Monkeymatic S'express 15-watt
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Monkeymatic S'express 15-watt
Witness! The inception of my small Express, thus, "S'express".
Thanks to RJ for the inspiration, and to others for the spare parts, including the iron, which is a 1980s tranny set for Rivera-era Fenders. I have taken many liberties with the layout, stealing ideas from Hoffman, Huss, HAD, etc., and completely throwing caution to the wind.
Chassis is a blank from Watts, 12.5" x 8" x 2.5". [updated layout, see next page]
Thanks to RJ for the inspiration, and to others for the spare parts, including the iron, which is a 1980s tranny set for Rivera-era Fenders. I have taken many liberties with the layout, stealing ideas from Hoffman, Huss, HAD, etc., and completely throwing caution to the wind.
Chassis is a blank from Watts, 12.5" x 8" x 2.5". [updated layout, see next page]
Last edited by xtian on Sat May 17, 2014 6:26 pm, edited 2 times in total.
I build and repair tube amps. http://amps.monkeymatic.com
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Re: Monkeymatic S'express 15-watt
Thanks xtian
Is this a build in the works?
I have a 18watt PT and a DR OT
on the shelf I might give this a shot.
Darin
Is this a build in the works?
I have a 18watt PT and a DR OT
on the shelf I might give this a shot.
Darin
Re: Monkeymatic S'express 15-watt
I have 95% of the parts, but haven't started building yet. This will probably get built over the next few weeks. I'll keep posting.
I build and repair tube amps. http://amps.monkeymatic.com
Re: Monkeymatic S'express 15-watt
Xtian
Is this gonna be a 6V6 version? MV, really??
Is this gonna be a 6V6 version? MV, really??
In theory, theory is the same as practice. In practice it's different.
Re: Monkeymatic S'express 15-watt
No, those are noval sockets for EL84. Yes, MV.
I build and repair tube amps. http://amps.monkeymatic.com
Re: Monkeymatic S'express 15-watt
Xtian
Nice addition to your amp choices....
Nice addition to your amp choices....
In theory, theory is the same as practice. In practice it's different.
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Re: Monkeymatic S'express 15-watt
Will be looking forward to updates
What is your iron specs?
I might see 350V@120ma on the plates using the 290v-0-290v PT
hoping its close enough for a 6V6 xpress.
Darin
What is your iron specs?
I might see 350V@120ma on the plates using the 290v-0-290v PT
hoping its close enough for a 6V6 xpress.
Darin
Last edited by dcribbs1412 on Fri May 16, 2014 7:29 pm, edited 1 time in total.
Re: Monkeymatic S'express 15-watt
Mine is going to be very low voltage. I'm using a Fender A019118 "Super Champ" transformer, with 310vac unloaded HV. That will probably give me 260vDC on the plates. Might have to throw up my hands and put in a different PT when I'm done...but we'll see.
EDIT: Well, I'm less concerned about the voltage after reviewing the EL84 datasheets, which have a spec for 250 on the anodes of a P-P pair in class AB.
EDIT: Well, I'm less concerned about the voltage after reviewing the EL84 datasheets, which have a spec for 250 on the anodes of a P-P pair in class AB.
I build and repair tube amps. http://amps.monkeymatic.com
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Re: Monkeymatic S'express 15-watt
What math are you using....Not sure if this is right but I have seen others use 1.2 and 1.4 as a multipliersxtian wrote:Mine is going to be very low voltage. I'm using a Fender A019118 "Super Champ" transformer, with 310vac unloaded HV. That will probably give me 260vDC on the plates. Might have to throw up my hands and put in a different PT when I'm done...but we'll see.
1.2x310V=372V loaded? or 1.4x310v=434 unloaded?
After looking into the load calcs a little further (1.2x290V=348V)
I may only see around 350V at the plates.
Darin
Re: Monkeymatic S'express 15-watt
Check out Hammond's Design Guide for Rectifier Use:
http://www.hammondmfg.com/pdf/5c007.pdf
Mine is a full-wave bridge, cap input. V(peak) = 1.4 x secondary HV, and V(average) = 0.9 x secondary HV.
So, I'm multiplying my 310vac unloaded by 0.9, and then AGAIN by 0.9 as fudge factor for value under load.
http://www.hammondmfg.com/pdf/5c007.pdf
Mine is a full-wave bridge, cap input. V(peak) = 1.4 x secondary HV, and V(average) = 0.9 x secondary HV.
So, I'm multiplying my 310vac unloaded by 0.9, and then AGAIN by 0.9 as fudge factor for value under load.
I build and repair tube amps. http://amps.monkeymatic.com
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Re: Monkeymatic S'express 15-watt
Thanks xtian
good info
looking forward to your build
Darin
good info
looking forward to your build
Darin
Re: Monkeymatic S'express 15-watt
Xtian
But an Express preamp with EL84s? Liverpool??
But an Express preamp with EL84s? Liverpool??
In theory, theory is the same as practice. In practice it's different.
Re: Monkeymatic S'express 15-watt
it looks like its fixed bias thoughJoeCon wrote:Xtian
But an Express preamp with EL84s? Liverpool??
Re: Monkeymatic S'express 15-watt
Ok so a cross between the Liverpool and Express! I like it...
I've got a chassis punched for EL84s maybe I should build one too...
Thanks.
I've got a chassis punched for EL84s maybe I should build one too...
Thanks.
Last edited by JoeCon on Wed Oct 14, 2015 12:48 pm, edited 1 time in total.
In theory, theory is the same as practice. In practice it's different.
Re: Monkeymatic S'express 15-watt
I'm following RJ's lead on this one. Express preamp, EL84 power section, fixed bias. Yup.
I build and repair tube amps. http://amps.monkeymatic.com