HoSo56 & 5879 OD

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10thTx
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HoSo56 & 5879 OD

Post by 10thTx »

I built a HoSo56 (Da Geezer's amp design off of Hoffman amp forum), but with some changes and a 5879 switchable OD channel.

Very touch sensitive amp. Clean channel is FAT with a dash of chime. Light playing is clean, moderate picking is on edge breakup, aggressive picking you have some break up & OD all on the clean channel with same volume settings. Note definition is excellent even when chording.

To my surprise, the OD channel is the creamiest overdrive I've gotten out of any amp build. Very very smooth tone and more like a boost then a strong overdrive. It does NOT have the type of sustain as a Dumble amp or the D'Mars ODS or the Tweed BluezMeister amps.

IF you build this and want a place to experiment, try different value caps off the cathode follower behind the 5879 pentode in the OD channel. Try a range from .0047 all the way up to .1 & see what you like.

Just thought I'd share for someone wanting to try a quasi-new idea.

With respect, 10thtx

** EDIT: I had an error in the original schematic and layout. The tone stack was bypassed going into the 5879 OD channel. And at this juncture, I have a .022 Musicap paralleled with a .022 Orange Drop PS off the cathode follower of the 5879 OD tube. Please accept my apology for the error.
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Last edited by 10thTx on Sun Mar 13, 2016 9:18 pm, edited 2 times in total.
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TUBEDUDE
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Re: HoSo56 & 5879 OD

Post by TUBEDUDE »

Looks nice. Any clips yet?
I might try it with 6V6 outputs.
Tube junkie that aspires to become a tri-state bidirectional buss driver.
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Colossal
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Re: HoSo56 & 5879 OD

Post by Colossal »

I didn't look at the .sch attachments as I don't have that application, but is there a PT, OT, and power supply called out for this build?
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M Fowler
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Re: HoSo56 & 5879 OD

Post by M Fowler »

OT shows Classictone 40-1800 but no PT data shown.
10thTx
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Re: HoSo56 & 5879 OD

Post by 10thTx »

I used a Hammond 272FX PT with 300-0-300 and 172ma

https://www.tubesandmore.com/products/P-T272FX

I used a Classictone 40-18000 OT.

http://www.classictone.net/40-18000.html

No sound clips yet. Hopefully, some in the next several weeks & I'll repost on this thread.

With respect, 10thtx
Bob S
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Re: HoSo56 & 5879 OD

Post by Bob S »

I got a few pentodes to play with so I'll be watching this.
Thanks for sharing.
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martin manning
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Re: HoSo56 & 5879 OD

Post by martin manning »

10thTx wrote:I used a Hammond 272FX PT with 300-0-300 and 172ma
I think folks are looking for the power supply schematic.
10thTx
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Re: HoSo56 & 5879 OD

Post by 10thTx »

I think folks are looking for the power supply schematic.
It was in the first post I made in the SCH file 2nd page.

With respect, 10thtx
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martin manning
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Re: HoSo56 & 5879 OD

Post by martin manning »

Well, not everyone does .sch, and for Mac users there seems to be a compatibility issue with jschem and the latest OS X. Thanks for the .gif!
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Colossal
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Re: HoSo56 & 5879 OD

Post by Colossal »

Here is a repost with a PDF
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10thTx
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Re: HoSo56 & 5879 OD

Post by 10thTx »

Thanks, Colossal !
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Colossal
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Re: HoSo56 & 5879 OD

Post by Colossal »

Thank you! Looking forward to a clip or two. The overdrive without distortion description is very interesting!
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TUBEDUDE
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Re: HoSo56 & 5879 OD

Post by TUBEDUDE »

10thTx,

I'm about half done on this and running our of front panel space. I was wondering, do you adjust the Shape control much, or is it a set and forget kind of pot. I might need to put it on the back panel if it's just adjusted with a different guitar, or inside the chassis as a trimmer, if it's a one time deal.
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10thTx
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Re: HoSo56 & 5879 OD

Post by 10thTx »

I have been surprised to find the "shape" control actually useful.

Sort of hard to describe what it does, but it's kind of dials between a more subtle OD tone to a more in your face tone edge. The OD doesn't seem to get much louder but it seems to become somewhat more aggressive. I have the shape pot set at 12 noon to 1 most of the time.

Having said that, I think you could use a 82k resistor alone instead of the 50k and 100ka shape pot. OR a mini-toggle that parallels an 82k with another 82k or 68k. You might have to play with those values some. I think something like that would reasonably duplicate the shape pot subtle to pushed tone .

I am loving this amp! It may be the most touch sensitive amp I've played. I also learned that there was more sustain then I previously thought using the 5879 OD channel. Just took a while to figure out how to dial it in.

I am really looking forward to your review of it. Your build is looking great!

with respect, 10thtx
10thTx
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Re: HoSo56 & 5879 OD

Post by 10thTx »

My amp wiring is not very neat but the amp is amazingly quiet at idle when the dials are set for a reasonably loud volume.

Given the neat builds on TAG, I am somewhat hesitant to share this but maybe the layout will be useful for others who might want to try this amp out?

With respect, 10thtx
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