Pink Triangle THE PIP

Hi folks!

Does anybody have the schematic of Pink Triangle's THE PIP or the PIP 2 ?

I remember listening to the PIP2 a long time ago and found it very good - a phantastic battery powered amplifier with a very unusual look.
I also remember a HifiNews article rewieing this item vaguely ( it consists a transconductance amplifier and passive riaa).
It seems for what reason ever PT discarded the product early, it was no great succes (which does not say anything about sound quality).

Any deeper knowledge ?

The PT preamps were rather legendary devices - there were a
couple of very positive reviews, and several reviewers (Paul
Miller, in particular) used them as references, but it was
always hard to get hold of one to listen to, and they were
also pretty expensive. Mind you, their POP power amps were
of at least another order of unattainability; I saw one at a
show and a picture of one on their website, but never heard
of anyone who had actually heard one, nor were they ever
reviewed, to my knowledge.

I gather that the PIP's phono stage used a current amplifier
on its input, as (many years on) did the Linn Linto, but I
don't have any more information than that.


When I was at Essex University ( A LONG time ago ), one of my colleagues in the Audio Research department took the PIP to pieces, to see how they had got it sounding so good. We all sat around and had a good laugh at the sight of a single transistor gain stage. After all, we were all knowledgeable engineers , who KNEW that you needed current mirrors, and dual differential this and that to make a good amp!

I don't have the schematic anymore, but it wasn't very different to Nelson Pass' unbalanced line stage. PT were way ahead of him.
I recently searched through my attic (!) and found Paul Millers review about the PIP2 in HiFi-News, September 1988. - Sometimes it is good that we do not throw away everything "old and used".
It contains a relativly long and detailed description (which I have not been able to understand it fully) about this preamp and some photographs.
There is even a photo from the inside of the amp on the cover of the mag:
One can see quite many different transistors, some high power types, lots of LEDs, probably for current sources. This must be the linear gain stage, because the board is on top of the main board with the riaa stage(s) and the input switching. I can also see two big caps (3.3mf Roederstein MKP) and several tantal pearl elctrolytics (!), ELECTROL and SGS relays and two TL071CP (maybe for offset control).

But you mentioned a single gain stage like the the BOZ from Nelson Pass?
This really does not look like one to me.
It looks more like a all symmetric amp with current mirrors and sources and a ClassA output stage.

Now my interest in getting more information is even greater than before.
( You, folks, know that fever probably. )

Can you, Asibbald, get hold of the schematic you had once again ? That would be great ! I AM VERY CURIOUS NOW !

hoping for more news

Btw, I once (1989) wrote to PT for a service manual because the austrian importer asked me to change the (probably) faulty accus, but they did not even respond. And I was not even able to open the bl**dy case (which is rare - I used to get everything open; I always look beneath the cover of electronic devices, it is an old and treasured habit ...)
Pip schematics

I don't have any chance of getting hold of the Pip schematics. I didn't even have the original, my colleague sketched it out on a pad of paper from inspection of the circuit components.

I suspect the Pip2 was a different beast. Certainly, I was at Essex long before the date of the review you mention, so perhaps they changed the design considerably in going from Pip1 to Pip2? I just don't know.

However, when I say a single gain stage, I mean just that. There were considerable numbers of other components which were dedicated to getting the operating point of the gain stage "just right", so don't get the impression that there was only 1 transistor in the case.

The reason I said it was probably similar to Nelson Pass' zen preamp is simply that there is a very limited number of configurations one can use with a single transistor. Any complication comes from what you feel you need to do to supply it with the appropriate voltage and current.
I may be able to help you with the Pink Triangle PIP2 The preamps were designed by my brother and the original designs were prototyped by both of us. I still have the original and have in fact just reinstalled it in my home system as an outboard phono only stage. I also have an early production PIP1. Although I am biased !! the designs were extremely good, their lack of commercial success reflecting that success in business is due to more than just having good product. Pink Triangle have struggled heroically for many years to establish themselves, but never quite made it into the mainstream.
The PIP2 took the design further by using a battery power supply to isolate the circuit from the deleterious effects of the line voltage. Although this added complexity to the overall design, the basic audio circuits still retained the original topology and elegant simplicity.
The design was certainly more than just a single transistor , and comprised of a transconductance amplifying stage feeding a passive RIAA deemphasis circuit, followed by a buffer. This configuration provided very high RIAA accuracy, high overload margin at all frequencies, and very low noise.
The multiple LED's were indeed used for biasing of current sources. They were very useful diagnostic tools when I was prototyping !!
It's a small world these days ! when were you at Essex? Both my brother and myself were there, him from '74 till about '85 and myself from '77 to '83, working first with Dr Malcom Hawksford in his audio research group (and also with Dr Fidler in the EE dept.) and then in the noise cancelling research group with Prof Chaplin. I then joined KEF and was there for 11 years, (becoming Chief Engineer under Laurie Fincham) before joining the brain drain and moving to the USA.
I haven't looked carefully at the Nelson Pass designs recently, so cannot comment on any similarities, but Nelson Pass certainly has his head screwed on right and is a very talented circuit designer. I will make a point of re-acquainting myself with his schematics.

