I have a few "spare parts" for Baby Huey or something similar tube amps for those who really want quality and superb looking amp.
These are "Raw" high quality american walnut wood frame and 3mm thickness aluminium top plate.
I use it on EL34 Baby Huey here:
https://www.diyaudio.com/community/threads/el34-baby-huey-amplifier.326920/post-7380662
I will post also at "Swap meet" area for sale.....but I was thinking first to the Baby Huey users....
These are "Raw" high quality american walnut wood frame and 3mm thickness aluminium top plate.
I use it on EL34 Baby Huey here:
https://www.diyaudio.com/community/threads/el34-baby-huey-amplifier.326920/post-7380662
I will post also at "Swap meet" area for sale.....but I was thinking first to the Baby Huey users....
Attachments
Was going through my BOM for the PSU board connectors and came up with these for screw type instead of spring type Phoenix terminal blocks and Molex from Mouser. If anyone has time to check and correct I'd appreciate it. Not sure on the amp boards yet.
| 1729128 | Phoenix | X1, X2, X3, X4 | 5.08mm, Terminal Blocks FFKDSA1/V1-5.08- 2 2 position, screw, 400V/17.5A |
| 41791-0849 | Molex | X5 | 3.96mm Header KK156 2-pin 600V/7A |
| 9503021 | Molex | X5 connector | 3.96mm Connector series 2139 KK156 2 pin |
| 1729128 | Phoenix | X5 Alternate | 5.08mm, Fixed Terminal Blocks FFKDSA1/V1-5.08- 2 2 position, 400V/17.5A (fit checked) |
| 1729144 | Phoenix | X6 | 5.08mm 4 pin terminal block, FFKDSA1/V series, screw, 400v/17.5A |
| 1725669 | Phoenix | X7 | 2.54mm, Terminal Block, 3-pin, screw, 160V/6A |
Dear All,
I have a pair of pcbs for this fantastic amp. Planning to build 2 monoblocks.
need help for the assembly of the amp.
The power transformers i have with secondaries :
1. 0-300Vac : 0.8A
2. 0-6.3Vac : 6A
3. 0-40Vac : 0.5A
Can this transformer be used for EL34 Baby Huey ?
Secondly, i have 2 sets of output transformers :
1. Hammond 1650F
2. EOP V78A01F
Both are rated at 25W, can any of these be used in this amp ?
I have attached some pictures and docs for reference. I would like to use the parts(transformers) in hand to complete the build.
Any help is highly appreciated.
I have a pair of pcbs for this fantastic amp. Planning to build 2 monoblocks.
need help for the assembly of the amp.
The power transformers i have with secondaries :
1. 0-300Vac : 0.8A
2. 0-6.3Vac : 6A
3. 0-40Vac : 0.5A
Can this transformer be used for EL34 Baby Huey ?
Secondly, i have 2 sets of output transformers :
1. Hammond 1650F
2. EOP V78A01F
Both are rated at 25W, can any of these be used in this amp ?
I have attached some pictures and docs for reference. I would like to use the parts(transformers) in hand to complete the build.
Any help is highly appreciated.
https://www.diyaudio.com/community/threads/baby-huey-gb-pcb-el34-build-thread.320273/
The Hammond has the wrong primary impedance, with the EOP the tap deviates from the Hammond by 24.5%.
With the power transformer, the voltage must be doubled in the 40V winding.
The Hammond has the wrong primary impedance, with the EOP the tap deviates from the Hammond by 24.5%.
With the power transformer, the voltage must be doubled in the 40V winding.
https://www.diyaudio.com/community/threads/hammond-1650p-vs-1650n-for-el34-pp.209934/
Hammond 1650F: If you connect an 8 ohm speaker to the 16 ohm tap you will get a different primary impedance !
Hammond 1650F: If you connect an 8 ohm speaker to the 16 ohm tap you will get a different primary impedance !
@Aniket,
Your transformers are almost right but not perfect.
1. The first problem with the power transformer is the 300 vac primary, but that you can work with to reduce to where you need it to be, for example by using a smaller film cap (around 6-8 uF is my guess for psuedo choke-input operation) in place of specified electrolytic for C7 with a good choke (2.5H or more). The second issue may be bigger; the 6 amp @ 6.3 Vac capacity of the heater coil. EL34 draws 1.5 amp each, so there is no capacity left to heat the ecc83 tubes. However, a ecc83 draws .3 amps, so a pair will overload your 6 amp heater winding by 10%. Depending on the robustness of your PT it may or may not handle it without overhearing. As @snapper mentioned, you may need to use a voltage doubler on the bias winding, but that is not a big deal either. Due to these issues, have you considered building a 6L6GB Baby Huey amplifier? If you search you will find several posts about 6L6-type implementations. A 6L6GB draws only 0.9 amps.
