6V6GT Single-Ended Project

[shooter]

Do you own climbing gear?

 

[kagliostro]

I'll begin to try with the values that are more close ...... then, if necessary adjust

Franco

[kagliostro]

Ciao David

BTW: Saturday I was at an Ham Fest and I meet my hungarian radio amateur friend Gyula

His father was engaged for long years on repair military russian apparatus so he knows very well russian tubes

I asked him about the 6Ж8 tube (to know if there are special designation military versions like many other tubes as 6p14 or 6n2p that has an EV suffix or other to specify if the tube is in a version with special performance ) and he told me all 6Ж8 are military version, this seems to be a good thing and standard construction will be way more better than for civil use)

I stop here, I don't want to highjack the thread

Franco

[dwinstonwood]

Thanks Franco. I searched the auction site and there are several NOS 6Ж8's for sale from Ukraine at very good prices. Thanks for the info on that tube.

So, I have a question about the primary connections with a single-ended OPT. Does it matter which lead goes to the power tube plate and which one connects to B+? I'm using NFB with this amp.

Here's the schematic for my OPT. It shows a phase dot for the red wire - which corresponds to the phase dot on the secondary black ground lead.
But, the primary labeling doesn't make sense to me. It seems to say the red wire goes to the plate (PLT) and the 7K blue wire goes to the screen (SCRN). I'm not connecting my OPT to the power tube screen.

I was going to connect the red wire to B+ and the blue wire to the plate. Should I reverse that, or does it matter with single-ended OPT's?

Thanks!

[kagliostro]

The screen is to be connected if you want an UL Power Section, elsewere, dont connect it

The answer to your question is ... I don't know, but I know for sure that if you have an NFB connection you can income on squeal but it is very easy to be solved, reverse the B+ and Plate connections and all is done

Franco


p.s.: At DIYItalia we are developing an SE with secret  NFB 
you can see something here attached

[Willabe]

Here's the schematic for my OPT. It shows a phase dot for the red wire - which corresponds to the phase dot on the secondary black ground lead.

Who's OT is that? And what model number?

[dwinstonwood]

Who's OT is that? And what model number?

Willabe, it's the Musical Power Supplies OT10SE:
https://www.musicalpowersupplies.com/products/

But, I found another diagram on their site for the OT10SE that answers my question.

[Willabe]

They have that drawing upside down.

[dwinstonwood]

OK, I did Merlin's pentode math a third time, and I think I finally got it right. At any rate, I have a better understanding of how pentodes operate. And, instead of just copying other values (nothing wrong with that), I have a basic idea of what different values will do.

With a B+ of about 225V, I should have close to 140V on the Plate, around 62V on the Screen, a Cathode voltage of about 1.8V, and a Gain of something like 77.

Here're the resistor values I'm using:

Plate - 47K Ohms
Screen - 330K Ohms
Cathode - 820 Ohms

[dwinstonwood]

I think I have all the parts installed. I'll wire up the tube sockets in the morning. I'm going to wire the heaters Fender-style from above.

[bmccowan]

Too clean, mate - it'll never sound funky

[shooter]

he's been binge-studying Slukey's layouts
 
the funk comes from the heart n fingers, the amp simply provides spice

[dwinstonwood]

Well, if there's funky mojo in this, I can buy some more wire and try to clone it!

[bmccowan]

Which Gibson is that?

[dwinstonwood]

Which Gibson is that?

he's been binge-studying Slukey's layouts

Yeah, he set the standard that I've been trying to aim for since joining this forum. Here's mine:

[kagliostro]

Wunderbar, meine Herren!   

David, you know I'll stolen your job  (and use it with russian tubes or a mix)

Nice Layout, very neat 

Franco

[dwinstonwood]

Thanks Franco! "Stealing" would be the best compliment.

I caught my first mistake. I had the power tube bypass cap backwards. Fixed.

[Willabe]

Finely somebody got the B+ A node grounding correct!!!!!      PT B+ CT directly to the A node cap ground lug by themselves. Then a wire run over to the rest of the B+ ground daisy chain.

Edit, see reply 70;

A few problems;

1. I'd change the power tube section chassis ground from where it is now, see below. 

2. 60uF for the B+ A node might eat 5Y3 rectifier tubes. That's a lot uF's for a 5Y3, will draw too much current through 5Y3 at start up to charge the caps. Maybe you get away with it, will depend on how much resistance is in the PT's B+ wind.

