That's great advice. You may need a lot less amplifier power than you think.
Longtime member Pano posted an interesting guide for estimating how much power you really need from your amplifier(s):
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
When I followed his procedure, I found I needed about 4 volts rms of swing into my 4 ohm speakers, at absolute maximum.
That's 4V RMS squared = 16 divided by the 3.6 ohm speaker DCR = 4.44 watts at the very most.
I figured double that power for headroom's sake and 8W per channel should do it for me with room to spare.
However, I live in an apartment so I can't blast sound, and my listening room is of modest dimensions. My speakers' sensitivity is about 90dB/1W/1m and I listen to them at only about 1.5 meters distance (pretty much near-field).
The Hashimoto HWC-30-8 does have UL taps.
https://www.acoustic-dimension.com/hashimoto/datasheets/Hashimoto-HWC-30-8.pdf
Longtime member Pano posted an interesting guide for estimating how much power you really need from your amplifier(s):
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
When I followed his procedure, I found I needed about 4 volts rms of swing into my 4 ohm speakers, at absolute maximum.
That's 4V RMS squared = 16 divided by the 3.6 ohm speaker DCR = 4.44 watts at the very most.
I figured double that power for headroom's sake and 8W per channel should do it for me with room to spare.
However, I live in an apartment so I can't blast sound, and my listening room is of modest dimensions. My speakers' sensitivity is about 90dB/1W/1m and I listen to them at only about 1.5 meters distance (pretty much near-field).
The Hashimoto HWC-30-8 does have UL taps.
https://www.acoustic-dimension.com/hashimoto/datasheets/Hashimoto-HWC-30-8.pdf
Nelson Pass said he did that for customers to show little power they were actually using.
Nice, I did this in the past but I should try it again.
I only have an older Tek oscilloscope, so might have to do the same as the Nelson Pass demos.
My listening room is of decent size, about 23x13 ft and is fairly isolated.
I've built both the Ekta mk2 and the Faital 3WC, and have invested far too much into them to think about more speakers in the foreseeable future, so should plan around those.
The Ekta are 4ohm @ 87dB and the Faital are 8ohm @ 93dB, never going below 5ohm.
That said, I had asked TG in the past about low power tube amps and he replied:
"The Faital-3WC-12, despite its high efficiency, still has a 12” bass driver that like a bit of power to fully excel."
So what I'm thinking is to perform this test, and finish the SPP build with the Sowters, which I already have all the parts for.
Based on its performance, I can gauge the power requirements.
Ironically, my current amp is the Benchmark AHB2 (which I will keep regardless), and is probably the polar opposite of a tube power amp.
I only have an older Tek oscilloscope, so might have to do the same as the Nelson Pass demos.
My listening room is of decent size, about 23x13 ft and is fairly isolated.
I've built both the Ekta mk2 and the Faital 3WC, and have invested far too much into them to think about more speakers in the foreseeable future, so should plan around those.
The Ekta are 4ohm @ 87dB and the Faital are 8ohm @ 93dB, never going below 5ohm.
That said, I had asked TG in the past about low power tube amps and he replied:
"The Faital-3WC-12, despite its high efficiency, still has a 12” bass driver that like a bit of power to fully excel."
So what I'm thinking is to perform this test, and finish the SPP build with the Sowters, which I already have all the parts for.
Based on its performance, I can gauge the power requirements.
Ironically, my current amp is the Benchmark AHB2 (which I will keep regardless), and is probably the polar opposite of a tube power amp.
If you decide that an amplifier built around the Hashimoto transformers you have will not work for you . . .
Then sell the transformers to me.
Seriously!
Ask the vendor of your speaker: What does a 12 inch driver have to do with efficiency, one way or the other (it can be one way or the other, but not just because it is 12 inches).
I recently listened to my 2 Watt balanced amplifier drive a 15 inch in a modified Altec A7 cabinet, 100 pound multi-cell horn with a combiner for 2 drivers, and a slot tweeter.
Just because the woofer was 15 inches, did not mean it needed more power.
Only three things keep me from owning a pair of such speakers, too hard to obtain, too heavy for the upstairs living room floor, and too big for the small living room.
Those balanced 2 Watt mono-blocks are in my living room, driving ProAc Tablette Signature 2000 speakers (87dB sensitivity).
I modified the Tablette's crossover slightly.
Sounds good to me.
I hope you are able to sleep at night; not staying awake worrying about amplifier power.
Of course there are recordings of pipe organs 32 foot pipes, and the Telarc recording of the 1812 Overture, with the 6Hz real cannon shots.
Then sell the transformers to me.
Seriously!
Ask the vendor of your speaker: What does a 12 inch driver have to do with efficiency, one way or the other (it can be one way or the other, but not just because it is 12 inches).
I recently listened to my 2 Watt balanced amplifier drive a 15 inch in a modified Altec A7 cabinet, 100 pound multi-cell horn with a combiner for 2 drivers, and a slot tweeter.
