Dave has done plenty of 350's,so his opinion carries weight and IHHO the Sprague orange drops sound as close to the original as he has found. Sprague makes 3 grades of orange drops,714P,715P, and the 716P series. The 716P has copper leads and is a better cap in my opinion. For the minimal upgrade in cost to me it's a no brainer.
The Sprague caps are favorites among most that upgrade Ampex electronics. My 350's were custom voiced to my ears and the parts were over 1,000+ $$. Can I tell the difference between the two, I think so but it's probably a case of is it worth the last 5 pct ? The biggest hurdle is finding somebody willing to upgrade these, few and far between.
If any resistors are needed Dave probably will have his thoughts and I would go with his recommendation. Later you might consider upgrading to a set of glass (GT) type tubes versus the military type metal cans. When you get that far email me and I can help you. As you know select tubes can make a difference.
Have Dave make you a set of IC's as the older Ampex cables use a different ground configuration. I think it's neet that you purchased a set of 350's as I consider them to be a great tube circuit preamp.
thanks for the great coaching. i did e-mail the suggestion to Dave on the 716P's, and he will go ahead and use the 715P and 716P polypropylene caps on the 350, and where they fit on the 351 where in some places he'll need to use the smaller polyester caps.
i very much appreciate your input and as i move along i'll definitely bounce things off you. and i'll mention the I.C.'s to Dave too. keep the suggestions coming as you think of them.
Mark, you are correct.....i do have a pair of 351 mic pre's. however; after i purchased those, i ran accross a 'virginal' complete 350-2 stereo deck in travel cases. so i brought the whole shebang over to Dave. he'll refurb the 350-2, and the 351 mic pre's.
i plan on using the 351 mic pre's as output electronics possibly with a transformer that would allow it to work with modern low impedence heads (maybe the ATR-102). or maybe i'll just sell them. we'll see.
Mike-another option that you can try when you get your 351s back is to take the XLR outputs from whatever tape deck you choose and run them into the line input of the 351s. This works perfect for me from my Otari MX-55 into my 350s. No hum, no noise, no overload, just great sound. Modern heads have way lower output than their older brethern.
yes. the 350-2 came complete with the 2 channels of electronics and the power supply. the small travel case in the pictures is just the power supply for the pre's.
if i had found this first i would not have purchased the 351 pre's.
Mike-another option that you can try when you get your 351s back is to take the XLR outputs from whatever tape deck you choose and run them into the line input of the 351s. This works perfect for me from my Otari MX-55 into my 350s. No hum, no noise, no overload, just great sound. Modern heads have way lower output than their older brethern.
Hi Mark:
The 351 has an Amphenol type connector for head input that is physically different from XLR type. It's not impossible but one would need to either modify or make a converter cable to use XLR head outputs. Although I have not try it myself, but I would have guessed the Ampex preamp would need a setup transformer or an additional gain stage to use modern heads with around 200mH inductance. But your MX-55 must have higher outputs than other heads.
Ki-I'm using the line input on my Ampex 350s which is an XLR connector. I don't think the output from my MX-55 is very high. If I plug the MX-55 output straight into my preamp, you have to really crank the volume control to get adequate gain. Plug it into the Ampex 350s and then into the preamp, it's a Goldilocks' moment. If I was trying to come straight off of the reproduce head and into the head input of the Ampex 350s, it would never work. There would need to be a step-up device in the signal path.
yes. the 350-2 came complete with the 2 channels of electronics and the power supply. the small travel case in the pictures is just the power supply for the pre's.
if i had found this first i would not have purchased the 351 pre's.
When Dave had my units he was using the orange drops and he did not see any reason to change to a different film cap. I always like to follow the techs advice, otherwise the water can muddy up quite a bit.
The coupling caps IIRC were 4uf values, I don't know what Dave uses as he might go with a electrolytic. FWIW I used a Auricap 4uf and they sound great. They were the right size and if you look at the pics of my 350's they are the yellow films,there are 4 in each unit. So I probably just muddied the water a little bit. Oh well,this is a audiophile forum isn't it.
Just thinking, and changing the 4uf coupling caps depends on what's in there to begin with.
Here's a old post I found when I first got my 350's. There are 2 4uf 150v and 2 4uf 450v caps, I used 200v and 400v rated Auricaps as replacements. I e-mailed Auricap and they told me the Auricaps were conservative in their ratings and the 400v would be fine in place of the 450v.
My Ampex MR70 transports will be picked up this Wednesday and packed and shipped next week. The transport is extremely quiet now compared to before the motors were rebuilt. I still have to have John at JRF Magnetics finish the headstack before I can have the complete deck up and running. I'll post some photos when I get everything in the console.
Update:
I talked to John French and should have the head stack done soon. I have the original adjustable head stack, adj. playback head and also the erase head. The record head John will provide. The transports will be shipped tomorrow so I will have them late next week. I'm getting excited about having this MR70 done.
Here are images of my MR70 running thru it's paces
With the real,idler and capstan motors rebuilt along with a new capstan flywheel rubber and pinch roller the deck is smooth and quiet.
The relays,switches,brake linings, power supply among many other things were cleaned, rebuilt or replaced .
I added the 1st video Charlie did for me back in June '11, I think you can tell that the reel motors are much quieter and the LH escutcheon has been replaced.
