5E3 DeLuxe Circuit

[John Egan]

Hi,
Just got myself a new amp head, which uses a 5e3 DeLuxe circuit, mainly for recording as a complementary alternative to my old Selmer T&B 50 MkII.
It came fitted with two 12AX7 tubes in the preamp, rather than the original 12AY7 in the V1 position. I thought this was very "boomy", as I remember these amps sometimes were. So, as I hadn't got a 12AY7 handy and the replacement hadn't arrived, I fitted a 12AU7 in the V1 slot, half expecting it to be too weedy. It wasn't.
When the AY arrived, I decide to fit both it and the AU and experimented with swapping the two around between V1 and V2. My preferred configuration is with the AU in V1. For my purposes, I much preferred this to the sound with the traditional AY + AX setup. It gives me more clean headroom and still seems to get the traditional tweed DeLuxe overdrive when whacked up (though with less volume, which suits me).
My question is what difference would you expect to find between the AY and the AU pairing when swapped around between V1 and V2. As you might expect, the interaction between the two volume controls and the tone control does make it difficult to be sure that the difference I think I am hearing is really there.
They always were slightly bewildering amps!
Regards, John

[Wonks]

Might not be what you wanted but this is a very good description of the 5E3 circuit in both layman's and more technical terms.

https://robrobinette.com/How_The_5E3_Deluxe_Works.htm

[John Egan]

Might not be what you wanted but this is a very good description of the 5E3 circuit in both layman's and more technical terms.

https://robrobinette.com/How_The_5E3_Deluxe_Works.htm

Thanks Wonks,

Unfortunately, my technical knowledge isn't up to answering my question, which was whether swapping preamp/PI valves around (in my case a 12AY7 and a 12AU7) should make a difference to the sound. It seems to me that it does, but I wondered what the theory says.

Regards, John

[Wonks]

I think it's more an art than science. I bought a hand-wired 5E5A based amp from eBay that was based on reusing the guts of a Fender Blues Deluxe amp - transformers, cabinet and amp chassis, with the rest replaced by a hand-wired turret board circuit (and a Weber copper cap rectifier). Came with 12AX7s in V1 and V2 when they should have been 12AY7s.

Didn't sound that great at first but swapped the AXs for AYs and also the heavy Eminence speaker it came with for a Celestion Neo Creamback and it now sounds superb.

Obviously there are differences between the valve types not just in gain but in plate characteristics and subsequent effects like the valve's current draw. A 12AU7 has a (specified) gain of 17, whilst the 12AY7 has one of 40. The bias points of the valves will also be different, so swapping valves doesn't only change the gain at that point in the circuit, but because the bias will be different, then the valve will operate slightly differently to the way it would behave in the correct socket, and so will sound a bit different as well. Which is where the 'art' and personal preference comes in.

I think ef37a said that it's not a good idea to put a 12AX7 in a socket designed for the other AX valves as it takes about 4 times the current of the others so can easily cause overheating problems - but I must profess my ignorance at any real details here and I may (probably) have got it wrong.

[John Egan]

I think ef37a said that it's not a good idea to put a 12AX7 in a socket designed for the other AX valves as it takes about 4 times the current of the others so can easily cause overheating problems - but I must profess my ignorance at any real details here and I may (probably) have got it wrong.

Hi Wonks,

In fact the original 5E3 normally used a 12AY7 in V1 and an AX7 in V2. I understand that some of the boutique clones use 12AX7s for both V1 and V2 and that's how mine was set up. It had much too much bass and was louder than I really wanted (probably great for gigging, but I want this for recording principally), so I decided to reduce the gain significantly. It performs beautifully now. Not unlike your story really.

Thanks for the help.

Regards, John

[Folderol]

The (potential) problem one is 12AU7. 12AX7 is the kindest of the lot.. The issue is the rating of the anode load resistors. If they are wimpy little 0.25W carbons change them for 0.6W metal film and you're good to go.

[John Egan]

The (potential) problem one is 12AU7. 12AX7 is the kindest of the lot.. The issue is the rating of the anode load resistors. If they are wimpy little 0.25W carbons change them for 0.6W metal film and you're good to go.

Hi Folderol,
Thanks for the heads up. I did check with the amp tech who built the 5E3 head for me and he is perfectly comfortable with me using a 12AU7 and a 12AY7.
Regards, John

[zenguitar]

Might not be what you wanted but this is a very good description of the 5E3 circuit in both layman's and more technical terms.

https://robrobinette.com/How_The_5E3_Deluxe_Works.htm

Bookmarked that site; very useful indeed, cheers Wonks

Andy

[ef37a]

The (potential) problem one is 12AU7. 12AX7 is the kindest of the lot.. The issue is the rating of the anode load resistors. If they are wimpy little 0.25W carbons change them for 0.6W metal film and you're good to go.

Bob on Will! I understand some of the old Fender amps were among the worst offenders for fitting low rated loads?

The boot is also on the other shoe, as it were! Do NOT fit an ECC83/12AX7 in place of an ECC82/12AU7. The latter valve is used where a low impedance drive or even a bit of power is required (Series One amps and HT-1) The 83 will burn out and sound dreadful to boot.

The 5E3 has an unusual feature, it employs the 'concertina' phase inverter. This is almost unseen in guitar amplifiers because, 1) it gives no net gain and 2) it generally sound awful* if overdriven. However, when drive is kept within reasonable bounds it gives very low distortion and a wide bandwidth and appeals to the Hi Fi brigade and after all, Fender WERE trying to make CLEAN amplifiers!

*This is not inevitable. Look up 'Tube Preamps' by Merlin Blencowe. (It's ok, he reverts to English inside!)

Dave.

[John Egan]

Might not be what you wanted but this is a very good description of the 5E3 circuit in both layman's and more technical terms.

https://robrobinette.com/How_The_5E3_Deluxe_Works.htm

Bookmarked that site; very useful indeed, cheers Wonks

Andy

Hi Andy,
I'll second that. I've been reading the 5E3 data since Wonks sent me the link and even for a non-techie like me it helps me understand (dimly) how the amp does what it does.
Once again, thanks Wonks.
Regards, John

[IvanSC]

Built mine few years back and it is still my favourite amp apart from my old cream 63 Tremolux piggyback that I foolishly sold in 1980.... for £80!!! (where is the crying buckets of griff smiley?)

[John Egan]

Built mine few years back and it is still my favourite amp

Hi Ivan,
The fascinating thing is the way the two volume and the tone control interact. There seems to be an endless variety of tones on tap.
Regards, John

[IvanSC]

...as Neil Young discovered!

Can't stand his singing, but cant fault him on taste in amps

[John Egan]

...as Neil Young discovered!

Can't stand his singing, but cant fault him on taste in amps

Hi Ivan,

Yes, I love his "rough 'n ready" guitar playing and his obvious enjoyment when he's playing.

My 5E3 is a head, made for me by Jeff Pugh of Aston Electronics. I didn't have room for another combo and it shares the speaker cab of my Fargen Townhouse. Sounds lovely, except for the rotten playing!

Regards, John