Now that’s also true Roger! I presume you’re not a fan of those 2 DIN plugs
Barrie
Well spotted Barrie! As George Washington is credited with saying “I cannot tell a lie!”, I am not a fan of them, or to be more truthful, I hate the b****y things!
An RCA/Banana is MUCH, MUCH more secure than one of those could ever be!
I’m talking from personal experience here!
Ranting Roger
Well said that man!
As you know, the speaker outs on the LEAK amps, are 2 pin DIN. I have the components now though to convert the speaker ends to banana sockets. Done already on the 2060’s, still need to convert the 600’s.
Barrie
YES, YES, YESSSS! That my friend is an up-grade long overdue
and well worth doing!
Roger
I would say the RCA plug isn’t ideal for speaker connections. They are designed for screened cable and not over easy to connect decent quality, two core speaker cable. Yes they do make a solid and secure connection though.
Banana plugs are undoubtedly the best option.
Perhaps I should amend my previously quoted DIN speaker plug pro to - Not reversible to an idiot proof level.
You’re absolutely right Paul! I should have made myself clearer!
Bananas for speaker connections, RCA for other connections!
DIN multi-pins OK for inter-connections.
DIN two pin speaker connections not fit for purpose!
The plugs tend to fall out of the sockets at the drop of a … two pin DIN speaker plug from its socket!
We did discuss this previously and the banana plugs were considered good for the amount of surface area for contact purposes, they are obviously very good in terms of being held securely in the sockets too, due to the design of the plugs. I currently have 2 x AIWA amps with bare wire spring connectors, 2 x LEAK amps with 2 pin DIN plugs along with the HITACHI music centre which also has 2 pin DIN speaker outs. The last amp I owned with banana sockets was the Pioneer AV receiver, actually a very nice piece of kit. Sold on here for next to nothing with a myriad of speakers including floor standers, bi poles, bookshelf, active subwoofer and centre speaker plus ATACAMA stands, quality interconnects etc, etc.
Mrs B didn’t like all the speakers and wires but I’m gradually reintroducing them into the lounge!
Barrie
So, I had a little time this morning, after taking dog out for big walks, attending to domestic duties, etc I got the second LEAK DELTA 75 amp out to have a look at transferring the chassis across into the original one. Four screws underneath each unit, frees the chassis and it can be drawn out from the front very easily
Three buttons on the new unit had been replaced at some point with”similar” but not OEM style buttons and the ON/OFF switch lever was also damaged on this unit. I swapped them over from the almost immaculate (cosmetically) original unit onto the new one. The ON/OFF lever came off easily using plastic trim tools I bought for the 5 the three buttons were slightly more difficult. The non original ones just pulled off the new unit but on the original amp, were glued in place. Judicious application of heat (courtesy of Mrs B’s hair dryer
) soon had the glue softened and off they came to be refixed onto the replacement chassis. All looking as good as new now!
Then the grandkids arrived so I’ve packed the original unit away and put the hybrid unit into the lounge until later. Here’s a picture of it finished!
Can’t tell from the pic but that fascia is milled out of solid 6mm aluminium plate! Beautiful piece of kit. The only thing I’ve not done, is actually test it! Am I right in thinking that with no speakers connected, it could cause damage to the amp? Thought I’d just wait until tomorrow at some point to connect everything up and do a proper test drive
On another note;
We‘re all going to the Christmas panto at teatime. It’s at the ALHAMBRA in Bradford, we’ve been doing this since our own kids were young and continuing now with the grandkids ( actually, its my cover story as I absolutely love going and I think I enjoy it more than the kids!) Billy Pearce starring again this year, 20 years for him this year I think Snow White is the panto
can’t wait!
Barrie
Won’t do any harm running without speakers connected. Just the same as turning the main and remote speaker switches to the off position.
Have fun at the panto.
I’ve always understood that turning on the amp with no speakers connected could cause damage - that is what I remember reading in the instruction book to my first ‘proper’ Hi Fi anyway. So consequently, I have never risked it.
Another point understood from those early days, is that one should always turn the volume down to zero before turning on / off the system, otherwise damage to the speakers could result. Again, I’ve always heeded this advice, and never chanced my luck.
I guess this probably says a lot about my personality - I’ve never been a gambler, especially when it concerns a piece of equipment that I know absolutely nothing about, and costs a fortune to boot !
I’m pretty sure that the Delta manual advises against that. Not seen any speaker “On/Off” switch either.
PS: No speaker “On/Off” switches on my other amps and their manuals say:-
“IMPORTANT! Always turn off the amplifier when changing leads (ie removing then replacing), especially speaker leads!”
I vaguely remember being advised not to turn amps on without speakers connected. However as Roadie says, some amps like mine (NAD 3130) have a speaker selection switch with up to four positions i.e. Speakers A only, Speakers B only, Speakers A & B, Speakers Off. So, maybe these amps have some sort of protection built into the output circuits. It may also depend on what “Class” the amplifier is. However if the manual advises against switching on with no speakers connected to the output, then I wouldn’t do it, especially if there is no speaker selection switch!
The normal reason for having the amp off when changing leads is to prevent shorts on the speaker wiring, and thumps and buzz happening from partly connected inputs. Common sense really, but not always in plentiful supply.
A modern transistor amplifier (ie probably 1970ish onwards) will be unconditionally stable in almost all load circumstances because the amp has enough open loop gain to achieve an ‘adequate phase margin’, something grievously lacking on early valve amps that would hoot and cry without a load and needed a Zobel network, sometimes even with a load should its inductance rise too high. I said ‘almost’ because not all amps have ‘short circuit protection’ or ‘load-line protection’ (in the standard circuit for this each power amp channel has an extra couple of small transistors and six or eight small resistors).
