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Leak Stereo 50 Tubes and other animals.

Borg7x9

Borg7x9

Member
Hi Guys,

As part of my Vintage Audio Journey ( I'm building some Altec 604-8k / 620 cabs ) I've just bought a Leak Stereo 50 and varioslope Pre. They sort of worked and did some things beautifully. But... there was quite a bit of hum from the Pre and the Pots and switches were scratchy and just felt very old. They are both at the tube amp doctors being measured and having bits replaced where required and everything cleaned.

My question is... The Stereo 50 uses 4 x EL34's. Can I use KT77's in this amp ? A friend has a quad of Gelalex Golden Lion KT77's that I can buy "cost effectively" that I'm told are very nice sounding EL34 type tubes.

Appreciate confirmation or just thoughts in general on these amps.

Thank you....I hope you are all well.
 
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Borg7x9 said:
Hi Guys,

As part of my Vintage Audio Journey ( I'm building some Altec 604-8k / 620 cabs ) I've just bought a Leak Stereo 50 and varioslope Pre. They sort of worked and did some things beautifully. But... there was quite a bit of hum from the Pre and the Pots and switches were scratchy and just felt very old. They are both at the tube amp doctors being measured and having bits replaced where required and everything cleaned.

My question is... The Stereo 50 uses 4 x EL34's. Can I use KT77's in this amp ? A friend has a quad of Gelalex Golden Lion KT77's that I can buy "cost effectively" that I'm told are very nice sounding EL34 type tubes.

Appreciate confirmation or just thoughts in general on these amps.

Thank you....I hope you are all well.
Click to expand...
The EL34 is a power pentode and the KT77 is a beam power tube. Their filament current requirements are 1.5 and 1.4 amps respectively. You could use the KT77 in the Leak but it was designed for the EL34 and both tubes types were available when the Leak was introduced. I personally stick to what the equipment designer specified. You did ask for thoughts.....
 
What are the grid resistors in the Leak? There is something about different G1 resistor values depending on bias method and plate dissipation with a KT77 vs an EL34. Need to see a schematic.
 
ramjet said:
The EL34 is a power pentode and the KT77 is a beam power tube. Their filament current requirements are 1.5 and 1.4 amps respectively. You could use the KT77 in the Leak but it was designed for the EL34 and both tubes types were available when the Leak was introduced. I personally stick to what the equipment designer specified. You did ask for thoughts.....
Click to expand...
Hi RamJet. I see the circuit diagram describes. El34, KT66 or 5881. I had read that the KT77 was a direct replacement for EL34, but it seems its not quite that straight forward. I appreciate your thoughts. Especially if it'll stop potential harm to my newly fettled amps.

Cheers !!!
 
so cathode biased, and its a 680k grid resistor. Looks like about 22 watts plate + screen dissipation.

1731893484956.png

per that it allows up to a 1M grid resistor, so you're fine with a KT77.
 
Lovely amp! IMO, the Varislope preamp betrays its age even when it's working optimally. The amp is sweet but the combination of the two gets a bit "gluey" for my tastes. But I'd be interested to hear what you think of the combo when they're back from the tech.
 
zackthedog said:
Lovely amp! IMO, the Varislope preamp betrays its age even when it's working optimally. The amp is sweet but the combination of the two gets a bit "gluey" for my tastes. But I'd be interested to hear what you think of the combo when they're back from the tech.
Click to expand...
Hi Zacktd. Thanks for your thoughts. My tech just phoned. All is ready and has turned out well. He replaced some non standard wiring and work that had been done previously And was happy that they were now working well. I'll pick them up tomorrow morning. Looking forward to it. i'll give them a whirl with some Living Voice Auditorium speakers I have here. They are pretty high sensitivity so should go well. I bought them to use with the Duplex Altecs when they are finished. might be a while away though. He says KT77s will be ok in that circuit. I know what you mean about the Glueyness... I think the Altec horn will eliminate that a bit, They should be a good match. I see you have proacs. I used to have a pair or Response 3.8 a few years back.... lovely speakers... I'll post my thoughts (and some pics) here after having a listen.
Thanks again.
 
Hi All . i’ve had my amps back from the shop. They sound great. I can’t wait for my Altecs to be done now. So how do they sound ? Well I think they sound very nice. Soundstage is good front to back and width wise. They pull out the main performance from the mix nicely.. not in your face , but quite naturally. The sound is nice and free of the speakers. i’m using a very cheap yamaha streamer as a source right now and it has no right to sound so relaxed but engaging. The Pre doesnt like being very close to the Stereo 50 it picks up quite a bit of transformer hum. a couple of feet apart is fine. there is still some noise inches from the speaker but not noticeable a couple of feet away. and certainly not with music on. i’m very happy. just another question though. What RCA plugs do you Leak guys use on the original sockets on the back. My MIT cables won’t fit, unless i take the outer part off. i don’t really want to change them out for modern ones, they sound good.

I’m happy to buy cable and connectors and make some up a bit more period correct if that’s a good way to go.

i did have some components changed as well as having an IEC connector added. the original was corroded and dropping earth. See bag of replaced bits below.

Hope you are all well.
 

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Try a Switchcraft 3502a

Thanks Gadget. Looking at the drawing they are only 10.3 mm outside diameter. That would be the narrowest I've seen. I'll order some. Perfect.
 
If you're feeling fancy you can get them with gold contacts, 3502aau, or if you want a black barrel with gold contacts, 3502abau. Lots of old tube gear puts the RCA jacks with narrow spacing and these fit well without being really crappy.
 
gadget73 said:
If you're feeling fancy you can get them with gold contacts, 3502aau, or if you want a black barrel with gold contacts, 3502abau. Lots of old tube gear puts the RCA jacks with narrow spacing and these fit well without being really crappy.
Click to expand...
Those black collet connectors look real fancy... perhaps I'll order some belden Cable and some of the Different plugs and see if I prefer one or the other. The Leak has old silver coloured connections ( under the oxidation ). So I doubt I'll be able to tell. having said that it seems everything makes a difference.
 
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