Croft RIAA Gain [Archive] - The Art of Sound Forum

gerlando

10-03-2021, 12:35

Hello there.

I recently bought a second hand Croft RIAA for matching it with a high output MC cartridge (Hana EH), since not long ago Glenn (Croft) told me that the RIAA has a slightly higher gain (44 db) than average standard MM phono stages (about 40/41 db), so it is a good match with the HOMC's.

While waiting for the Hana to arrive, yesterday I tried the RIAA with my AT-VM95ML (in as new condition, max 20 hours), which if I'm not mistaken has an output of 3.5 mv respect to the 2 mv of the Hana, but the output level seemed quite low, maybe even lower than the Graham Slee Gram Amp 2SE I had before.

Do you think it may depend on the type of tubes used (ECC83 Harma Cryo), or there may be other parameters affecting the gain?

I tried to write to Glenn but he still hasn't answered me.

The RIAA however sounds great and it's very musical.

Thank you.
Mauro

Firebottle

10-03-2021, 16:03

If you are using ECC88 valves that is the reason for the low gain.
AFAIK every Croft RIAA should use ECC83, which are much higher gain than the '88.

fiddlemaker

10-03-2021, 16:12

If you are using ECC88 valves that is the reason for the low gain.
AFAIK every Croft RIAA should use ECC83, which are much higher gain than the '88.

Yes, always ECC83. Maybe the previous owner misread the "8" as a "3". Or gain reduction for compatibility with the rest of his gear? Or just a tinkerer?
It'll sound much better with the correct valves.

gerlando

10-03-2021, 17:11

If you are using ECC88 valves that is the reason for the low gain.
AFAIK every Croft RIAA should use ECC83, which are much higher gain than the '88.

Sorry, my mistake, it's a pair of ECC83 HARMA Retro CRYO

https://i.imgur.com/oAkxXhh.jpg

Firebottle

10-03-2021, 18:06

The gain of the Croft is generally on the high side as most phono stages offer about 40dB.

However even with more gain than that the signal level will be way down when compared to a typical CD player or Dac output.

gerlando

10-03-2021, 18:19

Lawrence001

10-03-2021, 20:21

I know Glenn makes lower gain line preamps to order. Is it possible he also made lower gain RIAA stages?

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fiddlemaker

11-03-2021, 09:13

Hello there.

I tried to write to Glenn but he still hasn't answered me.

.
Mauro

I don't know if anyone else has found this, but there is something about Glenn's email address that triggers the spam filter on my email.
So might be worth looking in your spam/junk folder. I had to specifically add him to my contacts to stop this from happening. Just an idea.

gerlando

11-03-2021, 10:23

I don't know if anyone else has found this, but there is something about Glenn's email address that triggers the spam filter on my email.
So might be worth looking in your spam/junk folder. I had to specifically add him to my contacts to stop this from happening. Just an idea.

Than you for your suggestion.

Unfortunately no email in my spam folder.

gerlando

18-03-2021, 17:33

After receiving Glenn's reply, I understood the reasons for my Croft RIAA low gain:

"the gain of the RIAA depends on the input impedance of the amp it is driving - 100k ohms is the ideal value - anything lower will reduce the gain."

So if I understand correctly the RIAA would interface better with a tube amp.

My solid state integrated amplifier (Exposure 2010S) has a declared input impedance of> 14k ohms, so it's probably not the ideal match (my headphone amp has a declared input impedance of 47k ohms instead, and in fact connecting it directly at the RIAA the gain is significantly higher).

Wanting to keep my current integrated amp, do you think a solid state phono preamp (Trichord Dino, Lehmann BC, Dynavector P75, Graham Slee etc.) would pair better with my Exposure?

Thank you.
Mauro

hifi_dave

20-03-2021, 11:23

They might match but won't sound as good.

What is the problem with gain if you can turn the volume up a notch or two and get the volume you want ?

Firebottle

20-03-2021, 13:39

A valve buffer stage would solve the problem.

gerlando

20-03-2021, 14:50

They might match but won't sound as good.

What is the problem with gain if you can turn the volume up a notch or two and get the volume you want ?

