12ax7-ecc99 tube amp

[Renegadrian]

I had some nice emails with a guy named Patrick, starting from a video on youtube...He just made a GREAT tube amp, based on the Firefly...I asked his permission to post it here to share with all of you, as he's been so kind and ready an'willing (sorry, whitesnake fan here...) to share his work with others...So here it is...

this is the video he made...
http://www.youtube.com/watch?v=_l1kowPgmH0
and the schem...
http://www.bilder-hochladen.net/files/b3cc-4-jpg.html

Thank you again Pat! You're really kind!!!
PS Great Vid you made - it sounds SO GOOD!!!

[DougH]

Explore in here a little: http://www.aronnelson.com/gallery/main.php/v/DougH/amp/

[head_spaz]

Out of all the projects I've built over the years, the Firefly is a real keeper !
Doug Hammond really did an exceptional job on his FIREFLY design.

A guy named John Calhoun made a wonderful contribution to Doug's project
by designing an elegant PCB to make Doug's project really simple. It's a very
clever layout too. PCB website here

I built two of them for myself and like them both VERY much. The Firefly is a
LOT louder than you might think with the ECC99, and it has terrific tone.
I always plug straight-in and it sounds awsome with a 12" Vintage 30 from
Warehouse Guitar Speakers.
I used AX84's 1x12 cabinet design.
The Firefly has a real nice touch sensitivity to it. No stompboxes required !!!

John's new PCB (v8.0) eliminates ALL of the hum that the older versions were
burdened with.
This new board is damned_near silent, noise wise, even at full gain volume.
(I'm the guy that came up with the mods to fix the groundloop hum in the older
version 7 boards. The newly designed board (v8.0) incorporates those mods, so
it's good-to-go!)

Some say that the Firefly is a "one trick" pony... but with the ECC99, I find that
I can get a little more headroom out of it.
Without the hum... it's a much better amp... I'm sure it sounds closer to what
DougH designed in the first place.
Keep in mind that most of the sound clips and commentaries you're likely to find
are older projects that use the noisy PCBs and the 12AU7 for the output stage.
Similar... but different. I think the ECC99 and the new PCB sounds much better!
The PCB makes this project a snap to build. I built the board in one evening.
The chassis took a little longer because I'm a perfectionist.

I would suggest upgrading to MusicalPowerSupplies' OP5PP output
transformer over the Hammond though. I've used both, and MPS's sounds a whole
lot better - a tighter bottom end and less high frequency hash/hiss.
I haven't tried the Doberman OT........ yet.

If you decide to build one, don't forget to re-bias the ECC99 using a 220 instead of
the 440 ohm resistor (R13).
I'd wish you luck... but you probably won't need it.  

More references:
AX84's Firefly Archive
AX84's Forum... look in the Firefly discussion group.

Look out you'se kids... don't put yer lips on it!

[DUY1337GUITAR]

OMG that sounds incredible

[DougH]

I would suggest upgrading to MusicalPowerSupplies' OP5PP output
transformer over the Hammond though. I've used both, and MPS's sounds a whole
lot better - a tighter bottom end and less high frequency hash/hiss.
I haven't tried the Doberman OT........ yet.

A big part of that will be influenced by the speaker too. I found that my Peavey 4x12 is much kinder to the Hammond transformers. I have been trying to come up with a 1x12 solution for my Dragonfly. I don't like the sound with the Red Fang or the G12H30. I just ordered an Eminence Swamp Thang to try in that cabinet. It's supposed to have more bass, subtler highs, and it is 150W so it won't add its own breakup like the Red Fang does. The RF breakup sounds good with the "Voxy" Chime & Grind, but sounds fizzy with the Dragonfly, which is more midrangey and higher gain. I'll find out in week or so if I can get happy with this amp through the 1x12. Through the 4x12 it's killer.

[slacker]

That sounds really nice. I'm planning on building a Firefly this winter and that's given even more of an incentive

[head_spaz]

Doug,
I would never argue with you, especially about your own design, but have you actually tried using MPS's OT5PP ?
I lost my hard drive recently, and all my email archives went with it. But I seem to recall Matt telling me that his OT5PP measures approx 30H. Whereas Hammond's 125E has about 15H.
The OT5PP is slightly smaller in physical size, but not by much.
I noticed a marked improvement right away. And since I'd built two Fireflys, identical except for the OT, I was able to compare them directly. The OT5PP sounds way better - tighter bass, and much less hash.
So now, both of my Fireflys are running the OT5PP and the Hammond 125E had to find a new foster parent, via ebay.

The Hammond 125E sounded fizzy on everything I've got.
2 - 2x10 JBL E110's
4x10 JBL E110's
1x12 JBL D120
1x12 Eminence - Red White and Blues
1x12 Eminence Wizard
1x12 Eminence Cannibus Rex
Vintage 30 WGS
G12H30

OT5PP... less fizzing... tastes great!

