A few questions

[GLF]

Hi all, this is my first post here and I have a few questions and would like a few opinions.

Here is my system
Sony C333ES SACD player
Bottlehead Foreplay
Dynaco ST-70 (only new thing in there are the bias caps)
Magnepan MMG
Belden 89259 interconnects

I am in a small (10'x12') room.

I am wonder what you would recommend I do with my foreplay and dynaco. I have been looking at the various input boards for the ST-70 and also the idea of getting another power transformer and turning them into monoblocks. I would like to get rid of the selenium rectifier asap, I guess I need a UF4007 diode, does anyone know where I could pick one up?

As far as the foreplay goes, would it be worth it to mod the pre so it can use a different tube from the 12AU7? Maybe beef up the power supply a bit?

Any other ideas for any of it?

Thanks

Andrew

[SY]

You could probably use something with a bit more guts to run the Maggies- an ST-70 is pretty marginal, even in a small room.

If you want to rebuild the 70, you could do a lot worse than the Curcio circuits- very nice regulator, quite reliable, and a good topology for the input stage.

[GLF]

The dynaco does a good job with the maggies. I have heard them with less, and with a lot more. So far the ST-70 has done just as well as a 100watt bryston and a 230watt NAD in this room. The dynaco has a tad more bass then the NAD had.

Do you think it would be worth it to get another transformer and do the monoblocks or just do one of the ST-70 mods?

Andrew

[fdegrove]

Hi,

Do you think it would be worth it to get another transformer and do the monoblocks or just do one of the ST-70 mods?

My vote would go to the Curcio mod.

Cheers,

[GLF]

I have a chance to get another PA-060 power transformer from a friend for pretty cheap and if I buy the transformer he will help me machine some chassis plates out for a pair of mono blocks. I am wondering if there are any amp designs that would use the two power and two output transformers from the ST-70. Or am I best off just going for the Curcio upgrade or holding off for a while and doing the full mod.

Thanks

Andrew

[fdegrove]

Hi,

Since can get it cheap, why not?

It is a pretty universal xfromer so, wheter you use it for monoblocks or for something else...

As for the the JC mod, I think it is best to get acquainted with it first and see if you like the results enough, later on you can still go for the monoblock version of the amps IMO.

Cheers,

[pedroskova]

Originally posted by GLF


As far as the foreplay goes, would it be worth it to mod the pre so it can use a different tube from the 12AU7? Maybe beef up the power supply a bit?

I'd try the "Anticipation" ccs first, if you haven't already done it. Most tube replacements require changing the tranny - mostly due to heater requirements. If you just add a separate 6V tranny for the heaters, the 6SN7 is a literal drop in for this circuit.

[GLF]

I have done the anticipation mod (thanks dale). How much would a transformer with a 6v line run? I am thinking about rebuilding the foreplay in a different chassis once I finish the dynaco.

Speaking of the dynaco. Will power supply mods help it better drive my MMGs? Right now it has no trouble with the speakers, but the room I am in is only 10 feet deep. Will the modded amp do good once I move to a slightly larger room? If I wire it in triode will that also have an effect? I know triode knocks the amp down to around 18 watts.

I am sure that the mods to this amp make it sound really good, but what I am wondering is that if I put close to $500 US into the amp with the curcio mods and possibly wire it in triode, will it be a good amp for my speakers. I tend to have it on for 6-12 hours a day, not always at really loud levels, but at least at back ground levels. Considering I am a college student, and I would like this to be my last amp purchase for a while, at least till mid to late summer, should i go with the curcio mods, or look at design that would use the 4 transformers and EL-34s I have, or maybe one of the ASKA or Alpha kits?

Thanks again

Andrew

[pedroskova]

A 2 amp 6V transformer only costs a few bucks from discounters like Alltronics. Add a 16v 10000uf cap and a 1R 5W resistor, and you have dc filaments on the cheap...for the 6sn7...or you could get a hammond 260 or 360 series xfrmr for 35-45 bucks and be free to upgrade this circuit and try any number of other circuits in the future. They don't wear out.

for different tubes in the foreplay see below:

http://www.AudioAsylum.com/forums/bo...ges/21342.html