Bijou All Tube Futterman Headphone Amplifier - Page 164

*Slap forhead*

So I took the last couple hours and paralleled a lot of different resistors to try to get 98v. It has dawned on me that my voltage report is backwards. Should be:

6N6P-I pins 1-9 in order: 249.5v, 74.5, 124.9, 6.45v (ac), 6.45v (ac), 122.6, 4.1, 2.17, shield
6aq7: 199.5, 93.3, 97, heat, heat, 93, 0, 3.1, 0

6N6P-I: 249.7, 74.4, 125.0, 6.47, 6.47, 122.8, 3.4, 2.17, 0
PCC88: 196.2, 99.8, 103.0, heat, heat, 99.8, 0, 2.98, 0

I also killed my DAC yesterday. I should stop while I'm ahead.

Thanks for the help. A lightbulb went off in my head once I saw all the voltage readings. With the voltage on V1's plate at about 200v I don't think increasing the bias is needed without possibly shortening the life of the tube.

My next question. The voltage for Pin 6 on the PCC88 seems about right on target. The 6aq7 is a bit low, but is it allowable or is 98v truly optimal?

I'll likely need a resistor value greater than the 2k to get 98v.

LOL. It happens.

These voltages mean that you're going to need regal's mod to get a more lush sound from the amp. The 6bq7 plate voltage is ok. I wouldn't sweat it too much, particularly if you're planning to make the mod.

But, as you say, to get to 98V you'll need slightly more than 2k. Maybe 2k4 would do the trick.

58mm stainless volume knobs being manufactured from 62mm x 12" round rod.............

Alex, I was wondering if you would mind talking about the pros and cons of using a dual triode as a 'stereo' two channel tube (ala CTH) versus using it as a 'two-stage' tube with one tube per channel (ala Bijou and SOHA II)?

After building the CTH, I am impressed with the sound quality with both channels of the input stage being shared by a single tube. Is there such a thing as crosstalk within a dual triode?

I bring this up here because I am contemplating doing the Bijou as a PTP build, and was considering a topology where one tube would handle both channels of the input stage, and one tube would handle the job of phase splitting.

Any thoughts on this notion, or should I just stick to an equivalent topology of your single channel boards?

Edit: Just to clarify my thoughts a bit, I got to thinking about this with the idea that you could roll input tubes (like on the CTH) independently of the phase splitter tube. I began to wonder if there could be an interesting level of control and 'boutique' tweaking by dividing the two tasks into separate tubes...

Interesting you should ask this. My proto PTP Bijou does exactly what you want to do. The input stages are in one tube and the phase splitters in another. I don't think this generates any significant crosstalk and is a much easier way to do the PTP.

Mini Review: Bijou vs Soha II.

Source = Flac > camrbidge audio Dacmagic > silver interconnects.
Phones = Recabled hd650's (old, not silver cloth version).
Bijou tubes = amperex bugle boys 6dj8 + 6n6p
SohaII = amperex bugle boys.


Let me start by saying these are both very capable amps, both have their strengths. They have a different sound signitures, very different indeed.

Main differences:

The bijou is a much bigger sound and is slightly darker than the SohaII. Somehow the bijou gives a massive soundstage and creates a 3d holograph of the music. Tracks such as myriad harbour by the new pornographers creates music that reaches way past the headphones, sounding much like a good pair of distant speakers.

The SohaII's strength is the tight tight bass. bass tunes become stunningly clear, more so than the bijou. Its tight, but it still drops deep. It really excels on electronic music / R&B / Pop / dance. The bijou can sound slightly lose in comparison.

Treble, the bijou has a gorgeous fluidity, its very 'tubey' and imparts a lushness. Stick on Bon Iver "for emma" and you can drift away with the music. The SohaII is definately brighter than the bijou, its not overly bright but it certainly turns the hd650's into a quick sounding phone which is a feat on its own. The SohaII has a cooler signiture.

summary:

Bijou: huge lush sound, typically 'tubey' but certainly not muddy or muffled. Think of like a big rolls royce, effortlessly turning the roughest roads into a nice journey.

SohaII: quicker, more agile, brighter. IT sounds more solid state to my ears, potentially truer to the recording. However, it shows up poor recordings.

I would be happy to have either amps, they are both superb and in a way compliment eachother well. For me, the bijou is still the king of the cavalli's, you cant compete with the spaciousness it portrays, but the SohaII is snapping at its heals, and in a sprint leave the old man flagging. If i was going to listen to LCD soundsystem the sohaII woudl be my choice, if norah jones then it would be the bijou.

Both amps get a massive thumbs up - and thanks goes to alex.

Thank you for taking the time Adamus! While many of us don't have both machines in our stables, we gain some valuable insight with your head to head comparison!

Thanks for the review Adamus. It just helped me confirm that I need to build both of them.

no probs chaps.

Got to say, i am listening to the sohaII with 8416's in. Its very responsive to tube rolling, the 8416's are lovely.

So I was looking at the Bijou boards again and it seems like a pretty simple design with few parts. Death and smoldering corpses aside, is this considered an easy-ish build for a first venture into an all tube amp by an idiot? I'll be making an EHHA in the meantime so this'll be down the road a little. I've never had an all tube amp so figured this is as good as any to get on with (like I need any more DIY projects).

I am living proof. Get the psu done right, and there really is very little that can go wrong. Parts selection is the biggest variable.

Cheers, I'd be buying a glass jar kit so won't have to agonize ab out that aspect

adamus,
kudos for the review.

It was my first real tube amp and I'm still alive.

Just keep one hand in your pocket when there's HV on the boards, observe proper wire twisting and routing, and establish a good star ground and you'll be fine.

Adamus, thanks for the great review. I only have the Bijou at present but you have sparked my interest in looking into a hybrid.

smeggy, the Bijou is much easier regarding construction than many tube amps & Jeff's kit is comprehensive with good quality parts. I have constructed many tube & SS amps over the years so whilst it wasn't a technical challenge, the enjoyment factor was as good or better than far more complex builds. OTOH, the sound is unquestionably better than ANY of them. I have seen very few amps that exhibit such elegant simplicity & the ways in which some difficult technical challenges of the Futterman design have been overcome (eg. requirement for multiple PS & bias) are extremely neat.

IMO, it would be very difficult to find a better tube am design to start with. Go for it.