3. And that's a SE amp, it will hummm with the B+ filter supply like you have it. PP amps have much better power supply noise rejection that SE amps don't have because PP cancels noise. To fix this, you need to add 1 more filter stage node before what you have now. 

So, you can kill 2 birds with 1 stone here.

Use that 1st 30uF cap by itself and leave the PT's CT tied to that 1st caps ground lug. Now put a 470 ohm R as a dropping R from the 1st 30uF cap, A node, to the 2nd 30uF cap, B node. Use the 2nd 30uF cap, B node for the OT B+ feed. And leave the ground lug wire from A node cap to B node cap. BUT, now take the power tube chassis ground from B nodes ground lug. This will greatly reduce the power supply hummm.

Last thing, you might not want to use all 30uF B+ filter caps, for a SE 6V6. Some guys find an amp more touch sensitive with the last or last 2 B+ filter caps of only 8uF or 10uF.

[shooter]

"Stealing" would be the best compliment.

Not sure that Steve agreed when I stole from him 

[kagliostro]

OK, Willabe is right, there are some improvements to be made, but overall the layout is very very clean, any build will benefit from this footprint.

On DIYItalia we prefer to use a gyrator on the PS but also old school tricks can solve the SE Humm problems, we also discard the use of Vacuum Rectifiers especially on SE

Franco

[dwinstonwood]

Thanks Willabe!

I'm not sure I follow/understand your recommendations. I thought that having the Choke between the reservoir and A node would isolate the first cap as a single 30uF reservoir cap. I'm not sure where to place a 470 Ohm resistor... before or after the choke, or does it matter? I used this same basic power supply in my AC4 and there is practically zero hum.

Here is the schematic of this amp's power supply. The first 30uF is not a B+ node. A node goes to the OPT, and B node goes through a 470R to the 6V6 screen.

[Willabe]

I'm not sure I follow/understand your recommendations. I thought that having the Choke between the A and B nodes would isolate the A node as a single 30uF reservoir cap. I'm not sure where to place a 470 Ohm resistor... before or after the choke, or does it matter? I used this same basic power supply in my AC4 and there is practically zero hum.

Here is the schematic of this amp's power supply. The first 30uF is not a B+ node. A node goes to the OPT, and B node goes through a 470R to the 6V6 screen.

I missed that, your fine then.

I've never seen the chassis grounding the way you've done it, but I think that will work.

But;

....... you might not want to use all 30uF B+ filter caps, for a SE 6V6. Some guys find an amp more touch sensitive with the last or last 2 B+ filter caps of only 8uF or 10uF.

You have 6 @ 30uf = 180uF total B+ filter supply, that's a lot in a SE with a 5Y3 rectifier tube.

[dwinstonwood]

I've never seen the chassis grounding the way you've done it, but I think that will work.

Thanks Willabe. I've used this grounding method on my last four amps. Other than the PT center tap and reservoir ground lug, which is close to both and makes a small chassis ground circuit away from the rest of the amp, everything else is grounded at the input jack. It has worked really well for me, so I've been sticking with it.

But;
....... you might not want to use all 30uF B+ filter caps, for a SE 6V6. Some guys find an amp more touch sensitive with the last or last 2 B+ filter caps of only 8uF or 10uF.

Thanks, I have plenty of smaller caps I can try. The reason I did use all 30uF's is because I'm going with a "Star" B+ network. Each stage has its own dropping resistor and capacitor, i.e., the filter caps are not in series. This is supposed to provide better decoupling between stages. But, it's easy enough to swap in smaller caps.

David

[Willabe]

I've never seen the chassis grounding the way you've done it, but I think that will work.

I've used this grounding method on my last four amps. Other than the PT center tap and reservoir ground lug, which is close to both and makes a small chassis ground circuit away from the rest of the amp, everything else is grounded at the input jack.

What I meant was that a lot of guys use 2 circuit chassis grounds, 1 power amp ground, 2 preamp. (If amp has -FB, PI goes to power amp ground, if no -FB PI gets grounded with preamp.)

But this is a SE amp, so you put in 1 extra filter stage before the normal B+ filter daisy chain.

I saw that you ran that 1st B+ cap's ground to the chassis along with the PT's B+ CT.

But, really you should run the PT B+ CT directly to the 1st B+ filter cap then run a wire to the rest of the daisy chained star B+ filter cap nodes. This way the PT's B+ CT and filter cap can charge/drain in a small loop with nothing else in that loop. And this keeps that filter caps charging pulses current off of the chassis. So they don't interact with any other grounds.