2. The Hammond 1650F with primary of 7600 and 25 watts max is more suited to 6L6 types than EL34. EL34 PP works better with 4.3 - 5 k primary and 35 watts out max.
3. I don’t know the EOP V78A01F, but it appears to have a primary of 5.6k. That is about half-way between the ideals for 6L6GB and EL34, but could be make to work with either. The 24.5% UL tap is perfect for EL84 (but it likes a 8k primary), and 6L6 I understand prefers 50% and EL34 33-43%. I’m not sure what the design rationale was behind this EOP, but it looks like a very nice transformer.
So, you have losts of good stuff but nothing works quite perfectly with Baby Huey. I would compromise and build a 6L6GB Baby Huey, using you PT with B+ adjusted for about 350 Vdc and possibly a doubler on the bias winding, with your Hammond 1650F OTs in UL mode. This will all have to be worked out using load lines at the chosen operating point and mode, but I guess you can expect about 22-25 watts output per amplifier.
Good luck.
Your transformers are almost right but not perfect.
1. The first problem with the power transformer is the 300 vac primary, but that you can work with to reduce to where you need it to be, for example by using a smaller film cap (around 6-8 uF is my guess for psuedo choke-input operation) in place of specified electrolytic for C7 with a good choke (2.5H or more). The second issue may be bigger; the 6 amp @ 6.3 Vac capacity of the heater coil. EL34 draws 1.5 amp each, so there is no capacity left to heat the ecc83 tubes. However, a ecc83 draws .3 amps, so a pair will overload your 6 amp heater winding by 10%. Depending on the robustness of your PT it may or may not handle it without overhearing. As @snapper mentioned, you may need to use a voltage doubler on the bias winding, but that is not a big deal either. Due to these issues, have you considered building a 6L6GB Baby Huey amplifier? If you search you will find several posts about 6L6-type implementations. A 6L6GB draws only 0.9 amps.
2. The Hammond 1650F with primary of 7600 and 25 watts max is more suited to 6L6 types than EL34. EL34 PP works better with 4.3 - 5 k primary and 35 watts out max.
3. I don’t know the EOP V78A01F, but it appears to have a primary of 5.6k. That is about half-way between the ideals for 6L6GB and EL34, but could be make to work with either. The 24.5% UL tap is perfect for EL84 (but it likes a 8k primary), and 6L6 I understand prefers 50% and EL34 33-43%. I’m not sure what the design rationale was behind this EOP, but it looks like a very nice transformer.
So, you have losts of good stuff but nothing works quite perfectly with Baby Huey. I would compromise and build a 6L6GB Baby Huey, using you PT with B+ adjusted for about 350 Vdc and possibly a doubler on the bias winding, with your Hammond 1650F OTs in UL mode. This will all have to be worked out using load lines at the chosen operating point and mode, but I guess you can expect about 22-25 watts output per amplifier.
Good luck.
Aniket,
(and critics)
Many "8 Ohm" loudspeakers do not work perfectly; check the measurements:
I have seen "8 Ohm" loudspeaker reviews that find 4 Ohm minimum impedance; and 50 Ohms maximum impedance.
Matching a pair of push pull tubes to many loudspeakers is more of an art than a science, since science says they are not matched.
There is no rule that prevents you from not using the UL taps, and instead of that, Triode Wire your output tubes (Well, admittedly, there is a rule that you will get less power output, but as a plus you also will get higher damping factor before you apply global negative feedback).
Plan enough room on your chassis to mount either model of transformer. Then test how they work by mounting pairs of them on a wood board, and try them for comparison. Decide which model to drill holes for on your chassis.
Have fun!
If you were not 1/2 way around the world, I would purchase the two transformers that you do not use. Too much shipping charge.
Just saying
(and critics)
Many "8 Ohm" loudspeakers do not work perfectly; check the measurements:
I have seen "8 Ohm" loudspeaker reviews that find 4 Ohm minimum impedance; and 50 Ohms maximum impedance.
Matching a pair of push pull tubes to many loudspeakers is more of an art than a science, since science says they are not matched.
There is no rule that prevents you from not using the UL taps, and instead of that, Triode Wire your output tubes (Well, admittedly, there is a rule that you will get less power output, but as a plus you also will get higher damping factor before you apply global negative feedback).
