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Old 16th Sep 2020, 9:58 am   #1
Valvepower
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Default EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

Hi,

From the post for large B7G bases in the wanted section as I felt a separate thread was in order here.

Itís uses a pair of EL95ís in push pull with a Radiospares Hygrade output transformer. The EL95 specifies 10K a-to-a, however the Hygrade is 8K a-to-a, but given this amp is being made with parts from the spares/toy box there is going to have to be some artistic licence! Iím hoping the Hygrade has a reasonable primary inductance to give a decent LF response. I could slightly re-bias the EL95ís to accommodate the 8K a-to-a though.

For the driver Iím thinking of using the Jeffery (Wireless World Aug 1947) high gain phase splitter using EF184 valves, again using valves found in the spares/toy box.

The chassis is an early Sterns 5-10 chassis which had been liberated of its transformers and other ďusefulĒ parts Ė this explains wanting the bigger B7G valve bases.

The mains transformer could be a 2x 50V medium sized toroid with series windings configured as a full wave voltage doubler to get the necessary HT. An alternative to this is a Radiospares Standard transformer with a 275V-0-275V at 100mA which is more than enough.

I'm not aiming to set the world alight with audio performance, but make something using parts from the spares/toy box

Regards
Terry
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Old 16th Sep 2020, 11:14 am   #2
GrimJosef
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

Driver valves fatter than the output valves - that's the way bits-and-pieces amps should be !

The 100W/ch Radford STA100 uses a pair of EF184s as the phase-splitter/driver stage behind a pair of KT88s. I don't think you're going to be short of drive.

Cheers,

GJ
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Old 16th Sep 2020, 7:52 pm   #3
bikerhifinut
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

I shall watch this with relish Terry.

You're going to shame me into finally getting up and running with my pair of HygradesÖÖÖÖÖÖÖÖÖ...

Andy
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Old 17th Sep 2020, 11:08 am   #4
Valvepower
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

Hi GJ,

Hadn't looked at it that way - I could call it the Little and Large amplifier... If it weren't for using an EZ81 - if I decide to use the Radiospares Standard mains transformer - I could use the GZ30/5Z4GT and then you'd have small medium and large valves.... Then it could be called the three Bears amplifier with Baby valve, Mummy valve and Daddy valve..... .... Sorry must get out more often

Hi Andy,

Fingers crossed.... as you know I've been saying I'll do projects like this, now that I'm semi retired.

I think you should raid your spares/toy box and use those nice 6V6GT's in single ended amplifier.

Terry

Last edited by Valvepower; 17th Sep 2020 at 11:10 am. Reason: Triping Errot
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Old 17th Sep 2020, 10:59 pm   #5
bikerhifinut
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

I guess you have a point Terry.

I found the mains transformer from the scrapped Japanese EL84 amp with the 220V primaries and as I have a transformer I can use to "buck" the primary to use with our 245+V Mains I figure it'll work nicely on the 6V6.
Now then where's that circuit diagram for the radio Constructor "neophyte" in my pile of papers...ÖÖÖÖÖÖ..

I've got a 6V6 amp working SE at the moment but its running a low HT and I figure it runs out of steam at about 2W.

A.
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Old 20th Sep 2020, 8:35 pm   #6
kestrelmusic
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

I've just built an amp using oddments from stock. It has an EF37A front end, 6SN7 phase splitter, a pair of AC/Pen's output and an 80 rectifier. 5 bottles, 3 different base types! The reason for using AC/Pen output valves was that I wanted to use an odd mains transformer that had 4V, 5V and 6.3V LT secondaries! The transformers came from an old dud amp which I stripped. I am highly suspicious of the alleged output transformer - it has a centre tapped secondary! I suspect it is a heater transformer pressed into service...
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Old 22nd Sep 2020, 4:06 pm   #7
Valvepower
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Default Re: EL95 bitís this and bitís Ďa that amp (from Wanted section) Ö

Hi,

I suppose the transformers pretty much dictate the direction of the design of a bits Ďa this and bits Ďa that project. Ah, the AC/PEN thatís a proper Ďole bottleÖ

Quick updateÖ I did a quick trawl of the Forum and found the EL95 got some quite bad press, however, Iíll still use the EL95 with the Hygrade transformer, although, I did find 4x 6BW6ís Iíd forgotten about (thought Iíd swapped them with a friend a while back), these along with using a pair of Radiospares EL84 output transformers from the pension fund or if I don't want to raid the pension fund I could use a pair of EL84 output transformers salvaged from a basket case Jason J2-10 a good wile back, anyway either of these and the 6BW6's would make a nice bits Ďa this and bits Ďa that project.

Regards
Terry.
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