That's the dirtiest, nosiest ground in the amp.   

Those 2 ways of wiring it are very close but have a slight difference, the cap/CT grounds and the chassis connection. And those 2 differences matter. 

That's what I meant by I guess it will work. Because the other chassis ground is so far away from the 1st filter cap/PT CT chassis ground.

But;
....... you might not want to use all 30uF B+ filter caps, for a SE 6V6. Some guys find an amp more touch sensitive with the last or last 2 B+ filter caps of only 8uF or 10uF.

Thanks, I have plenty of smaller caps I can try. The reason I did use all 30uF's is because I'm going with a "Star" B+ network. Each stage has its own dropping resistor and capacitor, i.e., the filter caps are not in series. This is supposed to provide better decoupling between stages. But, it's easy enough to swap in smaller caps.

I missed that you wired the last 4 filter caps in || (parallel). I saw in the layout drawing that you were going for ground stars.

......because I'm going with a "Star" B+ network. Each stage has its own dropping resistor and capacitor, i.e., the filter caps are not in series. This is supposed to provide better decoupling between stages.

I've never heard or have read that. I see no reason why it would be better. If it was better, most amp makers would have done that all through the years.

You can just run those caps in series to use a daisy chained wired ground star system. And you'll get better filtering, and can use smaller caps, if you run the filter caps in a series daisy chain.

Filter cap/dropping R/filter cap/dropping R/filter cap/dropping R, etc.

[kagliostro]

Ciao David

About the kind of PS with filters in Parallel or In Series I can say that some VOX used the Parallel Arrangement and that this way the voltage are more stiff at any node

To achieve a similar performance in some PP amp I've seen PS that some plan used a diode between the PS  Power Section and the PS Preamp section to avoid the draining of the PS Preamp capacitors at the moment of transient that increase the consumption on the Power Section Nodes, but I don't think this is the case to have such a problem, on SE amp the current consumption don't vary so much

On this matter (Parallel or In Series Nodes on PS) I've read on the past explanations about the opportunity to use the one or the other but .... my mind is not efficient like in past and now I don't remember those precious info's

----

About the 30uf + Choke + 30uf on the PS a doubt come to me, as Willabe told, to avoid problems on the 5y3 (first capacitor ability excess) you can use a pre first Node A CR filter, it is true that a choke has a resistance, so your approach is similar but ..... a choke is also an energy storage element, the doubt is .... in this arrangement don't the choke will act as a Cap and his charge don't will stress the Vacuum Rectifier 

I really don't know, I hope someone can clarify this situation

Franco

[SEL49]

@dwinstonwood, your power supply is fine just as drawn. No danger to the 5Y3. And the parallel power supply nodes offer one big advantage over the series string nodes. You can dial in the voltage of one node without affecting the voltage on another node. Makes it easy when building a one-of-a-kind amp. Matchless is very fond of parallel nodes in most all of their amps.

@kagliostro, a filter cap opposes a change in voltage (smooths the voltage ripple and spikes). A choke opposes a change in current (smooths current ripple and spikes). Using a CLC filter between the rectifier and plate node greatly decreases hum (especially important in a SE amp). In addition, the choke reduces the current charging strain on the rectifier, similar to the effect of using a series resistor but without the voltage drop of the resistor.

[dwinstonwood]

Thank you SEL49. It's a grounding scheme that has worked well for me on other amps. And, yes, the ability to select individual node voltages was, in fact, another reason I went with series filtering - in addition to better decoupling. I'm using some less-common tubes (that I've never used before), and wanted the freedom to set each one up independently, if needed. 

I did make one grounding change. Originally, I wasn't going to use NFB, and had grounded the speaker with the power supply. But, since I did go with NFB I've now grounded the speaker at the ground star-point with the tube where the NFB is injected.

David

[Willabe]

And the parallel power supply nodes offer one big advantage over the series string nodes. You can dial in the voltage of one node without affecting the voltage on another node. Makes it easy when building a one-of-a-kind amp. Matchless is very fond of parallel nodes in most all of their amps.

1st off, Matchless amps builder was a Vox guy, so yeah, he's used to running || B+ filter string.

And that's true, you can dial in a dcv a little easier with a || filter string, but it's not all that much easier. Use ohms law to try and figure dcv drop to get close and just gator cable clip in the dropping R to test, not so bad.

