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Bottlehead vs. Dynaco Pas 3

B

bluepoint123

Member
I've had a Dynaco Pas 3 for 15 years now. Everything on the front panel has been bypassed with the exception of the Bass and Treble controls. The volume pot was upgraded as well. I'm looking to upgrade a bit. I rebuilt my Stereo 70 last year with the VTA kit. Very happy with that. I only listen to vinyl on this system. I feel like the phono stage could improve over the Pas circuit. Here's my question...
Am I better off building a phono pre kit like the Bottlehead Seduction and using that with the Pas 3 or just rebuilding the Pas 3 with a kit from Tubes 4 Hi Fi?
I do like having the bass and treble controls functional though I've never owned a preamp without them. My turntable is a VPI Scout with a Dynavector 10x5. Any thoughts are appreciated.
Thanks!
 
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I did the PAS kit from Tubes4HiFi and am really pleased. Sounds very nice with my ST-70 VTA. I've never tried the Seduction so no help there.

The PAS kit is a huge improvement and I guess I was determined to get that old PAS right. I'd like to try some other preamps and hear good things about the Seduction. The Aikido is another that interests me.

Here's a pic of my PAS kit - still rolling tubes so haven't quite finished with putting the case and knobs back on.
 
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Do you miss the bass and treble controls on the Pas? Having never owned a preamp without them I'm trying to get a grasp on what the sound is like.
 
Great looking PAS there. I see a Mark III on the bottom shelf hiding in your picture. Also, are you running EH88s in the Stereo 70? Inquiring minds want to know.
 
I had a PAS3 I loved. I put new original boards in, put a power supply board in, replaced the selector switch and the volume with an Alps. I toyed with the tone controls in and out (a very simple mod) and I must say I preferred the sound with the lone controls in the circuit. I kept them at 12:00. To me with the tone controls out of the circuit, the sound was too neutral, less warmth.
 
Rebuilding your Pas is a good option, and one poster has shown an option.
I had 2 very good condition Dynaco Pas preamps, and I rebuilt both of them with the Audio by Van Alstein Super Pas III kit. It replaces everything except the box and transformer. Replacement transformers are available if needed from various sources.

The kit uses the exact same tube compliment as the stock pas, but the circuit is anything but similar. Sound is very much improved and this unit stayed on stereophiles list of recommended components for years. They work reliably as hell, always work and sound very, very nice. The improved circuitry will drive lower input impedance amps, i.e. solid state without rolling off the frequency response. Plus, an extremely nice phono section is thrown in with the deal.

I can strongly recommend this unit and its phono stage, I've used them dailey since the mid 90's.

It also allows you to continue to use a component you may just be used to and would like to see stay in your system, albeit the insides will be different.

As to the Bottle head stuff, very well thought of and would no doubt out perform a stock Pas. To be very successful, and by successful I mean have it look decent as well as work, you need to be a bit of a craftsman. There are lots of examples of the units done by people who are. Personally, I dont like the look of a bunch of loosely cobbled together stuff that looks like a science fair project with a birds nest inside. Dont get me wrong, I've seen some very nice bottlehead jobs, and the sound is the big bang for the buck.
The looks depends on you.

As to missing the tone controls, whats to miss? As implemented, they are some of the worst I've seen, and a large improvement would be had by removing them in ANY case, along with the filters and loudness controls.

I dont know how plain the instructions are with these other kits out there, but the Van Alstein instructions are like the Dynaco instructions of old. Very clear concise, and if you can solder and ID components, its impossible to mess up. They will tell you how long to cut a wire, where it goes, etc down to the last detail. When done, it doesnt play radio stations, click or buzz while you are fiddling with it, it powers up extremely easy as well as down, due to the same tube rectifier the original Pass used. While I dont recommend doing this, it is one of the few preamps that if accidentally switched off in use doent make a big pop, nor does turning it back on with the power amp powered up, again I wouldnt recommend doing this either,
you will see your woofers slowly suck in a little, then slowly go back out. Dont ask how I know this.

Either path you take will allow you to learn a lot, that's for sure!:yes:
 
bhamham said:
I did the PAS kit from Tubes4HiFi and am really pleased. Sounds very nice with my ST-70 VTA. I've never tried the Seduction so no help there.

The PAS kit is a huge improvement and I guess I was determined to get that old PAS right. I'd like to try some other preamps and hear good things about the Seduction. The Aikido is another that interests me.

Here's a pic of my PAS kit - still rolling tubes so haven't quite finished with putting the case and knobs back on.
Click to expand...

Nice, I've looked at these kits before. I see you have an older Pas 2 with brass faceplate. Just like my first one. I put a Van Alstein kit in it, my first tube project and I couldnt make it stop humming. I sent it to Frank Van Alstein who pointed out it must have been one of the first few, as it didnt have the little ears on the case by the outputs for the power amp, and those little ears are what grounded it to the case. No wonder it hummed! Small piece of wire or two and the ground problem was solved.

agree the Aikido looks interesting.:yes:

Russellc
 
bhamham said:
I did the PAS kit from Tubes4HiFi and am really pleased. Sounds very nice with my ST-70 VTA. I've never tried the Seduction so no help there.

The PAS kit is a huge improvement and I guess I was determined to get that old PAS right. I'd like to try some other preamps and hear good things about the Seduction. The Aikido is another that interests me.

