found a chassis in my storage place :D

[norburybrook]

UPDATE:

did some valve rolling and ended up with all new JJs in the pre amp. I also tried a 12 AX7 in the PI which i preferred. So with that in mind I've made the whole PI section now like #183 with the exception of the 820R-24k-390 which is close on my amp with 800R-22k-390R adn the prescence is still a 2.2uF rather than a 1uf.

I'm liking the sound of this better now. I would say in OD mode there's slightly better note definition and its a bit 'sweeter' and seems to have a bit more dynamic range with the guitar volume control.

So in some way's the amp is now like a #183 with 2nd gen low plate OD. The EQ is 'nearly' Skyliner ,1M bass instead of 500k and 500k Treble instead of 250k so it would only take a few resistors and 2 pots to turn it into a full #183....



However, I'm liking how the OD sounds and the fact you can't tweak it in some ways is good so I'm leaving it as it is, a new kind of hybrid

(edit) I'm loving the PAB on clean with this amp, it's giving it a lovely crunchy, sparkly tone that gives a Strat a nice SRV type thing. The FET also does this but in a slightly different way.

I shall post some sound clips as soon as i can.

Also made a single cable send and return today from Van Damme Star quad and some nice sleeving i bought

IMG_20191128_165107.jpg

M

[norburybrook]

and......today's tweaks......

Fitted an switchable LNFB circuit with some lovely NOS Pihers, complete with blue Dumble gooooop.

I think the LNFB is what gives the #102/124 that really clean pure tone, and also with the JM amp too. A simple mod for any ODS and I really like the sound of it if you want clean clean

IMG_20191202_183119.jpg

IMG_20191202_143341.jpg

M

[Guy77]

I am also a big fan of the LNFB. Whenever I put it on a switch for a 102 or a 124 or the JM always end up keeping it engaged all the time.
BTW what type of shielded cable are you using and where do you get it?

Amp looks great Marcus!

Cheers
Guy

[norburybrook]

I am also a big fan of the LNFB. Whenever I put it on a switch for a 102 or a 124 or the JM always end up keeping it engaged all the time.
BTW what type of shielded cable are you using and where do you get it?

Amp looks great Marcus!

Cheers
Guy

Guy,

It's just bog standard RG59 mini 75 ohm video coax , something like this

https://www.ebay.co.uk/itm/CABLE-COAXIA ... 0005.m1851



I Like it because the centre core is a nice chunky weight of solid copper. Some of the other shielded cables I've used had very thin stranded inner core.



M

[talbany]

and......today's tweaks......

Fitted an switchable LNFB circuit with some lovely NOS Pihers, complete with blue Dumble gooooop.

I think the LNFB is what gives the #102/124 that really clean pure tone, and also with the JM amp too. A simple mod for any ODS and I really like the sound of it if you want clean clean

IMG_20191202_183119.jpg
IMG_20191202_143341.jpg

M

Marcus
Just so you know the bigger 1 Watt Pihers sound different than the 1/2 watters do!. A couple scattered around the amp can help smooth out the sound however if you use too many of them they can kill the top end. Notice Dumble only used them in a few key spots (OD section) but never loaded up on the 1 watters in the clean section. Just sayin
BTW. It looks like you forgot to solder the top lug of your NFB switch on the back. I don't see any solder there?? or is that a N/C
Tony

[norburybrook]

and......today's tweaks......

Fitted an switchable LNFB circuit with some lovely NOS Pihers, complete with blue Dumble gooooop.

I think the LNFB is what gives the #102/124 that really clean pure tone, and also with the JM amp too. A simple mod for any ODS and I really like the sound of it if you want clean clean

IMG_20191202_183119.jpg
IMG_20191202_143341.jpg

M

Marcus
Just so you know the bigger 1 Watt Pihers sound different than the 1/2 watters do!. A couple scattered around the amp can help smooth out the sound however if you use too many of them they can kill the top end. Notice Dumble only used them in a few key spots (OD section) but never loaded up on the 1 watters in the clean section. Just sayin
BTW. It looks like you forgot to solder the top lug of your NFB switch on the back. I don't see any solder there?? or is that a N/C
Tony

Tony,

yes, I get that regarding the 1w Pihers I had 10 of them so thought I'd use them for the LNFB and see how they sounded. They sound great The SPDT switch is only connected at one side as it just breaks the loop. I've always wired them this way.....am I doing it wrong?


M

[Charlie Wilson]

I am also a big fan of the LNFB. Whenever I put it on a switch for a 102 or a 124 or the JM always end up keeping it engaged all the time.
BTW what type of shielded cable are you using and where do you get it?

