The VAC is back!

[bronal]

Well I finally got my beloved VAC 70/70 back last night from Patrick Turner, after an 8 month wait.

Patrick has virtually rebuilt the amp, so I guess I've now got a 'Turvac' or possibly a 'Vacurner' (ugh!).

What he did was (a) add relays to the front on/off switches (b) detune the amp so it now produces 50wpc instead of 70wpc (c) extensively revise and tidy up the circuit (d) improve cooling of the transformers and (e) install a protection circuit (yes I know it's supposed to veil the sound but with 8 300Bs in tow...).

How does it sound? Well, I like to run this amp with zero NFB and had forgotten how much gain this produces, so Rothwell 10dB attenuators are now on the inputs. The 300Bs are still running in so I'll defer judgment for a little while.

I'd like to hear from anyone else who has, has had or who has heard a VAC. AFAIK I am the only 70/70 owner in Australia.

In sonus fraternitate

Alan

PS: I tried to post pix, without success. I'll send them to Chickenism for resizing.

[warnsey1]

Fantastic mate. I look forward to coming around for a listen.

[Jake]

Wow Alan, 8 months without your amp. I went a month and it drove me crazy.
Looking forward to your thoughts when you think its run in. Im not familiar with the VAC though, do you have any pics?
And why the need to detune it to 50wpc?

Cheers,
Jake

[bronal]

Wow Alan, 8 months without your amp. I went a month and it drove me crazy.
Looking forward to your thoughts when you think its run in. Im not familiar with the VAC though, do you have any pics?
And why the need to detune it to 50wpc?

Cheers,
Jake

I'm sending pix to Chickenism shortly.

Yes, Patrick detuned it to prolong the life of the valves. He believes that VAC, like most manufacturers, drive valves too hard to get outputs to compete with SS designs. My speakers are 96dB sensitive, so losing a little power is not an issue for me. Jeez, even the Melody M2A3 monoblocks produce wall vibrating bass in my room with 18wpc, as Chickenism will hopefully testify!

[warnsey1]

Here's to hoping I don't have the same kind of waiting time.

What section of the drivers will use for the VAC?

[Chickenism]

Evening all,

Whilst visiting Alan last week in Canberra I got to meet Patrick and saw this awesome amplifier and some of the work being done to it. Bronal, I'm glad it's finally back home; if only it was done a week earlier I would have been able to hear it as well.

Oh well, there's always next time...

I must say that the Melody's at 18w/ch drove bronal's Ambience ribbons to insane levels with nary a hint of strain; 50 watts a side is more than enough.

Anyway, without further ado, VAC pics:







Look forward to hearing more about how this amp turns out. :)

Cheers! Dave

[Jake]

Thanks Dave (Alan's secretary? :p)
That is one seriously good looking bloody amp.

Cheers,
Jake

[bronal]

Thanks for posting these, Dave.

The two outside 6SN7s are Sylvania VT-231s and the two inner ones are Russian milspecs. The 300Bs are Sophia Carbon Plates (note to 56oval - this is why I don't buy KRs or Emission Labs. Can you imagine the replacement cost?)

At first I wondered why the 300Bs didn't glow as much as the previous EHs I was using. Then it dawned on me - carbon plate doesn't glow!

In sonus fraternitate

Alan

[Chickenism]

No probs at all Alan.

One question, any particular reason for the Carbon Plate 300B's over the Mesh Plate versions from Sophia?

I only ask because I've heard very good things about the Mesh Plates.

Cheers, Dave.

[Jake]

"Have the new paperclips arrived yet Chickenism?"

"Yes, Bronal, they're over there...."


:D


(dont mind me, Ive got a flu, and apologies to Monty :p)

[Chickenism]

Cold 'n' Flu tablets obviously working a treat there, Jake...:D

[56oval]

Hello bronal .
4 sets of KR's can be dear ,I bought the KR's cheaper per pair than Sofia's $330 a pair .
I wouldn't say PT detuned your amp more like has it set to be more musical and
Chickenism the Mesh plate's can cloud low level info in the mids and round of snare drums and kick drums .
Its a very nice looking amp bronal well worth the resto .

Cheers

[Jake]

Cold 'n' Flu tablets obviously working a treat there, Jake...:D

Just kicking in now..........:D






WWWWwwwoooooooooooooooooooooooooooHHHHhooooooooooo ooooo! :cool:

[bronal]

No probs at all Alan.

One question, any particular reason for the Carbon Plate 300B's over the Mesh Plate versions from Sophia?

