A "Deluxe" Project: 5E3 / 6G3 amp project

[dr.barlo]

Hey guys,

Am thinking of building this amp (with the help of a friend of mine who'd be doing most of the "building"), and wanted your opinion...

• 2 channels, 4 inputs
• first channel is the "5e3" channel - has a volume and tone assigned
• second channel is the "6g3" channel, again has a volume and tone assigned
• there'd be lotsa switches... hehe
• one switch is to go back and forth between cathode bias and fixed bias
• another switch would be for selection 3 types of negative feedback resistors
• one setting is that it is off... the tweed ****
• another is the "brown" value
• and finally the last one would be the "blackface" value
• the amp would have both the presence and resonance in the back
• and it'd also have the vibrato thing, also hitting the 5e3 side...
• it'd be ~40W with 5881's (or 6L6s) or ~18-20W with JJ6V6's
• Am gonna use Hammond 370HX OT: 275-0-275V @ 200mA, powerful sucker
• am gonna use Heyboer TO40, the 4lbs version of the vibro ot from Allen Amps
• alpha pots
• mallory caps...
• gz34 rectifier

So what do you say? I really would appreciate the input.

I am sometimes thinking that I could go for the 6G11 (Vibro) for the second channel. But then again, the amp would be a bit more complicated and the presence and resonance should be giving me quite powerful controls anyway...

So it'd be able to do the 5e3 almost spot on (gz34 you know, not 5y3) ... Cathode bias & no negative feedback thing... And at the same time it'd do the 6g3 thingy right away... And there are some other in between things... like the 6G3 that is cathode biased, or fixed bias 5e3 with "blackface" negative feedback...

...

Am excited.

Any feedback?

B

 

[AlleeCat]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Sounds like an awesome idea!!! When can I place an order for one!!! Ha Ha!!!


AlleeCat

 

[jeremy]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

the presence wont work with the neg feedback switch in the tweed position, guessing you knew that.

i love both the 5e3 and the 6g3. actually use a ab763 every week

 

[Gypsyblue]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Ambitious! Good luck.

My concern would be with having created an expensive prototype that doesn't sound quite as good as I'd hoped and which after I'm done, I'd know I could do better the second or third time around.

Personally, I'd build either two completely separate amps or maybe just one that's much simpler.

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

the presence wont work with the neg feedback switch in the tweed position, guessing you knew that.

i love both the 5e3 and the 6g3. actually use a ab763 every week

Right on bro... The same here...

Yep, the presence and resonance would not work in the "tweed" setting, but going for a genuine tweed deluxe thing was the main concern to start with. I will be using a rotary switch and some additional cap values (on top of the "stock" value of 0.047uf) in order to keep "some" control, you know... The presence and resonance would be really useful with the 6G3 side. In fact, I also have sorta "blackface" version of the 6G3, but with the wrong plate voltage... Still am wondering how it would sound. Also, the tweed side with fixed bias and "blackface" negative feedback value is sorta giving me thoughts you kow...

Anyways, I hope I don't screw up ... Actually, that's primarily the reason of the thread you know... So far, so good...



I cannot stop thinking whether or not to go for the 6G11 (Vibro) preamp as opposed to 6G3... Then, instead of only vol/tone, I would have vol / bass / treble... But I already have the presence and resonance in that "brown" setting. So kinda think that I do not need the "bass & treble" controls... Anyways, am confused....

What do you say?

B

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Ambitious! Good luck.

My concern would be with having created an expensive prototype that doesn't sound quite as good as I'd hoped and which after I'm done, I'd know I could do better the second or third time around.

Personally, I'd build either two completely separate amps or maybe just one that's much simpler.

Thanks.

That is always the danger that one would run into when dealing with such kinda projects.

Then again, having checked the power amp structure of a 5E3 and 6G3 (basically the cathode bias vs fixed bias; and the levels of the negative feedback resistor), and being able to keep sorta the same plate voltage (~360-370V) that is kinda right for them amps, made me go for this project you know.

I dunno how the "in between" or better put "mixtures" would sound. For example, the sound from the 5e3 preamp with a fixed bias poweramp and the "blackface" level of negative feedback may suck big time... I dunno... It is just that, my current plan is already providing me with a genuine 5E3 position (with a GZ34 rectifier, and that is the only "off" thing) and a genuine 6G3 position.

