2nd Gen hybrid

[Bombacaototal]

Hi Erwin, thanks for the detailed post. Amazing collection of NOS parts, I bet it sounds amazing. I am building mine with Piher carbon(1w or 2w), dale rb65d for the plates and mepco mf7c for the cathodes. Cannot wait to hear it in action

Noted with thanks regarding the upgrades on the normal 2nd gen and hence the hybrid denomination

Regarding you comment on the #102 upgrade did you leave the 150k slope and 250k middle pot jist changing the mid capacitor to .05uf? Regarding the LNfB, when on clean, removing it, did you add the 56k grid stopper?

Still troubleshooting, finetuning will start when that's done. First thing for finetuning to try is lowering the 1m resistor after v2b.
On #102: only change the mid cap. The lnfb doesnt alter the grid resistor 220k//500pF so I cant follow your thoughts on this.

Ah yes of course, apologies for the mistake. I will give this idea a try and maybe also try 100k slope instead of 150k

[erwin_ve]

Sorted out the malfunctioning of the FET circuit; the 2N4416A was soldered too hot I think, replaced it with a new one.
Voila it's working!
All three footswitch functions are working and while playing it, more and more it seems a Swiss army knife to me, what a super versatile amp!
I really like it lot.
Next step; figuring out why the jazz side of the switch is acting like a PAB.

[ToneMerc]

Sorted out the malfunctioning of the FET circuit; the 2N4416A was soldered too hot I think, replaced it with a new one.
Voila it's working!
All three footswitch functions are working and while playing it, more and more it seems a Swiss army knife to me, what a super versatile amp!
I really like it lot.
Next step; figuring out why the jazz side of the switch is acting like a PAB.

Are you using an on/on or on/off/on switch? I wire the on/on like #183, but if you want the R/J to act as a front panel PAB switch in the mid position use a on/off/on and wire it like #124.

TM

[erwin_ve]

Are you using an on/on or on/off/on switch? I wire the on/on like #183, but if you want the R/J to act as a front panel PAB switch in the mid position use a on/off/on and wire it like #124.

TM

I'm using it as on-on switch. Thanks for your suggestion, will look into it asap!

[Bombacaototal]

Yes I have built several amps. Multiple: #102, hrm, blues master without the hrm stack and a few dumblelators.
Wether you like a amp with a strat is based on personal taste. I think any of the amps I mentioned is suitable for a strat, some need maybe a small modification; fe. #102 with a 0.05 mid cap and a switchable lnfb (only lnfb when od is engaged) is imo very suitable for strat.

Erwin

Just one curiosity, why do you prefer the sound without the LNFB for cleans for strat? Less compressed and more dynamic?
I also read around the forum that going low plate will also help the skyliner to become more strat friendly

[erwin_ve]

[

Just one curiosity, why do you prefer the sound without the LNFB for cleans for strat? Less compressed and more dynamic?
I also read around the forum that going low plate will also help the skyliner to become more strat friendly

The lnfb acts as a attenuator for the triode affecting certain frequencies; the resistors and cap for the lnfb are chosen in such a way that you loose a little top end. This also affects the sound for the overdrive and it will be more smooth. Downside is losing sparkle on the clean.
For a better understanding of negative feedback this is a nice read: https://archive.org/details/HighFidelityCircuitDesign

[Bombacaototal]

[

Just one curiosity, why do you prefer the sound without the LNFB for cleans for strat? Less compressed and more dynamic?
I also read around the forum that going low plate will also help the skyliner to become more strat friendly

The lnfb acts as a attenuator for the triode affecting certain frequencies; the resistors and cap for the lnfb are chosen in such a way that you loose a little top end. This also affects the sound for the overdrive and it will be more smooth. Downside is losing sparkle on the clean.
For a better understanding of negative feedback this is a nice read: https://archive.org/details/HighFidelityCircuitDesign

Thanks for the explanation and for the reference. Indeed very helpful

[erwin_ve]

The rock/jazz switch is fully functional now, as is the entire amp!
The wires coming from the pab board going to the center of the r/J switch were reversed.
(For anyone who uses the 2nd gen hybrid layout for there build: pay attention it has several errrors, the r/j switch amongst them!)

The loop is #124 style with 220k//250pF. And on the clean master I installed a 15pF cap.
Playing the amp with a dumblelator is sounding sweet, to come close to playing the amp without dumblelator, I engage the bright cap on the output pot on the dumblelator.

Next step: combo cabinet: snakeskin style tolex with a Fane Studio speaker!

[talbany]

Erwin
The build looks great!!
A few points of interest on this design I ended up tweaking on mine

1 ..The 1m bypass resistor on the OD network I lowered to 470k (Kittyhawk)..This struck a good balance of gain for me at the input volume setting I preferred as well as overall volume I would generally run the amp..
2...I just used the single .002 across the bass pot..This made for a smoother response of the bass control
3..With a 12AT in the PI I increased the NFB resistor (lowering the amount of feedback) again at the volume I ran on stage to open the amp up a bit.
4..I also tweaked the resistor to ground on V2b to keep things tight on the way out (I think 150k was what I used)

With these tweaks I never really missed the OD vol control to be honest..IMO the amp (in its original form) performs best at stage volumes (moderate to loud)
So my tweaks for me helps the amp perform better at slightly lower volumes for many of the venues as well as my guitars..(primary Single coils) but still works well with humbuckers

I actually prefer this OD circuit for Strats over the later 3rd generation amps..IMO the absence of the OD vol control plays a big role in why it sounds so good (big & fat dynamic)with single coils..YMMV

Good luck and hope this helps..

