EL34 Baby Huey Amplifier

[zintolo]

Thank you also for your reminder about CFB transformers - I forgot about the additional drive requirements with them. I will have to learn LTSpice to play with and balance these things and devise a proper drive circuit for those Toroidy TTG-CFB6600PP transformers in the closet.

LTSpice is an useful tool, but it's really only part of it. I use it during the week, when I cannot push the amp to its limits and hear how it sounds. Then details must be defined by hear IMO.

I don’t know if it is a simulation artifact, or some other cause, but I am dubious about the “optimal CCS current” result of >6 ma for two 12AX7 triodes. See the chart below.

I was probably not clear in my explanation, but the current I was talking about is through the leds of the CCS, not through the NPN (so not passing through the PI). It is clear that a current flowing through the triode would change its working point and so its harmonics, but here I'm talking about the current through the leds.

 

[zintolo]

This is again a cascoded version of the BH with KT88.

In attachment there's the schematic in image and LTSpice format, here below the THD at 70 Wrms with no gnfb:

Harmonic	Frequency	 Fourier 	Normalized	 Phase  	Normalized
 Number 	  [Hz]   	Component	 Component	[degree]	Phase [deg]
    1   	1.000e+03	3.341e+01	1.000e+00	   -3.54°	    0.00°
    2   	2.000e+03	9.127e-03	2.732e-04	  -93.13°	  -89.59°
    3   	3.000e+03	2.083e-01	6.237e-03	 -146.94°	 -143.40°
    4   	4.000e+03	9.812e-04	2.937e-05	  -90.02°	  -86.48°
    5   	5.000e+03	2.459e-01	7.362e-03	 -177.65°	 -174.11°
    6   	6.000e+03	6.152e-04	1.842e-05	  -86.21°	  -82.67°
    7   	7.000e+03	2.082e-02	6.231e-04	  162.87°	  166.41°
    8   	8.000e+03	5.356e-04	1.603e-05	  -82.22°	  -78.68°
    9   	9.000e+03	3.107e-02	9.300e-04	  174.51°	  178.06°
Total Harmonic Distortion: 0.971709%(0.971996%)

 

[zintolo]

Another trial of the cascoded version of the BH, this time with KT120.

In attachment there's the schematic in image and LTSpice format, here below the THD at 110 Wrms with no gnfb:

Harmonic	Frequency	 Fourier 	Normalized	 Phase  	Normalized
 Number 	  [Hz]   	Component	 Component	[degree]	Phase [deg]
    1   	1.000e+03	4.177e+01	1.000e+00	   -2.91°	    0.00°
    2   	2.000e+03	1.047e-02	2.507e-04	  -91.83°	  -88.92°
    3   	3.000e+03	1.350e-01	3.232e-03	  -71.34°	  -68.43°
    4   	4.000e+03	5.792e-04	1.387e-05	  -71.50°	  -68.59°
    5   	5.000e+03	2.946e-01	7.053e-03	 -168.55°	 -165.65°
    6   	6.000e+03	2.006e-04	4.803e-06	  -76.50°	  -73.59°
    7   	7.000e+03	1.674e-03	4.007e-05	 -112.26°	 -109.35°
    8   	8.000e+03	1.510e-04	3.615e-06	  -79.49°	  -76.59°
    9   	9.000e+03	2.552e-02	6.109e-04	  175.67°	  178.58°
Total Harmonic Distortion: 0.778626%(0.778689%)

 

[Algar_emi]

Hi. What is the Mouser part number for the NTC of the Baby Huey MK2 power Supply?
I cannot find it in any BOM that I have.
Thanks
SB

 

[bloozestringer]

In a BOM from Gbowling in post #635 I have mouser part #871-B57235S0100M000.

https://www.mouser.com/ProductDetail/EPCOS-TDK/B57235S0100M000/?qs=AKDv8POSxR1PE26cesafLQ==

 

[Algar_emi]

Thanks
SB

 

[Algar_emi]

Would that be interest into an other GB for the EL34 Baby Huey? I asked the previous GB organizer and the Baby Huey design team and they didn't object. I don,t want to walk on any one toes. Anyway I put together the PCB for the Baby Huey EL34 MK2 Ver1.51 and the Power Supply MK2, ver 2.0. Still Working to put together the updated BOM for each, but here the PCB layout. I tried to include all the latest findings and mods, and I also changed the PCB connectors to more standard (and less expensive) Phoenix connectors. Any comments appreciated. I'll post the BOM in a few days...