See?

Would love to hear what you think of this.

Best,

B

 

[jeremy]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

im a big fan of the single tone control, i wouldnt bother with the treble/bass.

the gz34 is gonna tighten things up a lot compared to a 5y3 but i tend to run a 5v4 in my 5e3 much of the time anyway. its definitely different, the extra headroom and more low end focus is nice.

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Cool...

I am going with a oversized (4lbs) vibro ot from Allen Amps (basically wound to their specs by Heyboer custom shop). It is not a bassman ot, but close. It is sorta bassman ot made to fit into a vibro, you know... Just a bit smaller than a regular bassman ot I suppose.

... and am gonna go with JJ 6V6's. So @ a plate voltage like 360V, it'd be like 16 - 18W. But it'd have the thumb you know. And I always can go for 5881's or even EL34s... but not need that much power you know.

SO... that may be a bit different that a genuine 5e3 afterall. Then, mine would have a bit more headroom and more low end. In fact, I don't mind that...

B

 

[the guy who invented fire]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

2 of my fav Fender amps ever but I'm not sure that a hybrid design of both trying to get both sides of those tones will work.

Maybe??

Best of luck!

 

[jeremy]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

ive used that allen tranny and its good

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

ive used that allen tranny and its good

Cool!

B :cool2:

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

2 of my fav Fender amps ever but I'm not sure that a hybrid design of both trying to get both sides of those tones will work.

Maybe??

Best of luck!

Thanks C. I know that you love that 6G3 of yours...

Now regarding how well this design/project will turn out to be... We'll see ...



Frankly speaking, it will not be a hybrid, you know (in terms of mixing two amp designs in a single channel; in some other sense it is a hybrid afterall). Its bright channel is a %100 6G3 (with a heavy weight OT which will be run @ half power... hence, still ~18W (as it should be) ... hence it is a 18-20W 6G3 but with a bigger OT).

The other channel, 5E3, is what's kinda funky about it. And in order to get it rightish, we are adding the cathode bias / fixed bias switch and negative feedback controls...

Anyways, we'll see.

B

 

[Fresh_Start]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Am I correct guessing that you're using the long-tailed phase inverter from the 6G3? If so, the amp is not going to sound/feel just like a 5E3. The concertina splitter is part of the Tweed Deluxe's mojo. Also, it will be higher gain than a Tweed Deluxe because the LTPI has some extra gain to it.

Not saying it's a bad project, just pointing out that when you do a "hybrid" every step of the circuit has to be considered.

I built a Super Reverb with the "Normal" channel starting out like a 6G16 Vibroverb, reverb on both channels, and bias vary tremolo like the Vibroverb. Turned out great, but I did a LOT of tweaking on the Normal channel. The tapped Treble pot Fender used briefly is one weird critter. But the 6G16 and the AB763 share similar power amp sections and I consider the PI part of the power amp.

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Am I correct guessing that you're using the long-tailed phase inverter from the 6G3? If so, the amp is not going to sound/feel just like a 5E3. The concertina splitter is part of the Tweed Deluxe's mojo. Also, it will be higher gain than a Tweed Deluxe because the LTPI has some extra gain to it.

Not saying it's a bad project, just pointing out that when you do a "hybrid" every step of the circuit has to be considered.

I built a Super Reverb with the "Normal" channel starting out like a 6G16 Vibroverb, reverb on both channels, and bias vary tremolo like the Vibroverb. Turned out great, but I did a LOT of tweaking on the Normal channel. The tapped Treble pot Fender used briefly is one weird critter. But the 6G16 and the AB763 share similar power amp sections and I consider the PI part of the power amp.

Thanks for chiming in.

I have to emphasize that I really appreciate the feedback. In fact, this is the very reason that I have opened up this thread.

You are right about the PI. That was exactly what my plan was. To get the 6G3 part spot on, and then get the 5E3 part as well as possible given the structure needed for the 6G3 side. So am not gonna give in to changes to the 6G3 side (by the way, instead of that log 350K 70K tapped pot, I am gonna go with a 250K pot with a 70K resistor, as generally advised).

Would the difference in the PI change the 5E3 too much? Basically this is the question?