Here's a pic of my PAS kit - still rolling tubes so haven't quite finished with putting the case and knobs back on.
Click to expand...

Another thing VanAlstein does that you could do to your pre, is to mount the transformer on the back of the case. This removes the heat it produces as well as any "electro-magnetic" trash inside the case. Heres a pic: As you can see from the last picture, the bottom nut that holds on the transformer interferes with the bottom of the case. A cheap nibbler from RS will allow you to nibble out a small notch for it to clear, very easy to do.
 

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DanO55 said:
Great looking PAS there. I see a Mark III on the bottom shelf hiding in your picture. Also, are you running EH88s in the Stereo 70? Inquiring minds want to know.
Click to expand...

Hi DanO55, thanks for the nice words on my PAS. Actually, that's another ST-70 that I'm planning on doing a 'Dynamutt' board. Not EH88s but GEC KT66s that I'm trying in the ST-70 VTA.

About tone controls, I have to admit there have been a few times when I would have liked to 'enhance' the sound a tad in either direction. 95% of the time it just sounds right and I wouldn't adjust a thing.

I looked at the Van Alstein Super PAS and was tempted but the Tubes4HiFi kit seemed a better value for me. Plus, Roy Mottram designed the VTA board and I thought his design for the PAS would compliment each other.
 
This thread shows something many of us have experienced with Dynaco products. That is enthusiasm. Lots of people started this never ending process of great sounds with Dynaco.
 
I guess my biggest fear with no tone controls is that it will sound like the stock Pas 3 with the controls set flat. That sound isn't too happening. I usually turn both bass and treble up to about 3:00.
I run KT 66s in my Stereo 70 (VTA modded) too. They really give the midrange a good presence.
Looks like I'll do a little obsessing between the VTA Pas and the Van Alstein circuit.
 
I had a Dynaco PA3, the final tube version. I personally am not a fan of any of the 12A type tubes. You might try cascading your PAS with another tube pre that uses different tubes. This is good ear training, I think. Maybe something with a 12b4 with its cathode bypassed with a 50mf cap. Leave the cap out if you like a warm sound. It'll definitely liven up your PAS playing vinyl with the tone controls bypassed. It's kinda easier I think to cascade a pre then modding the PAS (making room, soldering, etc.) and it exposes you to different sounds. If you screw up your cascade pre, you still have your unmodded PAS as backup.
 
Hello,
I have two PAS-3's, One has the stock circuit with tone controls removed/RIAA mod done and new volume control. My other unit has the PAS3-Z boards from tubes 4 hifi...I think the PAS-3Z sounds great with my Dynaco stereo 70's (Dynamutt and VTA) ,neutral, clear and accurate, but for my Heathkit W-5M mono blocks I prefer the one with the original circuit..It seems to have more punch.. also I really have to turn up the Volume control with the PAS3-Z, that is not really a problem because its quiet, maybe it's just psychological because I've never had a preamp I could turn ALL THE WAY UP!...I think your choice may be driven by your power amp.
Cheers
 
kirkleclaire said:
.. also I really have to turn up the Volume control with the PAS3-Z, that is not really a problem because its quiet, maybe it's just psychological because I've never had a preamp I could turn ALL THE WAY UP!...I think your choice may be driven by your power amp.
Cheers
Click to expand...

Hey Kirk, what speakers are you driving with you PAS3-Z & ST-70 VTA? Just curious as I don't need much volume adj on with my Klipsch.
 
Most pre's have way more line gain (and stages) than is needed with typical CD players and tuners, one modest line stage of gain like the PAS3-Z sufficient to accomedate the phono stage's gain with a typical cartridge would be adequate. A single line gain stage also normally inverts acoustic polarity and should be corrected by reversing speaker line polarity. Fewer stages and less 'stuff' = greater transparency and neutrality, I have no interest in owning gear that pfutzes with the sound by acting as a filter to compensate for problems elsewhere. I am revising my own 30-year project PAS and am considering putting the VTA boards in it eventually.
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bhamham said:
Hey Kirk, what speakers are you driving with you PAS3-Z & ST-70 VTA? Just curious as I don't need much volume adj on with my Klipsch.
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I have a pair of Klipsch Cornwall and a pair of Heresys....I use the Cornwalls for most listening...I generally keep the volume control on the VTA at about 12:00-1:00 and with the Dynamutt..a bit more....with the Heathkits 3:00 or more..of course it depends on the record, an old Blue Note Deep groove doesn't need as much as say a Ziggy Stardust on thin Dynaflex...I guess you noticed I only listen to records...most of the time!

...I'm curious though about the hook up for the Volume Control on the PAS3-Z...I wired mine like the old PAS-3 and I noted you and Roy wired it a bit differently...hmmmm.. there were no instructions so maybe I did it wrong??
Cheers
 
Yea, I just followed Roy's pics on wiring the Alps volume control. My only criticism of the PAS kit is Roy's documentation, or lack of. He was great to answer emails quickly and the pics are good. The build is pretty straightforward, however, I think some docs would go a long way to help build the kit and save a few emails. Maybe he has them now, don't know.

I did PIO1980's recommendation to reverse speaker line polarity and noticed a difference - thanks for that.
 
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