[SonicTrance]

But i am not confident in ordering parts. Read: quality and suitable parts. 1.000 different types of resistors and caps.

I've used all Russian NOS film caps as per recommendation from @MrCurwen. He's very knowledgeable about these things. They are high quality and still cheap. All resistors , except in the psu's, are 1W carbon films, nice and cheap. No reason to go with "audiophile" caps or resistors in this circuit!

And a step by step tutorial is more or less needed.

We can help with that. Can you read a schematic?

Adored the pics of the silver unit a thousand times. In love....

Thanks!
I liked those chassis too. I need to build something in them again (the insides are ripped out now). Will need to get some new top plates though.

Maybe it's not done to ask, if not forgive me. But what is the approx BOM costs..

Very hard to answer. You can build this amp for very little money. It depends how much you're into aesthetics? Sky is the limit! Most expensive part for me was the balanced stepped attenuator. If you don't need balanced inputs you can just use a stereo pot. MOSFET's, transistors, caps and resistors are all quite cheap. You can also use cheap tubes as long as they're linear, like TV sweep tubes. One thing I bought cheap for the first amp (silver) was the tube sockets. That was a big mistake! They became quite loose after short period, not good. This time I spent more money on teflon insulated sockets with tight fit. Very happy with them!

 

[MrCurwen]

Detectit, don't be intimidated by the way a P2P build looks! IRL it's not as complicated. As Sonic pointed out it's actually less complicated. Also, if you're into it, there's the historical reason; this is how everything was made for decades.

As for component selection; the main rule is it's not that big a deal. Here are my recommendation.

For resistors, the most important thing is to observe correct wattage. Most resistors in these schems should be cheapest available 1W carbon film resistors, or 1W metal film. Either is fine, I always use carbon film myself. There will be absolutely no sound quality difference; go with the cheapest.

Capacitors;

1) 1.5µF / 160V types are K73 types. You can buy these off eBay very very cheaply. Buy a full box.

2) 250nF high voltage types are MBGO or any OMBG (these are the same cap type for different application originally). Very cheap, buy in bulk.

3) I recommend you just buy MBGO for the parafeed caps as well. Sonic uses 12µF, but 4 or 8 µF is probably sufficient. This is dependent on your load.

4) PSU electrolytics; go with the cheapest, but if you have lots of heat (very small chassis) I'd recommend you invest a couple of pennies for 105 degree versions.


OT's should be Hammond 125D or 125C. Either is fine, there will be absolutely no sound quality difference. 125A is also fine. There is no DC flowing thru the primary at all. Hammonds should be pretty easily available everywhere.

IRF830's can be bough in bulk (please do, you'll need them) via eBay for 14 euros per 50 or so. Get double or triple amount of what you need.

Same goes for 2N2222(A). Get a lot of these, they don't cost much.

For wire I recommend teflon covered wire because it is great to handle and doesn't burn when touched with soldering iron. It is a bit expensive though.


For tubes I recommend 6SL7 or 6SN7 and 6P31S for 8 pin. For 9 pin 12AX7 and EL81. There will be absolutely no sound quality differences.

If less gain is needed, E180F or 6J9P for noval input tubes.

Buy only the cheapest tubes.

You can achieve 96% of sound quality by just dumping the output buffer. You can leave room for it and add it later if you so wish. It really is a beautiful and great amp even without it.

Depending on your chassis choises, this amp can be built for 300 to 400 euros. If you leave the output buffer and go for the cheapest tubes and caps, 330 should suffice.

If you wish to save even further money, you can achieve 90% of the sound quality by making the input section single ended. I can provide easy instructions (schems) on how to do this. This adds a tiny bit of "tube sound" but the quickness, impact and realism is are still there. This simplifies building a lot, and cuts down on costs even further.

It might be worthwhile to make a set of schems that have as added text the component info (MBGO, K73, resistor wattage etc.).

 

[MrCurwen]

If you already have some tubes laying around, you can (probably) use them. Depends completely on the type. This circuit will sound very good with even less-than-perfectly-linear tubes like 6V6GT for example.

 

[SonicTrance]

3) I recommend you just buy MBGO for the parafeed caps as well. Sonic uses 12µF, but 4 or 8 µF is probably sufficient. This is dependent on your load.

I actually use 4µF in the new amp as I needed to use the 400V caps. No room for more capacitance. Not needed as stated, frequency response is flat from 20Hz to 20KHz. I've no evidence (pics) of this but I did measure output amplitude from 20 - 20 000 Hz and it stayed about the same.

It might be worthwhile to make a set of schems that have as added text the component info (MBGO, K73, resistor wattage etc.).

I can do that and update first post!

 

[SonicTrance]

First post is now updated with schems with component types and values.