Amp looks great Marcus!

Cheers
Guy

Guy,

It's just bog standard RG59 mini 75 ohm video coax , something like this

https://www.ebay.co.uk/itm/CABLE-COAXIA ... 0005.m1851


I Like it because the centre core is a nice chunky weight of solid copper. Some of the other shielded cables I've used had very thin stranded inner core.



M

Copper coated steel.
CW

[talbany]

I am also a big fan of the LNFB. Whenever I put it on a switch for a 102 or a 124 or the JM always end up keeping it engaged all the time.
BTW what type of shielded cable are you using and where do you get it?

Amp looks great Marcus!

Cheers
Guy

Guy,

It's just bog standard RG59 mini 75 ohm video coax , something like this

https://www.ebay.co.uk/itm/CABLE-COAXIA ... 0005.m1851


I Like it because the centre core is a nice chunky weight of solid copper. Some of the other shielded cables I've used had very thin stranded inner core.



M

Copper coated steel.
CW

CW
Is this coax comparable to RGU/59 Dumble used and can you solder to the jacket or is it aluminum?

Tony

[norburybrook]

I am also a big fan of the LNFB. Whenever I put it on a switch for a 102 or a 124 or the JM always end up keeping it engaged all the time.
BTW what type of shielded cable are you using and where do you get it?

Amp looks great Marcus!

Cheers
Guy

Guy,

It's just bog standard RG59 mini 75 ohm video coax , something like this

https://www.ebay.co.uk/itm/CABLE-COAXIA ... 0005.m1851


I Like it because the centre core is a nice chunky weight of solid copper. Some of the other shielded cables I've used had very thin stranded inner core.



M

Copper coated steel.
CW

Charlie, I'm not sure mine is coated steel. I'll have a close look tomorrow as I can cut a piece and look at the cross section. I see that the link I sent is coated steel, not sure if that's exactly the same as mine. As I said I'll check.

Would that affect things in any way of it were steel?

@Tony, there is a foil and a braided shield so you could solder the shield to a pot if you've got the technique....I've never managed to be able to do that so it looks nice, I've taken to wiring it separately to the bus bar. It solders fine like this.


M

[Charlie Wilson]

Yeah, and that is the question. Is that early Tandy RG59 and even earlier Columbia Coax used by Dumble solid copper conductor or coated steel? I have some Tandy from the 90s and it is coated steel. Typically RF frequencies will mostly travel on the outside of the wire and the steel core is stronger, so it is a better choice for its intended use but what about audio frequencies? The coax Marcus used has a braided shield over an aluminum shield, so I guess you could solder it to the back of the pots but it is still pretty thick, so running the drain wire to a buss bar would be easier. Marcus, if you have a magnet it won't stick to solid copper.
CW

[norburybrook]

Yeah, and that is the question. Is that early Tandy RG59 and even earlier Columbia Coax used by Dumble solid copper conductor or coated steel? I have some Tandy from the 90s and it is coated steel. Typically RF frequencies will mostly travel on the outside of the wire and the steel core is stronger, so it is a better choice for its intended use but what about audio frequencies? The coax Marcus used has a braided shield over an aluminum shield, so I guess you could solder it to the back of the pots but it is still pretty thick, so running the drain wire to a buss bar would be easier. Marcus, if you have a magnet it won't stick to solid copper.
CW

magnet? of course

M

[Guy77]

Thanks for the update Marcus. I just recently started using rg188a/u that also has the braided steel shielding like yours. I also connect the braided shielding to the bus bar. Its easier than trying to connect it to the back of the pots.

I like it because the core wire is 25 awg and nice and sturdy and outer diam. is less than 3mm.

Cheers
Guy

[talbany]

Gottcha! Thanks guys'
If the coax has a solid core I generally like to go right to the buss bar. However if it's a thin stranded core like 188 I generally like to solder it to the pot casting for the added stability. Both ways seem to sound and perform the same to me. To the buss bar is a little more work and time involved than it takes me to go directly to the back of the pot. This next build I think I want to try some RGU/59 and see if it sweetens things up a bit for the hell of it!

Tony

[norburybrook]

Quick question:

If I put my pair of Black plate 6L6's into my amp as I've got 1.5k screen resistors opposed to 470R, will that affect the sound ? I'm just curious to how the amp would sound with 6L6's , will a quick swap without changing the resistors be an accurate representation? Obviously I'd re bias.



M

[martin manning]

I'd give it a try. Of course there will be some difference going from 470 to 1k5 Rg2, but I think you will still get the pentode/beam tetrode flavor difference. I have 1k screens in my ODS with =C= 6L6 and It sounds great.