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Help with Hybrid Design

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SerpentRuss:
Hey guys, new here.  I've been lurking for a few weeks and enjoying looking back through old posts hoping to gather some knowledge.   I started a project a couple of months ago and I have a couple of questions.

There is a seller on eBay that occasionally sells small tube guitar amplifiers housed in small, unique enclosures.   I have been outbid on the couple that I've tried to buy.  I look on eBay infrequently and he seems to offer amps on a rare basis.  I contacted him directly and asked him if he would sell me a kit and he was kind enough to reply with a schematic, but he wasn't interested in selling me a box of parts or supporting his design.  I get the feeling that he makes each amp a bit differently.

The power supply for the amp I'm trying to build features an inexpensive 7-volt Antec Toroid transformer with the 120-volt coils split, making it a small isolation transformer.  The 7-volt side is used for the tube filament.  The output transformer is a cheap 70-volt distribution transformer. The output is supposed to be in a 1/2 watt range.  I have sourced all the parts and have started working.  I think I have about 30 dollars in the parts.

If I was going to insert a tone stack in this circuit in the solid-state pre-amp, where would it go?  I'm thinking it would insert prior to the gate of the third LND150.  Also, the quality of the schematic jpeg is pretty bad.  I've assumed the gaps in some values are missing decimal points.  For example, this would make the cap in series with the volume pot 4.7N.  Does that seem right?

SerpentRuss:

As it happens this seller has an amp up for sale made into a computer power supply.   Interesting build and he included a schematic for this one.  I wonder if he's on this forum.  And no, he's not me.


https://www.ebay.com/itm/Custom-Low-Watt-Tube-Push-Pull-Guitar-Amplifier-with-Tone-and-Headphone-Output/133599983433?hash=item1f1b2df749:g:hbkAAOSwsbFfzwds

phatt:
The problem with tone stacks (assuming a normal Hiz fender type tone circuit)
is that they suck a lot of energy from the signal level (often termed insertion loss)
You can loose as much as 70% of the signal that way and you would need another gain stage otherwise the Amp will be very low on output. xP

A better option might be to add a separate tone circuit in front.
I have a circuit for such situations if you are interested I can post it?

Or maybe just use an EQ type pedal to give you an idea of how well that works.
Phil.

SerpentRuss:
Phil, I'd like to see it, if you don't mind posting it.

phatt:
Go here , Schematic is on the 2nd post.

https://www.ssguitar.com/index.php?topic=4895.msg38543#msg38543
Yes I know it does not have a preamp  :o and some think it strange but this does not need a preamp just plug your guitar into it.
I've lost count of how many of these I have built for players and No one has yet complained.
Just make sure you you use a Log pot for the Bass. I doubt you will ever need more treble but if so just lower the value of C8.  will run on 9V or up to the limit of the opamp and cap voltages used.
I run mine on 18V
Have fun, Phil.

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