To the new builders, I strongly suggest you start with gingertube's original design. It works reliably and sounds lovely. But after listening to one almost every day since Jan 2015, I think I'm allowed to explore variations.
I have tried more than just (current) Mullards and Genalex 12AX7s, and various EL84s for that matter too, but nobody needs to read all the details. I settled on Genalex in both positions, so with my first taste of 12AT7s I went to Genalex too.
I'm not interested in chasing NOS tubes. It's just not worth the fuss and expense for me. If I was to find some genuine Telefunkens sitting in a box I found in the attic, I would not be unhappy, but it's not likely is it.
BTW fellow Australians. You don't have to buy parts from overseas. I bought almost everything from here in Brisbane from a specialist guitar amp parts store. Postage is cheaper and quicker.
I have tried more than just (current) Mullards and Genalex 12AX7s, and various EL84s for that matter too, but nobody needs to read all the details. I settled on Genalex in both positions, so with my first taste of 12AT7s I went to Genalex too.
I'm not interested in chasing NOS tubes. It's just not worth the fuss and expense for me. If I was to find some genuine Telefunkens sitting in a box I found in the attic, I would not be unhappy, but it's not likely is it.
BTW fellow Australians. You don't have to buy parts from overseas. I bought almost everything from here in Brisbane from a specialist guitar amp parts store. Postage is cheaper and quicker.
In the US its fairly easy to get a nice pair of NOS tubes for very little “fuss”.
If you haven’t tried the well regarded NOS variants and can’t get a pair easily, I’d be happy to sell you a pair from my stash. The cost wouldn’t be much more than those Genalex new production. You can PM if interested.
For 12AT7s, the gold pin 6201 SQ types by Phillips are some of the best
If you haven’t tried the well regarded NOS variants and can’t get a pair easily, I’d be happy to sell you a pair from my stash. The cost wouldn’t be much more than those Genalex new production. You can PM if interested.
For 12AT7s, the gold pin 6201 SQ types by Phillips are some of the best
I've been diving back into very old emails of orders to help me remember what it is that I ended up actually building way back then. The alternative is to go and open the box, but then I'd have to partly disassemble the tag board strips to be able to read the component values. Easier to trawl gmail from the relevant epoch.
While I wasn't smitten by the allure of NOS tubes and didn't go down that merry path, I confess that I did get a bit carried away with capacitors and I did buy rather a lot of expensive film caps.
See, I've been chasing dynamics and transients all along.
While I wasn't smitten by the allure of NOS tubes and didn't go down that merry path, I confess that I did get a bit carried away with capacitors and I did buy rather a lot of expensive film caps.
See, I've been chasing dynamics and transients all along.
Definitely agree about getting caught up in it, as for the most expensive portion of the amp, a rule of the thumb for me is that it will always be the output transformers.
I won't be able to perform them during following evenings, just be patient but I'll work on them.
At what output you've got 7,5%THD? I will share it, but I've used just 23% UL in my amp(s).
You may find interesting two variations I've done:
Slowly building three Baby Huey EL84 - with notes
with a hybrid-cascode bottom-tubed PI version capable of 15 Wrms at 0,23% THD with a pair of EL84
improvements on 12AX7 12AT7 EL34 schematic?
with a hybrid-cascode top-tubed PI version and nested feedback capable of 52 Wrms at 0.56% THD with a pair of EL34
I'm not in a hurry. I plan I getting use to the sound of the current (new) setup. In a week or so I'll swap back to the 12AX7s and see how I feel about them then. It might turn out that I like those better after all.
That said, I will still be very interested to hear what your simulations show. And thanks again.
I've built mines with Russian equivalents, indeed.