When building an amp, the first thing any designer will do to the finished prototype is hold their breath, while standing behind a protective shield, and switch it on without a load and powered from a bench supply with full control over current and voltage. If no bang or flying bits, then adjust up the standing current to specification, shove a signal at the input and look at the output with a scope. After all the initial tests are passed, then they are repeated with decreasing impedance loads until the maximum power load is achieved. Then they go further and see if it self-destructs or protects when the load is reduced further, eventually down to a short. Or at least that is what we used to do.
One of my designs (almost a hundred of them built by friends and colleagues in the 1970s and 80s) was very reliable, except in one memorable instance early on when a friend in a hurry used the 50V battery supply at work to power his first attempt at this amp. All was well until a machine was stopped elsewhere in the building and a very short 300V spike (as later measured) from the relays travelled along the 50V wiring and over-volted the transistors, Every single one enthusiastically lost its top and all that was left in the circuit board were their legs, and bits of transistor shell were stuck in the ceiling and Stan’s face. Fortunately he was wearing glasses. Hence the shield always thereafter.
Thanks Richard, very informative, my only concern is that the Leak amps Barrie is using were built in 1972 and were almost certainly basically “tarted-up” 1960’s technology so they may not have the safeguards you mention for later technology built into them.
I didn’t understand a word of that, Richard !
Yes, I have many happy memories of 1950s and 1960s technology! I made pocket money with it!
I was repairing and then building valve power amps in the early and mid 1960s, and transistor ones in the later 1960s.
The germanium based transistor types usually blew up after a while, mainly because the power transistors were not up to the job despite all the cunning efforts to prevent the usual failure - thermal runaway.
Bring on modern silicon at the very end of the 1960s, and some of those superb late 1960s transistors are still specified in modern discrete amplifier designs, most of which are loosely based on the 1969 design by Ian Hardcastle and Basil Lane from Texas Instruments. I changed the output stage to tougher bigger and better transistors and added a few other minor refinements for better stability and load-line protection, and ended up with a fifty watt amplifier into a 3 to 4 Ohm load. Years later I checked the design with a computer tool for circuit modelling called Spice, and the design turned out to have been just about perfect right from the start. Look inside a modern IC Power Amp and it will be much the same configuration, just with a few added tweaks for durability and worst case survival.
There is a pdf of that ground breaking early design. It has the circuit and an explanation of why they did what they did.
Hmm the link to Google didn’t work, so put “Texas Instruments Hardcastle and Lane” into Google and the first item returned is the pdf of the 1969 article.
In the words of the song;
”disappointment haunted all my dreams”
After swapping over the relevanct bits n pieces on the LEAK DELTA amp, I got chance to connect speakers and give it a test First off with some temp cable connected via chocolate block connectors to the 2 pin DIN plugs ( these came with the second “allegedly“ working amp ) Only an output to the right channel was found. I swapped them into the second set of speaker sockets, switched over on the amp but just the same. Made some decent new cables using the new DIN plugs, thinking that was the problem with the old temporary plugs but again, no difference.
I decided to plug in my phones and try the 1/4” jack socket, again just the right channel,balance control making no difference. As I was removing the headphone jack, the channel switched over to the left channel, cutting out the right channel. Tried it several times and it did the same, so it can output to both channels just not at the same time! The jack is a standard TRS stereo plug. Anyway, while faffing about with that, the receiver decided to pack up!! Tried the TT just because I could, again right channel only from speakers.
At that point i decided to do the same and pack up! I’m parking the amps up out of the way as it’s beyond my limited capabilities to effect both a diagnosis and a repair.
I’ve seen a more “modern” LEAK 3400 version, contemporary with the 3001 turntable so might have a punt at that instead. It’s always a bit of a gamble with the older stuff so I reckon I was extremely fortunate with the AIWA stacks, not been a minutes bother once serviced and tape belts renewed
Barrie
Barrie,
When you pull out a stereo jack plug the right channel contact in the jack socket will temporarily connect to the left channel contact on the jack plug and disconnect from the right channel contact as it slides out (or in). This is because the connector has contacts arranged in a “linear” fashion rather than having parallel contacts, so to speak. So it is still the right hand channel of the amplifier only that is working but connecting to the left hand earphone, not that both channels will not work at the same time.
Did you get the Leak receiver through eBay. If you did you may have some recourse through eBay as the item was described as working and it clearly is not.
This may or may not help, there’s a guy on youtube going by the name of 12voltvids who has a couple of videos showing the repair of a dead channel on a Leak Delta 75.
Thanks guys First rider off, I think I understand what you are saying regarding the single channel thing. Kuparuk, I will have a look at the YouTube video and see if I can make something of it
Barrie
Just for info, here’s the wording of the advert from eBay
“Vintage LEAK DELTA 75 receiver.
There’s a switch for a magnetic cartridge or a ceramic. e.g., low and high input for record deck cartridges.
In working order with FM MW AND LW radio all of which appears working as I can get sound from all 3.
The meters also appear working as they move when tuning.
Unable to check for quality as I don’t have an aerial.
All internal bulbs replaced and the ceramic fuses replaced due to intermittent functions.
It looks like the three centre buttons aren’t origional and the off/on knob has been repaired, but all do their job.
There are two marks on tthe cabinet as seen in the pictures.
Comes with two speaker plugs, just to get you started, and a service manual.
Selling for a friend, but unfortunately the speakers already had been taken by family.
This is a very heavy item at 12kg so collection is advised.
I have no idea what it’s worth, offers are invited but please don’t ask for it to be posted this will not happen.
Any further questions please ask.”
TBH, didn’t pay a fortune for it and the seller is a couple of hundred miles away and was collection only. (My son collected and delivered when he came up for Christmas) Not sure I want the grief of attempting to return it?
Barrie