I only ask because I've heard very good things about the Mesh Plates.

Cheers, Dave.

Dave: I bought them because they got a very good review in Hi Fi+ some time ago. Also, they are very ruggedly built, so can take a lot of punishment. But I'm sure the mesh plates would have been good also. Let's face it, when considering Sophia/TJ/EML/KR you are looking at very high quality 300Bs, so there are not going to be night and day differences between them.

Cheers

Alan

[56oval]

when considering Sophia/TJ/EML/KR you are looking at very high quality 300Bs, so there are not going to be night and day differences between them.

Cheers

Alan
I wouldn't say that after living with TJ's/Sofia's for 3 years and now using KR's & EAT's the EAT's are very over priced to be honest and EML has to live with the stigma of being unreliable .

Cheers

[Chickenism]

I wouldn't say that after living with TJ's/Sofia's for 3 years and now using KR's & EAT's the EAT's are very over priced to be honest and EML has to live with the stigma of being unreliable .

Cheers

56,

Interested in your thoughts on the differences (if any) between TJ and Sophia 300B's.

Sorry Alan, bit of a thread hijack but it's kinda related. Interested in your opinion in this one too.

Cheers Dave

[bronal]

I wouldn't say that after living with TJ's/Sofia's for 3 years and now using KR's & EAT's the EAT's are very over priced to be honest and EML has to live with the stigma of being unreliable .

Cheers

56: you must spend a fortune on valves!

Dave: I'm not really in a position to comment on differences between 300Bs. The only ones I've heard are Electro-Harmonix (OK but nothing out of the box), TJ Full Music (very nice and sweet but maybe too 'glamorous' for some people) and the Sophias (up to now sounding overall quite neutral).

A.

[56oval]

56: you must spend a fortune on valves!


Hello Alan .
The tubes worked out cheaper than other parts for my new amps .
Dave TJ's & Sofia tubes are made by the same company .Its easier to be able to sit down and listen than explain some times .
Its a pity I only have 3 pairs of KR's here not 4 for you to try .
I found the solid plates to be better balanced tube over mesh ,but you can always tweak the circuit on both tubes .
I love all those tubes in that rack of yours .
Cheers

[Fast996]

I own both a Vac70/70 and a pair of 140 monoblocks...These are the best valve amps I have ever heard.Let me say have you contacted Kevin Hayes @ Vac in regards to your valves running hard?The sentry circuit is an auto biasing circuit which should alleviate any startup problems and prolong tube life.
I have talked to Kevin at VAC , also Richard at Sophia Electric the importer of the 300B carbon Plates and you should have no problem with them.
I am interested in your review of your modified 70/70 as you look to have the sentry circuit installed.The carbon plates in my 70/70 are very liquid and are life like my speakers are 96db efficiant large sattlelites with dynaudio drivers.The sound is as if transported into the venue be it live performance or recording studio.The speakers become airpumps disapearing completely.
As for drive tubes look at the Brimar cv1988 6sn7gty they are very good they can be had for $200 US. They are well worth the cost per pair.
This amp retailed in 1994 for $8000-$11,000 US .It is dual mono in every way right down to the dual power plugs on the back.

By the way the biggest improvement for the smallest dollar spent is a set of very good Power cords I use Walter Field's Nbs cables very expensive $550 for a 2 meter length but unbelievably quiet with the 70/70 .You are at -125db down, the sound stage has "pop" to it listen to Standards Live
by Keith Jarret or Kinda Blue for a jawdropping experience.

Like i said i look forward to your report.

Gary
Reno Nevada
USA

[ehtcom]

Hi Alan.
What brand driver tubes are you running in your VAC?
Cheers, Earle.

[bronal]

Hello Gary and welcome to SNA! How did you find us? Was it through googling for 'VAC'? Anyway, I hope you will enjoy visiting and contributing. Any chance of pix of your complete system?

I must confess I can only speculate what a 140/140 sounds like. I assume it's two 70/70 in mono mode? VAC, like many other overseas brands, has no real representation in Australia. I bought my 70/70 locally off eBay in late 2006. It came with EH 300Bs and Golden Dragon 6SN7s. I changed the 6SN7s to Sylvania VT-231s for the input and Russian milspecs (the real ones) for the drivers. That's the way it was until a 300B blew just before last Christmas.

Forunately, here in Canberra we have Patrick Turner of Turner Audio (www.turneraudio.com.au) (http://www.turneraudio.com.au), who is one of Australia's leading valve gurus. Patrick has gone through the VAC and made quite a few changes, as detailed in my earlier post on this thread. He wasn't too complimentary about some of the circuitry or the quality of the parts used! VAC were of no help at all, despite several emails, so Patrick had to trace the circuit out himself.