Plan enough room on your chassis to mount either model of transformer. Then test how they work by mounting pairs of them on a wood board, and try them for comparison. Decide which model to drill holes for on your chassis.
Have fun!
If you were not 1/2 way around the world, I would purchase the two transformers that you do not use. Too much shipping charge.
Just saying
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If I understood correctly, he is planning monoblocks, so the heating output will definitely be sufficient!
The second transformer is OEP branded, designed with EL34 in mind.
https://www.ebay.co.uk/itm/16490821...eyvgl_xSMK&var=&widget_ver=artemis&media=COPY
https://www.ebay.co.uk/itm/16490821...eyvgl_xSMK&var=&widget_ver=artemis&media=COPY
@snapper, thanks for the correction - I missed the monoblock part. Then those PTs would work fine for heating a EL34 Baby Huey monoblock each, if the other issues are addressed.
@jcalvarez, I’m puzzled by the OEP transformers‘s design choices. The V78A01F is mentioned for use with EL34 at 5.6 k primary, but with 24.5% Ul ratio. It would work with EL34, but not ideally - lowish power at 25 watts, rather high primary and unusually low UL ratio for EL34. Yet, their V29A06F (intended for EL84 and 6V6) has 10k primary (good), but 43% UL ratio (high for EL84).
But as @6A3sUMMER pointed out, speaker loads are not a constant, so these OEP transformers might perform well under dynamic music loads at these “unusual design choices”.
@jcalvarez, I’m puzzled by the OEP transformers‘s design choices. The V78A01F is mentioned for use with EL34 at 5.6 k primary, but with 24.5% Ul ratio. It would work with EL34, but not ideally - lowish power at 25 watts, rather high primary and unusually low UL ratio for EL34. Yet, their V29A06F (intended for EL84 and 6V6) has 10k primary (good), but 43% UL ratio (high for EL84).
But as @6A3sUMMER pointed out, speaker loads are not a constant, so these OEP transformers might perform well under dynamic music loads at these “unusual design choices”.
@Francois G To be honest I have never used them. They recenly upped prices and I can get Hammond delivered to the UK for less. As you and @6A3sUMMER mentioned, one thing is a pure 8 ohms resistive load, and another a real speaker in a room. The last step of testing an amplifier is the listening bit, and unfortunately it includes speakers 🙂. I've read reviews about phenomenally sounding amplifiers sporting a 5% THD at nominal output power. You never know😀.
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Quick easy Listening test idea:
Put a single Hammond output transformer, and a single EOP output transformer on a wood board.
Wire one mono-block to the Hammond, and one monoblock to the EOP.
Then connect the loudspeakers to the mono-blocks. Move the loudspeakers close together, so they are acoustically in the same environment.
Now, use a switch to apply the left channel signal from a CD player first to one monoblock, and then to the other monoblock.
That provides quick A-B-A-B comparison of the two manufacturers output transformers.
Have Fun!
Put a single Hammond output transformer, and a single EOP output transformer on a wood board.
Wire one mono-block to the Hammond, and one monoblock to the EOP.
Then connect the loudspeakers to the mono-blocks. Move the loudspeakers close together, so they are acoustically in the same environment.
Now, use a switch to apply the left channel signal from a CD player first to one monoblock, and then to the other monoblock.
That provides quick A-B-A-B comparison of the two manufacturers output transformers.
Have Fun!
I've found those percentages very depending on working conditions and only true if UL is the only local feedback applied to output tubes.
With multiple local feedback paths like the BH, standard UL rules are not strictly true.
EG IMO higher B+, less steep loadlines, lower UL, higher a-g1 feedback and higher driver gain is preferrable to get good DF, high power, euphonicity and good sensitivity.
25W is too low for an EL34 PP amp. From a pair of those those you get approximately 35 to 50 Wrms.
With a 5.6k Raa, to stay within 25 Wrms you need not to exceed 300V B+ (and get around 12 Wrms in "class A").
That's the EL84-6V6GT territory: you should get around 20 Wrms from a PP of EL84 with that output transformer and a B+ of 340V.
Because the OPT's in this case fit better with the EL84/6P14P it is also possible to use them with the BH-EL34 PCB.
The socket adapters required for this are difficult to find and also very expensive.
I designed my own DIY adapter PCBs for this some time ago.
If you are interested on this PCB´s please PM
The socket adapters required for this are difficult to find and also very expensive.
I designed my own DIY adapter PCBs for this some time ago.
If you are interested on this PCB´s please PM
Attachments
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