But a series string has pluses over a || string, it gives better filtering as you go down the string line and you can use smaller value, less chassis space, and cheaper caps as you go down the line, and still get great decoupling/filtering.

Other than starting with a low B+ dcv, like with EL84 amps, It's not really needed in most cases.
 
You can easily get great decoupling with a series filter string. With a series string the larger the cap and/or the larger value the dropping R, the better the decoupling. As you go down the string to the preamp tubes, they draw much less current, so you can use much larger dropping R's for better decoupling without much, if any voltage drop penalty.

[Willabe]

- in addition to better decoupling.

What are you basing this on?

You've said this twice now with no reasoning/explanation, or link to where you've heard/read this.

You can use either || or series that's fine, but I'd like to see where you are getting that || string offers better decoupling. I don't want to mislead members here with something like this if it's not true and then start newer builders all going to || filter cap strings.

You can easily get great decoupling with a series filter string. So I don't know why anyone would say that a || filter string has better decoupling than a series filter string.

And that's true, you can dial in a dcv a little easier with a || filter string, but it's not all that much easier. Use ohms law to try and figure dcv drop to get close and just gator cable clip in the dropping R to test, not so bad.

With a series string the larger the cap and/or the larger value the dropping R, the better the decoupling. As you go down the string to the preamp tubes, they draw much less current, 1mA/2mA, so you can use much larger dropping R's for better decoupling without much, if any voltage drop penalty.

[Willabe]

About the kind of PS with filters in Parallel or In Series I can say that some VOX used the Parallel Arrangement ....

Vox had to use the || string to keep the preamp tubes plate dcv up. Because they were using EL84 power tubes, they started with a pretty low B+ dcv. So to keep the preamp tubes dcv up as best they could, they had to use a || B+ filter string.

[DummyLoad]

About the kind of PS with filters in Parallel or In Series I can say that some VOX used the Parallel Arrangement ....

So does/did Matchless, even with the Clubman which employs EL34s running with 430V B+. 


--Pete

[Willabe]

About the kind of PS with filters in Parallel or In Series I can say that some VOX used the Parallel Arrangement ....

So does/did Matchless, even with the Clubman which employs EL34s running with 430V B+.

Sure, the guy who started the company cut his teeth on Vox AC30's, he's a Vox guy. He's used to doing || filter strings.

[dwinstonwood]

In the end, this is a hobby for me. So, I'm keeping it fun.

I don't think this needs saying, but for the record, I'm really not advocating; I'm not trying to encourage anyone to use parallel B+ strings, or to use preamp tubes other than 12A_7's. It's a project, and I just always learn more by experimenting.

The whole point of this project from the beginning was to dive into stuff I hadn't done before on my clone builds. Even if the end product is dismal, I'll have had a great time and learned a ton!

David

[Merlin]

Vox had to use the || string to keep the preamp tubes plate dcv up.

This is not really true, it's not hard to keep the DC voltage plenty high, whatever arrangement is used. I think it was more for convenience of layout.

I've never heard or have read that. I see no reason why it would be better. If it was better, most amp makers would have done that all through the years.

Series string provides better smoothing of rectifier ripple, parallel provides better decoupling between valves. Different concepts. Which one is more important? There's no right answer, but it a guitar amp we usually care more about hum (ripple), whereas a hi-fi amp might prioritise decoupling to improve LF harmonic distortion and crosstalk. The distinction is less important in modern times because we can buy large capacitances very cheaply.

[bmccowan]

In the end, this is a hobby for me. So, I'm keeping it fun.

I don't think this needs saying, but for the record, I'm really not advocating; I'm not trying to encourage anyone to use parallel B+ strings, or to use preamp tubes other than 12A_7's. It's a project, and I just always learn more by experimenting.

The whole point of this project from the beginning was to dive into stuff I hadn't done before on my clone builds. Even if the end product is dismal, I'll have had a great time and learned a ton!

David

Well stated David. For those of us that are in this as hobbyists, its the process that is the point. I learned how to not electrocute myself (so far) and then it was off to the races. I, and the collective we, are fortunate to not need to make a profit, and not need to meet a client's expectations. Not everyone is in that situation and I get and respect that.
Enjoy the ride.

[Willabe]

Vox had to use the || string to keep the preamp tubes plate dcv up.

This is not really true, it's not hard to keep the DC voltage plenty high, whatever arrangement is used. I think it was more for convenience of layout.

That could be, they had 2 chassis on those AC30's, I don't know about the AC15's if they also had 2 chassis?