I'm planning to order a set of PCB for me, but if there is enough interest I may start a GB. Let me know. Thanks
SB

 

[dch53]

Hi. I already have Ver 1.5 boards that I'm hoping to assemble soon. What are the differences between Version 1.5 and Version 1.51?

 

[Algar_emi]

Check I based my PCB on this pcb image I found on this long... thread. Ver1.51 was marked on it. Don't know really what is the difference between 1.50 to 1.51. May be just some cosmetic thing or some silkscreen corrections. This version is also designed to install the tube sockets and trimmer on the back, maybe the 1.50 was for the socket on the top...

I did changed the silkscreen/BOM of R7,R8 to 220K/2W, and R16 to 47K instead of 15k. Also in the thread it was mention the possible mods of replacing R17 by a second led, and to adjust R16 according to a chart to get the desired voltage at C10. My pcb also accept a led instead of R17...

 

[Algar_emi]

Here is what I'll order, the amp has a few changes:

AMP Ver1.51 Bottom: Updated a few silkscreen R7,R8 (220K/2w), update R16 to 47K, allow for R17 mods to use a led instead, all connectors are easier to get/less expensive from Phoenix or Molex...

PSU MK2: R17 external or choke, more space for R14, C4-C6 all 15nF/160V, C15,C16 Pins 7.5mm or 5mm, all connectors are easier to get/less expensive from Phoenix or Molex...

BOM updated to fit the pcb at all location...

Still have to do a final check before ordering, but it should be pretty close...

SB

 

[Dagwood]

Hi Algar_emi

I will be keen on a GB for the PSU boards

Thanks for kicking off another round.

 

[bekim]

Here is what I'll order, the amp has a few changes:

AMP Ver1.51 Bottom: Updated a few silkscreen R7,R8 (220K/2w), update R16 to 47K, allow for R17 mods to use a led instead, all connectors are easier to get/less expensive from Phoenix or Molex...


SB

Hi,

Please change values for the resistor R14 and R15 as suggested from gingertube in post #515 https://www.diyaudio.com/forums/tubes-valves/326920-el34-baby-huey-amplifier-52.html#post5853204 that, values should be 1K for EL34 and 6CA7.

Thanks

 

[Algar_emi]

Thanks for the info, change done. Got the transfo prices from Toroidy, herre their reply:
Thank You for contact us.

Please find an offer for needed transformers:

Audio grade version (potted interior):

Mains transformer TSTA 0250/001 AUDIO [2x115V] - 83,90 EUR / pc (0% VAT export price)
Output transformer TTG-KT88PP AUDIO - 71,60 EUR / pc (0% VAT export price)

Supreme version (potted in the stainless steel box) with the side-wiring plates:

Mains transformer TSTA 0250/001 SUPREME [2x115V] - 136,40 EUR / pc (0% VAT export price)
Output transformer TTG-KT88PP SUPREME - 120,00 EUR / pc (0% VAT export price)

In audio grade, noiseless transformer price You'll get transformer winded with with the largest possible inductance.
Core will be measured and selected, nominal induction will be lowered for the leakage flux minimalization
For a best noise reduction core and all the windings are impregnated.
Transformer will also has electric and electromagnetic shields and epoxy filled interior.
Audio SUPREME version is fully epoxy resinged in stainless steel box:
https://sklep.toroidy.pl/userdata/public/assets//Transformers grade comparision.jpg

 

[Algar_emi]

Will start a GB probably tomorrow. There will be option to order the AMP Ver1.51 and/or PSU MK2 separately.
Thanks
SB

 

[Dagwood]

Hi, can you confirm the physical layout of the amp board is the same as the old boards? I have a chassis already cut to those dimensions.

Thanks

 

[zman01]

Dagwood,

Are you referring to the dimensions of the PCBs from Bandol83's original GB for the EL34 BH amplifier?

I think I have a set of those somewhere...

 

[Dagwood]

Hi Zman01

These are the boards, I think they were the second GB but not 100% sure.

 

[zman01]

Maybe - my PCBs look slightly different to these...

 

[Dagwood]

Yes the original had provision for a volume pot in front of the ECC83

 

[Dagwood]

My problem is I have 2 pairs of mono block chassis and only one set of PCB's. Another member has a pair of PSU PCBs I can buy, but no one seems to have the actual AMP boards spare. Fingers crossed the layout overall is the same for this GB

My chassis is in paint stage at the moment.