Moreover, I guess the plate voltage levels are not good for a AB763 design... This will have a plate voltage around 360V. What would be your response to this?

Best,

B

 

[jeremy]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

youll lose a little clean headroom with the lower voltage.

the different phase inverters will definitely make a difference. that wasnt my best crafted sentence. ive never heard a 5e3 preamp thru a long tail pair so had to say

 

[dr.barlo]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Cool. Thanks for the info...

B

 

[glassman]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

The power transformer selection concerns me for what you are trying to do, particularly if you plan to run 6V6's.

A major part of the "tweed sound" is a power supply that limits the power output of the amp combined with low value filter caps (for fast recovery). This is what gives them the almost unforgiving dynamic response they have. The smallish output transformers in tweed amps also saturate quicker (which shrinks bandwidth) which causes them to become very midrange focused when overdriven and REALLY project; your larger OT selction won't do that.

I think the transformers you selected would work really well in a 6L6/5881 based amp but the vibe would probably be more Bluesbreaker/tweed Bassman than 5E3.

 

[Fresh_Start]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

360 volts on the power tube plates should sound nice, although not quite as much clean headroom as the AB763.

I would plan on experimenting with your cathode resistors (maybe higher value) on the first stage of the 5E3 channel. Maybe even have a 12AU7 handy. Both to reduce overall gain. Don't worry though. You won't be the first to put a LTPI after a Tweed Deluxe preamp. It will give you more clean headroom.

Hoffman Amps has the odd tapped pot and I recommend trying one. It works.
** I'm confused now as the 6G3 didn't use the unusual tapped 350K Treble pot **

Lower voltage supply for the 5E3 12AY7 Plates is something you should plan for. I've just found voltages as low as 118 vac on the plates. Separating the supply nodes on your power rail is a good plan anyway.

Most of all "Plan to be wrong about something." Best advice I ever got on the Hoffman forum.

Cheers,
Chip

 

[misterwhizzy]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

Just from a convenience point of view, I really hate having knobs that will be adjusted on the back. I've got a voicing switch on a push-pull pot on the back of my amp, and its easy to forget the position, and the pot is for depth. If it's possible, I would suggest moving them to the front of the chassis, although I understand this may not work at all.

 

[Fresh_Start]

Re: A "Deluxe" Project: 5E3 / 6G3 amp project

I understand misterwhizzy's concerns, but OT tap, negative feed back or fixed/cathode bias switches belong on the back of the amp - if only for layout cleanliness.

Sorry but I completely missed the power transformer issue which Glassman points out. If you're sticking with Allen Amps iron (great stuff BTW), the TP35 looks as big as I would go. Frankly, I'd rather stick with a PT and OT specifically intended for normal 6V6s (not JJs). His TO22 looks good in terms of an OT. Hoffman's Deluxe OT with an 8,000 ohm primary might be a better choice though.

You could enhance the cathode-biased Tweed mode by adding a switchable sag resistor between the rectifier and the power tube plate node on the power rail. That would lower the B+ voltage some and give you more... SAG. Sorry, I just had to do that. Either that or switch in significantly bigger screen grid resistors when you go to cathode bias. An ON-OFF-ON switch that goes from fixed bias to standby to cathode bias is a clean way to handle that task. You do NOT want the power tubes on line when you switch their bias.

FWIW I don't like the tone or feel of JJ 6V6s anywhere near as much as Tung Sols. Just my opinion. The JJs can handle much higher plate voltages than normal 6V6s which means that other things inside are different from vintage specs.

IMHO it's OK to build a single-ended amp like one of the AX84 projects that is switchable for multiple power tubes. However, by the time you're working with a push-pull design using a long-tailed PI, your "hybrid" may end up being the "jack of all trades and master of none." Besides the OT primary impedance, you have to worry about heater current capacity, bass response, touch response (which you won't get with a massive OT and PT), bias voltage and/or adjusting the power tube cathode resistor for different tubes in cathode-biased mode.

All this talk about the 6G3 has given me an idea though. I built a Princeton Reverb for myself a few years ago. I've been itching to start tweaking it but lacked a direction. A low power Vibroverb/Vibrolux might be just what the doctor ordered!

Cheers,

Chip