Fortunately, just before the valve blew, I'd invested in 8 Sophia Carbon Plates. I chose them not only because of reviews but also because they are very ruggedly made and I knew the VAC drove the output valves quite hard. In fact, Patrick has detuned the amp to about 50 wpc because, in his opinion, it was driving the 300Bs to the limit. This doesn't really matter too much in my system, as my speakers are about 96 dB sensitive.

I've had the VAC back for about 4 weeks now and the valves have done about 40 to 50 hours max, so they're nowhere near run in. At first they were rather lifeless with rather poor bass IMO, but are opening up nicely.

The main problem I have with the amp is its sensitivity - it develops full output at about 0.2v according to Patrick. This, of course, makes fine tuning the volume via my Melody preamp quite difficult, especially as the VAC has to be the most explosive amp I've ever heard on musical peaks. I remember when I first got it my jaw dropped at its PRAT - anyone who thinks valve amps are comfortable and leisurely should listen to the VAC.

I've tried Rothwell 10dB attenuators on the inputs, but they introduce a noticeable veiling of the sound. I don't like using the VAC with NFB either, as it is just so open with no NFB and even a little NFB (6 dB) seems to close the soundstage up. So I've started using the 2 ohm speaker connection, even though the load being presented to the amp through the Zero Autoformers I use is about 8 ohms. This has the effect of decreasing the sensitivity somewhat, although power is decreased as well.

The overall sound of the VAC at present is highly neutral and analytical with a lean controlled bass and clear top end. No 300B glamour I'm afraid! I'm hoping the bass will fill out a lttle bit with time - but not too much as I don't like overblown bass either. BTW I use a Pure Silver Connection 0.5 metre power cord.

I was interested in your recommendation for the Brimar CV1988s. Do you know where I can get four? Brent Jessee has one at the moment for US$70, but one is no good to me.

Cheers

Alan

[ehtcom]

Hi Alan.
Connecting to the 2 ohm output will drastically effect the response of your amplifier. Instead of your 300B's seeing a load of ~3500 ohms, the reflected load is going to be ~14000 ohms. I would persevere with the 8 ohm output and recommend using a good "splitter/attenuator ;) " in-between your melody and vac.

Cheers, Earle.

[bronal]

Earle: many thanks, but could you please explain for us non-technical types?

Cheers

Alan


Hi Alan.
Connecting to the 2 ohm output will drastically effect the response of your amplifier. Instead of your 300B's seeing a load of ~3500 ohms, the reflected load is going to be ~14000 ohms. I would persevere with the 8 ohm output and recommend using a good "splitter/attenuator ;) " in-between your melody and vac.

Cheers, Earle.

[Fast996]

"Hello Gary and welcome to SNA! How did you find us? Was it through googling for 'VAC'? Anyway, I hope you will enjoy visiting and contributing."

Hi Alan,
It is great to be among valve enthusiasts.I happened to come by this site by way of google.What started the search was your post on Audiogon re: the Carbon plates.
My system is in limbo as I recently purchased a pair of VAC 140's as shown in my post above.As soon as i can move things around I will post pics.
I have had many amps starting with a Fisher 500C when i was young .Solid state I tried for a while but then was really turned towards valves after listening to some Fulton J monitors and Futtermann Amps a truly spectacular experience these were
the most expensive tube amps in there day $12,000ea in 1984 with 90w per channel @ 8 ohms.I was ruined never before had I heard such sound reproduced like that.

Until I read about a startup amp mfg called VAC which in 1994 was sold by only 2 or 3 distributors here in the US.I friend of mine said these amps are simply astonishing so i saved up and bought the 70/70 sight unseen for $8000 and for me then that was some large coin.The amp did not dissapoint but first i tweeked my listening room and system...using a Accuphase C200 Preamp ,Linn LP12,Sony ES707 CD player,and my custom made sattlelites 96db 6 ft speakers. I was ready for great sound ,but no, until I contacted Walter @ NBS Cable and spend alot of money did i truly have a live system.
You see i didn't realize how the power coming in was so dirty that it really muddied the sound.That's why when you listen late at night 11:30-2:00am your system transforms itself.The "Grid " quiets down.

Anyway you find the Brimars by googling "cv1988" most pairs are $200US.
they are REALLY QUIET...which lowers your noise floor which is the secret . It is why I spent real money on cables.