 

[Maxx134]

Most expensive part for me was the balanced stepped attenuator

Ok can you link me that stepped attenuator?
I did look into this a year ago with the little dot but I like that you did all those resistors yourself haha

 

[SonicTrance]

Ok can you link me that stepped attenuator?
I did look into this a year ago with the little dot but I like that you did all those resistors yourself haha

Here it is: https://www.hificollective.co.uk/ca...ed-attenuator-metal-film-resistor-p-9287.html
I got the Elma switch in kit form. They do sell it built as well for an extra £30.
The switch feels very good when changing volume. One thing I don't like though is that there sometimes is a pop when changing volume. I've soldered an extra 10M resistor in parallell with the output of the attenuator, so from each 6C8G grid to ground. That completely removed the pop when there's no signal. It sometimes still pops when changing volume with music playing.

 

[SonicTrance]

Come on guys! Get to building! Or is someone secretly building without posting? Then post! I wanna see!

Listening to my amp now as I'm prepping a chassis to build the SE version of this amp. Gonna be interesting to compare the two!

Inspirational pics:

 

[Maxx134]

I've used all Russian NOS film caps as per recommendation from @MrCurwen. He's very knowledgeable about these things. They are high quality and still cheap

Alot these russian caps are actually at a higher than average level (!).

I would say as good as the best mundorf caps.
If I didn't hear it myself I wouldn't have believed it.

Very hard to answer. You can build this amp for very little money. It depends how much you're into aesthetics

I good way to see how much all will cost,
is creating a project-parts list in the Mouser website.

 

[SonicTrance]

Alot these russian caps are actually at a higher than average level (!).

I would say as good as the best mundorf caps.
If I didn't hear it myself I wouldn't have believed it.

Yeah, and as soon as you put a source follower, like grid driver or power buffer, directly after the cap, the cap becomes transparent! If good quality of course. I couldn't hear any difference between the russian KBG and Mundorf S/G/O's.

 

[bloodhawk]

Come on guys! Get to building! Or is someone secretly building without posting? Then post! I wanna see!

Listening to my amp now as I'm prepping a chassis to build the SE version of this amp. Gonna be interesting to compare the two!

Inspirational pics:

I really want to start building one. But im moving soon, so ill probably do it around the end of July.

Will riddle you and McCurwen with questions lol

In the mean meantime, how much did the parts cost? (Minus the cost of the chassis)

 

[SonicTrance]

I really want to start building one. But im moving soon, so ill probably do it around the end of July.

Will riddle you and McCurwen with questions lol

In the mean meantime, how much did the parts cost? (Minus the cost of the chassis)

Please ask questions!

Parts dont cost much. Do like Maxx said and make a cart at mouser for example. The russian caps you get from ebay are also cheap.

 

[bloodhawk]

Please ask questions!

Parts dont cost much. Do like Maxx said and make a cart at mouser for example. The russian caps you get from ebay are also cheap.

Oh trust me there are going to be many! Now that i maxed out my MKVI+, i really am itching for the next DIY build.

Are those Teflon sockets btw? I recently used Teflon Octal and Nine pin sockets and oh boy are these amazing.

Gotcha, on it!

 

[SonicTrance]

Oh trust me there are going to be many! Now that i maxed out my MKVI+, i really am itching for the next DIY build.

Are those Teflon sockets btw? I recently used Teflon Octal and Nine pin sockets and oh boy are these amazing.

Gotcha, on it!

Yes, the sockets in the amp with 6c8g and 47's are teflon. Feels high quality compared to ceramic sockets.

 

[SonicTrance]

Listening to my amp now as I'm prepping a chassis to build the SE version of this amp.

A little update on the SE amp build!

I'm reusing one of the silver chassis I used in the first LTP build, since that amp was in pieces anyway, and I really like the look of that chassis!
This is what I had to work with. Fortunately I have two so I can mix panels from the two to minimize drilling and unnecessary holes.

Some new holes drilled and old superglue residue has been grinded off.

Tube sockets and transformers mounted! As you can see there're two loctal sockets. The amp will be C3G input and 6BG6/6P7S output. The rectifier socket in the middle will not be used for B+, but I have a plan for it!

I like the new more "busy" front plate. New additions are toggle switch to switch between speaker and headphone output. And the SE headphone jack since, well, SE amp. Will probably only use the XLR output jack anyway but nice to have both. Also gives the opportunity to listen with two headphones simultaneously.

RCA inputs and speaker outputs added to the back panel. I don't plan to have a switch between the RCA and XLR inputs, so I can only use one at a time but that's all I need.

Here's an experiment I did with the B- supply. I first built the filter using a 42 VAC PT and voltage doubler filter and this is what I got after the regulator:
The filter had about 8mV of noise but after the regulator there was 80mV of ripple.

While the above ripple probably wont hurt anything in a constant current draw amp I wanted to less noise out of principle. So I decided to get rid of the voltage doubler circuit and changed the PT to 115 VAC.
Here're the results:

Reg output on the left, filter output in the middle and AC ripple on the right.

I'm very happy with 3mV of noise. For some reason the two FET regulators doesn't seem to like voltage doublers.
Those outputs are unloaded btw. Under load filter output should be around -125V and reg about -100V.