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DIY TUBE PREAMP HELP PLEASE

I'm using 90db speakers right now with a 3.5wpc tube amp. It gets loud enough.
Not shaking the windows loud, but louder than I usually listen at.
I do have problems using less efficient speakers around 84db to 86db in larger rooms though with my flea watt amps. For near fields or in the small 9'x10' room I have several small amps setup in the less efficient speakers do ok.
 
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I think for me the best way to go is with a tube pre amp because i can turn off the tube sound when i want, i can just turn off the tube pre amp and run the amp only, then i have options.
 
I kind of like the rectified DC heaters. I dont know much about the output tubes used though. It uses output tubes with anode caps, so you would have to be aware of the high voltage going to those anode connectors. I see the kit comes without capacitors for that price. You would have to order your own or pay more if they send them. Also that price doesn't include the power transformer. That's going to be the big cost. It will be the price of the power trany plus a lot in shipping due to the weight. You would have to ask the seller what transformer is used for it and see if the price would he worth it. Then there is getting a chassis to fit it all in along with measuring, drilling and punching all the holes needed to mount everything. Plus a power socket, input-output jacks added, volume control, board stand offs, wire, etc. It can add up fast.
 
Never seen a tube amp with the wires coming out going to the top of the tube don't think I would like that look. The sellers never answered me I've emailed him for 3 days and he's never replied to me trying to find out what kind of power it puts out I don't buy stuff from people that don't reply to their emails.

I don't mind making my own enclosure and drill in the holes and all that. Guys just a terrible eBay seller. It's okay I got my eye on a couple other things.

Thank you very much for your replying for taking a look at that.
 
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Califmike33 said:
what do you guys think of this layout, its a DIY headphone amp. Its a diy kit on ebay.
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Califmike33 said:
The sellers never answered me I've emailed him for 3 days and he's never replied to me trying to find out what kind of power it puts out I don't buy stuff from people that don't reply to their emails.

I don't mind making my own enclosure and drill in the holes and all that. Guys just a terrible eBay seller. It's okay I got my eye on a couple other things.
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If you're looking for a headphone amp, I'd suggest that you ask for advice on some of the various headphone forums rather than making a decision based on random listings that you find on eBay or Aliexpress.

Chinese eBay / Aliexpress sellers who have stuff like this listed are just selling a product that they obtain from a wholesaler. They generally lack any technical knowledge and they have probably never used or heard anything that they sell. And then there is the language barrier. If someone sent you a question in Chinese would you be able to respond?

Most headphone forums, like the one here on AK or Audio Asylum, are probably geared more toward finished products rather than DIY, but you might find something. The most obvious place to check would be DIY Audio. I took a very quick look and found this, for example:

https://www.diyaudio.com/community/threads/list-of-best-diy-headphone-amplifiers.308751/

There are probably many similar threads there and elsewhere. That said, most of the folks at DIY (the DIY Audio forum, not this board on AK) are highly technical "engineering types" so you may not find too may suggestions that are based on cheap Chinese circuit boards. Many designs will be SS and many suggestions will be very expensive. Have fun wading through it all.

But didn't you say you already have an OTL headphone amp? Or is that amp designed to run speakers?

I'm not very familiar with headphone amps but I know that a lot of them are OTL designs that use tubes whose output impedance is very low so they can match up with headphones (whose impedance is higher than speakers) without the expense of using OTs. OTL amps designed for speaker use generally use lots of tubes in parallel (sometimes dozens) in order to lower the output impedance enough to match the speakers.

Of course, there are also OTs which have secondaries that are geared toward headphone use. And headphone impedances vary widely too, which complicates matters so it kind of depends on the specs of your headphones. Most speakers are nominally 8 ohm but there seems to be a wider variation when it comes to headphones.

Again, not my thing, but I think this is relatively accurate. :dunno:
 
Califmike33 said:
I think for me the best way to go is with a tube pre amp because i can turn off the tube sound when i want, i can just turn off the tube pre amp and run the amp only, then i have options.
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From what you've said, your chassis fabrication skills are probably much better than mine. The chassis is the hardest part. If you use point to point you can very easily make changes to the circuit if there is a problem. So, yeah, just build a preamp.

As I've said previously, Stephe's videos offer a detailed, step by step, look at what's involved. Those basic layout and construction procedures can be adapted to pretty much any build. Or breadboard something first and then transfer it into a chassis later if you like it.
 
That's a good idea to ask in the headphone forum here on AK. Someone there probably knows of a kit that works well. I thought about building a headphone amp, but in the end I just bought one. It has output transformers as well with an impedance selector. I really took a chance on it when I bought it.
It was part of a limited run line of various small Chinese SE amps. 10 each if I remember right.
But it turned out great in the end. It uses a switch mode power supply so it can be plugged into anything from 90v to 230v to power it. The power supply is in its own shielded enclosier on top and well filtered.
 