I'm going to check out Turner's page looks like a lot of info.

Curious does your Vac sound better with the mod's .The dynamics you talk about is a result of the transformers .Did you notice a quieter noise floor and more defined sounstage?

Look forward to posting much more and thanks for the kind welcome.

Gary
Reno Nevada
USA

[datafone]

Nice bit of work done on it going by your post.

Also I like "TurVac" :D

[56oval]

Hi Alan.
Connecting to the 2 ohm output will drastically effect the response of your amplifier. Instead of your 300B's seeing a load of ~3500 ohms, the reflected load is going to be ~14000 ohms. I would persevere with the 8 ohm output and recommend using a good "splitter/attenuator ;) " in-between your melody and vac.

Cheers, Earle.
Hello Earle

Wouldn't it be easier to mod the input stage and whind output tranny's to match speaker load .

Cheers

[ehtcom]

Hi 56.
I have had a look at the circuit and the VAC uses a resistor on the input grid of the first stage, so its just a matter of changing this for a higher value and changing the ground reference resistor to maintain 100k input impedence.

Very simple, and if Alan was around the corner I would happily drop by and do the mod.
Canberra is about 9 hours away though :/

Cheers, Earle.

[ehtcom]

Earle: many thanks, but could you please explain for us non-technical types?

Cheers

Alan
Hi Alan.
To put it very simple, the output transformer reflects the speaker impedence to the output valves.

Your output transformers have a 3460 ohm primary impedence when the secondary is connected to the matching load.
8 to 8, 4 to 4 etc.
If you connect 4 to 8, you will halve the reflected impedence and the primary will then become 1730 ohm. If you double the speaker load to 16 and connect it to the 8 ohm tap you will double the primary impedence, i.e. 6920 ohms. In your case you have connected 8 ohms to the 2 ohm tap, quadrupling the impedence to 13840 ohms. This figure is quite a bit above the maximum recommended load for a quad of 300b's running in push-pull and whilst it "**shouldn't" damage the amplifier it will degrade the performance.
** With such a light load there is a slim possibility of HF circuit oscillation (if feedback is used) and possible plate arching on the 300B's.

Cheers, Earle.

[bronal]

Thanks, Earle.

[bronal]

Gary:

some VAC-related questions for you, if you don't mind!

(I've just whiled away a couple of hours following up links to VAC. It seems there is a lot of general, but not much specific, information about VAC products, and the 70/70 in particular.)

1 when was the 70/70 produced? My nest guess is from 1993/94 to 1999/2000 (Mk III). Mine's a MK II so would I be correct in estimating it was made around 1998?

2 why did VAC change over from triodes to KT88s?

3 would it be worth my while chasing a VAC preamp down? I notice their gain is less most, so I wonder if one would match up better with the 70/70 than the Melody P1688R.

Upscale Audio have Brimar CV1988s at US$100 each but I'm having trouble getting past their ordering system (needs a US style zip code even for overseas orders).

Cheers

Alan

[56oval]

Upscale Audio have Brimar CV1988s at US$100 each but I'm having trouble getting past their ordering system (needs a US style zip code even for overseas orders).

Cheers

Alan
Hello Alan
You need to send them an email ,they don't take oversea's credit cards only direct payment into their account .
Have the tried this mob I haven't http://www.tubemonger.com/.
Cheers

[Fast996]

Alan ,
1. Mine is a MKII also purchased in 94 but mine did not have the sentry protection circuit.THE MK II'S mfg from 6/95 on had the sentry.The MK3'S were much later 98 and after .The Renn series were discontinued i believe in 2000 because of cost issues relating to Mfg.I can't be sure but the escalation of the 300B tube must have played a part.
2. KT 88'S much easier to get and $20ea vs alot also the sound is within 90% of the triode so they say.
3. I would not .I have had many preamps SS & TUBE .When I first bought my Vac i had Mike from Quicksilver audio up to my house and a mutual friend they brought 2 or 3 preamps ARC CJ & one of Mikes they were all very good in a lot of different ways
some had highs some had bass but none stole the show these were all $2000 3000+
pre's .My Accuphase C200 bested them, $499 for it new although Solid state it has a synergy with this amp that's great....moral of the story preamps and amps are a listening thing in house over time.Find a dealer that will let you audition at home.
Usually preamps with 6922 (6dj8's) are very good.Ilove my Monarchy Dac it has a line stage also but my C200 is still my choice replaced all the caps with Muse .

4. TUBES CV1988 will email you.


Gary