Just because the woofer was 15 inches, did not mean it needed more power.
Only three things keep me from owning a pair of such speakers, too hard to obtain, too heavy for the upstairs living room floor, and too big for the small living room.
Those balanced 2 Watt mono-blocks are in my living room, driving ProAc Tablette Signature 2000 speakers (87dB sensitivity).
I modified the Tablette's crossover slightly.
Sounds good to me.
I hope you are able to sleep at night; not staying awake worrying about amplifier power.
Of course there are recordings of pipe organs 32 foot pipes, and the Telarc recording of the 1812 Overture, with the 6Hz real cannon shots.
Last edited:
This thread started more than 2 yrs ago. Any ordinary tech would have had something working with a plane Jane
circuit within a couple of weeks. Time to stop talking & do something.🙄
circuit within a couple of weeks. Time to stop talking & do something.🙄
jhstewart9,
The original Post # 1, by invaderzim was 05-19-21. invaderzim last posted on 07-15-21; and just dropped off the map.
Yesterday, itsikhefez picked up the thread with a new request, new oportunity.
Hopefully we will see something built by the new poster.
The original Post # 1, by invaderzim was 05-19-21. invaderzim last posted on 07-15-21; and just dropped off the map.
Yesterday, itsikhefez picked up the thread with a new request, new oportunity.
Hopefully we will see something built by the new poster.
@jcalvarez I took another look at the schematic and ironically the PT specified there, 372JX, is the one I have on hand that I planned on using. (not sure if thats what you actually used).
12AX7 instead of 6H9, OK.
For the 6H8, is 12AU7 adequete? The mu seems closer to a 6SN7 than a 6DJ8.
Do you mind sharing a pic of the internals of your build?
@itsikhefez Yes, I do use the components specified in that schematic, it is up to date. I have never used a 12AU7 for LTP. There are some concerns around here about the difficulty of balancing the LTP without a CCS in the cathodes. You can try and see what happens. I did some simulations, and you may need to increase R3 to 120K to avoid grid current in the 12AU7 at maximum power. With the 6DJ8 I also get lower THD. This is the result of simulations, I have not tried either tube for real, therefore your mileage may vary.
Here is a picture taken when one channel was built, I have none with both channels. Not a work of art, but it works 🙂
Here is a picture taken when one channel was built, I have none with both channels. Not a work of art, but it works 🙂
Dear jcAlvarez, I'm searching for a reliable project using the 6P3S-E tubes. Do you know where I can find detailed information about your build? Thinking of using the TTG-EL34PP OT's from Toroidy. Thanks and congratulations for your build!
Hi @framilopes
I do not have detailed step-by-step information about the build, here is some information:
The rest can be seen from the schematic, together with some pictures of the build in the archive here (https://drive.google.com/file/d/1iVY7IOD-ofe_KCSBb2Ul3BNMuNoIye_a/view?usp=drive_link).
I was a bit paranoid about noise from the power supply, I put both channels too far to the sides. If I would built it again I would put them a bit away from the sides. Also I would include just one 6H9C shared between channels, and of course, improve my point-to-point wiring skills 🙂.
I do not have detailed step-by-step information about the build, here is some information:
- Loosely follows Eico HF-89. The manual is pretty useful: https://www.audioservicemanuals.com/e/eico/eico-hf/eico-hf-89/234716-eico-hf-89-owners-manual
- Hammond transformers: Power transformer 372JX, output transformers 1650HA (Digikey UK)
- Hammond Aluminium Chassis 1444-30, 432 x 254 x 51mm (e-bay UK). The chassis is reinforced with an angular aluminium strip to be able to handle the transformers' weight.
- Tubes: 4x 6P3S-E, matched quad, 2x 6H8C (matched pair), 2x 6H9C (matched pair). (in reality you only need one 6H9C, but originally I had plans to add tone control, then I decided against it, that is the reason you see two 6H9C in my build)
- Belton octal sockets https://www.hotroxuk.com/belton-8pin-socket-vt8-st.html
- 100+100uF 500VDC capacitor can. Chosen just for the looks, there are better options.
- Rubber grommets for transformer cables.
- Binding posts for speaker connection.
- Insulated RCA input sockets.
The rest can be seen from the schematic, together with some pictures of the build in the archive here (https://drive.google.com/file/d/1iVY7IOD-ofe_KCSBb2Ul3BNMuNoIye_a/view?usp=drive_link).
I was a bit paranoid about noise from the power supply, I put both channels too far to the sides. If I would built it again I would put them a bit away from the sides. Also I would include just one 6H9C shared between channels, and of course, improve my point-to-point wiring skills 🙂.
@jcalvarez, thanks a lot to share the detailed guide and photos. I'm planning to use turret boards to help the wiring organization. It’s time to source parts. I‘ll send updates.👍