But I still think by using EL84's Vox on those amps started out with a fairly low B+. I don't see many of the AC30/AC15' schematics with dcv's. But this older AC15 starts out with 315dcv for B+. Doesn't leave a lot of room for B+ string dropping R's by the time you get to the 1st triode and it's plate R not much dcv left. Will a triode work with only ~90 to 100dcv, sure, but it will sound different than it had 150/200/250 on it.

This AC15 schematic shows a few dcv's. B+ starts with 315dcv, and at the Vib/Trem channel, the 1st triode, V1, 12AX7, shows 210dcv before the 150K plate R. So that could be down to ~100dcv on that plate? And the normal channel's 1st gain stages plate, EF86, only has 90dcv on it. EF86 spec sheet says it'll handle 250dcv on the plate. So Vox could have left that higher.

https://el34world.com/charts/Schematics/files/Vox/Vox_ac15.pdf

I've never heard or have read that. I see no reason why it would be better. If it was better, most amp makers would have done that all through the years.

Series string provides better smoothing of rectifier ripple, parallel provides better decoupling between valves. Different concepts. Which one is more important? There's no right answer, but it a guitar amp we usually care more about hum (ripple), whereas a hi-fi amp might prioritise decoupling to improve LF harmonic distortion and crosstalk. The distinction is less important in modern times because we can buy large capacitances very cheaply.

Ok, but why does parallel provides better decoupling between valves? 
We need to know the reason(s), can't learn anything if you don't explain a little bit of why.

On that AC15, both channels last B+ dropping R is 22K. Seems like that's how their getting some increase in the decoupling.

With a series string, the larger the cap and/or the larger value the dropping R, the better the decoupling. As you go down the string to the preamp tubes, they draw much less current, 1mA/2mA, so you can use much larger dropping R's for better decoupling without much, if any voltage drop penalty.

So using larger dropping R's as the string goes down to the 1st triode, why wouldn't that give as good of decoupling as a || B+ string? 

[Merlin]

But I still think by using EL84's Vox on those amps started out with a fairly low B+.

Dropping from 300V down to 250V leaves plenty of room for a series string IMO. Marshall used a series string for the 18W which also starts with ~300V.

Ok, but why does parallel provides better decoupling between valves? 

In the image below you can see how the two triodes are separated by 20k in parallel case, but only 10k in the series case. So for the same values, parallel offers better decoupling (isolation between stages). But the series case offers better smoothing for the second triode.

[kagliostro]

Please, Merlin, can you say your opinion on the practice I've seen in some (DIY) project to add an in series diode in a series PS between the preamp node and the power amp node, obviously the idea is to prevent the preamp node capacitor/s from being dried by the power section during transient, but ... will be it really useful ?

Many Thanks

Franco

[dwinstonwood]

I've taken basic DC voltage readings.

6V6GT:
Plate - 325.5
Plate > cathode - 311
Screen - 246.4
Across Rk - 13
Dissipation - 10.8W; 77%
Plate Current - 34.7mA

I designed for about 330 on the Plate and 250 on the Screen. I'm close.
I need to go down to a 300-ish Ohm Rk to get the dissipation up.

6SF5GT:
Plate - 161
Cathode - 1.222

5693:
Plate - 139
Screen - 66.8
Cathode - 1.894

I did the design math for 140 on the Plate, 62 on the Screen, and 1.8 at the Cathode. Pretty close.

6SL7:
Cathode Follower
Grid pin 1 - 136.7
Plate pin 2 - 231.4
Cathode pin 3 - 136.3

Driver
Plate pin 5 - 137.2
Cathode pin 6 - 1.28

These all look good to me. Next step... switch from dummy load to speaker and plug in a guitar.

[dwinstonwood]

Wow! I need to back way off on the voltage dividers I added. You all had me scared that this thing would be a howling beast, so I really chopped down the voltage.

With the Gain and the Volume knobs on 8 it is quiet but very clean, no distortion.

Speaking of quiet, there's no audible hum or hiss two feet away. I had a friend put his ear close to the speaker, and he didn't hear anything, either.

I'll dial back the dividers to 220K/220K and swap in a 300 Ohm cathode resistor and see where that gets me.

Otherwise, everything is functioning the way it should!

David

[shooter]

and swap in a 300 Ohm cathode resistor

take the 100uF Ck down to ~~47uF as long as you're reworking it.


i've found 100uf takes out some "mojo"


drop your Rk slowly 270, 250, 220.  Gator clips work if you're cautious
you'll find there's a "sweet spot" that gives you enough good distortion before you reach ugly sounds.
you'll wanna tweak the B+ tap to keep plate VDC up as you suck more current.