DougH,
U-DA-MAN, so I won't argue the point, but I would like to rationalize my suggestion if I may.
As you've pointed out, the Hammond may require an exclusive speaker configuration just to "get-by."
So unless someone has already bought the Hammond, why not instead just get the better transformer that's about equal in price from the "get-go"?
YMMV, but hindsight indicates to me that the Hammond is a false economy, because its purchase doesn't save enough money to pay for the speaker needed to mask its deficiency.
What I wasted on the Hammond would have covered half of the cost of a speaker - that being an EXTRA speaker, rather than a NECESSARY speaker.
No offense intended, just my observation.

[DougH]

Oh, I would agree with getting a better output transformer to start with. I have also heard that the reason the Hammonds sound the way they do is due to inductance. If I were starting from scratch, I would try the Heyboer transformer that was made for the ax84 4-4-0 studio amp. I'm sure the one you mentioned sounds better too. I'm just saying to pay attention to speaker choice too.

[head_spaz]

DougH,
Yes. You are absolutely correct. I should have been more accurate and specific in my initial post.
The "Doberman transformer" that I thought was available from Doberman is in fact a different transformer altogether.
I meant to say that it is offered from Chappellamps and is manufactured by Heyboer for the 4-4-0 studio amp project, which is not actually an AX84 design. It is credited as an "associates design", just like your Firefly.

Chappellamps currently offers the Heyboer 4-4-0 transformer for $65 outright. (DougH approved!)

I would definitely like to try a Heyboer someday, especially to compare it with MPS's OT10SE in an AX84 High Octane I just finished.
But at less than half price, a $29 OT5PP is pretty hard to resist, especially when it out-performs the more expensive Hammond 125E, which is supposed to be Hammond's "upgrade" to their 125A/C.
BTW... I looked it up... the OT5PP measures 35H inductance, not 30H as I inaccurately reported earlier.

However, price should never be the only consideration... because some of the most expensive things in life are FREE.
(Of course congress disagrees, which proves my point!)

[Hanglow]

Interesting, I haven't played with my firefly for quite a while now, getting tempted to change it, might try this one out

Has anyone tried the trainwreck inspired one that's on amp garage?

[rotylee]

So... are there any 6SN7GTB vs ecc99 comparison threads anywhere.?
i know one is octal and one noval.

[FcKw]

Hi @all,

I'm Patrick the guy who built the amp and recorded the clip. First thanks to all the kind words, especially to Renegadrian for his interest in my video!
My main goal was to build a small tube amp for practice and recording purposes at lower volumes that fits in a Hammond type BB enclosure, uses some common tubes and nails this slightly overdriven crunchy tube tone I prefer with my tele.
The amp started from the AX84 Firefly rev. 3 schematic without the boost stage (Thanks to Doug Hammond for his awesome design!). Then I started to modify the amp. I changed the poweramp tube to an ECC99 for slightly more headroom and a better bass response, especially at low volumes. I think it was DougH himself who wrote somewhere that this changes the amp from a toy to a "real" amp or something like that and I have to say you're absolutely right! And the second thing I did were some modifications to the preamp to shape the overall sound and overdrive behavior to my taste. I'm quite satisfied with the result.
So I used the Hammond 125A mainly because of its miniature size and price.

Here is another video with the final modified version and a modified colorsound wah I built:
http://www.youtube.com/watch?v=Lz03ZnOJnDc

And I also made a video directly after building the amp, with the unmodified Firefly preamp and a 12AU7 in the output-stage:
http://www.youtube.com/watch?v=bPi-RG7-y48

greets
Patrick

[doitle]

Hey Patrick. I really enjoyed your videos on youtube. Especially that you sort of step through the process of building an amp from scratch and even though you don't go through all the details it's valuable to see that process from vision to completed project.

I've got several tube radios sitting around and am literally surrounded by boxes of parts and tubes and just keep running out of time to work on projects with school started again. Your videos though have renewed my vigor to make time and finally build something.

Also could you elaborate a little bit about the swap to the ECC99? I've read that it is classified as a "super" triode and that it has a high gm and a low Rp. This certainly sounds interesting to me as some of the 70-volt line transformers I bought as OT are fairly low impedance... <8K.

Also do you have any tips for scavenging or acquiring low cost alternatives to the traditional power transformers? Those are my current stumbling block as I've acquired a few OTs... lots of tubes... a few chassis but I have no power transformers as of yet.

[FcKw]

... Also could you elaborate a little bit about the swap to the ECC99? I've read that it is classified as a "super" triode and that it has a high gm and a low Rp. This certainly sounds interesting to me as some of the 70-volt line transformers I bought as OT are fairly low impedance... <8K.
...

