ImPasse Preamplifier

[Albrerta]

Well, the amp I have is AMS1000-2600. In the manual,for balanced inputs, the input impedance varies between 1,37 and 14,5 Kohms. Meanwhile, I'm reading Jensen's doc (as060), for unbalanced input / balanced output, it says "output loads should match and be >20Kohms...", believe the same with cinemag

 

[jackinnj]

Some new (and old) Maida regulator PCB's with heater take-off. These also allow for using two electrolytic in series when the HV is higher than what SY had originally specified:

 

[mrdave45]

Hi, I want to build an impasse for my F4.

Looking through things it looks like the power transformer is a bit of a headache.

Im in the UK

Ive found this

Hammond 373AZ, main transformer, universal primary, trasformatore, 1pc. | eBay

Datasheet here

http://www.hammondmfg.com/pdf/373AZ.pdf

Does this look appropriate?

Anyone found better alternative in the UK which dont involve £150 or so on a custom wound effort?

Thanks

Dave

 

[SY]

It's totally noncritical- anything that will get you the required B+ will work fine. And you can use a separate transformer for the heaters. That transformer you linked seems quite unnecessarily expensive- the postage alone was more than I paid for my transformer!

 

[mrdave45]

Hi, yes, I thought the same. All these transformers seem to be quite cheap in the us but are very expensive once imported. I'm struggling to find anything like this made over here. There seems to be quite a good choice of main power transformers 200ma or so but then they're a comparable price anyway. Does anyone know of a decent uk supplier for such things.
I was hoping Danbury would have something but there were no stock transformers listed on their website.

 

[qwertyl]

I had the same issue, eventually I bought 373AZ from Mouser for about 60GBP.

 

[mrdave45]

Thanks quertyl!!!!,
Its looking more likely that Ill just get one of those as well as it seems to be the closest to the one in the article for UK use.
Its totally overpriced but Im struggling to see an alternative. Its seems this sort of thing is much more niche over here.
Dave

 

[bvtrinh]

Hello, I would also like to add a tube power regulated supply and was wondering if this one here would work
Tube Power regulator DIY PCB w/parts, ref Jadis/LS-57

Here are the specs:Tube Base Power Regulator PCB w/parts
using EL84 Tubes
Circuit design based on Jadis preamp
Model No: LS-57, Assembled and tested

(LS-57, tube based power regulator)

-Circuit design reference Jadis preamp
-High voltage section using 6X4, EL84, 12AU7
-Voltage can be adj. from 150V to 400V
-Two heater regulator 6.3V~ 12.6VDC adjustable
-using LM317 for heater regulation
-2.4mm thick gold plated fiber glass
-PCB with 2oz copper

Optional Items:
-Matched 100VA R CoreTransformer
-matched new tubes: 6X4 x 1(EH), EL84x1 (EH), 12AU7x 1 (EH) USD53 + USD12 shipping
-LS-9 preamplifier board

 

[SY]

I would trust nothing from that dealer.

 

[bvtrinh]

I would trust nothing from that dealer.

Thank you for your response. Other than the dealer, would something like that be suitable?

 

[mrdave45]

Woo hoo! Ordered my boards/kits from tech-diy. So hopefully won't be too long before I can start building mine!

 

[SY]

Thank you for your response. Other than the dealer, would something like that be suitable?

No way to tell, unless the schematic is there but I'm missing the link.

Jadis would be the last circuit I'd ever copy, if indeed this is actually a copy. But when someone is in the theft business, they are likely to steal whatever they can get more money for.

 

[bvtrinh]

No way to tell, unless the schematic is there but I'm missing the link.

Jadis would be the last circuit I'd ever copy, if indeed this is actually a copy. But when someone is in the theft business, they are likely to steal whatever they can get more money for.

Well, I certainly do not want to support that. I was wondering if you knew of any diy tube psu that would work with the Impasse? Thank you very much!

 

[6L6]

bvtrinh - What on earth is wrong with the one designed for the job?

 

[bvtrinh]

Absolutely nothing at all. I will probably go that route once Jack returns. I just had a silly idea of having a preamplifier with several tubes for aesthetic purposes.

 

[SY]

I'd look at Jan Didden's high voltage reg, or for a more vintage approach, copy one of the regs used by Tektronix in their tube oscilloscopes.

 

[6L6]

for a more vintage approach, copy one of the regs used by Tektronix in their tube oscilloscopes.

Oooh... That's a fantastic idea.

What would be a suitable model number to start looking? (I know nothing about old scopes...)

 

[SY]

Perhaps one of the 500 series? The 502A (one I used to own) used a 12B4 pass tube with a 6AN8 configured as a diff amp and achieved better than 1mV ripple.

 

[Zen Mod]

me always vote for shunt

 

[KatieandDad]

I've really got to get mine back out of its box. I haven't had any time to play with it since I moved house last year.