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Thanks guys for the advice I won't be buying that headphone amp I don't like the wires that go to the top of the tubes and the dude never answered me on eBay so that's over with.

I do have an OTL headphone amp right now then I'm not liking. So mainly I'm still looking to build a preamp kit is my main goal been doing a lot of research on it.

I did talk to Steph and she said that the headphone box should work no matter what the ohm of your headphone is.

But to be honest with you I'd rather be able to just plug my headphones straight in so the goal is is to get a good amplifier that has a good headphone jack and build a tube preamp.
 
Okay so I just bought this kit off of eBay,. I'm going to put my own capacitors in it I'm going to order high quality capacitors. I also have the transformer coming with it the seller has the transformer that it needs to run off . I know I still need a volume a case and other things but I'm going to build all this circuitry first to get practice in and to learn how to do this comes with a schematic I'm practicing how to read a schematic so I think it's a cheap starting point.

https://www.ebay.com/itm/1930703534...ar=493260105665&widget_ver=artemis&media=COPY
 
Its nice they listed a transformer to use with it. Some don't. 6SN7's are one of my favorite driver tubes. Tung-Sol 6SN7's sound nice and won't break the bank.
I use them in my Aikido preamp.
 

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Califmike33 said:
Okay so I just bought this kit off of eBay,. I'm going to put my own capacitors in it I'm going to order high quality capacitors. I also have the transformer coming with it the seller has the transformer that it needs to run off . I know I still need a volume a case and other things but I'm going to build all this circuitry first to get practice in and to learn how to do this comes with a schematic I'm practicing how to read a schematic so I think it's a cheap starting point.

https://www.ebay.com/itm/1930703534...ar=493260105665&widget_ver=artemis&media=COPY
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Should be a fun project and a great learning experience. Be sure to keep us posted.

Looks like a pair of 6SN7s for each channel with their sections in parallel. I'm not very familiar with that topology but I think it's called a mu follower. One tube is configured as a cathode follower - the output is taken from the cathode - so the output impedance should be low and suitable for SS or Class D.

Heaters are DC and run in series, so 12v. I've never had issues with running indirectly heated tubes with AC, which is much simpler. Nothing wrong with DC but I only use it with directly heated tubes.

Looks like the heater supply voltage is regulated so your heater voltage should be OK even though the PT has a 115v primary. Actually, the whole PS is voltage regulated and uses SS rectification.

I'm a simpleton, so it's way more complex than anything I'd build. It's obviously not a clone, more of an "inspired by" design. If it was a clone it would be even more complex! Here's a pic of the real Rogue 99:
Rogue 99.png
 
I've run both DC and AC heaters on indirect heated tubes. I can't really say I noticed any difference or benefit with one over another. Regulation is nice though. My Aikido uses DC regulated heaters. My 300B of course uses DC regulated heaters. Only one other amp I have uses DC heaters and that's my SE sweep tube amp. All the rest are AC.
 
Looks like a decent kit and I got the transformer I got everything I'm going to put good quality parts in it and I should be on my way I'll probably be calling on you guys cuz I'm sure I'm going to get stuck.
 
Just get better electrolytics and film caps. I haven't had any issues with Chinese metal film resistors. They've always tested fine.
One thing to remember, if you want the tubes exposed through the top of the chassis, mount all the parts except the sockets on the bottom side of the board paying attention to orientation.
 
Can you tell me some of the really good brands to get I mean I know a few of the good brands but throw me a few names out like what is the best parts I can buy what is the names?
 
Everyone has there favorite go to film caps. I never spend big money on boutique brands mundorf aluminum foil in oil caps are nice. I've used them and that's what's in my main preamp. Russian paper in oil caps sound good also.
I have them in one stereo tube amp and a couple 125 watt tube mono blocks.
As for electrolytics, Nichicon, Kemit, Cornell Dublier, United Chemcon, Panasonic, etc. If there are any small film caps, that usually l9ok like little squares or rectangles, Wima stack film polypropylene caps are a good choice.
I usually order from Mouser and Digikey. I usually order my Mundorf film caps from Partsconnexion. Great little company and good folks to deal with.
 
Thanks for that list that's going to help me a lot. Going to get all caps and everything with the kit and keep what is good and change what is bad.

I want to get my parts list and order now before the item arrives. Stupid question, what affects the sound the most? Capacitors, Coupling Capacitors, what else? should i just replace everything except the transistors?

Edit, went on mouser.com, and tried to get parts, 100uf 450v, don't know diameter, do i need all audio grades? i have no idea what I'm doing.
 
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Wait until the kit arrives. Not knowing the cap values, lead spacing and diameter, it wouldn't be a good idea to order yet. The resistors will be fine, no need to replace them. But when you do order you want to use 105° electrolytic caps whenever possible. They'll hold up to heat better than the 85° caps.
Especially with any near hot running regulators and tubes.
 
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