I hope lohk will forgive this blatent deviation from the original topic of this thread. I would have emailed you had this been possible. You shouldn't have mentioned your time at KEF, then you wouldn't be pestered with these questions :). I tried to obtain the information from KEF a couple of years ago but there doesn't seem to be anyone there now who knows about the older drive units. I have two questions for you.

1. Do you by any chance have the full parameters for the Q200H Uni-Q drive unit? I have only the data published in the KEFKit brochure and have been unable to get anything further from KEF themselves.

2. I have two differing sets of datasheets for the earlier drive units (B139, B110, T27 etc), one set from the mid '70s and the other from the early '80s. Do you know when the design of the drive units, and hence the TS parameters, changed? This is of interest to a number of constructors who are still using these drive units.

it is surely great to get in contact with somebody so "close to the center" !

Yes, I would like to have the schematics, from both versions, please !! You probably still have got even more details, like - ehem - the PCB layout :)
Do you see a possibility to post it to the web somewhere? Please contact me direct if you please (and if you do not want to publish it in the net).

Great thing. I am glad that I brought up this topic.

Do you think it is possible to do a DIY version of the PIP or the PIP2 ?


ps: In which company are you working at the moment, if I may ask ?
I would like to inform you that I posted the mentioned HI-FI News article about the PIP II from September 1988 on my tiny website (link below).
As far as I know PT went out of business again - alas.

Andrew, please, now is the time to give us a glimpse about some circuit details!



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If the partial schematic in HFNRR is at all representative of the real PIP II, then I made something very similar in concept and design years ago, perhaps around the mid-80s. However, mine was based on a non-differential complementary JFET input stage, used complementary folded cascodes, had the RIAA network connected between the folded cascode collector node and ground, and with a cascoded complementary JFET output stage. And a DC servo was fitted.

I don't believe that there were any problems with it, and I do recall concluding that it was a design approach worth looking deeper into. I may keep the schematics somewhere, but as I said, it's been y-e-a-r-s.

regards, jonathan carr
PIP in trouble

Dear All,

What a wonderful place this is.

I have been the proud owner of PIP 11 three box since 1999 - i bought it secondhand within two hours of seeing the ad. I previously owned a pip 1.

Sadly due to a massive power cut on Sunday night my right hand channel has given out. I am useless with a soldering iron and based in london.

I desperately need some help with repairing it as am bereft without it.

If any of you can help I would really appreciate it. I note everyones interest in this rarer than i thought piece of hifi.

I would really like to help you with your PIP II - but I'm in Austria...

There is a small hole underneath the amp from where the main screw can be accessed. I have no clue what kind of screw, maybe some kind of Torx. You will need a longer than usual tool for that - I once did not succeed in opening one.
Maybe you can try to make a high res digital photo with a flash?

All in all I believe that your units should not be damaged to much by a power cut.

Can you post some images of your items, or send it too me that I can post them on my site?

all the best


PIP now on way to repairers - I have hope that all will be well.

I have a copy of the original manual and a review from HiFi Choice that I shall scanand send to you.

It will take a week or two as manual has gone to menders but promise it shall be done.

THank you for your thoughts nad offer of remote help - much appreciated.

Pink Triangle PIP

I notice Anthonyf has a problem with his PIP II. Can you tell me where you are sending it for repair ...only they need someone who is familiar with the amp, otherwise more harm than good will probably result. If you are able to remove the lids and inspect the reverse side of the PCB's for discoloration and residue buildup, power the amp with the lids removed and check that all the led’s are glowing as brightly as each other. Check components for discoloration?