You'll still have to deal with the microphony of the 4P1L. It's significant and very audible on the input stage.
You'll be extremely lucky if they have any in stock, let alone at that price. They've been off the radar for a while now.
OK Regal, just to test the spud and transformer idea I'm running it now, listening to Harry Belafonte.
No step up on the input, 4P1L running at 218V on the plate, bias -17.3V, 38mA. OPT is a ratio of 3.75:1 loading the tube at about 5.6K. See below. It works just fine. Enough volume without being crazy. For classical pieces that are recorded at a lower level I'd want more gain. Maybe a 1:2 step up at the input.
The main problem is hum. As the hum at the output stage is reduced only 11dB, it's fairly loud. Need to work on the PSU. From this I would say with the proper OPT, like 5:1 and maybe a step up at the input, the 4P1L spud works just great for 300 ohm cans like the Senhiesser SD series.
No step up on the input, 4P1L running at 218V on the plate, bias -17.3V, 38mA. OPT is a ratio of 3.75:1 loading the tube at about 5.6K. See below. It works just fine. Enough volume without being crazy. For classical pieces that are recorded at a lower level I'd want more gain. Maybe a 1:2 step up at the input.
The main problem is hum. As the hum at the output stage is reduced only 11dB, it's fairly loud. Need to work on the PSU. From this I would say with the proper OPT, like 5:1 and maybe a step up at the input, the 4P1L spud works just great for 300 ohm cans like the Senhiesser SD series.
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You'll have to mail him. He might not even want to build them. If you guys are really interested I'll send him an email tomorrow.
Verstuurd van mijn GT-N7000 met Tapatalk
You also need a good mechanical mount in order to avoid vibrations. Mounting tubes directly on the chassis = asking for troubles. Also forget tube dampers on the glass and other similar useless stuff...🙄
I think this is wishful thinking.
Few years ago one of my buddy paid 3000 Eur for custom wound line output transformer pair.
Sent mail to Bartolucci asking quotation for OPT SE 5K:300 ohms 15W 70mA, Bartolucci answered if it's only for a dedicated headphone amp can be reduced dimensions OPTs with best perfomance and low price. Power can be around 1W and current Idc reduced to 30mA or less?
N.B. I asked for 307A output stage.
N.B. I asked for 307A output stage.
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1W can be enough for headphone amp if you specify it correctly. This means that you need to specify the low frequency where you want that power. That's really important!
In general, when power handling is given without an associated (low) frequency this is 50 Hz by default (i.e. like supply trans).
1W at 50 Hz is not the same thing as 1W at 20 Hz. There is a big difference. In fact if you buy a transformer specified for 1W at 50 Hz it will not handle anything more than 0.15-0.2W at 20 Hz with acceptable distortion.....
A good rule of thumb for SE OPT's is to specify max Pout at 30 Hz, this usually gives best balanced perfomance (because there is high frequency behaviour as well on the other side) with acceptable size.
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You really need to try an SSH2, if you can hear any hum at all then it is negatively affecting the sound more so than just annoyance. Are you using coleman rges for the fiament ? Getting rid of the hum an you will be amazed at the overall sq improvement.
Thanks for the report, let us know if you find an input stepup transformer that works without sacrificing treble.
