50 Watt amplifier

[John Caswell]

Chris wrote
"Instead of holding large stock of Tx's it would be better to purchase on here and have them sent directly from the supplier"
If only it worked like that. Few, if any, manufacturers make for stock nowadays - far too expensive. Same with chassis, front panels, chrome covers etc. Manufacturers want an order, deliver it and get paid for it naturally, so someone would have to take up the slack.
For Matthew to make it viable I would guess he would have to tool up for probably 25 kits, that's a fair amount of dead money.
Even if 25 people said they would buy an amplifier here are always those that drop out thereby increasing the nett cost of each amplifier as those not purchased could be considered "dead stock".
Its really a minefield and it boils down to one thing - money.

John

[Richard]

Originally Posted by John Caswell

also not sure whether to supply kit chassis with Octal cutouts for the two small signal valves and supply reduction plates for B9A type valves. Comments useful here please.
More anon

John

Yes adaptor plates would be sensible as the chassis could then be used for a variety of classic designs

The WW photo of the 88-50 amps shows the layout similar to those chassis I posted a pic of (valves in a line down one side). They will then sit side-by-side as in the pic, as 2 identical mono blocs with toggle power switches on the front and ip/op and power sockets on the back. This is a design fundamental that needs sorting early on imho as it would be easy to end up with 2 ungainly amps which were not easy to accomodate. (ha ha no pun intended there but an ungainly amp would truly be a useless device eh? )

I will probably paint the TX top caps to match the chassis for an overall appearance similar to Quad/Leak etc. I may even do this after construction by masking the sockets, then spray etch prime and top coat which will save a huge amount of messing around with re-assembling one-offs.

Re drop through or chassis mount TXs, cover, finish, etc there are pros and cons to all. I think you'll find it more difficult and expensive trying to make a covered amp but for folk with cats and kids it could be useful.

[davebms]

hello all.. my views.. yes big holes with adapter plates
chassis mounts i like for out put
mains, im used to drop through but not to bothered
chassis size would be good if it fitted a standard size
mono blockes prefferd i like transformers in black !( but then i realy hate silver)

could it be offered as a part kit.. poss chassis and curcuit+instructions at a price to cover design work / mains transformers if special type.. then as and when collect parts and output tranys from one of the known brands
or poss use some from an existing amp.. only thinking that if it ends up only small numbers mathew will only be stuffed with a few chassis + i have some output transformers !!!

[Greg.]

Originally Posted by John Caswell

Its good being the odd one out, don't run with the herd.
As a Spanish wit once said "If they give you lined paper, write the other way!"

John

John,

Personally I'm completely with you but unfortunately, my sound system is in the living room together with the TV and my amps etc are always a bone of contention with the Missus anyway. I don't have a dedicated listening room so if I want to keep them there, they need to have some reasonable aesthetic appeal. That is why aesthetics is important to me. If I had a listening den, I wouldn't give a toss and actually, most of my stuff would happily remain in a bread boarded state. Please sympathise with me and no doubt many others here who are under domestic pressure to keep things as presentable as possible. I'm sure you know what I mean

[davebms]

. Please sympathise with me and no doubt many others here who are under domestic pressure to keep things as presentable as possible. I'm sure you know what I mean [/quote]

i do..sympathise domestic pressure nice way if putting it do they have to be there, why are they at an angle (not in line with sofa) that bit is bigger than the last one,, etc the only good thing, the front room is nearly all black (not the walls) so if i swap a black bit for a black bit

back to the poss new kit.. ive taken parts to be plated ,not an ideal approach but poss an option

[Richard]

Yes agreed on the domestic front, not that I get any stick as my gear is behind the sofa and we have an agreement that what's behind the sofa doesn't count That said I like it to look good anyway and the job's not finished until after the tidying up in my book, ok, my good might not be your good lady's good

There's a sense of beauty in an unfussy, nicely proportioned, well engineered, beast of utility such as those Quad/Leak produced. The irony of course is that they were very expensive and they expected them to be built into furniture cabinets or at least wooden sleeves and cupboards. Maybe women are just more 1950's than men.

[John Caswell]

Hi all,
Interesting comments. Need to be careful here as we may end up with a three humped camel!!
One of the big problems with drop through txs is that they us a lot of space under the chassis that could be utilised for tagboards, capacitors etc so apart from the technical and engineering points mentioned I still think that is the way to go
I think Matthew is trying to keep the basic cost down so plain covers for the Tx may be the way and if you fancy chrome plated ones well off you go. Similarly the amps would have basic components, orange drops etc so you could add boutique components yourself, ie SAXs PIOs tantalum resistors.
The two prototypes don't have anything fancy in them and one has off-the-shelf Hammond transformers, the OPTx is very, very good. Because the OPTS needs to handle 50 watts with minimum distortion it is large. I thought that the Lundahl range may be OK but they only go up to 40Watts so core saturation is likely to set in.
Power tx will probably be custom made as the Hammond has excess HT current and no 6.3V heater for the 6D22s so perhaps the custom jobbie will have a rectifier heater winding of 0-5-6.3V to accommodate both 6D22s/EY84s and 5U4/5T4/5R4GY/GZ37. No reason why you couldn't use full wave (as opposed to Graetz bridge) SS rectification either. As you can see the possibilities seem to be endless, but a basic block needs to be considered without any variations as up goes the cost.
Certainly the small signal valve can be either Octal/Loctal/B9A based so I think the amp chassis will be punched with big holes with sub plates for the small holes.

More anon

John

[Greg.]

Hi John,

I acknowledge that drop through transformers take up space within the chassis, but surely, if they are designed in, there will be sufficient space for all the fat capacitors and other upgrade components accordingly. It only becomes an issue space wise if the original chassis design did not take into account these expectations and ends up too small.

Regards,

Greg

[John Caswell]

With drop throughs more likely too large than too small especially if you allow for boutique components.
The are just a waste of space, when you see some of the amplifiers and the trouble the designers/marketing have gone through to accommodate them, I sometimes despair.

John

[Richard]

Well other than having to make a decision if you want to supply the chassis fully punched or plain re TXs I don't think it matters much.

Certainly deciding where to punch out for iec mains, ip/op and mains switch is a bigger issue.

Big caps can go on top. If we take a tape to them I think there is not much saving to be had using frame mounted TXs as they are approx cubes with the end caps on. Look at the 2 below (not the small choke).

Drop-ins are popular as they only need one end cap and the wires are safely enclosed. They don't have to be chrome or gold and a cover isn't needed for a tidy result.

This is a nice bling amp but, for me, falls into the trap of being orientated the wrong way so only one will fit on a shelf. If the connections were on the ends 2 would fit side by side,