UA175 variable mu compressor output transformer calculation

[Swedish Chef]

Anybody got a cheaper price on the 1689?
i think it's so expensive from Canford as it's a non-stock item. Don't think Lundahl will want to sell it in 1-offs...

chef

 

[jhaible]

[quote author="Swedish Chef"]Anybody got a cheaper price on the 1689?
i think it's so expensive from Canford as it's a non-stock item. Don't think Lundahl will want to sell it in 1-offs...

chef[/quote]

Well I tried to say it's about the same price from the German distributor.

JH.

 

[jhaible]

As for the original transformer, I have the following info from a barely readable document for the 176. (THat's the same circuit, but with a multi-tapped transformer for different compression ratios.) It reads:

"Modified basic 1008 [might be I008 ?] transformer.
Less tertiary winding and plus taps
(Reference UTC No. PA 5946 [ might be PA S946 ?]
Reference U?? [unreadable] No. C-10477
for circuit.)"

Now, can anybody make anything out of this?

JH.

 

[Swedish Chef]

Well I tried to say it's about the same price from the German distributor.

Sorry, just being a stupid Englishman! :green:
I thought you were just Eurofying my price!

Now, can anybody make anything out of this?

shall we hold our breath...? :shock: :grin:

chef

 

[zebra50]

[quote author="Swedish Chef"]Anybody got a cheaper price on the 1689?
i think it's so expensive from Canford as it's a non-stock item. Don't think Lundahl will want to sell it in 1-offs...

chef[/quote]


Cheffy!
Lundahl do sell one-offs, but usually only if you can't get it locally. I recall looking into the Lundahl option trafo for the Altec comp last year, and I think they quoted me about 100 euros + VAT and postage, so little difference in price.
Stewart

 

[Swedish Chef]

Too right Zebby!
Here's the email I just received from Per:

LL1689 base price (EXW Sweden) Euro 80.00

Shipping costs and (if you are not VAT registered) Swedish VAT will be
added.
The LL1689 has the following discount breaks:
10+ 10% discount
25+ 20% discount
50+ 30% discount

Canford is not our distributor for our tube amp transformers, so their
discount is not favourable.
This can be the reason their price is rather high.

- Per Lundahl

Interesting... :green:

chef

 

[edanderson]

the PA5946 was the transformer that UTC used for their 1008 amp, the 610, and probably other pieces. the 610 schem i have indicates that the PA5946 was a 30k to 600ohm transformer with a minimum of 55Hy of inductance on the primary. it also had a tertiary winding, which was not used in the 610.

maybe you could get the output transformer that UA is using in their 610 reissue? groupdiy member scenaria may know something about that.

ed

 

[jhaible]

[quote author="edanderson"]the PA5946 was the transformer that UTC used for their 1008 amp, the 610, and probably other pieces. the 610 schem i have indicates that the PA5946 was a 30k to 600ohm transformer with a minimum of 55Hy of inductance on the primary. it also had a tertiary winding, which was not used in the 610.

maybe you could get the output transformer that UA is using in their 610 reissue? groupdiy member scenaria may know something about that.

ed[/quote]

Very interesting!

Is this 30k c.t. on the primary, or 30k + 30k ?

(In the first case, my calculations from the beginning of this thread would be far off.)

JH.

 

[edanderson]

the 610 schem i have says 30kct for the PA5946. it was redrawn by the lab forum member winston o'boogie aka john hinson, formerly of UA. you could try to contact him, but he is a pretty busy guy. also scenaria may have some info on the output transformer used in the 610 reissue.

hope this info is helpful somehow.

ed

 

[jhaible]

[quote author="edanderson"]
hope this info is helpful somehow.

ed[/quote]

Yes it is - it may stop me from buying a very special and expensive transformer, where a more standard confguration would work. Thank you!

I still wonder where the error in my maths is, though.

I made my calculations based on the asumption that the output attenuator in the 175 has no insertion loss when it is on cw end position. If, for insatnce, it has 6dB loss, then the transformer would calculate to something closer to 30k : 600 than my 200k : 600. But that's unlikely, for such an attenuator, isn't it? (It looks like a bridged T config, not a ladder config where insertion loss is to be expected.)

Still puzzled.

JH.

 

[[silent:arts]]

I made my calculations based on the asumption that the output attenuator in the 175 has no insertion loss when it is on cw end position. If, for insatnce, it has 6dB loss, then the transformer would calculate to something closer to 30k : 600 than my 200k : 600. But that's unlikely, for such an attenuator, isn't it? (It looks like a bridged T config, not a ladder config where insertion loss is to be expected.)

from the Universal Audio 176 Adv (downloaded from UA)

The attenuators normaly supplied are of the unbalanced ladder type, with 20 detended 2-db steps. A 6-db greater output can be obtained with a bridged-T output attenuator ...

ps: why have I had SQL-errors with this post yesterday ?
I tried a few times to post, but always had SQL Errors.
I tried it again this morning, and after that all posts I tried yesterday are in the tread ??? :?: :?: :?:

 

[jhaible]

Well I don't know about your SQL errors, but your post finally explains everything about this transformer!

With the extra 6dB, my calculations would give 50k c.t. (based on the 45V threshold, see above), which is reasonably close to the 30k c. t. .

Thanks to all who helped!

JH.

 

[Swedish Chef]

thank the Lord for 2 week lead times!!!!!!!! :grin:

chef

 

[SSLtech]

£74? ... ...

That's $140!!!!!!!!

:shock:

Keef!

 

[Swedish Chef]

Oh yes! :shock:

 

[jhaible]

[quote author="SSLtech"]£74? ... ...

That's $140!!!!!!!!

:shock:

Keef![/quote]


Just to avoid confusion:
After silent:arts' revelation I'm now looking for an affordable 30kct : 600 transformer (3.5 + 3.5 : 1) - not that 9+9 stuff anymore.

But now I need an even higher power rating! When 6dB is lost in the output attenuator, then the trafo must deliver 24dBm + 6dBm = 30dBm !

A Lundahl LL1630PP would fit (with the two secondaries in series), but that's also 99 Euros !!

Any more affordable alternatives for that ?

JH.

 

[jhaible]

Ok, I had to buy a transformer now. Want to finish this before I pack everything up for moving houses.

I thought I'd go for a LL1630, but unfortunately the German distributor is on vaccances, and buying directly from Lundahl would have cost me 140.00 EUR. 8-(

Now I ordered a Sowter 8344 (what they sell as a Fairchild 760 signal output). The specs seem to be fine (60k : 600 and 30dBu output).
I hope I did the right thing. I wanted to tra a Sowter transformer anyway, sooner or later. (That's my 1st buy from them). Looking forward to try it, to hear how it sounds.

Any teasers what to expect?

JH.

 

[CJ]

Should sound fine, a big chunk of M6 for low distortion on the bass notes.

 

[SUPERMAGOO]

build them!!!
http://groupdiy.twin-x.com/displayimage.php?album=40&pos=44

 

[rafafredd]

WOW! Would you open another thread for this marvelous machine?