I basically chose the ECC99 because it was recommended in the AX84 forum for some better bass response in this circuit. I am using it with the highest impedance I can get from the 125A wich is around 22K I think and I adjusted the cathode resistor to its needs. But from what I've read it seems to be quite flexible when it comes to OT impedance. But perhaps someone else with more experience can tell you more about the OT impedance problem with those triodes. One other thing you should consider is that the ECC99 needs 800mA instead of the 12AU7s 300mA with 6,3V heater voltage.

... Also do you have any tips for scavenging or acquiring low cost alternatives to the traditional power transformers? Those are my current stumbling block as I've acquired a few OTs... lots of tubes... a few chassis but I have no power transformers as of yet.

Yes, I know what you're talking about. Unfortunatly I don't know much about the US transformer market, but as you can see I used a toroidal transformer from an online shop here in europe called "Das Musikding" with the secondary specs: 185V/0,04A and 6,3V/1,4A, perhaps you can find some US equivalent somewhere, it was about 22€ (~32$) were a suited Hammond would cost about 60€ (~87$) over here. here is the link

greets
Patrick

[DougH]

You can usually pick up a decent surplus 110/208VAC isolation transformer for around $10 or so. Those work perfect for these amps with relatively low current drain. Add a surplus 6.3VAC filament xformer for $4 and you are all set. That's what I used for my Firefly (and now Chime & Grind).

[DougH]

One more comment on the "is it the output transformer or is it the speaker?" discussion.

Last night I plugged my Octal Fatness into my Red Fang in my 1x12 and didn't particularly like the sound. It was fizzy and harsh, somewhat. So I subbed the little $15 AES output xformer with a Heyboer S/E output xformer on my bench and did some experimenting. Through the same speaker and cabinet- the sound improved marginally. There was better low frequency response and a slightly "fuller" sound. But the fizz was still there and it wasn't really that big of an improvement. Fortunately the Heyboer has a 16 ohm tap, so I tried it through the 4x12. The sound of this amp came alive at that point. The fizz was all gone, better lows and mids, etc, etc. It sounded really great and solved all the problems I had with the other speaker. Also, I had been using beam tubes (6L6, 6AR6) because with an EL34 it was unlistenable with the 1x12. But through the 4x12 it didn't matter. It loved all the tubes and I could dial up the gain, master volume, tone controls anywhere I wanted to and it sounded great.

I think one of the keys is that the speakers in the 4x12 are 50W speakers and don't add any distortion of their own. In contrast, the Red Fang breaks up real early, and you can definitely hear it. Don't get me wrong- I love the Red Fang, and I think for Voxlike amps it sounds great. But for midrangey high gain amps it doesn't seem to work very well for me.

Unfortunately I cannot physically fit the Heyboer on this amp chassis, so I'll have to go back to the AES which only has an 8 ohm tap. (I'll probably build another s/e amp on a bigger chassis with the Heyboer at some point.) I'll see when my Swamp Thang comes in if that solves this issue with the 1x12, and then it doesn't really matter. It's coming in tomorrow and I'll have to give it a few weeks to break in.

So yeah, if you're building an amp from scratch, get a decent output xformer. But don't neglect the speaker. It has a big influence on the overall sound. And so far I'd say, a 4x12, at least this one, makes up for a whole host of ills.

[alternative84]

Hi!
As Renegadrian, I saw the video that Patrick uploaded and I decided to build one of these! I used the same chassis and layout that he used, because I really liked the size, It's tiny! I ordered all the components from "Das Musikding" (I'm Spanish), except the ECC99 and a few vintage carbon resistors that I ordered from "Tube Amp Doctor". I built the amp in only two days and took a few photos of the process. As Patrick told me in an email, I set up the cathode resistor in 220 ohm (I had trouble drawing the load line, because I'm not too good with tubes theory, at the moment ).

I've been testing the amp with 12AY7 (Groove Tubes Gold Series) and ECC83S (JJ)... and I cannot decide between them, because they both sound great . The cab is a Framus 2x12 (Celestion Vintage 30), but I have to try with the 1x12 cab that I'm building now, with a Jensen P12Q Alnico speaker.

These are the photos of the amp, I hope you like it (sound samples coming soon!).

http://www.megaupload.com/?d=TNDNM2KL

[Renegadrian]

THX for the report and welcome!!! 

[frequencycentral]

Hey, sounds interesting - but can't you find some other way to host the photos? Photobucket maybe? I don't really want pop-up ads and to have to wait 3 minutes to download files just to see them...........

[Brymus]

Wow that is an amazing difference from the first version to the ecc99 version (I listened to both vids)
I really liked the mellow song with the subtle lead/melody and the tele and old albums at the end was nice.
What are the specs on that toriodal you are using? and where did you get it?
After hearing this I am glad I didnt start one of these low wattage PP amps yet,I almost ordered the tubes last month but now I will get the ECC99 tubes instead.
I think I will make mine with a 125E and use 4 ECC99 tubes for 10 watts and just pull 2 of em for 5 watts.

I really am impressed by how well the amp sounds after you modded it and switched the output tubes.