

Russian GU50 Power Pentode a bit like KT88 • DIY Audio Projects Forum

http://www.diyaudio.com/forums/tube...ier-class-6sn7-full-construction-details.html

GU50 single end

greetings ko
 
#399
seel34 said:
hi jeff
i was thinking to use the end of this schematics and keep the 6n1p from thew original schematics kt88 ,whats your opinion ?
i got intresting after reading the article [see previous post ] from jac music
where they say that this tube beats a kt88 easy
http://www.diyaudio.com/forums/atta...onstruction-details-gu50-se-triode_resize.jpg

greetings from amsterdam
ko
Click to expand...

I really can't comment, I just am not too familiar with this tube, even after I read a few of the links you gave.

Have you built this amo (KT88SE) as-is? If you really want my opinion, I would first builkd this amp as-is on this thread then try to modify it later.

I find this amp has plenty of power and drives my Proac 2.5 Response clones much louder than I would want to listen to. I certainly think I don't need any more power. You could always try to adapt this front end to the GU50 but in the end you will have basically built an entirely different amp I think. That is just my opinion but, you did ask for it😉
Sorry I can't help you more.
Jeff
 
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