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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Schematic for a small SE EL84 amp
Schematic for a small SE EL84 amp
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Old 19th April 2002, 04:03 PM   #21
planet10 is offline planet10  Canada
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Schematic for a small SE EL84 amp
Quote:
Originally posted by FlMike
could r3 and r5 be omited in this amp? if so what size R would be used in their place?
You must be referring to the neat little phase-splitterless PP amp. R3 is the tone control, it & the cap in series with it could just be eliminated. R5 is the volume control, it could be replaced with a fixed R.

dave
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Old 19th April 2002, 04:42 PM   #22
RMS is offline RMS  United States
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Thanks For the help Planet10.
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Old 19th April 2002, 07:20 PM   #23
phil is offline phil
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Way back when Mullard produced a very good book on audio with circuits. If I remember correctly there was a 5-10 amp and a 10-10 amp. These used EL84's and EF86's. From What i remember they were very popular and gave a good sound.
Does anyone have any info on these amps or if the book is still available.
Many thanks
Phil.
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Old 19th April 2002, 08:15 PM   #24
tomcat is offline tomcat
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Yep here it is... the famous mullard EL84 SE
tomcat
(hope it works; the attachement that is!)
Attached Images
File Type: gif el84_8a.gif (74.2 KB, 3057 views)
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Old 19th April 2002, 08:40 PM   #25
Brett is offline Brett
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Default Simplest 6BQ5 SE

Is this the Tubecad page you guys were looking for before?

http://www.tubecad.com/september99/page11.html

Simple. But I personally prfer the 6W compact Yves posted. The output stage of the amp I'm currently building is similar in topology.

Cheers
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Old 19th April 2002, 08:52 PM   #26
planet10 is offline planet10  Canada
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Schematic for a small SE EL84 amp
Default Re: Simplest 6BQ5 SE

Quote:
Originally posted by Brett
Is this the Tubecad page you guys were looking for before?
Yep, that is the one...

dave
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Old 19th April 2002, 11:36 PM   #27
FlMike is offline FlMike
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i am interested in building this

http://www.triodeel.com/compact.html

the opt xformers i have are from a 6bm8 amp ani i dont know any of the specs on them. what are the chances that it will work out ok? anyone know of a similar circuit that uses 6bm8"s instead of 6bq5's. this is my first project and everything else is done expect for wiring. you can see what i have done so far in this thread.

http://www.diyaudio.com/forums/showt...&threadid=1782



cheers, mike
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Old 20th April 2002, 12:39 AM   #28
Brett is offline Brett
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Hi Mike,

It's hard to say whether your transformers are suitable until you know the turns ratio. Its very easy to measure. I've never used 6BM8s.

First, turn off the amp and make sure it is discharged. Desolder the B+ and the leads to the 6BM8 plates.

Next get a low voltage AC transformer, say 3V and place it across the 8R taps. Measure the ACV with a voltmeter across the 8R taps. Then measure the ACV across the primary, plate-to-plate. Divide the primary ACV by the secondary ACV. This gives you your turns ratio. Square this number and then multiply it by 8 and you have the primary impedance plate-to-plate.

The spec in the article calls for 8kR plate-to-plate. My trans is 7kR and even though my horns should be above 8R, I think 7kR should be OK. The Dynaco ST35 was 7.1kR.

HTH
Brett
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Old 20th April 2002, 03:04 AM   #29
yves is offline yves
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Default Mind sharing your circuit?

Brett,
Would you be so kind to share your
output stage circuit that is similar to the
6W amp?
I wonder why that differential pair
output state topology
is not so common - perhaps it is the need to
get equal currents thru both tubes?

rgds
Yv
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Old 20th April 2002, 03:25 AM   #30
planet10 is offline planet10  Canada
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Schematic for a small SE EL84 amp
Quote:
Originally posted by FlMike
the opt xformers i have are from a 6bm8 amp ani i dont know any of the specs on them. what are the chances that it will work out ok?
6BM8 (ECL82), ECL86, EL95, 6BQ5(EL84) are all fairly close in terms of their OPT requirements so go for it.

dave
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