Hi Dave,
unfortunately when paired with a Hana EH the output level is very low.

Maybe it would be better with a Ortofon 2M, Goldring 1042 or Rega Exact, all with an output of more than 5mV.

worrasf

20-03-2021, 16:52

You might consider using a Rothwell MC1-H (http://www.rothwellaudioproducts.co.uk/html/sut_for_homc.html) designed specifically for HOMC's prior to going into a MM RIAA. I use one with a Rothwell Simplex for my Mission 773 and Denon DL-160 HOMC's and am absolutely delighted with it. While both the Denon and Mission were sounding pretty good straight into the Simplex adding the MC1-H upped the gain but more importantly improved the dynamics.

The MC1-H/Simplex then feed a Croft 25RS line stage 7 monoblock system.

I had both the MC1-H and Simplex on a "try before you buy" from Andrew (Rothwell) so it was a risk-free deal.

Steve

Firebottle

20-03-2021, 17:59

Mauro and Stephen you are not understanding the problem.

The trouble is at the output with it being loaded with too low an impedance, nothing to do with the input or particular cartridge.

worrasf

20-03-2021, 18:17

Mauro and Stephen you are not understanding the problem.

The trouble is at the output with it being loaded with too low an impedance, nothing to do with the input or particular cartridge.Ah - my bad. Just read Mauro's post with Glenn's explanation. OK the MC1-H won't be the answer (it's still a nifty bit of kit though).
Presumably, if I were to get a Croft RIAA ( I was thinking the RIAA-R would be the sweet spot into my 25RS LS I would not have the same issue as Mauro?

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fiddlemaker

20-03-2021, 18:19

A valve buffer stage would solve the problem.

Something like this?
https://shenzhenaudio.com/collections/yaqin/products/yaqin-sd-cd3-6n8p-tube-signal-upgrade-hi-end-buffer-processor-for-cd-player

Edward

20-03-2021, 19:15

gerlando

20-03-2021, 20:07

Mauro,

I have one of Alan's (Firebottle) valve buffer stages (also with +14db gain) you are welcome to borrow to try things out if you wish. PM if interested.

Perhaps @Firebottle can first comment if this will help your situation?

Edward, thank you very much for your offer, but I don't want to put any other components in my system, at this point I prefer to try another solid state MM phono stage that is compatible with my amp and cartridge.

fiddlemaker

21-03-2021, 11:34

Edward, thank you very much for your offer, but I don't want to put any other components in my system, at this point I prefer to try another solid state MM phono stage that is compatible with my amp and cartridge.

Seems a shame.
Sounds like the sort of issue that Glenn could fix relatively easily with some minor internal mods to the RIAA? Although I'm not an expert, I hasten to add.

worrasf

21-03-2021, 12:08

Seems a shame.
Sounds like the sort of issue that Glenn could fix relatively easily with some minor internal mods to the RIAA? Although I'm not an expert, I hasten to add.He fitted a valve buffer circuit into my 25RSLS on the line out circuit so that I could use it to drive my Capella headphone amp without any loss of gain or quality

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gerlando

21-03-2021, 12:15

Seems a shame.
Sounds like the sort of issue that Glenn could fix relatively easily with some minor internal mods to the RIAA? Although I'm not an expert, I hasten to add.

It's strange, but Glenn didn't suggested me any modification on the RIAA.
But I can always ask him.

fiddlemaker

21-03-2021, 12:51

It's strange, but Glenn didn't suggested me any modification on the RIAA.
But I can always ask him.

My experience of communicating with Glenn about mods/upgrades is that he doesn't tend to lead the conversation. You often have to tell him what it is that you want him to do. That's what I've found, anyway.

worrasf

21-03-2021, 13:00

My experience of communicating with Glenn about mods/upgrades is that he doesn't tend to lead the conversation. You often have to tell him what it is that you want him to do. That's what I've found, anyway.I've found that to be the case as well. I think he's embarrassed about money and not wanting to appear greedy but if you ask the question "what's possible" the usual answer I get is "the sky's the limit"
LoL

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