As a guideline for different suffixes, there's this interesting post:
Russian 6P14P tubes
Yes, typically this would be true. I opted for Electra Print, not sowter or other "holy grail" but good solid reputation and quality, and still tubes add up quickly
When you get to it, I will look forward to your simulation results with a 12AT7 front tube in the “standard BH” circuit. I expect the operating condition will need to be adjusted significantly; for example the current through the 12AT7 triodes will likely need to be increased well beyond the ~1 ma for the 12AX7.
Gingertube wrote that his personal favorite Baby Huey implementation was the 6SL7/6V6. So, I expect the 12AT7 gain (mu=60 for 12AT7, vs 70 for 6SL7) will be sufficient for EL84 output tubes.
With 250V across the tube and 10k Raa you should be able to run the tubes in class A full time. I remember I've seen also a document showing how EL84 up to 250V B+ reacted in a more triodeish way with "Shade" feedback, compared to 300V and above. This also would explain why the father of the baby huey has 250V B+ with pentode connected EL84 and "shade" feedback plus a bit of gnfb to iron out PI's THD.
But I can't remember where I saved it, nor find it again online...
But I can't remember where I saved it, nor find it again online...
There was an older thread looking at OPT for EL84
Red Light District/Baby Huey (EL84 P-P) Output Iron
Red Light District/Baby Huey (EL84 P-P) Output Iron
Here it is my version of the BH EL84 with 330 V B+ and the following results (simulated) at 22 Wrms:
Code:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 1.891e+01 1.000e+00 -0.42° 0.00°
2 2.000e+03 7.237e-03 3.827e-04 -86.55° -86.13°
3 3.000e+03 3.810e-01 2.015e-02 -0.91° -0.49°
4 4.000e+03 1.907e-03 1.008e-04 81.60° 82.02°
5 5.000e+03 1.790e-01 9.465e-03 -172.99° -172.57°
6 6.000e+03 1.233e-04 6.521e-06 -37.22° -36.80°
7 7.000e+03 7.179e-02 3.796e-03 -7.62° -7.20°
8 8.000e+03 3.655e-04 1.933e-05 65.19° 65.62°
9 9.000e+03 1.967e-02 1.040e-03 -14.47° -14.05°
Total Harmonic Distortion: 2.260755%(2.271256%)Attachments
By simply substituing the 12AX7 with a 12AT7, the results at 13 Wrms are:
Code:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 1.455e+01 1.000e+00 -0.26° 0.00°
2 2.000e+03 9.702e-03 6.669e-04 -86.40° -86.14°
3 3.000e+03 3.055e-02 2.100e-03 -36.86° -36.60°
4 4.000e+03 5.565e-04 3.825e-05 64.48° 64.74°
5 5.000e+03 2.035e-02 1.399e-03 -49.30° -49.05°
6 6.000e+03 4.552e-04 3.129e-05 72.21° 72.47°
7 7.000e+03 4.376e-02 3.008e-03 -15.31° -15.06°
8 8.000e+03 3.308e-04 2.274e-05 71.68° 71.94°
9 9.000e+03 3.604e-02 2.478e-03 -14.64° -14.38°
Total Harmonic Distortion: 0.469068%(0.559864%)Remove the gnfb, set R16 to 37k and you'll get these results at 16 Wrms:
Code:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 1.611e+01 1.000e+00 -0.32° 0.00°
2 2.000e+03 1.422e-02 8.825e-04 -88.00° -87.69°
3 3.000e+03 3.073e-01 1.907e-02 -3.92° -3.61°
4 4.000e+03 4.221e-04 2.620e-05 -53.17° -52.85°
5 5.000e+03 2.951e-02 1.832e-03 -138.45° -138.14°
6 6.000e+03 5.616e-04 3.486e-05 76.99° 77.30°
7 7.000e+03 4.405e-02 2.734e-03 -20.45° -20.13°
8 8.000e+03 2.844e-04 1.765e-05 69.13° 69.44°
9 9.000e+03 3.993e-02 2.478e-03 -18.38° -18.06°
Total Harmonic Distortion: 1.953334%(1.984467%)