[Merlin]

Please, Merlin, can you say your opinion on the practice I've seen in some (DIY) project to add an in series diode in a series PS between the preamp node and the power amp node, obviously the idea is to prevent the preamp node capacitor/s from being dried by the power section during transient, but ... will be it really useful ?

I don't think it's useful in a guitar amp. It's more helpful in a hi-fi amp playing classical music, where it's mostly quiet but with the occasional very loud, very short interrupt, like a kettle drum or gong.

[Willabe]

Ok, but why does parallel provides better decoupling between valves? 

In the image below you can see how the two triodes are separated by 20k in parallel case, but only 10k in the series case. So for the same values, parallel offers better decoupling (isolation between stages). But the series case offers better smoothing for the second triode.

Thank you, I can see it now.

I should have seen that, I was thinking it was something more complicated. That's why I couldn't see it. 

Guess it comes down too how much smoothing and how much decoupling is enough. Seems to be some room to adjust, as long as you don't go to extremes, to get enough of both with either a series string or running them in || for them both to be pretty close in both smoothing and decoupling. 

[Willabe]

and swap in a 300 Ohm cathode resistor

take the 100uF Ck down to ~~47uF as long as you're reworking it.

i've found 100uf takes out some "mojo"

drop your Rk slowly 270, 250, 220.  Gator clips work if you're cautious
you'll find there's a "sweet spot" that gives you enough good distortion before you reach ugly sounds.
you'll wanna tweak the B+ tap to keep plate VDC up as you suck more current.

And the 6V6 screen dcv is holding back some volume. I'd raise it up much closer to the plate dcv.

There's a few Fender SE that have the screens the same as the plate. And few amps that the screen dcv is a little higher than the plate dcv, can't remember if they were guys builds here or Fender or someone. 

[shooter]

SE that have the screens the same as the plate.

one of the reasons I moved to UL OT's, the voltage stays close to plate while opposing fast current changes.
I've always run my xSE with minimal G2 "protection"; typically ~100 ohm R with a wattage rating to smoke before the tube.

[dwinstonwood]

Thanks Willabe! I had already switched the power Rk to a 25uF/50V.

All I have on hand are 330 and 270 Ohm 5W resistors. With the 330 (329.4 actual) it's getting there:
Plate - 325.5
Plate to Cathode - 311.2
Screen - 246.8
Across Rk - 12.85

Dissipation - 11.5W, 82%
36.9mA

I will follow your advice shooter and step down until I'm just at 100% - maybe a tad less.

Part of the plan for this project was to set the Screen up at 250V. Most of this project was about trying things I haven't done before.

I switched to 220K/220K 50% voltage dividers and it made a world of difference. With the input Gain dimed and the post-tone stack Volume on 4 it has some good distortion. With the input Gain on 4 and the Volume on 8 it's clean but not too bright. I happy with it!

Sorry for the poor lighting. It's already dark on the East Coast.

[bmccowan]

Wow! I need to back way off on the voltage dividers I added. You all had me scared that this thing would be a howling beast, so I really chopped down the voltage.

Guilty, yes I'm guilty
And I'll be guilty the rest of my life Randy Newman
Congrats on a great project - and hey, doesn't that red 5693 look great on the chassis?!
Have a great Thanksgiving, all.

[dwinstonwood]

Guilty, yes I'm guilty
And I'll be guilty the rest of my life Randy Newman
Congrats on a great project - and hey, doesn't that red 5693 look great on the chassis?!
Have a great Thanksgiving, all.

Hey, you weren't the only one here saying this was going to be a death metal animal. With no dividers at all it probably would be uncontrollable.
And, yeah! I love that red metal 5693 with the cool vintage RCA logo on top. Thanks to HBP for recommending that one.

Also, the James tonestack (first one I've used) is cool. Turning the Treble and Bass up in unison brings in the Mid-scoop and boosts gain a bit at the same time.

Have a great holiday!

[kagliostro]

Very cool David

Many thanks for the answer Merlin

Franco

[dwinstonwood]

Thanks Franco. And, I also need to thank Merlin. I copied a lot out of his books for this project.

Tomorrow I might try a GZ34, instead of the 5Y3GT, just to see if I can even tell a difference with higher voltages. But, I like it the way it is with all NOS (and inexpensive) tubes.

David