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Valve Headphone Amp – Very High Quality. Condition is New (Prototype/development unit, see below)
Superb sound from a single ended class A amp using a pair of 12SN7 valves with output transformers, valve rectified by 6BY5, with a very high quality power supply. Sound quality is in the 3000 range, gorgeous.
Two things to say here. I’m not going to blow my fine reputation and FB with a false claim; and above all, any buyer is welcome to return the unit for a full refund so don’t be afraid to try it.
The amp is designed for low impedance phones 32 to 100 ohms and works really well with the superb Audio Zenith PMx2, AKG K812, AKG K712, Mitchell & Johnson JP1. They do work with Sennheiser HD580 Precision (600 ohms) but not really recommended for high impedance phones.
Output socket is XLR 4 pin, but I will lend an adaptor for 6.3mm jack if needed so the buyer can try the amp out. 4 way wiring via XLR is recommended. I might be able to lend the buyer a suitable headphone cable – feel free to ask, tell me what the phones are.
This is a prototype / development unit, brought up to the best configuration I found and little more than run in as I have 3 other very similar units. Here’s the long story. I didn’t find the right category in the new/used etc list . new seems nearest.
First, I have a lot of experience designing and building high end valve gear, preamps, phono stages and SET amps.
A few years ago I started using headphones, not very seriously, with a Tascam CD200 player with headphone out. Then came a Little Dot, not bad. Then I built an Elekit amp, that was better later improved with better components and wiring. That then proved better than X-can and a solid state 1000 unit in a shootout.
I learnt a lot from a Nobsound using 6SN7s paralleled into output transformers, some promise but not right. I put that down to the driver valve, ECC83, way too much gain and poor tone. So I reconfigured that for ECC82 and it was better; quite a lot better than the Elekit.
I had then learnt quite a bit and had a go at my own design, on the Piper chassis. 12SN7 paralleled driving a good single ended OPT, as this worked well in Nobsound! 12SN7 used instead of 6SN7 as the supply, and prices, are both better.
I used a 7N7 as driver. Two power supplies using film/oil caps and chokes. Results were good; really nice bass with resolution, tone.
I kept that as it was as a benchmark unit and built another. As it seemed the gain of the driver stage was not needed, I tried a TVC (transformer volume control) as it steps down the signal level but steps up the ‘drive’, enabling the input to drive the output valves without a driver or buffer stage. Technically it worked well but the sound didn’t seem quite right (this often happens in hifi !!!!).
Next a did a mod to Piper, bypassing the driver stage with a stepped attenuator, and that was it !
The problem with this config is the high resistance of the volume control gives a degree of ‘disconnection’ to the output valves; overcome by careful choice of attenuator value.
Sound quality was very good, I knew I had a winner.
Next I did a very similar new build but with more attention to the power supply. In a SET amp (which this is), the power supply is absolutely fundamental to sound quality. I have good success with film/oil motor run caps, low DCR chokes, multi stages, unregulated supplies so I continued to use this kind of supply. 6BY5 valve rectifiers (paralleled for low equivalent resistance); low DCR high quality chokes, 3 of them; 3 stages; Shizuki (ASC) final capacitor, one of the best type. PSU optimised (by modelling in PSUD) for stability with fast clean response, and very low ripple. This amp is as quiet as the grave. Superb sound, really good tonality, solid tight tuneful bass, and above all excellent female vocals which I love.
I did yet another build, exactly the same other than slightly different operating point for the 12SN7, which made no noticeable difference. I like to have a number of virtually identical units to do some tweaks in a meaningful way.
In an idle moment, I took Piper and brought it up to the standard of the others. As it’s a development unit there are a few odd things, like an unused valve base and some holes in the top plate which will be sealed before selling. As you see the top plate is Perspex as I had plenty! You may or may not like that, but with this amp it’s all about the sound quality rather than looks (but it looks OK in a cabinet).
So Piper is for sale . it is taking up space, doing nothing, and I’d like someone to be enjoying it (and OK, I’d like some money) 🙂
So that’s what’s here. Remember, when you buy professional hifi, a lot of the cost is funding the development process! Which is why I give the above info; it has been developed thoroughly, to professional standards.
Ladder type attenuator with good resistors; 3 stage PSU, choke in each stage, all film caps (no electrolytics in the PSU); simple 12SN7 parallel output stage (elna bypass caps) driving good OPTs rated for 32 ohms (works fine with 70 ohm AKG K712).
Note that 6BY5 rectifiers sound very good indeed and are cheap on ebay (c.f. metal base GZ34s at ).
Several good types of 12SN7 are out there – and they sound *good*.
With no driver stage it seems like less …but believe me, here ‘less is more’.
My own amp is to *exactly* the same spec. I use this with Pro-ject RS2-T transport, ANK Dac 4.1x (high level Audionote kit valve dac, gorgeous); Audio Zenith PMx2 planar headphones. The sound of this system is superb in every way; tonality, vocals, rhythms, musicality, tight tuneful bass, sweet natural top end. Very high end sound from one hell of a good system as I’m sure you can appreciate; and the amp is totally at home here.
I’ve also used Piper with the Tascam CD200, good sound but a slight edge from the CD player. And with my Cayin CDi100, parts upgraded, Tent clock fitted, good valves, and sound was really nice; none of that edge, sweet, musical just not quite as sophisticated as the ANK dac.
Do be prepared to buy – you can always return it if not satisfied, which I very much doubt.
It’s hard to price something like this. Not much new gear is this good – 3 good chokes and good OPTs were costly but worth it; hard to find this level in any professional gear at almost any price. Also, with no electrolytic caps in the main PSU, and with over rated transformers and chokes, reliability will be good. I’m not going to sell for less than the price of the parts so I’ve guessed a reasonable value. I won’t take silly offers, I know what this sound quality is worth.
Can be heard by arrangement, in south east Essex.
Safety: all components are run conservatively; caps at very well below rated voltage, resistors at a small fraction of rated power, transformers and chokes at no more than 50% of rated power. The negative sides of the output socket connections are earthed.
Dimensions:
Length of chassis 420mm, length of fascia 430mm
Depth of chassis 300mm, max incl RCAs and volume knob 335mm
Height 145mm
Fitted with brand new NOC Sylvania chrome dome 12SN7, and almost new 6BY5 (they last for ages).
Feel free to ask about anything.
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Category: Sound and Vision:Home Audio and HiFi Separates:Amplifiers and Pre-Amps
Location: Canvey Island