Tony

[erwin_ve]

Erwin
The build looks great!!
A few points of interest on this design I ended up tweaking on mine

1 ..The 1m bypass resistor on the OD network I lowered to 470k (Kittyhawk)..This struck a good balance of gain for me at the input volume setting I preferred as well as overall volume I would generally run the amp..
2...I just used the single .002 across the bass pot..This made for a smoother response of the bass control
3..With a 12AT in the PI I increased the NFB resistor (lowering the amount of feedback) again at the volume I ran on stage to open the amp up a bit.
4..I also tweaked the resistor to ground on V2b to keep things tight on the way out (I think 150k was what I used)

With these tweaks I never really missed the OD vol control to be honest..IMO the amp (in its original form) performs best at stage volumes (moderate to loud)
So my tweaks for me helps the amp perform better at slightly lower volumes for many of the venues as well as my guitars..(primary Single coils) but still works well with humbuckers

I actually prefer this OD circuit for Strats over the later 3rd generation amps..IMO the absence of the OD vol control plays a big role in why it sounds so good (big & fat dynamic)with single coils..YMMV

Good luck and hope this helps..

Tony

Tony!
You're right, the amp, with a strat, but also humbucker guitars sound also very good, still have to do a gig with it. The big surprise for me was the FET circuit (switchable!). In combination with the overdrive it is to die for.
Thanks for your input!
Gonna try all of your suggestions.
On the od entrance: I was thinking to use a 1m pot and wire the entrance to the middle lug. The output of the pot wired to the 33k/v2a grid resistor. Kind of a trigger control but different: what do you think?
The nfb resistor increase: did you do that for a 50 or 100w?
Do you think seperate masters are different soundwise? The od channel has a 1m master and doesnt see a second master volume.
Thanks! Erwin

[talbany]

Erwin
Yes mine is 100w!..6L6 fender Iron running around 400v on plates
The trigger on the OD sounds like a good idea and worth a try..Let me know how that works out for you
As far as the separate master on OD goes..I understand why dumble would put a pot after V2b to control the level of the OD..But then (in OD) you essentially have a pot feeding another pot and is IMO a tone sucker and a unavoidable flaw in the design again IMO,which is probably why he changed the design later with the HRM design..I find if you can tweak the OD entrance just right along with the input vol on clean channel I can control the overall volume with the ratio control to balance out the 2 channels at the volume I normally run and have never really missed the OD master..I believe because of the absence of a pot feeding another pot that the OD sounds fuller and more dynamic again IMO especially with single coils where the later designs with the OD master don't sound as good to me!!..So when you get the amp up and running set up the volume difference you like between the clean and OD then tweak the amount of gain you like with the trigger and you should be good to go!..Again you can always tweak the overall volume on the OD with the ratio control (which now becomes the OD master)..There you go you should be set!!
A few more things..The sweet spot for V1 is around 180..This thing sounds killer with some NOS RCA glass (pre and output)..Black Plate 6Ls are icing on the cake (Black plate short bottle TAD's are nice to)..Put a balance on the PI and run an AT there (2nd harmonics abound) and will help keep the OD nice and tight..tweak the NFB last after you have all of this done and your tubes of choice are happy..then Let it eat!!
I agree with the FET.. I use an RC booster on the front of mine so I can tweak the tone and vol on the fly and at my feet..Good luck and let me know how that works and if I can help further

Tony

[erwin_ve]

Thanks Tony!

No soldering this week, a bit busy with teaching/ rehearsing/ gig-ing.
Only did the logo on the amp.

[erwin_ve]

Combo cab came today. Made by Tubetown, they did a excellent job!
So this is the final look.

[Matt J]

The rock/jazz switch is fully functional now, as is the entire amp!
The wires coming from the pab board going to the center of the r/J switch were reversed.
(For anyone who uses the 2nd gen hybrid layout for there build: pay attention it has several errrors, the r/j switch amongst them!)

The loop is #124 style with 220k//250pF. And on the clean master I installed a 15pF cap.
Playing the amp with a dumblelator is sounding sweet, to come close to playing the amp without dumblelator, I engage the bright cap on the output pot on the dumblelator.

Next step: combo cabinet: snakeskin style tolex with a Fane Studio speaker!

Would this type of switching layout be useful even if you don't use the PAB option for the R/J control and just omitted the wires leading to the relay board, or would further modding be necessary? I'm thinking of trying this in my Small Special build since it has a control layout based on a 2nd/3rd gen preamp.

[erwin_ve]

Would this type of switching layout be useful even if you don't use the PAB option for the R/J control and just omitted the wires leading to the relay board, or would further modding be necessary? I'm thinking of trying this in my Small Special build since it has a control layout based on a 2nd/3rd gen preamp.

Maybe; if your wire the treble pot like #124 with a 22m resistor and the other half of the centre R/J switch connected to the middle lug with a 22m resistor.